Role Of Wnt/β-catenin Signaling Pathway In The Development Of Liver Fibrosis

Background The activation of HSCs (Hepatic stellate cell) induced by TGF-β1(transforming growth factor-betal) plays a central role in the process of hepatic fibrosis.Due to various stimuli (hepatic virus, alcohol many antigens and so on), The activatedTGF-β1/Smad3 signaling pathway promotes the activation of HSCs leading to an excessiveaccumulation of ECM in liver. Therefore, the blockage of TGF-β1/Smad3 signalingpathway is the hotpot of antifibrosis research. Due to the unsatisfying curative effects ofvarious anti- TGF-β1 agents, Scientists have not found the key protein in the mechanism ofhepatic fibrosis induced by TGF-β1/Smad3.Wnt/β-catenin is a signaling pathway regulatingmany cellular physiological functions including cell proliferation, cell survival and necrosiswhich is known to play important roles in the development of hepatic-embryo and hepaticstem cells. In resent years, an increasing number of research has proved the key rolesβ-catenin played in the development of organ fibrosis and the TGF-β/Smad3 signaling pathway.However, there is little known about the role ofβ-catenin in the process of HSCs activation and hepaticfibrosis induced by TGF-β/Smad3 signaling pathway.Objective To investigate the role of Wnt/β-catein signaling pathway in the process of hepaticfibrosis and elucidate the mechanism involved in the development of hepatic fibrosis induced byWnt/β-catenin signaling pathway through clarifying the effect of Wnt/β-catein signaling pathway on theTGF-β/Smad3 induced HSCs activation.Methods the expression ofβ-catenin protein in liver tissue was detected byimmunochemistry assay. The levels of cytokines in the serum of rats were measured byELISA kits. The levels ofβ-catenin and a-SMA mRNA and protein in activated HSCsinduced by TGF-β1 at different time were analyzed by PCR and western-blottingrespectively. Plasmids of pcDNA3.1-β-catenin and pEGFP-N1 were co-transfected intoHSC-T6 cells using liposome. Cell viability was measured by 96-wells assay and the levels of β-catenin and a-SMA mRNA and protein in activated HSCs induced by TGF-β1 at differenttime were analyzed by PCR and western-blotting respectively.Results the levels ofβ-catenin protein in fibrotic livers were significantly higher than innormal control rats and they had a strong positive correlation with the degree of hepaticfibrosis. TGF-β1 could upregulate the expression ofβ-catenin in HSC-T6 cells togetherwith the viability of HSCs-T6 cells. The increased activation of HSCs-T6 cells transfectedwithβ-catenin. gene was accompanied by markedly higher levels of smad3 and a-SMAmRNA and protein than those in the cells of control groups.Conclusions The activation of Wnt/β-catenin signaling pathway is closely related to theprocess of hepatic fibrosis and it plays an important role in the development of hepaticfibrosis induced by TGF-β1 through increasing the activation of HSCs-T6 cells induced byTGF-β1 and up-regulating the expression of smads. Therefore, we presume thatβ-cateninprobably plays downstream in the TGF-β1 signaling pathway.