PS 1-7 : Exosomal miRNA Regulates Liver Fibrosis during Progres-sion of Nonalcoholic Fatty Liver Disease

Aims: Although nonalcoholic fatty liver disease (NAFLD) is becoming dominant cause of chronic liver disease, the exact mechanism of fibrosis progression in NAFLD have yet to be elucidated. We aimed to investigate the role of exosomal miRNA during fibrosis progression in NAFLD. Methods: We isolated exosomes from supernatant of human hepatoma cell line (Huh7) with or without palmitic acid treatment. Exosomal miRNA profiles were analyzed using a microarray. LX-2 cells, human hepatic stellate cell (HSC) line, were treated with isolated exosome or were transfected with miRNA. Collected LX-2 cells were subjected to real-time PCR for evaluation of fibrosis marker. In addition, we analyzed miRNA expression in exosomes from the sera in biopsy proven NAFLD patients. Results: Compared with controls, PA-treated hepatocytes displayed significantly increased exosome production (8.6 vs. 5.5 X 10^7 /μL, P < 0.001). The microarray data showed distinctive expression levels of miRNA between exosomes from vehicle- and PA-treated hepatocytes. In exosomes from PA-treated hepatocyte, the expression of miRNA 122 and 192 were significantly increased compared with controls. When LX-2 cells were cultured with exosomes from PA-treated hepatocytes, expression of fibrosis markers (TGF-β 1, α-SMA, and Col1a1) in LX-2 cells increased compared to those from vehicle-treated hepatocytes. When we transfected HSCs with miRNA 192, it showed enhanced expression of fibrosis markers comparing with negative control. In accordance with in vitro, the number of exosomes significantly increased in sera from advanced stage NAFLD patients compared to early stage NAFLD patients (21.73 vs. 9.75 X 107/μL, P < 0.001). Also, miRNA 122 and 192 expression were significantly increased in sera from advanced stage NAFLD patients compared to early stage NAFLD patients (21.73 vs. 9.75 X 107/μl, P < 0.001). Conclusions: PA treatment accelerated the production of exosomes in hepatocytes and altered their miRNA profile. Advanced stage NAFLD patients showed distinct number of exosomes and expression of miRNA in exosomes from sera compared to early stage NAFLD patients. Direct transfection of miRNA 192 into HSCs increased the expression of fibrosis marker genes in HSCs. Therefore, exosomes and exosomal miRNA might have important roles for crosstalk between hepatocytes and HSCs in the fibrosis progression in NAFLD.