Abstract P3080: Macrophages Synthesize Bioactive Lipids To Modulate Cardiomyocyte Metabolism And Proliferation During Cardiac Regeneration

Abstract

Introduction: Once thought to be a quiescent process, elimination of dying cells by macrophages actively reprograms macrophage metabolism to support downstream functions. Previously, we discovered that the phagocytic receptor MerTK is necessary for regeneration in the neonatal murine heart. Single-cell RNA sequencing and bulk-tissue lipidomics revealed prioritization of arachidonic acid metabolism towards the synthesis of Thromboxane A 2 (TXA 2 ) in regenerating hearts, yet the molecular mechanisms directly connecting macrophage-derived TXA 2 to regeneration remained undefined. Therefore, we sought to determine if TXA 2 and activation of its receptor ( Tbxa2r ) on cardiomyocytes is necessary for cardiac regeneration. Results: We created a novel mouse to conditionally knockout Tbxa2r in cardiomyocytes using the CRE recombinase under the Myh6 promoter. Loss of Tbxa2r did not affect normal cardiac development but significantly impaired cardiac regeneration as seen by significant fibrotic scarring, reduced cardiac output, and decreased cardiomyocyte proliferation. We next asked how Tbxa2r initiates intracellular signaling to support cardiomyocyte proliferation. Knowing that the YAP/TAZ pathway has been previously described to induce cardiomyocyte proliferation during regeneration and is regulated by GPCRs, we found that TXA 2 mimetics activate TBXA2R leading to the stabilization of YAP/TAZ in a time- and dose-dependent manner. Furthermore, YAP was translocated into the nucleus of cardiomyocytes in the border zone 3 days post-MI. However, deletion of Tbxa2r in cardiomyocytes completely prevents YAP translocation into the nucleus. Lastly, we have found that a TXA 2 mimetic increases the glycolytic capacity of cardiomyocytes further supporting anabolic processes needed for proliferation. Excitingly, we also observed an increase in glycolytic enzyme transcripts at the border zone of the infarct using publicly available spatial transcriptomic data. Conclusions: Our findings advance our understanding of how cell death, removal and recycling regulate macrophage metabolism, resulting in the production of bioactive lipids that further regulate the metabolism of neighboring cardiomyocytes during regeneration.