Knockout of microRNA-21 reduces biliary hyperplasia and liver fibrosis in cholestatic bile duct ligated mice

Cholestasis is a condition that leads to chronic hepatobiliary inflammation, fibrosis, and eventually cirrhosis. Many microRNAs (miRs) are known to play a role in fibrosis progression; however, the role of miR-21 during cholestasis remains unknown. Therefore, the aim of this study was to elucidate the role of miR-21 during cholestasis-induced biliary hyperplasia and hepatic fibrosis. Wild-type (WT) and miR21(−/−) mice underwent sham or bile duct ligation (BDL) for 1 wk, before evaluating liver histology, biliary proliferation, hepatic stellate cell (HSC) activation, fibrotic response, and Smad-7 expression. In vitro, immortalized murine biliary cell lines (IMCL) and human hepatic stellate cell line (hHSC) were treated with either miR-21 inhibitor or control before analyzing proliferation, apoptosis, and fibrotic responses. In vivo, the levels of miR-21 were increased in total liver and cholangiocytes after BDL, and loss of miR-21 decreased the amount of BDL-induced biliary proliferation and intrahepatic biliary mass. Also, loss of miR-21 decreased BDL-induced HSC activation, collagen deposition, and expression of the fibrotic markers TGF-β1 and α-SMA. In vitro, IMCL and hHSCs treated with miR-21 inhibitor displayed decreased proliferation and expression of fibrotic markers and enhanced apoptosis when compared to control treated cells. Furthermore, mice lacking miR-21 show increased Smad-7 expression, which may be driving the decrease in biliary hyperplasia and hepatic fibrosis. During cholestatic injury miR-21 is increased and leads to increased biliary proliferation and hepatic fibrosis. Local modulation of miR-21 may be a therapeutic option for patients with cholestasis.