bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of CC, CXC, C, and CX3C Chemokines on Proliferation of Myeloid Progenitor Cells, and Insights into SDF‐1‐Induced Chemotaxis of Progenitorsa
Authors: BROXMEYER HAL E. , KIM CHANG H. , COOPER SCOTT H. , HANGOC GIAO , HROMAS ROBERT , PELUS LOUI M.
Published: February 2006

Abstract: Chemokines have been implicated in the regulation of stem/progenitor cell proliferation and movement. The purpose of the present study was to assess a number of new chemokines for suppressive activity and to delve further into SDF‐1‐mediated chemotaxis of progenitor cells. This report extends the list of chemokines that have suppressive activity against immature subsets of myeloid progenitors stimulated to proliferate by multiple growth factors to include: MCP‐4/CKβ‐10, MIP‐4/CKβ‐7, I‐309, TECK, GCP‐2, MIG and lymphotactin. The suppressive activity of a number of other chemokines was confirmed. Additionally, pretreatment of the active chemokines with an acetylnitrile solution enhanced specific activity of a number of these chemokines. The new chemokines found to be lacking suppressive activity include: MCP‐2, MCP‐3, eotaxin‐1, MCIF/HCC‐1/CKβ‐1, TARC, MDC, MPIF‐2/eotaxin‐2/CKβ‐6, SDF‐1 and fractalkine/neurotactin. Overall, 19 chemokines, crossing the CC, CXC, and C subgroups, have now been found to be myelosuppressive, and 14 chemokines crossing the CC, CXC and CX3C subgroups have been found to lack myelosuppressive activity under the culture conditions of our assays. Because of the redundancy in chemokine/chemokine receptor interactions, it is not yet clear through which chemokine receptors many of these chemokines signal to elicit suppressive activities. It was also found that SDF‐1‐induced chemotaxis of progenitors can occur in the presence of fibronectin (FN) and extracellular matrix components and that FN effects involve activation of β1‐, and possibly α4‐, integrins.
Regulation of Transendothelial Migration of Hematopoietic Progenitor Cells
Authors: MÖHLE ROBERT , BAUTZ FRANK , RAFII SHAHIN , RAFII SHAHIN , MOORE MALCOLM A.S. , BRUGGER WOLFRAM , KANZ LOTHAR
Published: February 2006

Abstract: Transendothelial migration of hematopoietic progenitor cells occurs in the bone marrow during mobilization and homing, and may therefore play a key role in the trafficking of hematopoietic stem cells. We hypothesize that adhesion molecules, chemokines, and paracrine cytokines are involved in this multifactorial process. As suggested in several studies, downregulation of adhesion molecules (e.g., integrins) may contribute to mobilization of progenitors due to a decreased avidity to bone morrow stromal and endothelial cells, which express the corresponding ligands. Using an in vitro model of transendothelial migration, we have shown that only a small number of more mature, committed progenitors migrates spontaneously under the control of adhesion molecules of the beta‐2‐integrin family and their corresponding endothelial/ stromal ligands. However, transendothelial migration of progenitors in vitro is substantially enhanced by the chemokine stromal cell‐derived factor‐1 (SDF‐1), which is constitutively produced by bone marrow stromal cells. More primitive progenitors also respond to this chemokine. In addition, the ligand for SDF‐1, the chemokine receptor CXCR‐4, is expressed in greater levels on bone marrow CD34+ cells as compared to mobilized progenitors, suggesting that downregulation of chemokine receptors occurs during progenitor mobilization. Indeed, bone marrow CD34+ cells migrate more avidly in response to SDF‐1 than mobilized progenitors. Paracrine cytokines may also play a role in hematopoietic stem cell trafficking, since growth factor‐stimulated hematopoietic cells produce cytokines that act on endothelial cells (e.g., vascular endothelial growth factor, VEGF), modifying their proliferation, motility, permeability, and fenestration. We conclude that transendothelial migration of hematopoietic progenitor cells is regulated by adhesion molecules, paracrine cytokines, and chemokines. Cytotoxic therapy as well as exogenously administered hematopoietic growth factors may affect adhesion molecule expression, the local cytokine and chemokine milieu, and chemokine receptor expression, which indirectly results in mobilization of hematopoietic stem cells.
Characterization of Purified and Ex Vivo Manipulated Human Hematopoietic Progenitor and Stem Cells in Xenograft Recipients
Authors: BOCK THOMAS A. , ZIEGLER BENEDIKT L. , BÜHRING HANS‐JÖRG , SCHEDING STEFAN , BRUGGER WOLFRAM , KANZ LOTHAR
Published: February 2006

Abstract: Research on the biology, regulation, and transplantation of human hematopoietic stem cells requires test systems for the detection, monitoring, and quantitation of these cells. Xenografted animal models provide suitable stem cell assays, since they allow long‐term engraftment, multilineage differentiation, and serial transfer of human hematopoietic cells. Recent techniques for the separation of hematopoietic cells have provided highly purified cellular subsets selected on the basis of the surface marker phenotype. The stem cell content of these subsets, however, is still unclear. Also, innovative approaches for the induction of hematopoietic cell proliferation and differentiation have generated ex vivo manipulated cells whose biological properties and functions still remain to be assessed. This paper reports on the biological characterization of these cell populations by the use of xenograft models.
Ex Vivo Expansion and Genetic Marking of Primitive Human and Baboon Hematopoietic Cells
Authors: MEDIN JEFFREY A. , BRANDT JOHN E. , ROZLER ELEN , NELSON MARY , BARTHOLOMEW AMELIA , LI CONGFEN , TURIAN JULIUS , CHUTE JOHN , CHUNG THEODORE , HOFFMAN RONALD
Published: February 2006

