Abstract:
The invention provides for methods of treating, abating and reducing the risk for intestinal injury by administering a combination heparin binding epidermal growth factor (HB-EGF) and stem cells, such as mesenchymal stem cells or intestinal stem cells, in an amount effective to reduce the onset or severity of intestinal injury. The invention also provides for methods of promoting engraftment of stem cells, such as mesenchymal stem cells or intestinal stem cells, within the intestine of a patient suffering from intestinal injury.

Description:
FIELD OF INVENTION 
       [0001]    The invention provides for methods of treating, abating and reducing the risk for intestinal injury by administering a combination of heparin binding epidermal growth factor (HB-EGF) and stem cells, such as mesenchymal stem cells or intestinal stem cells, in an amount effective to reduce the onset or severity of intestinal injury. The invention also provides for methods of promoting engraftment of stem cells within the intestine of a patient suffering from an intestinal injury. 
       BACKGROUND 
       [0002]    Heparin-binding epidermal growth factor (HB-EGF) was first identified in the conditioned medium of cultured human macrophages (Besner et al.,  Growth Factors,  7: 289-296 (1992), and later found to be a member of the epidermal growth factor (EGF) family of growth factors (Higashiyama et al.,  Science.  251:936-9, 1991). It is synthesized as a transmembrane, biologically active precursor protein (proHB-EGF) composed of 208 amino acids, which is enzymatically cleaved by matrix metalloproteinases (MMPs) to yield a 14-20 kDa soluble growth factor (sHB-EGF). Pro-HB-EGF can form complexes with other membrane proteins including CD9 and integrin α3β1; these binding interactions function to enhance the biological activity of pro-HB-EGF. ProHB-EGF is a juxtacrine factor that can regulate the function of adjacent cells through its engagement of cell surface receptor molecules. 
         [0003]    sHB-EGF is a potent mitogenic and chemoattractant protein for many types of cells. Similar to all members of the EGF family, HB-EGF binds to the “classic” or prototypic epidermal growth factor receptor (EGFR; ErbB-1). However, while the mitogenic function of sHB-EGF is mediated through activation of ErbB-1, its migration-inducing function involves the activation of ErbB-4 and the more recently described N-arginine dibasic convertase (NRDc, Nardilysin). This is in distinction to other EGF family members such as EGF itself, transforming growth factor (TGF)-α and amphiregulin (AR), which exert their signal-transducing effects via interaction with ErbB-1 only. In fact, the NRDc receptor is totally HB-EGF-specific. In addition, unlike most members of the EGF family, which are non-heparin binding, sHB-EGF is able to bind to cell-surface heparin-like molecules (heparan sulfate proteoglycans; HSPG), which act as low affinity, high capacity receptors for HB-EGF. The differing affinities of EGF family members for the different EGFR subtypes and for HSPG may confer different functional capabilities to these molecules in vivo. The combined interactions of HB-EGF with HSPG and ErbB-1/ErbB-4/NRDc may confer a functional advantage to this growth factor. Importantly, endogenous HB-EGF is protective in various pathologic conditions and plays a pivotal role in mediating the earliest cellular responses to proliferative stimuli and cellular injury. 
         [0004]    Although the HB-EGF gene is widely expressed, the basal level of its mRNA is relatively low in normal cells. Expression of HB-EGF is significantly increased in response to tissue damage, hypoxia and oxidative stress, and also during wound healing and regeneration. This pattern of expression is consistent with a pivotal role for HB-EGF in ischemia/reperfusion (I/R) injury, regeneration, and repair processes. 
         [0005]    Intestinal barrier function represents a critical initial defense against noxious intraluminal substances. Although the intestine is not as essential as the vital organs in the immediate preservation of life, intestinal I/R is as lethal as extensive heart and brain ischemia. The gut has a higher critical oxygen requirement compared to the whole body and other vital organs. Accordingly, the intestinal mucosa is extremely susceptible to I/R and even short periods of ischemia can initiate local and remote tissue damage as well as systemic hemodynamic disturbances. 
         [0006]    Reactive oxygen species (ROS), pro-inflammatory cytokines, leukocyte adhesion, and complement activation can all mediate intestinal I/R. Loss of immune and barrier functions of the gut secondary to I/R leads to significant detrimental effects on other organs such as lungs, liver, kidneys and heart, and may result in multiple organ dysfunction syndrome (MODS) and death. Exploring the potential of new therapeutic strategies to enhance the regenerative capacity and/or increase the resistance of the intestine to I/R injury would improve outcome in these patients. 
         [0007]    The gut is highly susceptible to hypoperfusion injury due to its higher critical oxygen requirement compared to the whole body, and due to the mucosal countercurrent microcirculation. Not surprisingly, patients subjected to hypoperfusion states such as hemorrhagic shock and resuscitation (HS/R), trauma, and major surgery often develop intestinal ischemia as documented by both experimental and clinical studies. 
         [0008]    Following the hypoperfusion effects of the shock stage, traditional methods of resuscitation often fail to adequately restore mesenteric perfusion despite stabilization of heart rate, blood pressure, and improved perfusion in some organs such as the heart and brain. To the contrary, resuscitation is characterized by progressive deterioration of mesenteric blood flow. Progressive intestinal hypoperfusion after HS/R contributes to loss of the gut mucosal barrier and to hypoxia-induced intestinal inflammation, both of which are critical to the initiation of MODS after HS/R. Accordingly, factors that protect the intestine from injury and promote early intestinal healing by restitution could significantly improve outcome after HS/R. 
         [0009]    HB-EGF has been demonstrated to be essential for intestinal healing by restitution in intestinal epithelial cells (IEC) in vitro and in rats subjected to superior mesenteric artery occlusion (SMAO) in vivo (El-Assal &amp; Besner Gastroenterology 129(2): 609-625. 2005). These HB-EGF-induced effects are mediated via activation of various molecular mechanisms including MEK/ERK and PI3K/Akt signaling pathways. 
         [0010]    Administration of EGF to prevent tissue damage after an ischemic event in the brains of gerbils has been reported in U.S. Pat. No. 5,057,494 issued Oct. 15, 1991 to Sheffield. The patent projects that EGF “analogs” having greater than 50% homology to EGF may also be useful in preventing tissue damage and that treatment of damage in myocardial tissue, renal tissue, spleen tissue, intestinal tissue, and lung tissue with EGF or EGF analogs may be indicated. However, the patent includes no experimental data supporting such projections. 
         [0011]    EGF family members are of interest as intestinal protective agents due to their roles in gut maturation and function. Infants with NEC have decreased levels of salivary EGF, as do very premature infants (Shin et al.,  J Pediatr Surg  35:173-176, 2000; Warner et al.,  J Pediatr  150:358-6, 2007). Studies have demonstrated the importance of EGF in preserving gut barrier function, increasing intestinal enzyme activity, and improving nutrient transport (Warner et al.,  Semin Pediatr Surg  14:175-80, 2005). EGF receptor (EGFR) knockout mice develop epithelial cell abnormalities and hemorrhagic necrosis of the intestine similar to neonatal necrotizing enterocolitis (NEC), suggesting that lack of EGFR stimulation may play a role in the development of NEC (Miettinen et al.,  Nature  376:337-41, 1995). Dvorak et al. have shown that EGF supplementation reduces the incidence of experimental NEC in rats, in part by reducing apoptosis, barrier failure, and hepatic dysfunction ( Am J Physiol Gastrointest Liver Physiol  282:G156-G164, 2002). Vinter-Jensen et al., investigated the effect of subcutaneously administered EGF (150 μg/kg/12 hours) in rats, for 1, 2 and 4 weeks, and found that EGF induced growth of small intestinal mucosa and muscularis in a time-dependent manner ( Regul Pept  61:135-142, 1996). Several case reports of clinical administration of EGF also exist. Sigalet et al. administered EGF (100 μg/kg/day) mixed with enteral feeds for 6 weeks to pediatric patients with short bowel syndrome (SBS), and reported improved nutrient absorption and increased tolerance to enteral feeds with no adverse effects ( J Pediatr Surg  40:763-8, 2005). Sullivan et al., in a prospective, double-blind, randomized controlled study that included 8 neonates with NEC, compared the effects of a 6-day continuous intravenous infusion of EGF (100 ng/kg/hour) to placebo, and found a positive trophic effect of EGF on the intestinal mucosa ( Ped Surg  42:462-469, 2007). Palomino et al. examined the efficacy of EGF in the treatment of duodenal ulcers in a multicenter, randomized, double blind human clinical trial in adults. Oral human recombinant EGF (50 mg/ml every 8 h for 6 weeks) was effective in the treatment of duodenal ulcers with no side effects noted ( Scand J Gastroenterol  35:1016-22, 2000). 
         [0012]    Enteral administration of  E. coli -derived HB-EGF has been shown to decrease the incidence and severity of intestinal injury in a neonatal rat model of NEC, with the greatest protective effects found at doses of 600 or 800 μg/kg/dose (Feng et al.,  Semin Pediatr Surg  14:167-74, 2005). In addition, HB-EGF is known to protect the intestines from injury after intestinal ischemia/reperfusion injury (El-Assal et al., Semin Pediatr Surg 13:2-10, 2004) or hemorrhagic shock and resuscitation (El-Assal et al., Surgery 142:234-42, 2007). 
         [0013]    Mesenchymal stem cells (MSC) have the ability to differentiate into different cell lineages and can stimulate wound healing via paracrine signaling pathways. Preclinical studies have shown that MSC can regulate the host immune response, thus avoiding recognition and subsequent rejection by recipients. The robust, self-renewing, multilineage differentiation potential of MSC makes these cells very desirable candidates for possible clinical cellular therapy. Baksh et al.,  J Cell Mol Med  2004; 8(3):301-16. Ongoing investigations are exploring ways to optimize MSC efficacy prior to therapeutic delivery, including preconditioning by exposure to hypoxia, Hu et al.,  J Thorac Cardiovasc Surg  2008; 135(4):799-808, growth factors, Hahn et al.,  J Am Coll Cardiol  2008; 51(9):933-43, and various cytokines. Gui et al.,  Mol Cell Biochem  2007; 305(1-2):171-8, Pasha et al.,  Cardiovasc Res  2008; 77(1):134-42, Liu et al.,  Acta Pharmacol Sin  2008; 29(7):815-22. 
         [0014]    Local stem cell (SC) delivery may result in increased risks and side effects including bleeding and tissue injury when administered by direct intralesional injection, and occlusion and embolization when administered intra-arterially to target organs Dimmeler et al.,  Arterioscler Thromb Vasc Biol.  2008; 28:208-216, Ott et al.,  Basic Res Cardiol.  2005; 100:504-517, Sherman et al.,  Nat Clin Pract Cardiovasc Med.  2006; 3 Suppl 1:S57-64. Intravenous (IV) infusion has been used for systemic SC delivery in preclinical studies Lee et al.,  Cell Stem Cell.  2009; 5:54-63, Abdel-Mageed et al.,  Blood.  2009; 113:1201-1203, and in clinical trials Lazarus et al.,  Bone Marrow Transplant.  1995; 16:557-564, Horwitz et al., Nat. Med. 1999; 5:309-313, Le Blanc et al.,  Lancet.  2008; 371:1579-1586, Wu et al.,  Transplantation.  2011; 91:1412-1416, in the past two decades. However, it has been noted that a large fraction of systemically infused MSC become trapped in the lung due to their large size Schrepfer et al.,  Transplant Proc.  2007; 39:573-576. Thus, pulmonary passage is a major obstacle for IV stem cell delivery, which is termed the “pulmonary first-pass effect” Fischer et al.,  Stem Cells Dev.  2009; 18:683-692. This effect not only causes poor efficiency of MSC delivery and decreased specific homing of the cells, but it also threatens the life of experimental animals Ramot et al.,  Nanotoxicology.  2010; 4:98-105. Pulmonary sequestration by MSC intravascular infusion causes death in small adult animals, with the mortality rate ranging from 25% to 40%. 
         [0015]    The prevention and treatment of ischemic damage in the clinical setting continues to be a challenge in medicine. There exists a need in the art for models for testing the effects of potential modulators of ischemic events and for methods of preventing and/or treating ischemic damage, particularly ischemic damage to the intestines. Because of its ability to enhance the regenerative capacity and/or increase the resistance of the mucosa to injury, HB-EGF in combination with administration of somatic stem cells may represent a promising therapeutic strategy for intestinal diseases, including necrotizing enterocolitis hemorrhagic shock, and ischemia-related injuries and inflammatory conditions. 
       SUMMARY OF INVENTION 
       [0016]    Factors that protect the intestine from injury and promote early intestinal healing by restitution may significantly improve the clinical outcome of human subjects suffering many forms of intestinal injury. HB-EGF has previously been demonstrated to have potent mitogenic activity for a variety of cell types, including smooth muscle cells, epithelial cells, fibroblasts, keratinocytes and renal tubular cells, and is a known chemotactic agent for various cell types. Furthermore, mesenchymal stem cells are an attractive target for regenerative medicine. Their properties in cell culture and their in vitro behavior are becoming increasingly characterized. 
         [0017]    The invention provides for methods of treating intestinal injury by administering HB-EGF and somatic stems cells, such as mesenchymal stem cells (MSC) or intestinal stem cells (ISC), each in an amount effective to reduce the serverity of the intestinal injury. As shown in Example 11, treatment with HB-EGF alone or MSC alone reduced the severity of NEC. However, HB-EGF and MSC administered together reduced the severity of NEC more significantly compared to either HB-EGF or MSC alone. The experiments described herein demonstrate that HB-EGF protects enterocytes, goblet cells, neuroendocrine cells and intestinal progenitor and stem cells from NEC. In addition, HB-EGF protects intestinal stem cells from hypoxic stress in vitro. HB-EGF administration in conjunction with MSC transplantation leads to improved efficacy compared to either therapy alone in animal models of NEC (see Example 11). 
         [0018]    The experiments described herein also demonstrate that HB-EGF promotes proliferation of amniotic fluid derived MSC (AF-MSC) and bone marrow derived MSC (BM-MSC) under normoxic and anoxic conditions, induces MSC chemotaxis, and protects MSC from anoxia-induced apoptosis. The observation that HB-EGF induces a more robust proliferative response as well as increased resistance to anoxic stress in AF-MSC compared with BM-MSC may explain why AF-MSC appear to be more effective in protection of the intestines from injury in vivo when administered in conjunction with HB-EGF. Therefore, the invention provides for methods of using HB-EGF as a potential method to improve the efficacy of MSC transplantation for therapeutic use. 
         [0019]    HB-EGF is known to be present in human amniotic fluid and breast milk, ensuring continuous exposure of the fetal and newborn intestine to endogenous levels of the growth factor (Michalsky et al.,  J Pediatr Surg  37:1-6, 2006). Thus, the developing fetus and the breastfed newborn are continually exposed to HB-EGF naturally both before and after birth. Supplementation of enteral feeds with a biologically active substance such as HB-EGF, to which the fetus and newborn are naturally exposed, may represent a logical and safe way to reduce intestinal injury resulting in NEC. HB-EGF supplementation of feeds in very low birth weight patients (&lt;1500 g) who are most at risk for developing NEC is contemplated to facilitate maturation, enhance regenerative capacity, and increase the resistance of the intestinal mucosa to injury. 
         [0020]    Intragastric administration of HB-EGF to rats is known to lead to delivery of the growth factor to the entire GI tract including the colon within 8 hours. HB-EGF is excreted in the bile and urine after intragastric or intravenous administration (Feng et al.,  Peptides.  27(6):1589-96, 2006). In addition, intragastric administration of HB-EGF to neonatal rats and minipigs has no systemic absorption of the growth factor (unpublished data). These findings collectively support the clinical feasibility and safety of enteral administration of HB-EGF in protection of the intestines from injury. 
         [0021]    The invention provides for methods of treating an intestinal injury comprising administering a heparin binding epidermal growth factor (HB-EGF) product or a fragment thereof and stem cells, including somatic stem cells or embryonic stem cells, each in an amount effective to reduce the severity of the intestinal injury. 
         [0022]    The invention also provides for methods of reducing damage to intestinal tissue in a patient suffering from intestinal injury comprising administering a heparin binding epidermal growth factor (HB-EGF) product or a fragment thereof and stem cells each in an amount effective to protect the intestinal tissue in the patient, including administering somatic stem cells or embryonic stem cells. 
         [0023]    In another embodiment, the invention provides for methods of inducing somatic stem cell proliferation comprising administering a heparin binding epidermal growth factor (HB-EGF) product or a fragment thereof in an amount effective to induce somatic stem cell proliferation. This method includes inducing somatic stem cell proliferation, such as MSC and ISC, in vivo, in vitro and in culture. 
         [0024]    In another embodiment, the invention provides for methods of inducing embryonic stem cell proliferation comprising administering a heparin binding growth factor (HB-EGF) or a fragment thereof in an amount effective to induce embryonic stem cell proliferation. This method includes inducing embryonic stem cell proliferation, in vivo, in vitro and in culture. 
         [0025]    The invention also provides for methods of protecting somatic stem cells in a patient suffering from intestinal injury comprising administering a heparin binding epidermal growth factor (HB-EGF) product or a fragment thereof in an amount effective to protect the intestinal tissue in the patient. 
         [0026]    In another embodiment, the invention provides for methods of promoting engraftment of somatic stem cells in the intestine of a patient suffering from an intestinal injury comprising administering a heparin binding epidermal growth factor (HB-EGF) product or a fragment thereof in an amount effective to promote engraftment in the patient. 
         [0027]    In another embodiment, the invention provides for methods of promoting engraftment of embryonic stem cells in the intestine of a patient suffering from an intestinal injury comprising administering a heparin binding epidermal growth factor (HB-EGF) product or a fragment thereof in an amount effective to promote engraftment in the patient. 
         [0028]    In any of the foregoing methods of the invention, the intestinal injury may be caused by necrotizing enterocolitis, hemorrhagic shock, resuscitation, ischemia/reperfusion injury, intestinal inflammatory conditions or intestinal infections. In addition, in any of the foregoing methods of the invention, the patient or subject may be suffering from Hirschprung&#39;s Disease, intestinal dysmotility disorders, intestinal pseudo-obstruction (Ogilvie&#39;s Syndrome), inflammatory bowel disease, radiation enteritis, irritable bowel syndrome or chronic constipation, Chrone&#39;s Disease, bowel cancer or colorectal cancers. In addition, in any of the foregoing methods of the invention, the patient or subject many be an infant, adolescent or an adult. 
