Abstract
Heart failure with preserved ejection fraction (HFpEF) accounts for >50% of heart failure patients and is particularly prevalent in women. A mechanistic understanding of the intrinsic cardiomyocyte pathology in HFpEF is limited with no selective treatments identified. Gender-specific aspects of HFpEF etiology have not been well characterized. The aim of this study was to experimentally evaluate sex difference in cardiac and cardiomyocyte performance in HFpEF, using a novel recently developed rodent model of HFpEF - the ‘Hypertrophic Heart Rat’. Echocardiography was performed in 50 week male and female HHR/NHR (Normal Heart Rat) using a GE Vivid 9. Fibrosis measurements employed picrosirius red staining. Single myocyte force, shortening and intracellular Ca 2+ measurements were obtained (Myostretcher, Ionoptix). Male and female HHR hearts were hypertrophic (M: 4.9±0.3 vs 3.7±0.1; F: 6.6±0.5 vs 4.4±0.1mg/g CWI) with significant diastolic dysfunction (M:27.8±1.4 vs 18.0±1.7; F: 28.9±1.2 vs 18.9±1.0 E/E’) and preserved systolic function (M:78.4±1.9 vs 74.5±1.3; F: 80.9±1.3 vs 78.1±0.8 EF). Female HHR, but not males, exhibited diffuse interstitial fibrosis (M: 3.33±0.1 vs 3.51±0.1; F: 11.45±0.4 vs 8.44±0.2%). In male, but not female, cardiomyocytes, hypercontractility and high cytosolic operational Ca 2+ levels were observed (64% and 116% increase respectively). The force-length gradient produced by serial stretches of isolated cardiomyocytes was increased in male and female HHR (M:6.8±0.4 vs 4.3±0.8; F: 7.4±0.5 vs 3.0±0.4 nN/%SL stretch) indicating stiffer cardiomyocytes in the HFpEF hearts. The increase in stiffness was significantly accentuated in females. This study indicates that in HFpEF the cardiomyocyte functional etiology is different in males and females. Whilst in males the relationship between cardiomyocyte hypercontractility is the most prominent characteristic of HFpEF, in females the remodelling of the extracellular matrix exacerbates instrinsic myocyte stiffness. Further investigation of the molecular pathways involved in these processes is required for identification of potential therapeutic targets.
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