Enteric nervous system development and Hirschsprung's disease: advances in genetic and stem cell studies

The role of enteric nervous system and GDNF in depression: conversation between the brain and the gut

Depression is a debilitating mental disorder that causes a persistent feeling of sadness and loss of interest. Approximately 280 million individuals worldwide suffer from depression by 2023. Despite the heavy medical and social burden imposed by depression, pathophysiology remains incompletely understood. Emerging evidence indicates various bidirectional interplay enable communication between the gut and brain. This interplay provides a link between intestinal and central nervous system as well as feedback from cortical and sensory centers to enteric activities, which also influences physiology and behavior in depression. This review aims to overview the significant role of the enteric nervous system (ENS) in the pathophysiology of depression and gut-brain axis's contribution to depressive disorders. Additionally, we explore the alterations in enteric glia cells (EGCs) and glial cell line-derived neurotrophic factor (GDNF) in depression and their involvement in neuronal support, intestinal homeostasis maintains and immune response activation. Modulating ENS function, EGCs and GDNF level could serve as novel strategies for future antidepressant therapy.

Nobiletin restores HFD-induced enteric nerve injury by regulating enteric glial activation and the GDNF/AKT/FOXO3a/P21 pathway

BACKGROUND

To explore whether nobiletin has a protective effect on high-fat diet (HFD)-induced enteric nerve injury and its underlying mechanism.

METHODS

An obesity model was induced by a HFD. Nobiletin (100 mg/kg and 200 mg/kg) and vehicle were administered by gastric gavage for 4 weeks. Lee's index, body weight, OGTT and intestinal propulsion assays were performed before sacrifice. After sampling, lipids were detected using Bodipy 493/503; lipid peroxidation was detected using MDA and SOD kits and the expression of PGP 9.5, Trem2, GFAP, β-tubulin 3, Bax, Bcl2, Nestin, P75 NTR, SOX10 and EDU was detected using immunofluorescence. The GDNF, p-AKT, AKT, p-FOXO3a, FOXO3a and P21 proteins were detected using western blotting. The relative mRNA expression levels of NOS2 were detected via qPCR. Primary enteric neural stem cells (ENSCs) were cultured. After ENSCs were treated with palmitic acid (PA) and nobiletin, CCK-8 and caspase-3/7 activity assays were performed to evaluate proliferation and apoptosis.

RESULTS

HFD consumption caused colon lipid accumulation and peroxidation, induced enteric nerve damage and caused intestinal motor dysfunction. However, nobiletin reduced lipid accumulation and peroxidation in the colon; promoted Trem2, β-tubulin 3, Nestin, P75NTR, SOX10 and Bcl2 expression; inhibited Bax and GFAP expression; reduced NOS2 mRNA transcription; and regulated the GDNF/AKT/FOXO3a/P21 pathway. Nobiletin also promoted PA-induced impairment of ENSCs.

CONCLUSIONS

Nobiletin restored HFD-induced enteric nerve injury, which may be associated with inhibiting enteric nerve apoptosis, promoting enteric nerve survival and regulating the GDNF/AKT/FOXO3a/P21 pathway.

Genomic stress in diseases stemming from defects in the second brain

This review discusses the less-explored realm of DNA damage and repair within the enteric nervous system (ENS), often referred to as the "second brain." While the central nervous system has been extensively studied for its DNA repair mechanisms and associated neuropathologies, the ENS, which can autonomously coordinate gastrointestinal function, experiences unique challenges and vulnerabilities related to its genome integrity. The susceptibility of the ENS to DNA damage is exacerbated by its limited protective barriers, resulting in not only endogenous genotoxic exposures, such as oxidative stress, but also exogenous threats, such as ingested environmental contaminants, local inflammatory responses, and gut dysbiosis. Here, we discuss the evidence for DNA repair defects in enteric neuropathies, most notably, the reported relationship between inherited mutations in RAD21 and LIG3 with chronic intestinal pseudo-obstruction and mitochondrial gastrointestinal encephalomyopathy disorders, respectively. We also introduce the lesser-recognized gastrointestinal complications in DNA repair syndromes, including conditions like Cockayne syndrome. The review concludes by pointing out the potential role of DNA repair defects in not only congenital disorders but also aging-related gut dysfunction, as well as the crucial need for further research to establish direct causal links between DNA damage accumulation and ENS-specific pathologic phenotypes.

Cinchophen induces RPA1 related DNA damage and apoptosis to impair ENS development of zebrafish

Nonsteroidal anti-inflammatory drugs (NSAIDs) have become contaminants widely distributed in the environment due to improper disposal and discharge. Previous study has found several components might involve in impairing enteric nervous system (ENS) development of zebrafish, including NSAIDs cinchophen. Deficient ENS development in fetal could lead to Hirschsprung disease (HSCR), a congenital neurocristopathy characterized by absence of enteric neurons in hindgut. However, the intrinsic mechanism of neurotoxicity of cinchophen is unclear. We confirmed that cinchophen could impair ENS development of zebrafish and transcriptome sequencing revealed that disfunction of Replication protein A1 (RPA1), which is involved in DNA replication and repairment, might be relevant to the neurotoxicity effects induced by cinchophen. Based on previous data of single cell RNA sequencing (scRNA-seq) of zebrafish gut cells, we observed that rpa1 mainly expressed in proliferating, differentiating ENS cells and neural crest progenitors. Interestingly, cinchophen induced apoptosis and impaired proliferation. Furthermore, cinchophen caused DNA damage and abnormal activation of ataxia telangiectasia mutated/ Rad3 related (ATM/ATR) and checkpoint kinase 2 (CHK2). Finally, molecular docking indicated cinchophen could bind and antagonize RPA1 more effectively. Our study might provide a better understanding and draw more attention to the role of environmental factors in the pathogenesis of HSCR. And the mechanism of cinchophen neurotoxicity would give theoretical guidance for clinical pharmacy.

A review of sources, pathways, and toxic effects of human exposure to benzophenone ultraviolet light filters

Benzophenone ultraviolet light filters (BPs) are high-production-volume chemicals extensively used in personal care products, leading to widespread human exposure. Given their estrogenic properties, the potential health risks associated with exposure to BPs have become a public health concern. This review aims to summarize sources and pathways of exposure to BPs and associated health risks. Dermal exposure, primarily through the use of sunscreens, constitutes a major pathway for BP exposure. At a recommended application rate, dermal exposure of BP-3 via the application of sunscreens may reach or exceed the suggested reference dose. Other exposure pathways to BPs, such as drinking water, seafood, and packaged foods, contribute minimal to the overall dose. Inhalation is a minor pathway of exposure; however, its contribution cannot be ignored. Human exposure to BPs is an order of magnitude higher in North America than in Asia and Europe. Studies conducted on laboratory animals and cells have consistently demonstrated the toxic effects of BP exposure. BPs are estrogenic and elicit reproductive and developmental toxicities. Furthermore, neurotoxicity, hepatotoxicity, nephrotoxicity, and carcinogenicity have been reported from chronic BP exposure. In addition to animal and cell studies, epidemiological investigations have identified associations between BPs and couples' fecundity and other reproductive disorders, as well as adverse birth outcomes. Further studies are urgently needed to understand the risks posed by BPs on human health.

