REGγ Links Inflammation to Fibrosis in Post-Necrotizing Enterocolitis Intestinal Strictures by Activating Transforming Growth Factor-β/Smad3 Signaling.

Intestinal stricture affects 2.9% to 57% of necrotizing enterocolitis (NEC) cases, primarily involving the terminal ileum and colon. Although inflammation-driven fibrosis underlies stricture development, key molecular mechanisms remain unclear. Up-regulation of REGγ was previously observed in human NEC specimens and murine models, correlating with inflammation severity. Here, elevated REGγ in human strictures correlated with fibrotic severity. Single-cell RNA sequencing and immunofluorescence confirmed REGγ enrichment in fibroblasts. In vitro, REGγ silencing suppressed transforming growth factor-β1- or tumor necrosis factor (TNF)-α-induced fibroblast activation, proliferation, and migration, accompanied by reduced Smad3 phosphorylation and nuclear translocation. Mechanistically, TNF-α enhanced REGγ transcription via NF-κB p65 binding to its promoter. NF-κB inhibition attenuated TNF-α-induced fibrotic responses, rescued by REGγ overexpression. In murine fibrosis models, REGγ deficiency reduced inflammation, collagen deposition, and phosphorylated Smad3. These findings establish REGγ as a key mediator of inflammation-fibrosis crosstalk in post-NEC intestinal strictures and a promising therapeutic target.