Sex Differences in Cardiac Macrophages in Response to Pulmonary Hypertension - Project Abstract Pulmonary arterial hypertension (PAH) is a progressive and incurable disease with high morbidity and mortality. Although PAH is significantly more prevalent in women compared to men, female PAH patients exhibit better right ventricular (RV) function and survival. However, the mechanisms underlying superior female adaptation to RV pressure overload in PAH remain unknown. This proposal seeks to identify the role of RV macrophages in mediating sexual dimorphisms in RV function in PAH. This investigation is motivated by our compelling recently published data demonstrating that macrophages play a role in RV maladaptive remodeling in experimental pulmonary hypertension (PH) through effects the extracellular matrix (ECM), and that removal of macrophages in PH results in decreased collagens and other ECM proteins, improving RV contractility and RV-pulmonary arterial (RV-PA) coupling. Furthermore, through single cell RNA sequencing experiments of cells from the murine RVs, we discovered profound sexual dimorphism in gene expression in resident cardiac macrophages from male and female mice that include upregulation of several genes involved in ECM organization and collagen binding in males. We have previously shown that endogenous and exogenous 17beta-estradiol (E2) improves RV function in ovariectomized females and in males with PH, that E2 decreases collagen accumulation in the RV, and that E2 down-regulates the pro-inflammatory and pro- fibrotic transcriptome of bone marrow-derived macrophages. We now seek to understand whether the sexual dimorphisms we identified in RV adaptation and cardiac macrophage function are explained in part by transcriptional effects of sex hormones on the pro-fibrotic programming of RV macrophages. We hypothesize that female sex hormones regulate expression of RV macrophage genes associated with fibroblast activation and ECM stiffness, resulting in sexual dimorphisms in RV contractility, stiffness, and diastolic dysfunction in adaptation to RV pressure overload. Specifically, we hypothesize that female hormones downregulate pro-fibrotic programming in resident RV macrophages, resulting in less fibroblast activation and ECM stiffening. We will utilize the experimental PH models of mouse pulmonary artery banding and rat Sugen hypoxia, and examine differences in resident RV macrophage gene expression, RV contractility and stiffness, and the RV ECM between healthy and diseased male and female animals. We will utilize a menopausal animal model and exogenous estradiol hormone replacement therapy to examine how female and male sex hormones regulate RV macrophage programming.
