Abstract 199: Conditional Inactivation Of Lysyl Oxidase In Smooth Muscle Cells Reduces Atherosclerosis Burden And Plaque Calcification In Hyperlipidemic Mice Through Suppression Of The β-catenin/tcf4 Signaling Axis.

Abstract

Introduction: In atherosclerosis development and complications, the importance of lysyl oxidase (LOX), a copper-dependent amino-oxidase that crosslinks collagen and elastin and controls gene expression, is not well established. Hypothesis: Inactivation of LOX in smooth muscle cells (SMC) decreases atherosclerosis burden and plaque calcification in hyperlipidemic mice. Methods: qRT-PCR, Western blot, and scRNAseq demonstrated the loss of Lox gene expression in SMC of ApoE conditional mice (Lox f/f Myh11-CreERT2 ApoE-/-) but not in littermate control animals after tamoxifen injections. Surprisingly, vascular loss of LOX did not increase the risk of aneurysms nor affected the aorta's stiffness. However, it reduced atherosclerosis burden with respect to control mice (13±2 versus 23±1%, p < 0.01) after 16 weeks of high fat diet (HFD). There was also a significant reduction in calcium deposition (5±0.4 versus11.8±3, p < 0.05) within the plaque of LOX knockout mice versus control. Aortic whole genome transcriptomic analysis revealed a positive correlation between Lox gene expression and Frizzled-related protein 3 ( Frzb ), a biphasic modulator of Wnt signaling that facilitates the association of β-catenin with TCF4 in the nucleus. scRNAseq analysis confirmed the downregulation of Bmp2 and Myc , both β-catenin/TCF4 regulated genes, in SMC following gene deletion of Lox and 8 weeks of HFD. LOX knockout SMCs also had lower expression of Frzb and were more resistant to osteoblastic transformation in vitro. Conclusions: Vascular inactivation of LOX protects the vasculature from the proatherogenic effects of FRZB in SMCs.