Transplantation of enteric cells into the aganglionic rodent small intestines

Cutting-edge regenerative therapy for Hirschsprung disease and its allied disorders

Hirschsprung disease (HSCR) and its associated disorders (AD-HSCR) often result in severe hypoperistalsis caused by enteric neuropathy, mesenchymopathy, and myopathy. Notably, HSCR involving the small intestine, isolated hypoganglionosis, chronic idiopathic intestinal pseudo-obstruction, and megacystis-microcolon-intestinal hypoperistalsis syndrome carry a poor prognosis. Ultimately, small-bowel transplantation (SBTx) is necessary for refractory cases, but it is highly invasive and outcomes are less than optimal, despite advances in surgical techniques and management. Thus, regenerative therapy has come to light as a potential form of treatment involving regeneration of the enteric nervous system, mesenchyme, and smooth muscle in affected areas. We review the cutting-edge regenerative therapeutic approaches for managing HSCR and AD-HSCR, including the use of enteric nervous system progenitor cells, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells as cell sources, the recipient intestine's microenvironment, and transplantation methods. Perspectives on the future of these treatments are also discussed.

Autologous Transplantation of Skin-Derived Precursor Cells in a Porcine Model

BACKGROUND

Hirschprung's disease is characterized by aganglionic bowel and often requires surgical resection. Cell-based therapies have been investigated as potential alternatives to restore functioning neurons. Skin-derived precursor cells (SKPs) differentiate into neural and glial cells in vitro and generate ganglion-like structures in rodents. In this report, we aimed to translate this approach into a large animal model of aganglionosis using autologous transplantation of SKPs.

METHODS

Juvenile pigs underwent skin procurement from the shoulder and simultaneous chemical denervation of an isolated colonic segment. Skin cells were cultured in neuroglial-selective medium and labeled with fluorescent dye for later identification. The cultured SKPs were then injected into the aganglionic segments of colon, and the specimens were retrieved within seven days after transplantation. SKPs in vitro and in vivo were assessed with histologic samples for various immunofluorescent markers of multipotency and differentiation. SKPs from the time of harvest were compared to those at the time of injection using PCR.

RESULTS

Prior to transplantation, 72% of SKPs stained positive for nestin and S100b, markers of neural and glial precursor cells of neural crest origin, respectively. Markers of differentiated neurons and gliocytes, TUJ1 and GFAP, were detected in 47% of cultured SKPs. After transplantation, SKPs were identified in both myenteric and submucosal plexuses of the treated colon. Nestin co-expression was detected in the SKPs within the aganglionic colon in vivo. Injected SKPs appeared to migrate and express early neuroglial differentiation markers.

CONCLUSIONS

Autologous SKPs implanted into aganglionic bowel demonstrated immunophenotypes of neuroglial progenitors. Our results suggest that autologous SKPs may be potentially useful for cell-based therapy for patients with enteric nervous system disorders.

TYPE OF STUDY

Basic science.

3D Synthetic Peptide-based Architectures for the Engineering of the Enteric Nervous System

Damage of enteric neurons and partial or total loss of selective neuronal populations are reported in intestinal disorders including inflammatory bowel diseases and necrotizing enterocolitis. To develop three-dimensional scaffolds for enteric neurons we propose the decoration of ionic-complementary self-assembling peptide (SAP) hydrogels, namely EAK or EAbuK, with bioactive motives. Our results showed the ability of EAK in supporting neuronal cell attachment and neurite development. Therefore, EAK was covalently conjugated to: RGD, (GRGDSP)₄K (fibronectin), FRHRNRKGY (h-vitronectin, named HVP), IKVAV (laminin), and type 1 Insulin-like Growth Factor (IGF-1). Chemoselective ligation was applied for the SAP conjugation with IGF-1 and the other longer sequences. Freshly isolated murine enteric neurons attached and grew on all functionalized EAK but IGF-1. Cell-cell contact was evident on hydrogels enriched with (GRGDSP)₄K and HVP. Moreover (GRGDSP)₄K significantly increased mRNA expression of neurotrophin-3 and nerve growth factor, two trophic factors supporting neuronal survival and differentiation, whereas IKVAV decoration specifically increased mRNA expression of acetylcholinesterase and choline acetyltransferase, genes involved in synaptic communication between cholinergic neurons. Thus, decorated hydrogels are proposed as injectable scaffolds to support in loco survival of enteric neurons, foster synaptic communication, or drive the differentiation of neuronal subtypes.

