Atherosclerosis is a chronic inflammatory disease with complex pathobiology and 
one of the most common causes of cardiovascular events. The process is 
characterized by complex vascular remodeling processes that require the actions 
of numerous proteins. The composition of atherosclerotic plaque is increasingly 
recognized as a major factor governing the occurrence of cardiovascular or 
neurological symptoms. To gain deeper insights into the composition of 
atherosclerotic plaques, we created quantitative proteome profiles of advanced 
plaque tissues of six male patients undergoing carotid endarterectomy for stroke 
prevention. Using a quantitative, data-independent proteome approach, we 
identified 4181 proteins with an average protein coverage of 45%. An analysis of 
the quantitative composition of the tissue revealed key players of vascular 
remodeling processes. Moreover, compared with proximal arterial tissue, 20 
proteins in mature plaques were enriched, whereas 52 proteins were found in 
lower quantities. Among the proteins with increased abundance were prominent 
extracellular matrix proteins such as biglycan and lumican, whereas cytoskeletal 
markers for contractile smooth muscle cells (SMCs) were decreased. Taken 
together, this study provides the most comprehensive quantitative assessment of 
mature human plaque tissue to date, which indicates a central role of SMCs in 
the structure of advanced atherosclerotic plaques.