Regulation of hepatic stellate cell contraction and cirrhotic portal hypertension by Wnt/β-catenin signalling via interaction with Gli1.

Background and purpose Portal hypertension is a lethal complication of cirrhosis. Its mechanism and therapeutic targets remain largely unknown. Hepatic stellate cell (HSC) contraction increases intrahepatic vascular resistance contributing to portal hypertension. We investigated how HSC contraction was regulated by Wnt signaling and the therapeutic implication. Experimental approach Liver tissues from cirrhotic patients were examined. Cirrhotic mice with genetic or pharmacological treatments were used for in vivo assessments and their primary cells were isolated. Cellular functions and signaling pathways were analyzed in human HSC-LX2 cells using real-time PCR, Western blotting, siRNA, luciferase reporter assay, chromatin immunoprecipitation, co-immunoprecipitation, and site-directed mutagenesis. Key results Wnt/β-catenin correlated with HSC contraction in human cirrhotic liver. Wnt3a stimulated Smo-independent Gli1 nuclear translocation followed by LARG-mediated RhoA activation leading to HSC contraction. Sufu negatively mediated Wnt3a-induced Gli1 nuclear translocation. Wnt/β-catenin repressed the transcription of Sufu dependent on β-catenin/TCF4 interaction and TCF4 binding to Sufu promoter. Molecular simulation and site-directed mutagenesis identified the β-catenin residues Lys312 and Lys435 critically involved in the interaction. Additionally, TCF4 binding to the sequence CACACCTTCC at Sufu promoter was required for transrepression of Sufu. In cirrhotic mice, short-term liver-targeting β-catenin deficiency or acute treatment with β-catenin inhibitors reduced portal pressure via restriction of HSC contraction rather than inhibition of HSC activation. Long-term deficiency or treatments also ameliorated liver injury, fibrosis and inflammation. Conclusions and implications Interaction between Wnt/β-catenin and Smo-independent Gli1 pathways promoted HSC contraction via TCF4-dependent transrepression of Sufu. HSC-specific inhibition of β-catenin may have therapeutic benefits for cirrhotic portal hypertension.