Differential developmental blueprints of organ-intrinsic nervous systems

The organ-intrinsic nervous system is a major interface between visceral organs and the brain, mediating important sensory and regulatory functions in the body-brain axis and serving as critical local processors for organ homeostasis. Molecularly, anatomically, and functionally, organ-intrinsic neurons are highly specialized for their host organs. However, the underlying mechanism that drives this specialization is largely unknown. Here, we describe the differential strategies utilized to achieve organ-specific organization between the enteric nervous system (ENS) 1 and the intrinsic cardiac nervous system (ICNS) 2 , a neuronal network essential for heart performance but poorly characterized. Integrating high-resolution whole-embryo imaging, single-cell genomics, spatial transcriptomics, proteomics, and bioinformatics, we uncover that unlike the ENS which is highly mobile and colonizes the entire gastrointestinal (GI) tract, the ICNS uses a rich set of extracellular matrix (ECM) genes that match with surrounding heart cells and an intermediate dedicated neuronal progenitor state to stabilize itself for a 'beads-on-the-necklace' organization on heart atria. While ICNS- and ENS-precursors are genetically similar, their differentiation paths are influenced by their host-organs, leading to distinct mature neuron types. Co-culturing ENS-precursors with heart cells shifts their identity towards the ICNS and induces the expression of heart-matching ECM genes. Our cross-organ study thus reveals fundamental principles for the maturation and specialization of organ-intrinsic neurons.

Evaluation of a Group-based Patient Education Program Promoting Self-management in Adults with Hirschsprung Disease and Anorectal Malformations

INTRODUCTION

Adults with Hirschsprung disease (HD) and anorectal malformations (ARM) may experience persisting and new somatic and psychosocial problems. Patient education programs (PEPs) may improve self-management in patients with chronic illnesses. The aim of this study was to explore HD and ARM adults' experiences with and evaluation of a group-based PEP. We also looked at factors that might influence the attendance rate.

METHOD

Non-intellectually impaired HD and ARM adults were invited to attend a diagnosis specific PEP at a pelvic floor interdisciplinary center. Eight health care professionals lectured. Aspects of the PEP were graded anonymously in a patient reported experience measure (PREM). Ethical approval was obtained.

RESULTS

17% (21/125) of invited adults (10HD, 11ARM) attended four PEPs. 19/21 (90%) PREMs were returned. Participants found meeting peers and sharing experiences especially valuable in addition to improved disease knowledge. Lectures by the pediatric and colorectal surgeons, stoma nurse, and sexologist were rated highest by the participants. The majority reported that the PEP would be helpful in managing everyday life. All participants recommended PEP in adolescence. Factors such as gender and travel distance did not affect attendance rate, but participants were older than non-participants, median 37 versus 24 years (p = 0.01).

CONCLUSION

Attendance rates were low among HD and ARM adults invited to a PEP, but participants were overall highly satisfied. Peer support, mutual learning, and increased disease knowledge were seen as invaluable assets of the PEP. A web-based PEP was discouraged, while physical PEPs for both adults and adolescents were encouraged.

LEVEL OF EVIDENCE

III.

RET enhancer haplotype-dependent remodeling of the human fetal gut development program

Hirschsprung disease (HSCR) is associated with deficiency of the receptor tyrosine kinase RET, resulting in loss of cells of the enteric nervous system (ENS) during fetal gut development. The major contribution to HSCR risk is from common sequence variants in RET enhancers with additional risk from rare coding variants in many genes. Here, we demonstrate that these RET enhancer variants specifically alter the human fetal gut development program through significant decreases in gene expression of RET, members of the RET-EDNRB gene regulatory network (GRN), other HSCR genes, with an altered transcriptome of 2,382 differentially expressed genes across diverse neuronal and mesenchymal functions. A parsimonious hypothesis for these results is that beyond RET's direct effect on its GRN, it also has a major role in enteric neural crest-derived cell (ENCDC) precursor proliferation, its deficiency reducing ENCDCs with relative expansion of non-ENCDC cells. Thus, genes reducing RET proliferative activity can potentially cause HSCR. One such class is the 23 RET-dependent transcription factors enriched in early gut development. We show that their knockdown in human neuroblastoma SK-N-SH cells reduces RET and/or EDNRB gene expression, expanding the RET-EDNRB GRN. The human embryos we studied had major remodeling of the gut transcriptome but were unlikely to have had HSCR: thus, genetic or epigenetic changes in addition to those in RET are required for aganglionosis.

Enteric neurospheres retain the capacity to assemble neural networks with motile and metamorphic gliocytes and ganglia

BACKGROUND

Neurosphere medium (NSM) and self-renewal medium (SRM) were widely used to isolate enteric neural stem cells (ENSCs) in the form of neurospheres. ENSCs or their neurosphere forms were neurogenic and gliogenic, but the compelling evidence for their capacity of assembling enteric neural networks remained lacking, raising the question of their aptitude for rebuilding the enteric nervous system (ENS) in ENSC therapeutics. It prompted us to explore an effective culture protocol or strategy for assembling ENS networks, which might also be employed as an in vitro model to simplify the biological complexity of ENS embedded in gut walls.

METHODS

NSM and SRM were examined for their capacity to generate neurospheres in mass culture of dispersed murine fetal enterocytes at serially diluted doses and assemble enteric neural networks in two- and three-dimensional cell culture systems and ex vivo on gut explants. Time-lapse microphotography was employed to capture cell activities of assembled neural networks. Neurosphere transplantation was performed via rectal submucosal injection.

RESULTS

In mass culture of dispersed enterocytes, NSM generated discrete units of neurospheres, whereas SRM promoted neural network assembly with neurospheres akin to enteric ganglia. Both were highly affected by seeding cell doses. SRM had similar ENSC mitosis-driving capacity to NSM, but was superior in driving ENSC differentiation in company with heightened ENSC apoptosis. Enteric neurospheres were motile, capable of merging together. It argued against their clonal entities. When nurtured in SRM, enteric neurospheres proved competent to assemble neural networks on two-dimensional coverslips, in three-dimensional hydrogels and on gut explants. In the course of neural network assembly from enteric neurospheres, neurite extension was preceded by migratory expansion of gliocytes. Assembled neural networks contained motile ganglia and gliocytes that constantly underwent shapeshift. Neurospheres transplanted into rectal submucosa might reconstitute myenteric plexuses of recipients' rectum.

CONCLUSION

Enteric neurospheres mass-produced in NSM might assemble neural networks in SRM-immersed two- or three-dimensional environments and on gut explants, and reconstitute myenteric plexuses of the colon after rectal submucosal transplantation. Our results also shed first light on the dynamic entity of ENS and open the experimental avenues to explore cellular activities of ENS and facilitate ENS demystification.

L1cam alternative shorter transcripts encoding the extracellular domains were overexpressed in the intestine of L1cam knockdown mice

Hirschsprung disease (HSCR) is a congenital disorder of functional bowel obstruction due to the absence of enteric ganglia in distal bowel. Different L1cam variants were reportedly associated with L1cam syndrome and HSCR, whose phenotypes lacked predictable relevance to their genotypes. Using next-generation sequencing (NGS), we found an L1CAM de novo frameshift mutation in a female with mild hydrocephalus and skip-type HSCR. A nearly identical L1cam variant was introduced into FVB/NJ mice via the CRISPR-EZ method. A silent mutation was created via ssODN to gain an artificial Ncol restriction enzyme site for easier genotyping. Six L1cam protein-coding alternative transcripts were quantitatively measured. Immunofluorescence staining with polyclonal and monoclonal L1cam antibodies was used to characterize L1cam isoform proteins in enteric ganglia. Fifteen mice, seven males and eight females, generated via CRISPR-EZ, were confirmed to carry the L1cam frameshift variant, resulting in a premature stop codon. There was no prominent hydrocephalus nor HSCR-like presentation in these mice, but male infertility was noticed after observation for three generations in a total of 176 mice. Full-length L1cam transcripts were detected at a very low level in the intestinal tissues and almost none in the brain of these mice. Alternative shorter transcripts encoding the extracellular domains were overexpressed in the intestine of L1cam knockdown mice. Immunofluorescence confirmed no fulllength L1cam protein in enteric ganglia. These shorter L1cam isoform proteins might play a role in protecting L1cam knockdown mice from HSCR.

