Abstract 21: Genetic Deletion Of MicroRNA-15a/16-1 In Pericytes Stimulates Cerebral Angiogenesis And Promotes Long-term Functional Recovery After Ischemic Stroke

Abstract

Introduction: Post-stroke cerebral angiogenesis actively participates in tissue repair and plays a vital role in the long-term functional recovery in stroke patients. Accumulating evidence shows that certain microRNAs (miRs) regulate cerebral angiogenesis after CNS disorders. We have demonstrated that endothelium-targeted deletion of miR-15a/16-1 promotes post-stroke angiogenesis by enhancing activity of pro-angiogenic factors and their receptors. Here we further investigate the effects of pericyte-derived miR-15a/16-1 on post-ischemic cerebral angiogenesis and outcomes. Methods: Inducible pericyte-specific miR-15a/16-1 cKO mice and WT littermate controls were subjected to 1h MCAO and 28d reperfusion. Neurobehavioral outcomes were determined by the foot fault, rotarod, adhesive tape removal, and Morris water maze tests. Brain atrophy was measured by MAP2 immunostaining. Cerebral blood flow (CBF) was monitored by laser speckle imaging. Brain capillary density, functional microvessels, and neurons were examined by CD31/BrdU, tomato lectin/BrdU, and NeuN/BrdU double immunostaining, respectively. In vitro angiogenesis assays, including BrdU cell proliferation, scratch assay, and capillary tube formation were analyzed in mBMEC cutures treated with conditional medium from primary mouse vascular pericytes (mBVPs) with lentivirus-mediated miR-15a/16-1 knockdown. Pro-angiogenic factors were detected by qPCR and western blotting. Results: Pericytes-miR-15a/16-1 cKO mice exhibit improved sensorimotor and cognitive outcomes, increased CBF recovery, and reduced brain atrophy compared to WT controls. The number of newly-generated cerebral microvessels, functional microvessels, and neurons in the peri-infarct brain regions of Pericyte-miR-15a/16-1 cKO mice are higher than WT controls. Treatment of conditional medium from miR-15a/16-1 silencing pericytes significantly increases endothelial cell proliferation, migration, and tube formation, respectively. Mechanistically, lentiviral silencing of miR-15a/16-1 in primary mBVPs remarkably enhances the expression of both FGF2 and VEGFA. Conclusions: Our findings suggest that pericytic miR-15a/16-1 negatively regulates post-stroke cerebral angiogenesis.