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  • Title: The Epigenetically-Regulated microRNA-378a Targets TGF-β2 in TGF-β1-Treated Hepatic Stellate Cells.
    Author: Yu F, Yang J, Huang K, Pan X, Chen B, Dong P, Zheng J.
    Journal: Cell Physiol Biochem; 2016; 40(1-2):183-194. PubMed ID: 27855367.
    Abstract:
    BACKGROUND/AIMS: In liver fibrosis, the activation of hepatic stellate cells (HSCs) is considered as a pivotal event. It is well known that transforming growth factor-β1 (TGF-β1) is the main stimuli factor responsible for HSC activation. microRNAs (miRNAs), regulating various biological processes, have recently been shown to be involved in HSC activation. A recent study reported that deficiency of miR-378a contributes to cardiac fibrosis via TGF-β1-dependent paracrine mechanism. However, the involvement of miR-378a and its roles in TGF-β1-induced HSC activation remains largely unknown. METHODS: miR-378a expression was detected in TGF-β1-treated cells and patients with cirrhosis. Then, effects of miR-378a overexpression on cell proliferation and HSC activation were analyzed. We also analyzed the binding of miR-378a to the 3'-untranslated region of TGF-β2. RESULTS: In response to TGF-β1, miR-378a expression was down-regulated in a dose-dependent manner. miR-378a overexpression suppressed both cell proliferation and cell cycle in TGF-β1-treated LX-2 cells. Moreover, miR-378a overexpression inhibited TGF-β1-induced HSC activation including the reduction of α-smooth muscle actin (α-SMA) and type I collagen. Similarly, miR-378a resulted in a reduction in cell proliferation, and the expressions of α-SMA and Col1A1 in TGF-β1-treated primary HSCs. Notably, TGF-β2 was confirmed as a target of miR-378a by luciferase reporter assays. Interestingly, miR-378a promoter methylation may be responsible for miR-378a down-regulation in TGF-β1-treated LX-2 cells and TGF-β1-treated primary HSCs. Further studies confirmed that reduced miR-378a was associated with promoter methylation in patients with cirrhosis compared with healthy controls. CONCLUSION: Our results demonstrate that miR-378a expression is associated with its methylation status in TGF-β1-treated cells, and epigenetically-regulated miR-378a inhibits TGF-β1-induced HSC activation, at least in part, via TGF-β2.
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