A branching model of lineage differentiation underpinning the neurogenic potential of enteric glia

Glial cells have been proposed as a source of neural progenitors, but the mechanisms underpinning the neurogenic potential of adult glia are not known. Using single cell transcriptomic profiling, we show that enteric glial cells represent a cell state attained by autonomic neural crest cells as they transition along a linear differentiation trajectory that allows them to retain neurogenic potential while acquiring mature glial functions. Key neurogenic loci in early enteric nervous system progenitors remain in open chromatin configuration in mature enteric glia, thus facilitating neuronal differentiation under appropriate conditions. Molecular profiling and gene targeting of enteric glial cells in a cell culture model of enteric neurogenesis and a gut injury model demonstrate that neuronal differentiation of glia is driven by transcriptional programs employed in vivo by early progenitors. Our work provides mechanistic insight into the regulatory landscape underpinning the development of intestinal neural circuits and generates a platform for advancing glial cells as therapeutic agents for the treatment of neural deficits.

mRNA sequencing provides new insights into the pathogenesis of Hirschsprung's disease in mice

PURPOSE

The aim of this study is to use RNA sequencing and RT-qPCR to identify the main susceptibility genes linked to the occurrence and development of Hirschsprung disease in the colonic tissues of EDNRBm1yzcm and wild mice.

METHODS

RNA was extracted from colon tissues of 3 mutant homozygous mice and 3 wild mice. RNA degradation, contamination concentration, and integrity were then measured. The extracted RNA was then sequenced using the Illumina platform. The obtained sequence data are filtered to ensure data quality and compared to the reference genome for further analysis. DESeq2 was used for gene expression analysis of the raw data. In addition, graphene oxide enrichment analysis and RT-qPCR validation were also performed.

RESULTS

This study identified 8354 differentially expressed genes in EDNRBm1yzcm and wild mouse colon tissues by RNA sequencing, including 4346 upregulated genes and 4005 downregulated genes. Correspondingly, the results of RT-qPCR analysis showed good correlation with the transcriptome data. In addition, GO and KEGG enrichment results suggested that there were 8103 terms and 320 pathways in all DEGs. When P < 0.05, 1081 GO terms and 320 KEGG pathways reached a significant level. Finally, through the existing studies and the enrichment results of differentially expressed genes, it was determined that axon guidance and the focal adhesion pathway may be closely related to the occurrence of HSCR.

CONCLUSIONS

This study analyzed and identified the differential genes in colonic tissues between EDNRBm1yzcm mice and wild mice, which provided new insight for further mining the potential pathogenic genes of Hirschsprung's disease.

Mini-review: "Enteric glia functions in nervous tissue repair: Therapeutic target or tool?"

In the body, nerve tissue is not only present in the central nervous system, but also in the periphery. The enteric nervous system (ENS) is a highly organized intrinsic network of neurons and glial cells grouped to form interconnected ganglia. Glial cells in the ENS are a fascinating cell population: their neurotrophic role is well established, as well as their plasticity in specific circumstances. Gene expression profiling studies indicate that ENS glia retain neurogenic potential. The identification of neurogenic glial subtype(s) and the molecular basis of glia-derived neurogenesis may have profound biological and clinical implications. In this review, we discuss the potential of using gene-editing for ENS glia and cell transplantation as therapies for enteric neuropathies. Glia in the ENS: target or tool for nerve tissue repair?

Accuracy of Anorectal Manometry to Detect the Rectoanal Inhibitory Reflex in Children: Awake Versus Under General Anesthesia

OBJECTIVES

Our objective was to investigate if there is a difference in the detection of the rectoanal inhibitory reflex (RAIR) when an anorectal manometry (ARM) is performed awake or under general anesthesia.

METHODS

A retrospective review of ARM studies was performed to identify children who had undergone ARMs both while awake and under general anesthesia. We compared ARM outcomes including the detection of the RAIR and anal canal resting pressure.

RESULTS

Thirty-four children had received ARMs both while awake and under general anesthesia (53% female, median age at first ARM 7.5 years [range 3-18 years]). In 9 of 34 (26%) children the RAIR was solely identified during ARM under general anesthesia and not during ARM while awake. In 6 of 9 (66%) this was unrelated to the balloon volumes used during balloon inflations. In 4 of 34 (12%) children, assessment of the RAIR was inconclusive during ARM under general anesthesia due to too low, or loss of anal canal pressure. In 2 of those children, ARMs while awake showed presence of a RAIR. Anal canal resting pressures were higher during ARM while awake versus ARM under general anesthesia (median 70 [interquartile range, IQR 59-85] vs 46 mmHg [IQR 36-65] respectively, P < 0.001).

CONCLUSIONS

General anesthesia may affect the detection of a RAIR in 2 ways. On the one hand, it may facilitate better visualization in children in whom a RAIR could not be visualized while awake. On the other hand, it may cause a loss of anal canal pressure resulting in an inconclusive test result.

Regenerative medicine: current research and perspective in pediatric surgery

The field of regenerative medicine, encompassing several disciplines including stem cell biology and tissue engineering, continues to advance with the accumulating research on cell manipulation technologies, gene therapy and new materials. Recent progress in preclinical and clinical studies may transcend the boundaries of regenerative medicine from laboratory research towards clinical reality. However, for the ultimate goal to construct bioengineered transplantable organs, a number of issues still need to be addressed. In particular, engineering of elaborate tissues and organs requires a fine combination of different relevant aspects; not only the repopulation of multiple cell phenotypes in an appropriate distribution but also the adjustment of the host environmental factors such as vascularisation, innervation and immunomodulation. The aim of this review article is to provide an overview of the recent discoveries and development in stem cells and tissue engineering, which are inseparably interconnected. The current status of research on tissue stem cells and bioengineering, and the possibilities for application in specific organs relevant to paediatric surgery have been specifically focused and outlined.

L1CAM expression in human gastrointestinal tract development: From tongue to colon-rectum

Background

L1CAM (L1 cell adhesion molecule) is a member of the L1 family of neural adhesion molecules, involved in the development of multiple organs and tissues, including kidneys, the enteric nervous system, and adrenal glands. The aim of this study was to analyze, at the immunohistochemical level, the expression of L1CAM in the human tongue, parotid glands, and the different segments of the gastrointestinal tract during human development.

Design and method

Immunohistochemical analysis for L1CAM was performed in the human tongue, parotid glands, and in the different segments of the gastrointestinal tract during development, starting from the 8th up to the 32nd week of gestation.

Results

Our results were given by the expression of the L1CAM protein in different segments of the gastrointestinal tract during development, starting from the 8th week up to the 32nd week of gestation. L1CAM-reactive cells appeared aggregated in small bodies, irregular in shape, showing L1CAM storage in the cytoplasm. L1CAM expressing bodies were frequently found to be connected one to the next by thin fibers, a finding suggestive of the existence of an L1CAM network inside the developing tissue.

Conclusion

Our study confirms that L1CAM is involved in gut development, as well as in tongue and salivary gland development. These findings confirm that the role of L1CAM in fetal development is not restricted to the central nervous system and are necessary for further studies on the role of this molecule in human development.

hPSC-derived sacral neural crest enables rescue in a severe model of Hirschsprung's disease

The enteric nervous system (ENS) is derived from both the vagal and sacral component of the neural crest (NC). Here, we present the derivation of sacral ENS precursors from human PSCs via timed exposure to FGF, WNT, and GDF11, which enables posterior patterning and transition from posterior trunk to sacral NC identity, respectively. Using a SOX2::H2B-tdTomato/T::H2B-GFP dual reporter hPSC line, we demonstrate that both trunk and sacral NC emerge from a double-positive neuro-mesodermal progenitor (NMP). Vagal and sacral NC precursors yield distinct neuronal subtypes and migratory behaviors in vitro and in vivo. Remarkably, xenografting of both vagal and sacral NC lineages is required to rescue a mouse model of total aganglionosis, suggesting opportunities in the treatment of severe forms of Hirschsprung's disease.

