Proteomics and Ex Vivo Plaque Culture Identify the Insulin-Like Growth Factor Axis as a Regulator of Carotid Plaque Stability

Objective: Rupture of carotid atherosclerotic plaques leading to cerebral embolization, is a significant cause of stroke. We previously analyzed 21 plaques by mass spectrometry and reported that the proteomes of morphologically unstable (rupture-prone) and stable plaques are different. This dataset extends and includes non-atherosclerotic (thyroid) arteries to allow comparison with control tissue, and to investigate plaque stability using ex vivo plaques cultured. 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 the role of insulin-like growth factor-1 (IGF-1) signalling. Proteins were analyzed by liquid chromatography-mass spectrometry. Results: Mass spectrometric proteome analysis identified three protein clusters associated with morpho-logically unstable (type A) and stable (type B) plaques, as well as non-atherosclerotic arteries. 2,876 proteins were differentially abundant in plaques compared to non-atherosclerotic arteries. 1,415 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 re-ceptor was more abundant in type A. IGF-1 treatment of ex vivo plaques decreased matrix met-alloprotein 9 and increased collagen type XXI, consistent with a increased plaque stability. Conclusions: Proteomic analyses of atherosclerotic plaques, and ex vivo plaques cultured with IGF-1, reveals the IGF axis as a potential regulator of human atherosclerotic plaque stability.