CADHERIN-11, AN ESSENTIAL REGULATOR OF CELL-CELL ADHESION UPREGULATED IN IBD PATIENTS, PLAYS ESSENTIAL ROLES IN PROMOTING FIBROBLAST ACTIVATION AND DEVELOPMENT OF INTESTINAL INFLAMMATION AND FIBROSIS

Background Intestinal fibrosis is a severe complication of inflammatory bowel diseases (IBD) leading to intestinal strictures and need for surgery. No effective anti-fibrotic therapy is available. Cadherin-11 (Cad-11) is an adherens junction protein, which is upregulated in rheumatoid arthritis (RA), idiopathic pulmonary fibrosis (IPF) and skin fibrosis. Inhibition of cadherin-11 has shown beneficial effects in RA and IPF animal models. A phase II clinical trial of cadherin-11 inhibition in RA has shown a good safety profile. Our aim was to evaluate the expression levels and function of Cad-11 in IBD patients using intestinal tissues, primary human intestinal cells, and the murine dextran sulfate sodium (DSS)-induced chronic colitis model. Methods IBD (Crohn’s disease (CD) n=20; Ulcerative colitis (UC) (n=10) and control (n=10) full thickness resected intestinal tissues were procured from adults in accordance with IRB approval. Protein and mRNA were extracted for western blot (WB) and quantitative polymerase chain reaction (qPCR). Distribution of Cad-11 was evaluated by immunofluorescence (IF) and RNA hybridization in frozen and formalin-fixed paraffin-embedded (FFPE) tissue sections, respectively. Primary human intestinal myofibroblasts (HIMF) were used in functional experiments. Recombinant human Fc and Cad-11 extracellular domain (hCAD-11-Fc) was used as activator and siRNA as inhibitor of Cad-11 in HIMF. Murine chronic colitis was induced in wildtype BALB/c mice and cadherin-11 knockout mice by DSS. Anti-Cad-11 monoclonal antibody (H1M1) was used for the treatment of BALB/c mouse colitis. Results Increased gene and protein expression levels of Cad-11 were found in intestinal full thickness IBD tissue compared to controls (45-fold, p<0.01). Cad-11 colocalized with alpha smooth muscle actin (α-SMA) (Figure 1), indicating that Cad-11 is selectively expressed in intestinal myofibroblasts and smooth muscle cells. Among all the primary human intestinal cells, Cad-11 was expressed exclusively in HIMF and HIMC cells. Level of Cad-11 was increased in IBD HIMFs compared to non-IBD controls, and increased upon stimulation with TNF-α, IL-1β, b-FGF and TGF-β (all p<0.01). Knocking down Cad-11 with siRNA decreased FN expression, while hCAD-11-Fc increased the expression FN in a dose- and time-dependent manner as well as the proliferation of HIMF. Upon treatment with H1M1 antibody, DSS-treated mice showed lower clinical scores and weight loss compared to control mice (p<0.001. Figure 2), as well as less FN expression (p<0.001). Cadherin-11 knockout mice also showed lower clinical scores and weight loss compared to wild type mice (p<0.001). Conclusions Cad-11 expression is increased in CD stricture tissues and its blockade reduces profibrotic effects in HIMF in vitro. Inhibition of Cad-11 in vivo reduces clinical severity and fibrosis of experimental colitis.