The gastrointestinal symptoms that impair quality of life in childhood neurodegenerative disorders, may be because bowel enteric neurons are also affected.

The Neuronal Ceroid Lipofuscinoses (NCLs) are fatal inherited lysosomal storage diseases, with pronounced neuron loss in the central nervous system (CNS). Gastrointestinal issues are frequently reported by people with NCLs, although mechanisms underlying these symptoms are poorly understood. We recently demonstrated degeneration occurs within the enteric nervous system (ENS) in several NCLs. Given that the gut microbiome has been shown to be altered a CLN2 mouse model (Tpp1R207X/R207X) and may potentially influence both CNS and ENS pathology, we investigated the long-term impact of modulating the gut microbiome in these mice. This was done by administering a VNAM antibiotic cocktail (vancomycin, neomycin, ampicillin, and metronidazole) for 1-week post-weaning, examining its effects at disease endstage. While VNAM treatment markedly altered the gut microbiome and caused significant loss of enteric neurons in wildtype mice, it did not exacerbate key pathological parameters in either bowel or brain of Tpp1R207X/R207X mice. These included histomorphometric changes in the small intestine and neurodegeneration of enteric neurons, or CNS neuropathology. However, we did find evidence for moderate protective effects of VNAM upon enteric neurons in the ileum, and upon CNS microglia, but all other pathologies were unaltered in Tpp1R207X/R207X mice. These findings suggest that intestinal and ENS pathology is primarily driven by TPP1-deficiency rather than changes in the gut microbiome. Indeed, these alterations to the gut microbiome may occur secondary to the impact of CLN2 disease upon the bowel.

BACKGROUND:Visceral myopathy (VSCM) is an ultra-rare life-threatening condition characterized by severe impairment of gastrointestinal (GI), genitourinary, and uterine smooth muscle. This disorder represents a significant clinical challenge due to variable presentation and the lack of standardized diagnostic and therapeutic protocols. METHODS:To discuss advances in the field, scientists and clinicians with a special interest in VSCM met in Arenzano, Genova, Italy in October 2024 for the second International Forum on Visceral Myopathy 2024 (IFVM2024) (https://ifvm2024.ge.ibf.cnr.it/). KEY RESULTS:As in the previous edition of the event (https://poic-e-dintorni.org/efvm-2022/), attendees included clinicians and researchers from around the world who study this disease, representatives from support organizations, patients affected by VSCM and their families, and companies that co-funded the event. The present manuscript aims to summarize knowledge shared during the IFVM2024 conference, thus providing an updated state-of-the-art summary of VSCM biology and disease management. CONCLUSIONS:Here, we pay particular attention to the epidemiology of the disease, histopathology, genetics, novel treatments, advances in molecular and cell biology, experimental models, and the lived experiences and impact of this disorder on families.

Objectives Pediatric intestinal pseudo-obstruction (PIPO) is a severe bowel motility disorder characterized by impaired propulsion of gastrointestinal contents without mechanical obstruction. PIPO encompasses congenital and acquired disorders, including neuropathies, myopathies, and mesenchymopathies. PIPO presents with abdominal distension, bilious vomiting, and severe constipation. Diagnosis is based on objective measures of neuromuscular dysfunction, dilated bowel on imaging, parenteral and/or enteral nutrition dependence, and genetic or metabolic testing. Antroduodenal manometry permits objective assessment of proximal bowel neuromuscular function. Genetic testing is increasingly valuable although causes of PIPO often remain incompletely defined. Understanding genotype-phenotype correlations is essential for clarifying disease mechanisms and guiding therapies. This study aimed to characterize the clinical and genetic profiles of children with PIPO, utilizing manometric data for subtype classification.Methods A retrospective chart review was conducted at a tertiary care pediatric medical center, with inclusion criteria of PIPO diagnosis, completed manometry testing, and genetic evaluation.Results Nineteen children met inclusion criteria. Antroduodenal manometry classified 59% as neuropathic, 35% as myopathic, and one with mixed neuropathic and myopathic dysfunction. Genetic testing revealed pathogenic ACTG2 mutations in all myopathic cases, while neuropathic PIPO exhibited more genetic variability. Histopathology was inconsistent and often nonspecific. Therapeutic approaches focused on nutritional support and promotility agents, with surgical intervention more common in myopathic cases.Conclusions This study highlights the association of ACTG2 mutations with a myopathic phenotype, and genetic diversity in neuropathic PIPO, emphasizing the need for further research to improve phenotyping to enhance diagnosis and treatment.

