PROJECT SUMMARY: Heart disease accounts for nearly 1 in 4 deaths in the United States each year, highlighting the urgent need for therapies that can repair damaged hearts. Human induced pluripotent stem cell- derived cardiomyocytes (hiPSC-CMs) have emerged as a powerful cell source for cardiac repair, but their potential has been limited by poor survival and engraftment after injection. To address these challenges, our lab has pioneered the development of nanowired human cardiac organoids composed of electrically conductive silicon nanowires (e-SiNWs), hiPSC-CMs, and supporting cells. Our preliminary in vivo studies showed that nanowired cardiac organoids successfully engraft in ischemia/reperfusion (I/R) injured rat hearts and develop more organized contractile structures compared to non-nanowired cardiac organoids. Despite this progress, less than half (~30%) of injected organoids remained engrafted in infarcted hearts 7 days post-transplantation, which can be attributed to inadequate prevascularization and hypoxic/ischemic preconditioning of the organoids in vitro. To address this, we have explored pharmacological stabilization of HIF-a as a strategy to promote prevascularization and ischemic tolerance within the organoids. My preliminary in vitro data showed that treatment with Molidustat, a prolyl hydroxylase domain (PHD) inhibitor, significantly improved endothelial network and lumen formation (i.e., ~150% increase of CD31+ coverage) within the cardiac organoids. While these results are promising, further investigation is necessary to reveal phenotypic and genotypic changes in HIF-α stabilized cardiac organoids and how they correlate with transplantation efficiency. The goals of this proposal are to determine the effects of HIF-α stabilization on vascular maturation, cardiac function, cell and tissue-level metabolism, and transcriptomic changes in cardiac organoids (Aim 1), and to demonstrate therapeutic efficacy of HIF-α stabilized organoids in a rat model of myocardial I/R injury (Aim 2). The central hypothesis of this proposal is that stabilization of HIF-α signaling in cardiac organoids improves the survival and engraftment of hiPSC-CMs in infarcted myocardium and enhances their capacity to promote cardiac functional recovery in injured hearts. The proposal is innovative in that, for the first time, we will investigate how hypoxia mimetic agents precondition human engineered cardiac tissue to enhance the transplantation efficiency of hiPSC-CMs. My long-term goal is to develop clinically applicable cardiac regenerative therapies to treat cardiovascular diseases. Accordingly, we will pursue the following specific aims: 1) Determine how pharmacological HIF-α stabilization reprograms and preconditions human cardiac organoids for ischemic protection, and 2) Determine the effects of HIF-α stabilization on graft-host anastomosis, long-term engraftment, and therapeutic efficacy of nanowired human cardiac organoids in injured hearts. This resear...