Developmental determinants of the independence and complexity of the enteric nervous system

The interplay between microbiota and brain-gut axis in epilepsy treatment

The brain-gut axis plays a vital role in connecting the cognitive and emotional centers of the brain with the intricate workings of the intestines. An imbalance in the microbiota-mediated brain-gut axis extends far beyond conditions like Irritable Bowel Syndrome (IBS) and obesity, playing a critical role in the development and progression of various neurological disorders, including epilepsy, depression, Alzheimer's disease (AD), and Parkinson's disease (PD). Epilepsy, a brain disorder characterized by unprovoked seizures, affects approximately 50 million people worldwide. Accumulating evidence suggests that rebuilding the gut microbiota through interventions such as fecal microbiota transplantation, probiotics, and ketogenic diets (KD) can benefit drug-resistant epilepsy. The disturbances in the gut microbiota could contribute to the toxic side effects of antiepileptic drugs and the development of drug resistance in epilepsy patients. These findings imply the potential impact of the gut microbiota on epilepsy and suggest that interventions targeting the microbiota, such as the KD, hold promise for managing and treating epilepsy. However, the full extent of the importance of microbiota in epilepsy treatment is not yet fully understood, and many aspects of this field remain unclear. Therefore, this article aims to provide an overview of the clinical and animal evidence supporting the regulatory role of gut microbiota in epilepsy, and of potential pathways within the brain-gut axis that may be influenced by the gut microbiota in epilepsy. Furthermore, we will discuss the recent advancements in epilepsy treatment, including the KD, fecal microbiota transplantation, and antiseizure drugs, all from the perspective of the gut microbiota.

Understanding food allergy through neuroimmune interactions in the gastrointestinal tract

Food allergies are adverse immune reactions to food proteins in the absence of oral tolerance, and the incidence of allergies to food, including peanut, cow's milk, and shellfish, has been increasing globally. Although advancements have been made toward understanding the contributions of the type 2 immune response to allergic sensitization, crosstalk between these immune cells and neurons of the enteric nervous system is an area of emerging interest in the pathophysiology of food allergy, given the close proximity of neuronal cells of the enteric nervous system and type 2 effector cells, including eosinophils and mast cells. At mucosal sites, such as the gastrointestinal tract, neuroimmune interactions contribute to the sensing and response to danger signals from the epithelial barrier. This communication is bidirectional, as immune cells express receptors for neuropeptides and transmitters, and neurons express cytokine receptors, allowing for the detection of and response to inflammatory insults. In addition, it seems that neuromodulation of immune cells including mast cells, eosinophils, and innate lymphoid cells is critical for amplification of the type 2 allergic immune response. As such, neuroimmune interactions may be critical targets for future food allergy therapies. This review evaluates the contributions of local enteric neuroimmune interactions to the underlying immune response in food allergy and discusses considerations for future investigations into targeting neuroimmune pathways for treatment of food allergies.

Impact of the mother's gut microbiota on infant microbiome and brain development

The link between the gut microbiome and health has recently garnered considerable interest in its employment for medicinal purposes. Since the early microbiota exhibits more flexibility compared to that of adults, there is a considerable possibility that altering it will have significant consequences on human development. Like genetics, the human microbiota can be passed from mother to child. This provides information on early microbiota acquisition, future development, and prospective chances for intervention. The succession and acquisition of early-life microbiota, modifications of the maternal microbiota during pregnancy, delivery, and infancy, and new efforts to understand maternal-infant microbiota transmission are discussed in this article. We also examine the shaping of mother-to-infant microbial transmission, and we then explore possible paths for future research to advance our knowledge in this area.

A functional network of highly pure enteric neurons in a dish

The enteric nervous system (ENS) is the intrinsic nervous system that innervates the entire digestive tract and regulates major digestive functions. Recent evidence has shown that functions of the ENS critically rely on enteric neuronal connectivity; however, experimental models to decipher the underlying mechanisms are limited. Compared to the central nervous system, for which pure neuronal cultures have been developed for decades and are recognized as a reference in the field of neuroscience, an equivalent model for enteric neurons is lacking. In this study, we developed a novel model of highly pure rat embryonic enteric neurons with dense and functional synaptic networks. The methodology is simple and relatively fast. We characterized enteric neurons using immunohistochemical, morphological, and electrophysiological approaches. In particular, we demonstrated the applicability of this culture model to multi-electrode array technology as a new approach for monitoring enteric neuronal network activity. This in vitro model of highly pure enteric neurons represents a valuable new tool for better understanding the mechanisms involved in the establishment and maintenance of enteric neuron synaptic connectivity and functional networks.

A Deeper Curse: A Hirschsprung Patient's Evaluation Unmasks a Rare Association with Congenital Central Hypoventilation Syndrome and Neuroblastoma

We present a rare case of a 2-year-old male patient referred for primary evaluation of constipation and ultimately treatment of Hirschsprung disease (HSCR) whose preoperative workup incidentally revealed a posterior paraspinal mass. Following the biopsy of the mass, the patient exhibited hypoventilation and hypoxia requiring a delayed extubation, raising suspicion for congenital central hypoventilation syndrome (CCHS). We focus on the known history of associations between HSCR and CCHS, in addition to recently found genetic mutations in paired-like homeobox 2B that link HSCR, CCHS, and neuroblastoma.

Effect of Reactive EGCs on Intestinal Motility and Enteric Neurons During Endotoxemia

Paralytic ileus is common in patients with septic shock, causing high morbidity and mortality. Enteric neurons and enteric glial cells (EGCs) regulate intestinal motility. However, little is known about their interaction in endotoxemia. This study aimed to investigate whether reactive EGCs had harmful effects on enteric neurons and participated in intestinal motility disorder in mice during endotoxemia. Endotoxemia was induced by the intraperitoneal injection of lipopolysaccharide (LPS) in mice. Fluorocitrate (FC) was administered before LPS injection to inhibit the reactive EGCs. The effects of reactive EGCs on intestinal motility were analyzed by motility assays in vivo and colonic migrating motor complexes ex vivo. The number of enteric neurons was evaluated by immunofluorescent staining of HuCD, nNOS, and ChAT in vivo. In addition, we stimulated EGCs with IL-1β and TNF-α in vitro and cultured the primary enteric neurons in the conditioned medium, detecting the apoptosis and morphology of neurons through staining TUNEL, cleaved caspase-3 protein, and anti-β-III tubulin. Intestinal motility and peristaltic reflex were improved by inhibiting reactive EGCs in vivo. The density of the neuronal population in the colonic myenteric plexus increased significantly, while the reactive EGCs were inhibited, especially the nitrergic neurons. In vitro, the enteric neurons cultured in the conditioned medium of reactive EGCs had a considerably higher apoptotic rate, less dendritic complexity, and fewer primary neurites. Reactive enteric glial cells probably participated in paralytic ileus by damaging enteric neurons during endotoxemia. They might provide a novel therapeutic strategy for intestinal motility disorders during endotoxemia or sepsis.

