Tissue-engineered small intestine improves recovery after massive small bowel resection.

Short bowel syndrome (SBS) includes a broad diversity of metabolic and physiologic disturbances, including fluid, nutrient, and weight loss secondary to unavailable functional surface area.1 Calcium, magnesium, zinc, iron, B12, and fat-soluble vitamin deficiencies are complicated by decreased absorption of carbohydrates and protein, which are linked as well to metabolic acidosis, formation of biliary and renal calculi, dehydration, and weight loss.2 SBS generally occurs with loss of approximately 70% to 75% of the small intestine.3–5 The severity of SBS is linked to the extent of resection, presence of an ileocecal valve, and presence of jejunum,2 as well as the health of the remaining small bowel.4 Our laboratory first reported making tissue-engineered small intestine (TESI) by the transplantation of organoid units on a polymer scaffold into the omentum of the Lewis rat.6 Organoid units are multicellular units derived from neonatal rat intestine, containing a mesenchymal core surrounded by a polarized intestinal epithelium, and contain all of the cells of a full-thickness intestinal section.7 We have recently transformed this protocol to yield significantly more organoid units in a shorter time from more specific areas of the gastrointestinal tract, beginning with the sigmoid colon as reported in this journal,8 leading to a greater viability, as production of tissue-engineered colon (TEC) occurs 100% of the time from autologous tissue, syngeneic tissue, or TEC itself. We have generated specific areas of the entire gastrointestinal tract including the abdominal esophagus,9 stomach,10 gastroesophageal junction,10 ileum and jejunum, and portions of the colon (Fig. 1). The sigmoid colon alone, harvested and grown into TEC and used in a replacement model, demonstrates resilient architecture, sodium and water absorption, short-chain fatty acid production, and ganglion cells.11 In the case of TEC, the model in which much of the protocol refinement was done, the histology has improved to be indistinguishable in some cases from native colon with an appropriate epithelial layer, actin-positive muscularis propria containing S100-positive cells in the distribution of Meissner and Auerbach's plexi, as well as lucent adjacent ganglion cells.8 FIGURE 1. A, Tissue engineered esophagus, original magnification 20 ×. B, Tissue engineered colon, original magnification 20 ×. C, Tissue engineered stomach; note large lucent parietal cells and glandular structure, original magnification ... Preliminary data showed that TESI generated by our new protocol has markedly improved tissue architecture, including a mucosal immune system with an immunocyte population similar to that of native small intestine.12,13 In addition, response of TESI to exogenous GLP-2 includes mucosal growth and enhanced SGLT1 epxression.14 We hypothesized that together these findings indicated TESI could aid in recovery of SBS. In addition, we sought to confirm the correct architecture of TESI seen on initial histology by performing computer morphometry and immunohistochemistry to assess for nerve and muscle components. To prove the donor origin of the TESI, we sought to label the progenitor cells with green fluorescent protein (GFP), which has additional implications for future more useful transfections, and we initiated confirmation of the differentiated state of the enterocytes in TESI after anastomosis by studying the villin and intestinal alkaline phosphatase content by Northern blot.