Mesenchymal stem cell-derived exosomes protect against liver fibrosis via delivering miR-148a to target KLF6/STAT3 pathway in macrophages

Abstract Background Despite emerging evidence on the therapeutic potential of mesenchymal stem cells (MSCs) for liver fibrosis, the underlying mechanisms remain unclear. At present, MSC-derived exosomes (MSC-EXOs) are widely accepted as crucial messengers for intercellular communication. This study aimed to explore the therapeutic effects of MSC-EXOs on liver fibrosis and identify the mechanisms underlying the action of MSC-EXOs. Methods Carbon tetrachloride was used to induce a liver fibrosis model, which was intravenously administered with MSCs or MSC-EXOs to assess treatment efficacy. The resulting histopathology, fibrosis degree, inflammation and macrophage polarization were analyzed. RAW264.7 and BMDM cells were used to explore the regulatory effects of MSC-EXOs on macrophage polarization. Then, the critical miRNA mediating the therapeutic effects of MSC-EXOs was screened via RNA sequencing and validated experimentally. Furthermore, the target mRNA and downstream signaling pathways were elucidated by luciferase reporter assay, bioinformatics analysis and western blot. Results MSCs alleviated liver fibrosis largely depended on their secreted exosomes, which were visualized to circulate into liver after transplantation. In addition, MSC-EXOs were found to modulate macrophage phenotype to regulate inflammatory microenvironment in liver and repair the injury. Mechanically, RNA-sequencing illustrates that miR-148a, enriched in the MSC-EXOs, targets Kruppel-like factor 6 (KLF6) to suppress pro-inflammatory macrophages and promote anti-inflammatory macrophages by inhibiting the STAT3 pathway. Administration of miR-148a-enriched MSC-EXOs or miR-148a agomir shows potent ameliorative effects on liver fibrosis. Conclusions These findings suggest that MSC-EXOs protect against liver fibrosis via delivering miR-148a that regulates intrahepatic macrophage functions through KLF6/STAT3 signaling and provide a potential therapeutic target for liver fibrosis.