Systematic screen of potential circular RNA biomarkers of Hirschsprung's disease

BACKGROUND

Hirschsprung's disease (HSCR) is a developmental disorder of the enteric nervous system in which enteric ganglia are missing along a portion of the intestine. Aberrant expression of several circular RNAs (circRNAs) has been identified in the disease, but the full range of dysregulated circRNAs and their potential roles in its pathogenesis remain unclear. We used microarray profiling to systematically screen for circRNAs that were differentially expressed in HSCR, and we comprehensively analyzed the potential circRNA-miRNA-mRNA regulatory network to identify molecular mechanisms involved in the disorder.

METHODS

We identified circRNAs that were differentially expressed between diseased tissue and paired normal intestinal tissues from patients with HSCR. The most strongly upregulated circRNAs were then validated by quantitative reverse-transcription-PCR (RT-PCR). We also constructed a circRNA-miRNA-mRNA interaction network to determine functional interactions between miRNAs and mRNAs.

RESULTS

We identified 17 circRNAs that were upregulated and 10 that were downregulated in HSCR tissue compared with normal tissues. The five circRNAs that showed the greatest upregulation were verified by RT-PCR: hsa_circRNA_092493, hsa_circRNA_101965, hsa_circRNA_103118, hsa_circRNA_103279, and hsa_circRNA_104214. These five circRNAs were successfully adopted to diagnose HSCR based on receiver operating characteristic curves, and they were used to generate a circRNA-miRNA-mRNA network. The network revealed a potential function of the circRNAs as molecular sponges targeting miRNAs and mRNAs in HSCR.

CONCLUSIONS

This first-ever systematic dissection of the circRNA profile in HSCR may provide useful insights into improving diagnosis and therapy.

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.

Loss function of Bcr mutation causes gastrointestinal dysmotility and brain developmental defects

BACKGROUND

The breakpoint cluster region (BCR) is a protein that originally forms a fusion protein with c-Abl tyrosine kinase and induces leukemia. Researchers have shown that BCR is enriched in the central nervous system and may contribute to neurological disorders. We aimed to investigate the physiological function of BCR in neural development in the gastrointestinal (GI) tract and brain.

METHODS

Whole-exome sequencing was used to screen for mutations in the BCR. Bcr knockout mice (Bcr^-/- , ΔExon 2-22) were generated using the CRISPR/Cas9 system. Transit of carmine red dye and glass bead expulsion assays were used to record total and proximal GI transit and distal colonic transit.

KEY RESULTS

In an infant with pediatric intestinal pseudo-obstruction, we found a heterozygous de novo mutation (NM_004327.3:c.3072+1G>A) in BCR. Bcr deficiency mice (Bcr^-/- ) exhibited growth retardation and impaired gastrointestinal motility. Bcr^-/- mice had a prolonged average total GI transit time with increased distal colonic transit and proximal GI transit in isolation. Morphology analysis indicated that Bcr^-/- mice had a less number of neurons in the submucosal plexus and myenteric plexus. Bcr^-/- mice exhibited apparent structural defects in the brain, particularly in the cortex. Additionally, Bcr^- depletion in the mouse cortex altered the expression of Ras homologous (Rho) family small GTPases.

CONCLUSIONS AND INFERENCES

BCR mutations are associated with intestinal obstruction in children. Loss of Bcr can cause intestinal dysmotility and brain developmental defects may via regulation of Rho GTPases.

[Definition and treatment of superior mesenteric artery revascularization and dissection-associated diarrhea (SMARD syndrome) in Germany]

Hintergrund

Die A. mesenterica superior (AMS) wird im Rahmen von Pankreasresektionen (PR) und mesenterialen Gefäßeingriffen (MG) freigelegt und disseziert. Eine dadurch entstandene Schädigung des umliegenden ex- und intrinsischen vegetativen Nervenplexus kann zu einer passageren oder therapierefraktären Diarrhö führen.

Fragestellung

Die vorliegende Studie soll einen Überblick über den derzeitigen Stellenwert der AMS-Revaskularisations- und -Dissektions-assoziierten Diarrhö („superior mesenteric artery revascularisation and dissection-associated diarrhea“[SMARD]-Syndrom) in Deutschland geben.

Material und Methoden

Nach selektiver Literaturrecherche (SLR) mit der Fragestellung, ob und wie häufig eine postoperativ neu aufgetretene Diarrhö nach PR und MG vorkommt, wurde eine Onlineumfrage versendet.

Ergebnisse

Die SLR (n = 4) bestätigte, dass eine postoperativ neu aufgetretene Diarrhö eine häufige Komplikation nach Präparation zur Revaskularisation (RV) bzw. Dissektion (DIS) der AMS ist (Inzidenz ca. 62 %). Therapierefraktäre Verläufe sind selten 14 %. 54 von 159 Zentren beteiligten sich an der Umfrage. 63 % gaben an, eine AMS-RV/-DIS im Rahmen von PR oder MG durchzuführen. Der Durchschnitt an PR pro Zentrum lag 2018 bei 47 und bei 49 im Jahr 2019. Fünf MG erfolgten durchschnittlich in beiden Jahren pro Zentrum. Drei Patienten litten durchschnittlich am SMARD-Syndrom.

Diskussion

Diese Umfrage erfasst erstmals den derzeitigen Stellenwert des SMARD-Syndroms in Deutschland. Bisher fehlen Empfehlungen zur Therapie einer solchen Diarrhö. Die Ergebnisse zeigen, dass zunächst eine symptomatische Therapie erfolgen sollte. Aufgrund der Komplexität der Pathophysiologie sind kausale Therapieansätze bislang nicht entwickelt.

The enteric nervous system in gastrointestinal disease etiology

A highly conserved but convoluted network of neurons and glial cells, the enteric nervous system (ENS), is positioned along the wall of the gut to coordinate digestive processes and gastrointestinal homeostasis. Because ENS components are in charge of the autonomous regulation of gut function, it is inevitable that their dysfunction is central to the pathophysiology and symptom generation of gastrointestinal disease. While for neurodevelopmental disorders such as Hirschsprung, ENS pathogenesis appears to be clear-cut, the role for impaired ENS activity in the etiology of other gastrointestinal disorders is less established and is often deemed secondary to other insults like intestinal inflammation. However, mounting experimental evidence in recent years indicates that gastrointestinal homeostasis hinges on multifaceted connections between the ENS, and other cellular networks such as the intestinal epithelium, the immune system, and the intestinal microbiome. Derangement of these interactions could underlie gastrointestinal disease onset and elicit variable degrees of abnormal gut function, pinpointing, perhaps unexpectedly, the ENS as a diligent participant in idiopathic but also in inflammatory and cancerous diseases of the gut. In this review, we discuss the latest evidence on the role of the ENS in the pathogenesis of enteric neuropathies, disorders of gut-brain interaction, inflammatory bowel diseases, and colorectal cancer.

