Secreted Protein Profiling of Human Aortic Smooth Muscle Cells Identifies Vascular Disease Associations

Abstract

BACKGROUND: Smooth muscle cells (SMCs), which make up the medial layer of arteries, are key cell types involved in cardiovascular disease, the leading cause of mortality and morbidity worldwide. In response to microenvironment alterations, SMCs dedifferentiate from a contractile to a synthetic phenotype characterized by an increased proliferation, migration, production of ECM (extracellular matrix) components, and decreased expression of SMC-specific contractile markers. These phenotypic changes result in vascular remodeling and contribute to the pathogenesis of cardiovascular disease, including coronary artery disease, stroke, hypertension, and aortic aneurysms. Here, we aim to identify the genetic variants that regulate ECM secretion in SMCs and predict the causal proteins associated with vascular disease–related loci identified in genome-wide association studies. METHODS: Using human aortic SMCs from 123 multiancestry healthy heart transplant donors, we collected the serum-free media in which the cells were cultured for 24 hours and conducted liquid chromatography–tandem mass spectrometry-based proteomic analysis of the conditioned media. RESULTS: We measured the abundance of 270 ECM and related proteins. Next, we performed protein quantitative trait locus mapping and identified 20 loci associated with secreted protein abundance in SMCs. We functionally annotated these loci using a colocalization approach. This approach prioritized the genetic variant rs6739323-A at the 2p22.3 locus, which is associated with lower expression of LTBP1 (latent-transforming growth factor beta-binding protein 1) in SMCs and atherosclerosis-prone areas of the aorta, and increased risk for SMC calcification. We found that LTBP1 expression is abundant in SMCs, and its expression at mRNA and protein levels was reduced in unstable and advanced atherosclerotic plaque lesions. CONCLUSIONS: Our results unravel the SMC proteome signature associated with vascular disorders, which may help identify potential therapeutic targets to accelerate the pathway to translation.

Enhanced vasorin signaling mitigates adverse cardiovascular remodeling

“…Increased proliferation of VSMCs is associated with various vascular remodeling processes and diseases, including age‐associated intimal thickening, atherosclerosis, and in‐stent restenosis. 5 , 27 , 35 , 36 , 37 , 38 One main factor contributing to phenotype switch of VSMCs from quiescent to proliferative is the activation of inflammatory signaling cascades, which lead to the downregulation of crucial contractile structural and cytoskeletal proteins. 4 , 5 , 23 , 27 In this context, the smooth muscle cell‐specific protein VASN is emerging as a novel regulator of VSMC proliferation and differentiation both in vitro and in vivo.…”

“… 5 , 27 , 35 , 36 , 37 , 38 One main factor contributing to phenotype switch of VSMCs from quiescent to proliferative is the activation of inflammatory signaling cascades, which lead to the downregulation of crucial contractile structural and cytoskeletal proteins. 4 , 5 , 23 , 27 In this context, the smooth muscle cell‐specific protein VASN is emerging as a novel regulator of VSMC proliferation and differentiation both in vitro and in vivo. 7 , 8 , 9 , 10 , 21 , 22 …”

“… 2 , 3 , 4 Indeed, the wall thickening, fibrosis, and calcification observed in the aging cardiovascular system lay the foundation for the development of cardiovascular stiffening and associated diseases. 2 , 3 , 4 , 5 , 6 …”