MicroRNA-107 contributes to post-stroke angiogenesis by targeting Dicer-1

Previous studies have suggested that microRNA-107 (miR-107) regulates cell migration in tumor and promotes Hypoxia Inducible Factor 1α (HIF1α) regulated angiogenesis under hypoxia. We found that miR-107 was strongly expressed in ischemic boundary zone (IBZ) after permanent middle cerebral artery occlusion (pMCAO) in rats and inhibition of miR-107 could reduce capillary density in the IBZ after stroke. Such finding led us to hypothesize that miR-107 might regulate post-stroke angiogenesis and therefore serve as a therapeutic target. We also found that antagomir-107, a synthetic miR-107 inhibitor, decreased the number of capillaries in IBZ and increased overall infarct volume after pMCAO in rats. We demonstrated that miR-107 could directly down-regulate Dicer-1, a gene that encodes an enzyme essential for processing microRNA (miRNA) precursors. This resulted in translational desupression of VEGF (vascular endothelial growth factor) mRNA, thereby increasing expression of endothelial cell-derived VEGF (VEGF165/VEGF164), leading to angiogenesis after stroke. This process might be a protective mechanism for ischemia-induced cerebral injury and miR-107 might be used as a novel tool in stroke treatment.