Peptide Derived from AHNAK Inhibits Cell Migration and Proliferation in Hirschsprung's Disease by Targeting the ERK1/2 Pathway

Hirschsprung's disease (HSCR) is characterized by the lack of ganglion cells in the distal part of the digestive tract. It occurs due to migration disorders of enteric neural crest cells (ENCCs) from 5 to 12 weeks of embryonic development. More and more studies show that HSCR is a result of the interaction of multiple genes and the microenvironments, but its specific pathogenesis has not been fully elucidated. Studies have confirmed that many substances in the intestinal microenvironment, such as laminin and β1-integrin, play a vital regulatory role in cell growth and disease progression. In addition to these high-molecular-weight proteins, research on endogenous polypeptides derived from these proteins has been increasing in recent years. However, it is unclear whether these endogenous peptides have effects on the migration of ENCCs and thus participate in the occurrence of HSCR. Previously, our research group found that compared with the normal intestinal tissue, the expression of AHNAK protein in the stenosed intestinal tissue of HSCR patients was significantly upregulated, and overexpression of AHNAK could inhibit cell migration and proliferation. In this study, endogenous peptides were extracted from the normal control intestinal tissue and the stenosed HSCR intestinal tissue. The endogenous polypeptide expression profile was analyzed by liquid chromatography-mass spectrometry, and multiple peptides derived from AHNAK protein were found. We selected one of them, "EGPEVDVNLPK", for research. Because there is no uniform naming system, this peptide is temporarily named PDAHNAK (peptide derived from AHNAK). This project aims to clarify the potential role of PDAHNAK in the development of HSCR and to further understand its relationship with its precursor protein AHNAK and how they contribute to the development of HSCR.

Genetic background-dependent abnormalities of the enteric nervous system and intestinal function in Kif26a-deficient mice

The Kif26a protein-coding gene has been identified as a negative regulator of the GDNF-Ret signaling pathway in enteric neurons. The aim of this study was to investigate the influence of genetic background on the phenotype of Kif26a-deficient (KO, -/-) mice. KO mice with both C57BL/6 and BALB/c genetic backgrounds were established. Survival rates and megacolon development were compared between these two strains of KO mice. Functional bowel assessments and enteric neuron histopathology were performed in the deficient mice. KO mice with the BALB/c genetic background survived more than 400 days without evidence of megacolon, while all C57BL/6 KO mice developed megacolon and died within 30 days. Local enteric neuron hyperplasia in the colon and functional bowel abnormalities were observed in BALB/c KO mice. These results indicated that megacolon and enteric neuron hyperplasia in KO mice are influenced by the genetic background. BALB/c KO mice may represent a viable model for functional gastrointestinal diseases such as chronic constipation, facilitating studies on the underlying mechanisms and providing a foundation for the development of treatments.

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

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

Semaphorin 3A controls enteric neuron connectivity and is inversely associated with synapsin 1 expression in Hirschsprung disease

Most of the gut functions are controlled by the enteric nervous system (ENS), a complex network of enteric neurons located throughout the wall of the gastrointestinal tract. The formation of ENS connectivity during the perinatal period critically underlies the establishment of gastrointestinal motility, but the factors involved in this maturation process remain poorly characterized. Here, we examined the role of Semaphorin 3A (Sema3A) on ENS maturation and its potential implication in Hirschsprung disease (HSCR), a developmental disorder of the ENS with impaired colonic motility. We found that Sema3A and its receptor Neuropilin 1 (NRP1) are expressed in the rat gut during the early postnatal period. At the cellular level, NRP1 is expressed by enteric neurons, where it is particularly enriched at growth areas of developing axons. Treatment of primary ENS cultures and gut explants with Sema3A restricts axon elongation and synapse formation. Comparison of the ganglionic colon of HSCR patients to the colon of patients with anorectal malformation shows reduced expression of the synaptic molecule synapsin 1 in HSCR, which is inversely correlated with Sema3A expression. Our study identifies Sema3A as a critical regulator of ENS connectivity and provides a link between altered ENS connectivity and HSCR.

Intestinal Macrophages in Resolving Inflammation

Macrophages not only regulate intestinal homeostasis by recognizing pathogens to control enteric infections but also employ negative feedback mechanisms to prevent chronic inflammation. Hence, macrophages are intriguing targets for immune-mediated therapies, especially when barrier function in the gut is compromised to trigger aberrant inflammatory responses, most notably during inflammatory bowel diseases. Recently, there has been considerable progress in our understanding of human macrophage biology in different tissues, including the intestines. In this review, we discuss some new findings on the properties of distinct populations of intestinal macrophages, how resolution of inflammation and tissue repair by macrophages could be promoted by type 2 cytokines as well as other therapeutic interventions, and highlight some challenges for translating these findings into the future for this exciting area of immunology research.

Assessment of Behavioural Disorders in Children with Functional Constipation

BACKGROUND

Functional constipation (FC) is a common health problem in paediatrics that causes significant physical and emotional distress to patients and their families.

AIM

In the current work, we assessed the presence of behavioural problems in children with functional constipation and their pattern and relation to various demographic and disease-associated factors.

METHODS

A cross-sectional case-control study was conducted, including 55 consecutive children aged 4-16 years diagnosed with functional constipation and 55 healthy age and sex-matched controls. Psychological assessment was done using the Pediatric Symptom Checklist - 17 (PSC-17).

RESULTS

Twenty-six (47.3%) patients with FC had positive total PSC-17 scores while none of the controls had positive scores (p-value < 0.001). Positive internalising and externalising behaviours scores and attention problems were found in 36 (65.5%), 15 (27.3%) and 12 (21.8%) of the patients respectively in contrary to controls where only 6 (10.9%) had positive scores in internalising behaviour, and non-showed externalising behaviour and 4 (7.3%) were inattentive. Older age, longer duration of illness, residency in rural areas and presence of encopresis were found to have a significant association with the presence of such problems.

CONCLUSION

Children with FC have more behavioural disorders compared to healthy controls. Integration of psychosocial aspects and their management is recommended during dealing with patients with FC.

Hirschsprung disease: Insights on genes, penetrance, and prenatal diagnosis

The objective of this mini-review is to provide insights on the advances in the understanding of the genetic variants associated with different manifestations of Hirschsprung disease, which may present with a range of denervation from a short segment of colon to total colonic and small bowel or extensive aganglionosis. A recent article in this journal documented potential gene variants involved in long-segment Hirschsprung disease in 23 patients. Gene variants were identified using a 31-gene panel of genes related to Hirschsprung disease or enteric neural crest cell development, as previously reported in the literature. The study identified potentially harmful variants in eight genes across 13 patients, with a detection rate of 56.5% (13/23 patients). Five patients had pathologic variants in RET, NRG1, and L1CAM, and the remainder were considered variants of unknown significance. The authors attempted prenatal diagnosis of Hirschsprung disease utilizing an amniocentesis sample obtained for advanced maternal age in a family with a known deleterious RET mutation, manifested in the father (long-segment Hirschsprung disease) and older daughter (total colonic aganglionosis). The fetus had the same RET variant but, after several years of follow-up, has not developed any symptoms of Hirschsprung disease, supporting the conclusion that this RET mutation is an autosomal dominant gene with incomplete penetrance. This experience suggests that genetic counseling is appropriate to carefully assess the justification of prenatal testing, especially, when the phenotype of long-segment Hirschsprung disease is so variable and the disease is potentially curable with surgery.

