Abstract Body: Hypertension-induced heart failure is more common in women, who also develop more cardiac fibrosis. Fibrosis arises when hypertension drives cardiac fibroblast (CF) activation and extracellular matrix (ECM) deposition. In male spontaneously hypertensive rats (SHR), transient angiotensin-converting enzyme inhibitor (ACEi) treatment confers lasting antifibrotic protection, whereas females exhibit increased risk of fibrosis. This study investigates the transcriptomic and epigenetic sex differences in CF that underlie these opposing outcomes.
SHRs received ± ACEi for 2 weeks, followed by a 2-week washout. Single-nucleus RNA/ATAC sequencing was performed on left-ventricle non-cardiomyocyte, CD31-negative cells. Two CF populations emerged: a large homeostatic cluster (Pi16, Tcf21) and a small activated/inflammatory cluster (Ccn2, Thbs1, Sparc, Mmp2, Nfkb, Il1r1). At baseline, male CFs expressed higher ECM-regulating genes, while females showed increased accessibility at activation-associated promoters, indicating a primed but less active state.
In females, transient ACEi shifted homeostatic CFs toward activation and reduced accessibility at regulatory/anti-inflammatory loci (e.g., Arid1a, Tnfaip3). ECM genes were strongly upregulated (GO Term ECM p=7.85E-7), including Col1a1, Col3a1, and Col4a1. KEGG pathways enriched included pathways in cancer and PI3K-AKT signaling (p=2.7E-5 and 6.1E-5), with increased Egfr, Sos2, Pik3r1, and Akt3. In males, ACEi downregulated ECM-regulating genes (GO Term ECM p=9E-6), including Col4a2, Lama2, Actn1, and reduced accessibility at Emp1, Ets1, and Boc.
In activated CFs, females upregulated profibrotic/inflammatory genes (e.g., Loxl2, Map3k14) and decreased chromatin accessibility at immune-regulatory loci (e.g., Tnfaip3, Ccl3), locking CFs into a persistently activated state after ACEi. Males showed broad suppression of structural/stress-response genes (e.g., Fn1, Csf1) without chromatin changes, indicating transcriptional dampening independent of epigenetic alteration.
Overall, transient ACEi drives divergent CF trajectories: antifibrotic resilience in males versus primed, persistent profibrotic activation in females, supporting the need for sex-specific therapeutic strategies.