Abstract 635: ESAM Deficiency-related Coronary Microvascular Dysfunction Contributes To Left Ventricle Diastolic Dysfunction In HFpEF

Abstract

Coronary microvascular dysfunction and vascular inflammation have been linked to heart failure with preserved ejection fraction (HFpEF), but the underlying molecular mechanisms remain incompletely understood. Endothelial cell-selective adhesion molecule (ESAM) has been recently implicated as one of the biomarkers for heart failure. The biological function of ESAM is to regulate inflammatory cell adhesion, permeability and angiogenesis. Here, we examined the mechanistic role of ESAM in contributing left ventricle (LV) diastolic dysfunction in a mouse model of human HFpEF. We employed wild type (WT) mice and mice with homozygous genetic deficiency of ESAM (ESAM -/- ), with or without uninephrectomy and aldosterone infusion (UNX-Aldo, for 4-week). Using echocardiography, we found that WT mice with UNX-Aldo develop LV diastolic dysfunction, as indicated by a significantly reduced E/A ratio (E=early, A=late mitral inflow peak velocities), increased E/e’ ratio, isovolumic relaxation time (IVRT) and E wave deceleration time. UNX-Aldo significantly increased the serum soluble ESAM levels, along with elevated MMP2/9 levels, as potential mediators of ESAM ectodomain shedding. When compared to WT, ESAM -/- mice with UNX-Aldo displayed significant worsening of LV diastolic dysfunction, as indicated by increased IVRT, and the development of pulmonary edema and fibrosis. An unbiased automated tracing and 3D reconstruction of coronary microvasculature revealed that ESAM -/- mice had a significantly reduced coronary microvascular density. Arteries of ESAM -/- mice exhibited impaired endothelial sprouting and in cultured endothelial cells siRNA-mediated ESAM knockdown reduced tube formation. Thus, we propose that ESAM plays a role in the proper myocardial vascularization, hence the maintenance of myocardial perfusion. Deficiency, or augmented ectodomain shedding of ESAM impairs myocardial vascularization, whereby it contributes to the development of LV diastolic dysfunction, and could have mechanistic and diagnostic implications in human HFpEF.