Abstract: Objective The purpose of this experiment was to explore the roles of microRNA(miR)-122 in the pathogenesis of liver fibrosis by in vitro and by in vivo. Methods The liver fibrosis model was established in C57BL/6 mice by intraperitoneal injection of carbon tetrachloride and also in HSC-T6 cells in vitro by incubation with 10 ng/ml transforming growth factor-β1 (TGF-β1). The miR-122 agomir and miR-122 mimics were transfected to overexpress miR-122 in mice and in hepatic stellate cells. The total RNA and whole protein were extracted for RT-PCR and Western-blot detection of miR-122, α-smooth muscle actin (α-SMA), type I collagen (Collagen Ⅰ), tissue inhibitor of metalloproteinase 1 (TIMP-1), and platelet-derived growth factor (PDGF). The proliferation of HSC-T6 cells was detected by CCK-8. Results The expression of α-SMA in the liver tissue in the model animal was significantly higher than that in the control group (9.92±2.12 vs. 1.12±0.54, P<0.01), while the miR-122 level was significantly lower than that in the control group (0.95±0.31 vs. 2.07±0.28, P<0.01); in mice with carbon tetrachloride-induced liver fibrosis, the miR-122 level in the miR-122 agomir-transfected group was significantly higher than that in the miR-122 agomir control-transfected group (6.27±1.73 vs. 2.78±0.21, P < 0.01); the α-SMA, type I collagen, TIMP-1 and PDGF protein expression in the miR-122 agomir-transfected group were significantly decreased; in TGF-β1-intervened HST-T6 cells, the α-SMA expression increased as the prolongation of TGF-β1 treatment (0h:0.61±0.02, 12 h:0.69±0.05, 24 h:0.75±0.01, 48 h:1.01±0.03, P＜0.05), while the miR-122 levels decreased (0 h:0.72±0.05, 12 h:0.45±0.01, 24 h:0.37±0.03, 48 h:0.29±0.08, P＜0.05); the miR-122 level in the miR-122 mimics-transfected cells greatly increased as compared with the miR-122 negative control-transfected cells (178.45±30.62 vs. 12.18±2.39, P＜0.01); the Western blot showed that the expression of α-SMA protein was significantly down-regulated in the miR-122 mimics-transfected group; in TGF-β1-intervened HST-T6 cells, the proliferation activity greatly decreased in the miR-122 mimics-transfected group as compared to that in miR-122 negative control-transfected group (P＜0.05). Conclusion The miR-122 levels down-regulate in liver fibrosis, and overexpression of it might inhibit the activation and proliferation of hepatic stellate cells, and probably inhibit the occurrence and development of liver fibrosis.

Key words: Liver fibrosis, HSC-T6 cells, MicroRNA-122, Tissue inhibitor of metalloproteinase 1, Platelet-derived growth factor, Mice