Transplanted progenitors generate functional enteric neurons in the postnatal colon

Isolation of Enteric Nervous System Progenitor Cells from the Aganglionic Gut of Patients with Hirschsprung's Disease

Enteric nervous system progenitor cells isolated from postnatal human gut and cultured as neurospheres can then be transplanted into aganglionic gut to restore normal patterns of contractility. These progenitor cells may be of future use to treat patients with Hirschprung’s disease, a congenital condition characterized by hindgut dysmotility due to the lack of enteric nervous system ganglia. Here we demonstrate that progenitor cells can also be isolated from aganglionic gut removed during corrective surgery for Hirschsprung’s disease. Although the enteric nervous system marker calretinin is not expressed in the aganglionic gut region, de novo expression is initiated in cultured neurosphere cells isolated from aganglionic Hirschsprung bowel. Furthermore, expression of the neural markers NOS, VIP and GFAP also increased during culture of aganglionic gut neurospheres which we show can be transplantation into cultured embryonic mouse gut explants to restore a normal frequency of contractility. To determine the origin of the progenitor cells in aganglionic region, we used fluorescence-activated cell sorting to demonstrate that only p75-positive neural crest-derived cells present in the thickened nerve trunks characteristic of the aganglionic region of Hirschsprung gut gave rise to neurons in culture. The derivation of enteric nervous system progenitors in the aganglionic gut region of Hirschprung’s patients not only means that this tissue is a potential source of cells for future autologous transplantation, but it also raises the possibility of inducing the differentiation of these endogenous cells in situ to compensate for the aganglionosis.

The appendix as a viable source of neural progenitor cells to functionally innervate bioengineered gastrointestinal smooth muscle tissues

Appendix-derived neural progenitor cells (NPCs) have both neurogenic and gliogenic potential, but use of these cells for enteric neural cell therapy has not been addressed. The objective of this study was to determine whether NPCs obtained from the appendix would differentiate into enteric neural subsets capable of inducing neurotransmitter-mediated smooth muscle cell (SMC) contraction and relaxation. NPCs were isolated from the appendix and small intestine (SI) of rabbits. Bioengineered internal anal sphincter constructs were developed using the same source of smooth muscle and innervated with NPCs derived from either the appendix or SI. Innervated constructs were assessed for neuronal differentiation markers through Western blots and immunohistochemistry, and functionality was assessed through force-generation studies. Expression of neural and glial differentiation markers was observed in constructs containing appendix- and SI-derived NPCs. The addition of acetylcholine to both appendix and SI constructs caused a robust contraction that was decreased by pretreatment with the neural inhibitor tetrodotoxin (TTX). Electrical field stimulation caused relaxation of constructs that was completely abolished in the presence of TTX and significantly reduced on pretreatment with nitric oxide synthase inhibitor (Nω-nitro-l-arginine methyl ester hydrochloride [l-NAME]). These data indicate that in the presence of identical soluble factors arising from intestinal SMCs, enteric NPCs derived from the appendix and SI differentiate in a similar manner and are capable of responding to physiological stimuli. This coculture paradigm could be used to explore the nature of the soluble factors derived from SMCs and NPCs in generating specific functional innervations.

SIGNIFICANCE

This study demonstrates the ability of neural stem cells isolated from the appendix to differentiate into mature functional enteric neurons. The differentiation of neural stem cells from the appendix is similar to differentiation of neural stem cells derived from the gastrointestinal tract. The appendix is a vestigial organ that can be removed with minimal clinical consequence through laparoscopy. Results presented in this paper indicate that the appendix is a potential source of autologous neural stem cells required for cell therapy for the gastrointestinal tract.