A distinct transcriptome characterizes neural crest-derived cells at the migratory wavefront during enteric nervous system development

Enteric nervous system development relies on intestinal colonization by enteric neural crest-derived cells (ENCDCs). This is driven by a population of highly migratory and proliferative ENCDCs at the wavefront, but the molecular characteristics of these cells are unknown. ENCDCs from the wavefront and the trailing region were isolated and subjected to RNA-seq. Wavefront-ENCDCs were transcriptionally distinct from trailing ENCDCs, and temporal modelling confirmed their relative immaturity. This population of ENCDCs exhibited altered expression of ECM and cytoskeletal genes, consistent with a migratory phenotype. Unlike trailing ENCDCs, the wavefront lacked expression of genes related to neuronal or glial maturation. As wavefront ENCDC genes were associated with migration and developmental immaturity, the genes that remain expressed in later progenitor populations may be particularly pertinent to understanding the maintenance of ENCDC progenitor characteristics. Dusp6 expression was specifically upregulated at the wavefront. Inhibiting DUSP6 activity prevented wavefront colonization of the hindgut, and inhibited the migratory ability of post-colonized ENCDCs from midgut and postnatal neurospheres. These effects were reversed by simultaneous inhibition of ERK signaling, indicating that DUSP6-mediated ERK inhibition is required for ENCDC migration in mouse and chick.

KIF26A is mutated in the syndrome of congenital hydrocephalus with megacolon

Human disorders of the enteric nervous system (ENS), e.g., Hirschsprung's disease, are rarely associated with major central nervous system involvement. We describe two families each segregating a different homozygous truncating variant in KIF26A with a unique constellation of severe megacolon that resembles Hirschsprung's disease but lacks aganglionosis as well as brain malformations that range from severe to mild. The intestinal phenotype bears a striking resemblance to that observed in Kif26a^-/- mice where KIF26A deficiency was found to cause abnormal GDNF-Ret signaling resulting in failure to establish normal neuronal networks despite myenteric neuronal hyperplasia. Very recently, a range of brain developmental phenotypes were described in patients and mice with KIF26A deficiency and were found to result from abnormal radial migration and increased apoptosis. Our report, therefore, reveals a recognizable autosomal-recessive human KIF26A deficiency phenotype characterized by severe ENS dysfunction and a range of brain malformations.

Ileal atresia and total colonic hirschsprung disease in a 36-week neonate: A case report

Intestinal atresia and hirschsprung disease are two common causes of bowel obstruction in neonates; simultaneous occurrence is rare. This report delineates a 36-week newborn with ileal atresia and total colonic hirschsprung who was referred to our unit due to failure of meconium passage during the first 48 h after birth.

The m6A methyltransferase METTL3 affects cell proliferation and migration by regulating YAP expression in Hirschsprung disease

BACKGROUND

METTL3, an mRNA m⁶A methyltransferase, has been implicated in various steps of mRNA metabolism, such as stabilization, splicing, nuclear transportation, translation, and degradation. However, whether METTL3 dysregulation is involved in Hirschsprung disease (HSCR) development remains unclear. In this study, we preliminarily elucidated the role of METTL3 in HSCR and sought to identify the associated molecular mechanism.

METHODS

The gene expression levels of YAP and several methyltransferases, demethylases, and effectors were evaluated by RT-qPCR. Protein levels were evaluated by western blot and immunohistochemistry. Cell proliferation and migration were detected by CCK-8 and Transwell assays, respectively. The overall levels of m⁶A modification were determined by colorimetry.

RESULTS

We found that m⁶A levels were reduced in the stenotic intestinal tissue of patients with HSCR. When METTL3 was knocked down in SH-SY5Y and HEK-293T cells, the proliferative and migratory abilities of the cells were inhibited, m⁶A modification levels were reduced, and YAP expression was increased. Importantly, YAP and METTL3 expression displayed a negative correlation in both cell lines as well as in HSCR tissue.

CONCLUSIONS

Our results provide evidence for an interaction between METTL3 and YAP in HSCR, and further suggest that METTL3 is involved in the pathogenesis of HSCR by regulating neural crest cell proliferation and migration upstream of YAP.

A Single RET Mutation in Hirschsprung Disease Induces Intestinal Aganglionosis Via a Dominant-Negative Mechanism

BACKGROUND & AIMS

Hirschsprung disease (HSCR) is a congenital disorder characterized by the absence of the enteric nervous system (ENS). HSCR potentially involves multiple gene aberrations and displays complex patterns of inheritance. Mutations of the RET gene, encoding the RET receptor tyrosine kinase, play a central role in the pathogenesis of HSCR. Although a wide variety of coding RET mutations have been identified, their pathogenetic significance in vivo has remained largely unclear.

METHODS

We introduced a HSCR-associated RET missense mutation, RET(S811F), into the corresponding region (S812) of the mouse Ret gene. Pathogenetic impact of Ret(S812F) was assessed by histologic and functional analyses of the ENS and by biochemical analyses. Interactions of the Ret(S812F) allele with HSCR susceptibility genes, the RET9 allele and the Ednrb gene, were examined by genetic crossing in mice.

RESULTS

Ret^S812F/+ mice displayed intestinal aganglionosis (incidence, 50%) or hypoganglionosis (50%), impaired differentiation of enteric neurons, defecation deficits, and increased lethality. Biochemical analyses revealed that Ret(S811F) protein was not only kinase-deficient but also abrogated function of wild-type RET in trans. Moreover, the Ret(S812F) allele interacted with other HSCR susceptibility genes and caused intestinal aganglionosis with full penetrance.

CONCLUSIONS

This study demonstrates that a single RET missense mutation alone induces intestinal aganglionosis via a dominant-negative mechanism. The Ret^S812F/+ mice model HSCR displays dominant inheritance with incomplete penetrance and serves as a valuable platform for better understanding of the pathogenetic mechanism of HSCR caused by coding RET mutations.

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.

Intrauterine exposure to oxidative stress induces caspase-1-dependent enteric nerve cell pyroptosis

PURPOSE

This study determined whether oxidative stress causes the developmental abnormalities of the enteric nervous system during the embryonic period.

METHODS

Using the test results of tissue specimens of children with Hirschsprung disease (HSCR), we established a pregnant rat model of oxidative stress and a cellular oxidative stress model to conduct related molecular, cellular, and histopathological experiments for exploration and validation.

RESULTS

The results of the quantitative real-time polymerase chain reaction assay indicated overexpression of pyroptosis markers (NLRP3, ASC, and caspase-1) in HSCR lesions and newborn pups in the oxidative stress group (treated with D-galactose). The expression of cathepsin D was significantly decreased in intestinal tissues of newborn pups in the oxidative stress group compared to the control group. Reactive oxygen species scavengers (N-acetyl-cysteine, NAC), the caspase-1 inhibitor (VX-765), and the NLRP3 siRNA could reverse the release of LDH, decrease the number of propidium iodide stained cells, and reduce the percentage of TUNEL/caspase-3 double-positive cells in the H₂O₂-treated group.

CONCLUSION

Oxidative stress can induce the death of enteric nerve cells by activating caspase-1-dependent pyroptosis through NLRP3 inflammasomes, which may contribute to abnormal enteric nervous system development.

