Human Placental Stem Cell Therapy in Stroke: Endothelial / Smooth Muscle Mechanisms Underlying Protection?

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 include secretion of protective and trophic factors which limit acute brain I/R injury. We evaluated human placenta mesenchymal stem cells (hPMSC) as potential ameliorative SCT in an acute ischemic stroke model. We hypothesized that potential benefits of hPMSCs, in acute stroke injury, reflect site‐specific suppression of post‐ischemic immune cell adhesion, transvascular leukocyte emigration and preservation of the BBB. This can limit the progression of post –ischemic stroke injury. We found that intraperitoneal (IP) administration of hPMSCs at the time of reperfusion, using the transient middle cerebral artery occlusion (MCAO)/reperfusion model, produced highly significant protection of the ipsilateral hemisphere. We then examined hPMSC support of BBB integrity via mobilization of junctional proteins in human brain endothelial cells (hCMEC‐D3) in conjunction with a biotin/FITC‐avidin permeability assay coupled with western blotting and immunolocalization of junctional proteins. We also assessed the ability of hPMSC to suppress inflammation‐driven hCMEC‐D3 binding of macrophages (RAW264.7) and transmigration of PMNs. In addition, we used collagen gels to study the influence of hPMSC on human brain vascular smooth muscle cells (hBVSMC) tonic contractility.We observed that hPMSC administration significantly (p<0.001) enhanced the barrier integrity of brain endothelial monolayers, at 24h, in an oxygen/glucose deprived/reperfused (OGDR) condition. We found that hCMEC‐D3, which were independently co‐cultured with hPMSCs, expressed significantly higher levels of VE‐cadherin and α‐catenin under OGDR conditions (p<0.001). Additionally, the spatial localization of VE‐cadherin and α‐catenin at hCMEC‐D3 junctions was increased, in the OGDR state, following hPMSC treatment. We also observed that hPMSC treatment significantly (p<0.0001) reduced binding of RAW264.7 to TNF‐α/ LPS activated hCMEC‐D3 monolayers. The expression of VCAM‐1 was increased in TNF‐α/ LPS activated hCMEC‐D3 while this was significantly (p<0.01, P<0.05) decreased by hPMSC treatment. hPMSC also inhibited (p<0.05) PMN transmigration across hCMEC‐D3 monolayers. Lastly, we found that hBVSMC contraction was significantly increased by hPMSC treatment (p=0.0001). This effect was reversed by angiotensin II Type 1 receptor blockade (Losartan, 50μM), angiotensin converting enzyme (Captopril, 50μM), thromboxane A2 synthesis (Ozagrel, 10μM), and endothelin converting enzyme inhibition (SM19712, 100μM).We conclude that pleiotropic factors associated with hPMSC administration can have a favorable impact on BBB integrity, immune cell interaction, and vasoregulation potentially alleviating the detrimental effects of ischemic stroke.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.