         [0029]    In another embodiment, the invention provides for methods of treating an infant suffering from necrotizing enterocolitis (NEC), comprising administering a heparin binding epidermal growth factor (HB-EGF) product and stem cells each in an amount effective to reduce the severity of NEC, including administering somatic stem cells or embryonic stem cells. 
         [0030]    The invention also provides for method of treating an infant to abate necrotizing enterocolitis (NEC), comprising administering a heparin binding epidermal growth factor (HB-EGF) product and stem cells each in an amount effective to reduce the severity of NEC, including administering somatic stem cells or embryonic stem cells. 
         [0031]    The invention provides for methods of reducing the risk of developing necrotizing enterocolitis (NEC) in an infant, comprising administering a heparin binding epidermal growth factor (HB-EGF) product and stem cells in an amount effective to reduce the onset of NEC, including administering somatic stem cells or embryonic stem cells. 
         [0032]    In any of the methods of the invention, the somatic stem cells are mesenchymal stem cells or intestinal stem cells, and the somatic stem cells are administered intravenously, intra-arterially or intraperitoneally. Further, in any of the foregoing methods of the invention, the HB-EGF product is administered intravenously, intraluminally, intragastrically intraperitoneally or intra-arterially. For any of the methods of the invention, the HB-EGF product and/or the somatic stem cells are administered immediately following the intestinal injury or within 1-5 hours following the intestinal injury. 
         [0033]    The invention also provides for carrying out any of the methods of the invention using embryonic stem cells that are administered intravenously, intra-arterially or intraperitoneally. 
         [0034]    In any of the methods of the invention, the HB-EGF product and the somatic stem cells, such as MSC or ISC, are administered concurrently. For concurrent administration, the HB-EGF product and the somatic stem cells can be administered as separate compositions at the same time or within a short time period. Alternatively, the somatic stem cell can be transformed to express a HB-EGF product, and thereby administration of the HB-EGF product expressing somatic stem cells results in concurrent administration of the HB-EGF product and the somatic stem cells. 
         [0035]    In another embodiment, the HB-EGF product and the somatic stem cells, such as MSC or ISC are administered consecutively. For example, the HB-EGF product is administered immediately before the somatic stem cells, or the somatic stem cells are administered immediately before the HB-EGF product. Alternatively, the methods of the invention are carried out wherein somatic stem cells are administered within 1-5 hours after administering the HB-EGF product or the methods of the invention are carried out wherein HB-EGF product is administered within 1-5 hours after administering the somatic stem cells. 
         [0036]    In any of the methods of the invention, the HB-EGF product are administered prior to administration of the somatic stem cells, such as MSC or ISC. In one embodiment, the HB-EGF product can be administered daily for several days, prior to the administration of the somatic stem cells. For example, the HB-EGF product can be administered one day prior to the administration of the somatic stem cells, or the HB-EGF product can be administered two days prior to the administration of the somatic stem cells, or the HB-EGF product can be administered three days prior to the administration of the somatic stem cells, the HB-EGF product can be administered four days prior to the administration of the somatic stem cells, the HB-EGF product can be administered five days prior to the administration of the somatic stem cells, the HB-EGF product can be administered six days prior to the administration of the somatic stem cells, or the HB-EGF product can be administered seven days prior to the administration of the somatic stem cells. In addition, the HB-EGF product can be administered 1-2 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 1-3 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 1-4 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 1-5 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 1-6 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 1-7 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 2-3 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 2-4 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 3-5 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 3-6 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 3-7 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 4-7 days prior to the administration of the somatic stem cells, the HB-EGF product can be administered 5-7 days prior to the administration of the somatic stem cells, or the HB-EGF product can be administered 6-7 days prior to the administration of the somatic stem cells. 
         [0037]    The onset of symptoms of NEC refers to the occurrence or presence of one or more of the following symptoms: temperature instability, lethargy, apnea, bradycardia, poor feeding, increased pregavage residuals, emesis (may be bilious or test positive for occult blood), abdominal distention (mild to marked), occult blood in stool (no fissure), gastrointestinal bleeding (mild bleeding to marked hemorrhaging), significant intestinal distention with ileus, edema in the bowel wall or peritoneal fluid, unchanging or persistent “rigid” bowel loops, pneumatosis intestinalls, portal venous gas, deterioration of vital signs, evidence of septic shock and pneumoperitoneum. 
         [0038]    In one embodiment, the invention contemplates administering a HB-EGF product and somatic stem cells, such as MSC or ISC, to a premature infant. The term “premature infant” (also known as a “premature baby” or a “preemie”) refers to babies born having less than 36 weeks gestation. In another embodiment, the invention provides for methods of administering an EGF receptor agonist to an infant having a low birth weight or a very low birth weight. A low birth weight is a weight less than 2500 g (5.5 lbs.). A very low birth weight is a weight less than 1500 g (about 3.3 lbs.). The invention also provides for methods of administering a HB-EGF product and somatic stem cells, such as MSC or ISC, to infants having intrauterine growth retardation, fetal alcohol syndrome, drug dependency, prenatal asphyxia, shock, sepsis, or congenital heart disease. 
         [0039]    In addition to a HB-EGF product, the methods of the invention may utilize any EGF receptor agonist. An EGF receptor agonist refers to a molecule or compound that activates the EGF receptor or induces the EGF receptor to dimerize, autophosphorylate and initiate cellular signaling. For example, any of the methods of the invention may be carried out with an EGF receptor agonist such as an EGF product or a HB-EGF product. 
         [0040]    The methods of the invention are carried out with a dose of each of a HB-EGF product and somatic stem cells, such as MSC or ISC, that is effective to reduce the onset or severity of intestinal injury or to protect or rejuvenate the intestinal tissue in patient. Exemplary effective doses are 100 μg/kg dose, 105 μg/kg dose, 110 μg/kg dose, 115 μg/kg dose, 120 μg/kg dose, 125 μg/kg dose, 130 μg/kg dose, 135 μg/kg dose, 140 μg/kg dose, 200 μg/kg dose, 250 μg/kg dose, 300 μg/kg dose, 400 μg/kg dose, 500 μg/kg dose, 550 μg/kg dose, 570 μg/kg dose, 600 μg/kg dose, 800 μg/kg dose and 1000 μg/kg dose. Exemplary dosage ranges of EGF receptor agonist, such as HB-EGF, that is effective to reduce the onset or severity of intestinal injury or to protect or rejuvenate the intestinal tissue in patients are 100-140 μg/kg, 100-110 μg/kg dose, 110-120 μg/kg dose, 120-130 μg/kg dose, 120-140 μg/kg dose and 130-140 μg/kg dose. 
         [0041]    For all the methods of the invention, the HB-EGF product is a polypeptide having the amino acid sequence of SEQ ID NO: 2 or a fragment thereof that competes with HB-EGF for binding to the ErbB-1 receptor and has ErbB-1 agonist activity. A preferred HB-EGF product is a fragment of HB-EGF that comprises amino acids of 74-148 of SEQ ID NO: 2 (human HB-EGF(74-148). In addition, the HB-EGF product includes fragments of HB-EGF that induce epithelial cell or somatic stem cell, such as MSC or ISC, proliferation, fragments of HB-EGF that induce epithelial cell or somatic stem cell, such as MSC or ISC, migration, fragments of HB-EGF that promote epithelial cell or somatic stem cell, such as MSC or ISC, viability, and a fragment of HB-EGF that protects epithelial cells or somatic stem cells, such as MSC or ISC form apoptosis or other types of cellular injury. 
         [0042]    In preferred embodiments, the HB-EGF product and somatic stem cells, such as MSC or ISC, are administered in any of the methods of the invention immediately after intestinal injury, or shortly after intestinal injury such as within about 1, about 2, about 3, about 4 or about 5 hours after intestinal injury. However, the invention provides for methods of administering a HB-EGF product and somatic stem cells, such as MSC or ISC, at any time during or after intestinal injury, such as later than about 5 hours after injury. For example, the invention contemplates administering a HB-EGF product and somatic stem cells, such as MSC or ISC, to subjects seeking treatment several or many hours after injury or after hemorrhagic shock (HS) or NEC has developed, or in cases where treatment is delayed for some reason. 
         [0043]    When the intestinal injury is caused by HS or HS/R, the invention provides method of administering a HB-EGF product and somatic stem cells, such as MSC or ISC, immediately after HS or HS/R or shortly after HS or HS/R such as within about 1, about 2, about 3, about 4 or about 5 hours after resuscitation. However, the invention provides for methods of administering a HB-EGF product and somatic stem cells, such as MSC or ISC, at any time during or after HS or HS/R has developed, such as later than about 5 hours after injury or later than about 5 hours after HS or HS/R has developed. For example, the invention contemplates administering a HB-EGF product and somatic stem cells, such as MSC or ISC, to subjects seeking treatment several or many hours after injury or after HS has developed, or in cases where treatment is delayed for some reason. In addition, it is preferred that the HB-EGF product and somatic stem cells, such as MSC or ISC, be administered before ischemia, hypoxia or necrotizing enterocolitis takes effect. 
         [0044]    When the intestinal injury is NEC, the methods of the invention include administering a HB-EGF product and somatic stem cells, such as MSC or ISC, immediately after birth or shortly after birth. For example, the dose may be administered within about the first hour following birth, within about 2 hours following birth, within about 3 hours following birth, within about 4 hours following birth, within about 5 hours following birth, within about 6 hours following birth, within about 7 hours following birth, within about 8 hours following birth, within about 9 hours following birth, within about 10 hours following birth, within about 11 hours following birth, within about 12 hours after birth, within about 13 hours after birth, within about 14 hours after birth, within about 15 hours after birth, within about 16 hours after birth, within about 17 hours after birth, within about 18 hours after birth, within about 19 hours after birth, within about 20 hours after birth, within about 21 hours after birth, within about 22 hours after birth, within about 23 hours after birth, within about 24 hours after birth, within about 36 hours after birth, within about 48 hours after birth or within about 72 hours after birth. 
         [0045]    The invention contemplates administering a HB-EGF product and somatic stem cells, such as MSC or ISC, to an infant suffering or at risk of developing NEC. In one embodiment, a HB-EGF product and somatic stem cells, such as MSC or ISC, are administered within about the first 12-72 hours after birth. For example, the doses a HB-EGF product and somatic stem cells, such as MSC or ISC, are administered about 12 hours after birth, about 24 hours after birth, about 36 hours after birth, about 48 hours after birth or about 72 hours after birth. In further embodiments, the doses are administered between hours 1-4 following birth or between hours 2-5 following birth or between hours 3-6 following birth or between hours 4-7 following birth or between hours 5-8 following birth or between hours 6-9 following birth or between hours 7-10 following birth or between hours 8-11 following birth, between hours 9-12 following birth, between hours 10-13 following birth, between hours 11-14 following birth, between hours 12-15 following birth, between hours 13-16 following birth, between hours 14-17 following birth, between hours 15-18 following birth, between hours 16-19 following birth, between hours 17-20 following birth, between hours 18-21 following birth, between hours 19-22 following birth, between hours 20-23 following birth, between hours 21-24 following birth, between hours 12-48 following birth, between hours 24-36 following birth, between hours 36-48 following birth and between hours 48-72 after birth. 
         [0046]    In another embodiment, a HB-EGF product and somatic stem cells, such as MSC or ISC, are administered within 24 hours following the onset of at least one symptom of NEC, such as administering a HB-EGF product and somatic stem cells, such as MSC or ISC, within about the first 12-72 hours after onset of at least one symptom of NEC. For example, the doses of a HB-EGF product and somatic stem cells, such as MSC or ISC, are administered about 12 hours following the occurrence or presence of a symptom of NEC, about 24 hours following the occurrence or presence of a symptom of NEC, about 36 hours following the occurrence or presence of a symptom of NEC, about 48 hours following the occurrence or presence of a symptom of NEC or about 72 hours following the occurrence or presence of a symptom of NEC. In further embodiments, the doses are administered between hours 1-4 following the occurrence or presence of a symptom of NEC or between hours 2-5 following the occurrence or presence of a symptom of NEC or between hours 3-6 following the occurrence or presence of a symptom of NEC or between hours 4-7 following the occurrence or presence of a symptom of NEC or between hours 5-8 following the occurrence or presence of a symptom of NEC or between hours 6-9 following the occurrence or presence of a symptom of NEC or between hours 7-10 following the occurrence or presence of a symptom of NEC or between hours 8-11 following the occurrence or presence of a symptom of NEC, between hours 9-12 following the occurrence or presence of a symptom of NEC, between hours 10-13 following the occurrence or presence of a symptom of NEC, between hours 11-14 following the occurrence or presence of a symptom of NEC, between hours 12-15 following the occurrence or presence of a symptom of NEC, between hours 13-16 following the occurrence or presence of a symptom of NEC, between hours 14-17 following the occurrence or presence of a symptom of NEC, between hours 15-18 following the occurrence or presence of a symptom of NEC, between hours 16-19 following the occurrence or presence of a symptom of NEC, between hours 17-20 following the occurrence or presence of a symptom of NEC, between hours 19-22 following the occurrence or presence of a symptom of NEC, between hours 20-23 following the occurrence or presence of a symptom of NEC, between hours 21-24 following the occurrence or presence of a symptom of NEC, between hours 12-48 following the occurrence or presence of a symptom of NEC, between hours 24-36 following after the occurrence or presence of a symptom of NEC, between hours 36-48 following the occurrence or presence of a symptom of NEC or between hours 48-72 following the occurrence or presence of a symptom of NEC. 
         [0047]    The term “within 24 hours after birth” refers to administering at least a first unit dose of a HB-EGF product and/or unit dose of somatic stem cells, such as MSC or ISC, within about 24 hours following birth, and the first dose may be succeeded by subsequent dosing outside the initial 24 hour dosing period. 
         [0048]    The term “within 24 hours following the onset of at least one symptom of NEC” refers to administering at least a first unit dose of a HB-EGF product and/or unit dose of somatic stem cells, such as MSC or ISC, within about 24 hours following the first clinical sign or symptom of NEC. The first doses may be succeeded by subsequent dosing outside the initial 24 hour dosing period. 
         [0049]    The HB-EGF product and/or somatic stem cells, such as MSC or ISC, may be administered to a patient suffering from an intestinal injury or an infant, including a premature infant, once a day (QD), twice a day (BID), three times a day (TID), four times a day (QID), five times a day (FID), six times a day (HID), seven times a day or 8 times a day. The HB-EGF product and/or somatic stem cells, such as MSC or ISC, may be administered alone or in combination with feeding. The HB-EGF product and/or somatic stem cells, such as MSC or ISC, may be administered to an infant with formula or breast milk with every feeding or a portion of feedings. 
         [0050]    The invention also provides for methods of improving the clinical outcome of a human subject at risk for or suffering from an intestinal injury, such as NEC, or HS- or HS/R- or I/R-induced intestinal injury, comprising administering a HB-EGF product and somatic cells, such as MSC or ISC, in an amount effective to protect the intestine of the human subject from NEC or HS- or HS/R- or I/R-induced intestinal injury. 
         [0051]    The methods of the invention may be carried out with any HB-EGF product including recombinant HB-EGF produced in  E. coli  and HB-EGF produced in yeast. The development of expression systems for the production of recombinant proteins is important for providing a source of protein for research and/or therapeutic use. Expression systems have been developed for both prokaryotic cells such as  E. coli , and for eukaryotic cells such as yeast ( Saccharomyces, Pichia  and  Kluyveromyces  spp) and mammalian cells. 
         [0052]    The invention contemplates treating human subjects of any age including infants, children and adults. The methods of the invention may be carried out in any human subject at risk for or suffering from intestinal injury, such as patients suffering from shock, HS or HS/R. HS may be the result of any type of injury, severe hemorrhaging, trauma, surgery, spontaneous hemorrhaging, or intestinal tissue grafting (transplantation). HS causes hypotension with decreased blood flow to vital organs. Other conditions causing hypotension, although not strictly due to blood loss, may also benefit from treatment with a HB-EGF product, for example, patients with major burns, shock due to sepsis or other causes, and major myocardial infarction to name a few. In certain embodiments, the methods of the invention may be carried out in any human subject other than a subject suffering from necrotizing enterocolitis. 
         [0053]    In addition, the invention contemplates treating patients of any age including infants, children and adults suffering from intestinal inflammatory conditions, intestinal infections, Hirschprung&#39;s Disease, intestinal dysmotility disorders, intestinal pseudo-obstruction (Ogilvie&#39;s Syndrome), inflammatory bowel disease, irritable bowel syndrome or chronic constipation, Crohn&#39;s Disease, bowel cancer, colorectal cancers. 
       EGF Receptor Agonists 
       [0054]    The Epidermal Growth Factor Receptor (EGFR) is a transmembrane glycoprotein that is a member of the protein kinase superfamily. The EGFR is a receptor for members of the epidermal growth factor family. Binding of the protein to a receptor agonist induces receptor dimerization and tyrosine autophosphorylation, and leads to cell proliferation and various other cellular effects (e.g. chemotaxis, cell migration). 