Chronic Megacolon Presenting in Adolescents or Adults: Clinical Manifestations, Diagnosis, and Genetic Associations

OBJECTIVE

Chronic megacolon is rarely encountered in clinical practice beyond infancy or early childhood. Most cases are sporadic, and some are familial megacolon and present during adolescence or adulthood. There is a need for diagnostic criteria and identifying genetic variants reported in non-Hirschsprung's megacolon.

METHODS

PubMed search was conducted using specific key words.

RESULTS

This article reviews the clinical manifestations, current diagnostic criteria, and intraluminal measurements of colonic compliance to confirm the diagnosis when the radiological imaging is not conclusive. Normal ranges of colonic compliance at 20, 30, and 44 mmHg distension are provided. The diverse genetic associations with chronic acquired megacolon beyond childhood are reviewed, including the potential association of SEMA3F gene in a family with megacolon.

CONCLUSIONS

Measuring colonic compliance could be standardized and simplified by measuring volume at 20, 30, and 44 mmHg distension to identify megacolon when radiology is inconclusive. Diverse genetic associations with chronic acquired megacolon beyond childhood have been identified.

The Role of the Gut-Brain Axis in Attention-Deficit/Hyperactivity Disorder

Genetic and environmental factors play a role in the cause and development of attention-deficit/hyperactivity disorder (ADHD). Recent studies have suggested an important role of the gut-brain axis (GBA) and intestinal microbiota in modulating the risk of ADHD. Here, the authors provide a brief overview of the clinical and biological picture of ADHD and how the GBA could be involved in its cause. They discuss key biological mechanisms involved in the GBA and how these may increase the risk of developing ADHD. Understanding these mechanisms may help to characterize novel treatment options via identification of disease biomarkers.

Local heat-shock mediated multi-color labeling visualizing behaviors of enteric neural crest cells associated with division and neurogenesis in zebrafish gut

BACKGROUND

The enteric nervous system (ENS) is derived from enteric neural crest cells (ENCCs) that migrate into the gut. The zebrafish larva is a good model to study ENCC development due to its simplicity and transparency. However, little is known how individual ENCCs divide and become neurons.

RESULTS

Here, by applying our new method of local heat-shock mediated Cre-recombination around the dorsal vagal area of zebrafish embryos we produced multicolored clones of ENCCs, and performed in vivo time-lapse imaging from ca. 3.5 to 4 days post-fertilization after arrival of ENCCs in the gut. Individual ENCCs migrated in various directions and were highly intermingled. The cell divisions were not restricted to a specific position in the gut. Antibody staining after imaging with anti-HuC/D and anti-Sox10 showed that an ENCC produced two neurons, or formed a neuron and an additional ENCC that further divided. At division, the daughter cells immediately separated. Afterward, some made soma-soma contact with other ENCCs.

CONCLUSIONS

We introduced a new method of visualizing individual ENCCs in the zebrafish gut, describing their behaviors associated with cell division, providing a foundation to study the mechanism of proliferation and neurogenesis in the ENS in vertebrates.

Familial chronic megacolon presenting in childhood or adulthood: Seeking the presumed gene association

OBJECTIVE

We identified a pedigree over five generations with 49 members, some of whom had chronic megacolon presenting in adolescence or adulthood. We aimed to assess the genetic cause of chronic megacolon through clinical and DNA studies.

DESIGN

After ethical approval and informed consent, family members provided answers to standard bowel disease questionnaires, radiological or surgical records, and DNA (buccal mucosal scraping). Exome DNA sequencing of colon tissue or blood DNA from seven family members with colon or duodenal dilatation, or no megacolon (n = 1) was carried out. Sanger sequencing was performed in 22 additional family members to further evaluate candidate variants. The study focused on genes of potential relevance to enteric nerve (ENS) maturation and Hirschsprung's disease or megacolon, based on the literature (GFRA1, NKX2-1, KIF26A, TPM3, ACTG2, SCN10A, and C17orf107 [CHRNE]) and other genetic variants that co-segregated with megacolon in the six affected family members.

RESULTS

Information was available in all except five members alive at time of study; among 30 members who provided DNA, six had definite megacolon, one megaduodenum, seven significant constipation without bowel dilatation, and 16 normal bowel function by questionnaire. Among genes studied, SEMA3F (g.3:50225360A>G; c1873A>G) was found in 6/6 family members with megacolon. The SEMA3F gene variant was assessed as potentially pathogenic, based on M-CAP in silico prediction. SEMA3F function is associated with genes (KIT and PDGFRB) that impact intestinal pacemaker function.

CONCLUSION

Familial chronic megacolon appears to be associated with SEMA3F, which is associated with genes impacting enteric nerve or pacemaker function.

Establishment of an induced pluripotent stem cell model of Hirschsrpung disease, a congenital condition of the enteric nervous system, from a patient carrying a novel RET mutation

Hirschsprung disease (HSCR) is a complex genetic disorder of the enteric nervous system that is characterized by a complete loss of the neuronal ganglion cells in the intestinal tract. It is one of the most frequent causes of congenital intestinal obstruction and more than 80% of the causative mutations are in RET. Here, we identified a new RET mutation in a patient and established a cell model that can be used to elucidate the pathogenesis of HSCR. Peripheral blood was collected from a patient who was clinically and pathologically diagnosed with HSCR with a heterozygous deletion mutation (c.180delT; p.Glu61ArgfsX163) in exon 2 of RET. Patient-derived induced pluripotent stem cell (iPSC) lines were generated from dermal fibroblasts. Using immunofluorescence staining and RT-PCR, we showed that the generated iPSCs expressed the pluripotency markers OCT4, SSEA4, SOX2, TRA-1-60, and NANOG. We also showed that the HSCR-iPSCs could differentiate into cells from all three germ layers by spontaneous in-vitro differentiation. In addition, 3 months after the administration of a subcutaneous injection of these iPSCs into nude mice, teratomas with all three germ layers were observed. We identified a new RET gene mutation causing HSCR and successfully established a human iPSC line from an HSCR patient carrying this novel RET mutation, which could be useful in pathogenesis studies of HSCR.

Regional complexity in enteric neuron wiring reflects diversity of motility patterns in the mouse large intestine

The enteric nervous system controls a variety of gastrointestinal functions including intestinal motility. The minimal neuronal circuit necessary to direct peristalsis is well-characterized but several intestinal regions display also other motility patterns for which the underlying circuits and connectivity schemes that coordinate the transition between those patterns are poorly understood. We investigated whether in regions with a richer palette of motility patterns, the underlying nerve circuits reflect this complexity. Using Ca²⁺ imaging, we determined the location and response fingerprint of large populations of enteric neurons upon focal network stimulation. Complemented by neuronal tracing and volumetric reconstructions of synaptic contacts, this shows that the multifunctional proximal colon requires specific additional circuit components as compared to the distal colon, where peristalsis is the predominant motility pattern. Our study reveals that motility control is hard-wired in the enteric neural networks and that circuit complexity matches the motor pattern portfolio of specific intestinal regions.