Nontoxicity of lentiviral vector infection to viability, migration, apoptosis, and differentiation of postnatal rat enteric neural crest-derived cells

Lentiviral vector infection of enhanced green fluorescent protein fluorescence reporter genes in enteric neural crest-derived cells maintained efficient, stable, long-term labeling and the infected enteric neural crest-derived cells could survive, proliferate, and express fluorescent reporter genes. However, the method does not show whether there is some defined or undefined toxicity to the enteric neural crest-derived cells, which may affect enteric neural crest-derived cells' properties. Here, we evaluated the enteric neural crest-derived cells properties under the influence of lentivirus infection of enhanced green fluorescent protein fluorescence reporter genes. This study used the cell count kit-8 for measurement of vitality, transwell for cell migration, immunocytochemistry for cell count and identification, and tested the apoptosis of the enteric neural crest-derived cells with flow cytometry. The enteric neural crest-derived cells with or without lentivirus and their derivative enteric neural crest-derived cells could form characteristic neurospheres, and maintain their level of fluorescent label steady. When cultured under inducing conditions, enteric neural crest-derived cells differentiated into neurons and glia. The results showed that the enteric neural crest-derived cells with or without lentivirus showed no significant difference in viability, migration, apoptosis, neuronal, and glial ratio. The study identified that lentivirus can be used in a nontoxic manner for infection of enhanced green fluorescent protein fluorescence reporter genes into enteric neural crest-derived cells.

A Time-Limited and Partially Reversible Model of Hypoganglionosis Induced by Benzalkonium Chloride Treatment

Serosal application of benzalkonium chloride (BAC) has been previously applied to produce a model of aganglionosis; however, confusion remains regarding the extent of chemical ablation of enteric myenteric plexus after BAC treatment. The time sequence of BAC-induced effects on the myenteric plexus of the rat colon was determined and followed the morphologic changes. After sacrifice of animals 7, 14, 28, 56, 84 or 168 days postintervention, colonic tissue samples were removed, fixed in formalin, and cut into 5-μm longitudinal sections for histological analysis. The neural analysis was used to re-evaluate BAC treatments for the appropriate model. Compared with rats in sham groups, rats in 0.1 %-30-min BAC group maintained only 15.27 ± 4.80 % of ganglia per section in a 1-cm/5-μm slice and 11.76 ± 2.30 % of ganglionic cells after 28 days, the lower and stable number of ganglionic cells between Day 7 and 84 (from 11.67 ± 2.10 to 19.05 ± 5.10 %). Although an increase, ganglionic cell numbers did not recover at Day168 when compared with the numbers in sham groups. The results showed that characteristics of rats in the 0.1 %-30-min BAC group between Day 7 and 84 most closely kept in stable state, suggesting that these treatment parameters are ideal for producing a hypoganglia model of hypoganglionosis.

Mouse model of endoscopically ablated enteric nervous system

BACKGROUND

Current transgenic animal models of Hirschsprung disease are restricted by limited survival and need for special dietary care. We used small animal colonoscopy to produce chemically ablated enteric nervous system in the distal colon and rectum of normal mice.

MATERIALS AND METHODS

Adult C57BL/6 mice underwent colonoscopy with submucosal injection of 75-100 μL of saline (n = 2) or 0.002% (n = 2), 0.02% (n = 15), or 0.2% (n = 2) benzalkonium chloride (BAC). Each mouse received 1-3 injections in the distal colon and rectum. Mice were sacrificed on postprocedure day 7 or 28. Injection sites were analyzed histologically and with immunostaining for β-tubulin III.

RESULTS

Submucosal injection of 0.02% BAC resulted in megacolon and obliteration of 82 ± 8.8% of myenteric ganglia at the injection site on postprocedure day 7 compared with normal colon. This effect was sustained until day 28. Injection of 0.002% BAC had little effect on the myenteric neuronal network at these time points. Multiple injections of 0.002% or 0.02% BAC (up to three injections per mouse) were well tolerated. Injection of 0.2% BAC caused acute toxicity or death.

CONCLUSIONS

A novel model of chemically ablated enteric nervous system in the mouse colon and rectum is introduced. This model can be valuable in evaluating targeted cell delivery therapies for Hirschsprung disease.

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.

