Abstract 103: Smooth Muscle Cell Specific Overexpression Of Adamts7 Drives Atherosclerosis Development Through The Remodeling Of The Extracellular Matrix

Abstract

Genome-wide association studies in humans link ADAMTS7 with coronary artery disease. Subsequent studies in mice showed ADAMTS7 to be proatherogenic, as whole-body knockout (KO) reduced atherosclerosis independent of lipid-lowering. Further studies show that Adamts7 expression is temporarily induced in response to vascular injury, and Adamts7 KO reduces primary smooth muscle cell (SMC) migration ex vivo. However, both the mechanism through which ADAMTS7 influences atherosclerosis progression and the responsible cell type remain unclear. As ADAMTS7 is secreted, we sought to determine its cleavage targets. We generated an immortalized human SMC line with doxycycline-inducible expression of GFP or ADAMTS7. We analyzed conditioned media from these cells via terminal amine isotopic labeling of substrates (TAILS) proteomics. This method labels new protein N termini, enabling the identification of cleavage products. Overexpression of Adamts7 enriched extracellular matrix (ECM) peptides such as Col1a1, Col1a2, Col4a2, and fibronectin. Furthermore, KEGG analysis identified ECM receptor interaction and focal adhesion formation as highly enriched pathways in the dataset. These results suggest ADAMTS7 alters SMCs by modulating signaling between cell and ECM. To examine the cell type that confers the proatherogenic effects of Adamts7, we generated a conditional transgenic ADAMTS7 mouse on the Ldlr knockout background. Given previously described roles for ADAMTS7 in SMC migration and vascular reendothelialization, we crossed these mice to either the Tie2-Cre or Myh11-CreERT2 to overexpress ADAMTS7 in endothelial and SMCs respectively. We found >3-fold increase (p = 0.0002) in plaque burden by en face staining in overexpression of Adamts7 in SMCs compared to controls. In contrast, transgenic overexpression of Adamts7 in endothelial cells is embryonic or perinatally lethal (Chi-squared = 0.0018). In summary, our transgenic study affirms the proatherogenic effect of increased Adamts7 expression in SMCs in vivo. Furthermore, our TAILS data suggests a dynamic role of ADAMTS7 in cleaving ECM. These studies fill critical knowledge gaps in our understanding of ADAMTS7 biology and help inform potential therapeutic avenues to targeting this enzyme.