Altered enteric expression of the homeobox transcription factor Phox2b in patients with diverticular disease

Background

Diverticular disease, a major gastrointestinal disorder, is associated with modifications of the enteric nervous system, encompassing alterations of neurochemical coding and of the tyrosine receptor kinase Ret/GDNF pathway. However, molecular factors underlying these changes remain to be determined.

Objectives

We aimed to characterise the expression of Phox2b, an essential regulator of Ret and of neuronal subtype development, in the adult human enteric nervous system, and to evaluate its potential involvement in acute diverticulitis.

Methods

Site-specific gene expression of Phox2b in the adult colon was analysed by quantitative polymerase chain reaction. Colonic specimens of adult controls and patients with diverticulitis were subjected to quantitative polymerase chain reaction for Phox2b and dual-label immunochemistry for Phox2b and the neuronal markers RET and tyrosine hydroxylase or the glial marker S100β.

Results

The results indicate that Phox2b is physiologically expressed in myenteric neuronal and glial subpopulations in the adult enteric nervous system. Messenger RNA expression of Phox2b was increased in patients with diverticulitis and both neuronal, and glial protein expression of Phox2b were altered in these patients.

Conclusions

Alterations of Phox2b expression may contribute to the enteric neuropathy observed in diverticular disease. Future studies are required to characterise the functions of Phox2b in the adult enteric nervous system and to determine its potential as a therapeutic target in gastrointestinal disorders.

Brain-Gut Axis: Clinical Implications

This article provides an overarching view of what is currently known about the physiology of the brain-gut axis in both health and disease and how these concepts apply to irritable bowel syndrome, the most common functional gastrointestinal disorder in pediatrics.

Circular RNA CCDC66 targets DCX to regulate cell proliferation and migration by sponging miR-488-3p in Hirschsprung's disease

It has been suggested that circular RNAs play critical roles in natural growth and disease development. Nevertheless, whether the circular RNAs were related in Hirschsprung's disease (HSCR) remains unknown. Thus, we discovered the cir-CCDC66 was downregulated in HSCR compared with the normal gut tissues. The cir-CCDC66 reduction might inhibit cells' proliferation and migration in vitro. Then, we found that DCX transcript was putative cir-CCDC66 competing endogenous RNA. Furthermore, the function of cir-CCDC66 as a sponge for miR-488-3p to regulate DCX RNA expression was demonstrated by immunoprecipitation and luciferase reporter assays. In conclusion, this is the first report revealing that cir-CCDC66 modulates DCX expression through sponging miR-488-3p and thus participates in the onset of HSCR.

Neuroendocrine regulation of innate lymphoid cells

The activities of the immune system in repairing tissue injury and combating pathogens were long thought to be independent of the nervous system. However, a major regulatory role of immunomodulatory molecules released locally or systemically by the neuroendocrine system has recently emerged. A number of observations and discoveries support indeed the notion of the nervous system as an immunoregulatory system involved in immune responses. Innate lymphoid cells (ILCs), including natural killer (NK) cells and tissue-resident ILCs, form a family of effector cells present in organs and mucosal barriers. ILCs are involved in the maintenance of tissue integrity and homeostasis. They can also secrete effector cytokines rapidly, and this ability enables them to play early roles in the immune response. ILCs are activated by multiple pathways including epithelial and myeloid cell-derived cytokines. Their functions are also regulated by mediators produced by the nervous system. In particular, the peripheral nervous system, through neurotransmitters and neuropeptides, works in parallel with the hypothalamic-pituitary-adrenal and gonadal axis to modulate inflammatory events and maintain homeostasis. We summarize here recent findings concerning the regulation of ILC activities by neuroendocrine mediators in homeostatic and inflammatory conditions.

Enteric nervous system development: what could possibly go wrong?

The gastrointestinal tract contains its own set of intrinsic neuroglial circuits - the enteric nervous system (ENS) - which detects and responds to diverse signals from the environment. Here, we address recent advances in the understanding of ENS development, including how neural-crest-derived progenitors migrate into and colonize the bowel, the formation of ganglionated plexuses and the molecular mechanisms of enteric neuronal and glial diversification. Modern lineage tracing and transcription-profiling technologies have produced observations that simultaneously challenge and affirm long-held beliefs about ENS development. We review many genetic and environmental factors that can alter ENS development and exert long-lasting effects on gastrointestinal function, and discuss how developmental defects in the ENS might account for some of the large burden of digestive disease.

News from the endothelin-3/EDNRB signaling pathway: Role during enteric nervous system development and involvement in neural crest-associated disorders

The endothelin system is a vertebrate-specific innovation with important roles in regulating the cardiovascular system and renal and pulmonary processes, as well as the development of the vertebrate-specific neural crest cell population and its derivatives. This system is comprised of three structurally similar 21-amino acid peptides that bind and activate two G-protein coupled receptors. In 1994, knockouts of the Edn3 and Ednrb genes revealed their crucial function during development of the enteric nervous system and melanocytes, two neural-crest derivatives. Since then, human and mouse genetics, combined with cellular and developmental studies, have helped to unravel the role of this signaling pathway during development and adulthood. In this review, we will summarize the known functions of the EDN3/EDNRB pathway during neural crest development, with a specific focus on recent scientific advances, and the enteric nervous system in normal and pathological conditions.

Aberrant expression of LncRNA-MIR31HG regulates cell migration and proliferation by affecting miR-31 and miR-31* in Hirschsprung's disease

Hirschsprung's disease (HSCR) is a birth defect that causes a failure of the enteric nervous system to cover the distal gut during early embryonic development. Evidence shows that long non-coding RNAs (lncRNA) play important roles in HSCR. The MIR31 host gene (MIR31HG), also known as Loc554202, is a long non-coding RNA (lncRNA), which acts as the host gene of (microRNA) miR-31 and miR-31*. There have been no studies regarding its function in early developmental defects during pregnancy, and its downstream genetic receptors. We report that downregulation of MIR31HG inhibited migration and proliferation in 293T and SH-SY5Y cell lines, by suppressing miR-31 and miR-31*. Moreover, the downregulation of miR-31 and miR-31* enhanced inter-α-trypsin inhibitor heavy chain 5 (ITIH5) and the phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic gamma subunit (PIK3CG), respectively with reductions of cell migration and proliferation in 293T and SH-SY5Y cell lines. In addition, synergistic actions were observed between miR-31 and miR-31* in cell migration and proliferation. Our results demonstrated that the MIR31HG-miR-31/31*-ITIH5/PIK3CG pathway plays a role in the pathogenesis of HSCR.