Ion channel expression in the developing enteric nervous system

The enteric nervous system arises from neural crest-derived cells (ENCCs) that migrate caudally along the embryonic gut. The expression of ion channels by ENCCs in embryonic mice was investigated using a PCR-based array, RT-PCR and immunohistochemistry. Many ion channels, including chloride, calcium, potassium and sodium channels were already expressed by ENCCs at E11.5. There was an increase in the expression of numerous ion channel genes between E11.5 and E14.5, which coincides with ENCC migration and the first extension of neurites by enteric neurons. Previous studies have shown that a variety of ion channels regulates neurite extension and migration of many cell types. Pharmacological inhibition of a range of chloride or calcium channels had no effect on ENCC migration in cultured explants or neuritogenesis in vitro. The non-selective potassium channel inhibitors, TEA and 4-AP, retarded ENCC migration and neuritogenesis, but only at concentrations that also resulted in cell death. In summary, a large range of ion channels is expressed while ENCCs are colonizing the gut, but we found no evidence that ENCC migration or neuritogenesis requires chloride, calcium or potassium channel activity. Many of the ion channels are likely to be involved in the development of electrical excitability of enteric neurons.

Enteric neurospheres are not specific to neural crest cultures: implications for neural stem cell therapies

Objectives

Enteric neural stem cells provide hope of curative treatment for enteric neuropathies. Current protocols for their harvesting from humans focus on the generation of ‘neurospheres’ from cultures of dissociated gut tissue. The study aims to better understand the derivation, generation and composition of enteric neurospheres.

Design

Gut tissue was obtained from Wnt1-Cre;Rosa26^Yfp/Yfp transgenic mice (constitutively labeled neural crest cells) and paediatric patients. Gut cells were cultured either unsorted (mixed neural crest/non-neural crest), or following FACS selection into neural crest (murine-YFP+ve/human-p75+ve) or non-neural crest (YFP-ve/p75-ve) populations. Cultures and resultant neurospheres were characterized using immunolabelling in vitro and following transplantation in vivo.

Results

Cultures of (i) unsorted, (ii) neural crest, and (iii) non-neural crest cell populations generated neurospheres similar in numbers, size and morphology. Unsorted neurospheres were highly heterogeneous for neural crest content. Neural crest-derived (YFP+ve/p75+ve) neurospheres contained only neural derivatives (neurons and glia) and were devoid of non-neural cells (i.e. negative for SMA, c-Kit), with the converse true for non-neural crest-derived (YFP-ve/p75-ve) ‘neurospheres’. Under differentiation conditions only YFP+ve cells gave rise to neural derivatives. Both YFP+ve and YFP-ve cells displayed proliferation and spread upon transplantation in vivo, but YFP-ve cells did not locate or integrate within the host ENS.

Conclusions

Spherical accumulations of cells, so-called ‘neurospheres’ forming in cultures of dissociated gut contain variable proportions of neural crest-derived cells. If they are to be used for ENS cell replacement therapy then improved protocols for their generation, including cell selection, should be sought in order to avoid inadvertent transplantation of non-therapeutic, non-ENS cells.

Building a second brain in the bowel

The enteric nervous system (ENS) is sometimes called the "second brain" because of the diversity of neuronal cell types and complex, integrated circuits that permit the ENS to autonomously regulate many processes in the bowel. Mechanisms supporting ENS development are intricate, with numerous proteins, small molecules, and nutrients that affect ENS morphogenesis and mature function. Damage to the ENS or developmental defects cause vomiting, abdominal pain, constipation, growth failure, and early death. Here, we review molecular mechanisms and cellular processes that govern ENS development, identify areas in which more investigation is needed, and discuss the clinical implications of new basic research.

Skin-derived precursors generate enteric-type neurons in aganglionic jejunum

PURPOSE

Skin-derived precursor cells (SKPs) may regenerate the enteric nervous system in Hirschsprung's disease. SKPs migrate and differentiate into myenteric ganglia in aganglionic intestine. We sought to characterize the time-course of SKP gangliogenesis and enteric neurotransmitter synthesis in vivo.

METHODS

Adult Lewis rat jejunal segments were isolated and denervated with benzalkonium chloride (BAC). Denervation was evaluated by immunohistochemical (IHC) stains for markers of mature neuronal and glial cells. Green fluorescent protein (GFP)-expressing neonatal rat SKPs were cultured in neuroglial-selective medium. SKPs were transplanted into aganglionic segments 65-85days after BAC treatment. IHC was performed to identify glia, neurons, and neurotransmitter synthesis in GFP+cells between post-transplant days 1 and 28.

