Proteomics and ex vivo plaque culture identify the insulin-like growth factor axis as a potential regulator of matrix remodelling in carotid plaques

BACKGROUND AND AIMS: Rupture of carotid atherosclerotic plaques is a significant cause of stroke. We have previously analyzed 21 plaques by mass spectrometry and reported differing proteomic profiles between morphologically unstable (rupture-prone) and stable plaques. This expanded dataset includes additional carotid plaques as well as non-atherosclerotic arteries, allowing comparison with control tissue. Additionally, the role of insulin-like growth factor 1 (IGF-1) signaling in plaque stability was investigated with ex vivo cultured plaques. METHODS: Plaques (n = 76) and non-atherosclerotic superior thyroid artery segments (n = 8) were retrieved from carotid endarterectomies. Additionally, 22 plaques were cultured ex vivo for 22 days to examine IGF-1 signaling effects. Proteins were analyzed by liquid chromatography-mass spectrometry. RESULTS: Mass spectrometric proteome analysis identified three clusters associated with two different plaque phenotypes (type A and type B) and non-atherosclerotic arteries. 2608 proteins were differentially abundant in plaques compared to non-atherosclerotic arteries. 1315 proteins were differentially abundant between plaque types A and B. Proteins linked to IGF transport and binding, particularly IGF-binding proteins, were more abundant in plaques compared to non-atherosclerotic arteries, and in type B compared to type A plaques. IGF-1, IGF-2 and the IGF-1 receptor were more abundant in type B plaques, whereas the IGF-2 receptor was more abundant in type A. IGF-1 treatment of ex vivo plaques decreased matrix metalloproteinase 9 and increased collagen type XXI, consistent with increased plaque stability. CONCLUSIONS: Proteomic analyses of atherosclerotic plaques, and ex vivo plaques cultured with IGF-1, reveal the IGF axis as a potential regulator of human atherosclerotic plaque stability.