Development of interstitial cells of Cajal in the human digestive tract as the result of reciprocal induction of mesenchymal and neural crest cells

Neural crest cells (NCC) can migrate into different parts of the body and express their strong inductive potential. In addition, they are multipotent and are able to differentiate into various cell types with diverse functions. In the primitive gut, NCC induce differentiation of muscular structures and interstitial cells of Cajal (ICC), and they themselves differentiate into the elements of the enteric nervous system (ENS), neurons and glial cells. ICC develop by way of mesenchymal cell differentiation in the outer parts of the primitive gut wall around the myenteric plexus (MP) ganglia, with the exception of colon, where they appear simultaneously also at the submucosal border of the circular muscular layer around the submucosal plexus (SMP) ganglia. However, in a complex process of reciprocal induction of NCC and local mesenchyma, c‐kit positive precursors are the first to differentiate, representing probably the common precursors of ICC and smooth muscle cells (SMC). C‐kit positive precursors could represent a key impact factor regarding the final differentiation of NCC into neurons and glial cells with neurons subsequently excreting stem cell factor (SCF) and other signalling molecules. Under the impact of SCF, a portion of c‐kit positive precursors lying immediately around the ganglia differentiate into ICC, while the rest differentiate into SMC.

Upregulation of MiR-369-3p suppresses cell migration and proliferation by targeting SOX4 in Hirschsprung's disease

BACKGROUND

Hirschsprung disease (HSCR) is a congenital digestive disease in the new born. miR-369-3p has been reported to be involved in many human diseases. However, the relationship between miR-369-3p and HSCR remains largely unknown.

METHODS

In this study, qRT-PCR was used to detect the relative expression of miR-369-3p in 60 HSCR bowel tissue samples and 47 matched controls. Bioinformatic analysis and dual-luciferase reporter assay were performed to evaluate the target for miR-369-3p. Cell Counting Kit-8 (CCK-8) assay, Transwell assay, wound healing assay and flow cytometry were employed to investigate the biological function of miR-369-3p in human SH-SY5Y and 293T cell lines.

RESULTS

We found that ganglion cell numbers were remarkably reduced while miR-369-3p was significantly upregulated in HSCR tissues compared to that in adjacent normal tissues (P<0.01). Dual-luciferase reporter assay showed that the 3'-UTR of SOX4 was a direct target to miR-369-3p. Moreover, an increased level of miR-369-3p was inversely correlated with decreased levels of SOX4 mRNA and protein (P<0.05, respectively). Dysregulation of miR-369-3p and SOX4 significantly suppressed cell proliferation and migration in SH-SY5Y and 293T cell lines in vitro (P<0.05, respectively).

CONCLUSION

Our study demonstrates that aberrant expression of miR-369-3p might play a crucial role in the development HSCR by regulating SOX4 expression, which may infer that it is an effective diagnostic target in the pathogenesis of HSCR, but investigation is still needed to explore the underlying mechanism.

Spontaneous calcium waves in the developing enteric nervous system

The enteric nervous system (ENS) is an extensive network of neurons in the gut wall that arises from neural crest-derived cells. Like other populations of neural crest cells, it is known that enteric neural crest-derived cells (ENCCs) influence the behaviour of each other and therefore must communicate. However, little is known about how ENCCs communicate with each other. In this study, we used Ca²⁺ imaging to examine communication between ENCCs in the embryonic gut, using mice where ENCCs express a genetically-encoded calcium indicator. Spontaneous propagating calcium waves were observed between neighbouring ENCCs, through both neuronal and non-neuronal ENCCs. Pharmacological experiments showed wave propagation was not mediated by gap junctions, but by purinergic signalling via P2 receptors. The expression of several P2X and P2Y receptors was confirmed using RT-PCR. Furthermore, inhibition of P2 receptors altered the morphology of the ENCC network, without affecting neuronal differentiation or ENCC proliferation. It is well established that purines participate in synaptic transmission in the mature ENS. Our results describe, for the first time, purinergic signalling between ENCCs during pre-natal development, which plays roles in the propagation of Ca²⁺ waves between ENCCs and in ENCC network formation. One previous study has shown that calcium signalling plays a role in sympathetic ganglia formation; our results suggest that calcium waves are likely to be important for enteric ganglia development.

Defining the transcriptomic landscape of the developing enteric nervous system and its cellular environment

BACKGROUND

Motility and the coordination of moving food through the gastrointestinal tract rely on a complex network of neurons known as the enteric nervous system (ENS). Despite its critical function, many of the molecular mechanisms that direct the development of the ENS and the elaboration of neural network connections remain unknown. The goal of this study was to transcriptionally identify molecular pathways and candidate genes that drive specification, differentiation and the neural circuitry of specific neural progenitors, the phox2b expressing ENS cell lineage, during normal enteric nervous system development. Because ENS development is tightly linked to its environment, the transcriptional landscape of the cellular environment of the intestine was also analyzed.

RESULTS

Thousands of zebrafish intestines were manually dissected from a transgenic line expressing green fluorescent protein under the phox2b regulatory elements [Tg(phox2b:EGFP) ^w37 ]. Fluorescence-activated cell sorting was used to separate GFP-positive phox2b expressing ENS progenitor and derivatives from GFP-negative intestinal cells. RNA-seq was performed to obtain accurate, reproducible transcriptional profiles and the unbiased detection of low level transcripts. Analysis revealed genes and pathways that may function in ENS cell determination, genes that may be identifiers of different ENS subtypes, and genes that define the non-neural cellular microenvironment of the ENS. Differential expression analysis between the two cell populations revealed the expected neuronal nature of the phox2b expressing lineage including the enrichment for genes required for neurogenesis and synaptogenesis, and identified many novel genes not previously associated with ENS development. Pathway analysis pointed to a high level of G-protein coupled pathway activation, and identified novel roles for candidate pathways such as the Nogo/Reticulon axon guidance pathway in ENS development.

CONCLUSION

We report the comprehensive gene expression profiles of a lineage-specific population of enteric progenitors, their derivatives, and their microenvironment during normal enteric nervous system development. Our results confirm previously implicated genes and pathways required for ENS development, and also identify scores of novel candidate genes and pathways. Thus, our dataset suggests various potential mechanisms that drive ENS development facilitating characterization and discovery of novel therapeutic strategies to improve gastrointestinal disorders.

Osteopathic Manipulative Treatment Limits Chronic Constipation in a Child with Pitt-Hopkins Syndrome

Pitt-Hopkins Syndrome (PTHS) is a rare genetic disorder caused by insufficient expression of the TCF4 gene. Children with PTHS typically present with gastrointestinal disorders and early severe chronic constipation is frequently found (75%). Here we describe the case of a PTHS male 10-year-old patient with chronic constipation in whom Osteopathic Manipulative Treatment (OMT) resulted in improved bowel functions, as assessed by the diary, the QPGS-Form A Section C questionnaire, and the Paediatric Bristol Stool Form Scale. The authors suggested that OMT may be a valid tool to improve the defecation frequency and reduce enema administration in PTHS patients.

A novel enteric neuron-glia coculture system reveals the role of glia in neuronal development

KEY POINTS

Unlike astrocytes in the brain, the potential role of enteric glial cells (EGCs) in the formation of the enteric neuronal circuit is currently unknown. To examine the role of EGCs in the formation of the neuronal network, we developed a novel neuron-enriched culture model from embryonic rat intestine grown in indirect coculture with EGCs. We found that EGCs shape axonal complexity and synapse density in enteric neurons, through purinergic- and glial cell line-derived neurotrophic factor-dependent pathways. Using a novel and valuable culture model to study enteric neuron-glia interactions, our study identified EGCs as a key cellular actor regulating neuronal network maturation.

