Loss of the Coronary Artery Disease Risk Gene LMOD1 in Vascular Smooth Muscle Cells Triggers Rapid-Onset Coronary Atherosclerosis

BACKGROUND: Atherosclerosis is the primary underlying cause of coronary artery disease. LMOD1 is a coronary artery disease risk gene whose role in coronary artery pathophysiology is unknown. Whole-body loss of Lmod1 causes a lethal neonatal visceral myopathy in mice, necessitating unique approaches for the study of vascular smooth muscle cell (VSMC) phenotypes. METHODS: Control mice ( Lmod1 WT carrying a Cre recombinase allele) and VSMC-restricted Lmod1 knockout mice ( Lmod1 SMKO ) were subjected to various atherogenic regimens. Atherosclerosis and LMOD1 (leiomodin 1) expression in mouse and human coronary arteries were assessed by histopathology and confocal immunofluorescence microscopy. Coronary arteries from Lmod1 WT and Lmod1 SMKO mice were analyzed with assorted stains and antibodies, immunogold lineage tracing, and spatial metabolomics. Aortic smooth muscle cells from Lmod1 WT and Lmod1 SMKO mice were subjected to lipid loading with or without lentivirus carrying wild-type or actin nucleation–deficient Lmod1 ( Lmod1 ND . Mice harboring an intronic deletion of Lmod1 or Lmod1 ND were engineered using clustered regularly interspaced short palindromic repeats. RESULTS: A lethal neonatal visceral myopathy occurred in Lmod1 SMKO mice using Myh11-CreER T2 , prohibiting further investigation. In contrast, Lmod1 SMKO mice generated with Itga8-CreER T2 survived and were therefore used in all subsequent studies. Under atherogenic conditions, Lmod1 SMKO mice displayed little vascular disease in several organs but developed diffuse, occlusive coronary atherosclerosis with fibrous caps. No such disease was observed in Lmod1 WT mice. Time-course studies documented lipid insudation and VSMC migration into the intima of coronary arteries of Lmod1 SMKO mice as early as 8 days after the regimen. Immunogold lineage tracing revealed that 46% of coronary plaque cells were of VSMC origin. Spatial metabolomics uncovered multiple lipid species within coronary atheromata of Lmod1 SMKO mice. In vitro studies demonstrated elevated lipid accumulation in Lmod1 SMKO VSMCs, which was rescued by viral-mediated Lmod1 WT or Lmod1 ND expression. An intronic deletion of Lmod1 , comprising a conserved orthologous sequence where the single nucleotide variant associated with coronary artery disease exists, showed attenuated LMOD1 expression. Heterozygous Lmod1 SMKO mice, with a comparable reduction in LMOD1, displayed no coronary artery disease. Similarly, VSMC-restricted expression of Lmod1 ND resulted in negligible coronary atherosclerosis. CONCLUSIONS: Under atherogenic conditions, Lmod1 SMKO mice present with rapid-onset coronary atherosclerosis. LMOD1 safeguards coronary homeostasis, apparently in an actin nucleation–independent manner.