Cultured nestin-positive cells from postnatal mouse small bowel differentiate ex vivo into neurons, glia, and smooth muscle

Phosphatase and Tensin Homolog Inhibition in Proteolipid Protein 1-Expressing Cells Stimulates Neurogenesis and Gliogenesis in the Postnatal Enteric Nervous System

Phosphatase and tensin homolog (Pten) is a key regulator of cell proliferation and a potential target to stimulate postnatal enteric neuro- and/or gliogenesis. To investigate this, we generated two tamoxifen-inducible Cre recombinase murine models in which Pten was conditionally ablated, (1) in glia (Plp1-expressing cells) and (2) in neurons (Calb2-expressing cells). Tamoxifen-treated adult (7-12 weeks of age; n = 4-15) mice were given DSS to induce colitis, EdU to monitor cell proliferation, and were evaluated at two timepoints: (1) early (3-4 days post-DSS) and (2) late (3-4 weeks post-DSS). We investigated gut motility and evaluated the enteric nervous system. Pten inhibition in Plp1-expressing cells elicited gliogenesis at baseline and post-DSS (early and late) in the colon, and neurogenesis post-DSS late in the proximal colon. They also exhibited an increased frequency of colonic migrating motor complexes (CMMC) and slower whole gut transit times. Pten inhibition in Calb2-expressing cells did not induce enteric neuro- or gliogenesis, and no alterations were detected in CMMC or whole gut transit times when compared to the control at baseline or post-DSS (early and late). Our results merit further research into Pten modulation where increased glia and/or slower intestinal transit times are desired (e.g., short-bowel syndrome and rapid-transit disorders).

L-Fucose promotes enteric nervous system regeneration in type 1 diabetic mice by inhibiting SMAD2 signaling pathway in enteric neural precursor cells

BACKGROUND

Diabetes can lead to extensive damage to the enteric nervous system (ENS), causing gastrointestinal motility disorders. However, there is currently a lack of effective treatments for diabetes-induced ENS damage. Enteric neural precursor cells (ENPCs) closely regulate the structural and functional integrity of the ENS. L-Fucose, is a dietary sugar that has been showed to effectively ameliorate central nervous system injuries, but its potential for ameliorating ENS damage and the involvement of ENPCs in this process remains uncertain.

METHODS

Genetically engineered mice were generated for lineage tracing of ENPCs in vivo. Using diabetic mice in vivo and high glucose-treated primary ENPCs in vitro, the effects of L-Fucose on the injured ENS and ENPCs was evaluated by assessing gastrointestinal motility, ENS structure, and the differentiation of ENPCs. The key signaling pathways in regulating neurogenesis and neural precursor cells properties, transforming growth factor-β (TGF-β) and its downstream signaling pathways were further examined to clarify the potential mechanism of L-Fucose on the injured ENS and ENPCs.

RESULTS

L-Fucose improved gastrointestinal motility in diabetic mice, including increased defecation frequency (p < 0.05), reduced total gastrointestinal transmission time (p < 0.001) and bead expulsion time (p < 0.05), as well as enhanced spontaneous contractility and electric field stimulation-induced contraction response in isolated colonic muscle strips (p < 0.001). The decrease in the number of neurons and glial cells in the ENS of diabetic mice were reversed by L-Fucose treatment. More importantly, L-Fucose treatment significantly promoted the proportion of ENPCs differentiated into neurons and glial cells both in vitro and in vivo, accompanied by inhibiting SMAD2 phosphorylation.

CONCLUSIONS

L-Fucose could promote neurogenesis and gliogenesis derived from ENPCs by inhibiting the SMAD2 signaling, thus facilitating ENS regeneration and gastrointestinal motility recovery in type 1 diabetic mice. Video Abstract.

Harnessing the Power of Enteric Glial Cells' Plasticity and Multipotency for Advancing Regenerative Medicine

The enteric nervous system (ENS), known as the intrinsic nervous system of the gastrointestinal tract, is composed of a diverse array of neuronal and glial cell subtypes. Fascinating questions surrounding the generation of cellular diversity in the ENS have captivated ENS biologists for a considerable time, particularly with recent advancements in cell type-specific transcriptomics at both population and single-cell levels. However, the current focus of research in this field is predominantly restricted to the study of enteric neuron subtypes, while the investigation of enteric glia subtypes significantly lags behind. Despite this, enteric glial cells (EGCs) are increasingly recognized as equally important regulators of numerous bowel functions. Moreover, a subset of postnatal EGCs exhibits remarkable plasticity and multipotency, distinguishing them as critical entities in the context of advancing regenerative medicine. In this review, we aim to provide an updated overview of the current knowledge on this subject, while also identifying key questions that necessitate future exploration.

A fast and efficient method for isolating and culturing enteric neural precursor cells from adult mouse colon

BACKGROUND

The enteric neural precursor cells (ENPCs) are important for researching the pathogenesis of enteric nervous system (ENS)-related diseases, especially in adulthood. Because primary ENPCs are difficult to isolate and survive, easy to contaminate and low-yielding, a rapid and effective method to isolate and cultivate ENPCs from adult mice is necessary.

NEW METHODS

The longitudinal muscle myenteric plexus (LMMP) was isolated from the adult mouse colon. The papain and collagenase Ⅱ were chosen to increase the yield of ENPCs. The growth and proliferation of ENPCs could be promoted by using polylysine precoated culture plates and reasonable cell seeding density. The ENPCs were identified by Nestin and the proliferative properties were verified by EDU. The transgenic Nestin-cre:tdTomato mice were used to observe the proliferation of ENPCs more intuitively in vitro.

RESULTS

Our method to isolate the ENPCs from adult mouse colon was effective and high-yielding. The ENPCs were identified as Nestin positive. The Nestin-positive ENPCs could proliferate rapidly and had a tendency to differentiate into neurons and glial cells in vitro without any inducing factors.

COMPARISON WITH EXISTING METHODS

Previous studies about the ENPCs focused on experiment in vivo or were limited to the embryonic mice, and had limitations of low yield and long experiment time. The ENPCs from adult mice were isolated quickly by our method, and had a high yield and purity.

CONCLUSION

We described a rapid, efficient, step by step method for isolation and culture of ENPCs from the adult mouse colon, which was simple and obtained high yield of ENPCs.

BMSCs Promote Differentiation of Enteric Neural Precursor Cells to Maintain Neuronal Homeostasis in Mice With Enteric Nerve Injury

BACKGROUND & AIMS

Our previous study showed that transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) promoted functional enteric nerve regeneration in denervated mice but not through direct transdifferentiation. Homeostasis of the adult enteric nervous system (ENS) is maintained by enteric neural precursor cells (ENPCs). Whether ENPCs are a source of regenerated nerves in denervated mice remains unknown.

METHODS

Genetically engineered mice were used as recipients, and ENPCs were traced during enteric nerve regeneration. The mice were treated with benzalkonium chloride to establish a denervation model and then transplanted with BMSCs 3 days later. After 28 days, the gastric motility and ENS regeneration were analyzed. The interaction between BMSCs and ENPCs in vitro was further assessed.

RESULTS

Twenty-eight days after transplantation, gastric motility recovery (gastric emptying capacity, P < .01; gastric contractility, P < .01) and ENS regeneration (neurons, P < .01; glial cells, P < .001) were promoted in BMSCs transplantation groups compared with non-transplanted groups in denervated mice. More importantly, we found that ENPCs could differentiate into enteric neurons and glial cells in denervated mice after BMSCs transplantation, and the proportion of Nestin⁺/Ngfr⁺ cells differentiated into neurons was significantly higher than that of Nestin⁺ cells. A small number of BMSCs located in the myenteric plexus differentiated into glial cells. In vitro, glial cell-derived neurotrophic factor (GDNF) from BMSCs promotes the migration, proliferation, and differentiation of ENPCs.

