Hepatocyte exosomal miR-21-5p activates hepatic stellate cells and exacerbates liver fibrosis via targeting Smad7
Aims This study investigated the impact of hepatocyte exosomes on hepatic stellate cell (HSC) activation and their potential role in liver fibrosis while elucidating the underlying molecular mechanisms. Methods L02 exosomes were extracted, and their influence on LX-2 activation was preliminarily investigated. A mouse liver fibrosis model was established through intraperitoneal injection of 20% carbon tetrachloride (CCl4). Normal and fibrotic hepatocyte exosomes were separately collected to explore their distinct effects on HSC activation. High-throughput sequencing identified differential miRNAs in exosomes from normal and fibrotic hepatocytes. MiR-21-5p, displaying the most substantial expression difference, was selected to assess the correlation between serum exosomal miR-21-5p and liver fibrosis. The target gene of miR-21-5p was validated using a dual luciferase assay. LX-2 cells were transfected with miR-21-5p mimics and inhibitors to clarify the impact and mechanisms of miR-21-5p on HSC activation, proliferation, and collagen synthesis. Results Normal L02 exosomes were internalized by LX-2 cells and inhibited their activation. In comparison to normal hepatocyte exosomes, fibrotic hepatocyte exosomes induced HSC activation. High-throughput sequencing revealed 32 upregulated and 6 downregulated miRNAs in fibrotic hepatocyte exosomes, with the most significant increase observed in miR-21-5p. Serum exosomal miR-21-5p displayed a close association with liver fibrosis. Dual luciferase assays and cell transfection experiments confirmed that miR-21-5p promoted HSC activation, proliferation, and collagen synthesis by targeting Smad7. Conclusion Fibrotic hepatocyte exosomes may trigger HSCs activation through exosomal transfer in liver fibrosis. Exosomal miR-21-5p enhances HSCs activation, proliferation, and collagen synthesis by targeting Smad7, potentially serving as a diagnostic marker and therapeutic target for liver fibrosis.