Exosomes derived from bone marrow mesenchymal stem cells promote angiogenesis via transfer of miR-21-5p after cerebral ischemia in mice

Background Mesenchymal stem cells (MSCs) transplantation is a potential clinical therapy for cerebral ischemia. The therapeutic effects of MSCs primarily depends on the paracrine action by releasing exosomes (Exos). Exosomes derived from bone marrow mesenchymal stem cells (BMSC-Exos) could modulate target cell functions by transferring microRNAs (miRs) cargo. In this study, we aimed to investigate whether BMSC-Exos could promote angiogenesis via transfer of miR-21-5p after cerebral ischemia. Methods BMSC-Exos were isolated from conditioned medium of BMSCs by differential ultracentrifugation, and confirmed by transmission electron microscopy, nanoparticle tracking analysis, and western blot analysis. In mice with middle cerebral artery occlusion (MCAO), the neurological function was evaluated by Zea Longa’s method, and the infarct volume and microvessel density were detected by TTC staining and vWF immunofluorescence staining, respectively. The proangiogenic effects of BMSC-Exos were assessed via proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) in vitro assays. The miR-21-5p expression was detected by qRT-PCR. The expression levels of VEGF, VEGFR2, Ang-1, and Tie-2 were determined by western blot. Results BMSC-Exos significantly improved neurological function and reduced infract volume after cerebral ischemia. Moreover, BMSC-Exos significantly upregulated the microvessel density and the expression levels of proangiogenic proteins VEGF, VEGFR2, Ang-1 and Tie-2 in the ischemic boundary region. MiR-21-5p expression was also dramatically increased after cerebral ischemia. In vitro assays revealed that BMSC-Exos enhanced HUVECs functions including proliferation, migration and tube formation, as well as increasing the expression of VEGF and VEGFR2. However, these proangiogenic effects of BMSC-Exos on HUVECs were reversed by miR-21-5p inhibitor. Conclusion Our study indicated that BMSC-Exos could promote angiogenesis and neurological function recovery via transfer of miR-21-5p. Therefore, the application of miR-21-5p-loaded BMSC-Exos might be an attractive treatment strategy of cerebral ischemia.