CONCLUSIONS

In the case of enteric nerve injury, ENPCs can differentiate into enteric neurons and glial cells to promote ENS repair and gastric motility recovery after BMSCs transplantation. BMSCs expressing GDNF enhance the migration, proliferation, and differentiation of ENPCs.

Enteric Neural Network Assembly Was Promoted by Basic Fibroblast Growth Factor and Vitamin A but Inhibited by Epidermal Growth Factor

Extending well beyond the original use of propagating neural precursors from the central nervous system and dorsal root ganglia, neurosphere medium (NSM) and self-renewal medium (SRM) are two distinct formulas with widespread popularity in enteric neural stem cell (ENSC) applications. However, it remains unknown what growth factors or nutrients are crucial to ENSC development, let alone whether the discrepancy in their components may affect the outcomes of ENSC culture. Dispersed enterocytes from murine fetal gut were nurtured in NSM, SRM or their modifications by selective component elimination or addition to assess their effects on ENSC development. NSM generated neuriteless neurospheres, whereas SRM, even deprived of chicken embryo extract, might wire ganglia together to assemble neural networks. The distinct outcomes came from epidermal growth factor, which inhibited enteric neuronal wiring in NSM. In contrast, basic fibroblast growth factor promoted enteric neurogenesis, gangliogenesis, and neuronal wiring. Moreover, vitamin A derivatives might facilitate neuronal maturation evidenced by p75 downregulation during ENSC differentiation toward enteric neurons to promote gangliogenesis and network assembly. Our results might help to better manipulate ENSC propagation and differentiation in vitro, and open a new avenue for the study of enteric neuronal neuritogenesis and synaptogenesis.

The gut brain in a dish: Murine primary enteric nervous system cell cultures

BACKGROUND

The enteric nervous system (ENS) is an extensive neural network embedded in the wall of the gastrointestinal tract that regulates digestive function and gastrointestinal homeostasis. The ENS consists of two main cell types; enteric neurons and enteric glial cells. In vitro techniques allow simplified investigation of ENS function, and different culture methods have been developed over the years helping to understand the role of ENS cells in health and disease.

PURPOSE

This review focuses on summarizing and comparing available culture protocols for the generation of primary ENS cells from adult mice, including dissection of intestinal segments, enzymatic digestions, surface coatings, and culture media. In addition, the potential of human ENS cultures is also discussed.

Intestinal microbiota shapes gut physiology and regulates enteric neurons and glia

BACKGROUND

The intestinal microbiota plays an important role in regulating gastrointestinal (GI) physiology in part through interactions with the enteric nervous system (ENS). Alterations in the gut microbiome frequently occur together with disturbances in enteric neural control in pathophysiological conditions. However, the mechanisms by which the microbiota regulates GI function and the structure of the ENS are incompletely understood. Using a mouse model of antibiotic (Abx)-induced bacterial depletion, we sought to determine the molecular mechanisms of microbial regulation of intestinal function and the integrity of the ENS. Spontaneous reconstitution of the Abx-depleted microbiota was used to assess the plasticity of structure and function of the GI tract and ENS. Microbiota-dependent molecular mechanisms of ENS neuronal survival and neurogenesis were also assessed.

RESULTS

Adult male and female Abx-treated mice exhibited alterations in GI structure and function, including a longer small intestine, slower transit time, increased carbachol-stimulated ion secretion, and increased intestinal permeability. These alterations were accompanied by the loss of enteric neurons in the ileum and proximal colon in both submucosal and myenteric plexuses. A reduction in the number of enteric glia was only observed in the ileal myenteric plexus. Recovery of the microbiota restored intestinal function and stimulated enteric neurogenesis leading to increases in the number of enteric glia and neurons. Lipopolysaccharide (LPS) supplementation enhanced neuronal survival alongside bacterial depletion, but had no effect on neuronal recovery once the Abx-induced neuronal loss was established. In contrast, short-chain fatty acids (SCFA) were able to restore neuronal numbers after Abx-induced neuronal loss, demonstrating that SCFA stimulate enteric neurogenesis in vivo.

CONCLUSIONS

Our results demonstrate a role for the gut microbiota in regulating the structure and function of the GI tract in a sex-independent manner. Moreover, the microbiota is essential for the maintenance of ENS integrity, by regulating enteric neuronal survival and promoting neurogenesis. Molecular determinants of the microbiota, LPS and SCFA, regulate enteric neuronal survival, while SCFA also stimulates neurogenesis. Our data reveal new insights into the role of the gut microbiota that could lead to therapeutic developments for the treatment of enteric neuropathies. Video abstract.

Neuron-Glia Interaction in the Developing and Adult Enteric Nervous System

The enteric nervous system (ENS) constitutes the largest part of the peripheral nervous system. In recent years, ENS development and its neurogenetic capacity in homeostasis and allostasishave gained increasing attention. Developmentally, the neural precursors of the ENS are mainly derived from vagal and sacral neural crest cell portions. Furthermore, Schwann cell precursors, as well as endodermal pancreatic progenitors, participate in ENS formation. Neural precursorsenherite three subpopulations: a bipotent neuron-glia, a neuronal-fated and a glial-fated subpopulation. Typically, enteric neural precursors migrate along the entire bowel to the anal end, chemoattracted by glial cell-derived neurotrophic factor (GDNF) and endothelin 3 (EDN3) molecules. During migration, a fraction undergoes differentiation into neurons and glial cells. Differentiation is regulated by bone morphogenetic proteins (BMP), Hedgehog and Notch signalling. The fully formed adult ENS may react to injury and damage with neurogenesis and gliogenesis. Nevertheless, the origin of differentiating cells is currently under debate. Putative candidates are an embryonic-like enteric neural progenitor population, Schwann cell precursors and transdifferentiating glial cells. These cells can be isolated and propagated in culture as adult ENS progenitors and may be used for cell transplantation therapies for treating enteric aganglionosis in Chagas and Hirschsprung's diseases.

Early Expression of Neuronal Dopaminergic Markers in a Parkinson's Disease Model in Rats Implanted with Enteric Stem Cells (ENSCs)

BACKGROUND

Parkinson's Disease (PD) is a common neurodegenerative disorder affecting the dopaminergic (DAergic) system. Replacement therapy is a promising alternative aimed at reconstructing the cytoarchitecture of affected brain regions in PD. Experimental approaches, such as the replacement of DAergic neurons with cells obtained from the Enteric Nervous System (ENS) has yet to be explored.

OBJECTIVE

To establish and characterize a cell replacement strategy with ENS Cells (ENSCs) in a PD model in rats.

METHODS

Since ENSCs can develop mature DAergic phenotypes, here we cultured undifferentiated cells from the myenteric plexus of newborn rats, establishing that they exhibit multipotential characteristics. These cells were characterized and further implanted in the Substantia nigra pars compacta (SNpc) of adult rats previously lesioned by a retrograde degenerative model produced by intrastriatal injection of 6-Hydroxydopamine (6-OHDA). DAergic markers were assessed in implants to validate their viability and possible differentiation once implanted.

RESULTS

Cell cultures were viable, exhibited stem cell features and remained partially undifferentiated until the time of implant. The retrograde lesion induced by 6-OHDA produced DAergic denervation, reducing the number of fibers and cells in the SNpc. Implantation of ENSCs in the SNpc of 6-OHDAlesioned rats was tracked after 5 and 10 days post-implant. During that time, the implant increased selective neuronal and DAergic markers, Including Microtubule-Associated Protein 2 (MAP-2), Dopamine Transporter (DAT), and Tyrosine Hydroxylase (TH).