Abstract: The achievement of positive outcomes in many clinical protocols involving hematopoietic stem cells (HSCs) has been handicapped by the limited numbers of marrow repopulating cells available to actually bring about therapy. This insufficiency has been especially problematic in stem cell transplantation and gene therapy. A number of studies have been initiated to attempt expansion of HSCs, mainly by manipulation of key cytokines in cell suspension cultures. Unfortunately, these expansion methods usually lead to altered properties in the amplified cells, mainly by reducing their self‐renewal and multilineage differentiative potentials. Here we discuss our ongoing work, utilizing a unique endothelial cell line that supports primitive hematopoiesis, to attempt to generate expansion of primate HSCs that retain their elementary properties. Genetic marking of early hematopoietic cells to facilitate tracking will be mentioned as will the development and employment of assay systems designed to evaluate the long‐term functional attributes of the expanded cells.
Embryonic Beginnings of Definitive Hematopoietic Stem Cells
Authors: DZIERZAK ELAINE
Published: February 2006

Abstract: The ability of the many cell types within the adult blood system to be constantly replenished and renewed from hematopoietic stem cells is an interesting problem in development and differentiation and has led to questions concerning how, when and where thses stem cells for the adult hematopoietic system are generated within the embryo. During embryonic development many mature hematopoietic cells appear before adult‐type hematopoietic stem cells thus the notion of a conventional hematopoietic hierarchy is challegned. Experiments probing the development of hematopoietic stem cells in the mouse embryo strongly suggest that at least two independent hematopoietic sites generate blood cells during development; the yolk sac, which produces the transient embryonic hematopoietic system, and the AGM (aorta‐gonad‐mesonephros) region, which initiates the long‐lived adult hematopoietic system.
Asymmetric Cell Divisions in Hematopoietic Stem Cells
Authors: BRÜMMENDORF TIM H. , DRAGOWSKA WIESLAWA , LANSDORP PETER M.
Published: February 2006

Abstract: In order to study cell kinetics involved in long‐term hematopoiesis, we studied single sorted candidate hematopoietic stem cells (HSC) from fetal liver cultured in the presence of a mixture of stimulatory cytokines. After 8‐10 days in culture, the number of cells varied from less than a hundred to more than ten thousand cells. Single cells in slowly growing colonies were recloned upon reaching a 100‐200‐cell stage. Strikingly, the number of cells in subclones varied widely again. These results are indicative of asymmetric divisions in primitive hematopoietic cells in which the proliferative potential and cell cycle properties are unevenly distributed among daughter cells. The continuous generation of heterogeneity in cell cycle properties among the clonal progeny of HSC appears a relevant mechanism to maintain long‐term maintenance of hematopoiesis in vitro and in vivo.
Searching for Stem Cell Regulatory Molecules Some General Thoughts and Possible Approaches
Authors: LEMISCHKA IHOR
Published: February 2006

Abstract: Hematopoietic development in the mammal can be represented as a numerically expanding hierarchy of cell populations that are progressively restricted in their self‐renewal and differentiation abilities. Classical functional studies have now been extebded to provide exact physical descriptions of various stages in the Hematopoietic hierarchy. In particular, much information is available that defines the properties of the most primitive stem cell compartment. In addition, a number of in vitro culture systems suggest the possibility of maintaining and expanding these cells in a defined context. In all developmental systems, unique profiles of expressed genes define distinct differentiation stages. Within these profiles are gene products that play crucial roles in the regulation of cell‐fate decisions. Recent progress in hematopoietic biology provides the framework within which to define molecular phenotypes for hematopoietic stem cells and their immediate clonal progeny. Identifying novel gene products expressed predominantly in uncommittes stem cells together with functional loos and gain‐of‐function approaches should begin to unravel the molecular mechanisms that govern biological phenomena such as self‐renewal, commitment, and proliferation in the hematopoietic system.
Stem Cells, Pre‐Progenitor Cells and Lineage‐Committed Cells: Are Our Dogmas Correct?
Authors: METCALF D.
Published: February 2006

Abstract: Recent developments warrant careful reexamination of several of the central dogmas of hematopoiesis. The bioassays previously used may have predetermined which subsets of hematopoietic stem cells are regarded as having long‐term repopulating activity and thus have produced misleading data. Lineage commitment in multipotential cells has been regarded as an immutable stochastic process but may be a process that can be modified by extrinsic signaling. Finally, loss of self‐renewal activity has been regarded as progressive and irreversible but this response to signaling can be blocked by cytokine‐inducible modulating proteins.
G‐CSF Receptor Mutations in Patients with Severe Congenital Neutropenia Do Not Abrogate Jak2 Activation and Stat1/Stat3 Translocation
Authors: HERBST A. , KOESTER M. , WIRTH D. , HAUSER H. , WELTE K.
Published: February 2006

Abstract: Severe congenital neutropenia (SCN) is an inherited disorder of myelopoiesis, characterized by a maturation arrest at the stage of promyelocytes and myelocytes in bone marrow, and absence or low levels of mature neutrophil granulocytes in peripheral blood. Recently, studies of patients with SCN who subsequently developed acute myeloid leukemia (AML) revealed nonsense mutations in the cytoplasmic domain of the granulocyte colony‐stimulating factor (G‐CSF) receptor messenger RNA. We focused our interest on the G‐CSF‐mediated signaling cascade to examine the consequences of the observed point mutations for the nuclear translocation of the transcription factors Stat1 and Stat3. Expression vectors encoding for truncated G‐CSF receptors were transfected in the murine fibroblast cell line C243 expressing a fusion protein consisting of the transcription factor Stat1 and Stat3, respectively, and the green fluorescent protein (GFP). Nuclear translocation of the GFP fusion proteins was examined after G‐CSF stimulation of the transfected cells.
Clinical Applications of Mixed Chimerism
Authors: EXNER BEATE G. , DOMENICK MICHELE A. , BERGHEIM MARIANNE , MUELLER YVONNE M. , ILDSTAD SUZANNE T.
Published: February 2006

