Abstract Body: Introduction
Mammalian cardiomyocytes have a low turnover rate which is insufficient to repopulate the damaged myocardium after injury caused by myocardial infarction (MI). Previously, we reported that ferroptosis is the main mechanism of cardiomyocyte death in the infarcted neonatal heart. We hypothesized that ferroptotic cardiomyocytes play a beneficial role during the wound healing process.
Aims
In this study, we aim to characterize the role of ferroptotic cardiomyocytes by investigating their influence on non-cardiomyocyte populations in the heart post-MI.
Methods
Left anterior descending artery occlusion (LAD-O) was performed on wild type (C57BL/6J x FVB) mice at P1. Ferroptosis inhibitor ferrostatin-1 (Fer-1) was delivered at a 2mg/kg dose via subcutaneous injection immediately following LAD-O procedure and again daily until P4. Histology and immunofluorescence were performed to assess myocardial regeneration. iPSC-derived cardiomyocytes (iCMs) were treated with Erastin, Staurosporine, or vehicle control to generate conditioned media. HUVECs were treated with iCM conditioned media for tube formation assays.
Results

The infarcts of Fer-1 treated animals show decreased total macrophages from 5.5% to 0.16% (P < 0.05, N = 6 per group, S.E.M. = 1.2%) and those present were less polarized towards the M2 phenotype, decreased from 62.5% to 7.9% (N = 6 per group, P < 0.001, S.E.M. = 9.6%). This trend was confirmed via flow cytometry. The number of Emcn⁺ cells in the infarct was significantly reduced in Fer-1 treated mice, decreasing from 17% to 10% (S.E.M. = 1.7%, N = 4 per group, P < 0.01). HUVECs treated with conditioned media generated by treating iPSC-derived cardiomyocytes with Staurosporine, but not Erastin or DMSO, showed reduced mesh area (fold change from 0.94 to.0 24, N = 5 per group, P < 0.01. S.EM. = .128). Other tube formation endpoints such as extremities, junctions, and branching followed this trend.
Conclusions
Our analysis revealed that ferroptotic cardiomyocytes play a supportive role in the wound healing and tissue remodeling environment by directly supporting angiogenesis and polarizing the cardiac macrophages towards a more pro-angiogenic state.