CONCLUSION

Our novel results suggest that ENSCs possess a differentiating, proliferative and restorative potential that may offer therapeutic modalities to attenuate neurodegenerative events with the inherent demise of DAergic neurons.

Postnatal human enteric neurospheres show a remarkable molecular complexity

BACKGROUND

The enteric nervous system (ENS), a complex network of neurons and glial cells, coordinates major gastrointestinal functions. Impaired development or secondary aberrations cause severe enteric neuropathies. Neural crest-derived stem cells as well as enteric neuronal progenitor cells, which form enteric neurospheres, represent a promising tool to unravel molecular pathomechanisms and to develop novel therapy options. However, so far little is known about the detailed cellular composition and the proportional distribution of enteric neurospheres. Comprehensive knowledge will not only be essential for basic research but also for prospective cell replacement therapies to restore or to improve enteric neuronal dysfunction.

METHODS

Human enteric neurospheres were generated from three individuals with varying age. For detailed molecular characterization, nCounter target gene expression analyses focusing on stem, progenitor, neuronal, glial, muscular, and epithelial cell markers were performed. Corresponding archived paraffin-embedded individuals' specimens were analyzed accordingly.

KEY RESULTS

Our data revealed a remarkable molecular complexity of enteric neurospheres and archived specimens. Amongst the expression of multipotent stem cell, progenitor cell, neuronal, glial, muscle and epithelial cell markers, moderate levels for the pluripotency marker POU5F1 were observed. Furthermore, besides the interindividual variability, we identified highly distinct intraindividual expression profiles.

CONCLUSIONS & INFERENCES

Our results emphasize the assessment of molecular signatures to be essential for standardized use, optimization of experimental approaches, and elimination of potential risk factors, as the formation of tumors. Our study pipeline may serve as a blueprint implemented into the characterization procedure of enteric neurospheres for various future applications.

Enteric Neurogenesis During Life Span Under Physiological and Pathophysiological Conditions

The enteric nervous system (ENS) controls gastrointestinal key functions and is mainly characterized by two ganglionated plexus located in the gut wall: the myenteric plexus and the submucous plexus. The ENS harbors a high number and diversity of enteric neurons and glial cells, which generate neuronal circuitry to regulate intestinal physiology. In the past few years, the pivotal role of enteric neurons in the underlying mechanism of several intestinal diseases was revealed. Intestinal diseases are associated with neuronal death that could in turn compromise intestinal functionality. Enteric neurogenesis and regeneration is therefore a crucial aspect within the ENS and could be revealed not only during embryogenesis and early postnatal periods, but also in the adulthood. Enteric glia and/or enteric neural precursor/progenitor cells differentiate into enteric neurons, both under homeostatic and pathologic conditions beyond the perinatal period. The unique role of the intestinal microbiota and serotonin signaling in postnatal and adult neurogenesis has been shown by several studies in health and disease. In this review article, we will mainly focus on different recent studies, which advanced the concept of postnatal and adult ENS neurogenesis. Moreover, we will discuss the key factors and underlying mechanisms, which promote enteric neurogenesis. Finally, we will shortly describe neurogenesis of transplanted enteric neural progenitor cells. Anat Rec, 302:1345-1353, 2019. © 2019 Wiley Periodicals, Inc.

Stem cells as a potential therapy for diabetes mellitus: a call-to-action in Latin America

Latin America is a fast-growing region that currently faces unique challenges in the treatment of all forms of diabetes mellitus. The burden of this disease will be even greater in the coming years due, in part, to the large proportion of young adults living in urban areas and engaging in unhealthy lifestyles. Unfortunately, the national health systems in Latin-American countries are unprepared and urgently need to reorganize their health care services to achieve diabetic therapeutic goals. Stem cell research is attracting increasing attention as a promising and fast-growing field in Latin America. As future healthcare systems will include the development of regenerative medicine through stem cell research, Latin America is urged to issue a call-to-action on stem cell research. Increased efforts are required in studies focused on stem cells for the treatment of diabetes. In this review, we aim to inform physicians, researchers, patients and funding sources about the advances in stem cell research for possible future applications in diabetes mellitus. Emerging studies are demonstrating the potential of stem cells for β cell differentiation and pancreatic regeneration. The major economic burden implicated in patients with diabetes complications suggests that stem cell research may relieve diabetic complications. Closer attention should be paid to stem cell research in the future as an alternative treatment for diabetes mellitus.

Transplanted enteric neural stem cells integrate within the developing chick spinal cord: implications for spinal cord repair

Spinal cord injury (SCI) causes paralysis, multisystem impairment and reduced life expectancy, as yet with no cure. Stem cell therapy can potentially replace lost neurons, promote axonal regeneration and limit scar formation, but an optimal stem cell source has yet to be found. Enteric neural stem cells (ENSC) isolated from the enteric nervous system (ENS) of the gastrointestinal (GI) tract are an attractive source. Here, we used the chick embryo to assess the potential of ENSC to integrate within the developing spinal cord. In vitro, isolated ENSC formed extensive cell connections when co-cultured with spinal cord (SC)-derived cells. Further, qRT-PCR analysis revealed the presence of TuJ1⁺ neurons, S100⁺ glia and Sox10⁺ stem cells within ENSC neurospheres, as well as expression of key neuronal subtype genes, at levels comparable to SC tissue. Following ENSC transplantation to an ablated region of chick embryo SC, donor neurons were found up to 12 days later. These neurons formed bridging connections within the SC injury zone, aligned along the anterior/posterior axis, and were immunopositive for TuJ1. These data provide early proof of principle support for the use of ENSCs for SCI, and encourage further research into their potential for repair.

Recent developments in cell-based ENS regeneration - a short review

Therapeutic options to treat neurogenic motility disorders of the gastrointestinal tract are usually limited to symptomatic treatment. The capacity of the enteric nervous system (ENS) to regenerate and the fact that progenitor cells of the enteric nervous system reside in the postnatal and adult gut led to the idea to develop cell-based strategies to treat ENS related disorders. This short review focuses on recent developments in cell-based ENS regeneration, discussing advantages and disadvantages of various cell sources, functional impact of transplanted cells and highlights the challenges of translation of small animal studies to human application.

Activation of Wnt Signaling Increases Numbers of Enteric Neurons Derived From Neonatal Mouse and Human Progenitor Cells

BACKGROUND & AIMS

Neural stem and progenitor cells from the enteric nervous system (ENS) might serve as a source of cells for treatment of neurogastrointestinal disorders. Before we can use these cells, we must increase our understanding of the signaling mechanisms that regulate proliferation and differentiation. We systematically evaluated the effects of canonical Wnt signaling on proliferation and differentiation of cultured ENS progenitor cells from neonatal mice and humans.

METHODS

We isolated ENS progenitors from tunica muscularis of the small intestine of newborn (postnatal day 0) wild-type C57BL/6 mice as well as from Wnt1-Cre2 reporter mice. We also obtained intestinal tissue samples from infants (2 and 7 months old) undergoing surgery for imperforate anus or focal intestinal perforation and isolated ENS cells. ENS cells were cultured under proliferation conditions leading to formation of 3-dimensional spheres, which we activated with Wnt3a and SB216763 in order to activate the β-catenin-dependent canonical Wnt pathway. We used immunoblot and quantitative polymerase chain reaction to evaluate the molecular response to Wnt stimuli and immunohistochemistry, proliferation, and cell death assays to identify new neurons.