         [0055]    The amino acid sequence of the EGF receptor is set out as SEQ ID NO: 16 (Genbank Accession No. NP — 005219). EGF receptors are encoded by the nucleotide sequence set out as SEQ ID NO: 15 (Genbank Accession No. NM — 005228). The EGF receptor is also known in the art as EGFR, ERBB, HER1, mENA, and PIG61. An EGF receptor agonist is a molecule that binds to and activates the EGF receptor so that the EGF receptor dimerizes with the appropriate partner and induces cellular signaling and ultimately results in an EGF receptor-induced biological effect, such as cell proliferation, cell migration or chemotaxis. Exemplary EGF receptor agonists include epidermal growth factor (EGF), heparin binding EGF (HB-EGF), transforming growth factor-α (TGF-α), amphiregulin, betacellulin, epiregulin, and epigen. 
       Epidermal Growth Factor 
       [0056]    Epidermal Growth Factor (EGF), also known as beta-urogastrone, URG and HOMG4, is a potent mitogenic and differentiation factor. The amino acid sequence of EGF is set out as SEQ ID NO: 4 (Genbank Accession No. NP — 001954). EGF is encoded by the nucleotide sequence set out as SEQ ID NO: 3 (Genbank Accession No. NM — 001963). 
         [0057]    As used herein, “EGF product” includes EGF proteins comprising about amino acid 1 to about amino acid 1207 of SEQ ID NO: 4; EGF proteins comprising about amino acid 1 to about amino acid 53 of SEQ ID NO: 4; fusion proteins comprising the foregoing EGF proteins; and the foregoing EGF proteins including conservative amino acid substitutions. In a specific embodiment, the EGF product is human EGF(1-53), which is a soluble active polypeptide. Conservative amino acid substitutions are understood by those skilled in the art. The EGF products may be isolated from natural sources, chemically synthesized, or produced by recombinant techniques. In order to obtain EGF products of the invention, EGF precursor proteins may be proteolytically processed in situ. The EGF products may be post-translationally modified depending on the cell chosen as a source for the products. 
         [0058]    The EGF products of the invention are contemplated to exhibit one or more biological activities of EGF, such as those described in the experimental data provided herein or any other EGF biological activity known in the art. For example, the EGF products of the invention may exhibit one or more of the following biological activities: cellular mitogenicity in a number of cell types including epithelial cells and smooth muscle cells, cellular survival, cellular migration, cellular differentiation, organ morphogenesis, epithelial cytoprotection, tissue tropism, cardiac function, wound healing, epithelial regeneration, promotion of hormone secretion such as prolactin and human gonadotrophin, pituitary hormones and steroids, and influence glucose metabolism. 
         [0059]    The present invention provides for the EGF products encoded by the nucleic acid sequence of SEQ ID NO: 4 or fragments thereof including nucleic acid sequences that hybridize under stringent conditions to the complement of the nucleotides sequence of SEQ ID NO: 3, a polynucleotide which is an allelic variant of SEQ ID NO: 3; or a polynucleotide which encodes a species homolog of SEQ ID NO: 4. 
       HB-EGF Polypeptide 
       [0060]    The cloning of a cDNA encoding human HB-EGF (or HB-EHM) is described in Higashiyama et al.,  Science,  251: 936-939 (1991) and in a corresponding international patent application published under the Patent Cooperation Treaty as International Publication No. WO 92/06705 on Apr. 30, 1992. Both publications are hereby incorporated by reference herein in their entirety. In addition, uses of human HB-EGF are taught in U.S. Pat. No. 6,191,109 and International Publication No. WO 2008/134635(Intl. Appl. No. PCT/US08/61772), also incorporated by reference in its entirety. 
         [0061]    The sequence of the protein coding portion of the cDNA is set out in SEQ ID NO: 1 herein, while the deduced amino acid sequence is set out in SEQ ID NO: 2. Mature HB-EGF is a secreted protein that is processed from a transmembrane precursor molecule (pro-HB-EGF) via extracellular cleavage. The predicted amino acid sequence of the full length HB-EGF precursor represents a 208 amino acid protein. A span of hydrophobic residues following the translation-initiating methionine is consistent with a secretion signal sequence. Two threonine residues (Thr75 and Thr85 in the precursor protein) are sites for O-glycosylation. Mature HB-EGF consists of at least 86 amino acids (which span residues 63-148 of the precursor molecule), and several microheterogeneous forms of HB-EGF, differing by truncations of 10, 11, 14 and 19 amino acids at the N-terminus have been identified. HB-EGF contains a C-terminal EGF-like domain (amino acid residues 30 to 86 of the mature protein) in which the six cysteine residues characteristic of the EGF family members are conserved and which is probably involved in receptor binding. HB-EGF has an N-terminal extension (amino acid residues 1 to 29 of the mature protein) containing a highly hydrophilic stretch of amino acids to which much of its ability to bind heparin is attributed. Besner et al.,  Growth Factors,  7: 289-296 (1992), which is hereby incorporated by reference herein, identifies residues 20 to 25 and 36 to 41 of the mature HB-EGF protein as involved in binding cell surface heparin sulfate and indicates that such binding mediates interaction of HB-EGF with the EGF receptor. 
         [0062]    As used herein, “HB-EGF product” includes HB-EGF proteins comprising about amino acid 63 to about amino acid 148 of SEQ ID NO: 2 (HB-EGF(63-148)); HB-EGF proteins comprising about amino acid 73 to about amino acid 148 of SEQ ID NO: 2 (HB-EGF(73-148)); HB-EGF proteins comprising about amino acid 74 to about amino acid 148 of SEQ ID NO: 2 (HB-EGF(74-148)); HB-EGF proteins comprising about amino acid 77 to about amino acid 148 of SEQ ID NO: 2 (HB-EGF(77-148)); HB-EGF proteins comprising about amino acid 82 to about amino acid 148 of SEQ ID NO: 2 (HB-EGF(82-148)); HB-EGF proteins comprising a continuous series of amino acids of SEQ ID NO: 2 which exhibit less than 50% homology to EGF and exhibit HB-EGF biological activity, such as those described herein; fusion proteins comprising the foregoing HB-EGF proteins; and the foregoing HB-EGF proteins including conservative amino acid substitutions. In a specific embodiment, the HB-EGF product is human HB-EGF(74-148). Conservative amino acid substitutions are understood by those skilled in the art. The HB-EGF products may be isolated from natural sources known in the art (e.g., the U-937 cell line (ATCC CRL 1593)), chemically synthesized, or produced by recombinant techniques such as disclosed in WO92/06705, supra, the disclosure of which is hereby incorporated by reference. In order to obtain HB-EGF products of the invention, HB-EGF precursor proteins may be proteolytically processed in situ. The HB-EGF products may be post-translationally modified depending on the cell chosen as a source for the products. 
         [0063]    The HB-EGF products of the invention are contemplated to exhibit one or more biological activities of HB-EGF, such as those described in the experimental data provided herein or any other HB-EGF biological activity known in the art. One such biological activity is that HB-EGF products compete with HB-EGF for binding to the ErbB-1 receptor and has ErbB-1 agonist activity. In addition, the HB-EGF products of the invention may exhibit one or more of the following biological activities: cellular mitogenicity, cellular chemoattractant, endothelial cell migration, acts as a pro-survival factor (protects against apoptosis), decrease inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production in epithelial cells, decrease nuclear factor-κB (NF-κB) activation, increase eNOS (endothelial nitric oxide synthase) and NO production in endothelial cells, stimulate angiogenesis and promote vasodilatation. 
         [0064]    The present invention provides for the HB-EGF products encoded by the nucleic acid sequence of SEQ ID NO: 1 or fragments thereof including nucleic acid sequences that hybridize under stringent conditions to the complement of the nucleotides sequence of SEQ ID NO: 1, a polynucleotide which is an allelic variant of any SEQ ID NO: 1; or a polynucleotide which encodes a species homolog of SEQ ID NO: 2. 
       Additional EGF Receptor Agonists 
       [0065]    Additional EGF receptor agonists include: Transforming Growth Factor-α (TGF-α), also known as TFGA, which has the amino acid sequence set out as SEQ ID NO: 6 (Genbank Accession No. NP — 001093161), and is encoded by the nucleotide sequence set out as SEQ ID NO: 5 (Genbank Accession No. NM — 001099691); amphiregulin, also known as AR, SDGF, CRDGF, and MGC13647, which has the amino acid sequence set out as SEQ ID NO: 8 (Genbank Accession No. NP — 001648), and is encoded by the nucleotide sequence set out as SEQ ID NO: 7 (Genbank Accession No. NM — 001657); betacellulin (BTG) which has the amino acid sequence set out as SEQ ID NO: 10 (Genbank Accession No. NP — 001720), and is encoded by the nucleotide sequence set out as SEQ ID NO: 9 (Genbank Accession No. NM — 001729); Epiregulin (EREG), also known as ER, which has the amino acid sequence set out as SEQ ID NO: 12 (Genbank Accession No. NP — 001423) and is encoded by the nucleotide sequence set out as SEQ ID NO: 11 (Genbank Accession No. NM — 001432); and epigen (EPGN) also known as epithelial mitogen homolog, EPG, PRO9904, ALGV3072, FLJ75542, which has the amino acid sequence set out as SEQ ID NO: 14 (Genbank Accession No. NP — 001013460), and is encoded by the nucleotide sequence set out as SEQ ID NO: 13 (Genbank Accession No. NM — 001013442). 
         [0066]    The EGF receptor agonists also may be encoded by nucleotide sequences that are substantially equivalent to any of the EGF receptor agonists polynucleotides recited above. Polynucleotides according to the invention can have at least, e.g., 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, or 89%, more typically at least 90%, 91%, 92%, 93%, or 94% and even more typically at least 95%, 96%, 97%, 98% or 99% sequence identity to the polynucleotides recited above. Preferred computer program methods to determine identity and similarity between two sequences include, but are not limited to, the GCG program package, including GAP (Devereux et al.,  Nucl. Acid. Res.,  12: 387, 1984; Genetics Computer Group, University of Wisconsin, Madison, Wis.), BLASTP, BLASTN, and FASTA (Altschul et al.,  J. Mol. Biol.,  215: 403-410, 1990). The BLASTX program is publicly available from the National Center for Biotechnology Information (NCBI) and other sources (BLAST Manual, Altschul et al. NCB/NLM/NIH Bethesda, Md. 20894; Altschul et al.,  J. Mol. Biol.,  215: 403-410, 1990). The well known Smith Waterman algorithm may also be used to determine identity. 
         [0067]    Included within the scope of the nucleic acid sequences of the invention are nucleic acid sequence fragments that hybridize under stringent conditions to any of SEQ ID NOS: 1, 3, 5, 7, 9, 11 and 13, or compliments thereof, which fragment is greater than about 5 nucleotides, preferably 7 nucleotides, more preferably greater than 9 nucleotides and most preferably greater than 17 nucleotides. Fragments of, e.g., 15, 17, or 20 nucleotides or more that are selective for (i.e., specifically hybridize to any one of the polynucleotides of the invention) are contemplated. 
         [0068]    The term “stringent” is used to refer to conditions that are commonly understood in the art as stringent. Hybridization stringency is principally determined by temperature, ionic strength, and the concentration of denaturing agents such as formamide. Examples of stringent conditions for hybridization and washing are 0.015 M sodium chloride, 0.0015 M sodium citrate at 65-68° C. or 0.015 M sodium chloride, 0.0015M sodium citrate, and 50% formamide at 42° C. See Sambrook et al.,  Molecular Cloning: A Laboratory Manual,  2nd Ed., Cold Spring Harbor Laboratory, (Cold Spring Harbor, N.Y. 1989). More stringent conditions (such as higher temperature, lower ionic strength, higher formamide, or other denaturing agent) may also be used, however, the rate of hybridization will be affected. In instances wherein hybridization of deoxyoligonucleotides is concerned, additional exemplary stringent hybridization conditions include washing in 6×SSC 0.05% sodium pyrophosphate at 37° C. (for 14-base oligos), 48° C. (for 17-base oligos), 55° C. (for 20-base oligos), and 60° C. (for 23-base oligos). 
         [0069]    Other agents may be included in the hybridization and washing buffers for the purpose of reducing non-specific and/or background hybridization. Examples are 0.1% bovine serum albumin, 0.1% polyvinyl-pyrrolidone, 0.1% sodium pyrophosphate, 0.1% sodium dodecylsulfate, NaDodSO 4 , (SDS), ficoll, Denhardt&#39;s solution, sonicated salmon sperm DNA (or other non-complementary DNA), and dextran sulfate, although other suitable agents can also be used. The concentration and types of these additives can be changed without substantially affecting the stringency of the hybridization conditions. Hybridization experiments are usually carried out at pH 6.8-7.4, however, at typical ionic strength conditions, the rate of hybridization is nearly independent of pH. See Anderson et al.,  Nucleic Acid Hybridisation: A Practical Approach , Ch. 4, IRL Press Limited (Oxford, England). Hybridization conditions can be adjusted by one skilled in the art in order to accommodate these variables and allow DNAs of different sequence relatedness to form hybrids. 
         [0070]    The EGF receptor agonists of the invention include, but are not limited to, a polypeptide comprising: the amino acid sequences encoded by the nucleotide sequence of any one of SEQ ID NOS: 1, 3, 5, 7, 9, 11 and 13, or the corresponding full length or mature protein. In one embodiment, polypeptides of the invention also include polypeptides preferably with EGF receptor agonist biological activity described herein that are encoded by: (a) an open reading frame contained within any one of the nucleotide sequences set forth as SEQ ID NO: 1, 3, 5, 7, 9, 11 and 13, preferably the open reading frames therein or (b) polynucleotides that hybridize to the complement of the polynucleotides of (a) under stringent hybridization conditions. In another embodiment, polypeptides of the invention also include polypeptides preferably with EGF receptor agonist biological activity described herein that are encoded by: (a) an open reading frame contained within the nucleotide sequences set forth any as SEQ ID NO: 1, 3, 5, 7, 9, 11 and 13, preferably the open reading frames therein or (b) polynucleotides that hybridize to the complement of the polynucleotides of (a) under stringent hybridization conditions. 
         [0071]    The EGF receptor agonists of the invention also include biologically active variants of any of the amino acid sequences of SEQ ID NO: 2, 4, 6, 8, 10, 12 and 14; and “substantial equivalents” thereof with at least, e.g., about 65%, about 70%, about 75%, about 80%, about 85%, 86%, 87%, 88%, 89%, at least about 90%, 91%, 92%, 93%, 94%, typically at least about 95%, 96%, 97%, more typically at least about 98%, or most typically at least about 99% amino acid identity) that retain EGF receptor agonist biological activity. Polypeptides encoded by allelic variants may have a similar, increased, or decreased activity compared to polypeptides having the amino acid sequence of any of SEQ ID NO: 2, 4, 6, 8, 10, 12 and 14. 
         [0072]    The EGF receptor agonists of the invention include polypeptides with one or more conservative amino acid substitutions that do not affect the biological activity of the polypeptide. Alternatively, the EGF receptor agonist polypeptides of the invention are contemplated to have conservative amino acids substitutions which may or may not alter biological activity. The term “conservative amino acid substitution” refers to a substitution of a native amino acid residue with a normative residue, including naturally occurring and normaturally occurring amino acids, such that there is little or no effect on the polarity or charge of the amino acid residue at that position. For example, a conservative substitution results from the replacement of a non-polar residue in a polypeptide with any other non-polar residue. Further, any native residue in the polypeptide may also be substituted with alanine, according to the methods of “alanine scanning mutagenesis.” Naturally occurring amino acids are characterized based on their side chains as follows: basic: arginine, lysine, histidine; acidic: glutamic acid, aspartic acid; uncharged polar: glutamine, asparagine, serine, threonine, tyrosine; and non-polar: phenylalanine, tryptophan, cysteine, glycine, alanine, valine, proline, methionine, leucine, norleucine, isoleucine. 
       Expression of HB-EGF by Stem Cells 
       [0073]    The invention provides for transforming or transfecting somatic stem cells, such as MSC or ISC, with a nucleic acid encoding the amino acid sequence of a HB-EGF product. The transformed somatic stem cells are then administered to a patient suffering from an intestinal injury in any of the methods of the invention which results in administration of the HB-EGF product and the somatic stem cell concurrently. 
         [0074]    A nucleic acid molecule encoding the amino acid sequence of an HB-EGF product may be inserted into an appropriate expression vector that is functional in stem cells using standard ligation techniques. Exemplary vectors that function in somatic stem cells include bacterial vectors, eukaryotic vectors, plasmids, cosmids, viral vectors, adenovirus vectors and adenovirus associated vectors. 
         [0075]    The expression vectors preferably may contain sequences for cloning and expression of exogenous nucleotide sequences. Such sequences may include one or more of the following nucleotide sequences: a promoter, one or more enhancer sequences, an origin of replication, a transcriptional termination sequence, a complete intron sequence containing a donor and acceptor splice site, a sequence encoding a leader sequence for polypeptide secretion, a ribosome binding site, a polyadenylation sequence, a polylinker region for inserting the nucleic acid encoding the polypeptide to be expressed, and a selectable marker element. 
         [0076]    The vector may contain a sequence encoding a “tag”, such as an oligonucleotide molecule located at the 5′ or 3′ end of the HB-EGF product coding sequence; an oligonucleotide sequence encoding polyHis (such as hexaHis), FLAG, hemaglutinin influenza virus (HA) or myc or other tags for which commercially available antibodies exist. This tag may be fused to the HB-EGF product upon expression. A selectable marker gene element encoding a protein necessary for the survival and growth of a host cell grown in a selective culture medium may also be a component of the expression vector. Exemplary selection marker genes include those that encode proteins that complement auxotrophic deficiencies of the cell; or supply critical nutrients not available from complex media. 
         [0077]    A leader, or signal, sequence may be used to direct the HB-EGF product out of the stem cell after administration. For example, a nucleotide sequence encoding the signal sequence is positioned in the coding region of the HB-EGF product nucleic acid, or directly at the 5′ end of the HB-EGF coding region. The signal sequence may be homologous or heterologous to the HB-EGF product gene or cDNA, or chemically synthesized. The secretion of the HB-EGF product from the stem cell via the presence of a signal peptide may result in the removal of the signal peptide from the secreted HB-EGF product. The signal sequence may be a component of the vector, or it may be a part of the nucleic acid molecule encoding the HB-EGF product that is inserted into the vector. 
         [0078]    The expression vectors used in the methods of the invention may contain a promoter that is recognized by the host organism and operably linked to the nucleic acid sequence encoding the HB-EGF product. Promoters are untranscribed sequences located upstream to the start codon of a structural gene that control the transcription of the structural gene. Inducible promoters initiate increased levels of transcription from DNA under their control in response to some change in culture conditions, such as the presence or absence of a nutrient or a change in temperature. Alternatively, constitutive promoters initiate continual gene product production with little or no control over gene expression. A large number of promoters, recognized by a variety of potential host cells, are well known. A suitable promoter is operably linked to the nucleic acid molecule encoding the HB-EGF product. The native HB-EGF gene promoter sequence may be used to direct amplification and/or expression of a HB-EGF product nucleic acid molecule. A heterologous promoter also may be used to induce greater transcription and higher yields of the HB-EGF product expression as compared to HB-EGF expression induced by the native promoter. 
