Abstract: Objective To investigate the mechanism by which fibroblasts with high WNT2b expression causes intestinal mucosa barrier disruption and promote the progression of inflammatory bowel disease (IBD). Methods Caco-2 cells were treated with 20% fibroblast conditioned medium or co-cultured with fibroblasts highly expressing WNT2b, with the cells without treatment with the conditioned medium and cells co-cultured with wild- type fibroblasts as the control groups. The changes in barrier permeability of Caco-2 cells were assessed by measuring transmembrane resistance and Lucifer Yellow permeability. In Caco-2 cells co-cultured with WNT2b-overexpressing or control intestinal fibroblasts, nuclear entry of β-catenin was detected with immunofluorescence assay, and the expressions of tight junction proteins ZO-1 and E- cadherin were detected with Western blotting. In a C57 mouse model of dextran sulfate sodium (DSS)-induced IBD-like enteritis, the therapeutic effect of intraperitoneal injection of salinomycin (5 mg/kg, an inhibitor of WNT/β-catenin signaling pathway) was evaluated by observing the changes in intestinal inflammation and detecting the expressions of tight junction proteins. Results In the co-culture system, WNT2b overexpression in the fibroblasts significantly promoted nuclear entry of β-catenin (P<0.01) and decreased the expressions of tight junction proteins in Caco-2 cells; knockdown of FZD4 expression in Caco-2 cells obviously reversed this effect. In DSS- treated mice, salinomycin treatment significantly reduced intestinal inflammation and increased the expressions of tight junction proteins in the intestinal mucosa. Conclusion Intestinal fibroblasts overexpressing WNT2b causes impairment of intestinal mucosal barrier function and can be a potential target for treatment of IBD.

Key words: inflammatory bowel disease; fibroblasts; WNT2b; WNT/β-catenin signaling pathway