In toto imaging of early enteric nervous system development reveals that gut colonization is tied to proliferation downstream of Ret

The enteric nervous system is a vast intrinsic network of neurons and glia within the gastrointestinal tract and is largely derived from enteric neural crest cells (ENCCs) that emigrate into the gut during vertebrate embryonic development. Study of ENCC migration dynamics and their genetic regulators provides great insights into fundamentals of collective cell migration and nervous system formation, and these are pertinent subjects for study due to their relevance to the human congenital disease Hirschsprung disease (HSCR). For the first time, we performed in toto gut imaging and single-cell generation tracing of ENCC migration in wild type and a novel ret heterozygous background zebrafish (retwmr1/+) to gain insight into ENCC dynamics in vivo. We observed that retwmr1/+ zebrafish produced fewer ENCCs localized along the gut, and these ENCCs failed to reach the hindgut, resulting in HSCR-like phenotypes. Specifically, we observed a proliferation-dependent migration mechanism, where cell divisions were associated with inter-cell distances and migration speed. Lastly, we detected a premature neuronal differentiation gene expression signature in retwmr1/+ ENCCs. These results suggest that Ret signaling may regulate maintenance of a stem state in ENCCs.

Human Pluripotent Stem Cell-Based Models for Hirschsprung Disease: From 2-D Cell to 3-D Organoid Model

Hirschsprung disease (HSCR) is a complex congenital disorder caused by defects in the development of the enteric nervous system (ENS). It is attributed to failures of the enteric neural crest stem cells (ENCCs) to proliferate, differentiate and/or migrate, leading to the absence of enteric neurons in the distal colon, resulting in colonic motility dysfunction. Due to the oligogenic nature of the disease, some HSCR conditions could not be phenocopied in animal models. Building the patient-based disease model using human induced pluripotent stem cells (hPSC) has opened up a new opportunity to untangle the unknowns of the disease. The expanding armamentarium of hPSC-based therapies provides needed new tools for developing cell-replacement therapy for HSCR. Here we summarize the recent studies of hPSC-based models of ENS in 2-D and 3-D culture systems. These studies have highlighted how hPSC-based models complement the population-based genetic screens and bioinformatic approaches for the discovery of new HSCR susceptibility genes and provide a human model for the close-to-physiological functional studies. We will also discuss the potential applications of these hPSC-based models in translational medicines and their advantages and limitations. The use of these hPSC-based models for drug discovery or cell replacement therapy likely leads to new treatment strategies for HSCR in the future. Further improvements in incorporating hPSC-based models with the human-mouse chimera model and organ-on-a-chip system for establishing a better disease model of HSCR and for drug discovery will further propel us to success in the development of an efficacious treatment for HSCR.

Circ-ITCH overexpression promoted cell proliferation and migration in Hirschsprung disease through miR-146b-5p/RET axis

BACKGROUND

Hirschsprung disease (HSCR) is a congenital intestinal disease caused by the abnormal proliferation and migration of enteric nerve cells (ENCC). Research suggested critical roles for circular RNA (circRNA) itchy E3 ubiquitin protein ligase (ITCH) in gastrointestinal malignancies progression. However, the function of circ-ITCH in HSCR remains poorly defined.

METHODS

The related genes expression in 30 HSCR patients and 30 controls without HSCR were detected using qRT-PCR. Cell proliferation was assessed by CCK-8 assay and EdU assay. Cell migration was detected with wound-healing assay and transwell assay. The interactions among circ-ITCH, miR-146b-5p, and RET were confirmed by Dual luciferase reporter assay.

RESULTS

Circ-ITCH and RET expressions were downregulated in HSCR patients and cells, while the miR-146b-5p expression was upregulated. Circ-ITCH overexpression facilitated cell proliferation, migration, and activated MAPK pathway, which were reversed by circRNA-ITCH knockdown. Circ-ITCH negatively regulated miR-146b-5p expression. MiR-146b-5p overexpression abolished the promoting effects of circ-ITCH overexpression on cell proliferation and migration. MiR-146b-5p inhibited RET expression. RET overexpression eliminated the inhibitory effects of miR-146b-5p overexpression on cell proliferation and migration.

CONCLUSION

Circ-ITCH overexpression facilitated cell proliferation and migration in HSCR by regulating miR-146b-5p/RET/MAPK axis.

IMPACT

The expressions of Circ-ITCH and RET were markedly reduced in HSCR, while miR-146b-5p expression was increased in HSCR. Circ-ITCH overexpression enhanced the proliferative and migratory abilities of SH-SY5Y and 293T cells. Circ-ITCH negatively regulated miR-146b-5p expression.

Lactobacillus rhamnosus GG normalizes gut dysmotility induced by environmental pollutants via affecting serotonin level in zebrafish larvae

Intestinal peristalsis is essential for gastrointestinal function, which could maintain the appropriate progression and digestion of food and reduce bacterial aggregation through mixing function. Even though certain ingredients of foodstuff are known to increase or decrease intestinal peristalsis, the role of environmental pollutants on intestinal peristalsis is relatively unknown. Therefore, the effects of four typical environmental pollutants (oxytetracycline, arsenic, polychlorinated biphenyls and chlorpyrifos) on intestinal peristalsis in the zebrafish model and then tested the recovery effect of the constipation-resistant probiotic. The results showed that 4-day environmental pollutants exposures on the zebrafish embryos at 1 day post fertilization clearly decreased the intestinal peristalsis through decreasing the serotonin (5-HT) production and down-regulating the expression of key genes involved in 5-HT synthesis. Pollutants-evoked change of gut motility could be normalized in the presence of Lactobacillus rhamnosus GG (LGG) via increasing 5-HT secretion. Exogenous 5-hydroxytryptophan (100 µg/L) could also rescue the dysfunction of gut motility in pollutants-treated zebrfish. The data identified that LGG normalized disorder of intestinal peristalsis induced by environmental pollutants through increasing 5-HT level. The stimulant effect of LGG on peristalsis may be associated with 5-HT system, which could provide references for the application of probiotics in regulation of gut dysmotility.

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 complex involvement of the digestive tract in human defense behavior - structural and functional arguments

The digestive system has an innate monitoring and defense capacity, which allows the recognition and elimination of different dangerous substances. The complex analysis of the intestinal content comprises the cross-interactions between the epithelial cells, the enteroendocrine cells, the neural tissue and the cellular defense mechanisms. The enteric nervous system, also called "the enteric brain" or "the second brain" is the only neuronal network outside the central nervous system capable of autonomous reflex activity. The enteric nervous system activity is mostly independent of the central nervous system, but not in all aspects. In fact, even the enteral reflexes are a consequence of the bidirectional intestine-brain relation. The central nervous and enteric nervous systems are coupled through the sympathetic and parasympathetic branches of the autonomic nervous system. The gastrointestinal functions are regulated due to the interaction between the intrinsic neurons within the gastrointestinal wall and the extrinsic neurons outside the gastrointestinal tract. Here we provide an overview of the important role of the enteric brain in defensive behavior, as well as its structural and functional particularities that make it a special organ.

CircRNA ITCH: Insight Into Its Role and Clinical Application Prospect in Tumor and Non-Tumor Diseases

CircRNA E3 ubiquitin protein ligase (ITCH) (circRNA ITCH, circ-ITCH), a stable closed-loop RNA derived from the 20q11.22 region of chromosome 20, is a new circRNA discovered in the cytoplasm in recent decades. Studies have shown that it does not encode proteins, but regulates proteins expression at different levels. It is down-regulated in tumor diseases and is involved in a number of biological activities, including inhibiting cell proliferation, migration, invasion, and promoting apoptosis. It can also alter disease progression in non-tumor disease by affecting the cell cycle, inflammatory response, and critical proteins. Circ-ITCH also holds a lot of promise in terms of tumor and non-tumor clinical diagnosis, prognosis, and targeted therapy. As a result, in order to aid clinical research in the hunt for a new strategy for diagnosing and treating human diseases, this study describes the mechanism of circ-ITCH as well as its clinical implications.