         [0079]    In addition, an enhancer sequence may be inserted into the vector to increase the transcription of a DNA encoding the HB-EGF product. Enhancers are cis-acting elements of DNA, usually about 10-300 bp in length, that act on the promoter to increase transcription. Enhancer sequences available from mammalian genes include globin, elastase, albumin, alpha-feto-protein and insulin. Exemplary viral enhancers that activate eukaryotic promoters include the SV40 enhancer, the cytomegalovirus early promoter enhancer, the polyoma enhancer, and adenovirus enhancers. While an enhancer may be spliced into the vector at a position 5′ or 3′ to a nucleic acid molecule encoding the HB-EGF product, it is typically located at a site 5′ from the promoter. 
         [0080]    The transformation of an expression vector encoding a HB-EGF product into a stem cell may be accomplished by well-known methods such as transfection, infection, calcium chloride, electroporation, microinjection, lipofection or the DEAE-dextran method or any other technique known in the art. These methods and other suitable methods are well known in the art, for example, in Sambrook, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press; 3rd ed., 2001. 
       Somatic Stem Cells 
       [0081]    Stem cells are cells with the ability to divide for indefinite periods in culture to give rise to specialized cells. The term “somatic stem cell” or “adult stem cell” refers to undifferentiated cells, found among differentiated cells within a tissue or organ, which has the capacity for self-renewal and differentiation. The somatic stem cells can differentiate to yield some or all of the major specialized cell types of the renewable tissue or organ. The primary role of somatic stem cells is to maintain and repair the tissue in which they are found. 
         [0082]    Somatic stem cells may be used for transplantation. For example, the invention provides for methods of transplanting somatic stem cells to treat intestinal injury or to reduce the damage to the intestine in a patient suffering from an intestinal injury. Exemplary somatic stem cells include hematopoietic stem cells, mesenchymal stem cells, intestinal stem cells, skeletal stem cells, hepatocyte stem cells, neural stem cells, skin stem cells, endothelial stem cells, mammary stem cells, and neural crest stem cells. 
       Mesenchymal Stem Cells 
       [0083]    “Mesenchymal stem cells” (MSC) are non-hematopoietic, pluripotent, self-renewing progenitor cells with a characteristic spindle-shaped morphology. These cells are derived from immature embryonic connective tissue (mesoderm layer). 
         [0084]    MSC have been shown to contribute to the maintenance and regeneration of various connective tissues. (Pittenger et al., Science 1999; 284(5411):143-7) MSC differentiate into a number of cell types, including chondrocytes, bone, fat, cells that support the formation of blood, and fibrous connective tissue. 
         [0085]    MSC are mobilized from bone marrow in response to tissue injury to aid in repair after a variety of end organ injury-models including models of myocardial infarction (Kawada et al.,  Blood  2004; 104:3581-7), spinal cord injury (Koda et al.,  Neuroreport  2005; 16:1763-7), renal ischemia/reperfusion injury (Togel et al.,  Am J Physiol Renal Physiol  2005; 289:F31-42) and intestinal radiation injury (Zhang et al.,  J Biomed Sci  2008; 15:585-94). 
         [0086]    Mesenchymal stem cells may be isolated from various tissues including but not limited to bone marrow (denoted as BM-MSC herein), peripheral blood, blood, placenta, and adipose tissue and amniotic fluid (denoted as AF-MCS herein) Exemplary methods of isolating mesenchymal stem cells from bone marrow are described in (Phinney et al.,  J Cell Biochem  1999; 72(4):570-85), from amniotic fluid (Baghaban et al.,  Arch Iran Med  2011; 14(2):96-103), from peripheral blood are described by Kassis et al. ( Bone Marrow Transplant.  2006 May; 37(10):967-76), from placental tissue are described by Zhang et al. ( Chinese Medical Journal,  2004, 117 (6):882-887), from adipose tissue, placental and cord blood mesenchymal stem cells are described by Kern et al. ( Stem Cells,  2006; 24:1294-1301). 
         [0087]    The mesenchymal stem cells may be characterized usng structural phenotypes. For example, the cells of the present invention may show a morphology similar to that of mesenchymal stem cells (a spindle-like morphology). Alternatively or additionally, the MSC may be characterized by the expression of one or more surface markers. Exemplary MSC surface markers include but are not limited to CD105+, CD29+, CD44+, CD90+, CD73+, CD105+, CD166+, CD49+, SH(1), SH(2), SH(3), SH(4), CD14−, CD34−, CD45−, CD19−, CD5−, CD20−, CD11B−, FMC7− and HLA class 1 negative. Other mesenchymal stem cell markers include but are not limited to tyrosine hydroxylase, nestin and H-NF. 
         [0088]    Examples of cells derived from mesenchymal cells include (1) cells of the cardiovascular system such as endothelial cells or cardiac muscle cells or the precursor cells of the cells of the cardiovascular system, and cells having the properties of these cells; (2) cells of any one of bone, cartilage, tendon and skeletal muscle, the precursor cells of the cells of any one of bone, cartilage, tendon, skeletal muscle and adipose tissue, and the cells having the properties of these cells; (3) neural cells or the precursor cells of neural cells, and the cells having the properties of these cells; (4) endocrine cells or the precursor cells of endocrine cells, and the cells having the properties of these cells; (5) hematopoietic cells or the precursor cells of hematopoietic cells, and the cells having the properties of these cells; and (6) hepatocytes or the precursor cells of hepatocytes, and the cells having the properties of these cells. 
         [0089]    Methods of mesenchymal cell culture are well known in the art of cell culturing (see, for example, Friedenstein et al.,  Exp Hematol  1976 4, 267-74; Dexter et al.  J Cell Physiol  1977, 91:335-44; and Greenberger,  Nature  1978 275, 7524). For example, mesenchymal cells are derived from a source selected from the group consisting of endothelial cells, cardiac muscle cells, bone cells, cartilage cells, tendon cells, skeletal muscle cells, bone cells, cartilage cells, tendon cells, adipose tissue cells, neural cells, endocrine cells, hematopoietic cells, hematopoietic precursor cells, bone marrow cells, and the precursor cells thereof, hepatocytes, and hepatocyte precursor cells. 
         [0090]    The marrow or isolated mesenchymal stem cells can be autologous, allogeneic or from xenogeneic sources, and can be embryonic or from post-natal sources. Bone marrow cells may be obtained from iliac crest, femora, tibiae, spine, rib or other medullary spaces. Other sources of human mesenchymal stem cells include embryonic yolk sac, placenta, umbilical cord, periosteum, fetal and adolescent skin, and peripheral, circulating blood. 
       Intestinal Stem Cells 
       [0091]    The lining of the intestines is composed of millions of villi and crypts, which form a barrier against bacterial invasion. The intestinal epithelium is the most rapidly proliferating tissue in adult mammals. Intestinal stem cells (ISCs) are responsible for self-renewal of the epithelium, and also represent a reserve pool of cells that can be activated after injury. The estimated number of stem cells is 4-6 per crypt. (Barker et al.,  Gastroenterology  2007; 133:1755-1760) Stem cells have been proven to be crucial for the recovery and regeneration of several tissues including the intestinal epithelium. (Vaananen et al.,  Ann Med  2005; 37:469-479). In the past, ISCs were identified at position +4 from the crypt bottom, directly above the Paneth cells. It is now thought that there may be two populations of ISCs, a slowly cycling quiescent reserve population above the Paneth cells (upper stem cell zone, USZ) (the +4 cells), and a more rapidly cycling (every 24 hours) active pool of crypt base columnar (CBC) cells located between the Paneth cells (lower stem cell zone, LSZ). The more active ISCs may maintain homeostatic regenerative capacity of the intestine with the more quiescent ISCs held in reserve. (Scoville et al.,  Gastroenterology  2008 136: 849-864) Several signaling pathways including the Wnt/b-catenin, BMP, RTK/PI3K and Notch cascades are critical to ISC self-renewal and proliferation. Among them, Wnt/b-catenin is the signature/signaling pathway, and its downstream regulated genes represent potential ISC markers. The Wnt/b-catenin target gene LGR5 has been recently identified as a marker for CBC ISCs. (Sato et al.,  Nature  2009; 459:262-265) Prominin-1 is also expressed in ISC. (Snippert et al.,  Gastroenterology  2009; 136:2187-2194, Zhu et al., Nature 2009; 457: 603-607). 
         [0092]    The integrity of the intestinal epithelium is ensured by pluripotent, self-renewing and proliferative stem cells. Barker et al.,  Gastroenterology  2007; 133:1755-1760, Potten et al.,  Cell Prolif  2009; 42:731-750. These cells have only recently been identified using special markers such as Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) and prominin-1/CD133, in addition to classic +4 long retention cell characteristics. Barker et al., Nature 2007; 449:1003-1007, Snippert et al., Gastroenterology 2009; 136:2187-2194. Between 4 and 6 stem cells at each crypt base generate epithelial progenitor cells in the transit-amplifying (TA) zone, which subsequently differentiate and maintain intestinal homeostasis. Barker et al., Gastroenterology 2007; 133:1755-1760, Potten et al.,  Cell Prolif  2009; 42:731-750. They provide a fast-paced renewal of the four differentiated epithelial cell lineages, each of which has distinct important physiologic functions: enterocytes that absorb nutrients, goblet cells that produce protective mucus, Paneth cells that secrete antibacterial proteins and neuroendocrine cells that produce hormones. Scoville et al.,  Gastroenterology  2008; 134:849-864. Stresses such as intestinal ischemia can harm the intestinal epithelial cell (IEC) lineages, particularly the stem cells, thereby disrupting normal homeostasis and gut barrier function. Stem cells in some organs, including the intestines, have been shown to respond to stress and to promote recovery from injury. Markel et al.,  J Pediatr Surg  2008; 43:1953-1963. A previous study showed that bone marrow-derived progenitor cells have the ability to regenerate the intestine after injury. Gupta et al.,  Biomacromolecules  2006; 7:2701-2709. However, the role of intestinal stem cells (ISCs) in recovery from NEC is unknown. The ability to protect ISCs in the face of stress may represent a critical step in the prevention and treatment of NEC. 
         [0093]    Cell surface markers for ISC include but are not limited to LGR5 and prominin-1 (Barker et al.,  Nature  2007; 449:1003-1007, Snippert et al.,  Gastroenterology  2009; 136:2187-2194, Lee et al.,  Nat Neurosci  2005; 8:723-729, Zhu et al.,  Nature  2009; 457: 603-607, Chen et al.,  Growth Factors  2010; 28:82-97). 
       Embryonic Stem Cells 
       [0094]    Embryonic stem cells (ESC) are derived from embryos that were developed from eggs that have been fertilized using in vitro fertilization. Procedures for isolating and growing human primordial stem cells are described in U.S. Pat. No. 6,090,622. Human embryonic stem cells (hESCs) can be isolated from human blastocysts obtained from human in vivo preimplantation embryos, in vitro fertilized embryos, or one-cell human embryos expanded to the blastocyst stage (Bongso et al.,  Hum. Reprod.  4:706, 1989). Human embryos can be cultured to the blastocyst stage in G1.2 and G2.2 medium (Gardner et al.,  Fertil. Steril.  69:84, 1998). The zona pellucida is removed from blastocysts by brief exposure to pronase. The inner cell masses can be isolated by immunosurgery or by mechanical separation, and are plated on mouse embryonic feeder layers, or in an appropriate culture system. Inner cell mass-derived outgrowths are then dissociated into clumps using calcium and magnesium-free phosphate-buffered saline (PBS) with 1 mM EDTA, using dispase, collagenase, or trypsin, or by mechanical dissociation with a micropipette. The dissociated cells are then replated for colony formation. Colonies demonstrating undifferentiated morphology are individually selected by micropipette, mechanically dissociated into clumps, and replated. Embryonic stem cell-like morphology is characterized as compact colonies with apparently high nucleus to cytoplasm ratio and prominent nucleoli. 
         [0095]    The ESC may be cultured under conditions that support the substantially undifferentiation growth of the primordial stem cells using any suitable cell culture techinique known in the art. For example, the ESCs may be grown on synthetic or purified extracellular matrix using methods standard in the art. Alternatively, the ESC may be grown on extracellular matrix that contains laminin or a growth-arrested murine or human feeder cell layer (e.g., a human foreskin fibroblast cell layer) and maintained in a serum-free growth environment. 
         [0096]    Cell surface markers for ESC include, but are not limited to, alkine phosphatase, CD30, Cripto (TDGF-1), GCTM-2, Genesis, Germ cell nuclear factor, OCT-4/POU5F1, SSEA-3, SSEA-4, stem cell factor (SCF or c-kit ligand), TRA-1-60 and TRA-1-81. 
       Stem Cell Administration 
       [0097]    The invention provides for methods of administering isolated somatic stem cells, such as MSC or ISC. The term “isolated” refers to a cell that has been removed from its in vivo location (e.g. bone marrow, neural tissue). Preferably the isolated cell is substantially free from other substances (e.g., other cell types) that are present in its in vivo location. The stem cells of the present invention may be isolated or obtained using any technique, preferably known to those skilled in the art. 
         [0098]    The somatic stem cells used in any of the methods of the invention may be obtained from any autologous or non-autologous (i.e., allogeneic or xenogeneic) human donor. For example, cells may be isolated from a donor subject. The somatic stem cells of the present invention may be administered to the treated subject using a variety of transplantation approaches, depending on the site of implantation. 
         [0099]    Methods of culturing stem cells ex vivo are well known in the art. For example, see “Culture of Animal Cells—A Manual of Basic Technique” by Freshney, Wiley-Liss, N.Y. (1994), Third Edition, the teachings of which are hereby incorporated by reference. 
         [0100]    Culture medium compositions typically include essential amino acids, salts, vitamins, minerals, trace metals, sugars, lipids and nucleosides. Cell culture medium supplies the necessary components to meet the nutritional needs for cells to grow in a controlled, artificial and in vitro environment. Nutrient formulations, pH, and osmolarity vary in accordance with parameters such as cell type, cell density, and the culture system employed. Many cell culture medium formulations are known in the art and a number of media are commercially available. 
         [0101]    Once the culture medium is incubated with cells, it is known to those skilled in the art as “conditioned medium”. Conditioned medium contains many of the original components of the medium, as well as a variety of cellular metabolites and secreted proteins, including, for example, biologically active growth factors, inflammatory mediators and other extracellular proteins. 
         [0102]    Preconditioned media ingredients include, but are not limited to those described below. Additionally, the concentration of the ingredients is well known to one of ordinary skill in the art. See, for example, Methods For Preparation Of Media, Supplements and Substrate for Serum-free Animal Cell Cultures. The ingredients include amino-acids (both D and/or L-amino acids) such as glutamine, alanine, arginine, asparagine, cystine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and vatine and their derivatives; acid soluble subgroups such as thiamine, ascorbic acid, ferric compounds, ferrous compounds, purines, glutathione and monobasic sodium phosphates. 
         [0103]    Additional ingredients include sugars, deoxyribose, ribose, nucleosides, water soluble vitamins, riboflavin, salts, trace metals, lipids, acetate salts, phosphate salts, HEPES, phenol red, pyruvate salts and buffers. 
         [0104]    Other ingredients often used in media formulations include fat soluble vitamins (including A, D, E and K) steroids and their derivatives, cholesterol, fatty acids and lipids Tween 80, 2-mercaptoethanol pyramidines as well as a variety of supplements including serum (fetal, horse, calf, etc.), proteins (insulin, transferrin, growth factors, hormones, etc.) antibiotics (gentamicin, penicillin, streptomycin, amphotericin B, etc.) whole egg ultra filtrate, and attachment factors (fibronectins, vitronectins, collagens, laminins, tenascins, etc.). The media may or may not need to be supplemented with growth factors and other proteins such as attachment factors. 
         [0105]    The term “transplantation,” “cell replacement” or “grafting” are used interchangeably herein and refer to the introduction of the somatic stem cells of the present invention to target tissue such as areas of intestinal injury. The cells can be derived from the transplantation recipient or from an allogeneic or xenogeneic donor. 
         [0106]    For example, the cells can be grafted into the intestine. Conditions for successful transplantation include: (i) viability of the implant; (ii) retention of the graft at the site of transplantation; and (iii) minimum amount of pathological reaction at the site of transplantation. 
         [0107]    For administration of the stem cells, an effective amount of the stem cells are diluted in suitable carriers. Exemplary carriers include phosphate buffered saline (PBS), culture medium and other buffered solutions. 
         [0108]    The isolated stem cells may be administered by intravenous injection, by intraperitoneal injection or by preparing a cavity by surgical means to expose the intestine and then depositing the graft into the cavity. The cells may also be transplanted to a healthy region of the tissue. In some cases the exact location of the damaged tissue area may be unknown and the cells may be inadvertently transplanted to a healthy region. In other cases, it may be preferable to administer the cells to a healthy region, thereby avoiding any further damage to the injured region. Then following transplantation, the cells preferably migrate to the damaged area. 
         [0109]    Since non-autologous stems cell may induce an immune reaction when administered to the body, steps may be necessary to decrease the likelihood of rejection of the stem cells. These steps include suppressing the recipient immune system or encapsulating the non-autologous stem cells in immunoisolating, semipermeable membranes before transplantation. 
         [0110]    Encapsulation techniques are generally classified as microencapsulation, involving small spherical vehicles and macroencapsulation, involving larger flat-sheet and hollow-fiber membranes (Uludag et al.  Adv Drug Deliv Rev.  2000; 42: 29-64). Exemplary methods of preparing microcapsules include those made of alginate and alpha-phenoxycinnamylidene-acetylated poly(allylamine) (Lu et al.,  Biotechnol Bioeng.  2000, 70: 479-83) and photosensitive poly(allylamine alpha-cyanocinnamylideneacetate) ( J Microencapsul.  2000, 17: 245-51). In addition, microcapsules are prepared by complexing modified collagen with a ter-polymer shell of 2-hydroxyethyl methylacrylate (HEMA), methacrylic acid (MAA) and methyl methacrylate (MMA), resulting in a capsule thickness of 2-5 μm. Such microcapsules can be further encapsulated with additional 2-5 μm ter-polymer shells in order to impart a negatively charged smooth surface and to minimize plasma protein absorption (Chia. et al.  Biomaterials.  2002 23: 849-56). 