Diverticular disease is a common and morbid complex phenotype influenced by both innate and environmental risk factors. We performed the largest genome-wide association study meta-analysis for diverticular disease, identifying 126 novel loci. Employing multiple downstream analytic strategies, including tissue and pathway enrichment, statistical fine-mapping, allele-specific expression, protein quantitative trait loci and drug-target investigations, and linkage disequilibrium score regression, we prioritized causal genes and produced several lines of evidence linking diverticular disease to connective tissue biology and colonic motility. We substantiated these findings by integrating single-cell RNA sequencing data, showing that prioritized diverticular disease-associated genes are enriched for expression in colonic smooth muscle, fibroblasts, and interstitial cells of Cajal. In quantitative analysis of surgical specimens, we found a substantial reduction in the density of elastin present in the sigmoid colon in severe diverticulitis.

Enterocolitis is a common and potentially deadly manifestation of Hirschsprung disease (HSCR) but disease mechanisms remain poorly defined. Unexpectedly, we discovered that diet can dramatically affect the lifespan of a HSCR mouse model ( Piebald lethal , sl/sl ) where affected animals die from HAEC complications. In the sl/sl model, diet alters gut microbes and metabolites, leading to changes in colon epithelial gene expression and epithelial oxygen levels known to influence colitis severity. Our findings demonstrate unrecognized similarity between HAEC and other types of colitis and suggest dietary manipulation could be a valuable therapeutic strategy for people with HSCR. Abstract:Hirschsprung disease (HSCR) is a birth defect where enteric nervous system (ENS) is absent from distal bowel. Bowel lacking ENS fails to relax, causing partial obstruction. Affected children often have "Hirschsprung disease associated enterocolitis" (HAEC), which predisposes to sepsis. We discovered survival of Piebald lethal ( sl/sl ) mice, a well-established HSCR model with HAEC, is markedly altered by two distinct standard chow diets. A "Protective" diet increased fecal butyrate/isobutyrate and enhanced production of gut epithelial antimicrobial peptides in proximal colon. In contrast, "Detrimental" diet-fed sl/sl had abnormal appearing distal colon epithelium mitochondria, reduced epithelial mRNA involved in oxidative phosphorylation, and elevated epithelial oxygen that fostered growth of inflammation-associated Enterobacteriaceae . Accordingly, selective depletion of Enterobacteriaceae with sodium tungstate prolonged sl/sl survival. Our results provide the first strong evidence that diet modifies survival in a HSCR mouse model, without altering length of distal colon lacking ENS. Highlights:Two different standard mouse diets alter survival in the Piebald lethal ( sl/sl ) mouse model of Hirschsprung disease, without impacting extent of distal colon aganglionosis (the region lacking ENS). Piebald lethal mice fed the "Detrimental" diet had many changes in colon epithelial transcriptome including decreased mRNA for antimicrobial peptides and genes involved in oxidative phosphorylation. Detrimental diet fed sl/sl also had aberrant-appearing mitochondria in distal colon epithelium, with elevated epithelial oxygen that drives lethal Enterobacteriaceae overgrowth via aerobic respiration. Elimination of Enterobacteriaceae with antibiotics or sodium tungstate improves survival of Piebald lethal fed the "Detrimental diet". Graphical abstract:

Bowel smooth muscle experiences mechanical stress constantly during normal function and pathologic mechanical stressors in disease states. We tested the hypothesis that pathologic mechanical stress could alter transcription to induce smooth muscle phenotypic class switching. To test this hypothesis, primary human intestinal smooth muscle cells (HISMCs), seeded on electrospun aligned poly-ε-caprolactone nano-fibrous scaffolds, were subjected to pathologic, high-frequency (1 Hz) uniaxial 3% cyclic stretch (loaded) or kept unloaded in culture for 6 hours. RNA-Seq, quantitative PCR (qPCR), and quantitative IHC defined loading-induced changes in gene expression. NicheNet predicted how differentially expressed genes might affect HISMCs and other bowel cells. These studies show loading induced differential expression of 4,537 HISMC genes. Loaded HISMCs had a less contractile phenotype, with increased expression of synthetic SMC genes, proinflammatory cytokines, and altered expression of axon guidance molecules, growth factors, and morphogens. Many differentially expressed genes encode secreted ligands that could act cell autonomously on smooth muscle and on other cells in the bowel wall. These data show that HISMCs undergo remarkably rapid phenotypic plasticity in response to mechanical stress that may convert contractile HISMCs into proliferative fibroblast-like cells or proinflammatory cells. These mechanical stress-induced changes in HISMC gene expression may be relevant for human bowel disease.

