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Crohn's disease (CD) is marked by recurring intestinal inflammation and tissue injury, often resulting in fibrostenosis and bowel obstruction, necessitating surgical intervention with high recurrence rates. To elucidate the mechanisms underlying fibrostenosis in CD, we analyzed the transcriptome of cells isolated from the transmural ileum of patients with CD, including a trio of lesions from each patient: non-affected, inflamed, and stenotic ileum samples, and compared them with samples from patients without CD. Our computational analysis revealed that profibrotic signals from a subset of monocyte- derived cells expressing CD150 induced a disease-specific fibroblast population, resulting in chronic inflammation and tissue fibrosis. The transcription factor TWIST1 was identified as a key modulator of fibroblast activation and extracellular matrix (ECM) deposition. Genetic and pharmacological inhibition of TWIST1 prevents fibroblast activation, reducing ECM production and collagen deposition. Our findings suggest that the myeloid-stromal axis may offer a promising therapeutic target to prevent fibrostenosis in CD., Introduction Crohn's disease (CD) is a chronic inflammatory condition affecting the gastrointestinal tract, characterized by transmural inflammation that often leads to complications such as strictures, fistulas, and abscesses. The disease [...]

Background Patients with inflammatory bowel disease [IBD] are considered immunosuppressed, but do not seem more vulnerable for COVID-19. Nevertheless, intestinal inflammation has shown to be an important risk factor for SARS-CoV-2 infection and prognosis. Therefore, we investigated the role of intestinal inflammation on the viral intestinal entry mechanisms, including ACE2, in IBD. Methods We collected inflamed and uninflamed mucosal biopsies from Crohn's disease [CD] [ n  = 193] and ulcerative colitis [UC] [ n  = 158] patients, and from 51 matched non-IBD controls for RNA sequencing, differential gene expression, and co-expression analysis. Organoids from UC patients were subjected to an inflammatory mix and processed for RNA sequencing. Transmural ileal biopsies were processed for single-cell [sc] sequencing. Publicly available colonic sc-RNA sequencing data, and microarrays from tissue pre/post anti-tumour necrosis factor [TNF] therapy, were analysed. Results In inflamed CD ileum, ACE2 was significantly decreased compared with control ileum [ p  = 4.6E-07], whereas colonic ACE2 was higher in inflamed colon of CD/UC compared with control [ p  = 8.3E-03; p  = 1.9E-03]. Sc-RNA sequencing confirmed this ACE2 dysregulation and exclusive epithelial ACE2 expression. Network analyses highlighted HNF4A as key regulator of ileal ACE2 , and pro-inflammatory cytokines and interferon regulating factors regulated colonic ACE2. Inflammatory stimuli upregulated ACE2 in UC organoids [ p  = 1.7E-02], but not in non-IBD controls [ p  = 9.1E-01]. Anti-TNF therapy restored colonic ACE2 regulation in responders. Conclusions Intestinal inflammation alters SARS-CoV-2 coreceptors in the intestine, with opposing dysregulations in ileum and colon. HNF4A , an IBD susceptibility gene, seems an important upstream regulator of ACE2 in ileum, whereas interferon signalling might dominate in colon. [ABSTRACT FROM AUTHOR]

Background and Aims: During early phases of inflammation, activated neutrophils extrude neutrophil extracellular traps (NETs) in a PAD4-dependent manner, aggravating tissue injury and remodelling. In this study, we investigated the potential pro-fibrotic properties and signalling of NETs in Crohn's disease (CD)., Methods: NETs and activated fibroblasts were labelled on resected ileum from CD patients by multiplex immunofluorescence staining. NETs-treated human primary intestinal fibroblasts were analysed by bulk RNA-sequencing to uncover cell signalling pathways, and by high-throughput imaging to assess collagen production and migratory activity. Consequentially, TLR2/NF-kB pathway was evaluated by transfection of CCD-18Co fibroblasts with NF-kB-luciferase reporter plasmid, incorporating C29 to block TLR2 signalling. A chronic DSS mouse model was used to define the specific role of PAD4 deletion in neutrophils (MRP8-Cre, Pad4fl/fl)., Results: Immunofluorescence showed spatial co-localisation of NETs and activated fibroblasts in ileal ulcerations of CD patients. Transcriptomic analysis revealed upregulation of pro-fibrotic genes and activation of TLR-signalling pathways in NETs-treated fibroblasts. NETs treatment induced fibroblast proliferation, diminished migratory capability, and increased collagen release. Transfection experiments indicated a substantial increase in NF-kB expression with NETs, whereas C29 led to decreased expression and release of collagen. In line, a significantly reduction in collagen content was observed in the colon of MRP8-Cre, Pad4fl/fl mice subjected to chronic DSS colitis., Conclusions: NETs potentially serve as an initial stimulus for pathological activation of fibroblasts within the intestine via the TLR2/NF-kB pathway. Given their early involvement in inflammation, inhibition of PAD4 might offer a strategy to modulate both inflammation and fibrogenesis in CD., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Enteric glia have been recently recognized as key components of the colonic tumor microenvironment indicating their potential role in colorectal cancer pathogenesis. Although enteric glia modulate immune responses in other intestinal diseases, their interaction with the colorectal cancer immune cell compartment remains unclear. Through a combination of single-cell and bulk RNA-sequencing, both in murine models and patients, here we find that enteric glia acquire an immunomodulatory phenotype by bi-directional communication with tumor-infiltrating monocytes. The latter direct a reactive enteric glial cell phenotypic and functional switch via glial IL-1R signaling. In turn, tumor glia promote monocyte differentiation towards pro-tumorigenic SPP1 + tumor-associated macrophages by IL-6 release. Enteric glia cell abundancy correlates with worse disease outcomes in preclinical models and colorectal cancer patients. Thereby, our study reveals a neuroimmune interaction between enteric glia and tumor-associated macrophages in the colorectal tumor microenvironment, providing insights into colorectal cancer pathogenesis., (© 2024. The Author(s).)