         [0111]    Other microcapsules are based on alginate, a marine polysaccharide (Sambanis et al.,  Diabetes Technol. Ther.  2003, 5: 665-8) or its derivatives. For example, microcapsules can be prepared by the polyelectrolyte complexation between the polyanions sodium alginate and sodium cellulose sulphate with the polycation poly(methylene-co-guanidine) hydrochloride in the presence of calcium chloride. 
         [0112]    It will be appreciated that cell encapsulation is improved when smaller capsules are used. Thus, the quality control, mechanical stability, diffusion properties, and in vitro activities of encapsulated cells improved when the capsule size was reduced from 1 mm to 400 μm (Canaple et al.,  J Biomater Sci Polym Ed.  2002; 13:783-96). Moreover, nanoporous biocapsules with well-controlled pore size as small as 7 nm, tailored surface chemistries and precise microarchitectures were found to successfully immunoisolate microenvironments for cells (Williams  Med Device Technol.  1999, 10: 6-9; Desai,  Expert Opin Biol Ther.  2002, 2: 633-46). 
         [0113]    Examples of immunosuppressive agents that may be administered in conjunction with the methods of the invention include, but are not limited to, methotrexate, cyclophosphamide, cyclosporine, cyclosporin A, chloroquine, hydroxychloroquine, sulfasalazine (sulphasalazopyrine), gold salts, D-penicillamine, leflunomide, azathioprine, anakinra, infliximab (REMICADE), etanercept, TNFα. blockers, a biological agent that targets an inflammatory cytokine, and Non-Steroidal Anti-Inflammatory Drug (NSAIDs). Examples of NSAIDs include, but are not limited to acetyl salicylic acid, choline magnesium salicylate, diflunisal, magnesium salicylate, salsalate, sodium salicylate, diclofenac, etodolac, fenoprofen, flurbiprofen, indomethacin, ketoprofen, ketorolac, meclofenamate, naproxen, nabumetone, phenylbutazone, piroxicam, sulindac, tolmetin, acetaminophen, ibuprofen, Cox-2 inhibitors and tramadol. 
       Necrotizing Enterocolitis 
       [0114]    Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in premature newborn infants (Schnabl et al.,  World J Gastroenterol  14:2142-2161, 2008; Kliegman et al.,  N Engl J Med  310:1093-103, 1984). With aggressive management leading to the salvage of premature infants from the pulmonary standpoint, the incidence of NEC is increasing, and it is thought that NEC will soon replace pulmonary insufficiency as the leading cause of death in premature infants (Lee et al.,  Semin Neonatol  8:449-59, 2003). The mortality of this disease ranges from 20% to 50%, resulting in over 1000 infant deaths in this country each year (Caplan et al.,  Pediatr  13: 111-115, 2001) Like other diseases manifested by severe intestinal injury, NEC can cause the dysregulated inflammation characteristic of the systemic inflammatory response syndrome (SIRS), potentially resulting in multiple organ dysfunction syndrome (MODS) and death. Evidence suggests that the risk factors for NEC, namely formula feeding, intestinal ischemia and bacterial colonization, stimulate proinflammatory mediators that in turn activate a series of events culminating in necrosis of the bowel (Caplan et al.,  Pediatr  13: 111-115, 2001). Survivors of acute NEC frequently develop malabsorption, malnutrition, total parenteral nutrition-related complications, intestinal strictures and short bowel syndrome (Caplan et al.,  Pediatr  13:111-115, 2001). 
         [0115]    Since prematurity is the single most important risk factor for NEC, it is possible that absent or reduced levels of specific factors that are normally expressed during later periods of gestation may contribute to the development of this condition. With this in mind, exogenous replacement of key factors may be clinically valuable as a means to reduce the incidence of NEC. Several potential preventive strategies have aimed at induction of gastrointestinal maturation with steroids, improvement in host defense with breast milk feeding or oral immunoglobulins, change in bacterial colonization with antibiotics, probiotics or feeding modifications, and reduction or antagonism of inflammatory mediators, none of which have led to consistently positive therapeutic results (Feng et al.,  Semin Pediatr Surg  14:167-74, 2005). 
       Hemorrhagic Shock 
       [0116]    Shock is a state of inadequate perfusion, which does not sustain the physiologic needs of organ tissues. Hemorrhagic shock (HS) refers to shock that is caused by blood loss that exceeds the ability of the body to compensate and to provide adequate tissue perfusion and oxygenation. HS is frequently caused by trauma, but also may be caused by spontaneous hemorrhage (e.g., GI bleeding, childbirth), surgery, and other causes. Frequently, an acute bleeding episode will cause HS, but HS may also occur in chronic conditions with subacute blood loss. 
         [0117]    Untreated HS can lead to death. Without intervention, a classic trimodal distribution is seen in severe HS. An initial peak of mortality occurs within minutes of hemorrhage due to immediate exsanguination. Another peak occurs after 1 to several hours due to progressive decompensation. A third peak occurs days to weeks later due to sepsis and organ failure. Therefore, the methods of the invention preferably are carried out during the early stages of HS such as after or during the initial peak, or before or during the second peak (1 to several hours after the initial hemorrhage). 
         [0118]    A person in shock has extremely low blood pressure. Depending on the specific cause and type of shock, symptoms will include one or more of the following: anxiety, agitation, confusion, pale, cool and clammy skin, low or no urine production, bluish lips and fingernails, dizziness, light-headedness, faintness, profuse sweating, rapid but weak pulse, shallow breathing, chest pain and unconsciousness. 
         [0119]    Resuscitation during or after HS/R is known to have deletorious effects on the blood vessels of the patient. For example, HS/R is characterized by progressive deterioration of mesenteric blood flow. In addition, progressive intestinal hypoperfusion after HS/R contributes to loss of the gut mucosal barrier and to hypoxia-induced intestinal inflammation, both of which are critical to the initiation of MODS after HS/R. 
       The Role of HB-EGF in Intestinal Cytoprotection 
       [0120]    Induction and activation of the EGF receptor have been demonstrated in different tissues, including the intestines, during hypoxia and after ischemia. (Ellis et al.,  Biochem. J.  354:99-106, 2001; Lin et al.,  J Lab Clin Med;  125:724-33, 1995; Nishi et al.,  Cancer Res  62:827-34, 2002; Sondeen et al.,  J Lab Clin Med  134:641-8, 1999; Yano et al.,  Nephron  81:230-3, 1999). Previous studies have shown that HB-EGF mRNA and protein are induced after exposure of intestinal epithelial cells to anoxia/reoxygenation (A/R) in vitro, and after intestinal I/R injury in vivo. (Xia et al.,  J Invest Surg  16:57-63, 2003). Hypoxia and I/R have been found to induce HB-EGF transcription and protein synthesis in different tissues including the brain and kidney. (Homma et al.,  J Clin Invest  96:1018-25, 1995; Jin et al.,  J Neurosci  22:5365-73, 2002; Kawahara et al.,  J Cereb Blood Flow Metab  19:307-20, 1999; Sakai et al.,  J. Clin. Invest.;  99:2128-2138, 1997). During the early phases of hypoxia and oxidative stress, activation of EGFR and shedding of proHB-EGF occur, leading to immediate availability of soluble HB-EGF protein for targeting via autocrine or paracrine pathways. HB-EGF shedding is followed by the induction of transcription and de novo synthesis of HB-EGF (El-Assal et al.,  Semin Pediatr Surg  13:2-10, 2004). 
         [0121]    Intestinal epithelium undergoes a dynamic and continuous process of renewal and replacement with a turnover time of 3-6 days. (Potten et al.,  Am J Physiol  273:G253-7, 1997). Depending more on the depth of injury rather than the total surface area affected, the process of healing starts as early as a few minutes after injury (Ikeda et al.,  Dig Dis Sci  2002; 47:590-601, 2002). The most important priority during intestinal regeneration is reconstitution of epithelial cell continuity, allowing restoration of barrier function and prevention of systemic toxic complications. This is achieved by rapid epithelial cell migration from the wound edge, a process known as “restitution” (Ikeda et al.,  Dig Dis Sci  47:590-601, 2002; McCormack et al.,  Am J Physiol;  263:G426-35, 1992; Moore et al.  Am J Physiol  257:G274-83, 1989; Moore et al.  Gastroenterology  102:119-30, 1992). Early migration of goblet cells, which are more resistant to ischemia-induced cell death than enterocytes, serves as a source of both cell lining and mucous secretion, thus promoting rapid recovery of intestinal barrier function (Ikeda et al.,  Dig Dis Sci  47:590-601, 2002). Complete intestinal repair is achieved by proliferation and differentiation of crypt epithelium, which does not occur as early as restitution. Following administration of HB-EGF to rats exposed to intestinal I/R, a significant improvement in intestinal healing characterized by reduced mucosal damage was observed (Pillai et al.,  J Surg Res  87:225-31, 1999). In the early phase of intestinal healing HB-EGF was shown to induce intestinal restitution, (El-Assal et al.,  Gastroenterology  129:609-25, 2005) whereas in the later phase of healing HB-EGF promotes crypt cell proliferation (Xia et al.,  J Pediatr Surg  37:1081-7; 2002). In addition, the effects of HB-EGF in inducing restitution are mediated by both the PI3-kinase and MAPK intracellular signaling pathways (El-Assal et al.  Gastroenterology  129:609-25, 2005). HB-EGF administration leads to preservation of gut barrier function and intestinal permeability after intestinal I/R (El-Assal et al.  Gastroenterology  129:609-25, 2005), with resultant decrease in bacterial translocation (Xia et al.,  J Pediatr Surg  37:1081-7; 2002). It is important to note that the protective effects of HB-EGF administration are seen even when the growth factor is administered during or after the ischemic interval has already occurred (Martin et al.,  J Pediatr Surg.  40:1741-7, 2005). Thus, prophylactic administration of HB-EGF prior to ischemia is not required. Most importantly, HB-EGF improves survival in rats exposed to intestinal I/R injury (Pillai et al.,  J Surg Res  87:225-31, 1999). 
         [0122]    Additional studies demonstrated that treatment with HB-EGF reduced the generation of ROS in rats exposed to intestinal I/R in vivo and in leukocytes exposed to ROS-inducing stimuli in vitro (Kuhn et al.,  Antioxid Redox Signal  4:639-46, 2002). HB-EGF also preserved intestinal epithelial cell ATP levels in cells exposed to hypoxia (Pillai et al.,  J. Pediatr. Surg.  33:973-979, 1998). HB-EGF is known to downregulate expression of adhesion molecules including P- and E-selectin and intercellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1 (VCAM-1) after intestinal I/R (Xia et al.,  J Pediatr Surg  38:434-9. 2003). Downregulation of adhesion molecules was followed by reduced infiltration of leukocytes, which are critical mediators of I/R (Xia et al.,  J Pediatr Surg  38:434-9. 2003). 
         [0123]    Exposure of intestinal epithelium to I/R results in cell death, with apoptosis rather than necrosis as the major mechanism of cell death. One of the unique functions of HB-EGF is its ability to protect against apoptotic cell death. sHB-EGF is known to protect enterocytes from hypoxia-induced intestinal necrosis (Pillai et al.,  J. Pediatr. Surg.  33:973-979, 1998) and from pro-inflammatory cytokine-induced apoptosis (Michalsky et al.,  J Pediatr Surg  36:1130-5. 2001) in vitro. HB-EGF is also known to act as a pro-survival factor in cells exposed to various forms of stress including mechanical stress, serum starvation and exposure to cytotoxic agents. Recent studies have demonstrated that HB-EGF decreases intestinal epithelial cell apoptosis in vivo in a rat model of necrotizing enterocolitis (Feng et al.,  J Pediatr Surg  2006 41(4):742-7) 
         [0124]    Nitric oxide (NO) is another mediator of I/R-induced apoptosis and intestinal mucosal damage. Despite the protective effect of constitutive NO, there is ample evidence that high levels of NO induce apoptosis and mediate tissue damage in different cell types including intestinal epithelial cells during I/R. iNOS (inducible nitric oxide synthase) inhibitors led to attenuated NO production and decreased hypoxia-induced intestinal apoptosis with preservation of gut barrier function in rats with endotoxemia. Furthermore, iNOS knock-out mice are more resistant to intestinal I/R-induced mucosal injury. Collectively, these studies clearly indicate that reduction of iNOS can decrease I/R-induced intestinal damage. HB-EGF down-regulates cytokine-induced iNOS and NO production in intestinal epithelial cells in vitro, and I/R-induced intestinal iNOS expression and serum NO levels in vivo. HB-EGF has been shown to decrease iNOS and NO production in intestinal epithelial cells, which is dependent upon its ability to decrease nuclear factor-κB (NF-κB) activation in a PI3-kinase dependent fashion. Reduction of I/R-induced overproduction of NO in IEC represents an additional cytoprotective mechanism of HB-EGF. 
         [0125]    HB-EGF is a hypoxia- and stress-inducible gene that is involved in reduction of I/R-induced tissue damage. It promotes structural recovery after I/R by enhancing cell proliferation and by inducing migration of healthy epithelial cells from the edge of damaged tissues. In addition to promoting healing based on its positive trophic effects, HB-EGF also protects the intestine by decreasing leukocyte infiltration and production of injurious mediators after injury, thus protecting epithelial cells from apoptosis and necrosis. It is likely that reducing I/R-induced IEC death will ameliorate intestinal damage and reduce systemic complications. 
       Pharmaceutical Compositions 
       [0126]    The administration of a HB-EGF product is preferably accomplished with a pharmaceutical composition comprising a HB-EGF product and a pharmaceutically acceptable carrier. The carrier may be in a wide variety of forms depending on the route of administration. Suitable liquid carriers include saline, PBS, lactated Ringer solution, human plasma, human albumin solution, 5% dextrose and mixtures thereof. The route of administration may be oral, rectal, parenteral, intraluminally, or through a nasogastric or orogastric tube (enteral). Examples of parenteral routes of administration are intravenous, intra-arterial, intraperitoneal, intramuscular or subcutaneous injection or infusion. 
         [0127]    A preferred route of administration of the present invention is the enteral route. Therefore, the present invention contemplates that the acid stability of HB-EGF is a unique factor as compared to, for example, EGF. For example, the pharmaceutical composition of the invention may also include other ingredients to aid solubility, or for buffering or preservation purposes. Pharmaceutical compositions containing a HB-EGF product may comprise the HB-EGF product at a concentration of about 100 to 1000 μg/kg in saline. Suitable doses are in the range from 100-140 μg/kg, or 100-110 μg/kg, or 110-120 μg/kg, or 120-130 μg/kg, or 120-140 μg/kg, or 130-140 μg/kg, or 500-700 μg/kg, or 600-800 μg/kg or 800-1000 μg/kg. Preferred doses include 100 μg/kg, 120 μg/kg, 140 μg/kg and 600 μg/kg administered enterally once a day. Additional preferred doses may be administered once, twice, three, four, five, six or seven or eight times a day enterally. 
         [0128]    The pharmaceutical compositions of a HB-EGF product are administered as methods of the invention include a HB-EGF product which is associated or attached to a carrier that assists in stabilizing the agonist during administration. For example, the invention contemplates administering a HB-EGF product associated with a carrier that prevent digestion in the duodenal fluids such as polymers, phospholipids, hydrogels, polysaccharides and prodrugs, microparticles or nanoparticles. The pharmaceutical compositions may also comprise pH sensitive coatings or carriers for controlled release, pH independent biodegradable coatings or carriers or microbially controlled coatings or carriers. 
         [0129]    The dose of a HB-EGF product may also be administered intravenously. In addition, the dose of the HB-EGF product may be administered as a bolus, either once at the onset of therapy or at various time points during the course of therapy, such as every four hours, or may be infused for instance at the rate of about 0.01 μg/kg/h to about 5 μg/kg/h during the course of therapy until the patient shows signs of clinical improvement. Addition of other bioactive compounds [e.g., antibiotics, free radical scavenging or conversion materials (e.g., vitamin E, beta-carotene, BHT, ascorbic acid, and superoxide dimutase), fibrolynic agents (e.g., plasminogen activators), and slow-release polymers to the HB-EGF product or separate administration of the other bioactive compounds is also contemplated. 
         [0130]    As used herein, “pathological conditions associated with intestinal ischemia” includes conditions which directly or indirectly cause intestinal ischemia (e.g., premature birth, birth asphyxia, congenital heart disease, cardiac disease, polycythemia, hypoxia, exchange transfusions, low-flow states, atherosclerosis, embolisms or arterial spasms, ischemia resulting from vessel occlusions in other segments of the bowel, ischemic colitis, and intestinal torsion such as occurs in infants and particularly in animals) and conditions which are directly or indirectly caused by intestinal ischemia (e.g., necrotizing enterocolitis, shock, sepsis, and intestinal angina). Thus, the present invention contemplates administration of a HB-EGF product to patients in need of such treatment including patients at risk for intestinal ischemia, patients suffering from intestinal ischemia, and patients recovering from intestinal ischemia. The administration of a HB-EGF product to patients is contemplated in both the pediatric and adult populations. 
         [0131]    More particularly, the invention contemplates a method of reducing necrosis associated with intestinal ischemia comprising administering a HB-EGF product, to a patient at risk for, suffering from, or recovering from intestinal ischemia. Also contemplated is a method of protecting intestinal epithelial cells from hypoxia comprising exposing the cells to a HB-EGF product. Administration of, or exposure to, HB-EGF products reduces lactate dehyrogenase efflux from intestinal epithelial cells, maintains F-actin structure in intestinal epithelial cells, increases ATP levels in intestinal epithelial cells, and induces proliferation of intestinal epithelial cells. 
         [0132]    In view of the efficacy of HB-EGF in protecting intestinal tissue from ischemic events, it is contemplated that HB-EGF has a similar protective effect on myocardial, renal, spleen, lung, brain and liver tissue. 
       Administration to Pediatric Patients 
       [0133]    Intestinal injury related to an ischemic event is a major risk factor for neonatal development of necrotizing enterocolitis (NEC). NEC accounts for approximately 15% of all deaths occurring after one week of life in small premature infants. Although most babies who develop NEC are born prematurely, approximately 10% of babies with NEC are full-term infants. Babies with NEC often suffer severe consequences of the disease ranging from loss of a portion of the intestinal tract to the entire intestinal tract. At present, there are no known therapies to decrease the incidence of NEC in neonates. 
         [0134]    Babies considered to be at risk for NEC are those who are premature (less than 36 weeks gestation) or those who are full-term but exhibit, e.g., prenatal asphyxia, shock, sepsis, or congenital heart disease. The presence and severity of NEC is graded using the staging system of Bell et al.,  J. Ped. Surg.,  15:569 (1980) as follows: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Stage I 
                 Any one or more historical factors producing perinatal stress 
               