Present and future avenues of cell-based therapy for brain injury: The enteric nervous system as a potential cell source

Cell therapy is a promising strategy in the field of regenerative medicine; however, several concerns limit the effective clinical use, namely a valid cell source. The gastrointestinal tract, which contains a highly organized network of nerves called the enteric nervous system (ENS), is a valuable reservoir of nerve cells. Together with neurons and neuronal precursor cells, it contains glial cells with a well described neurotrophic potential and a newly identified neurogenic one. Recently, enteric glia is looked at as a candidate for cell therapy in intestinal neuropathies. Here, we present the therapeutic potential of the ENS as cell source for brain repair, too. The example of stroke is introduced as a brain injury where cell therapy appears promising. This disease is the first cause of handicap in adults. The therapies developed in recent years allow a partial response to the consequences of the disease. The only prospect of recovery in the chronic phase is currently based on rehabilitation. The urgency to offer other treatments is therefore tangible. In the first part of the review, some elements of stroke pathophysiology are presented. An update on the available therapeutic strategies is provided, focusing on cell‐ and biomaterial‐based approaches. Following, the ENS is presented with its anatomical and functional characteristics, focusing on glial cells. The properties of these cells are depicted, with particular attention to their neurotrophic and, recently identified, neurogenic properties. Finally, preliminary data on a possible therapeutic approach combining ENS‐derived cells and a biomaterial are presented.

Molecular profiling of enteric nervous system cell lineages

The enteric nervous system (ENS) is an extensive network of enteric neurons and glial cells that is intrinsic to the gut wall and regulates almost all aspects of intestinal physiology. While considerable advancement has been made in understanding the genetic programs regulating ENS development, there is limited understanding of the molecular pathways that control ENS function in adult stages. One of the limitations in advancing the molecular characterization of the adult ENS relates to technical difficulties in purifying healthy neurons and glia from adult intestinal tissues. To overcome this, we developed novel methods for performing transcriptomic analysis of enteric neurons and glia, which are based on the isolation of fluorescently labeled nuclei. Here we provide a step-by-step protocol for the labeling of adult mouse enteric neuronal nuclei using adeno-associated-virus-mediated gene transfer, isolation of the labeled nuclei by fluorimetric analysis, RNA purification and nuclear RNA sequencing. This protocol has also been adapted for the isolation of enteric neuron and glia nuclei from myenteric plexus preparations from adult zebrafish intestine. Finally, we describe a method for visualization and quantification of RNA in myenteric ganglia: Spatial Integration of Granular Nuclear Signals (SIGNS). By following this protocol, it takes ~3 d to generate RNA and create cDNA libraries for nuclear RNA sequencing and 4 d to carry out high-resolution RNA expression analysis on ENS tissues.

Opioid Use, Gut Dysbiosis, Inflammation, and the Nervous System

Opioid use disorder (OUD) is defined as the chronic use or misuse of prescribed or illicitly obtained opioids and is characterized by clinically significant impairment. The etiology of OUD is multifactorial as it is influenced by genetics, environmental factors, stress response and behavior. Given the profound role of the gut microbiome in health and disease states, in recent years there has been a growing interest to explore interactions between the gut microbiome and the central nervous system as a causal link and potential therapeutic source for OUD. This review describes the role of the gut microbiome and opioid-induced immunopathological disturbances at the gut epithelial surface, which collectively contribute to OUD and perpetuate the vicious cycle of addiction and relapse.

Adult enteric Dclk1-positive glial and neuronal cells reveal distinct responses to acute intestinal injury

Intestinal ganglionic cells in the adult enteric nervous system (ENS) are continually exposed to stimuli from the surrounding microenvironment and need at times to respond to disturbed homeostasis following acute intestinal injury. The kinase DCLK1 and intestinal Dclk1-positive cells have been reported to contribute to intestinal regeneration. Although Dclk1-positive cells are present in adult enteric ganglia, their cellular identity and response to acute injury have not been investigated in detail. Here, we reveal the presence of distinct Dclk1-tdTom+/CD49b+ glial-like and Dclk1-tdTom+/CD49b- neuronal cell types in adult myenteric ganglia. These ganglionic cells demonstrate distinct patterns of tracing over time yet show a similar expansion in response to elevated serotonergic signaling. Interestingly, Dclk1-tdTom+ glial-like and neuronal cell types appear resistant to acute irradiation injury-mediated cell death. Moreover, Dclk1-tdTom+/CD49b+ glial-like cells show prominent changes in gene expression profiles induced by injury, in contrast to Dclk1-tdTom+/CD49b- neuronal cell types. Finally, subsets of Dclk1-tdTom+/CD49b+ glial-like cells demonstrate prominent overlap with Nestin and p75NTR and strong responses to elevated serotonergic signaling or acute injury. These findings, together with their role in early development and their neural crest-like gene expression signature, suggest the presence of reserve progenitor cells in the adult Dclk1 glial cell lineage.NEW & NOTEWORTHY The kinase DCLK1 identifies glial-like and neuronal cell types in adult murine enteric ganglia, which resist acute injury-mediated cell death yet differ in their cellular response to injury. Interestingly, Dclk1-labeled glial-like cells show prominent transcriptional changes in response to injury and harbor features reminiscent of previously described enteric neural precursor cells. Our data thus add to recently emerging evidence of reserve cellular plasticity in the adult enteric nervous system.

Multiple Roles of Ret Signalling During Enteric Neurogenesis

The majority of the enteric nervous system is formed by vagal neural crest cells which enter the foregut and migrate rostrocaudally to colonise the entire length of the gastrointestinal tract. Absence of enteric ganglia from the distal colon are the hallmark of Hirschsprung disease, a congenital disorder characterised by severe intestinal dysmotility. Mutations in the receptor tyrosine kinase RET have been identified in approximately 50% of familial cases of Hirschsprung disease but the cellular processes misregulated in this condition remain unclear. By lineage tracing neural crest cells in mice homozygous for a knock-in allele of Ret (Ret^51/51), we demonstrate that normal activity of this receptor is required in vivo for the migration of enteric nervous system progenitors throughout the gut. In mutant mice, progenitors of enteric neurons fail to colonise the distal colon, indicating that failure of colonisation of the distal intestine is a major contributing factor for the pathogenesis of Hirschsprung disease. Enteric nervous system progenitors in the ganglionic proximal guts of mutant mice are also characterised by reduced proliferation and differentiation. These findings suggest that the functional abnormalities in Hirschsprung disease result from a combination of colonic aganglionosis and deficits in neuronal circuitry of more proximal gut segments. The reduced neurogenesis in the gut of Ret^51/51 mutants was reproduced in the multilineage enteric nervous system progenitors isolated from these animals. Correction of the molecular defects of such progenitors fully restored their neurogenic potential in culture. These observations enhance our understanding of the pathogenesis of Hirschsprung disease and highlight potential approaches for its treatment.

Prucalopride might improve intestinal motility by promoting the regeneration of the enteric nervous system in diabetic rats

The present study aimed to investigate whether prucalopride, as a 5-hydroxytryptamine 4 (5-HT4) receptor agonist, improved intestinal motility by promoting the regeneration of the enteric nervous system (ENS) in rats with diabetes mellitus (DM). A rat model of DM was established using an intraperitoneal injection of streptozotocin. The rats were randomly divided into four groups of 6 rats/group: Control, DM (DM model), DM + A (5 µg/kg prucalopride) and DM + B (10 µg/kg prucalopride). The rats in the Control group were given an equal volume of citric acid solvent. After successful model establishment, high blood glucose levels were maintained for 2 weeks before administration of prucalopride. The colonic transit time was measured using the glass bead discharge method. It was revealed that the colonic transit time of diabetic rats was the longest, and this was significantly shortened in the DM + B group. Subsequently, the colons were collected. The expression levels of Nestin, glial fibrillary acidic protein (GFAP), SOX10, RNA-binding protein human antigen D (HuD) and ubiquitin thiolesterase (PGP9.5) were determined via immunohistochemical analysis. Immunofluorescence double staining of 5-HT4 + Nestin and Ki67 + Nestin was performed. The 5-HT level was measured using ELISA. Compared with that in the control group, Nestin expression was significantly increased in the DM and DM + A groups, and it was concentrated in columnar epithelial cells and the mesenchyme. Furthermore, the expression levels of Nestin in the DM + A group were higher than those in the DM group. No difference was observed in the expression levels of Nestin between the DM + B group and the Control group. The expression levels of 5-HT protein were highest in the Control group; however, the expression levels of 5-HT protein in the DM group, DM + A group and DM + B group exhibited an increasing trend. Similar trends in the expression of 5-HT4 and Nestin were not observed; however, similar trends in the expression of Nestin and Ki67 were observed. The expression levels of GFAP, SOX10, PGP9.5 and Ki67 in the DM + A and DM + B groups were higher compared with those in the DM group. In the DM + A group, HuD expression was decreased compared with that in the Control group but it was markedly higher compared with that in the DM group. In conclusion, prucalopride may improve intestinal motility by promoting ENS regeneration in rats with DM.

