Exosome Derived from Palmitic Acid-treated Hepatocytes Activates Hepatic Stellate Cells

Abstract

Background/Aim: Although nonalcoholic fatty liver disease (NAFLD) is becoming dominant cause of chronic liver disease, the exact mechanism of progression from simple steatosis to nonalcoholic steatohepatitis (NASH) have yet to be elucidated. We aimed to investigate the role of exosome from lipid laden hepatocyte in the context of NAFLD progression in vitro.

Methods: We isolated exosome from human hepatoma cell lines (Huh7 or HepG2) treated with palmitic acid (PA). Concentration of exosome was determined with exosome quantitation assay kit and microarray was done for miRNA analysis in exosome. LX-2 cells, human hepatic stellate cell (HSC) line, were treated with isolated exosome from PA treated cells.

Results: Compare with controls, PA-treated hepatocytes significantly increased CD36 and exosome production. (8.6 vs. 5.5 X 10^7 /μL, p <0.01). Microarray showed distinct expression level of microRNA between exosome from control hepatocytes and exosome from PA-treated hepatocytes (Figure). When LX-2 cells were cultured with exosome from hepatocytes, TGF-beta1, alpha-SMA, and Col1a1 expression in LX-2 cells were significantly increased compared to control. Moreover, exosome from PA-treated hepatocytes more increased the expression levels of fibrosis markers. High concentration of exosome (100 μg/mL) more increased the expression levels of fibrosis markers compared to low concentration of exosome (50 μg/mL).

Conclusions: Palmitic acid treatment enhanced the production of exosome in hepatocytes and changed miRNA components in exosome. Exosomes derived from palmitic acid-treated hepatocytes increased expression levels of fibrotic genes in HSCs.Therefore, exosome might have important roles for crosstalk between hepatocytes and HSCs in the progression to NASH from simple steatosis.