Cardiac Revascularization Post Myocardial Infarction Enhances Remuscularization and Improves Function

Abstract

BackgroundHuman induced pluripotent stem cell‐derived cardiomyocytes (hiPSC‐CMs) offer an unprecedented opportunity to remuscularize infarcted human hearts. However, studies show that the majority of hiPSC‐CMs die post transplantation into the ischemic environment, limiting their regenerative potential and clinical application. Death of transplanted CMs occurs in the first few days post‐transplantation due to ischemia. Thus, attempts have been made to promote blood perfusion (i.e. addition of endothelial cells and/or angiogenic factors). However, these approaches require weeks for new vessels to form and to carry blood compared to the rapid death of transplanted CMs (2–3 days).PurposeOur goal was to improve the vascularization of the ischemic hearts to improve the survival of hiPSC‐CMs and increase heart remuscularization and function.MethodsWe performed left anterior descending artery (LAD) ligation in immunocompromised rats to model myocardial infarction. To improve vascularization, we used an innovative strategy consisting of ready‐made microvessels isolated from adipose tissue that form a vasculature and carry blood within the first days post subcutaneous implantation. We have co‐implanted ready‐made microvessels with hiPSC‐CMs by intra‐myocardial injection 2 weeks post LAD ligation. Cardiac function was assessed at 0, 2 and 4 weeks post‐implantation by echocardiography and by pressure‐volume loop at the endpoint (4 weeks). Immunohistochemistry and blood perfusion studies were performed at 1 and 4 weeks post‐implantation.ResultsCompared to hiPSC‐CM transplantation alone, microvessels promoted a ~600% increase in hiPSC‐CM survival with significant reduction in scar size. Echocardiography and pressure–volume (PV) loop analysis performed 4 weeks post‐MI revealed that hiPSC‐CM transplantation attenuated post‐infarct ventricular dilation and enhanced left ventricular contractility by demonstrating a significant improvement in fractional shortening (FS), ejection fraction (EF) as well as other functional parameters (end‐systolic volume, end‐diastolic volume, dP/dt max and min, Tau). Remarkably, co‐transplantation of hiPSC‐CMs with microvessels showed significantly superior functional recovery compared to hiPSC‐CMs alone in all the parameters assessed. Microvessels showed remarkable persistence and integration at both early and late time points, resulting in significantly faster blood perfusion and higher vessel density in the grafts.ConclusionThese findings provide a novel approach to cell‐based therapies for myocardial infarction whereby incorporation of ready‐made microvessels can serve as a personalized delivery system to improve functional outcomes in cell replacement therapies post‐myocardial infarction.Support or Funding InformationCanadian Institutes of Health Research (CIHR), Institute of Circulatory and Respiratory Health grant #137352 and #PJT153160. Discovery grant from the Natural Sciences and Engineering Research Council (NESERC): RGPIN 06621‐2017.