Abstract 112: Genetic Deletion of Endothelial microRNA-15a/16-1 Promotes Cerebral Angiogenesis and Neurological Recovery in Ischemic Stroke Through Src Signaling Pathway

Introduction: Cerebral angiogenesis is tightly controlled by certain microRNAs (miRs), such as the miR-15a/16-1 cluster, among others. Recently, we demonstrated that endothelium-targeted deletion of miR-15a/16-1 promotes post-stroke angiogenesis and improves long-term neurological recovery by increasing protein levels of VEGFA, FGF2, and their receptors VEGFR2 and FGFR1. Here, we further investigated the downstream signaling pathways of these pro-angiogenic factors by using a potent Src family inhibitor, saracatinib (AZD0530), in endothelial cell-selective miR-15a/16-1 conditional knockout (EC-miR-15a/16-1 cKO) mice after ischemic stroke. Hypothesis: Pharmacological inhibition of Src signaling cascade using AZD0530 diminishes enhanced post-stroke angiogenesis and long-term neurological recovery induced by the genetic deletion of miR-15a/16-1 in the endothelium. Methods: EC-miR-15a/16-1 cKO and WT littermate controls were subjected to 1h MCAO and 28d reperfusion. AZD0530 (20 mg/kg) was administered daily to both genotypes at 3-21d after MCAO by oral gavage. Cognitive outcomes were determined by Morris water maze tests. Brain atrophy was measured by MAP2 immunostaining. Cerebral blood flow (CBF) was monitored by laser speckle imaging. Brain capillary density and functional vessels were examined by CD31/BrdU and tomato lectin/BrdU double-immunostaining, respectively. Src signaling pathway-related molecules were analyzed by western blotting. Results: Treatment with AZD0530 exacerbates cognitive impairments and brain atrophy in EC-miR-15a/16-1 cKO mice following MCAO. AZD0530 also attenuates the long-term CBF recovery, correlated with inhibiting the generation of newly formed microvessels and functional vessels in the peri-infarct brain regions in EC-miR-15a/16-1 cKO mice after cerebral ischemia. Moreover, EC-targeted deletion of miR-15a/16-1 upregulates the Src signaling pathway, while AZD0530 blocks the Src signaling pathway by downregulating p-Src and its downstream mediators (p-Stat3, p-Akt, p-FAK, p-p38 MAPK) in ischemic brains. Conclusions: Endothelium-targeted deletion of miR-15a/16-1 promotes post-stroke angiogenesis and improves long-term neurological recovery via Src signaling pathway.