Abstract: Bone marrow transplantation (BMT) Is currently a procedure that Is associated with high morbility and mortality. Thus, The clinical application of this technique is limited to the treatment of life‐threatening hematopoietic malignancies. The morbility and mortality of BMT is mainly related to graft‐versus‐host disease (GVHD), failure of engraftment, and toxicity related to fully myeloablative conditioning. GVHD can be prevented by T‐cell depletion. However, T‐cell depletion increases the risk of failure of engraftment. With the identification of a facilitating cell population that enables engraftment of hematopoietic stem cells across major histocompatibility barriers, the dichotomy between GVHD and failure of engraftment has been resolved. If one could overcome the toxicity of conditioning with the development of partially ablative conditioning strategies, BMT could be used for the treatment of a variety of nonmalignent diseases, as well as in the induction of donor‐specific transplantation tolerance. This review outlines the development and advantages of partially ablative conditioning strategies and illustrates possible applications of the technique. Forty years ago E.D. Thomas discussed the potential of BMT for treating immunodeficiencies and for the induction of transplantation tolerance. 1 BMT can be viewed as a natural form of gene therapy to replace a defective cell or enzyme with a functional and normally regulated one.
Control of Complement Activities for Immunoisolation
Authors: IWATA HIROO , MURAKAMI YOSHINOBU , IKADA YOSHITO
Published: February 2006

ABSTRACT: Immunoisolation of cells by semipermeable membranes is a most promising approach to transplant xenogeneic cells. Although membranes which allow xenotranplantation have been reported, ambiguity remains as to their long term effectiveness. In this review, we would like to reconsider the immuno‐isolative effectiveness of membranes reported from the standpoint of permeability and present our strategy to prepare membranes that can realize long‐term functioning of xenograft. There are distinct different types of semi‐permeable membranes, hydrogel membranes and ultrafiltration membranes. Studies on their permeability indicated that neither of these membranes effectively fractionate solutes on the basis of molecular size under a diffusion‐controlled process, nor thus can they immuno‐isolate xenograft for a long time. Humoral immunity including antibodies and complement proteins is suspected of playing a major role in the rejection of xenografts. Control of complement cytolytic activities, not antibody permeation, may be a key factor determining the fate of the xenograft enclosed in membranes. We found that the microbead containing poly(styrene sulfonic acid) can consume complement cytolytic activities and thus can effectively protect xenogeneic islets of Langerhans in diabetic mice from the humoral immunity.
Designing Biomaterials to Direct Biological Responses
Authors: HEALY KEVIN E. , REZANIA ALIREZA , STILE RANEE A.
Published: February 2006

ABSTRACT: We have set forth a design strategy for creating biomimetic materials that direct the formation of tissue surrounding implants or regeneration within porous scaffolds. Our studies have established that heterogeneous mimetic peptide surfaces (MPS) containing both the ‐RGD‐ (cell‐binding) and ‐FHRRIKA‐(putative heparin‐binding) peptides, unique to BSP, in the ratio of 75:25 (MPS II) or 50:50 (MPS III) proved to be more biologically relevant and specific for RCO cell function. The initial response of human osteoblast‐like cells to these surfaces was mediated by the collagen (α2β1) and vitronectin receptors (αvβ3), whereas the vitronectin receptor alone dominated longer‐term events (> 30 min). MPS II and III surfaces enhanced cell spreading and long‐term events such as mineralization of the extracellular matrix compared to homogenous peptide surfaces and controls. Furthermore, extensive mineralization of the ECM deposited by RCOs occurred when the peptide was coupled to an interfacial interpenetrating polymer network (IPN) that resisted protein deposition (i.e., non‐specific adsorption) and fouling. Work on thermo‐reversible P(NIPAAm‐co‐AAc) hydrogels demonstrated the ability to create materials that can be delivered to the body in a minimally invasive manner and support tissue regeneration. These hydrogels can be modified to incorporate biofunctional components such as the biomimetic peptides, theoretically enhancing their ability to foster tissue regeneration. These results suggest that biomaterials can be engineered to mimic ECM components of bone (e.g., various organs) by grafting peptides in the appropriate ratios of the cell and heparin‐binding domains, and ultimately modulate the expression of the osteoblast cell phenotype. Approaches similar to the one presented in this work can be used to design materials for hybrid artificial organs and other tissues.
New Microcapsules Based on Oligoelectrolyte Complexation
Authors: BARTKOWIAK ARTUR , HUNKELER DAVID
Published: February 2006

ABSTRACT:A new one‐step microencapsulation procedure has been developed. For the alginate/oligochitosan system the molar mass of the chitosan is a key parameter in the formation of stable, elastic capsules with high modulus. Furthermore, the selection of an optimum molar mass provides an additional degree of freedom, permitting the simultaneous regulation of mechanical properties and permeability without the need for multicomponent organic‐inorganic chemistries as have been previously employed. The effects of molar mass of chitosan, its concentration, the alginate molar mass and its metal salt on the preparation, physical properties, and release characteristics of the capsules have been studied.
Development of Cellulose Sulfate‐based Polyelectrolyte Complex Microcapsules for Medical Applications
Authors: DAUTZENBERG HORST , SCHULDT UTE , GRASNICK GERD , KARLE PETER , MÜLLER PETRA , LÖHR MATTHIAS , PELEGRIN MIREIA , PIECHACZYK MARC , ROMBS KERSTIN V. , GÜNZBURG WALTER H. , SALMONS BRIAN , SALLER ROBERT M.
Published: February 2006

