Abstract 107: Selective Igf-1 Production By Resident Cardiac Macrophages Orchestrates Adaptive Cardiomyocyte Growth During Hypertensive Stress

Abstract

Objective: Adaptive cardiomyocyte growth is an essential compensatory response to hypertension. While hypertension activates cardiac immune cells, their role in adaptation is unclear. Here, we define the transcriptional heterogeneity and functional role of cardiac resident macrophages (RMs) in vivo in hypertensive heart disease. Methods: We performed flow cytometry, immunofluorescence, and single-cell transcriptomics on fate-mapped cardiac RMs isolated from mice with angiotensin II infusion in acute (day 4) and chronic hypertensive stress (day 28). Following inducible depletion of RMs or specific genetic deletion of Igf1 in RMs during hypertension in mice, functional outcomes were tested with echocardiography and immunohistochemistry. Lastly, we also performed single-cell RNA sequencing on human cardiac macrophages from healthy and diseased samples. Results: Cardiac RMs possess numerous transcriptionally diverse cell states with a core repertoire of reparative gene programs that includes high expression of Igf1 in normotensive animals. Individual cell states were differentially responsive during hypertension while all maintained their original transcriptional identity. Hypertension drove selective in situ proliferation and numerical expansion of some cardiac RMs, directly correlating with increased cardiomyocyte size. Inducible ablation of RMs, or selective deletion of RM-derived IGF-1 caused complete absence of adaptive cardiomyocyte growth and development of cardiac dysfunction. Single-cell transcriptomics further identified a conserved IGF1 -expressing macrophage subpopulation in human cardiomyopathy. Conclusions: Here, we defined the absolute requirement of cardiac RM-produced IGF-1 in adaptive cardiomyocyte growth during hypertension, identifying a novel and essential pathway of RM-directed cardiac adaptation to disease.