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

Background: Mesenchymal stem cells (MSCs) have become a promising treatment of liver fibrosis which is a key process in liver diseases. Recent studies showed that transplanted mesenchymal stem cells (MSCs) undergo rapid apoptosis and the apoptotic extracellular vesicles (ApoEVs) derived from MSCs exhibited stronger immunosuppressive capability. But 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. Methods: 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 analysis was conducted to identify potential pathway. Results: 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. Conclusion: These findings showed that ApoEVs exhibit better efficacy than EVs in treating liver fibrosis. Besides, the findings highlighted their therapeutic potential, clarified functional differences, and suggested ApoEVs as a promising strategy for liver disease treatment.