Extracellular vesicles derived from live or apoptotic mesenchymal stem cells: comparison of the effects of two extracellular vesicles on liver fibrosis

Mesenchymal stem cells (MSCs) have become a promising treatment of liver fibrosis which is a key process in liver diseases. Recent studies have shown that transplanted MSCs undergo rapid apoptosis and the apoptotic extracellular vesicles (ApoEVs) derived from MSCs exhibited stronger immunosuppressive capability. However, the effect and the mechanisms of ApoEVs in liver fibrosis remain unclear. The functional differences between ApoEVs and extracellular vesicles (EVs) have yet to be elucidated. This study aims to compare their therapeutic effects on liver fibrosis in order to optimize existing treatment strategies. ApoEVs and EVs were isolated by density gradient centrifugation and illustrated by TEM and NTA. A CCl4-induced liver fibrosis mouse model was treated with equal doses of ApoEVs and EVs. Histopathological analysis was performed on liver sections, serological indicators, fibrosis-related gene expression, macrophage polarization, and the activation status of hepatic stellate cells (HSCs) were analyzed. Subsequently, miRNA-sequencing and untargeted metabolomics analysis were conducted to identify potential pathway. Our results demonstrated that ApoEVs had fourfold higher protein yield than EVs, and ApoEVs exhibited a significant superior ability to improve liver fibrosis. In vitro, ApoEVs enhanced macrophage polarization and suppressed HSC activation more effectively, thereby reducing the degree of fibrosis. The underlying molecular mechanism likely due to the enrichment of more miRNAs targeting the PI3K-AKT pathway in ApoEVs and more metabolite molecules that mediate inflammatory metabolic processes. These findings showed that ApoEVs exhibit better effects than EVs in alleviating liver fibrosis. Besides, the findings highlighted their therapeutic potential which suggested that ApoEVs could be a promising approach for the treatment of liver diseases and further lay a research foundation for clarifying the therapeutic mechanism of MSCs.