Sex-Dependent Fibroblast Signatures in Heart Failure: Toward Stratified Anti-Fibro-Inflammatory Therapies

Cardiac fibroblasts play a central role in myocardial remodeling and exhibit sex-specific differences in abundance and function. How these differences manifest in heart failure remains unclear. This study aimed to characterize how sex influences human cardiac fibroblast activation and the fibro-inflammatory response in heart failure.

Cardiac fibroblasts were isolated from endomyocardial biopsies of the left ventricle from heart failure patients with LVEF<50% and age-matched patients with LVEF≥50% (each group: n=6, 3 men vs. 3 women). Cells were analyzed in vitro regarding cell amount, metabolic activity, collagen deposition, activation marker expression, and morphology. Single-cell RNA sequencing identified fibroblast subpopulations and sex-specific pathway activation.

Metabolic activity differed by sex with higher activity in female compared to male fibroblasts in the LVEF<50% patient group, and the reverse was found in the LVEF≥50% group. In patients with LVEF<50%, female fibroblasts deposited more collagen despite lower α-SMA expression. They appeared more polarized, and asymmetric than male cells, suggesting increased extracellular matrix interaction and migratory capacity. These morphological differences were less pronounced in the LVEF≥50% patient group. Transcriptomic analysis revealed distinct activation programs: male fibroblasts showed broad enrichment of TGF-β-driven extracellular matrix remodeling pathways, indicative of widespread structural remodeling. Female fibroblasts exhibited IL-1-associated remodeling and selective activation of distinct fibroblast subsets, consistent with a more targeted, inflammation-centered response.

Our findings suggest sexual dimorphism in cardiac fibroblast biology with potentially distinct mechanisms. Sex may influence fibroblast activation states that shift in heart failure, underscoring the relevance of considering sex in anti-fibrotic strategies and the use of fibroblasts for individualized disease profiling.