RESULTS

Aganglionosis was confirmed by IHC. On post-transplant days 1 and 2, GFP+cells were detected near injection sites within the muscularis propria. GFP+cell clusters were evident only between longitudinal and circular smooth muscle layers at post-transplant days 14, 21, and 28. These structures co-expressed markers of mature neurons and gliocytes. Several markers of neurotransmitter synthesis were detected in GFP+clusters at days 21 and 28.

CONCLUSION

SKPs are capable of enteric neuroglial differentiation in vivo. SKPs migrate to the intermuscular layer of aganglionic intestine within days of transplantation. Our observations suggest that SKPs are capable of generating enteric ganglia in aganglionic intestine.

Lentiviral labeling of mouse and human enteric nervous system stem cells for regenerative medicine studies

BACKGROUND

Reliable methods of labeling human enteric nervous system (ENS) stem cells for use in novel cell replacement therapies for enteric neuropathies are lacking. Here, we explore the possibility of using lentiviral vectors expressing fluorescent reporter genes to transduce, label, and trace mouse and human ENS stem cells following transplantation into mouse gut.

METHODS

Enteric nervous system precursors, including ENS stem cells, were isolated from enzymatically dissociated mouse and human gut tissues. Lentivirus containing eGFP or mCherry fluorescent reporter genes was added to gut cell cultures at a multiplicity of infection of 2-5. After fluorescence activated cell sorting for eGFP and subsequent analysis with markers of proliferation and cell phenotype, transduced mouse and human cells were transplanted into the gut of C57BL/6 and immune deficient Rag2-/gamma chain-/C5 mice, respectively and analyzed up to 60 days later.

KEY RESULTS

Mouse and human transduced cells survived in vitro, maintained intense eGFP expression, proliferated as shown by BrdU incorporation, and formed characteristic neurospheres. When transplanted into mouse gut in vivo and analyzed up to 2 months later, transduced mouse and human cells survived, strongly expressed eGFP and integrated into endogenous ENS networks.

CONCLUSIONS & INFERENCES

Lentiviral vectors expressing fluorescent reporter genes enable efficient, stable, long-term labeling of ENS stem cells when transplanted into in vivo mouse gut. This lentiviral approach not only addresses the need for a reliable fluorescent marker of human ENS stem cells for preclinical studies, but also raises the possibility of using lentiviruses for other applications, such as gene therapy.

Enteric neural progenitors are more efficient than brain-derived progenitors at generating neurons in the colon

Gut motility disorders can result from an absent, damaged, or dysfunctional enteric nervous system (ENS). Cell therapy is an exciting prospect to treat these enteric neuropathies and restore gut motility. Previous studies have examined a variety of sources of stem/progenitor cells, but the ability of different sources of cells to generate enteric neurons has not been directly compared. It is important to identify the source of stem/progenitor cells that is best at colonizing the bowel and generating neurons following transplantation. The aim of this study was to compare the ability of central nervous system (CNS) progenitors and ENS progenitors to colonize the colon and differentiate into neurons. Genetically labeled CNS- and ENS-derived progenitors were cocultured with aneural explants of embryonic mouse colon for 1 or 2.5 wk to assess their migratory, proliferative, and differentiation capacities, and survival, in the embryonic gut environment. Both progenitor cell populations were transplanted in the postnatal colon of mice in vivo for 4 wk before they were analyzed for migration and differentiation using immunohistochemistry. ENS-derived progenitors migrated further than CNS-derived cells in both embryonic and postnatal gut environments. ENS-derived progenitors also gave rise to more neurons than their CNS-derived counterparts. Furthermore, neurons derived from ENS progenitors clustered together in ganglia, whereas CNS-derived neurons were mostly solitary. We conclude that, within the gut environment, ENS-derived progenitors show superior migration, proliferation, and neuronal differentiation compared with CNS progenitors.