Severe gastrointestinal (GI) symptoms occur in people with CLN3 disease, a neurodegenerative disorder. If left untreated these GI symptoms compromise life quality and may contribute to death. We hypothesized GI symptoms in CLN3 disease are at least partially due to neurodegeneration in the enteric nervous system (ENS), the master regulator of bowel function. We examined the integrity of the ENS in human CLN3 autopsy small bowel and colon, and in CLN3 deficient (Cln3Δex7/8) mice. We performed detailed immunohistological analyses of enteric neurons and glia and assessed bowel transit times at multiple disease stages. We then tested the therapeutic potential of neonatal intravenous gene therapy (AAV9.hCLN3) to prevent bowel phenotypes in Cln3Δex7/8 mice. Human CLN3 bowel displayed a profound loss of enteric neurons and their neurites, with pathological effects upon enteric glia. Cln3Δex7/8 mice had normal appearing ENS at 1 month of age, but then experienced progressive loss of both enteric neurons and glia accompanied by marked bowel distention, resembling the human CLN3 phenotype. Degenerative changes in Cln3Δex7/8 mouse enteric neurons and glia were largely prevented by systemic neonatal delivery of AAV9.hCLN3 gene therapy, preventing bowel distention at disease endstage. Our findings demonstrate that CLN3 deficiency profoundly damages enteric neurons and glia in both murine and human CLN3 disease, contributing to GI dysfunction. This study provides preclinical evidence that systemic gene therapy may effectively treat multiple aspects of bowel pathology, expanding the therapeutic landscape beyond the CNS.

Lysosomal storage disorders and their impact upon the central nervous system:Lysosomal storage disorders(LSDs)are a group of over 70 rare inherited metabolic disorders(Platt et al.,2018).They are caused by dysfunction of lysosomes,organelles that contain enzymes responsible for digesting macromolecules.In functional lysosomes,these enzymes break down complex substrates,and the resulting fragments are recycled.

Children with neurodegenerative disease often have debilitating gastrointestinal symptoms. We hypothesized that this may be due at least in part to underappreciated degeneration of neurons in the enteric nervous system (ENS), the master regulator of bowel function. To test this hypothesis, we evaluated mouse models of neuronal ceroid lipofuscinosis type 1 and 2 (CLN1 and CLN2 disease, respectively), neurodegenerative lysosomal storage disorders caused by deficiencies in palmitoyl protein thioesterase-1 and tripeptidyl peptidase-1, respectively. Both mouse lines displayed slow bowel transit in vivo that worsened with age. Although the ENS appeared to develop normally in these mice, there was a progressive and profound loss of myenteric plexus neurons accompanied by changes in enteric glia in adult mice. Similar pathology was evident in colon autopsy material from a child with CLN1 disease. Neonatal administration of adeno-associated virus-mediated gene therapy prevented bowel transit defects, ameliorated loss of enteric neurons, and extended survival in mice. Treatment after weaning was less effective than treating neonatally but still extended the lifespan of CLN1 disease mice. These data provide proof-of-principle evidence of ENS degeneration in two lysosomal storage diseases and suggest that gene therapy can ameliorate ENS disease, also improving survival.

