Heart failure with preserved ejection fraction is linked to a shift in fibroblast subtypes involving mineralocorticoid receptor signaling

Background Heart failure with reduced (HFrEF) or preserved ejection fraction (HFpEF) cause similar symptoms, however, the respective underlying pathophysiology differs. As a consequence, treatment options for HFpEF are still limited. HFpEF is closely linked to co-morbidities including chronic kidney disease or the metabolic syndrome. Recent clinical trials indicate beneficial effects of mineralocorticoid receptor (MR) antagonists on heart failure related outcomes in patients with diabetic kidney disease or established HFpEF. Purpose The aim of this study was to determine gene expression changes in cardiac cells associated with HFpEF at single cell resolution. Methods and Results We treated male and female C57BL/6 wildtype mice with aldosterone (ALDO, 500µg / kg body weight / day) and a high salt-diet (1 % NaCl with drinking water) and compared them to untreated mice (n=8-12 per group). After two weeks, echocardiography revealed left ventricular diastolic dysfunction (MV-E/E’: ALDO 37.7 ± 0.8 vs. CTRL 29.9 ± 0.5; P<0.001), hypertrophy (LV posterior wall thickness diastole ALDO 0.78±0.01 vs. CTRL 0.60±0.01 mm; P<0.001), and atrial dilatation (left atrial area systole ALDO 4.6±0.1 vs. CTRL 3.7±0.1 mm²; P<0.001), mimicking a HFpEF-like phenotype. We performed single nucleus RNA sequencing of left ventricular tissue. Differential gene expression analysis revealed the biggest impact of ALDO on cardiomyocytes, fibroblasts, and capillary endothelial cells. Among the ten genes that showed overlapping regulation in these three cell types were previously described target genes of the mineralocorticoid receptor (MR), including Zbtb16 or Per1. To identify overlapping and distinct features, we performed a cross-comparison of our results with available data from other HFpEF (high fat diet/L-NAME) or HFrEF (myocardial infarction, angiotensin II infusion) mouse models. Subclustering of cardiac fibroblasts after ALDO indicated a shift towards a fibroblast subpopulation that is different from the typical myofibroblast that is found in HFrEF models. Comparison with high fat diet/L-NAME-induced HFpEF showed an overlapping upregulation of typical MR target genes in both models. To validate the functional consequence of this finding, we used mice with cell type-specific MR deletion in fibroblasts (MRTCF21Cre) and exposed them to ALDO. MRTCF21Cre mice were protected from diastolic dysfunction (MV E/E′ MRTcf21Cre ALDO 25.7 vs. MRwildtype ALDO 31.1; P<0.05), indicating a role for fibroblast MR as upstream regulator of cardiac remodeling in HFpEF. Conclusions MR activation is an overlapping feature of cardiorenal and cardiometabolic HFpEF models. HFpEF is associated with a fibroblast subtype that is different from the myofibroblasts observed in HFrEF. This may explain why MR deletion from fibroblasts prevents disease progression in HFpEF but not (as previously shown [1]) in HFrEF.