RESULTS

In proliferating enterospheres derived from ENS progenitor cells, we verified the expression of Wnt receptors frizzled 1-10 and the co-receptors low-density lipoprotein receptor-related proteins 5 and 6. Pharmacologic stimulation with Wnt agonists led to intracellular accumulation of Wnt-dependent β-catenin and up-regulated expression of known Wnt target genes axin2, lef1, and lgr5. Activation of the canonical Wnt pathway promoted growth of ENS cell spheres during cell expansion and increased the number of newborn neurons derived from mouse and human progenitor cells.

CONCLUSIONS

In studies of human and mouse ENS progenitors, we found activation of the Wnt signaling pathway to promote neurogenesis of the ENS in vitro. The neurogenic effect of Wnt agonists on ENS progenitors supports their use in generation of cell pools for autologous cell replacement therapies.

Adult enteric nervous system in health is maintained by a dynamic balance between neuronal apoptosis and neurogenesis

According to current dogma, there is little or no ongoing neurogenesis in the fully developed adult enteric nervous system. This lack of neurogenesis leaves unanswered the question of how enteric neuronal populations are maintained in adult guts, given previous reports of ongoing neuronal death. Here, we confirm that despite ongoing neuronal cell loss because of apoptosis in the myenteric ganglia of the adult small intestine, total myenteric neuronal numbers remain constant. This observed neuronal homeostasis is maintained by new neurons formed in vivo from dividing precursor cells that are located within myenteric ganglia and express both Nestin and p75NTR, but not the pan-glial marker Sox10. Mutation of the phosphatase and tensin homolog gene in this pool of adult precursors leads to an increase in enteric neuronal number, resulting in ganglioneuromatosis, modeling the corresponding disorder in humans. Taken together, our results show significant turnover and neurogenesis of adult enteric neurons and provide a paradigm for understanding the enteric nervous system in health and disease.

Phenotype and distribution pattern of nestin-GFP-expressing cells in murine myenteric plexus

The enteric nervous system has to adapt to altering dietary or environmental conditions and presents an enormous plasticity that is conserved over the whole lifespan. It harbours neural-crest-derived neurons, glial cells and their precursors. Based on a nestin-green fluorescent protein (NGFP) transgenic model, a histological inventory has been performed to deliver an overview of neuronal and glial markers for the various parts of the gastrointestinal tract in newborn (postnatal day 7) and adult mice under homeostatic conditions. Whereas NGFP-positive glial cells can be found in all parts of the gut at any individual age, a specific NGFP population is present with both neuronal morphology and marker expression in the myenteric plexus (nNGFP). These cells appear in variable quantities, depending on age and location. Their overall abundance decreases from newborn to adults and their spatial distribution is also age-dependent. In newborn gut, nNGFP cells are found in similar quantities throughout the gut, with a significantly lower presence in the duodenum. Their expression increases in the adult mouse from the stomach to the colon. All of these nNGFP cells expressed either (but not both) of the glia markers S100 or glial fibrillary acidic protein (GFAP). In the S100-positive glia population, a subset of cells also shows a neuronal morphology (nS100), without expressing nestin. Thus, the presence of premature neurons that express NGFP demonstrates that neurogenesis takes place far beyond birth. In enteric neurons, NGFP acts as a marker for neuronal plasticity showing the differentiation and change in the phenotype of neuronal precursor cells.

White paper on guidelines concerning enteric nervous system stem cell therapy for enteric neuropathies

Over the last 20 years, there has been increasing focus on the development of novel stem cell based therapies for the treatment of disorders and diseases affecting the enteric nervous system (ENS) of the gastrointestinal tract (so-called enteric neuropathies). Here, the idea is that ENS progenitor/stem cells could be transplanted into the gut wall to replace the damaged or absent neurons and glia of the ENS. This White Paper sets out experts' views on the commonly used methods and approaches to identify, isolate, purify, expand and optimize ENS stem cells, transplant them into the bowel, and assess transplant success, including restoration of gut function. We also highlight obstacles that must be overcome in order to progress from successful preclinical studies in animal models to ENS stem cell therapies in the clinic.

Organotypic Cultures as a Model to Study Adult Neurogenesis in CNS Disorders

Neural regeneration resides in certain specific regions of adult CNS. Adult neurogenesis occurs throughout life, especially from the subgranular zone of hippocampus and the subventricular zone, and can be modulated in physiological and pathological conditions. Numerous techniques and animal models have been developed to demonstrate and observe neural regeneration but, in order to study the molecular and cellular mechanisms and to characterize multiple types of cell populations involved in the activation of neurogenesis and gliogenesis, investigators have to turn to in vitro models. Organotypic cultures best recapitulate the 3D organization of the CNS and can be explored taking advantage of many techniques. Here, we review the use of organotypic cultures as a reliable and well defined method to study the mechanisms of neurogenesis under normal and pathological conditions. As an example, we will focus on the possibilities these cultures offer to study the pathophysiology of diseases like Alzheimer disease, Parkinson's disease, and cerebral ischemia.

Isogenic enteric neural progenitor cells can replace missing neurons and glia in mice with Hirschsprung disease

BACKGROUND

Transplanting autologous patient-derived enteric neuronal stem/progenitor cells (ENSCs) is an innovative approach to replacing missing enteric neurons in patients with Hirschsprung disease (HSCR). Using autologous cells eliminates immunologic and ethical concerns raised by other cell sources. However, whether postnatal aganglionic bowel is permissive for transplanted ENSCs and whether ENSCs from HSCR patients can be successfully isolated, cultured, and transplanted in vivo remains unknown.

METHODS

ENSCs isolated from the ganglionic intestine of Ednrb(-/-) mice (HSCR-ENSCs) were characterized immunohistochemically and evaluated for their capacity to proliferate and differentiate in vitro. Fluorescently labeled ENSCs were co-cultured ex vivo with aganglionic Ednrb(-/-) colon. For in vivo transplantation, HSCR-ENSCs were labeled with lentivirus expressing green fluorescent protein (GFP) and implanted into aganglionic embryonic chick gut in ovo and postnatal aganglionic Ednrb(-/-) rectum in vivo.

KEY RESULTS

HSCR-ENSCs maintain normal capacity self-renewal and neuronal differentiation. Moreover, the Ednrb(-/-) aganglionic environment is permissive to engraftment by wild-type ENSCs ex vivo and supports migratrion and neuroglial differentiation of these cells following transplantation in vivo. Lentiviral GFP-labeled HSCR-ENSCs populated embryonic chick hindgut and postnatal colon of Ednrb(-/-) HSCR, with cells populating the intermuscular layer and forming enteric neurons and glia.

CONCLUSIONS & INFERENCES

ENSCs can be isolated and cultured from mice with HSCR, and transplanted into the aganglionic bowel of HSCR littermates to generate enteric neuronal networks. These results in an isogenic model establish the potential of using autologous-derived stem cells to treat HSCR and other intestinal neuropathies.

Engraftment of enteric neural progenitor cells into the injured adult brain

Background

A major area of unmet need is the development of strategies to restore neuronal network systems and to recover brain function in patients with neurological disease. The use of cell-based therapies remains an attractive approach, but its application has been challenging due to the lack of suitable cell sources, ethical concerns, and immune-mediated tissue rejection. We propose an innovative approach that utilizes gut-derived neural tissue for cell-based therapies following focal or diffuse central nervous system injury.

Results

Enteric neuronal stem and progenitor cells, able to differentiate into neuronal and glial lineages, were isolated from the postnatal enteric nervous system and propagated in vitro. Gut-derived neural progenitors, genetically engineered to express fluorescent proteins, were transplanted into the injured brain of adult mice. Using different models of brain injury in combination with either local or systemic cell delivery, we show that transplanted enteric neuronal progenitor cells survive, proliferate, and differentiate into neuronal and glial lineages in vivo. Moreover, transplanted cells migrate extensively along neuronal pathways and appear to modulate the local microenvironment to stimulate endogenous neurogenesis.