A durable model of Hirschsprung's colon

INTRODUCTION

Hirschsprung's disease is characterized by colonic aganglionosis, curable only by surgical correction. Stem cells may offer regenerative benefits while preventing surgical risks. Existing Hirschsprung's model systems are limited by alimentary compromise and spontaneous ganglionic reconstitution. We endeavored to generate a model of permanent colonic aganglionosis to support longitudinal cell therapy studies.

METHODS

Among adult female Lewis rats (n=11), laparotomy was performed and one-centimeter segments of descending colon were isolated from continuity and denervated by trans-serosal benzalkonium chloride (BAC) exposure. Postoperative weights were plotted. The colon segments were retrieved after 50 or 100days. Immunohistochemical staining (IHC) for beta-III tubulin (TUJ1) and glial fibrillary acid protein (GFAP) revealed colonic ganglia. Muscle layer diameter and the presence of ganglia were contrasted between normal and denervated segments.

RESULTS

All animals survived, experienced 5% weight loss after one week, and then consistently gained weight. Isolated segments had significantly hypertrophied smooth muscle layers compared to normal colon. Ganglia were identified by IHC in normal colonic segments, and denervated colonic segments had no IHC evidence of myenteric ganglia.

CONCLUSION

Colonic segmental isolation and denervation result in an effective model of irreversible colonic aganglionosis. Animals retain alimentary function. Muscularis hypertrophy, myenteric denervation, and normal animal longevity are suitable for long-term studies of cell 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.

A novel in vivo model of permanent intestinal aganglionosis

BACKGROUND

Enteric neuromuscular disease is a characteristic of several disease states, including Hirschsprung disease, esophageal achalasia, Chagas disease, and gastroparesis. Medical therapy for these conditions is limited, and surgical intervention may incur significant morbidity. Alternatively, transplantation of neural progenitor cells may regenerate enteric ganglia. Existing aganglionosis model systems are limited by swift animal demise or by spontaneous regeneration of native ganglia. We propose a novel protocol to induce permanent aganglionosis in a segment of rat jejunum, which may serve as an experimental transplantation target for cellular therapy.

MATERIALS AND METHODS

This protocol was performed in 17 adult female Sprague-Dawley rats. A laparotomy was performed and a 1-cm segment of jejunum was isolated from continuity. Among 14 rats, the isolated segments were treated with benzalkonium chloride (BAC) for 20 min to induce aganglionosis. Jejunal segment isolation was performed without BAC treatment in three rats. The animals were euthanized at posttreatment days 21-166. Muscle layer diameter was compared among normal, isolated, and BAC-treated isolated jejunal segments. The presence of jejunal ganglia was documented by immunohistochemical staining (IHC) for beta-III tubulin (TUJ1) and S100, markers of neuronal and glial cell lineages, respectively.

RESULTS

Ganglia were identified by IHC in normal and isolated jejunal segments. Isolated segments had significantly hypertrophied smooth muscle layers compared with normal jejunum (diameter 343 ± 53 μm versus 211 ± 37 μm, P < 0.0001). BAC-treated jejunal segments had no IHC evidence of ganglionic structures. Aganglionosis was persistent in all specimens up to 166 days after treatment.

CONCLUSIONS

The exclusion of a jejunal segment from continuity and concurrent treatment with BAC results in an effective, reproducible, and permanent model of aganglionosis. Muscular hypertrophy and aganglionosis in the isolated jejunal segment make it an ideal recipient site for transplantation of neuroglial precursor cells.

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.

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.

Transplanted progenitors generate functional enteric neurons in the postnatal colon

Cell therapy has the potential to treat gastrointestinal motility disorders caused by diseases of the enteric nervous system. Many studies have demonstrated that various stem/progenitor cells can give rise to functional neurons in the embryonic gut; however, it is not yet known whether transplanted neural progenitor cells can migrate, proliferate, and generate functional neurons in the postnatal bowel in vivo. We transplanted neurospheres generated from fetal and postnatal intestinal neural crest-derived cells into the colon of postnatal mice. The neurosphere-derived cells migrated, proliferated, and generated neurons and glial cells that formed ganglion-like clusters within the recipient colon. Graft-derived neurons exhibited morphological, neurochemical, and electrophysiological characteristics similar to those of enteric neurons; they received synaptic inputs; and their neurites projected to muscle layers and the enteric ganglia of the recipient mice. These findings show that transplanted enteric neural progenitor cells can generate functional enteric neurons in the postnatal bowel and advances the notion that cell therapy is a promising strategy for enteric neuropathies.