ABSTRACT: Microencapsulation, as a tool for immunoisolation for allogenic or xenogenic implants, is a rapidly growing field. However most of the approaches are based on alginate/polylysine capsules, despite this system's obvious disadvantages such as its pyrogenicity. Here we report a different encapsulation system based on sodium cellulose sulfate and polydiallyldimethyl ammonium chloride for the encapsulation of mammalian cells. We have characterized this system regarding capsule formation, strength and size of the capsules as well as viability of the cells after encapsulation. In addition, we demonstrate the efficacy of these capsules as a “microfactory”in vitro and in vivo. Using encapsulated hybridoma cells we were able to demonstrate long‐term release of antibodies up to four months in vivo. In another application we could show the therapeutic relevance of encapsulated genetically modified cells as an in vivo activation center for cytostatic drugs during tumor therapy.
In Situ Electrochemical Oxygen Generation with an Immunoisolation Device
Authors: WU HAIYAN , AVGOUSTINIATOS EFSTATHIOS S. , SWETTE LARRY , BONNER‐WEIR SUSAN , WEIR GORDON C. , COLTON CLARK K.
Published: February 2006

The viability and function of transplanted tissue encapsulated in immunobarrier devices is subject to oxygen transport limitation. In this study, we have designed and used an in situ electrochemical oxygen generator which decomposes water electrolyticaly to provide oxygen to the adjacent planer immunobarrier diffusion chamber. The rate of oxygen generation, which increases linearly with electrical current, was accurately controlled. A theoretical model of oxygen diffusion was also developed and was used to calculate the oxygen profiles in some of the experimental systems. In vitro culture experiments were carried out with βTC3 cells encapsulated in titanium ring devices. The growth and viability of cells with or without in situ oxygen generation was studied. We found that under otherwise similar culturing conditions, the thickness of the cell layer and the viability of cells was the highest in devices cultured in stirred media with oxygen generation, even though the thickness had not reached the theoretically predicted value, and lowest in those unstirred and without oxygen generation.
Conformal Coating of Small Particles and Cell Aggregates at a Liquid‐Liquid Interface
Authors: MAY MICHAEL H. , SEFTON MICHAEL V.
Published: February 2006

ABSTRACT: Polymer encapsulation of allogeneic or xenogeneic tissue is under active investigation as a means of isolating transplanted cells, such as pancreatic islets, from the immune system. We report here a method for coating small particles and cell aggregates with a very thin water insoluble hydroxyethyl methacrylate‐methyl methacrylate (HEMA‐MMA) membrane that conforms to the shape of the aggregate, and minimizes the polymer's contribution to the total transplant volume. Cell aggregates were coated at a liquid‐Liquid interface of a discontinuous density gradient composed of both aqueous and organic liquids. By increasing the viscoisty difference and decreasing the density difference between the two liquies of the coating interface, coatings from approximately 1 to 15 μm thick were fpr,ed. Aggregates of HepG2 cells and pancreatic islets were coated and remained viable.
Potential Application of Neonatal Porcine Islets as Treatment for Type 1 Diabetes: A Review
Authors: RAYAT GINA R. , RAJOTTE RAY V. , KORBUTT GREGORY S.
Published: February 2006

ABSTRACT:Islet transplantation has been shown to be a viable option for treating patients with type 1 diabetes. However, widespread clinical application of this treatment will necessitate an alternative source of insulin‐producing tissue. Porcine pancreata may be a potential source of islets since pigs are inexpensive, readily available, and exhibit morphological and physiological characteristics comparable to humans. Recently, we developed a simple, standardized procedure for isolating large composition. Following nine days ofin vitroculture, tissue from one neonatal pig pancreas yielded approximately 50,000 islet cell aggregates, consisting of primarily epithelial cells (57%) and pancreatic endocrine cells (35%). In addition, neonatal porcine islets were responsive to glucose challenge in vitro and were capable of correcting hyperglycemia in alloxan‐induced diabetic nude mice. Although neonatal porcine islets constitute an attractive alternative source of insulin‐producing tissue for clinical transplantation, many aspects such as the immunological responses to these tissue and the latent period (2 to 8 weeks) between transplantation of these islets and the reversal of hyperglycemia need further investigation. This article discusses these issues and presents possible solutions to problems that may hinder the potential application of neonatal porcine islets for transplantation into patients with type 1 diabetes.
Islet Cryopreservation Protocols
Authors: RAJOTTE RAY V.
Published: February 2006

ABSTRACT: Low temperature banking of islets has facilitated ongoing clinical trials, allowing for the collection and long‐term storage of islets during which viability and sterility assessment can be carried out. Islets from most species of animals have been cryopreserved using various freeze‐thaw protocols; however, the best to date is slow cooling to −40°C and rapid thawing from −196°C. If one carefully follows the three distinct steps of freezing and thawing human islets can be successfully cryopreserved, allowing for the establishment of a low temperature bank with diverse HLA (Human Leukocyte Antigen) and ABO phenotypes. Using a combination of fresh and cryopreserved islets to transplant Type I diabetic patients, long‐term insulin independence has been obtained.
Encapsulated, Genetically Engineered Cells, Secreting Glucagon‐like Peptide‐1 for the Treatment of Non‐insulin‐dependent Diabetes Mellitus
Authors: BURCELIN RÉMY , ROLLAND ERIC , DOLCI WANDA , GERMAIN STÉPHANE , CARREL VÉRONIQUE , THORENS BERNARD
Published: February 2006

