Abstract
Heart failure with preserved ejection fraction (HFpEF) accounts for more than 50% of all HF cases. HFpEF patients manifest normal or mildly reduced left ventricle (LV) ejection fraction (LVEF), LV hypertrophy, diastolic dysfunction, myocardial stiffness, cardiac fibrosis, hypertension, nephropathy and sudden death. There is no appropriate animal model for HFpEF. The Alport Col4a3
-/-
mouse, a model of nephropathy, hypertension and early death, develops a cardiovascular pathology that is yet to be well characterized. We elected to analyze the cardiovascular pathology of the Alport mouse and investigate any commonalities with HFpEF. Male Alport and wild type (WT) littermates of mixed background at 2 months of age were subjected to echocardiographic and 2D speckle tracking analyses and heart tissues were used for histopathological examinations (N=6 mice per group). Circulating Galectin-3, a marker of HFpEF, was measured by Elisa in plasma samples. Data are shown as mean±SEM. Normalized heart weight increased in Alport relative to WT mice - p<0.01, indicative of cardiac hypertrophy. Consistently, echocardiography showed interventricular septum (IVS) thickening -p<0.05. Reduced stroke volume p<0.01, and impaired global longitudinal and circumferential strain (GLS and GCS) indicated systolic dysfunction in Alport mice. No significant reduction in LVEF was observed. Alport mice developed diastolic dysfunction evidenced by a prolonged Isovolumetric relaxation time -P<0.05, and a reduced E/A, a marker of LV relaxation and stiffness -p<0.01. Elevated LV filling pressure and pulmonary artery wedge pressure were demonstrated by an increase in E/E’ - p<0.01. Galectin-3 increased in Alport relative to WT plasma (P<0.01). Alport hearts had more Fibronectin protein - P<0.05 and increased number of fibroblasts with “activated” phenotype as demonstrated by increased mass of rough endoplasmic reticulum in EM cross sections. Our study suggests that the cardiovascular pathologies of the Alport mouse are similar to HFpEF, specifically preserved ejection fraction, diastolic dysfunction, hypertension, early death and cardiac stiffness and fibrosis. Further study of this multi-factorial pathology may render the Alport mouse as a useful novel model for HFpEF.