Cell reconstruction of the rectal mucosa in patients with familial adenomatous polyposis: endoscopy, morphology, immunohistochemistry

We propose a new surgical approach to the treatment of familial colorectal adenomatous polyposis implying preservation of a portion of the rectum with removed mucosa. For reconstruction of the rectum, allotransplantation of the mixed culture of fetal allogenic somatic cells of the intestinal epithelium and mesenchymal cells of various origin is used. The mechanisms of mucosa reparation were studied in 34 patients. Endoscopic, morphological, and immunohistochemical studies showed that cell transplantation considerably accelerated reparation of the mucosa in mucosectomized rectum. The proposed treatment of familial colorectal adenomatous polyposis allows delaying the development of rectal polyps and cancer for many years.

Migration and differentiation of transplanted enteric neural crest-derived cells in murine model of Hirschsprung's disease

Stem cell therapy offers the potential of rebuilding the enteric nervous system (ENS) in the aganglionic bowel of patients with Hirschsprung's disease. P0-Cre/Floxed-EGFP mice in which neural crest-derived cells express EGFP were used to obtain ENS stem/progenitor cells. ENS stem/progenitor cells were transplanted into the bowel of Ret(-/-) mouse, an animal model of Hirschsprung's disease. Immunohistochemical analysis was performed to determine whether grafted cells gave rise to neurons in the recipient bowel. EGFP expressing neural crest-derived cells accounted for 7.01 ± 2.52 % of total cells of gastrointestinal tract. ENS stem/progenitor cells were isolated using flow cytometry and expanded as neurosphere-like bodies (NLBs) in a serum-free culture condition. Some cells in NLBs expressed neural crest markers, p75 and Sox10 and neural stem/progenitor cells markers, Nestin and Musashi1. Multipotency of isolated ENS stem/progenitor cells was determined as they differentiated into neurons, glial cells, and myofibloblasts in culture. When co-cultured with explants of hindgut of Ret(-/-) mice, ENS stem/progenitor cells migrated into the aganglionic bowel and gave rise to neurons. ENS stem/progenitor cells used in this study appear to be clinically relevant donor cells in cell therapy to treat Hirschsprung's disease capable of colonizing the affected bowel and giving rise to neurons.

The neural crest: a versatile organ system

The neural crest is the name given to the strip of cells at the junction between neural and epidermal ectoderm in neurula-stage vertebrate embryos, which is later brought to the dorsal neural tube as the neural folds elevate. The neural crest is a heterogeneous and multipotent progenitor cell population whose cells undergo EMT then extensively and accurately migrate throughout the embryo. Neural crest cells contribute to nearly every organ system in the body, with derivatives of neuronal, glial, neuroendocrine, pigment, and also mesodermal lineages. This breadth of developmental capacity has led to the neural crest being termed the fourth germ layer. The neural crest has occupied a prominent place in developmental biology, due to its exaggerated migratory morphogenesis and its remarkably wide developmental potential. As such, neural crest cells have become an attractive model for developmental biologists for studying these processes. Problems in neural crest development cause a number of human syndromes and birth defects known collectively as neurocristopathies; these include Treacher Collins syndrome, Hirschsprung disease, and 22q11.2 deletion syndromes. Tumors in the neural crest lineage are also of clinical importance, including the aggressive melanoma and neuroblastoma types. These clinical aspects have drawn attention to the selection or creation of neural crest progenitor cells, particularly of human origin, for studying pathologies of the neural crest at the cellular level, and also for possible cell therapeutics. The versatility of the neural crest lends itself to interlinked research, spanning basic developmental biology, birth defect research, oncology, and stem/progenitor cell biology and therapy.

Transplanted skin-derived precursor stem cells generate enteric ganglion-like structures in vivo

INTRODUCTION

Hirschsprung's disease is characterized by a developmental arrest of neural crest cell migration, causing distal aganglionosis. Transplanted cells derived from the neural crest may regenerate enteric ganglia in this condition. We investigated the potential of skin-derived precursor cells (SKPs) to engraft and to differentiate into enteric ganglia in aganglionic rat intestine in vivo.

