Extracellular vesicles enriched with miR-486 from Tetramethylpyrazine-preconditioned bone marrow mesenchymal stem cells promote microglia/macrophage M2 polarization and enhance neurogenesis in rats with ischemic stroke

Background Bone marrow mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) show therapeutic promise for ischemic stroke (IS). Preconditioning MSCs with drugs can modulate the cargo composition and function of their derived EVs. This study investigated the therapeutic effects and underlying mechanisms of EVs derived from tetramethylpyrazine (TMP)-preconditioned BMSCs (TMP-BMSC-EVs) in IS. Methods EVs were isolated from BMSCs pretreated with or without TMP by differential centrifugation. The therapeutic efficacy of EVs was evaluated in a rat model of middle cerebral artery occlusion (MCAO) through neurological function assessments and infarct volume quantification. The expression of miR-486 and its roles in regulating microglia/macrophage polarization and neurogenesis, as well as the mechanistic targets, were examined by real-time quantitative polymerase chain reaction (RT-qPCR), immunofluorescence staining, and Western blotting. Results TMP-BMSC-EVs exerted superior therapeutic efficacy compared to BMSC-EVs. Mechanistically, TMP-BMSC-EVs were enriched with miR-486, which promoted microglia/macrophage M2 polarization and neurogenesis, while downregulating phosphatase and tensin homolog (PTEN) and phosphorylated NF-κB (p-NF-κB) protein levels, and upregulating phosphorylated Akt (p-Akt) expression. Transfection with a miR-486 inhibitor abolished the beneficial effects of TMP-BMSC-EVs, which could be counteracted by the PTEN inhibitor bisperoxovanadium (bpV). Conclusions TMP-BMSC-EVs could significantly promote neural repair by driving microglia/macrophage M2 polarization and enhancing neurogenesis through miR-486-mediated PTEN inhibition, thereby offering a promising treatment strategy for IS.