ABSTRACT

In the nervous system, the formation of neuronal circuitry results from a complex and coordinated action of intrinsic and extrinsic factors. In the CNS, extrinsic mediators derived from astrocytes have been shown to play a key role in neuronal maturation, including dendritic shaping, axon guidance and synaptogenesis. In the enteric nervous system (ENS), the potential role of enteric glial cells (EGCs) in the maturation of developing enteric neuronal circuit is currently unknown. A major obstacle in addressing this question is the difficulty in obtaining a valuable experimental model in which enteric neurons could be isolated and maintained without EGCs. We adapted a cell culture method previously developed for CNS neurons to establish a neuron-enriched primary culture from embryonic rat intestine which was cultured in indirect coculture with EGCs. We demonstrated that enteric neurons grown in such conditions showed several structural, phenotypic and functional hallmarks of proper development and maturation. However, when neurons were grown without EGCs, the complexity of the axonal arbour and the density of synapses were markedly reduced, suggesting that glial-derived factors contribute strongly to the formation of the neuronal circuitry. We found that these effects played by EGCs were mediated in part through purinergic P2Y1 receptor- and glial cell line-derived neurotrophic factor-dependent pathways. Using a novel and valuable culture model to study enteric neuron-glia interactions, our study identified EGCs as a key cellular actor required for neuronal network maturation.

Neuro-Immune Interactions at Barrier Surfaces

Multidirectional interactions between the nervous and immune systems have been documented in homeostasis and pathologies ranging from multiple sclerosis to autism, and from leukemia to acute and chronic inflammation. Recent studies have addressed this crosstalk using cell-specific targeting, novel sequencing, imaging, and analytical tools, shedding light on unappreciated mechanisms of neuro-immune regulation. This Review focuses on neuro-immune interactions at barrier surfaces-mostly the gut, but also including the skin and the airways, areas densely populated by neurons and immune cells that constantly sense and adapt to tissue-specific environmental challenges.

Distinct pattern of enteric phospho-alpha-synuclein aggregates and gene expression profiles in patients with Parkinson's disease

Phosphorylated alpha-synuclein (p-α-syn) containing Lewy bodies (LBs) and Lewy neurites (LNs) are neuropathological hallmarks of Parkinson’s disease (PD) in the central nervous system (CNS). Since they have been also demonstrated in the enteric nervous system (ENS) of PD patients, the aim of the study was to analyze enteric p-α-syn positive aggregates and intestinal gene expression. Submucosal rectal biopsies were obtained from patients with PD and controls and processed for dual-label-immunohistochemistry for p-α-syn and PGP 9.5. p-α-syn positive aggregates in nerve fibers and neuronal somata were subjected to a morphometric analysis. mRNA expression of α-syn and dopaminergic, serotonergic, VIP (vaso intestinal peptide) ergic, cholinergic, muscarinergic neurotransmitter systems were investigated using qPCR. Frequency of p-α-syn positive nerve fibers was comparable between PD and controls. Although neuronal p-α-syn positive aggregates were detectable in both groups, total number and area of p-α-syn positive aggregates were increased in PD patients as was the number of small and large sized aggregates. Increased expression of dopamine receptor D1, VIP and serotonin receptor 3A was observed in PD patients, while serotonin receptor 4 and muscarinic receptor 3 (M3R) were downregulated. M3R expression correlated negative with the number of small sized p-α-syn positive aggregates. The findings strengthen the hypothesis that the CNS pathology of increased p-α-syn in PD also applies to the ENS, if elaborated morphometry is applied and give further insights in altered intestinal gene expression in PD. Although the mere presence of p-α-syn positive aggregates in the ENS should not be regarded as a criterion for PD diagnosis, elaborated morphometric analysis of p-α-syn positive aggregates in gastrointestinal biopsies could serve as a suitable tool for in-vivo diagnosis of PD.

Identifying key genes associated with Hirschsprung's disease based on bioinformatics analysis of RNA-sequencing data

BACKGROUND

Hirschsprung's disease (HSCR) is a type of megacolon induced by deficiency or dysfunction of ganglion cells in the distal intestine and is associated with developmental disorders of the enteric nervous system. To explore the mechanisms of HSCR, we analyzed the RNA-sequencing data of the expansion and the narrow segments of colon tissues separated from children with HSCR.

METHODS

RNA-sequencing of the expansion segments and the narrow segments of colon tissues isolated from children with HSCR was performed. After differentially expressed genes (DEGs) were identified using the edgeR package in R, functional and pathway enrichment analyses of DEGs were carried out using DAVID software. To further screen the key genes, protein-protein interaction (PPI) network and module analyses were conducted separately using Cytoscape software.

RESULTS

A total of 117 DEGs were identified in the expansion segment samples, including 47 up-regulated and 70 down-regulated genes. Functional enrichment analysis suggested that FOS and DUSP1 were implicated in response to endogenous stimulus. In the PPI network analysis, FOS (degree=20), EGR1 (degree=16), ATF3 (degree=9), NOS1 (degree=8), CCL5 (degree=8), DUSP1 (degree=7), CXCL3 (degree=6), VIP (degree=6), FOSB (degree=5), and NOS2 (degree=4) had higher degrees, which could interact with other genes. In addition, two significant modules (module 1 and module 2) were identified from the PPI network.

CONCLUSIONS

Several genes (including FOS, EGR1, ATF3, NOS1, CCL5, DUSP1, CXCL3, VIP, FOSB, and NOS2) might be involved in the development of HSCR through their effect on the nervous system.

Decreased expression of NEDL2 in Hirschsprung's disease

PURPOSE

NEDD4-like ubiquitin protein ligase 2 (NEDL2) plays an important role in many physiological and pathological processes. NEDL2 is a positive regulator of GDNF/Ret signaling during enteric neurogenesis. Mice lacking NEDL2 exhibit decreased numbers of enteric neurons, progressive bowel dysmotility and intestinal hypoganglionosis. We designed this study to investigate the expression of NEDL2 in the normal human colon and in HSCR.

METHODS

HSCR tissue specimens (n=10) were collected at the time of pull-through surgery and divided into aganglionic and ganglionic segments. Colonic control samples (n=10) were obtained from patients with imperforate anus at the time of colostomy closure. Immunolabeling of NEDL2 was visualized using confocal microscopy to assess protein distribution, while Western blot analysis was undertaken to quantify NEDL2 protein expression.

RESULTS

Confocal microscopy revealed that NEDL2-immunoreactivity colocalized with ICCs and neurons within the submucosa, myenteric plexus and smooth muscle in controls and ganglionic specimens, with markedly reduced NEDL2-immunoreactivity in aganglionic specimens. Western blotting revealed high levels of the NEDL2 protein in normal controls and the ganglionic region of HSCR, while there was a marked decrease in NEDL2 protein expression in the aganglionic region of HSCR.

CONCLUSION

We report, for the first time, the expression of NEDL2 in the human colon. The decreased expression of NEDL2 in the aganglionic colon suggests that NEDL2 may play a role in the pathophysiology of HSCR.

