Abstract TP102: Human Placental Mesenchymal Stem Cells Derived Exosome-Angiotensin Converting Enzyme-2 Dependent Protection in Ischemic Stroke Injury

Abstract

Following thrombolytic therapy for stroke, ischemia/reperfusion (I/R) mediated inflammation often disrupts the blood brain barrier (BBB). This can enhance expression of endothelial adhesion markers and perturb normal blood flow regulation. Proposed benefits of stem cell therapy (SCT) in stroke, besides long-term trans-differentiation into neural cells, include secretion of protective factors, which partly depends on exosomes released by stem cells. We evaluated human placenta mesenchymal stem cells (hPMSC) as potential ameliorative SCT in an acute ischemic stroke model. We hypothesize that hPMSC would achieve site-specific suppression of post-ischemic immune cell transmigration, preservation of the BBB and maintenance of blood flow via ‘paracrine’ signaling pathways in acute stroke injury.We found that intraperitoneal (IP) administration of hPMSC at the time of reperfusion, using the middle cerebral artery occlusion (MCAO)/reperfusion model, produced significant protection ( p =0.0001) of the ipsilateral hemisphere. We also demonstrated that hPMSC-treated MCAO mice exhibited significantly greater neurological recovery ( p <0.0001) compared to untreated MCAO, an effect which was accompanied by significant restoration of blood flow ( p <0.01) to the MCAO-stressed brains. Using Evans Blue dye assay, we also observed significant ( p =0.004) improvement of BBB integrity in ipsilateral hemispheres of hPMSC-treated mice vs MCAO controls. Furthermore, we determined that hPMSC-derived exosomes contribute to paracrine based protection of hPMSC in MCAO model. Importantly, we found that hPMSC/exosome protection is mediated partly by the function of angiotensin converting enzyme 2 (ACE2). To evaluate the contribution of ACE2 in protection of the brain after ischemic stroke, we first demonstrated that hPMSC and their exosomes express ACE2. Second, mice injected with hPMSC which had been pre-treated with the specific ACE2 inhibitor (10μM) MLN-4760, showed tissue injury and neurological behavior similar to that seen in untreated MCAO.We conclude that pleiotropic factors associated with hPMSC administration can have a favorable impact on blood flow, BBB integrity potentially alleviating the detrimental effects of ischemic stroke.