PROJECT SUMMARY/ABSTRACT Cardiac allograft vasculopathy (CAV), a form of chronic rejection, is a leading cause of late graft failure and mortality after heart transplantation (HT). It is characterized by diffuse intimal thickening of the entire coronary tree, including the epicardial coronary arteries and microvasculature. Currently, therapies are initiated after identification of epicardial CAV on coronary angiography. However, they have limited efficacy once epicardial disease is detected. There remain substantial unmet needs in CAV prevention and treatment, due in part to a lack of fundamental understanding of the mechanisms early in CAV pathogenesis. The PI’s long-term career goal is to develop into an independent physician-scientist leading a patient-oriented research program in heart transplant biology. The PI has previously shown feasibility of performing single-nuclear RNA sequencing (snRNA-seq) on endomyocardial biopsies (EMBs) collected routinely during post-HT clinical care. The central hypothesis of this proposal is that unique and dynamic gene regulatory networks define early and progressive CAV. The Specific Aims of the proposed research are (1) To define dynamic cell-specific transcriptional programs in individuals with new and progressive epicardial CAV within the first-year post-transplant; (2) To characterize longitudinal changes in cell-specific chromatin accessibility in individuals with progressive epicardial CAV during the first-year post-transplant; and (3) To identify transcriptional signatures that precede CAV in PBMCs and compare relative expression to myocardial tissue. Identified genes will be highly relevant to clinical CAV, whether serving as biomarkers preceding CAV or influencing progressive disease, and will be prioritized for functional and clinical utility studies in the next phase of the PI’s career (i.e., R01). This work is supported by primary co-mentors, Dr. Jane Freedman and Dr. Ravi Shah, and a multidisciplinary research advisory committee comprising of experts in clinical heart transplantation, RNA sequencing, immunology, bioinformatics, and multi-omics. The PI will leverage the highest-volume heart transplant center in the world over the past three years, Vanderbilt University Medical Center, to accomplish the proposed Aims. During this award, the PI will also complete a Master’s in Clinical Investigation and select courses in immunology, advanced statistics, and machine learning to augment his research experience. Through the studies outlined in this proposal, an exemplary mentorship team, and a well-defined career development plan, the PI will (1) obtain a foundation in patient-oriented translational research, (2) develop state-of-the-art CAV molecular phenotypes, (3) gain expertise in immunology and advanced statistical modeling of high-dimensional data, and (4) refine professional development and scientific communication skills to successfully transition into an independently-funded physician-scienti...