R-Spondin2 Activates Hepatic Stellate Cells and Promotes Liver Fibrosis

The development of liver fibrosis is the fundamental stage toward a number of mortal complications of liver diseases, including cirrhosis and hepatocellular carcinoma. Canonical Wnt pathway is crucial in diverse biological processes and mediates the progression and regression of liver fibrosis. As a potent Wnt pathway agonist, the role of roof plate-specific spondin-2 (R-Spondin2) in the hepatic fibrosis has not been well elucidated. The purpose of this study was to investigate whether R-Spondin2 contributes to hepatic stellate cells (HSCs) activation, the key event in liver fibrogenesis. Human liver tissues, hepatic fibrosis mouse model, and freshly isolated mice HSCs were used. Protein expression and transcriptional level were analyzed by Western-blot assays and real-time PCR, respectively. Exogenous stimulation with recombinant R-Spondin2 and knockdown of R-Spondin2 were performed to investigate functionality. Nuclear beta-catenin level and T cell-specific transcription factors activity were analyzed, and HSC proliferation was tested by MTT assay. Overexpression of R-Spondin2 was observed in both human fibrotic liver tissues and hepatic fibrosis mouse model. Exogenous stimulation with R-Spondin2 in the freshly isolated mice HSCs induced a dose-dependent increase in Wnt pathway activities, HSC proliferation, and the expression of alpha-smooth muscle actin (alpha-SMA) and Collagen I. Additionally, Wnt pathway activities, HSC proliferation, and the expressions of alpha-SMA and Collagen I decreased in the R-Spondin2 knockdown HSCs. These findings suggest that R-Spondin2 may promote HSC activation by enhancing the canonical Wnt pathway.