Mast Cells Inhibit Stem Cell-driven Epithelial Repair in Inflammatory Bowel Disease via Suppressing Wnt/lrp6/β-Catenin Signaling Pathway.

BACKGROUND & AIMS: Mast cells (MCs) play a critical role in the pathogenesis of inflammatory bowel diseases (IBD), encompassing ulcerative colitis and Crohn's disease. Nevertheless, their regulatory impact on intestine stem cells (ISCs) compartment remains poorly characterized. We aim to study the effect of MCs on ISC-mediated epithelial regeneration in IBD. METHODS: The bulk RNA sequencing data of intestine tissues from patients with IBD were collected from the Mount Sinai Crohn's and Colitis Registry to explore the direct and indirect correlation of MCs with ISCs, stemness, and related pathways. Subsequently, the results were verified by experiments such as dextran sulfate sodium (DSS)-induced colitis in MC-deficient rats and C57BL/6 mice, and co-culture of bone marrow-derived mast cells and small intestinal organoids. RESULTS: Bulk RNA sequencing data analysis demonstrated significant MC activation in inflamed mucosa of patients with IBD, showing negative correlations with transcriptional signatures of ISC, stemness markers, and Wnt pathway activity. Genetic ablation of MCs in rats conferred protection against DSS-induced epithelial damage, exhibiting enhanced Lgr5 expression and Wnt/lrp6/β-catenin signaling activation compared with wild-type rats. Pharmacological stabilization of MCs with cromolyn sodium or intervention with a carboxypeptidase A inhibitor during the recovery phase of DSS-induced colitis promoted epithelial restoration in mice, evidenced by improved crypt architecture and upregulation of ISC-associated genes and proteins. In vitro co-culture experiments demonstrated MC-mediated suppression of intestinal organoid growth and Wnt/lrp6/β-catenin signaling pathway, reversible through Lrp6 activation and carboxypeptidase A3 inhibition. Mediation analysis coupled with neutrophils detection revealed an additional indirect regulatory axis involving MC-driven neutrophil recruitment to inhibit ISC-mediated epithelial repair. CONCLUSIONS: Our findings establish that MCs play a pivotal role in inhibiting ISC-mediated epithelial regeneration by suppressing Wnt/lrp6/β-catenin pathway in IBD, directly through carboxypeptidase A3 secretion and indirectly through neutrophils recruitment.