Extracellular vesicles originating from steatotic hepatocytes promote hepatic stellate cell senescence via AKT/mTOR signaling

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing rapidly due to the obesity epidemic. In the inflammatory stages of MASLD (MASH), activation of hepatic stellate cells (HSCs) leads to initiation and progression of liver fibrosis. Extracellular vesicles (EVs) are released from all cell types and play an important role in intercellular communication. However, the role of EVs released from hepatocytes in the context of MASLD is largely unknown. Therefore, the present study aimed to investigate the role of EVs derived from both normal and steatotic (free fatty acid-treated) hepatocytes on the phenotype of HSCs via the senescence pathway. Primary rat hepatocytes were treated with free fatty acids (FFAs: oleic acid and palmitic acid). EVs were collected by ultracentrifugation. EVs markers and HSCs activation and senescence markers were assessed by Western blot analysis, qPCR and cytochemistry. Reactive oxygen species (ROS) production was assessed by fluorescence assay. RNA profiles of EVs were evaluated by sequencing. We found that EVs from hepatocytes treated with FFAs (FFA-EVs) inhibit collagen type 1 and α-smooth muscle actin expression, increase the production of ROS and the expression of senescence markers (IL-6, IL-1β, p21 and senescence-associated β-galactosidase activity) in early activating HSCs via the AKT-mTOR pathway. Sequencing showed differentially enriched RNA species between the EVs groups. In conclusion, EVs from FFA-treated hepatocytes inhibit HSC activation by inducing senescence via the AKT-mTOR signaling pathway. Determining the components in EVs from steatotic hepatocytes that induce HSC senescence may lead to the identification of novel targets for intervention in the treatment of MASLD in the future.