Allan M. Goldstein

Multisystemic smooth muscle dysfunction syndrome (MSMDS) is a rare disorder caused by ACTA2 mutations, including the R179H variant, which alters actin filament stability and dynamics and smooth muscle contractility. Cardiovascular complications dominate its clinical presentation, but gastrointestinal (GI) dysfunction significantly affects quality of life. To investigate the structural, functional, and cellular basis of gut dysmotility in MSMDS, we reviewed clinical data from 24 patients with MSMDS and studied the ACTA2 R179H mouse model. Patients exhibited severe gut dysmotility, with 75% requiring medication for chronic constipation. ACTA2 mutant mice displayed cecal and colonic dilatation, reduced intestinal length, and disrupted colonic migrating motor complexes. Delayed whole-gut transit and impaired contractile responses to electrical and pharmacological stimulation were observed. Transcriptomic analysis revealed significant actin cytoskeleton-related gene changes in smooth muscle cells, and immune profiling identified increased lymphocytic infiltration. Despite functional abnormalities, there were no obvious changes in the enteric nervous system. These findings establish ACTA2 mice as a robust model for studying GI pathology in MSMDS, elucidating the role of smooth muscle dysfunction in gut dysmotility. This model provides a foundation for developing targeted therapies aimed at restoring intestinal motility by directly addressing actin cytoskeletal disruptions in smooth muscle cells.

Hirschsprung disease (HSCR) is a neurocristopathy, yet paradoxically, neural crest-derived EGCs are present within the muscle of the affected region. This study investigates the molecular identity, origins, and neurogenic potential of EGCs in the aganglionic mouse and human colon. We utilized single-cell RNA sequencing (scRNA-seq), immunohistochemistry, and in vitro culture of EGCs from aganglionic and ganglionated segments of Ednrb-null mice (Plp1-GFP;Baf-tdT;Ednrb^−/−) and human HSCR tissues. Neurogenic potential and network formation were assessed, and the effects of glial cell line-derived neurotrophic factor (GDNF) on neurogenesis were evaluated. scRNA-seq and immunohistochemistry revealed the absence of GFAP+ intraganglionic (IG) glia in aganglionic colon, while CAMK2b+ extraganglionic (EG) glia and Schwann-like cells (SLCs) were present. EG glia exhibited a transcriptional profile similar to SLCs, suggesting a possible shared embryonic origin. EGCs in the aganglionic segment (comprising EGs and SLCs) exhibited reduced neurogenic potential and network complexity compared to EGCs from the ganglionated region (comprising EGs and IGs). GDNF partially restored neurogenic capacity and enhanced network complexity of EGCs isolated from the aganglionic segment, acting through a non-canonical NCAM1-dependent pathway independent of RET signaling.

10.1136/wjps-2025-001032.video01 6376273975112 BMJ Journals Video Player wjps2025001032media1

Neurosensory circuits of the gastrointestinal tract sense microbial and nutrient changes in the gut; however, studying these circuits in vivo is hindered by invasive techniques and ethical concerns. Here, an in vitro model of enteroendocrine cells (EECs) and calcium reporting enteric neurons (ENs) is established and validated for functional signaling. Both mechanical and sucrose stimulation of co‐cultures increased the percentage of neurons undergoing a calcium flux, indicating an action potential. Neuronal activation is blocked with either a piezo or insulin receptor blocker. At baseline, a flow only stimulus elicited 51.9% of neurons to activate in co‐culture, which is decreased to 15.1% with a piezo blocker. Piezo blocked and sucrose stimulated EECs increased neuronal activation to 43.9%, and an insulin blocker reduced response to 12.4%. Since a cell line is used to model the EEC in the previous experiments, primary rat duodenal epithelium enriched for EECs are also stimulated and found to produced measurable insulin. This work shows the ability of EECs to produce insulin and for ENs to sense insulin. These results inspire further work on how insulin production outside the pancreas effects diabetes, insulin as a neurotransmitter, and exploration of additional nutritional and microbiotic stimuli on enteroendocrine‐to‐neuronal signaling.

Hirschsprung disease (HSCR) is a congenital enteric neuropathy in which the enteric nervous system (ENS) fails to develop along variable lengths of the distal gastrointestinal (GI) tract. This aganglionosis results in a functional bowel obstruction and requires surgical resection of the aganglionic segment. Despite surgery, however, long-term bowel dysfunction affects many patients. Understanding the embryologic causes and pathophysiologic consequences of HSCR is critical to improving its diagnosis and treatment. During normal gut development, the ENS arises from neural crest cells (NCCs) that delaminate from the neural tube to populate the entire GI tract with enteric neurons and glia. This process requires NCCs to undergo proliferation, migration and differentiation to form the complex neuroglial network that regulates gut motility and other intestinal functions. This review discusses the cellular and molecular processes that control normal ENS formation and what goes awry to give rise to HSCR. The complex pathophysiologic consequences of aganglionosis are discussed, including recent observations that describe novel aspects of HSCR beyond the absence of ganglion cells. This review aims to expand the understanding of HSCR and to stimulate new ideas on how to improve current management of the disease.

The goal of this study was to determine if transplantation of enteric neural stem cells (ENSCs) can rescue the enteric nervous system, restore gut motility, reduce colonic inflammation, and improve survival in the Ednrb-KO mouse model of Hirschsprung disease (HSCR). ENSCs were isolated from mouse intestine, expanded to form neurospheres, and microinjected into the colons of recipient Ednrb-KO mice. Transplanted ENSCs were identified in recipient colons as cell clusters in “neo-ganglia.” Immunohistochemical evaluation demonstrated extensive cell migration away from the sites of cell delivery and across the muscle layers. Electrical field stimulation and optogenetics showed significantly enhanced contractile activity of aganglionic colonic smooth muscle following ENSC transplantation and confirmed functional neuromuscular integration of the transplanted ENSC-derived neurons. ENSC injection also partially restored the colonic migrating motor complex. Histological examination revealed a significant reduction in inflammation in ENSC-transplanted aganglionic recipient colon compared with that of sham-operated mice. Interestingly, mice that received cell transplant also had prolonged survival compared with controls. This study demonstrates that ENSC transplantation can improve outcomes in HSCR by restoring gut motility and reducing the severity of Hirschsprung-associated enterocolitis, the leading cause of death in human HSCR.