Similarities and differences between nigral and enteric dopaminergic neurons unravel distinctive involvement in Parkinson's disease

In addition to the well-known degeneration of midbrain dopaminergic neurons, enteric neurons can also be affected in neurodegenerative disorders such as Parkinson's disease (PD). Dopaminergic neurons have recently been identified in the enteric nervous system (ENS). While ENS dopaminergic neurons have been shown to degenerate in genetic mouse models of PD, analyses of their survival in enteric biopsies of PD patients have provided inconsistent results to date. In this context, this review seeks to highlight the distinctive and shared factors and properties that control the evolution of these two sets of dopaminergic neurons from neuronal precursors to aging neurons. Although their cellular sources and developmental times of origin differ, midbrain and ENS dopaminergic neurons express many transcription factors in common and their respective environments express similar neurotrophic molecules. For example, Foxa2 and Sox6 are expressed by both populations to promote the specification, differentiation, and long-term maintenance of the dopaminergic phenotype. Both populations exhibit sustained patterns of excitability that drive intrinsic vulnerability over time. In disorders such as PD, colon biopsies have revealed aggregation of alpha-synuclein in the submucosal plexus where dopaminergic neurons reside and lack blood barrier protection. Thus, these enteric neurons may be more susceptible to neurotoxic insults and aggregation of α-synuclein that spreads from gut to midbrain. Under sustained stress, inefficient autophagy leads to neurodegeneration, GI motility dysfunction, and PD symptoms. Recent findings suggest that novel neurotrophic factors such as CDNF have the potential to be used as neuroprotective agents to prevent and treat ENS symptoms of PD.

The science of Hirschsprung disease: What we know and where we are headed

The enteric nervous system (ENS) is a rich network of neurons and glial cells that comprise the gastrointestinal tract's intrinsic nervous system and are responsible for controlling numerous complex functions, including digestion, transit, secretion, barrier function, and maintenance of a healthy microbiome. Development of a functional ENS relies on the coordinated interaction between enteric neural crest-derived cells and their environment as the neural crest-derived cells migrate rostrocaudally along the embryonic gut mesenchyme. Congenital or acquired disruption of ENS development leads to various neurointestinal diseases. Hirschsprung disease is a congenital neurocristopathy, a disease of the neural crest. It is characterized by a variable length of distal colonic aganglionosis due to a failure in enteric neural crest-derived cell proliferation, migration, differentiation, and/or survival. In this review, we will review the science of Hirschsprung disease, targeting an audience of pediatric surgeons. We will discuss the basic biology of normal ENS development, as well as what goes awry in ENS development in Hirschsprung disease. We will review animal models that have been integral to studying this disease, as well as current hot topics and future research, including genetic risk profiling, stem cell therapy, non-invasive diagnostic techniques, single-cell sequencing techniques, and genotype-phenotype correlation.

Diagnostic Efficacy of Rectal Suction Biopsy with Regard to Weight in Children Investigated for Hirschsprung's Disease

BACKGROUND/AIM

Diagnostic efficacy, defined as the percentage of rectal suction biopsy (RSB) specimens sufficient enough to determine the absence of ganglia cells in Hirschsprung's disease (HD) diagnosis, has been reported to be low, requiring repeated biopsies. The aim was to explore whether RSB diagnostic efficacy was influenced by the child's weight and to ascertain whether RSB efficacy differed between aganglionic and ganglionic tissue.

MATERIALS AND METHODS

Efficacy analyses were conducted in a national HD-center's register on children 0-15 kg, examined between 2011-2019. First-time RSB diagnostic efficacy was correlated to the children's weight and final HD diagnosis.

RESULTS

Among the 84 children who had first-time RSB, the overall diagnostic efficacy was 85% (71/84). The efficacy was higher among children weighing less than the identified cut-off of 9.0 kg (89% in 0-9.0 kg versus 62% in 9.01-15.0 kg, p = 0.026). Among children diagnosed with HD, 96% (26/27) weighed 0-9.0 kg. In this weight group, the diagnostic efficacy was lower in aganglionosis compared to ganglionosis (77%; 20/26 versus 96%; 43/45), p = 0.045).

CONCLUSIONS

The RSB diagnostic efficacy was significantly higher in children weighing less than 9.0 kg and was less in aganglionic compared to ganglionic tissue. Therefore, weight can be useful to predict RSB diagnostic efficacy.

Development, Diversity, and Neurogenic Capacity of Enteric Glia

Enteric glia are a fascinating population of cells. Initially identified in the gut wall as the "support" cells of the enteric nervous system, studies over the past 20 years have unveiled a vast array of functions carried out by enteric glia. They mediate enteric nervous system signalling and play a vital role in the local regulation of gut functions. Enteric glial cells interact with other gastrointestinal cell types such as those of the epithelium and immune system to preserve homeostasis, and are perceptive to luminal content. Their functional versatility and phenotypic heterogeneity are mirrored by an extensive level of plasticity, illustrated by their reactivity in conditions associated with enteric nervous system dysfunction and disease. As one of the hallmarks of their plasticity and extending their operative relationship with enteric neurons, enteric glia also display neurogenic potential. In this review, we focus on the development of enteric glial cells, and the mechanisms behind their heterogeneity in the adult gut. In addition, we discuss what is currently known about the role of enteric glia as neural precursors in the enteric nervous system.

Clinical significance and biological effect of ZFAS1 in Hirschsprung's disease and preliminary exploration of its underlying mechanisms using integrated bioinformatics analysis

BACKGROUND

The pathogenesis of Hirschprung's disease (HSCR) remains largely unknown. The lncRNA ZNFX1 antisense RNA 1 (ZFAS1) has been found to have vital regulatory roles in a number of diseases. However, the association between ZFAS1 and HSCR has not been reported.

AIMS

The present study was aimed at investigating the expression pattern and biological function and underlying mechanisms of ZFAS1 in HSCR.

METHODS

The expression of ZFAS1 was detected in surgical excision samples of 30 children diagnosed with HSCR and 30 control cases. Functional experiments were conducted after over-expression or knockdown of ZFAS1 in human neuronal cell line SH-SY-5Y. Multiple bioinformatics databases and tools were used to explore the potential regulatory mechanisms of ZFAS1 in HSCR.

RESULTS

Compared with the control group, the HSCR group has a significantly higher level of ZFAS1(P = 0.0012). The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was 0.7133 (P = 0.0045), which indicated good biomarker potency of ZFAS1 in HSCR. Functionally, over-expression of ZFAS1 significantly inhibited cell proliferation, whereas knockdown of ZFAS1 promoted cell proliferation and colony formation of SH-SY-5Y cells. Using multiple databases, a competing endogenous RNA (ceRNA) network, containing ZFAS1,13 candidate miRNAs, and 110 potential gene targets, was established. Further enrichment analysis suggested that ZFAS1 may regulate a number of genes and signaling pathways that were crucial for neuron development.

