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

Abstract

Following thrombolytic therapy in stroke, ischemia/reperfusion (I/R) mediated inflammation impairs maintenance of blood brain barrier (BBB), enhance expression of endothelial and leukocyte adhesion molecules and perturbs normal blood flow regulation. Currently, benefits of stem cell therapy (SCT) in stroke are thought to reflect secretion of protective and trophic factors which limit acute brain I/R injury. We studied human placenta mesenchymal stem cells (hPMSC) as a potent, high‐yield and inexpensive tool in SCT for human stroke therapy. We found that acute intravenous hPMSC administration significantly reduced infarct size (p<0.05) at 24h in our acute (1h) model of middle cerebral artery occlusion (MCAO) in rats. Our hypothesis was that acute benefits of hPMSCs in stroke might reflect suppression of post‐I/R immune, inflammatory and BBB disturbances which limit the onset and progression of stroke injury following restoration of blood flow. We first examined hPMSC support of BBB via mobilization of junctional proteins in human brain endothelial cells (hCMEC‐D3) in conjunction with FITC‐Dextran and FITC‐biotin‐gelatin avidin permeability assays plus western blotting and immunolocalization of junctional proteins. We also assessed the ability of hPMSC to suppress inflammation driven hCMEC‐D3 binding of macrophages (RAW246.7). Lastly we studied the influence of hPMSC on contractility of human brain vascular smooth muscle cells (hBVSMC) in collagen gel contraction assays.hPMSC significantly (p<0.001) enhanced barrier integrity at 24h in oxygen/glucose deprived/reperfused (OGDR) brain endothelial monolayers (in both FITC‐dextran and FITC‐biotin assays. We found that hCMEC‐D3 which were contact‐‐independently co‐cultured with hPMSCs expressed significantly higher levels of VE‐cadherin and α‐catenin under OGDR conditions (p<0.001); surprisingly, we did not see significant increases in occludin or claudin‐5 expression. Additionally, the spatial localization of VE‐cadherin and α‐catenin at hCMEC‐D3 junctions was apparently increased under OGDR, but not control conditions after hPMSC treatment. We also saw that hPMSC significantly (p<0.0001) reduced binding of macrophages to activated brain endothelial monolayers. Lastly, we found that hBVSMC contraction was significantly increased by hPMSC (p=0.0001), an effect which was reversed by Angiotensin II Type 1 receptor inhibition (Losartan, 10 uM) (p=0.004), but not by thromboxane A2 or endothelin‐1 blockade.We conclude that hPMSC release stable factors which beneficially and acutely influence endothelial barrier integrity, interactions with immune cells and vasoregulation to improve recovery in stroke.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.