Conclusions

Our findings suggest that enteric nervous system derived cells represent a potential source for tissue regeneration in the central nervous system. Further studies are needed to validate these findings and to explore whether autologous gut-derived cell transplantation into the injured brain can result in functional neurologic recovery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-016-0238-y) contains supplementary material, which is available to authorized users.

Stem cell research in Latin America: update, challenges and opportunities in a priority research area

Stem cell research is attracting wide attention as a promising and fast-growing field in Latin America, as it is worldwide. Many countries in the region have defined Regenerative Medicine as a research priority and a focus of investment. This field generates not only opportunities but also regulatory, technical and operative challenges. In this review, scientists from Uruguay, Mexico, Chile, Brazil and Argentina provide their view on stem cell research in each of their countries. Despite country-specific characteristics, all countries share several issues such as regulatory challenges. Key initiatives of each country to promote stem cell research are also discussed. As a conclusion, it is clear that regional integration should be more emphasized and international collaboration, promoted.

Stem cell therapy for GI neuromuscular disorders

The enteric nervous system is the intrinsic innervation of the gut. Several neuromuscular disorders affect the neurons and glia of the enteric nervous system adversely, resulting in disruptions in gastrointestinal motility and function. Pharmacological interventions to remedy gastrointestinal function do not address the underlying cause of dysmotility arising from lost, absent, or damaged enteric neuroglial circuitry. Cell-based therapies have gained traction in the past decade, following the discovery of several adult stem cell niches in the human body. Adult neural stem cells can be isolated from the postnatal and adult intestine using minimally invasive biopsies. These stem cells retain the ability to differentiate into several functional classes of enteric neurons and enteric glia. Upon identification of these cells, several groups have also established that transplantation of these cells into aganglionic or dysganglionic intestine rescues gastrointestinal motility and function. This chapter highlights key studies performed in the field of stem cell transplantation therapies that are targeted towards the remedy of gastrointestinal motility and function.

Vagus Nerve Mediates the Neural Stem Cell Response to Intestinal Injury

BACKGROUND

Intestinal ischemia and reperfusion injury results in damage to elements critical to maintaining intestinal barrier function, including neurons and glia cells, which are part of the enteric nervous system (ENS). To limit inflammation, the ENS must be restored or replaced, yet the process by which this occurs is poorly understood. Multipotent progenitor cells called enteric nervous stem cells (ENSC) can differentiate into neurons or glia when stimulated. The ability of this cell population to respond to intestinal injury is unknown. In this study, we hypothesized that resolution of intestinal barrier injury would be associated with vagus nerve-mediated expansion of ENSCs.

STUDY DESIGN

Ischemia and reperfusion injury was reproduced in male mice by occluding the superior mesenteric artery for 30 minutes. Abdominal vagotomy was performed in a separate cohort to study the effects of the vagus nerve. Terminal ileum was harvested at various time points after reperfusion and analyzed with histology, flow cytometry, and immunohistochemistry.

RESULTS

Enteric nervous stem cell expansion occurs at 2, 4, and 8 hours after injury compared with sham (4.6% vs 2.1%; p < 0.001) and correlated with increased glial fibrillary acidic protein on immunohistochemistry. Vagotomy prevented both ENSC expansion and increased glial fibrillary acidic protein staining after injury. Intestinal permeability was restored to baseline by 48 hours after injury, but remained elevated in the vagotomy group compared with sham and injury alone at 48 hours (3.25 mg/mL vs 0.57 mg/mL and 0.26 mg/mL, respectively; p < 0.05).

CONCLUSIONS

Vagal-mediated expansion of ENSCs occurs after ischemia and reperfusion injury and results in improved kinetics of injury resolution.

Colitis induces enteric neurogenesis through a 5-HT4-dependent mechanism

BACKGROUND

The intestine is known to contain enteric neuronal progenitors, but their precise identity and the mechanisms that activate them remain unknown. Based on the evidence for the neurogenic role of serotonin (5-HT) in the postnatal gut and the observation of enteric neuronal hyperplasia in inflammatory bowel disease, we hypothesized that colitis induces a neurogenic response through 5-HT4 receptor signaling.

METHODS

We examined the effects of 5-HT4 agonism on colonic neurogenesis and gliogenesis in vitro and in vivo in adult mice using dextran sodium sulfate to experimentally induce colitis.

RESULTS

In vitro, 5-HT4 agonism led to increased neuronal proliferation and density. Induction of experimental colitis in vivo similarly resulted in increased numbers of myenteric neurons, and this was inhibited by 5-HT4 antagonism. Interestingly, both in vitro and in vivo, 5-HT4 signaling increased glial cell proliferation but did not increase glial cell numbers, leading us to hypothesize that glia may give rise to neurons. After induction of colitis in normal, Nestin-GFP and Sox2-GFP transgenic mice, it was revealed that multiple glial markers (Sox2, Nestin, and CD49b) became strongly expressed by enteric neurons. Immunoselected enteric glia were found to give rise to neurons in culture, and this was inhibited in the presence of 5-HT4 blockade. Finally, isolated glia gave rise to a neuronal network upon transplantation into aganglionic embryonic avian hindgut.

CONCLUSIONS

These results show that colitis promotes enteric neurogenesis in the adult colon through a serotonin-dependent mechanism that drives glial cells to transdifferentiate into neurons.

Anti-inflammatory activity of Wnt signaling in enteric nervous system: in vitro preliminary evidences in rat primary cultures

Background

In the last years, Wnt signaling was demonstrated to regulate inflammatory processes. In particular, an increased expression of Wnts and Frizzled receptors was reported in inflammatory bowel disease (IBD) and ulcerative colitis to exert both anti- and pro-inflammatory functions regulating the intestinal activated nuclear factor κB (NF-кB), TNFa release, and IL10 expression.

Methods

To investigate the role of Wnt pathway in the response of the enteric nervous system (ENS) to inflammation, neurons and glial cells from rat myenteric plexus were treated with exogenous Wnt3a and/or LPS with or without supporting neurotrophic factors such as basic fibroblast growth factor (bFGF), epithelial growth factor (EGF), and glial cell-derived neurotrophic factor (GDNF). The immunophenotypical characterization by flow cytometry and the protein and gene expression analysis by qPCR and Western blotting were carried out.

Results

Flow cytometry and immunofluorescence staining evidenced that enteric neurons coexpressed Frizzled 9 and toll-like receptor 4 (TLR4) while glial cells were immunoreactive to TLR4 and Wnt3a suggesting that canonical Wnt signaling is active in ENS.

Under in vitro LPS treatment, Western blot analysis demonstrated an active cross talk between canonical Wnt signaling and NF-кB pathway that is essential to negatively control enteric neuronal response to inflammatory stimuli. Upon costimulation with LPS and Wnt3a, a significant anti-inflammatory activity was detected by RT-PCR based on an increased IL10 expression and a downregulation of pro-inflammatory cytokines TNFa, IL1B, and interleukin 6 (IL6). When the availability of neurotrophic factors in ENS cultures was abolished, a changed cell reactivity by Wnt signaling was observed at basal conditions and after LPS treatment.

Conclusions

The results of this study suggested the existence of neuronal surveillance through FZD9 and Wnt3a in enteric myenteric plexus. Moreover, experimental evidences were provided to clarify the correlation among soluble trophic factors, Wnt signaling, and anti-inflammatory protection of ENS.

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.

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.