ABSTRACT: Non‐insulin‐dependent, or type II, diabetes mellitus is characterized by a progressive impairment of glucose‐induced insulin secretion by pancreatic β cells and by a relative decreased sensitivity of target tissues to the action of this hormone. About one third of type II diabetic patients are treated with oral hypoglycemic agents to stimulate insulin secretion. These drugs however risk inducing hypoglycemia and, over time, lose their efficacy. An alternative treatment is the use of glucagon‐like peptide‐1 (GLP‐1), a gut peptidic hormone with a strong insulinotropic activity. Its activity depends of the presence of normal blood glucose concentrations and therefore does not risk inducing hypoglycemia. GLP‐1 can correct hyperglycemia in diabetic patients, even in those no longer responding to hypoglycemic agents. Because it is a peptide, GLP‐1 must be administered by injection; this may prevent its wide therapeutic use. Here we propose to use cell lines genetically engineered to secrete a mutant form of GLP‐1 which has a longer half‐life in vivo but which is as potent as the wild‐type peptide. The genetically engineered cells are then encapsulated in semi‐permeable hollow fibers for implantation in diabetic hosts for constant, long‐term, in situ delivery of the peptide. This approach may be a novel therapy for type II diabetes.
Reverse Engineering of Bioadhesion in Marine Mussels
Authors: WAITER J. HERBERT
Published: February 2006

ABSTRACT: Marine mussels (Mytilus) are experts at bonding to a variety of solid surfaces in a wet, saline and turbulent environment. Bonding is rapid, permanent, versatile and protein‐based. In mussels, adhesive bonding takes the form of a byssus‐a bundle of extracorporeal threads‐each connected to living tissues of the animal at one end and secured by an adhesive plaque at the other. We have investigated the composition and formation of byssal plaques and threads with the hope of discovering technologically relevant innovations in chemistry and materials science. All proteins isolated from the byssus to date share the quality of containing the unusual amino acid, 3,4‐dihydroxyphenylalanine. This residue appears to have a dual functionality with significant consequences for adsorption and cohesion. On the one hand, it forms a diverse array of weaker molecular interactions such as metal chelates, H‐bonds, and π‐cations: these appear to dominate in surface behavior (adsorption). On the other hand, 3,4‐dihydroxyphenylalanine and its redox couple, dopaquinone, can mediate formation of covalent cross‐links among byssal proteins (cohesion). One of the challenges in making functional biomimetic versions of byssal adhesion is to understand how these two reactivities are balanced.
Tissue Engineering of Bone in the Craniofacial Complex
Authors: HOLLINGER JEFFREY O. , WINN SHELLEY R.
Published: February 2006

ABSTRACT: Tissue engineered therapies to regenerate bone in the craniofacial complex will probably include combinations of BMP‐like molecules, a BMP‐responsive set of cells (both endogenous and exogenous), and packaging in a surgically convenient format. In this report we have described our work with OPCs, BMP, and polymer: components suitable for tissue engineering.
Bioreactor Development for Tissue‐Engineered Cartilage
Authors: WU FLORENCE , DUNKELMAN NOUSHIN , PETERSON AL , DAVISSON TWANA , DE LA TORRE REBECCA , JAIN DEEPAK
Published: February 2006

ABSTRACT: The development of tissue engineered cartilage is emerging as a potential treatment for the repair of cartilage defects. By seeding chondrocytes onto poly‐glycolic acid (PGA) biodegradable scaffolds within a convective‐flow bioreactor, the synthesis of tissue‐engineered articular cartilage has been recently demonstrated. The ability to cultivate and manipulate this cell‐polymer construct to possess specific dimensions, as well as biochemical and biomechanical properties is critical for potential application as an in vivo therapy of damaged articular surfaces. Bioreactor design requirements for stages from research to development to commercialization are discussed. Advantages and limitations to various bioreactor designs are critiqued. These studies illustrate the ability to synthesize tissue‐engineered cartilage under convective‐flow conditions for potential human tissue repair.
Overview of Charcot‐Marie‐Tooth Disease Type 1A
Authors: THOMAS P. K.
Published: February 2006

ABSTRACT: Type 1A CMT disease is most commonly due to a segmental duplication on chromosome 17p11.2, leading to the presence of an extra copy of the gene for peripheral myelin protein 22 (PMP22). Inheritance is autosomal dominant in pattern. Analysis of nerve biopsies suggests that the disorder is caused by increased gene dosage. Occasionally CMTIA results from point mutations in the PMP22 gene. Onset of symptoms in cases with a duplication is usually in the first decade of life; slowing of nerve conduction velocity is evident from the age of 2 years. Active demyelination is restricted to childhood. It leads to hypertrophic “onion bulb” changes and is accompanied and followed by progressive axonal loss. The commonest clinical phenotype is the CMT syndrome with distal muscle wasting and weakness, tendon areflexia, usually mild sensory loss, and foot deformity. Other phenotypes include the Roussy‐Lévy syndrome, in which postural tremor and ataxia are associated, and cases with severe distal sensory loss and acrodystrophic changes.
Overview of Hereditary Neuropathy with Liability to Pressure Palsies
Authors: CHANCE PHILIP F.
Published: February 2006

