Proteomic analysis of extracellular matrix of human atherosclerotic plaques shows marked changes between plaque types

•Extracellular matrix (ECM) components may differ between atherosclerotic plaques and result in plaque instability.•4498 proteins including 354 ECM species were detected from symptomatic patients using a new single-step LC-MS method.•Multidimensional scaling analysis and hierarchical clustering indicate two clusters that correlate with clinical data.•714 proteins showed differential abundances between plaque groups.•Unstable plaques were enriched in proteins involved in inflammation, ECM remodelling, and protein degradation.•Stable plaques contained higher levels of ECM structural and mineralization proteins.