METHODS

Adult Lewis rat jejunal segments were separated from intestinal continuity and treated with benzalkonium chloride to induce aganglionosis. Ganglia were identified via immunohistochemical stains for S100 and β-III tubulin (TUJ1). SKPs were procured from neonatal Lewis rats expressing enhanced green fluorescent protein (GFP) and cultured in neuroglial-selective media. SKP cell line expansion was quantified, and immunophenotypes were assessed by immunocytochemistry. Aganglionic segments underwent SKP transplantation 21-79days after benzalkonium chloride treatment. The presence of GFP+cells, mature neurons, and mature glia was evaluated at posttransplant days 1, 6, and 9.

RESULTS

Benzalkonium chloride-induced aganglionosis persisted for at least 85days. Prior to differentiation, SKPs expressed S100, denoting neural crest lineage, and nestin, a marker of neuronal precursors. Differentiated SKPs in vitro expressed GFAP, a marker of glial differentiation, as well as TUJ1 and several enteric neurotransmitters. After transplantation, GFP+structures resembling ganglia were identified between longitudinal and circular smooth muscle layers.

CONCLUSION

SKPs are capable of engraftment, migration, and differentiation within aganglionic rodent intestine in vivo. Differentiated SKPs generate structures that resemble enteric ganglia. Our observations suggest that SKPs represent a potential gangliogenic therapeutic agent for Hirschsprung's disease.

The influence of extracellular matrix composition on the differentiation of neuronal subtypes in tissue engineered innervated intestinal smooth muscle sheets

Differentiation of enteric neural stem cells into several appropriate neural phenotypes is crucial while considering transplantation as a cellular therapy to treat enteric neuropathies. We describe the formation of tissue engineered innervated sheets, where intestinal smooth muscle and enteric neuronal progenitor cells are brought into close association in extracellular matrix (ECM) based microenvironments. Uniaxial alignment of constituent smooth muscle cells was achieved by substrate microtopography. The smooth muscle component of the tissue engineered sheets maintained a contractile phenotype irrespective of the ECM composition, and generated equivalent contractions in response to potassium chloride stimulation, similar to native intestinal tissue. We provided enteric neuronal progenitor cells with permissive ECM-based compositional and viscoelastic cues to generate excitatory and inhibitory neuronal subtypes. In the presence of the smooth muscle cells, the enteric neuronal progenitor cells differentiated to functionally innervate the smooth muscle. The differentiation of specific neuronal subtypes was influenced by the ECM microenvironment, namely combinations of collagen I, collagen IV, laminin and/or heparan sulfate. The physiology of differentiated neurons within tissue engineered sheets was evaluated. Sheets with composite collagen and laminin had the most similar patterns of Acetylcholine-induced contraction to native intestinal tissue, corresponding to an increased protein expression of choline acetyltransferase. An enriched nitrergic neuronal population, evidenced by an increased expression of neuronal nitric oxide synthase, was obtained in tissue engineered sheets that included collagen IV. These sheets had a significantly increased magnitude of electrical field stimulated relaxation, sensitive maximally to nitric oxide synthase inhibition. Tissue engineered sheets containing laminin and/or heparan sulfate had a balanced expression of contractile and relaxant motor neurons. Our studies demonstrated that neuronal subtype was modulated by varying ECM composition. This observation could be utilized to derive enriched populations of specific enteric neurons in vitro prior to transplantation.

Tissue engineering in the gut: developments in neuromusculature

The complexity of the gastrointestinal (GI) tract lies in its anatomy as well as in its physiology. Several different cell types populate the GI tract, adding to the complexity of cell sourcing for regenerative medicine. Each cell layer has a specialized function in mediating digestion, absorption, secretion, motility, and excretion. Tissue engineering and regenerative medicine aim to regenerate the specific layers mimicking architecture and recapitulating function. Gastrointestinal motility is the underlying program that mediates the diverse functions of the intestines, as an organ. Hence, the first logical step in GI regenerative medicine is the reconstruction of the tubular smooth musculature along with the drivers of their input, the enteric nervous system. Recent advances in the field of GI tissue engineering have focused on the use of scaffolding biomaterials in combination with cells and bioactive factors. The ability to innervate the bioengineered muscle is a critical step to ensure proper functionality. Finally, in vivo studies are essential to evaluate implant integration with host tissue, survival, and functionality. In this review, we focus on the tubular structure of the GI tract, tools for innervation, and, finally, evaluation of in vivo strategies for GI replacements.

