Neural stem cell–derived exosomes regulate cell proliferation, migration, and cell death of brain microvascular endothelial cells via the miR‐9/Hes1 axis under hypoxia

Background Our previous study found that mouse embryonic neural stem cell (NSC)–derived exosomes (EXOs) regulated NSC differentiation via the miR‐9/Hes1 axis. However, the effects of EXOs on brain microvascular endothelial cell (BMEC) dysfunction via the miR‐9/Hes1 axis remain unknown. Therefore, the current study aimed to determine the effects of EXOs on BMEC proliferation, migration, and death via the miR‐9/Hes1 axis. Methods Immunofluorescence, quantitative real‐time polymerase chain reaction, cell counting kit‐8 assay, wound healing assay, calcein‐acetoxymethyl/propidium iodide staining, and hematoxylin and eosin staining were used to determine the role and mechanism of EXOs on BMECs. Results EXOs promoted BMEC proliferation and migration and reduced cell death under hypoxic conditions. The overexpression of miR‐9 promoted BMEC proliferation and migration and reduced cell death under hypoxic conditions. Moreover, miR‐9 downregulation inhibited BMEC proliferation and migration and also promoted cell death. Hes1 silencing ameliorated the effect of amtagomiR‐9 on BMEC proliferation and migration and cell death. Hyperemic structures were observed in the regions of the hippocampus and cortex in hypoxia‐induced mice. Meanwhile, EXO treatment improved cerebrovascular alterations. Conclusion NSC‐derived EXOs can promote BMEC proliferation and migration and reduce cell death via the miR‐9/Hes1 axis under hypoxic conditions. Therefore, EXO therapeutic strategies could be considered for hypoxia‐induced vascular injury. MiR‐9 was enriched in neural stem cell‐derived exosomes (EXOs). EXOs promote brain microvascular endothelial cell proliferation and migration and reduce cell death via the miR‐9/Hes1 axis.