Targeting the gastrointestinal tract with viral vectors: state of the art and possible applications in research and therapy

While there is a large body of preclinical data on the use of viral vectors in gene transfer, relatively little is known about viral gene transfer in the gastrointestinal tract. Viral vector technology is especially underused in the field of neurogastroenterology when compared to brain research. This review provides an overview of the studies employing viral vectors-in particular retroviruses, adenoviruses and adeno-associated viruses-to transduce different cell types in the intestine. Early work mainly focused on mucosal transduction, but had limited success due to the harsh luminal conditions in the gastrointestinal tract and the high turnover rate of enterocytes. More recently, several studies have successfully employed viral gene transfer to target the enteric nervous system and its progenitors. Although several hurdles still need to be overcome, in particular on how to augment transduction efficiency and specific cell targeting, viral vector technology holds strong potential not only as a valid research tool in fundamental gastroenterological research but also as a therapeutic agent in translational (bio)medical research.

The bowel and beyond: the enteric nervous system in neurological disorders

The enteric nervous system (ENS) is large, complex and uniquely able to orchestrate gastrointestinal behaviour independently of the central nervous system (CNS). An intact ENS is essential for life and ENS dysfunction is often linked to digestive disorders. The part the ENS plays in neurological disorders, as a portal or participant, has also become increasingly evident. ENS structure and neurochemistry resemble that of the CNS, therefore pathogenic mechanisms that give rise to CNS disorders might also lead to ENS dysfunction, and nerves that interconnect the ENS and CNS can be conduits for disease spread. We review evidence for ENS dysfunction in the aetiopathogenesis of autism spectrum disorder, amyotrophic lateral sclerosis, transmissible spongiform encephalopathies, Parkinson disease and Alzheimer disease. Animal models suggest that common pathophysiological mechanisms account for the frequency of gastrointestinal comorbidity in these conditions. Moreover, the neurotropic pathogen, varicella zoster virus (VZV), unexpectedly establishes latency in enteric and other autonomic neurons that do not innervate skin. VZV reactivation in these neurons produces no rash and is therefore a clandestine cause of gastrointestinal disease, meningitis and strokes. The gut-brain alliance has raised consciousness as a contributor to health, but a gut-brain axis that contributes to disease merits equal attention.

Postnatal development of the dopaminergic signaling involved in the modulation of intestinal motility in mice

BACKGROUND

Since antidopaminergic drugs are pharmacological agents employed in the management of gastrointestinal motor disorders at all ages, we investigated whether the enteric dopaminergic system may undergo developmental changes after birth.

METHODS

Intestinal mechanical activity was examined in vitro as changes in isometric tension.

RESULTS

In 2-d-old (P2) mice, dopamine induced a contractile effect, decreasing in intensity with age, replaced, at the weaning (day 20), by a relaxant response. Both responses were tetrodotoxin (TTX)-insensitive. In P2, dopaminergic contraction was inhibited by D1-like receptor antagonist and mimicked by D1-like receptor agonist. In 90-d-old (P90) mice, the relaxation was reduced by both D1- and D2-like receptor antagonists, and mimicked by D1- and D2-like receptor agonists. In P2, contraction was antagonized by phospholipase C inhibitor, while in P90 relaxation was antagonized by adenylyl cyclase inhibitor and potentiated by phospholipase C inhibitor. The presence of dopamine receptors was assessed by immunofluorescence. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed a significant increase in D1, D2, and D3 receptor expression in proximal intestine with the age.

CONCLUSION

In mouse small intestine, the response to dopamine undergoes developmental changes shifting from contraction to relaxation at weaning, as the consequence of D2-like receptor recruitment and increased expression of D1 receptors.

Negative feedback circuitry between MIR143HG and RBM24 in Hirschsprung disease

Hirschsprung disease (HSCR) is a genetic disorder of neural crest development. It is also believed that epigenetic changes plays a role in the progression of this disease. Here we show that the MIR143 host gene (MIR143HG), the precursor of miR-143 and miR-145, decreased cell proliferation and migration and forms a negative feedback loop with RBM24 in HSCR. As RBM24 mRNA is a target of miR-143, upregulation of RBM24 upon an increase in the level of MIR143HG could be attributed to sequestration of miR-143 by MIR143HG (sponge effect). The RBM24 protein was shown to bind to MIR143HG, and subsequently, accelerated its degradation by destabilizing its transcript and facilitating its interaction with Ago2, thus forming a negative feedback between MIR143HG and RBM24. In addition, experiments using siRNA against DROSHA indicated that RBM24 could promote the biogenesis of miR-143. This feedback loop we describe here represents a novel mode of autoregulation, with implications in HSCR pathogenesis.

Suppressive action of miRNAs to ARP2/3 complex reduces cell migration and proliferation via RAC isoforms in Hirschsprung disease

Hirschsprung disease (HSCR) is a congenital disorder caused by the defective function of the embryonic enteric neural crest. The impaired migration of embryonic enteric neural crest plays an important role in the pathogenesis of this disease. Recent studies showed that the ARP2/3 complex and RAC isoforms had effects on actin cytoskeleton remodelling, which contributes to migration. Moreover, some regulatory relationships were identified between ARP2/3 complex and RAC isoforms. Although microRNAs (miRNAs) have been known to modulate target gene expression on the post-transcriptional level, little is known about the regulation among miRNAs, ARP2/3 complex and RAC isoforms. Here, we report that down-regulation of ARP2 and ARP3, two main subunits of ARP2/3 complex, suppressed migration and proliferation in 293T and SH-SY5Y cell lines via the inhibition of RAC1 and RAC2. Meanwhile, as the target genes, ARP2 and ARP3 are reduced by increased miR-24-1* and let-7a*, respectively, in 70 HSCR samples as compared with 74 normal controls. Co-immunoprecipitation showed that aberrant reduction in ARP2 and ARP3 could weaken the function of ARP2/3 complex. Our study demonstrates that the miR-24-1*/let-7a*-ARP2/3 complex-RAC isoforms pathway may represent a novel pathogenic mechanism for HSCR.

Functional Coupling with Cardiac Muscle Promotes Maturation of hPSC-Derived Sympathetic Neurons

Neurons derived from human pluripotent stem cells (hPSCs) are powerful tools for studying human neural development and diseases. Robust functional coupling of hPSC-derived neurons with target tissues in vitro is essential for modeling intercellular physiology in a dish and to further translational studies, but it has proven difficult to achieve. Here, we derive sympathetic neurons from hPSCs and show that they can form physical and functional connections with cardiac muscle cells. Using multiple hPSC reporter lines, we recapitulated human autonomic neuron development in vitro and successfully isolated PHOX2B::eGFP+ neurons that exhibit sympathetic marker expression and electrophysiological properties and norepinephrine secretion. Upon pharmacologic and optogenetic manipulation, PHOX2B::eGFP+ neurons controlled beating rates of cardiomyocytes, and the physical interactions between these cells increased neuronal maturation. This study provides a foundation for human sympathetic neuron specification and for hPSC-based neuronal control of organs in a dish.