Macrophage functional dynamics in adult heart regeneration

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Much of the basic research on cardiac biology has been focused on cardiomyocytes (CMs), aiming to unravel the basic principles underlying cardiac physiology and pathophysiology for future development of therapeutic interventions to treat cardiac diseases. Besides CMs, the heart contains many other cell types including endothelial cells, fibroblasts, and a wide variety of immune cells. During heart development and homeostasis, non-myocytes (nonCMs) have been increasingly recognized to play active roles in regulating various CM behaviors. Yet a lack of detailed information on the cellular identities and cell states of the nonCMs associated development and homeostasis is a major hurdle to precisely delineating the biological events in heart development and homeostasis. In our recently published study, we delineated nonCMs cellular and transcriptomic dynamics during cardiac regeneration. Through scRNA-seq, we identified major nonCM cell types, including multiple macrophage (MC), FB and EC subpopulations with unique tempo-spatial distribution. Prticularly, we found that MC exists in multiple definable states that exhibit dynamic functional changes from acute inflammatory response to inflammation resolution. Interestingly, perturbing MC function resulted in defective cardiac regeneration. Combining Topologizer and RNA velocity analyses, we uncovered dynamic transition between MC functional states and identified factors involved in mRNA processing and transcriptional regulation associated with the transition. However, whether and how nonCMs interact at the subpopulation level, and MC dynamic functional change affects nonCMs interactions and hence heart regeneration remains largely unexplored. In this research proposal, we hypothesize that heart regeneration is a highly orchestrated process involving temporally regulated MC function executed by the distinct subtypes and their interactions with other nonCM cell types. To test this hypothesis, we aim to 1) define the role of the inflammatory MCs (iMCs) subtype in nonCM interaction and heart regeneration, 2) delineate the role of the immune surveillance MC (isMCs) subtype in nonCM interaction and heart regeneration, and 3) study the molecular mechanism governing transition of MC functional states.