ABSTRACT: Hereditary neuropathy with liability to recurrent pressure‐sensitive palsies (HNPP; also called tomaculous neuropathy) is an autosomal dominant disorder that produces an episodic, recurrent demyelinating neuropathy. HNPP generally develops during adolescence, and may cause attacks of numbness, muscular weakness, and atrophy. Peroneal palsies, carpal‐tunnel syndrome, and other entrapment neuropathies are frequent manifestations of this disorder. Motor and sensory nerve conduction velocities may be reduced in clinically affected patients, as well as in asymptomatic gene carriers. Pathological changes observed in peripheral nerves of HNPP patients include segmental demyelination and tomaculous or “sausage‐like” formations. Because of mild overlap of clinical features with CMT1, HNPP patients may be misdiagnosed as having CMT1. HNPP and CMT1 are both demyelinating neuropathies; however, their clinical, pathological, and electrophysiological features are quite distinct. The HNPP locus maps to chromosome 17p11.2‐12 and is associated with a 1.5‐Mb deletion. DNA markers known to map to the region in 17p11.2–12 associated with the CMT1A duplication, including the PMP22 gene, are deleted in HNPP. The deletion breakpoints in HNPP map to the same intervals in which the CMT1A duplication breakpoints map. In one pedigree, de novo deletion of paternal origin was detected as a basis for sporadic HNPP. HNPP results from deletion of the PMP22 gene and underexpression of this locus, which is reflected in reduced mRNA and protein levels in sural nerve biopsy samples from HNPP patients. Further support for this hypothesis was provided by the identification of a nondeleted HNPP kindred in which a two base pair deletion and early termination codon within exon 1 of PMP22 was present. The possibility of genetic heterogeneity in HNPP was raised by the identification of an HNPP pedigree that did not demonstrate linkage to the region of 17p11.2‐12. Hereditary neuralgic amyotrophy (familial brachial plexus neuropathy) is an autosomal dominant disorder causing painful, recurrent brachial plexopathies and maps to chromosome 17q25.
Molecular Mechanisms for CMT1A Duplication and HNPP Deletion
Authors: BOERKOEL C. F. , INOUE K. , REITER L. T. , WARNER L. E. , LUPSKI J. R.
Published: February 2006

ABSTRACT: As the best characterized human genomic disorders, 118 CMT1A and HNPP illustrate several common mechanistic features of genomic rearrangements. These features include the following: (1) Recombination occurs between homologous sequences flanking the duplicated/deleted genomic segment. (2) The evolution of the mammalian genome may result in an architecture consisting of region‐specific low‐copy repeats that predispose to rearrangement secondary to providing homologous regions as substrate for recombination. (3) Strand exchange occurs preferentially in a region of perfect sequence identity within the flanking repeat sequences. (4) Double‐strand breaks likely initiate recombination between the flanking repeats. (5) The mechanism and rate of homologous recombination resulting in DNA rearrangement may differ for male and female gametogenesis. (6) Homologous recombination resulting in DNA rearrangement occurs with high frequency in the human genome. (7) Genomic disorders result from structural features of the human genome and not population specific alleles or founder effects; therefore, genomic disorders appear to occur with equal frequencies in different world populations.
X‐linked Charcot‐Marie‐Tooth Disease and Connexin32
Authors: FISCHBECK KENNETH H. , ABEL ANNETTE , LIN GRACE S. , SCHERER STEVEN S.
Published: February 2006

ABSTRACT: X‐linked Charcot‐Marie‐Tooth disease is caused by mutations in the gene for the gap junction protein connexin32. This protein is expressed in peripheral nerve and present in noncompacted myelin, where it likely forms channels around and across the myelin sheath. Studies in cell culture and in transgenic mice show that connexin32 mutations can cause a loss of channel function or a gain of toxic effects on myelinating Schwann cells or both, with resulting peripheral nerve degeneration.
A Clinical Review of Charcot‐Marie‐Tooth
Authors: GARCIA CARLOS A.
Published: February 2006

ABSTRACT: CMT polyneuropathy is a complex genetically and clinically heterogeneous group of disorders. The rapid advances in our understanding of the molecular basis of these groups of neuropathies have helped to resolve some of the controversial issues regarding the clinical and genetic classification. However, there is still confusion and chaos in the terminology employed by different groups of researchers. A reclassification based on the molecular mechanisms of these neuropathies will help in the future to unify and simplify the diagnosis of these complex disorders. The understanding of the molecular mechanisms will also help in the future to find a way to control or treat these hereditary neuropathies.
Schwann Cell‐Axon Interactions in Charcot‐Marie‐Tooth Disease
Authors: GRIFFIN JOHN W. , SHEIKH KAZIM
Published: February 2006

ABSTRACT: The consequences of the molecular defects in myelin genes are manifest from the time of birth in most patients, as assessed either electrodiagnostically or pathologically. Reduction in nerve conduction velocity is present from the first weeks of life, but the clinical manifestations have been recognized as predominantly distal and dominated by distal muscle atrophy. The recent advances in understanding the molecular defects involved present a paradox: the molecular abnormalities are found in intrinsic Schwann cell proteins, not in distal axons. Thus, the interactions between Schwann cells and axons have been the focus of much attention. Here, we present findings on the effects of Schwann cell phenotype on the axon and how abnormalities in myelin alter the axonal cytoskeleton. The clinical importance of Schwann cell‐axon interactions extends beyond Charcot‐Marie‐Tooth disorders. The same principles may apply in the CNS, for example, in multiple sclerosis.
Nodes, Paranodes, and Incisures: From Form to Function
Authors: SCHERER STEVEN S.
Published: February 2006

