Exosomal Transmission of MicroRNA from HCV Replicating Cells Stimulates Transdifferentiation in Hepatic Stellate Cells

The mechanism by which hepatitis C virus (HCV) causes fibrosis and other chronic liver diseases remains poorly understood. Previously, we observed that HCV infection induces microRNA-192 (miR-192) expression, which in turn upregulates transforming growth factor β1 (TGF-β1) in hepatocytes. In this study, we aimed to determine the roles and mechanisms of HCV-induced miR-192 expression during chronic liver injury and fibrosis and to identify potential target of the liver disease. Noticeably, miR-192 is secreted and transmitted through exosomes from HCV-replicating hepatocytes into hepatic stellate cells (HSCs). Exosomal transferred miR-192 upregulated fibrogenic markers in HSCs through TGF-β1 upregulation, resulting in the activation and transdifferentiation of HSCs into myofibroblasts. Anti-miR-192 treatment of HCV-replicating hepatocytes efficiently reduced miR-192 levels in exosomes, downregulated miR-192 and fibrogenic marker levels in HSCs, and impeded transdifferentiation of the cells. In contrast, miR-192 mimic RNA treatment significantly increased miR-192 levels in exosomes from naive hepatocytes, increased miR-192 and fibrogenic marker expression in HSCs, and induced transdifferentiation of the cells. Notably, transdifferentiation of exosome-exposed HSCs was reversed following treatment with anti-miR-192 into the HSCs. This study revealed a novel mechanism of HCV-induced liver fibrosis and identified exosomal miR-192 as a major regulator and potential treatment target for HCV-mediated hepatic fibrosis.