Design strategies of biodegradable scaffolds for tissue regeneration

There are numerous available biodegradable materials that can be used as scaffolds in regenerative medicine. Currently, there is a huge emphasis on the designing phase of the scaffolds. Materials can be designed to have different properties in order to match the specific application. Modifying scaffolds enhances their bioactivity and improves the regeneration capacity. Modifications of the scaffolds can be later characterized using several tissue engineering tools. In addition to the material, cell source is an important component of the regeneration process. Modified materials must be able to support survival and growth of different cell types. Together, cells and modified biomaterials contribute to the remodeling of the engineered tissue, which affects its performance. This review focuses on the recent advancements in the designs of the scaffolds including the physical and chemical modifications. The last part of this review also discusses designing processes that involve viability of cells.

Maintenance of the enteric stem cell niche by bacterial lipopolysaccharides? Evidence and perspectives

The enteric nervous system (ENS) has to respond to continuously changing microenvironmental challenges within the gut and is therefore dependent on a neural stem cell niche to keep the ENS functional throughout life. In this study, we hypothesize that this stem cell niche is also affected during inflammation and therefore investigated lipopolysaccharides (LPS) effects on enteric neural stem/progenitor cells (NSPCs). NSPCs were derived from the ENS and cultured under the influence of different LPS concentrations. LPS effects upon proliferation and differentiation of enteric NSPC cultures were assessed using immunochemistry, flow cytometry, western blot, Multiplex ELISA and real-time PCR. LPS enhances the proliferation of enteric NSPCs in a dose-dependent manner. It delays and modifies the differentiation of these cells. The expression of the LPS receptor toll-like receptor 4 on NSPCs could be demonstrated. Moreover, LPS induces the secretion of several cytokines. Flow cytometry data gives evidence for individual subgroups within the NSPC population. ENS-derived NSPCs respond to LPS in maintaining at least partially their stem cell character. In the case of inflammatory disease or trauma where the liberation and exposure to LPS will be increased, the expansion of NSPCs could be a first step towards regeneration of the ENS. The reduced and altered differentiation, as well as the induction of cytokine signalling, demonstrates that the stem cell niche may take part in the LPS-transmitted inflammatory processes in a direct and defined way.

In vivo transplantation of neurosphere-like bodies derived from the human postnatal and adult enteric nervous system: a pilot study

Recent advances in the in vitro characterization of human adult enteric neural progenitor cells have opened new possibilities for cell-based therapies in gastrointestinal motility disorders. However, whether these cells are able to integrate within an in vivo gut environment is still unclear. In this study, we transplanted neural progenitor-containing neurosphere-like bodies (NLBs) in a mouse model of hypoganglionosis and analyzed cellular integration of NLB-derived cell types and functional improvement. NLBs were propagated from postnatal and adult human gut tissues. Cells were characterized by immunohistochemistry, quantitative PCR and subtelomere fluorescence in situ hybridization (FISH). For in vivo evaluation, the plexus of murine colon was damaged by the application of cationic surfactant benzalkonium chloride which was followed by the transplantation of NLBs in a fibrin matrix. After 4 weeks, grafted human cells were visualized by combined in situ hybridization (Alu) and immunohistochemistry (PGP9.5, GFAP, SMA). In addition, we determined nitric oxide synthase (NOS)-positive neurons and measured hypertrophic effects in the ENS and musculature. Contractility of treated guts was assessed in organ bath after electrical field stimulation. NLBs could be reproducibly generated without any signs of chromosomal alterations using subtelomere FISH. NLB-derived cells integrated within the host tissue and showed expected differentiated phenotypes i.e. enteric neurons, glia and smooth muscle-like cells following in vivo transplantation. Our data suggest biological effects of the transplanted NLB cells on tissue contractility, although robust statistical results could not be obtained due to the small sample size. Further, it is unclear, which of the NLB cell types including neural progenitors have direct restoring effects or, alternatively may act via 'bystander' mechanisms in vivo. Our findings provide further evidence that NLB transplantation can be considered as feasible tool to improve ENS function in a variety of gastrointestinal disorders.

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.

The human gastrointestinal tract, a potential autologous neural stem cell source

Stem cell therapies seem to be an appropriate tool for the treatment of a variety of diseases, especially when a substantial cell loss leads to a severe clinical impact. This is the case in most neuronal cell losses. Unfortunately, adequate neural stem cell sources are hard to find and current alternatives, such as induced programmed stem cells, still have incalculable risks. Evidence of neurogenesis in the adult human enteric nervous system brought up a new perspective. In humans the appendix harbors enteric neuronal tissue and is an ideal location where the presence of neural stem cells is combined with a minimal invasive accessibility. In this study appendices from adults and children were investigated concerning their neural stem cell potential. From each appendix tissue samples were collected, and processed for immunohistochemistry or enteric neural progenitor cell generation. Free-floating enteric neurospheres (EnNS's) could be generated after 6 days in vitro. EnNS's were either used for transplantation into rat brain slices or differentiation experiments. Both transplanted spheres and control cultures developed an intricate network with glia, neurons and interconnecting fibers, as seen in primary enteric cultures before. Neuronal, glial and neural stem cell markers could be identified both in vitro and in vivo by immunostaining. The study underlines the potential of the enteric nervous system as an autologous neural stem cell source. Using the appendix as a potential target opens up a new perspective that might lead to a relatively unproblematic harvest of neural stem cells.

Enteric nervous system development: migration, differentiation, and disease

The enteric nervous system (ENS) provides the intrinsic innervation of the bowel and is the most neurochemically diverse branch of the peripheral nervous system, consisting of two layers of ganglia and fibers encircling the gastrointestinal tract. The ENS is vital for life and is capable of autonomous regulation of motility and secretion. Developmental studies in model organisms and genetic studies of the most common congenital disease of the ENS, Hirschsprung disease, have provided a detailed understanding of ENS development. The ENS originates in the neural crest, mostly from the vagal levels of the neuraxis, which invades, proliferates, and migrates within the intestinal wall until the entire bowel is colonized with enteric neural crest-derived cells (ENCDCs). After initial migration, the ENS develops further by responding to guidance factors and morphogens that pattern the bowel concentrically, differentiating into glia and neuronal subtypes and wiring together to form a functional nervous system. Molecules controlling this process, including glial cell line-derived neurotrophic factor and its receptor RET, endothelin (ET)-3 and its receptor endothelin receptor type B, and transcription factors such as SOX10 and PHOX2B, are required for ENS development in humans. Important areas of active investigation include mechanisms that guide ENCDC migration, the role and signals downstream of endothelin receptor type B, and control of differentiation, neurochemical coding, and axonal targeting. Recent work also focuses on disease treatment by exploring the natural role of ENS stem cells and investigating potential therapeutic uses. Disease prevention may also be possible by modifying the fetal microenvironment to reduce the penetrance of Hirschsprung disease-causing mutations.

