1Albert-Ludwigs-Universität Freiburg Experimentelle und Klinische Pharmakologie und Toxikologie Freiburg, Deutschland; 2Universitäts-Herzzentrum Freiburg - Bad Krozingen Institut für Experimentelle Kardiovaskuläre Medizin Freiburg im Breisgau, Deutschland
Introduction
Heart failure with preserved ejection fraction (HFpEF) is a clinical syndrome in which the heart contracts physiologically but the relaxation is impaired. Therapeutic options for HFpEF are limited and new approaches are needed. The mineralocorticoid receptor (MR), a nuclear transcription factor that is activated by aldosterone, is expressed in all major cell populations in the heart and a known driver of HF with reduced EF. However, much less is known about its role in HFpEF. Here, we determine MR-dependent gene expression at single cell resolution using a model of aldosterone-induced HFpEF.
Methods and Results
C57BL/6N wildtype mice received aldosterone from osmotic minipumps (500 µg/kg BW/d) together with high salt diet (1% NaCl with drinking water, ALDO) and were compared to untreated controls (CTRL). After two weeks, echocardiography revealed impaired diastolic function (E/E’ 36.2 vs. 27.8, P<0.0001) and left atrial dilation in mice treated with ALDO. This was associated with left ventricular hypertrophy (LV wall thickness 0.77 mm vs. 0.60 mm, P<0.0001), moderate fibrosis, and an increase in passive mechanical tissue stiffness in ALDO treated mice, resembling a typical HFpEF phenotype.
We performed single nucleus RNA-seq of left atrial (n = 4) and -ventricular (n = 8) tissue after two weeks of ALDO or CTRL treatment to elucidate the phenotype-driving transcriptional mechanisms. In total, we captured 90,000 nuclei with an average of 2,800 genes being detected. While the global cardiac cellular composition remained largely unchanged, we found marked changes in gene expression profiles within the major cell clusters: Although ALDO had minor impact on the expression of typical HF marker genes (Nppa, Nppb, Ctgf) we observed a shift in the expression of genes related to cardiac metabolic activity. Differential expression of genes involved in heart growth, heart contraction, and angiogenesis was primarily found in LV rather than LA nuclei. Likewise, regulation of MR target gene expression (Fkbp5, Klf9, Per1-3) by ALDO was apparent in LV nuclei. Cell-cell interaction prediction suggested a stronger effect of MR overactivation in LV compared to LA in both total number of interactions and strength of interactions. In LV, major senders were cardiomyocytes and endothelial cells, whereas smooth muscle cells, macrophages and T-cells showed an increase in incoming signaling strength. Pericytes, neurons and particularly fibroblasts displayed an increase in both ingoing and outgoing signaling strength. Upregulated pathways were strongly associated with extracellular matrix remodelling.
Conclusions
ALDO treatment induced LV diastolic dysfunction and remodeling, resembling a typical HFpEF phenotype in mice. snRNA-seq analysis indicates that major changes in gene expression and heterocellular interactions occur in LV endothelial cells, smooth muscle cells and fibroblasts.