               
                 (Suspected 
                 Systemic manifestations - temperature instability, lethargy, 
               
               
                 NEC) 
                 apnea, bradycardia 
               
               
                   
                 Gastrointestinal manifestations - poor feeding, increased 
               
               
                   
                 pregavage residuals, emesis (may be bilious or test positive 
               
               
                   
                 for occult blood), mild abdominal distention, occult blood in 
               
               
                   
                 stool (no fissure) 
               
               
                 Stage II 
                 Any one or more historical factors 
               
               
                 (Definite 
                 Above signs and symptoms plus persistant occult or gross 
               
               
                 NEC) 
                 gastrointestinal bleeding, marked abdominal distention 
               
               
                   
                 Abdominal radiographs showing significant intestinal 
               
               
                   
                 distention with ileus, small-bowel separation (edema in bowel 
               
               
                   
                 wall or peritoneal fluid), unchanging or persistent “rigid” 
               
               
                   
                 bowel loops, pneumatosis intestinalls, portal venous gas 
               
               
                 Stage III 
                 Any one or more historical factors 
               
               
                 (Advanced 
                 Above sings and symptoms plus deterioration of vital signs, 
               
               
                 NEC) 
                 evidence of septic shock, or marked gastrointestinal 
               
               
                   
                 hemorrhage 
               
               
                   
                 Abdominal radiographs showing pneumoperitoneum in 
               
               
                   
                 addition to findings listed for Stage II 
               
               
                   
               
             
          
         
       
     
         [0135]    Babies at risk for or exhibiting NEC are treated as follows. Patients receive a daily liquid suspension of HB-EGF (e.g. about 1 mg/kg in saline or less). The medications are delivered via a nasogastric or orogastric tube if one is in place, or orally if there is no nasogastric or orogastric tube in place. 
     
    
     
       BRIEF DESCRIPTION OF DRAWING 
         [0136]      FIG. 1  depicts the percentage of pups that survived after exposure to experimental NEC alone or those exposed to NEC and treated with one of the following combinations: HB-EGF alone (NEC+HB-EGF), MSC alone administered intraperitoneally (NEC+MSC IP), HB-EGF and MSC administered intraperitoneally (NEC+HB-EGF+MSC IP), MSC alone administered intravenously (NEC+MSC IV), and HB-EGF and MSC administered intravenously (NEC+HB-EGF+MSC IV). The breastfed group was not exposed to NEC and 100% survived. 
           [0137]      FIG. 2  depicts the percentage of pups with high grade NEC after exposure to experimental NEC alone or those exposed to NEC and treated with one of the following combiantins: HB-EGF alone (NEC+HB-EGF), MSC alone administered intraperitoneally (NEC+MSC IP), HB-EGF and MSC administered intraperitoneally (NEC+HB-EGF+MSC IP), MSC alone administered intravenously (NEC+MSC IV), and HB-EGF and MSC administered intravenously (NEC+HB-EGF+MSC IV). The breastfed group was not exposed to NEC and did not have any incidence of high grade NEC. 
           [0138]      FIG. 3  depicts the number of labeled MCS that were engrafted within the intestine of the pups exposed to NEC and treated with one of the following: MSC alone administered intraperitoneally (NEC+MSC IP), HB-EGF and MSC administered intraperitoneally (NEC+HB-EGF+MSC IP), MSC alone administered intravenously (NEC+MSC IV), and HB-EGF and MSC administered intravenously (NEC+HB-EGF+MSC IV). 
       
    
    
