Abstract 418: Ready-made Microvessels Robustly Integrate Into the Infarcted Coronary Vasculature Promoting Graft Perfusion, Enhancing Cardiac Remuscularization and Function

Abstract

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offer an unprecedented opportunity to remuscularize infarcted hearts. However, the majority of hiPSC-CMs die post transplantation into the ischemic environment, limiting their regenerative potential. CM death occurs in the first few days post-transplantation due to ischemia. Attempts to promote intramyocardial vascularization (i.e. delivery of growth factors or cells) have not led to significant improvements due to poor cell retention and the long time required for new vessels to form and carry blood compared to the rapid death of transplanted CMs. Here, we used ready-made microvessels harvested from adipose tissue - that form a vasculature and carry blood within the first days post subcutaneous implantation - to re-vascularize ischemic rat hearts and improve hiPSC-CM survival. We performed left anterior descending artery ligation in immunocompromised rats to model MI. hiPSC-CMs (10 x10 6 ) with (CM+V) or without (CM-only, control) microvessels were delivered by intra-myocardial injection 2 weeks post MI. Cardiac function was assessed by echocardiography and pressure-volume loop. Delivery of microvessels from GFP rats allowed assessment of microvessel persistence. Compared to hiPSC-CM transplantation alone, microvessels promoted a 6-fold increase in hiPSC-CM survival, with reduction in scar size and a significantly superior functional recovery. While delivery of CM-only stabilized the heart preventing further fractional shortening decline, delivery of CM+V resulted in reversal of fractional shortening loss. This was supported by PV-loop data (ejection fraction: sham, ~20%; CM-only, ~31%; CM+V, ~39%; 4 wks). Moreover, microvessels showed unprecedented persistence and integration (>60%, 4 wks), resulting in 2-fold increase in vessel area and graft perfusion (as early as day 5 post-transplantation). This was achieved despite the very low number of cells (~2 x10 5 ) delivered in the form of microvessels. These findings provide a novel approach to cell-based therapies for MI whereby incorporation of ready-made microvessels can serve as a personalized delivery system to improve functional outcomes in cell replacement therapies.