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.