Isolation, expansion and transplantation of postnatal murine progenitor cells of the enteric nervous system

Neural stem or progenitor cells have been proposed to restore gastrointestinal function in patients suffering from congenital or acquired defects of the enteric nervous system. Various, mainly embryonic cell sources have been identified for this purpose. However, immunological and ethical issues make a postnatal cell based therapy desirable. We therefore evaluated and quantified the potential of progenitor cells of the postnatal murine enteric nervous system to give rise to neurons and glial cells in vitro. Electrophysiological analysis and BrdU uptake studies provided direct evidence that generated neurons derive from expanded cells in vitro. Transplantation of isolated and expanded postnatal progenitor cells into the distal colon of adult mice demonstrated cell survival for 12 weeks (end of study). Implanted cells migrated within the gut wall and differentiated into neurons and glial cells, both of which were shown to derive from proliferated cells by BrdU uptake. This study indicates that progenitor cells isolated from the postnatal enteric nervous system might have the potential to serve as a source for a cell based therapy for neurogastrointestinal motility disorders. However, further studies are necessary to provide evidence that the generated cells are capable to positively influence the motility of the diseased gastrointestinal tract.

Neural stem cell therapies for enteric nervous system disorders

The enteric nervous system is vulnerable to a range of congenital and acquired disorders that disrupt the function of its neurons or lead to their loss. The resulting enteric neuropathies are some of the most challenging clinical conditions to manage. Neural stem cells offer the prospect of a cure given their potential ability to replenish missing or dysfunctional neurons. This article discusses diseases that might be targets for stem cell therapies and the barriers that could limit treatment application. We explore various sources of stem cells and the proof of concept for their use. The critical steps that remain to be addressed before these therapies can be used in patients are also discussed. Key milestones include the harvesting of neural stem cells from the human gut and the latest in vivo transplantation studies in animals. The tremendous progress in the field has brought experimental studies exploring the potential of stem cell therapies for the management of enteric neuropathies to the cusp of clinical application.

Transplantation of enteric neural stem/progenitor cells into the irradiated young mouse hippocampus

Radiotherapy is an effective treatment for brain tumors but often results in cognitive deficits in survivors. Transplantation of embryonic or brain-derived neural stem/progenitor cells (BNSPCs) ameliorated cognitive impairment after irradiation (IR) in animal models. However, such an approach in patients requires a clinically relevant source of cells. We show for the first time the utilization of enteric neural stem/progenitor cells (ENSPCs) from the postnatal intestinal wall as a source of autologous cells for brain repair after injury caused by IR. Cells were isolated from the intestinal wall and propagated in vitro for 1 week. Differentiation assays showed that ENSPCs are multipotent and generated neurons, astrocytes, and myofibroblasts. To investigate whether ENSPCs can be used in vivo, postnatal day 9 mice were subjected to a single moderate irradiation dose (6 or 8 Gy). Twelve days later, mice received an intrahippocampal injection of syngeneic ENSPCs. Four weeks after transplantation, 0.5% and 1% of grafted ENSPCs were detected in the dentate gyrus of sham and irradiated animals, respectively, and only 0.1% was detected after 16 weeks. Grafted ENSPCs remained undifferentiated but failed to restore IR-induced loss of BNSPCs and the subsequent impaired growth of the dentate gyrus. We observed microglia activation, astrogliosis, and loss of granule neurons associated with grafted ENSPC clusters. Transplantation of ENSPCs did not ameliorate IR-induced impaired learning and memory. In summary, while autologous ENSPC grafting to the brain worked technically, even in the absence of immunosuppression, the protocols need to be modified to improve survival and integration.

A novel bidirectional interaction between endothelin-3 and retinoic acid in rat enteric nervous system precursors

BACKGROUND

Signaling through the endothelin receptor B (EDNRB) is critical for the development of the enteric nervous system (ENS) and mutations in endothelin system genes cause Hirschsprung's aganglionosis in humans. Penetrance of the disease is modulated by other genetic factors. Mutations affecting retinoic acid (RA) signaling also produce aganglionosis in mice. Thus, we hypothesized that RA and endothelin signaling pathways may interact in controlling development of the ENS.