Neuroglial differentiation of adult enteric neuronal progenitor cells as a function of extracellular matrix composition

Enteric neuronal progenitor cells are neural crest-derived stem cells that can be isolated from fetal, post-natal and adult gut. Neural stem cell transplantation is an emerging therapeutic paradigm to replace dysfunctional or lost enteric neurons in several aganglionic disorders of the GI tract. The impetus to identify an appropriate microenvironment for enteric neuronal progenitor cells derives from the need to improve survival and phenotypic stability following implantation. Extracellular matrix composition can modulate stem cell fate and direct differentiation. Adult mammalian myenteric ganglia in vivo are surrounded by a matrix composed primarily of Collagen IV, Laminin and a Heparan sulfate proteoglycan. In these studies, adult mammalian enteric neuronal progenitor cells isolated from full thickness rabbit intestines were induced to differentiate when cultured on various combinations of neural ECM substrates. Neuronal and glial differentiation was studied as a function of ECM composition on coated glass coverslips. Poly-lysine coated coverslips (control) supported extensive glial differentiation but very minimal neuronal differentiation. Individual culture substrata (Laminin, Collagen I and Collagen IV) were conducive for both neuronal and glial differentiation. The addition of laminin or heparan sulfate to collagen substrates improved neuronal differentiation, significantly increased neurite lengths, branching and initiation of neuronal network formation. Glial differentiation was extensive on control poly lysine coated coverslips. Addition of laminin or heparan sulfate to composite collagen substrates significantly reduced glial immunofluorescence. Various neural ECM components were evaluated individually and in combination to study their effect of neuroglial differentiation of adult enteric neuronal progenitor cells. Our results indicate that specific ECM substrates that include type IV Collagen, laminin and heparan sulfate support and maintain neuronal and glial differentiation to different extents. Here, we identify a matrix composition optimized to tissue engineer transplantable innervated GI smooth muscle constructs to remedy aganglionic disorders.

Ex vivo neurogenesis within enteric ganglia occurs in a PTEN dependent manner

A population of multipotent stem cells capable of differentiating into neurons and glia has been isolated from adult intestine in humans and rodents. While these cells may provide a pool of stem cells for neurogenesis in the enteric nervous system (ENS), such a function has been difficult to demonstrate in vivo. An extensive study by Joseph et al. involving 108 rats and 51 mice submitted to various insults demonstrated neuronal uptake of thymidine analog BrdU in only 1 rat. Here we introduce a novel approach to study neurogenesis in the ENS using an ex vivo organotypic tissue culturing system. Culturing longitudinal muscle and myenteric plexus tissue, we show that the enteric nervous system has tremendous replicative capacity with the majority of neural crest cells demonstrating EdU uptake by 48 hours. EdU⁺ cells express both neuronal and glial markers. Proliferation appears dependent on the PTEN/PI3K/Akt pathway with decreased PTEN mRNA expression and increased PTEN phosphorylation (inactivation) corresponding to increased Akt activity and proliferation. Inhibition of PTEN with bpV(phen) augments proliferation while LY294002, a PI3K inhibitor, blocks it. These data suggest that the ENS is capable of neurogenesis in a PTEN dependent manner.

Nestin-expressing cells in the gut give rise to enteric neurons and glial cells

BACKGROUND

Neuronal stem cells (NSCs) are promising for neurointestinal disease therapy. Although NSCs have been isolated from intestinal musclularis, their presence in mucosa has not been well described. Mucosa-derived NSCs are accessible endoscopically and could be used autologously. Brain-derived Nestin-positive NSCs are important in endogenous repair and plasticity. The aim was to isolate and characterize mucosa-derived NSCs, determine their relationship to Nestin-expressing cells and to demonstrate their capacity to produce neuroglial networks in vitro and in vivo.

METHODS

Neurospheres were generated from periventricular brain, colonic muscularis (Musc), and mucosa-submucosa (MSM) of mice expressing green fluorescent protein (GFP) controlled by the Nestin promoter (Nestin-GFP). Neuronal stem cells were also grown as adherent colonies from intestinal mucosal organoids. Their differentiation potential was assessed using immunohistochemistry using glial and neuronal markers. Brain and gut-derived neurospheres were transplanted into explants of chick embryonic aneural hindgut to determine their fate.

KEY RESULTS

Musc- and MSM-derived neurospheres expressed Nestin and gave rise to cells of neuronal, glial, and mesenchymal lineage. Although Nestin expression in tissue was mostly limited to glia co-labelled with glial fibrillary acid protein (GFAP), neurosphere-derived neurons and glia both expressed Nestin in vitro, suggesting that Nestin+/GFAP+ glial cells may give rise to new neurons. Moreover, following transplantation into aneural colon, brain- and gut-derived NSCs were able to differentiate into neurons.

CONCLUSIONS & INFERENCES

Nestin-expressing intestinal NSCs cells give rise to neurospheres, differentiate into neuronal, glial, and mesenchymal lineages in vitro, generate neurons in vivo and can be isolated from mucosa. Further studies are needed for exploring their potential for treating neuropathies.

Divergent fate and origin of neurosphere-like bodies from different layers of the gut

Enteric neural stem cells (ENSCs) are a population of neural crest-derived multipotent stem cells present in postnatal gut that may play an important role in regeneration of the enteric nervous system. In most studies, these cells have been isolated from the layer of the gut containing the myenteric plexus. However, a recent report demonstrated that neurosphere-like bodies (NLBs) containing ENSCs could be isolated from mucosal biopsy specimens from children, suggesting that ENSCs are present in multiple layers of the gut. The aim of our study was to assess whether NLBs isolated from layers of gut containing either myenteric or submucosal plexus are equivalent. We divided the mouse small intestine into two layers, one containing myenteric plexus and the other submucosal plexus, and assessed for NLB formation. Differences in NLB density, proliferation, apoptosis, neural crest origin, and phenotype were investigated. NLBs isolated from the myenteric plexus layer were present at a higher density and demonstrated greater proliferation, lower apoptosis, and higher expression of nestin, p75, Sox10, and Ret than those from submucosal plexus. Additionally, they contained a higher percentage of neural crest-derived cells (99.4 ± 1.5 vs. 0.7 ± 1.19% of Wnt1-cre:tdTomato cells; P < 0.0001) and produced more neurons and glial cells than those from submucosal plexus. NLBs from the submucosal plexus layer expressed higher CD34 and produced more smooth muscle-like cells. NLBs from the myenteric plexus layer contain more neural crest-derived ENSCs while those from submucosal plexus appear more heterogeneous, likely containing a population of mesenchymal stem cells.

A novel xenogeneic co-culture system to examine neuronal differentiation capability of various adult human stem cells

Background

Targeted differentiation of stem cells is mainly achieved by the sequential administration of defined growth factors and cytokines, although these approaches are quite artificial, cost-intensive and time-consuming. We now present a simple xenogeneic rat brain co-culture system which supports neuronal differentiation of adult human stem cells under more in vivo-like conditions.

Methods and Findings

This system was applied to well-characterized stem cell populations isolated from human skin, parotid gland and pancreas. In addition to general multi-lineage differentiation potential, these cells tend to differentiate spontaneously into neuronal cell types in vitro and are thus ideal candidates for the introduced co-culture system. Consequently, after two days of co-culture up to 12% of the cells showed neuronal morphology and expressed corresponding markers on the mRNA and protein level. Additionally, growth factors with the ability to induce neuronal differentiation in stem cells could be found in the media supernatants of the co-cultures.

Conclusions

The co-culture system described here is suitable for testing neuronal differentiation capability of numerous types of stem cells. Especially in the case of human cells, it may be of clinical relevance for future cell-based therapeutic applications.

Enteric glia are multipotent in culture but primarily form glia in the adult rodent gut

It is unclear whether neurogenesis occurs in the adult mammalian enteric nervous system (ENS). Neural crest-derived cells capable of forming multilineage colonies in culture, and neurons and glia upon transplantation into chick embryos, persist throughout adult life in the mammalian ENS. In this study we sought to determine the physiological function of these cells. We discovered that these cells could be identified based on CD49b expression and that they had characteristics of enteric glia, including p75, GFAP, S100B, and SOX10 expression. To test whether new neurons or glia arise in the adult gut under physiological conditions, we marked dividing progenitors with a thymidine analog in rodents under steady-state conditions, or during aging, pregnancy, dietary changes, hyperglycemia, or exercise. We also tested gut injuries including inflammation, irradiation, benzalkonium chloride treatment, partial gut stenosis, and glial ablation. We readily observed neurogenesis in a neurogenic region of the central nervous system, but not reproducibly in the adult ENS. Lineage tracing of glial cells with GFAP-Cre and GFAP-CreERT2 also detected little or no adult ENS neurogenesis. Neurogenesis in the adult gut is therefore very limited under the conditions we studied. In contrast, ENS gliogenesis was readily observed under steady-state conditions and after injury. Adult enteric glia thus have the potential to form neurons and glia in culture but are fated to form mainly glia under physiological conditions and after the injuries we studied.

