Project Summary The long-term objective of this application is to understand the molecular pathways of myocardial infraction (MI)- mediated cardiac fibrosis and eventually heart failure. In our last grant cycle, we elucidated thoroughly the role of Neuropilin-1 (NRP1), a multi-ligand receptor/adaptor and mediator of different signaling pathways including TGFβ, in MI-induced cardiac pathogenesis, in particular fibrosis, and inflammation. Our preliminary data suggest that conditional knockdown of NRP1 in the adult mice, either in cardiomyocytes (CM) or in endothelial cells (EC) resulted varied phenotypes following cardiac injury (MI). In addition, our preliminary data from the single-nucleus RNA sequencing (snRNA seq) using the cardiac tissues in a cell-specific manner and revealed marked changes in gene expression patterns of key genes previously known to be associated with inflammation, cardiac hypertrophy, fibrosis. In addition, we revealed microRNA (miR30s) showed differentially expressed in ECNRP1-/- vs. CMNRP1-/- cells that correlated with HF genes. Hence, the scientific premise of this proposal is to reveal the mechanistic role of divergent NRP1 spatiotemporal signaling in MI pathogenesis, and eventually to develop new therapeutic targets and strategies to overcome progressive cardiac dysfunctions and overall heart failure. In this regard, we will examine the spatiotemporal influence of NRP1 pathways for cardiac fibrosis following MI injury as well as define the tissue-specific role of microRNAs regulated by NRP1 pathways on MI-induced fibrosis. Finally, we will develop new therapeutic approaches to overcome cardio fibrosis following MI injury combining novel NRP1 inhibitor (NRP1i) using novel targeted liposomal formulations. The current application is a multi- disciplinary approach to reveal the spatiotemporal role of NRP1 in cardiac fibrosis/remodeling and identify new targets to develop novel therapies to overcome one of the most common myocardial pathologies, which is an unmet clinical need.