AbstractCLN3 disease causes profound neurological deficits in affected children, but less well recognized are a variety of peripheral neuromuscular and gastrointestinal problems. We hypothesized that in addition to central nervous system (CNS) degeneration, CLN3 deficiency may also directly affect neuronal and/or glial cell populations in the rest of the body. Therefore, we examined the neuromuscular and enteric nervous system inCln3Δex7/8mice. There was no overt sciatic nerve axon loss or demyelination inCln3Δex7/8mice, but significant loss of terminal Schwann cells (tSCs) at lower limb neuromuscular junctions (NMJ), and progressive NMJ denervation. This was accompanied by pronounced myofiber atrophy, with fewer and displaced myofibril nuclei, with similar pathology seen in a human CLN3 muscle biopsy. Atrophy was also evident in bowel smooth muscle withCln3Δex7/8mice displaying slow bowel transit, and significant loss of both enteric neurons and glial cells throughout the bowel. Similar enteric pathology was evident at autopsy in the small intestine and colon of a human CLN3 case. Neonatal administration of intravenous gene therapy toCln3Δex7/8mice using an AAV9-hCLN3 vector completely prevented tSCs and NMJ pathology, atrophy of both skeletal and smooth muscle, positively impacted bowel transit and largely prevented the loss of enteric neurons and glia. These findings reveal an underappreciated, but profound, impact of CLN3 disease outside the CNS and suggest these novel aspects of disease may be treatable using gene therapy.Graphical abstract

BACKGROUND & AIMS:Hirschsprung's disease is defined by the absence of the enteric nervous system (ENS) from the distal bowel. Primary treatment is "pull-through" surgery to remove bowel that lacks ENS, with reanastomosis of "normal" bowel near the anal verge. Problems after pull-through are common, and some may be due to retained hypoganglionic bowel (ie, low ENS density). Testing this hypothesis has been difficult because counting enteric neurons in tissue sections is unreliable, even for experts. Tissue clearing and 3-dimensional imaging provide better data about ENS structure than sectioning. METHODS:Regions from 11 human colons and 1 ileal specimen resected during Hirschsprung's disease pull-through surgery were cleared, stained with antibodies to visualize the ENS, and imaged by confocal microscopy. Control distal colon from people with no known bowel problems were similarly cleared, stained, and imaged. RESULTS:Quantitative analyses of human colon, ranging from 3 days to 60 years old, suggest age-dependent changes in the myenteric plexus area, ENS ganglion area, percentage of myenteric plexus occupied by ganglia, neurons/mm2, and neuron Feret's diameter. Neuron counting using 3-dimensional images was highly reproducible. High ENS density in neonatal colon allowed reliable neuron counts using 500-μm2 × 500-μm2 regions (36-fold smaller than in adults). Hirschsprung's samples varied 8-fold in proximal margin enteric neuron density and had diverse ENS architecture in resected bowel. CONCLUSIONS:Tissue clearing and 3-dimensional imaging provide more reliable information about ENS structure than tissue sections. ENS structure changes during childhood. Three-dimensional ENS anatomy may provide new insight into human bowel motility disorders, including Hirschsprung's disease.

Epigenetic regulatory mechanisms are underappreciated, yet are critical for enteric nervous system (ENS) development and maintenance. We discovered that fetal loss of the epigenetic regulator Bap1 in the ENS lineage caused severe postnatal bowel dysfunction and early death in Tyrosinase-Cre Bap1 fl/fl mice. Bap1 -depleted ENS appeared normal in neonates; however, by P15, Bap1 -deficient enteric neurons were largely absent from the small and large intestine of Tyrosinase-Cre Bap1 fl/fl mice. Bowel motility became markedly abnormal with disproportionate loss of cholinergic neurons. Single -cell RNA sequencing at P5 showed that fetal Bap1 loss in Tyrosinase-Cre Bap1 fl/fl mice markedly altered the composition and relative proportions of enteric neuron subtypes. In contrast, postnatal deletion of Bap1 did not cause enteric neuron loss or impaired bowel motility. These findings suggest that BAP1 is critical for postnatal enteric neuron differentiation and for early enteric neuron survival, a finding that may be relevant to the recently described human BAP1-associated neurodevelopmental disorder.