METHODS

Rat immunoselected ENS precursor cells were cultured with the EDNRB ligand endothelin-3, an EDNRB-selective antagonist (BQ-788), and/or RA for 3 or 14 days. mRNA levels of genes related to ENS development, RA- and EDNRB-signaling were measured at 3 days. Proliferating cells and cells expressing neuronal, glial, and myofibroblast markers were quantified.

RESULTS

Culture of isolated ENS precursors for 3 days with RA decreases expression of the endothelin-3 gene and that of its activation enzyme. These changes are associated with glial proliferation, a higher percentage of glia, and a lower percentage of neurons compared to cultures without RA. These changes are independent of EDNRB signaling. Conversely, EDNRB activation in these cultures decreases expression of RA receptors β and γ mRNA and affects the expression of the RA synthetic and degradative enzymes. These gene expression changes are associated with reduced glial proliferation and a lower percentage of glia in the culture. Over 14 days in the absence of EDNRB signaling, RA induces the formation of a heterocellular plexus replete with ganglia, glia and myofibroblasts.

CONCLUSIONS

A complex endothelin-RA interaction exists that coordinately regulates the development of rat ENS precursors in vitro. These results suggest that environmental RA may modulate the expression of aganglionosis in individuals with endothelin mutations.

Enteric neural crest-derived cells promote their migration by modifying their microenvironment through tenascin-C production

The enteric nervous system (ENS) is derived from vagal and sacral neural crest cells that migrate, proliferate, and differentiate into enteric neurons and glia within the gut wall. The mechanisms regulating enteric neural crest-derived cell (ENCC) migration are poorly characterized despite the importance of this process in gut formation and function. Characterization of genes involved in ENCC migration is essential to understand ENS development and could provide targets for treatment of human ENS disorders. We identified the extracellular matrix glycoprotein tenascin-C (TNC) as an important regulator of ENCC development. We find TNC dynamically expressed during avian gut development. It is absent from the cecal region just prior to ENCC arrival, but becomes strongly expressed around ENCCs as they enter the ceca and hindgut. In aganglionic hindguts, TNC expression is strong throughout the outer mesenchyme, but is absent from the submucosal region, supporting the presence of both ENCC-dependent and independent expression within the gut wall. Using rat-chick coelomic grafts, neural tube cultures, and gut explants, we show that ENCCs produce TNC and that this ECM protein promotes their migration. Interestingly, only vagal neural crest-derived ENCCs express TNC, whereas sacral neural crest-derived cells do not. These results demonstrate that vagal crest-derived ENCCs actively modify their microenvironment through TNC expression and thereby help to regulate their own migration.

In vitro culture and characterization of enteric neural precursor cells from human gut biopsy specimens using polymer scaffold

In vitro expansion and characterization of neural precursor cells from human gut biopsy specimens with or without Hirschsprung's disease using a novel thermoreversible gelation polymer (TGP) is reported aiming at a possible future treatment. Gut biopsy samples were obtained from five patients undergoing gut resection for Hirschsprung's disease (n = 1) or gastrointestinal disorders (n = 4). Cells isolated from the smooth muscle layer and the myenteric plexus were cultured in two groups for 18 to 28 days; Group I: conventional culture as earlier reported and Group II: using TGP scaffold. Neurosphere like bodies (NLBs) were observed in the cultures between 8th to 12th day and H & E staining was positive for neural cells in both groups including aganglionic gut portion from the Hirschsprung's disease patient. Immunohistochemistry using S-100 and neuron specific enolase (NSE) was positive in both groups but the TGP group (Group II) showed more number of cells with intense cytoplasmic granular positivity for both NSE and S-100 compared to Group I. TGP supports the in vitro expansion of human gut derived neuronal cells with seemingly better quality NLBs. Animal Studies can be tried to validate their functional outcome by transplanting the NLBs with TGP scaffolds to see whether this can enhance the outcome of cell based therapies for Hirschsprung's disease.