Abstract Thu161: Sex Differences in Cardiac Fibroblast Response to Transient Angiotensin-Converting Enzyme Inhibition

Hypertension-induced heart failure is more prevalent in women, who also develop more cardiac fibrosis than men. Hypertension promotes cardiac fibroblast (CF) activation and extracellular matrix (ECM) production, leading to fibrosis and heart failure. While sex influences ECM remodeling, the underlying mechanisms remain poorly understood. In spontaneously hypertensive rats (SHR), transient angiotensin-converting enzyme inhibition (ACEi) treatment provides long-term protection against fibrosis in males but not females. This study identifies key sex differences in the CF transcriptome at baseline and after transient ACEi treatment. Adult male and female SHR were treated ± ACEi for two weeks, followed by a two-week washout. CD31-, non-cardiomyocyte cells from the left ventricle (LV) were isolated and analyzed using single-nucleus RNA sequencing. CFs from control male SHR exhibited significantly higher expression of ECM-related genes and genes involved in epidermal growth factor receptor (EGFR) signaling compared to control females. Following transient ACEi, female CFs exhibited a transcriptome suggesting greater ECM remodeling and EGFR signaling. ECM was the top Gene Ontology (GO) term associated with significantly upregulated genes in female CFs (Benjamini p = 5.5E-3), including Col1a1, Col3a1, and Col4a1. The top upregulated KEGG pathways in female CFs included pathways in cancer, Ras signaling, and PI3K-AKT signaling (Benjamini p = 8.2E-3, 8.2E-3, 6.5E-3). Notably, Egfr and its downstream targets (Sos2, Rasa2, Pik3r1, Akt3) were significantly upregulated in each pathway. In contrast, the top GO term associated with significantly downregulated genes in male CFs after transient ACEi was "extracellular space" (Benjamini p = 6.9E-5), with reduced expression of ECM components Col4a2, Lama2, and Actn1. These findings reveal significant sex differences in CFs from SHR at baseline and a sexually dimorphic response to ACEi. Increased EGFR-related gene expression in female CFs may contribute to their reduced protection against fibrosis compared to males.