Abstract 390: Human Aortic Valve Interstitial Cells Exhibit Decreased Cholesterol Efflux Associated with Hypo- α1-nascent HDL Particles

Objectives: High plasma levels of lipoprotein (a) (Lp(a)) are associated with increased risk of aortic valve stenosis. The purpose of this study was to determine ability of human aortic valve interstitial cells (HAVICs) to generate HDL particles from plasma of patients with high Lp(a), and understand the mechanism involved. Methods: HAVICs were isolated from consented participants and cultured in DMEM, 10% FBS, 5% glucose. ABCA1 proteins expression was tested in HAVICs lyses after detection by polyclonal anti-ABCA1 antibody. Cholesterol efflux was determined in HAVICs against HDL isolated by PEG from patients with aortic valve stenosis exhibiting mild or severe plasma Lp(a), compared to normolipidemic controls. FPLC and 2D-PAGGE were used to illustrate HDL profiles from these patients after incubation with HAVICs. Results: Our data showed abundant expression of ABCA1, and a significant decrease in HAVICs cholesterol efflux (5%, for 8h) in response to HDL from plasma of patients with high Lp(a) and aortic valve stenosis (mild 16±0.01%cpm, severe 23.4±0.21%cpm) compared to normolipidemic HDL (29.57cpm; P<0.01). This was consistent with FPLC profiles indicating a similar reduction in in cholesterol within nascent HDL (nHDL) when compared to nHDL generated from HDL isolated from plasma of normal controls. Importantly, we noticed a generation of smaller population of HDL particles formed following cholesterol efflux. Plasma from patient with aortic valve stenosis showed a distinct decrease in preβ- and α1-migrating HDL, but no in other α-migrating HDL particles, when compared to plasma from normolipidemic controls. We also observed a defect in α1-HDL in the nHDL generated from patient with high Lp(a) and aortic valve stenosis compared to nHDL from plasma of normal controls. Conclusion: These findings demonstrate a defect in HAVICs ABCA1 cholesterol removal associated a loss of α1 species of nHDL in patient with high Lp(a) and aortic valve stenosis. Therefore, the HAVICs cholesterol efflux defect associated with the elevated plasma Lp(a) may explain the pathological changes associated aortic valve calcification.