ADAMTS7 promotes smooth muscle foam cell expansion in atherosclerosis
Human genetic studies have repeatedly associated ADAMTS7 with atherosclerotic cardiovascular disease. Subsequent investigations in mice demonstrated that ADAMTS7 is proatherogenic and induced in response to vascular injury and that the proatherogenicity of ADAMTS7, a secreted protein, is due to its catalytic activity. However, the cell-specific mechanisms governing ADAMTS7 proatherogenicity remain unclear. To determine which vascular cell types express ADAMTS7, we interrogated single-cell RNA sequencing of human carotid atherosclerosis and found ADAMTS7 expression in smooth muscle cells (SMCs), endothelial cells (ECs), and fibroblasts. We subsequently created SMC- and EC-specific Adamts7 conditional knockout and transgenic mice. Conditional knockout of Adamts7 in either cell type is insufficient to reduce atherosclerosis, whereas transgenic induction in either cell type increases atherosclerosis. In SMC transgenic mice, this increase coincides with an expansion of lipid-laden SMC foam cells and decreased fibrous cap formation. RNA-sequencing in SMCs revealed an upregulation of lipid uptake genes typically assigned to macrophages. Subsequent experiments demonstrated that ADAMTS7 increases SMC oxLDL uptake through increased CD36 levels. Furthermore, Cd36 expression is increased due to increased levels of PU.1, a transcription factor typically associated with myeloid fate determination. In summary, Adamts7 expression in either SMCs or ECs promotes SMC foam cell formation and atherosclerosis. In SMCs, ADAMTS7 promotes oxLDL uptake via increased PU.1 and Cd36 expression, thereby increasing SMC foam cell formation and atherosclerosis. Overall design: Primary vascular smooth muscle cells collected from aorta of 8 week old male mice of either wild type or Myh11-Cre-ERT2 with Adamts7 overexpression