CONCLUSIONS

Our findings revealed that ZFAS1 may participate in the pathogenesis of HSCR through regulating neuron functions. Bioinformatics analysis highlighted an important perspective for the following mechanical researches.

Direct Interaction of Sox10 With Cadherin-19 Mediates Early Sacral Neural Crest Cell Migration: Implications for Enteric Nervous System Development Defects

BACKGROUND AND AIMS

The enteric nervous system, which regulates many gastrointestinal functions, is derived from neural crest cells (NCCs). Defective NCC migration during embryonic development may lead to enteric neuropathies such as Hirschsprung's disease (hindgut aganglionosis). Sox10 is known to be essential for cell migration but downstream molecular events regulating early NCC migration have not been fully elucidated. This study aimed to determine how Sox10 regulates migration of sacral NCCs toward the hindgut using Dominant megacolon mice, an animal model of Hirschsprung's disease with a Sox10 mutation.

METHODS

We used the following: time-lapse live cell imaging to determine the migration defects of mutant sacral NCCs; genome-wide microarrays, site-directed mutagenesis, and whole embryo culture to identify Sox10 targets; and liquid chromatography and tandem mass spectrometry to ascertain downstream effectors of Sox10.

RESULTS

Sacral NCCs exhibited retarded migration to the distal hindgut in Sox10-null embryos with simultaneous down-regulated expression of cadherin-19 (Cdh19). Sox10 was found to bind directly to the Cdh19 promoter. Cdh19 knockdown resulted in retarded sacral NCC migration in vitro and ex vivo, whereas re-expression of Cdh19 partially rescued the retarded migration of mutant sacral NCCs in vitro. Cdh19 formed cadherin-catenin complexes, which then bound to filamentous actin of the cytoskeleton during cell migration.

CONCLUSIONS

Cdh19 is a direct target of Sox10 during early sacral NCC migration toward the hindgut and forms cadherin-catenin complexes which interact with the cytoskeleton in migrating cells. Elucidation of this novel molecular pathway helps to provide insights into the pathogenesis of enteric nervous system developmental defects.

Enteric nervous system and inflammatory bowel diseases: Correlated impacts and therapeutic approaches through the P2X7 receptor

The enteric nervous system (ENS) consists of thousands of small ganglia arranged in the submucosal and myenteric plexuses, which can be negatively affected by Crohn's disease and ulcerative colitis - inflammatory bowel diseases (IBDs). IBDs are complex and multifactorial disorders characterized by chronic and recurrent inflammation of the intestine, and the symptoms of IBDs may include abdominal pain, diarrhea, rectal bleeding, and weight loss. The P2X7 receptor has become a promising therapeutic target for IBDs, especially owing to its wide expression and, in the case of other purinergic receptors, in both human and model animal enteric cells. However, little is known about the actual involvement between the activation of the P2X7 receptor and the cascade of subsequent events and how all these activities associated with chemical signals interfere with the functionality of the affected or treated intestine. In this review, an integrated view is provided, correlating the structural organization of the ENS and the effects of IBDs, focusing on cellular constituents and how therapeutic approaches through the P2X7 receptor can assist in both protection from damage and tissue preservation.

miR-938 rs2505901 T>C polymorphism increases Hirschsprung disease risk: a case-control study of Chinese children

Aim: To explore the association between miR-938 rs2505901 T>C polymorphism and Hirschsprung disease (HSCR) risk in Chinese children. Materials & Methods: We conducted a case-control study in a Chinese population with 1381 cases and 1457 controls. The associated correlation strengths were assessed by adjusted odds ratios (AORs) and 95% CIs. Results: The results revealed that the rs2505901 TC and rs2505901 TC/CC genotype were related to an increased HSCR risk compared to the risk contributed by the rs2505901 TT genotype. A stratification analysis showed that the rs2505901 TC/CC genotype promoted the progression of HSCR more significantly in patients with the short-segment HSCR subtype. Conclusion: Our study indicated that miR-938 rs2505901 T>C polymorphism is significantly associated with HSCR risk in Chinese children. This result needs to be confirmed with well-designed studies.

Ciliary protein Kif7 regulates Gli and Ezh2 for initiating the neuronal differentiation of enteric neural crest cells during development

Gastrointestinal motility disorders occur frequently in patients with ciliopathy, but the underlying genetic link is unclear. The ciliary protein Kif7 can positively or negatively regulate Hedgehog signaling in different cellular contexts. Mice with neural crest cell (NCC)–specific Kif7 deficiency show a marked reduction of enteric NOS⁺ inhibitory neurons. Malformation of enteric nervous system (ENS) causes growth retardation and gut motility defect in mice. Mechanistically, Kif7 inhibits Gli2 in enteric NCCs (ENCCs), where Gli2 positively regulates the expression of Ezh2 by inhibiting the miR124-mediated suppression. In developing ENCCs, Ezh2 is a master regulator of 102 core genes underlying ENCC differentiation. Deletion of Gli2 or inhibition of Ezh2 favors the neurogenic lineage differentiation of mouse and human ENCCs and rescues the ENS defects of Kif7 mutants. In summary, Hedgehog signal, via Kif7-Gli-Ezh2, controls the timely expressions of the core genes to mediate the differentiation of ENCCs.

Benzophenone-3 induced abnormal development of enteric nervous system in zebrafish through MAPK/ERK signaling pathway

Hirschsprung disease (HSCR) is a congenital disease characterized by the absence of enteric neurons, which is derived from the failure of the proliferation, differentiation or migration of the enteric neural crest cells (ENCCs). HSCR is associated with multiple risk factors, including polygenic inheritance factors and environmental factors. Genetic studies have been extensively performed, whereas studies related to environmental factors remain insufficient. Benzophenone-3 (BP-3), one important component of the ultraviolet (UV) filters, has been proved to have cytotoxicity and neurotoxicity which might be associated with HSCR. In this study, we used zebrafish as a model to investigate the relationship between BP-3 exposure and the development of the enteric nervous system (ENS) in vivo. Embryos exposed to BP-3 showed an average of 46% reduction of the number of the enteric neurons number. Besides, the ENCCs specific markers (ret and hand2) were downregulated upon BP-3 exposure. Moreover, we identified potential targets of BP-3 through Network Pharmacology Analysis and Autodock and demonstrated that the attenuation of the MAPK/ERK signaling might be the potential mechanism underlying the inhibition of the ENS development by BP-3. Importantly, MAPK/ERK signaling agonist could be used to rescue the ENS defects of zebrafish induced by BP-3. Overall, we characterized the influence of BP-3 on ENS development in vivo and explored possible molecular mechanisms.

Roles of Enteric Neural Stem Cell Niche and Enteric Nervous System Development in Hirschsprung Disease

The development of the enteric nervous system (ENS) is highly modulated by the synchronized interaction between the enteric neural crest cells (ENCCs) and the neural stem cell niche comprising the gut microenvironment. Genetic defects dysregulating the cellular behaviour(s) of the ENCCs result in incomplete innervation and hence ENS dysfunction. Hirschsprung disease (HSCR) is a rare complex neurocristopathy in which the enteric neural crest-derived cells fail to colonize the distal colon. In addition to ENS defects, increasing evidence suggests that HSCR patients may have intrinsic defects in the niche impairing the extracellular matrix (ECM)-cell interaction and/or dysregulating the cellular niche factors necessary for controlling stem cell behaviour. The niche defects in patients may compromise the regenerative capacity of the stem cell-based therapy and advocate for drug- and niche-based therapies as complementary therapeutic strategies to alleviate/enhance niche-cell interaction. Here, we provide a summary of the current understandings of the role of the enteric neural stem cell niche in modulating the development of the ENS and in the pathogenesis of HSCR. Deciphering the contribution of the niche to HSCR may provide important implications to the development of regenerative medicine for HSCR.