Glial cells in the mouse enteric nervous system can undergo neurogenesis in response to injury

The enteric nervous system (ENS) in mammals forms from neural crest cells during embryogenesis and early postnatal life. Nevertheless, multipotent progenitors of the ENS can be identified in the adult intestine using clonal cultures and in vivo transplantation assays. The identity of these neurogenic precursors in the adult gut and their relationship to the embryonic progenitors of the ENS are currently unknown. Using genetic fate mapping, we here demonstrate that mouse neural crest cells marked by SRY box-containing gene 10 (Sox10) generate the neuronal and glial lineages of enteric ganglia. Most neurons originated from progenitors residing in the gut during mid-gestation. Afterward, enteric neurogenesis was reduced, and it ceased between 1 and 3 months of postnatal life. Sox10-expressing cells present in the myenteric plexus of adult mice expressed glial markers, and we found no evidence that these cells participated in neurogenesis under steady-state conditions. However, they retained neurogenic potential, as they were capable of generating neurons with characteristics of enteric neurons in culture. Furthermore, enteric glia gave rise to neurons in vivo in response to chemical injury to the enteric ganglia. Our results indicate that despite the absence of constitutive neurogenesis in the adult gut, enteric glia maintain limited neurogenic potential, which can be activated by tissue dissociation or injury.

RGMa inhibits neurite outgrowth of neuronal progenitors from murine enteric nervous system via the neogenin receptor in vitro

The enteric nervous system (ENS) in vertebrate embryos is formed by neural crest-derived cells. During development, these cells undergo extensive migration from the vagal and sacral regions to colonize the entire gut, where they differentiate into neurons and glial cells. Guidance molecules like netrins, semaphorins, slits, and ephrins are known to be involved in neuronal migration and axon guidance. In the CNS, the repulsive guidance molecule (RGMa) has been implicated in neuronal differentiation, migration, and apoptosis. Recently, we described the expression of the subtypes RGMa and RGMb and their receptor neogenin during murine gut development. In the present study, we investigated the influence of RGMa on neurosphere cultures derived from fetal ENS. In functional in vitro assays, RGMa strongly inhibited neurite outgrowth of differentiating progenitors via the receptor neogenin. The repulsive effect of RGMa on processes of differentiated enteric neural progenitors could be demonstrated by collapse assay. The influence of the RGM receptor on ENS was also analyzed in neogenin knockout mice. In the adult large intestine of mutants we observed disturbed ganglia formation in the myenteric plexus. Our data indicate that RGMa may be involved in differentiation processes of enteric neurons in the murine gut.

Isolation and live imaging of enteric progenitors based on Sox10-Histone2BVenus transgene expression

To facilitate dynamic imaging of neural crest (NC) lineages and discrimination of individual cells in the enteric nervous system (ENS) where close juxtaposition often complicates viewing, we generated a mouse BAC transgenic line that drives a Histone2BVenus (H2BVenus) reporter from Sox10 regulatory regions. This strategy does not alter the endogenous Sox10 locus and thus facilitates analysis of normal NC development. Our Sox10-H2BVenus BAC transgene exhibits temporal, spatial, and cell-type specific expression that reflects endogenous Sox10 patterns. Individual cells exhibiting nuclear-localized fluorescence of the H2BVenus reporter are readily visualized in both fixed and living tissue and are amenable to isolation by fluorescence activated cell sorting (FACS). FACS-isolated H2BVenus+ enteric NC-derived progenitors (ENPs) exhibit multipotency, readily form neurospheres, self-renew in vitro and express a variety of stem cell genes. Dynamic live imaging as H2BVenus+ ENPs migrate down the fetal gut reveals cell fragmentation suggesting that apoptosis occurs at a low frequency during normal development of the ENS. Confocal imaging both during population of the fetal intestine and in postnatal gut muscle strips revealed differential expression between individual cells consistent with down-regulation of the transgene as progression towards non-glial fates occurs. The expression of the Sox10-H2BVenus transgene in multiple regions of the peripheral nervous system will facilitate future studies of NC lineage segregation as this tool is expressed in early NC progenitors and maintained in enteric glia.

Evidence for neural progenitor cells in the human adult enteric nervous system

Putative neural stem cells have been identified within the enteric nervous system (ENS) of adult rodents and cultured from human myenteric plexus. We conducted studies to identify neural stem cells or progenitor cells within the submucosa of adult human ENS. Jejunum tissue was removed from adult human subjects undergoing gastric bypass surgery. The tissue was immunostained, and confocal images of ganglia in the submucosal plexus were collected to identify protein gene product 9.5 (PGP 9.5) - immunoractive neurons and neuronal progenitor cells that coexpress PGP 9.5 and nestin. In addition to PGP-9.5-positive/nestin-negative neuronal cells within ganglia, we observed two other types of cells: (1) cells in which PGP 9.5 and nestin were co-localized, (2) cells negative for both PGP 9.5 and nestin. These observations suggest that the latter two types of cells are related to a progenitor cell population and are consistent with the concept that the submucosa of human adult ENS contains stem cells capable of maintenance and repair within the peripheral nervous system.

Transplantation of enteric cells expressing p75 in the rodent stomach

BACKGROUND

Neural crest stem cells may hold potential as a cellular therapeutic to repopulate the enteric nervous system. The expression of the low-affinity nerve growth factor receptor, p75, may enrich enteric cells isolated from the neonatal rodent intestinal tract for neural crest stem cells. While these cells have shown tremendous promise in vitro, it remains to be determined whether they will survive and differentiate after in vivo transplantation.

MATERIALS AND METHODS

Cells isolated from the neonatal rodent intestinal muscularis were sorted according to their degree of p75 expression. The parent, p75-high, and p75-low expressing populations were injected into the rodent stomach for 7 d in vivo.

RESULTS

Cells that expressed high levels of p75 also expressed high levels of nestin. Evaluation of the parent, p75-high, and p75-low populations of cells showed 420-, 130-, and 20-fold growth, respectively, after 11 d of culture. Transplantation of these populations of cells into syngeneic rodent stomachs showed cell survival in the injection site after 7 d. Cells expressing either the neuronal marker, peripherin, or the glial marker, S100, were present in and around the injection site when the parent and the p75-high populations were transplanted.

CONCLUSIONS

Enteric cells survive transplantation into the rodent stomach and induce the expression of differentiation markers in and around the injection site. Based on these results, enteric cells may hold potential as a cellular therapeutic in a variety of gastrointestinal disorders.

Hirschsprung's disease

Hirschsprung's disease (HSCR) is characterized by absence of the enteric nervous system in a variable portion of the distal gut. Affected infants usually present in the days after birth with bowel obstruction. Despite surgical advances, long-term outcomes remain variable. In the last 2 decades, great advances have been made in understanding the genes and molecular biological mechanisms that underlie the disease. In addition, our understanding of normal enteric nervous system development and how motility develops in the developing fetus and infant has also increased. This review aims to draw these strands together to explain the developmental and biological basis of HSCR, and how this knowledge may be used in the future to aid children with HSCR.