Non-TGFβ profibrotic signaling in ulcerative colitis after in vivo experimental intestinal injury in humans

Although impaired regeneration is important in many gastrointestinal diseases including ulcerative colitis (UC), the dynamics of mucosal regeneration in humans are poorly investigated. We have developed a model to study these processes in vivo in humans. Epithelial restitution (ER) and extracellular matrix (ECM) regulation after an experimental injury of the sigmoid colonic mucosa was assessed by repeated high-resolution endoscopic imaging, histological assessment, RNA sequencing, deconvolution analysis, and 16S rDNA sequencing of the injury niche microbiome of 19 patients with UC in remission and 20 control subjects. Human ER had a 48-h lag before induction of regenerative epithelial cells [wound-associated epithelial (WAE) and transit amplifying (TA) cells] along with the increase of fibroblast-derived stem cell growth factor gremlin 1 mRNA (GREM1). However, UC deconvolution data showed rapid induction of inflammatory fibroblasts and upregulation of major structural ECM collagen mRNAs along with tissue inhibitor of metalloproteinase 1 (TIMP1), suggesting increased profibrotic ECM deposition. No change was seen in transforming growth factor β (TGFβ) mRNA, whereas the profibrotic cytokines interleukin 13 (IL13) and IL11 were upregulated in UC, suggesting that human postinjury responses could be TGFβ-independent. In conclusion, we found distinct regulatory layers of regeneration in the normal human colon and a potential targetable profibrotic dysregulation in UC that could lead to long-term end-organ failure, i.e., intestinal damage.NEW & NOTEWORTHY The study reveals the regulatory dynamics of epithelial regeneration and extracellular matrix remodeling after experimental injury of the human colon in vivo and shows that human intestinal regeneration is different from data obtained from animals. A lag phase in epithelial restitution is associated with induction of stromal cell-derived epithelial growth factors. Postinjury regeneration is transforming growth factor β-independent, and we find a profibrotic response in patients with ulcerative colitis despite being in remission.