Heart disease remains the leading cause of mortality worldwide with myocardial infarction (MI) affecting over 700,000 individuals annually in the United States alone. As standard therapies fail to recover the injured myocardium, any advances in the treatment of cardiac ischemia would have major clinical significance. Recently, cell-free biological therapies using cell-secreted exosomes have shown promise in achieving cardiac recovery. Exosomes contain sets of micro-RNAs (miRNAs) that they deliver to induce pleiotropic effects. As exosomes from different cell types carry different sets of miRNAs, some exosomes may have increased ability to recover the injured heart. In preliminary studies, I determined that exosomes from induced pluripotent stem cell derived cardiomyocytes (iCM-ex) were able to mediate recovery of the heart, resulting in improved ejection fraction and reduced infarct size after MI. An in-depth understanding of the cellular and molecular mechanisms behind iCM- ex induced cardiac recovery will be critical to further advance the utility of iCM-ex treatment. In pursuit of this goal, I propose the following aims: In Aim 1, I will investigate the ability of iCM-ex to deliver miRNAs that can directly alter gene expression and promote recovery in cardiomyocytes after hypoxic injury. I hypothesize that I will be able to identify a set of miRNAs delivered by iCM-exs to CMs that can directly regulate CM responses to hypoxia, protecting them from injury and preventing cell death. In Aim 2, I will determine how the timing of iCM-ex delivery after MI affects functional recovery. Based on how iCM-ex affect each phase of cardiac repair following MI, I hypothesize that I will be able to establish an iCM-ex treatment strategy that results in greater functional recovery. Overall, my proposed research is designed to advance the utility of iCM-ex treatment by identifying the key cellular and molecular mechanisms responsible for iCM-ex mediated cardiac recovery. I anticipate that this will allow for the future development of precisely controlled cell-free treatments that can be safely deployed in the clinic. This proposed project will be conducted in the lab of my sponsor, Dr. Gordana Vunjak-Novakovic, a University Professor on faculty at the Departments of Biomedical Engineering and Medicine at Columbia University. As part of a broader training plan for this fellowship, the execution of this project under her direct mentorship will allow me to expand and refine my technical skills in cardiac biology, computational analysis, and tissue engineering and to improve my ability to generate concrete hypotheses and formulate impactful projects. Additionally, my training plan includes substantial clinical training at the New York Presbyterian Hospital at the Columbia University Medical Center, a thousand-bed hospital home to the Vivian and Seymour Milstein Family Heart Center, one of the top hospitals in the field of cardiology. Together, this training plan will allow me to connect the laboratory bench to the patient bedside and benefit from an extensive network of dedicated scientific, clinical and professional mentors. If awarded, this fellowship will support my ultimate goal of developing into an independent and productive physician-scientist.