     DETAILED DESCRIPTION 
       [0139]    The following examples illustrate the invention wherein Example 1 describes the neonatal rat model of experimental necrotizing enterocolitis. Example 2 describes a method of transplanting mesencymal stem cells. Example 3 demonstrates that HB-EGF protects enterocytes, goblet cells and neuroendocrine cells from NEC in vivo. Example 4 demonstrates that HB-EGF protects rat pup intestinal progenitor cells and stem cells from NEC in vivo. Example 5 demonstrates that HB-EGF protects prominin-1-positive ISCs from hypoxic stress in vivo. Example 6 demonstrates that HB-EGF promotes stem cell viability and growth of crypt-villous organoids ex vivo. Example 7 demonstrates that HB-EGF protects ex vivo crypt-villous organoids from hypoxic injury via EGFR activation and the MEK1/2 signaling pathway. Example 8 demonstrates that HB-EGF promotes MSC proliferation under normal and hypoxic conditions. Example 9 demonstrates that HB-EGF Induces MSC Migration. Example 10 demonstrates that HB-EGF Protects MSC from anoxia-induced apoptosis. 
       EXAMPLES 
     Example 1 
     Neonatal Rat Model of Experimental Necrotizing Enterocolitis 
       [0140]    The studies described herein utilize a neonatal rat model of experimental NEC. These experimental protocols were performed according to the guidelines for the ethical treatment of experimental animals and approved by the Institutional Animal Care and Use Committee of Nationwide Children&#39;s Hospital (#04203AR). Necrotizing enterocolitis was induced using a modification of the neonatal rat model of NEC initially described by Barlow et al. ( J Pediatr Surg  9:587-95, 1974). Pregnant time-dated Sprague-Dawley rats (Harlan Sprague-Dawley, Indianapolis, Ind.) were delivered by C-section under CO 2  anesthesia on day 21.5 of gestation. Newborn rats were placed in a neonatal incubator for temperature control. Neonatal rats were fed via gavage with a formula containing 15 g Similac 60/40 (Ross Pediatrics, Columbus, Ohio) in 75 mL Esbilac (Pet-Ag, New Hampshire, Ill.), a diet that provided 836.8 kJ/kg per day. Feeds were started at 0.1 mL every 4 hours beginning 2 hours after birth and advanced as tolerated up to a maximum of 0.4 mL per feeding by the fourth day of life. Animals were also exposed to a single dose of intragastric lipopolysaccharide (LPS; 2 mg/kg) 8 hours after birth, and were stressed by exposure to hypoxia (100% nitrogen for 1 minute) followed by hypothermia (4° C. for 10 minutes) twice a day beginning immediately after birth and continuing until the end of the experiment. In all experiments, pups were euthanized by cervical dislocation upon the development of any clinical signs of NEC. All remaining animals were sacrificed at the end of experiment at 96 hours after birth. 
         [0141]    The HB-EGF used in all experiments was GMP-grade human mature HB-EGF produced in  P. pastoris  yeast (KBI BioPharma, Inc., Durham, N.C.). EGF was produced in  E. coli  and purchased from Vybion, Inc. (Ithaca, N.Y.). 
         [0142]    To assess the histologic injury score, immediately upon sacrifice, the gastrointestinal tract was carefully removed and visually evaluated for typical signs of NEC including areas of bowel necrosis, intestinal hemorrhage and perforation. Three pieces each of duodenum, jejunum, ileum, and colon from every animal were fixed in 10% formalin for 24 hours, paraffin-embedded, sectioned at 5 μm thickness, and stained with hematoxylin and eosin for histological evaluation of the presence and/or degree of NEC using the NEC histologic injury scoring system described by Caplan et al. ( Pediatr Pathol  14:1017-28, 1994). Histological changes in the intestines were graded as follows: grade 0, no damage; grade 1, epithelial cell lifting or separation; grade 2, sloughing of epithelial cells to the mid villus level; grade 3, necrosis of the entire villus; and grade 4, transmural necrosis. All tissues were graded blindly by two independent observers. Tissues with histological scores of 2 or higher were designated as positive for NEC. 
         [0143]    Fisher&#39;s exact test was used for comparing the incidence of NEC between groups with no adjustments made for multiple comparisons. P-values less then 0.05 were considered statistically significant. All statistical analyses were performed using SAS, (version 9.1,SAS Institute, Cary, N.C.). 
       Example 2 
     Method of Transplanting Mesencymal Stem Cells 
     Culture of Murine Bone Marrow-Derived MSC, Characterization and Preparation for Injection 
       [0144]    Murine yellow fluorescence protein (YFP)-labeled bone marrow-derived mesencymal stem cells (YFP-BM-MSC) at passage 2 were initially derived as follows. A transgenic construct (pCX::EYFP) containing an enhanced YFP gene under the control of a chicken beta actin promoter coupled with the cytomegalovirus (CMV) immediate early enhancer, was introduced into (129×1/SvJ×129S1/Sv) F1-derived R1 mouse embryonic stem (ES) cells. The homozygotes (129-Tg (CAG-eYFP) 7AC5Nagya, http://jaxmice.jax.org/strain/005483.html) were used as the source of BM-MSC. Bone marrow was harvested from the femurs and tibias of hind limbs and suspended in Dulbecco&#39;s Modified Eagle Medium (D-MEM) Nutrient Mixture F-12/GlutaMAX-ITM medium (GIBCO Invitrogen; Carlsbad, Calif.). The cell mixture was pipetted and filtered through a cell strainer with 70 μm nylon mesh (Becton Dickinson; Franklin Lakes, N.J.), and seeded in DMEM Nutrient Mixture F-12/GlutaMAX-ITM medium supplemented with 10% MSC-qualified fetal bovine serum (FBS) (GIBCO, Grand Island, N.Y.) and 0.01% gentamicin (GIBCO, Grand Island, N.Y.) at 37° C. in 5% CO 2 . Culture medium was changed every 4 days and non-adherent cells removed. 
         [0145]    Prior to MSC injection, adherent cells were trypsinized (0.25% trypsin, Cellgro, Manassas, Va.) for 3 min and then D-MEM/F12/GlutaMAX-ITM medium supplemented with 10% MSC-qualified FBS was added to neutralize the trypsin. 
         [0146]    Cells were quantified using a hemacytometer and centrifuged at 800 rpm for 5 minutes at 4° C. Supernatants were discarded and pellets were resuspended in sterile saline. Suspended MSC were filtered through a cell strainer with 70 μm nylon mesh before injection. The concentration of MSC was adjusted to 7.5×10 6  cells/ml for injection. MSC suspensions were loaded into 0.3 ml low-dose U-100 insulin syringes with 29 gauge needles (Becton Dickinson; Franklin Lakes, N.J.). Prior to IV infusion, syringes were maintained at 4° C. with continuous shaking and MSC gently resuspended to ensure they were not aggregated prior to infusion. (Hall et al.,  Handb Exp Pharmacol.  2007:263-283) 
         [0147]    The stem cell characteristics of the murine BM-MSC were verified in vitro by their ability to differentiate into osteocytes and adipocytes in the presence of specific induction media for 15 days (Adipogenic and Osteogenic Differentiation kits, GIBCO Invitrogen, Grand Island, N.Y.). MSC cultured without adipogenic or osteocyte differentiation media were used as undifferentiated controls. MSC were able to differentiate into both osteocytes and adipocytes. Osteogenic differentiation was associated with extracellular precipitate stained with alizarin Red S (ph 4.2) corresponding to calcium deposits. Adipogenic differentiation was accompanied by the accumulation of lipid droplets stained by Oil-Red. Undifferentiated control cells had no staining with either alizarin Red S or Oil-Red. 
         [0148]    Cultured MSC had a spindle-like shape. As expected, all MSC had YFP expression. Vimentin is the main intermediate filament protein in mesenchymal cells and is therefore considered as a positive marker for MSC. Vimentin immunocytochemistry was performed as follows: cultured MSC were fixed in 4% paraformaldehyde (USB Corporation; Cleveland, Ohio) at 4° C. for 20 minutes and rinsed in phosphate-buffered saline (PBS) (Cellgro, Manassas, Va.) three times. Cells were then incubated with mouse anti-Vimentin monoclonal antibody at a 1:50 dilution (Thermo Scientific; IL, USA; http://thermoscientific.com/ab) for 2 hours at room temperature, rinsed with PBS three times, and incubated with Cy3 labeled donkey anti-mouse antibody at a 1:500 dilution (Jackson ImmunoResearch, West Grove, Pa.) for 1 hour at room temperature. Counterstaining of nuclei was accomplished using 4′,6-Diamidino-2-Phenylindole Dihydrochloride (DAPI). Fluorescence was observed under a fluorescent microscope (Axioscope, Carl Zeiss; Jena, Germany) using green fluorescence protein (GFP), Cy3 and DAPI channels. All MSC were positive for Vimentin expression. 
       Injection 
       [0149]    Sprague-Dawley pups on day 21 of gestation were delivered via Cesarean section (C-section). After delivery, placentas were kept moist and warm, and the integrity of the umbilical cords maintained for injection. The premature newborn rats (average weight 5.2 g) were placed in a neonatal incubator for temperature control. For intravenous (IV) cannulation and infusion of MSC, the newborn rat pups were anesthetized immediately following C-section with inhalational isofluorane in 4% O 2 . The placenta was placed on a gauze pad and the umbilical cord straightened for exposure. Under a surgical dissecting microscope, the membrane covering the umbilical vein and arteries was dissected and the vein separated from the arteries. A fine toothed forceps was placed beneath the exposed umbilical vein. An oblique incision (˜1.5 mm) was made in the umbilical vein and the vein was flushed with saline. One end of the tip of a piece of polyethylene-10 (PE-10) tubing (Becton Dickinson, Sparks, Md.) was slightly stretched to make it thinner, and the other end of the tubing was fitted onto the needle of the syringe holding the MSC suspension. Using sterile technique, the stretched end of the tube was cannulated into the umbilical vein and the tube was fixed with an atraumatic vessel clip. A total volume of 40 μl containing 300×10 3  MSC was infused through the umbilical vein of rat pups (N=83). MSC suspensions were injected within 1 minute of cannulation. Rat pups receiving the same volume of IV saline injection were used as control animals (N=11). Injections that drove blood in the umbilical vein back to the circulation were considered to be successful. Fluid extravasation, umbilical vein rupture, resistance while injecting or obstruction of umbilical veins were considered to be signs of injection failure. Mean operating time for each successful cannulation and injection was recorded. 
         [0150]    All umbilical vein injections were performed by the same operator. The first 3 injections had an operating time of ˜8 minutes each, and injection failed in two of the pups due to umbilical vein rupture. After the first 3 pups, the operating time decreased to 2.5-5.5 minutes per pup (mean operating time 3.9 min ±1.1 minutes), and the injection success rate was 92.8% (77 out of 83). 
         [0151]    Upon injecting methylene blue dye, the dye entered the umbilical vein. The skin of rat pups was pink prior to methylene blue injection. Blue discoloration of the skin was noted immediately after injection in the order of chest, head, abdomen and paws. The internal aspect of the umbilical vein stained blue upon injection of the dye. Bluish discoloration of the intestines was noted about 5 seconds after dye injection. 
         [0152]    In vivo cardiac structures were identified using a VisualSonics Vevo 2100 with a 40 MHz transducer (Visualsonics, Toronto, Ontario). After umbilical vein cannulation, rat pups were moved to a heated procedure board. Next, pre-warmed ultrasound gel (Aquasonic, Parker Labs, Farifield, N.J.) was placed on the chest and a 15 MHz probe (optimized and dedicated to rodent studies) was placed in a subcostal orientation and a four chamber apical view was obtained. After obtaining the four chamber view, the patent foramen ovale (PFO) was visualized. Subsequently, the sample volume was injected to the level of the PFO and pulsed wave. Doppler was used to capture baseline shunt flow. When injecting MSC suspensions, extra waves and changes of wave shapes were recorded. The Doppler ultrasound imaging demonstrated a patent foramen ovale (PFO) with right to left shunting between the atria. At the site of the PFO, pulse-wave ultrasound scanning showed baseline pulse-waves with right-to-left shunting prior to IV MSC injection. During the injection of MSC, an extra wave was detected representing the extra blood flow through the PFO. After injection, the waves following the extra wave had a longer wavelength and higher wave peak compared to the waves at baseline, indicating a higher speed of blood flow upon injection. 
         [0000]    Mortality after IV MSC Administration in Adult Mice and Newborn Rat Pups 
         [0153]    In an effort to compare IV MSC infusion in adult animals compared to newborn animals, we chose to use adult mice since their bodyweight was ˜5 times that of newborn rats, as opposed to using adult rats which would have a bodyweight of about 50 times that of newborn rats. FVB mice (12 weeks of age) were anesthetized with inhalational isofluorane in 4% O 2  and 100 μl of a suspension of 1×10 6  MSC was infused with a 28 gauge needle through the tail vein using a dissecting microscope. This concentration of MSC was calculated to be comparable to the concentration of MSC administered to rat pups based on body weight. Mice receiving saline injection served as negative controls. 
         [0154]    Immediately after IV MSC infusion, the mortality in adult mice was 21.7%, however, the mortality in premature rat pups was significantly decreased (6.43%, p=0.047). Within 24 hours, the cumulative mortality in adult mice was 47.8%, whereas the cumulative mortality in rat pups was significantly less (23.4%, p=0.0352). No control animals receiving saline injection died. 
       YFP-MSC Engraftment in Lungs, Heart and Intestines 
       [0155]    After 96 hours, 11 of the rat pups that received systemic MSC administration and 11 control rat pups that received saline injections were euthanized by carbon dioxide asphyxiation followed by exsanguination. Lungs, hearts and intestines were harvested and fixed in fixation solution containing 1% paraformaldehyde, 15% picric acid, and 0.1 M sodium phosphate buffer (pH 7.0) and shaken gently at 4° C. overnight. Samples were embedded in Tissue-Tek Optimal Cutting Temperature (OCT) (Sakura Finetek, Torrance, Calif.) compound and frozen sections (10 μm) made. Slides were washed with PBS three times and mounted with Vectashield mounting medium for fluorescence with DAPI (Vector Laboratories, Burlingame, Calif.). Fluorescence was observed under a fluorescence microscope (Axioscope, Carl Zeiss; Jena, Germany) using GFP and DAPI channels. Quantification of MSC was performed by counting YFP-positive cells per visual field at 100× magnification. 
         [0156]    As expected, negative control rat pups receiving saline injection only had no YFP positive MSC in the lungs, heart or intestines. YFP-MSC were identified in these organs after IV MSC administration. Quantification of YFP-MSC engraftment revealed 15.8±4.1 cells per visual field in the lungs, 2.9±1.2 cells per visual field in the heart, and 19.8±5.0 cells per visual field in the intestines. 
         [0157]    In addition, frozen sections of OCT-embedded intestines were prepared and sections were rinsed in PBS three times, incubated with mouse anti-Vimentin monoclonal antibody (Thermo Scientific;IL, USA) overnight at 4° C., rinsed with PBS three times again, and incubated with Cy3 labeled donkey anti mouse antibody for 1 hour at room temperature. Fluorescence was observed under a fluorescent microscope (Axioscope, Carl Zeiss; Jena, Germany) using GFP and Cy3 channels at 400× magnificationYFP positive MSC were noted in the mucosal layer of the villi. Vimentin expression co-localized with YFP expression in MSC. 
       Example 3 
     HB-EGF Protects Enterocytes, Goblet Cells and Neuroendocrine Cells from NEC in vivo 
       [0158]    HB-EGF protects enterocytes, goblet cells and neuroendocrine cells from injury induced by experimental NEC in vivo (as described in Example 1). In particular, pups (n=10), designated as the NEC group, were exposed to hypoxia with 100% nitrogen for 1 minute followed by hypothermia at 4° C. for 10 minutes twice daily beginning 60 minutes after birth for either 1, 2 or 3 days, with intragastric feeding of lipopolysaccharide (LPS) (2 mg/kg) 8 hours after birth. LPS administration enhanced the incidence of NEC in our model and has been used by others as well. (Cetin et al.,  J Biol Chem  2004; 279:24592-24600) Pups were euthanized by cervical dislocation on the development of any clinical signs of NEC, or at the end of the experiment at 3 days after birth. Additional pups (n=10), designated as the NEC+HB-EGF group, were stressed for 3 days, but were treated with HB-EGF (800 mg/kg per dose) added to each feed beginning with the first feed received after birth. Control pups (n=5), designated as the breast milk (BM) group, were breast fed for 3 days using surrogate mothers (since their natural mothers were killed after C-section), and were not stressed. 
         [0159]    The recombinant human HB-EGF used in the current experiments, corresponding to amino acids 74-148 of the mature HB-EGF precursor, was produced using a  Pichia pastoris  expression system according to Good Laboratory Practice procedures (Trillium Therapeutics, Toronto, Canada). 
         [0160]    Intestines were removed on killing and fixed in 10% formalin for 24 h. Four pieces each of duodenum, jejunum, ileum and colon were harvested, paraffin-embedded, sectioned at 5 mm thickness, and stained with hematoxylin and eosin. Intestinal injury was graded by examining tissue sections with phase contrast microscopy using the histological scoring system described by Caplan et al. ( Pediatr Pathol  1994; 14: 1017-1028) Intestinal morphologic changes were graded as: grade 0, no damage; grade 1, epithelial cell lifting or separation; grade 2, necrosis to the mid villous level; grade 3, necrosis of the entire villus; and grade 4, transmural necrosis. Histological injury scores of grade 2 or greater were considered positive for NEC. Grading was carried out blindly by two experienced independent observers. 
         [0161]    Rat pup jejunal cross-sections (5 mm thickness) were subjected to histochemical and immunohistochemical staining for detection of IEC lineages. Enterocytes were identified by H&amp;E staining of tissue sections. H&amp;E stained sections were examined using an Axioscope microscope (HBO 100/W2, Zeiss, Thornwood, N.Y., USA) with bright field photo-documentation using AxioVision software (version, 02.2002). Enterocytes in villi were manually identified and marked and then numerically counted using the Cell Counter in ImageJ software (version 1.39U, NIH, Bethesda, Md., USA). Goblet cells were identified by periodic acid-Schiff (PAS) staining of tissue sections. For neuroendocrine cells, immunofluorescent staining was performed for the detection of chromogranin-A-positive neuroendocrine cells using rabbit polyclonal anti-chromogranin-A (v:v¼1:500) (ABCAM, Cambridge, Mass., USA) primary antibodies. Paneth cells in the intervillous regions, tissue sections were also subjected to a-defensin immunostaining using goat polyclonal anti-a-defensin (R-19) (Santa Cruz Biotechnology, Santa Cruz, Calif., USA) primary antibodies in an attempt to identify Paneth cells. 
         [0162]    Enterocytes/villous in breast fed control rat pups (BM group) were decreased significantly in pups with experimental NEC (NEC group), and increased significantly in pups with experimental NEC that were treated with HB-EGF added to the feeds (NEC+HB-EGF group). Similar results were found for goblet cells and neuroendocrine cells. No Paneth cells were detectable in the intervillous regions of newborn rat pups using either H&amp;E staining or anti-α-defensin immunostaining. 
       Example 4 
     HB-EGF Protects Rat Pup Intestinal Progenitor Cells and Stem Cells from NEC In Vivo 
       [0163]    PCNA immunostaining was used to identify proliferating ISCs and TA progenitor cells in the intervillous regions of rat pup intestines. Mouse anti-proliferating cell nuclear antigen (PCNA) (Sigma-Aldrich, St Louis, Mo., USA) primary antibodies were used as described in Trahair et al. ( J Pediatr Gastroenterol Nutr  1986; 5:648-654.25). ISCs were further identified by immunostaining using rabbit anti-LGR5 (v:v=1:500) (MBL International Corporation, Woburn, Mass., USA) and rat monoclonal anti-prominin-1 (v:v=1:10) (Miltenyi Biotec, Auburn, Calif., USA). The HB-EGF treated rats are described in Example 3. 
         [0164]    The PCNA antibodies labeled most of the intervillous epithelial cell nuclei in breast fed rat pups, indicating intense proliferation of these cells. PCNA immunostaining was markedly reduced in pups subjected to NEC. Importantly, pups subjected to NEC but treated with HB-EGF added to the feeds had significantly increased intervillous PCNA immunostaining compared with non-HBEGF-treated pups. These findings show that HB-EGF is able to protect stem cells/TA progenitor cells from experimental NEC. 
         [0165]    LGR5 and prominin-1 are both known to be expressed in ISCs, and therefore expression of LGR5 and prominin-1 in ISC was analyzed. Under basal, non-injury conditions, double immunostaining with monoclonal anti-prominin-1 and anti-LGR5 antibodies successfully identified rat pup ISCs. Prominin-1 expression in rat pup intervillous epithelial cells colocalized with LGR5 expression specific to stem cells, but not to TA progenitor cells. Confocal serial scanning confirmed that prominin-1 and LGR5 staining was both intracellular and cell membrane associated. Some villous and mesenchymal cells stained positively, as has been described. (Barker et al.,  Nature  2007; 449:1003-1007). 
         [0166]    The effect of HB-EGF on ISCs in the animal model of experimental NEC (described in examples 1 and 3) was analyzed. The number of stem cells/intervillous region decreased significantly in pups subjected to NEC, and increased significantly in pups subjected to NEC but with HB-EGF added to the feeds. Thus, HB-EGF protects ISCs from injury in a model of experimental NEC. The decreased LGR5 expression in ISCs was also observed in human intestine resected for NEC compared with human intestine resected for small bowel atresia. 
       Example 5 
