GSK-3β suppresses the proliferation of rat hepatic oval cells through modulating Wnt/β-catenin signaling pathway

Aim: Glycogen synthase kinase 3 beta (GSK-3 beta) plays a crucial role in hepatic biology, including liver development, regeneration, proliferation and carcinogenesis. In this study we investigated the role of GSK-3 beta in regulation of growth of hepatic oval cells in vitro and in liver regeneration in partially hepatectomized rats. Methods: WB-F344 cells, the rat hepatic stem-like epithelial cells, were used as representative of oval cells. Cell viability was examined using a WST-8 assay. The cells were transfected with a recombinant lentivirus expressing siRNA against GSK-3 beta (GSK3-beta RNAiLV) or a lentivirus that overexpressed GSK-3 beta (GC-GSK-3 beta LV). Adult rats underwent partial (70%) hepatectomy, and liver weight and femur length were measured at d 7 after the surgery. The expression of GSK-3 beta, phospho-Ser9-GSK-3 beta, beta-catenin and cyclin D1 was examined with immunoblotting assays or immunohistochemistry. Results: Treatment of WB-F344 cells with the GSK-3 beta inhibitor SB216763 (5 and 10 mu mol/L) dose-dependently increased the levels of phospho-Ser9-GSK-3 beta, but not the levels of total GSK-3 beta, and promoted the cell proliferation. Knockout of GSK-3 beta with GSK-3 beta RNAiLV increased the cell proliferation, whereas overexpression of GSK-3 beta with GC-GSK-3 beta LV decreased the proliferation. Both SB216763 and GSK-3 beta RNAiLV significantly increased the levels of beta-catenin and cyclin D1 in the cells, whereas GSK-3 beta overexpression decreased their levels. In rats with a partial hepatectomy, administration of SB216763 (2 mg/kg, ip) significantly increased the number of oval cells, the levels of phospho-Ser9-GSK-3 beta, beta-catenin and cyclin D1 in liver, as well as the ratio of liver weight to femur length at d 7 after the surgery. Conclusion: GSK-3 beta suppresses the proliferation of hepatic oval cells by modulating the Wnt/beta-catenin signaling pathway.