ABSTRACT: The exquisite molecular architecture of myelinated fibers is the basis for saltatory conduction. The nodal axolemma contains high concentrations of voltage‐dependent sodium channels as well as the cell adhesion molecules neurofascin and Nr‐CAM, all of which are probably linked to the axonal cytoskeleton by ankyrin. At paranodes, the axonal membrane contains paranodin/Caspr, which may be a Ca2+‐dependent cell adhesion molecule with a heterophilic partner on the apposed glial cell membrane. The juxtaparanodal axonal membrane contains the potassium channels Kv1.1 and Kv1.2, as well as the associated β2 subunit, which together may function to dampen re‐entrant excitation. The paranodes and incisures of the Schwann cell myelin sheath contain “reflexive” adherens junctions and gap junctions. The adherens junctions are composed of E‐cadherin as well as α‐ and β‐catenin, which together probably join the adjacent layers of noncompact myelin together. Reflexive gap junctions, comprising connexin32 and at least one other connexin protein, form a radial pathway for the diffusion of ions and small molecules directly across the myelin sheath.
The Anatomy and Cell Biology of Peripheral Myelin Protein‐22
Authors: SNIPES G. JACKSON , ORFALI WAYEL , FRASER ANDREW , DICKSON KATHLEEN , COLBY JOSHUA
Published: February 2006

ABSTRACT: The gain of function phenotypes exhibited by the heterozygous Tr, Tr‐J, and CMT1A mutations indicate that these mutations interfere with more than the function of a single PMP22 allele. The identification of proteins that interact with PMP22 and that are sensitive both to stoichiometry and the effects of the mutations could provide important leads to a unified hypothesis to explain the riddle of the PMP22‐related neuropathies.
Distinct Phenotypes Associated with Increasing Dosage of the PLP Gene: Implications for CMT1A Due to PMP22 Gene Duplication
Authors: ANDERSON T. J. , KLUGMANN M. , THOMSON C. E. , SCHNEIDER A. , READHEAD C. , NAVE K‐A. , GRIFFITHS I. R.
Published: February 2006

ABSTRACT: Increased dosage of the proteolipid protein (Plp) gene causes CNS disease (Pelizaeus‐Merzbacher disease [PMD]), which has many similarities to disorders of the PNS associated with duplication of the peripheral myelin protein‐22 (PMP22) gene locus. Transgenic mice carrying extra copies of the wild‐type Plp gene provide a valid model of PMD. Variations in gene dosage can cause a wide range of phenotypes from severe, lethal dysmyelination through late‐onset demyelination. A predilection for different fiber diameters may occur within the various phenotypes with dysmyelination being more obvious in large fibers and late‐onset degeneration predominantly affecting small fibers. Although the frequency of apoptotic oligodendrocytes is increased with high gene dosage, the number of mature oligodendrocytes appears adequate. Oligodendrocytes in the dysmyelinated CNS express a range of genes typical of mature cells, yet are unable to assemble sufficient myelin. Oligodendrocytes contain abnormal vacuoles and stain intensely for PLP and other proteins such as MAG. The findings suggest that with high gene dosage much of the PLP, and possibly other proteins, is missorted and degraded in the lysosomal system.
Trembler as a Mouse Model of CMT1A?
Authors: GARBAY BERTRAND , SALLES JEROME , KNOLL ANJA , BOIRON‐SARGUEIL FRANÇOISE , HEAPE ANTHONY M. , BONNET JACQUES , CASSAGNE CLAUDE
Published: February 2006

ABSTRACT: The Trembler mouse suffers from a dominantly inherited autosomal mutation that results in an abnormal myelination of the peripheral nervous system. Biochemical studies have shown that dysmyelination is the primary event, demyelination being a late‐occurring process. The expression of myelin protein genes has been studied. The steady‐state levels for PMP22 mRNA represent 10 and 5% of normal values in the nerves of heterozygous and homozygous Trembler, respectively. This is due to a reduced expression of the specific transcript driven by the promoter 1 of the PMP22 gene. Collective results indicate that Trembler dysmyelination is not necessarily the consequence of a large accumulation of the mutated PMP22 protein. Moreover, it appears that the situation in the Trembler is different from that encountered in most CMT1A patients, where an increased PMP22 gene dosage is responsible for the disease. Therefore, the Trembler mutant is perhaps not an ideal model for this human neuropathy.
P0‐Deficient Knockout Mice as Tools to Understand Pathomechanisms in Charcot‐Marie‐Tooth 1B and P0‐Related Déjérine‐Sottas Syndrome
Authors: MARTINI RUDOLF
Published: February 2006

ABSTRACT: P0 (mylin protein zero, MPZ) is one of the four identified culprit genes for hereditary peripheral neuropathies. Homo‐ or heterozygous null mutants for P0 share pathological features with some patients suffering from P0‐related Déjérine‐Sottas‐Syndrome (DSS) or Charcot‐Marie‐Tooth (CMT) neuropathy, type 1B, respectively, and can thus be considered as appropiate animal models for the corresponding diseases. This article focuses on distinct histopathological features in these mice. Such features include dysregulation of Schwann cell genes and axonal loss in homozygous mutants and significant infiltration of T‐lymphocytes and macrophages in heterozygous mutants. These histological characteristics are instrumental in understanding the pathogenesis of the disease and may help in developing treatments.
Peripheral Nerve Dysmyelination Due to P0 Glycoprotein Overexpression Is Dose‐Dependent
Authors: QUATTRINI ANGELO , FELTRI MARIA LAURA , PREVITALI STEFANO , FASOLINI MARINA , MESSING ALBEE , WRABETZ LAWRENCE
Published: February 2006