Background and Aims:Bowel smooth muscle experiences mechanical stress constantly during normal function, and pathologic mechanical stressors in disease states. We tested the hypothesis that pathologic mechanical stress could alter transcription to induce smooth muscle phenotypic class switching. Methods:Primary human intestinal smooth muscle cells (HISMCs), seeded on electrospun aligned poly-ε-caprolactone nano-fibrous scaffolds, were subjected to pathologic, high frequency (1 Hz) uniaxial 3% cyclic stretch (loaded) or kept unloaded in culture for 6 hours. Total RNA sequencing, qRT-PCR, and quantitative immunohistochemistry defined loading-induced changes in gene expression. NicheNet predicted how differentially expressed genes might impact HISMCs and other bowel cells. Results:Loading induced differential expression of 4537 genes in HISMCs. Loaded HISMCs had a less contractile phenotype, with increased expression of synthetic SMC genes, proinflammatory cytokines, and altered expression of axon guidance molecules, growth factors and morphogens. Many differentially expressed genes encode secreted ligands that could act cell-autonomously on smooth muscle and on other cells in the bowel wall. Discussion:HISMCs demonstrate remarkably rapid phenotypic plasticity in response to mechanical stress that may convert contractile HISMCs into proliferative, fibroblast-like cells or proinflammatory cells. These mechanical stress-induced changes in HISMC gene expression may be relevant for human bowel disease.

Visceral myopathy is a life-threatening disease characterized by muscle weakness in the bowel, bladder, and uterus. Mutations in smooth muscle γ-actin (ACTG2) are the most common cause of the disease, but the mechanisms by which the mutations alter muscle function are unknown. Here, we examined four prevalent ACTG2 mutations (R40C, R148C, R178C, and R257C) that cause different disease severity and are spread throughout the actin fold. R178C displayed premature degradation, R148C disrupted interactions with actin-binding proteins, R40C inhibited polymerization, and R257C destabilized filaments. Because these mutations are heterozygous, we also analyzed 50/50 mixtures with wild-type (WT) ACTG2. The WT/R40C mixture impaired filament nucleation by leiomodin 1, and WT/R257C produced filaments that were easily fragmented by smooth muscle myosin. Smooth muscle tropomyosin isoform Tpm1.4 partially rescued the defects of R40C and R257C. Cryo–electron microscopy structures of filaments formed by R40C and R257C revealed disrupted intersubunit contacts. The biochemical and structural properties of the mutants correlate with their genotype-specific disease severity.

A defining unique characteristic of the gut immune system is its ability to respond effectively to foreign pathogens while mitigating unnecessary inflammation. Intestinal macrophages serve as the cornerstone of this balancing act, acting uniquely as both the sword and shield in the gut microenvironment. The GI tract is densely innervated by the enteric nervous system (ENS), the intrinsic nervous system of the gut. Recent advances in sequencing technology have increasingly suggested neuroimmune crosstalk as a critical component for homeostasis both within the gut and in other tissues. Here, we systematically review the ENS–macrophage axis. We focus on the pertinent molecules produced by the ENS, spotlight the mechanistic contributions of intestinal macrophages to gut homeostasis and inflammation, and discuss both existing and potential strategies that intestinal macrophages use to integrate signals from the ENS. This review aims to elucidate the complex molecular basis governing ENS–macrophage signaling, highlighting their cooperative roles in sustaining intestinal health and immune equilibrium.

BAZ1B is one of 25-27 coding genes deleted in canonical Williams syndrome, a multi-system disorder causing slow growth, vascular stenosis, and gastrointestinal complaints, including constipation. BAZ1B is involved in (among other processes) chromatin organization, DNA damage repair, and mitosis, suggesting reduced BAZ1B may contribute to Williams syndrome symptoms. In mice, loss of Baz1b causes early neonatal death. 89.6% of Baz1b-/- mice die within 24 h of birth without vascular anomalies or congenital heart disease (except for patent ductus arteriosus). Some (<50%) Baz1b-/- were noted to have prolonged neonatal cyanosis, patent ductus arteriosus, or reduced lung aeration, and none developed a milk spot. Meanwhile, 35.5% of Baz1b+/- mice die over the first three weeks after birth. Surviving Baz1b heterozygotes grow slowly (with variable severity). 66.7% of Baz1b+/- mice develop bowel dilation, compared to 37.8% of wild-type mice, but small bowel and colon transit studies were normal. Additionally, enteric neuron density appeared normal in Baz1b-/- mice except in distal colon myenteric plexus, where neuron density was modestly elevated. Combined with several rare phenotypes (agnathia, microphthalmia, bowel dilation) recovered, our work confirms the importance of BAZ1B in survival and growth and suggests that reduced copy number of BAZ1B may contribute to the variability in Williams syndrome phenotypes.