     HB-EGF Protects Prominin-1-Positive ISCs from Hypoxic Stress In Vitro 
       [0167]    An in vitro model was used to further investigate the cytoprotective effects of HB-EGF on ISCs. Magnetic-activated cell sorting (MACS) isolation of prominin-1+ ISCs was performed with modifications of a previously described method. (Sato et al.,  Nature  2009; 459:262-265, Yu et al.,  Biotechnol Lett  2004; 26:1131-1136). 
         [0168]    In particular, small intestines were excised from 6 to 10 neonatal rat pups at 3 days of age for isolation of intestinal progenitor and stem cells. Intestines were opened longitudinally, washed with cold PBS and cut into 5 mm pieces. Tissue fragments were incubated in 2 mM EDTA/PBS for 30 minutes on ice. Intervillous epithelia were enriched and centrifuged at 150-200 g for 3 minutes as described previously (Sato et al.,  Nature  2009; 459:262-265) and dissociated by incubation in PBS supplemented with trypsin (10 mg/ml) and DNase (0.8 m/ml) for 30 minutes at 37° C. (Dekaney et al.,  Gastroenterology  2005; 129:1567-1580) Single cells were centrifuged at 300 g for 10 minutes at 4° C., resuspended in minimum essential medium and filtered through 40 mm cell strainers. Strained cells were washed with 10 ml of cold PBS and centrifuged at 300 g for 10 minutes at 4° C. The isolation of prominin-1-positive stem cells was carried out according to the manufacturer&#39;s protocol (Miltenyi Biotec) as follows. Dissociated intervillous epithelial cells were resuspended in 80 ml PBS/BSA/EDTA buffer (pH 7.2, 0.5% BSA and 2 mM EDTA) per 107 total cells. Twenty ml of anti-Prominin-1 MicroBeads (Miltenyi Biotec) per 107 total cells were added and incubated for 10 minutes on ice. Cells were washed with 1-2 ml of buffer per 10 7  cells and centrifuged at 300 g for 10 minutes. Supernatants were removed and B108 cells were suspended in 500 ml of PBS/BSA/EDTA buffer and run through MACS pre-separation filters to remove clumped cells. MACS separation columns were placed in a magnetic multistand and rinsed with 2 ml PBS/BSA/EDTA buffer. Filtered cell suspensions were applied to the columns, the columns were washed two times with 2 ml PBS/BSA/EDTA buffer, and flow through collected as controls. The retained prominin-1-positive cells were harvested by removing the column from the magnetic multistand, and eluting the cells into collection tubes using 2 ml PBS/BSA/EDTA buffer. To monitor the purification efficiency, portions of run through and retained cells were centrifuged at 300 g at 4° C. and fixed in methanol/acetone (v:v=1:1) for 30 minutes. After three washes with PBS buffer, cells were subjected to anti-prominin-1 antibody immunostaining. Prominin-1-positive stem cells were maintained in medium (high-glucose Dulbecco&#39;s modified Eagle&#39;s medium (DMEM) with 10% FBS, 10 mg/ml insulin, 2 mM glutamine, 100 U/ml penicillin and 100 mg/ml streptomycin) at 37° C. in an incubator with 5% CO 2  until hypoxia experiments were carried out. 
         [0169]    Additional experiments were designed to confirm that prominin-1 MACS enriches for ISC. MACS isolated cells were labeled either with anti-Prominin-1 and Cy3-conjugated secondary antibody or with anti-LGR5 and FITC conjugated secondary antibody, and then subjected to flow cytometry analysis (BD LSR II; BD Biosciences, San Jose, Calif. with 30 000 events recorded. Appropriate controls were labeled with secondary antibodies conjugated with Cy3 or FITC alone. 
         [0170]    Colocalized prominin-1 and LGR5 expression in ISCs in vivo supported isolation of ISCs by prominin-1 MACS. Intervillous epithelia were separated from the villi and prominin-1-positive cells were enriched by prominin-1 antibody MACS. Prominin-1 and LGR5 immunostaining confirmed about 90% positively stained cells in MACS eluates compared with about 10% in the flow through. Flow cytometry confirmed that about 80% of the MACS purified cells expressed prominin-1 and LGR5. In the absence of HB-EGF, exposure of ISCs to hypoxia led to decreased cell viability. However, addition of HB-EGF to ISCs exposed to hypoxia led to significantly increased ISC viability. Furthermore, under normoxic conditions, addition of HB-EGF also led to increased ISC viability. 
       Example 6 
     HB-EGF Promotes Stem Cell Viability and Growth of Crypt-Villous Organoids Ex Vivo 
       [0171]    The effects of HB-EGF on crypt-villous organoid growth ex vivo, under basal, non-injury conditions were analyzed. The ex vivo crypt-villous organoid culture system as described by Sato et al (Nature 2009; 459:262-265) was modified using R-spondin 1 and Nogginin the culture medium, but replacing EGF with HB-EGF. 
         [0172]    To isolate the crypts, C57BL/6J 3-month-old mice were killed and the intestines removed. Crypt isolation was carried out using a modification of the method described by Bjerknes et al. ( Anat Rec  1981; 199:565-574) The distal half of the jejunum and the entire ileum were excised and intestinal contents were removed by flushing with ice-cold Ca 2+ - and Mg 2+ -free PBS. The intestine was reverted on a 4 mm glass rod and exposed to PBS/EDTA (30 mM) (pH 7.4), at 37° C. for 5 minutes. To release villi into ice-cold PBS, intestines on glass rods were assembled unto a Bulcher gradient maker and subjected to 4-5 pulses of vibration. Sheets of crypts were then rapidly vibrated off the intestine into new ice-cold PBS after a further 15-minute incubation in PBS/EDTA (30 mM) (pH 7.4), at 37° C. Crypts were separated from remnant villi by gentle pipetting up and down with 10 ml serum tubes followed by filtering through 70 mm cell strainers. Crypts were centrifuged at 100-150 g and were resuspended in cold PBS buffer. Crypts were quantified using hemocytometry with Trypan blue (1:10 dilution) (Invitrogen). 
         [0173]    Crypt-villous organoid cultures were established according to the methodology described by Sato et al. ( Nature  2009; 459:262-265) The concentration of isolated crypts was evaluated by counting the total number of crypts in 100 ml PBS microscopically. In all, B500 crypts plus 50 ml of BD Matrigel basement membrane matrix (BD Biosciences) were mixed and seeded in 24-well plates. When gels polymerized at room temperature, 500 ml of crypt culture medium (advanced DMEM/F12) (Invitrogen) containing EGF (50 ng/ml) (Peprotech, Rocky Hill, N.J.) or HB-EGF (50 ng/ml) (Trillium Therapeutics), plus the Wnt agonist R-spondin 1 (500 ng/ml) (R&amp;D Systems, Minneapolis, Minn.) and the BMP inhibitor Noggin (100 ng/ml) (Peprotech) were used to maintain crypt-villous organoid growth. In order to further examine the requirements for organoid growth, HB-EGF, R-spondin 1 or Noggin, alone or in various combinations, were added and replaced every three days. Crypt cultures were maintained at 37° C. in an incubator with 5% CO 2  and the percentage of crypts growing into crypt-villous organoids were evaluated at days 1, 3 and 5. Crypt-villous organoids were released from matrigel using recovery buffer (BD Biosciences) on ice for 30 minutes and washed in 1×PBS three times before fixation in 4% paraformaldehy/PBS for 2 hours. Orgnoids were penetrated using 0.1% Tween 20/PBS for immunostaining. Some organoids were embedded in histogel (Lab Storage System, St Peters, Mo., USA) and fixed again in 10% formalin/PBS before paraffin embedding and sectioning. Organoid tissue sections were subjected to cell lineage identification using H&amp;E, immunohistologic and PAS staining. 
         [0174]    Ex vivo crypt-villous organoids were analyzed as follows. Crypt-villous organoid viability in each culture well was expressed as the percentage of viable organoids after scoring of at least 50 organoids. Organoid size was determined by microscopic visualization of 15 crypt-villous organoids at x5 magnification using a LEICA DM-4000B microscope, with organoid size expressed in relative area units obtained using ImageJ software (version 1.39U, NIH). Crypt length was quantified similarly and expressed as relative length units. The total number of crypts in each crypt-villous organoid was also determined. A relative unit is a pixel unit designated by ImageJ software when a certain length or area was measured. 
         [0175]    The crypts grew into crypt-villous organoids with a villous sphere and numerous budding crypts. The growth of crypt-villous organoids from the cryptal base was exponential during the 12-day culture period. Cultured organoids were designated as either viable or degraded. The addition of R-spondin 1 alone was essential for maintenance of viable organoids, and was able to sustain organoids up to day 4. With either HBEGF alone or Noggin alone, crypts were initially viable at 12 hours in culture, but viability dropped dramatically by days 1-2 and was completely lost by day 4 in culture. The addition of Noggin to R-spondin 1 did not increase the percentage of viable organoids, suggesting that Noggin may not be essential for maintaining organoids, although it may be necessary for further passage of ex vivo organoid cultures. However, addition of HB-EGF to R-spondin 1 and Noggin significantly increased organoid viability, organoid size, and crypt fission and crypt length. Together, these results indicate that HB-EGF enhances R-spondin 1-induced ISC activation and proliferation, resulting in increased organoid growth under basal, non-injury conditions. 
       Example 7 
     HB-EGF Protects Ex Vivo Crypt-Villous Organoids from Hypoxic Injury Via EGFR Activation and the MEK1/2 Signaling Pathway 
       [0176]    To investigate the effects of HB-EGF on ISC survival and proliferation on exposure to injury, the sizes and the percentage of viable organoids were quantified in ex vivo crypt-villous organoid cultures exposed to normoxia or hypoxia for 60 minutes. MACS-isolated prominin-1-positive cells (10 4 ) were seeded in 96-well plates in triplicate and incubated overnight. Cells were subjected to hypoxia (100% nitrogen) or to normoxia for 60 minutes in the presence or absence of HB-EGF (100 ng/ml) that was added 1 hour before the initiation of hypoxia. Stem cell viability was evaluated 24 hours post hypoxia using the Cyquant cell proliferation assay kit (Invitrogen, Eugene, Oreg., USA), normalized to the viability of the normoxic control without HB-EGF, which was designated as 100%. Ex vivo crypt-villous organoids were cultured overnight and subjected to hypoxia (100% nitrogen) or to normoxia for 60 minutes, in the presence or absence of HB-EGF (50 ng/ml) that was added 12 hours before hypoxia. Each treatment was performed in triplicate. Crypt viability in 50 crypts was examined on days 1-5 after hypoxia, with determination of the percentage of crypts that formed crypt-villous organoids. The size of crypt-villous organoids exposed to different treatments at days 1-5 of culture was normalized to the size of crypt-villous organoids exposed to normoxia for 1 day. The methods to analyze the crypt-villous organoids are described in Example 6. 
         [0177]    In the absence of HB-EGF, organoid size remained static under normoxic or hypoxic conditions at all-time points tested. However, crypt-villous organoid growth in the presence of HB-EGF was significantly increased at 3 and 5 days after exposure to either hypoxia or normoxia. HB-EGF significantly increased the percentage of viable organoids at days 1,2 and 3 under normoxic conditions, and at day 3 on exposure to hypoxia. This indicates that HB-EGF protects ISCs from hypoxic injury and promotes ISC proliferation even under hypoxic conditions. 
         [0178]    Signal pathway inhibitor studies suggested that HB-EGF promotes crypt-villous organoid proliferation via activation of EGFR/MEK1/2 and PI3K/Akt signaling pathways. In the absence of inhibitors, crypts grew into crypt-villous organoids in the presence of HB-EGF beginning at day 1. In the presence of specific inhibitors to EGFR, PI3K or MEK1/2 signaling, organoid size and viability (were significantly decreased. Organoids cultured in the presence of HB-EGF and the MEK1/2 inhibitor were composed of a cellular sphere with none to few shortened protruding crypts similar to organoids grown without HB-EGF. Organoids cultured in the presence of HB-EGF and the EGFR inhibitor or the PI3K inhibitor suffered more severe consequences. Under these conditions, organoids stopped growing by day 1, and were completely degraded into debris by days 2-5. These findings were similar under either normoxic or hypoxic conditions. 
       Example 8 
     HB-EGF Promotes Mesenchymal Stem Cell Proliferation Under Normal and Hypoxic Conditions 
       [0179]    Bone marrow-derived mesencymal stem cells (BM-MSC) were harvested from adult pan-EGFP C57/BL6 mice following previously described protocols (Phinney et al.,  J Cell Biochem  1999; 72(4):570-85). Briefly, mice were euthanized by cervical dislocation, and the femurs and tibias were removed and dissected free of surrounding tissue using sterile technique. The marrow was flushed out with 2 ml of phosphate-buffered saline (PBS) using a sterile syringe and 20 gauge needle. The marrow pellet was dispersed by gentle pipetting and transferred to uncoated cell culture flasks. 
         [0180]    Amniotic fluid was obtained via amniocentesis of pan-EGFP C57/BL6 mice using an adaptation of techniques previously described in Baghaban et al.,  Arch Iran Med.  14(2): 96-103, 2011. Female mice at 12.5 days gestation were anesthetized with 2.5% tribromoethanol via intraperitoneal (IP) injection. The abdominal skin was shaved and scrubbed with 70% ethanol. A midline laparotomy was performed and the gravid uterus identified. The uterus was opened and amniocentesis performed under direct vision of the individual placentas using a 23 gauge needle. Amniotic fluid samples were transferred to uncoated cell culture flasks. 
         [0181]    After harvesting, AF-MSC and BM-MSC were cultured in Dulbecco&#39;s modified Eagle&#39;s medium: Nutrient Mixture F-12 with GlutaMax (DMEM/F12; Invitrogen, Carlsbad, Calif.) supplemented with 10% MSC Qualified Fetal Bovine Serum (FBS; Invitrogen, Carlsbad, Calif.) and gentamycin (5 μg/ml) (Invitrogen, Carlsbad, Calif.) in uncoated cell culture flasks at 37° C. in a humidified atmosphere of 5% CO 2 /95% Nitrogen. After 24 hours, non-adherent cells were washed away with PBS and discarded. Adherent MSC were purified and expanded during successive passages. MSC were passaged once they achieved 80% confluence to expand the primary cultures. MSC from passages four through nine were used for all experiments. 
         [0182]    Differentiation assays were used to confirm pluripotency of MSC using the STEMPRO Adipogenesis Differentiation Kit (Invitrogen, Carlsbad, Calif.) and the STEMPRO Osteogenesis Differentiation Kit (Invitrogen, Carlsbad, Calif.) according to the manufacturer&#39;s instructions. Briefly, MSC were incubated in 12-well plates at 37° C. in a humidified atmosphere of 5% CO 2 /95% air, and grown in adipogenic or osteogenic differentiation media for 14 days. MSC grown in adipogenic differentiation media were then stained with Oil Red O to confirm adipogenic differentiation, and MSC grown in osteogenic differentiation media were stained with alkaline phosphatase to confirm osteogenic differentiation. Visual microscopic evaluation confirmed terminal differentiation into the adipocyte and osteocyte lineages. 
         [0183]    MSC proliferation was measured using CyQUANT Cell Proliferation Assay Kit (Molecular Probes, Eugene, Oreg.) according to the manufacturer&#39;s instructions. Briefly, MSC (4000 cells per well) were plated for 24 hours in 96-well plates. HB-EGF was then added at various concentrations (0, 5, 10, 25, 50, 100) and 1 hour later cells were cultured under either normoxic conditions or with exposure to anoxia (95% N2/5% CO 2 ) for 24 h followed by re-oxygenation for 24 hour at 37° C. Media was removed, dye binding solution was added to each well, and plates were incubated for 1 hour at room temperature. Results were quantified using a fluorescence plate reader (Molecular Devices, Sunnyvale, Calif.) using a 485/530 nm filter set. Fluorescent counts for the HB-EGF (0 ng/ml) group was normalized to 100%, with counts in the HB-EGF-treated groups compared to this standard. 
         [0184]    Under normoxic conditions HB-EGF significantly stimulated both AF-MSC and BM-MSC proliferation over a range of HB-EGF doses from 5-100 ng/ml. HB-EGF had a significantly greater proliferative effect on AF-MSC compared with BM-MSC over the entire range of HB-EGF doses. Upon exposure to anoxia/reoxygenation, HB-EGF stimulated AF-MSC proliferation at the same doses, and BM-MSC proliferation at slightly higher doses (10-100 ng/ml). The proliferation observed for AF-MSC under normoxic conditions was the most robust of all conditions tested. 
       Example 9 
     HB-EGF Induces MSC Migration 
       [0185]    MSC migration was assessed using the CHEMICON QCM Cell Migration Assay Kit (Millipore, Billerica, Mass.) according to the manufacturer&#39;s instructions. Briefly, 0.5×10 6  MSC/ml in serum-free media were placed in the inner wells of the migration chambers and HB-EGF at various concentrations (0, 5, 10, 25, 50, 100 ng/ml) in serum-free media was placed in the outer wells of the chambers, with incubation at 37° C. for 24 hour. Media was then removed, lysis buffer/dye solution was added to each well, and plates were incubated for 15 min at RT. Results were quantified using a fluorescence plate reader (Molecular Devices, Sunnyvale, Calif.) using a 490/520 nm filter set. Fluorescent counts for the HB-EGF (0 ng/ml) group was normalized to 100%, with counts in the HB-EGF-treated groups compared to this standard. 
         [0186]    AF-MSC and BM-MSC had increased migration in response to HB-EGF over a range of HB-EGF doses from 5-100 ng/ml. The chemotactic effect of HB-EGF was comparable in AF-MSC and BM-MSC. 
       Example 10 
     HB-EGF Protects MSC from Anoxia-Induced Apoptosis 
       [0187]    MSC apoptosis was assessed using caspase-3 immunohistochemistry (IHC). MSC were seeded on cover slips in 12-well plates in the growth media described above and allowed to adhere for 24 hours. MSC were treated with HB-EGF at various concentrations (0, 5, 10, 25, 50, 100 ng/ml), and 1 hour later were stressed by exposure to anoxia (95% N2/5% CO 2 ) for 24 hours followed by 24 hours of re-oxygenation at 37° C. MSC were then washed with sterile PBS with 0.1% Tween 20 (PBS/Tween), fixed with 4% paraformaldehyde in PBS at room temperature for 20 minutes, washed with PBS/Tween, and blocked with 10% goat serum in PBS/Tween for 1 hour at room temperature. MSC were then incubated overnight at 4° C. with rabbit anti-cleaved-caspase 3 antibody (Cell Signaling Technology, Danvers, Mass.) at a 1:100 dilution. After washing with PBS/Tween, MSC were incubated for 1 hour at room temperature with Cy3 AffiniPure Goat Anti-Rabbit IgG (H+L) (Jackson Immuno Research, West Grove, Pa.) at a 1:500 dilution. MSC were then washed, counterstained with DAPI and visualized using a Zeiss Axioskip fluorescent microscope (Carl Zeiss, New York, N.Y.). Five random fields were counted per well in two separate experiments to quantify the ratio of apoptotic cells to total cells. 
         [0188]    Under normoxic conditions, the percentage of apoptotic cells was 2.1% for AF-MSC and 1.7% for BM-MSC. Following exposure to anoxia for 24 hours followed by re-oxygenation for 24 hours, AF-MSC apoptosis increased to 7.2% and BM-MSC apoptosis increased to 9.6%. Addition of HB-EGF protected both AF-MSC and BM-MSC from anoxia-induced apoptosis in a dose-dependent fashion. At lower doses of HB-EGF (5 ng/ml and 10 ng/ml), there was significantly decreased apoptosis in the AF-MSC group compared with the BM-MSC group. 
       Example 11 
     HB-EGF and MSC Promote Survival in NEC 
       [0189]    The effect of HB-EGF and MSC administered concurrently in the animal model of necrotizing enterocolitis described in Examples 1 and 3 was investigated. HB-EGF was administered enterally by addition to the feeds as described above and mesenchymal stem cells (5×10 4  cells diluted in PBS per pup) were administered either intraperitoneally or intravenously immediately after birth. Survival was determined as the number of remaining pups at 14 days of life. 
         [0190]    All of the breast fed pups survived while there was a significantly decrease in survival in pups exposed to experimental NEC. Pups treated with either HB-EGF alone or MSC delivered IP or IV alone had improved survival, with the best survival seen in pups treated with both HB-EGF and intravenously administered MSC. These results are provided in  FIG. 1 . 
         [0191]    In addition to survival, the effect of the treatment with HB-EGF and MSCs on the incidence of severe grade 3 and 4 NEC was investigated. The histologic injury score was used to determine severity as described in Example 1. As shown in  FIG. 2 , the combination of HB-EGF and MSC administered intravenously resulted in the lowest incidence of severe NEC. In particular, the breast fed pups had no intestinal injury and the pups exposed to NEC had the highest incidence of severe intestinal injury. Upon treatment with either HB-EGF alone, MSC alone administered intravenously, or MSC alone administered intraperitoneally, the severity of intestinal injury decreased. However, when pups were exposed to NEC but treated with HB-EGF in combination with intraperitoneal or intravenous MSC, there was a further decrease in severe NEC, with the lowest incidence of severe NEC seen in pups treated with HB-EGF plus intravenous administration of mesenchymal stem cells. 
         [0192]    The engraftment of the MSC administered in conjunction with HB-EGF in the intestine was quantified. The administered MSC were fluorescently labeled, which allowed for the number of labeled cells/crypt/villous axis to be visually counted. As shown in  FIG. 3 , administration of HB-EGF led to significant increase in engraftment of the intraperitoneal or intravenous administered MSC. 
         [0193]    In addition, mucosal permeability was determined by measuring serum levels of FITC-labeled dextran that was administered enterally to the pups treated as described above. Very low intestinal permeability was seen in the breast fed pups, and the permeability significantly increased in the pups exposed to NEC. The pups in all experimental groupshad significantly decreased intestinal permeability with the best gut barrier function found in pups exposed to NEC but treated with HB-EGF plus intravenous administered MSC.