Abstract 11486: Hormone-Independent Sex Dimorphisms in Cardiac Reparative Functions of Bone Marrow Stem Cells: Underlying Epigenetic Insights

Abstract

Introduction: This work was designed to identify the hormone-independent mechanisms that govern the superiority of female endothelial progenitor cells (F-EPC) for cardiac repair post myocardial infarction (MI). A direct comparison of therapeutic efficacy of gender-specific stem cells or estrogen-independent mechanisms of gender-specific dimorphism in the reparative properties of EPCs has not been established. Hypothesis: We hypothesized that epigenetic mechanisms contribute to the sex-specific functional dimorphisms of Sca-1+/CD31+ EPCs in regulating cardiac reparative functions post-MI. Methods: Male (M), female (F), and ovariectomized (OVX) mice derived Sca-1+/CD31+ EPCs were subjected through a series of cytokine quantifications and epigenetic CUT&Tag screening, followed by assessment of their therapeutic function in vitro and in vivo . Results: F-EPC and OVX EPC secrete high levels of proangiogenic factors and low amounts of pro-inflammatory cytokines compared to M-EPC. Further evaluation of the inflammasome showed that the M-EPC secreted the most elevated amounts of CCL3, and other inflammatory chemokines compared to F-EPC and OVX EPC. The secretome of F-EPC and OVX EPC was found to be substantially proangiogenic in vitro than the male EPCs. Post-MI injection of F-EPC and OVX EPC resulted in remarkable preservation of cardiac structure and functions. In contrast, post-MI injection of M-EPC resulted in an inflamed myocardium. Epigenetic sequencing of the sex differential EPCs for the H3K9me3 mark showed high methylation in M-EPC compared to F-EPC and OVX EPC. The inhibition of histone methyltransferase, G9a using BIX-01294 upregulated the secretion of inflammatory factors in all EPCs. The conditioned medium from all EPCs with high levels of CCL3 inhibited angiogenesis in vitro . Neutralizing CCL3 in the same medium restored in vitro angiogenesis. Conclusion: EPCs from both fertile and OVX female mice retain better cardiac reparative activity than their male counterparts irrespective of sex hormone influence. Mechanistically, we show that this gender-based functional dimorphism of EPCs is mediated, in part, by differential epigenetic regulation of chemokine CCL3.