Abstract Thu087: Sam68 Promotes Aortic Valve Calcification by Regulating Macrophage Lipophagy-Mediated Cholesterol Metabolic Reprogramming

Introduction: Calcific aortic valve disease (CAVD) is characterized by lipid deposition and inflammatory macrophage infiltration, yet the molecular mechanisms linking lipid metabolism to valvular calcification remain unclear. Hypothesis: This study investigates the role of Sam68, an RNA-binding protein, in Methods macrophage lipid homeostasis and its contribution to CAVD progression.Using an ApoE-/- mouse model of aortic valve calcification and human calcified aortic valves, we analyzed Sam68 expression via immunohistochemistry and single-cell RNA sequencing (scRNA-seq). Macrophage subsets were characterized, and lipid metabolism pathways were assessed through functional assays (ox-LDL uptake, cholesterol efflux, lipophagy). Results: Sam68 was upregulated in calcified valves, co-localizing with scar-associated macrophages (SAMs) and pro-inflammatory subsets (M1, Birc5+). scRNA-seq revealed Sam68 enrichment in pathways related to autophagy and lipid metabolism. Sam68 knockout enhanced lipid phagocytosis, reduced scavenger receptor (SR-A1/CD36/LOX-1) activation, and decreased ox-LDL uptake, thereby suppressing foam cell formation. It also promoted lysosomal-lipid droplet fusion (lipophagy) and reduced intracellular cholesterol ester accumulation. Conclusions: Sam68 exacerbates CAVD by impairing macrophage lipid clearance and promoting pro-inflammatory macrophage polarization. Targeting Sam68 may restore lipid homeostasis and mitigate valvular calcification, offering a novel therapeutic strategy for CAVD.