ABSTRACT: We have previously shown that increased dosage of the mouse protein zero gene (Mpz) causes a dysmyelinating neuropathy in transgenic (Tg80) mice. To ask whether the dysmyelination is dose dependent, we inbred one of the Tg80 lines and compared the resulting phenotype in homozygous and heterozygous mice. Whereas heterozygous mice (30% overexpression) have only transient peripheral nerve hypomyelination at two weeks after birth and normal myelin at four weeks after birth, homozygous mice demonstrated more severely hypomyelinated nerves. In the latter, many Schwann cells had achieved a one‐to‐one relationship with large axons but formed no myelin at four weeks after birth. Expression analysis confirmed a doubling of Mpz overexpression in the sciatic nerves of the homozygous mice. Thus, a threshold exists for Mpz overexpression, above which dysmyelination results. These data have important implications for replacement therapy in Charcot‐Marie‐Tooth 1B neuropathies due to loss of P0 function.
Electrophysiologic Features of Inherited Demyelinating Neuropathies: A Reappraisal
Authors: LEWIS RICHARD A. , SUMNER AUSTIN J.
Published: February 2006

ABSTRACT: The observation that inherited demyelinating neuropathies tend to have uniform conduction slowing and acquired disorders (CIDP and variants) have nonuniform or multifocal slowing was made before the identification of genetic defects of specific myelin constituents that cause the different forms of Charcot‐Marie‐Tooth and other inherited disorders involving peripheral nerve myelin. It is becoming clear that the electrophysiologic aspects of these disorders are more complex than previously realized. We review the current information available on the electrophysiologic features of the inherited demyelinating neuropathies in hopes of clarifying the clinical electrodiagnostic features of these disorders as well as to shed light on the physiologic consequences of the different genetic mutations.
Variability of Presentation in Hereditary Neuropathy with Liability to Pressure Palsy Results in Underrecognition
Authors: KUMAR NEERAJ , COLE JULIE , PARRY GARETH J.
Published: February 2006

ABSTRACT: The genetic defect responsible for hereditary neuropathy with liability to pressure palsy (HNPP) is located in the same segment that is duplicated in Charcot‐Marie‐Tooth type 1A (CMT1A). HNPP had been presumed to be rare until an epidemiological study found a much higher incidence than was expected; the researchers suggested that HNPP was underrecognized because many affected persons have mild symptoms. We believe that another reason for underdiagnosis of HNPP is the marked phenotypic variability of the disease. We recommend, therefore, that DNA analysis for the 17p11.2 deletion be considered in patients with unexplained demyelinating neuropathy regardless of family history.
Free Radicals and Hearing: Cause, Consequence, and Criteria
Authors: EVANS PATRICIA , HALLIWELL BARRY
Published: February 2006

ABSTRACT: Reactive oxygen and nitrogen species, including free radicals, are produced in the human body in both health and disease. In health, they may arise as regulatory mechanisms, intercellular signaling species, or as bacteriocidal agents. Their production is normally controlled by the antioxidant defense mechanisms that include intracellular enzymes‐for example, glutathione peroxidase and superoxide dismutase‐and low molecular‐mass compounds such as vitamin E or ascorbic acid. Although repair mechanisms exist, some steady‐state basal oxidative damage occurs in all individuals.

Oxidative stress arises when there is a marked imbalance between the production and removal of reactive oxygen and nitrogen species. This may originate from an overproduction of these substances or from a depletion in the antioxidant defenses. Certain drugs may induce oxidative stress by forming drug‐derived radicals that can not only deplete the antioxidant defenses but can also react directly with biomolecules. To be able to assess whether oxidative stress is occurring in a particular tissue, reliable biomarkers of oxidative damage are required. Since oxidative stress can damage all major biomolecules in vitro and probably in vivo, biomarkers for DNA, protein, and lipid damage are being developed which, when taken with an assessment of the antioxidant status of the individual, will allow evaluation of the involvement of oxidative stress in the etiology of disease and in the side effects of drugs. There is some evidence to suggest that free radical‐mediated damage may be involved in the ototoxicity of aminoglycosides and cisplatin derivatives. Whether this is a cause or consequence of the toxic insult to the sensory hair cells of the inner ear remains to be determined.
Genetic Factors in Aminoglycoside Toxicity
Authors: FISCHEL‐GHODSIAN NATHAN
Published: February 2006

ABSTRACT: Ototoxicity is the major irreversible toxicity of aminoglycosides, and occurs both in a dose‐dependent and idiosyncratic fashion. The idiosyncratic pathway is presumably due to genetic predispositions, and in 1993 we identified an inherited mutation that predisposes to aminoglycoside ototoxicity, the A1555G mutation in the mitochondrial 12S ribosomal RNA gene. Seventeen‐33% of patients with aminoglycoside ototoxicity carry this mutation.

In a search for additional susceptibility mutations, a dual strategy of yeast genetics and candidate genes was employed. Through yeast genetics 8 genes that by overexpression prevent aminoglycoside toxicity were identified. The human homologues of these genes may harbor aminoglycoside susceptibility mutations. Another candidate gene is the mitochondrial ribosomal protein S12, which interacts with the ribosomal RNA gene and in bacteria can harbor aminoglycoside resistance mutations. Analysis of this gene in 41 patients with aminoglycoside ototoxicity did not reveal any mutations in the coding regions. However, an Italian family with five maternally related family members who went deaf after aminoglycosides led to the identification of the second susceptibility mutation in the mitochondrial 12S ribosomal RNA gene, ΔT961Cn.

While these findings have immediate clinical implications for prevention of aminoglycoside‐induced ototoxicity, they have not yet led to a clear understanding of the pathophysiology of aminoglycoside toxicity or the development of therapeutic options after the onset of symptoms.