β-catenin is a central mediator of pro-fibrotic Wnt signaling in systemic sclerosis

Objectives Pathologic fibroblast activation drives fibrosis of the skin and internal organs in patients with systemic sclerosis (SSc). β-catenin is an integral part of adherens junctions and a central component of canonical Wnt signaling. Here, the authors addressed the role of β-catenin in fibroblasts for the development of SSc dermal fibrosis. Methods Nuclear accumulation of β-catenin in fibroblasts was assessed by triple staining for β-catenin, prolyl-4-hydroxylase-β and 4′,6-diamidino-2-phenylindole (DAPI). The expression of Wnt proteins in the skin was analysed by real-time PCR and immunohistochemistry. Mice with fibroblast-specific stabilisation or fibroblast-specific depletion were used to evaluate the role of β-catenin in fibrosis. Results The auhors found significantly increased nuclear levels of β-catenin in fibroblasts in SSc skin compared to fibroblasts in the skin of healthy individuals. The accumulation of β-catenin resulted from increased expression of Wnt-1 and Wnt-10b in SSc. The authors further showed that the nuclear accumulation of β-catenin has direct implications for the development of fibrosis: Mice with fibroblast-specific stabilisation of β-catenin rapidly developed fibrosis within 2 weeks with dermal thickening, accumulation of collagen and differentiation of resting fibroblasts into myofibroblasts. By contrast, fibroblast-specific deletion of β-catenin significantly reduced bleomycin-induced dermal fibrosis. Conclusions The present study findings identify β-catenin as a key player of fibroblast activation and tissue fibrosis in SSc. Although further translational studies are necessary to test the efficacy and tolerability of β-catenin/Wnt inhibition in SSc, the present findings may have clinical implications, because selective inhibitors of β-catenin/Wnt signaling have recently entered clinical trials.