Abstract 225: Coordinated Transcriptome and Cell State Dynamics of Non-myocytes in Heart Regeneration

Abstract

Cardiac regeneration occurs primarily through proliferation of existing cardiomyocytes, yet the regenerative response also involves complex interactions between distinct cardiac cell types including not only cardiomyocytes, but also non-cardiomyocytes (nonCMs). However, the subpopulations, distinguishing molecular features, cellular functions, and intercellular interactions of nonCMs in heart regeneration remain largely unexplored. Using the LIGER algorithm, we assembled an atlas of cell states from 61,977 individual nonCM scRNA-seq profiles isolated at multiple time points during heart regeneration in both wildtype and mutant fish. This analysis revealed extensive nonCM cell diversity, including multiple macrophage, fibroblast and endothelial subpopulations with unique spatiotemporal distributions and cooperative interactions during the process of cardiac regeneration. Genetic and pharmacological perturbation of macrophage functional dynamics compromised interactions among nonCM subpopulations, reduced cardiomyocyte proliferation, and caused defective cardiac regeneration. Furthermore, we developed a computational algorithm called Topologizer to map the topological relationships and dynamics of nonCMs during heart regeneration. We uncovered dynamic transitions between macrophage functional states and identified factors involved in mRNA processing and transcriptional regulation associated with the transition. Together, our single-cell transcriptomic analysis of nonCMs during cardiac regeneration provides a blueprint for interrogating the molecular and cellular basis of cardiac regeneration.