Proteomics and Ex Vivo Plaque Culture Identify the Insulin-Like Growth Factor Axis as a Regulator of Carotid Plaque Stability
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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 mor-phologically 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 receptor was more abundant in type A. IGF-1 treatment of ex vivo plaques decreased matrix metalloprotein 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, re-veals the IGF axis as a potential regulator of human atherosclerotic plaque stability.
CLINICAL RELEVANCE
The protein composition of unstable carotid artery plaques differs from that of stable ones, which may explain their varying tendency to rupture. Components of the insulin-like growth factor (IGF) axis are more abundant in atherosclerotic plaques than in healthy tissue, and are more abundant in stable compared to unstable plaque morphology, suggesting a protective role of these proteins against plaque rupture. To investigate this, we treated plaques ex vivo with IGF-1. This data indicates that manipulating the IGF axis may promote plaque stability, with potential clinical relevance in prevention of plaque rupture.
ARTICLE HIGHLIGHTS
Type of Research
Human study
Key Findings
Proteomic analysis of 76 carotid ath-erosclerotic plaques and 8 superior thyroid artery controls identified the insulin-growth factor (IGF) axis as potential regulators of plaque stability. Ex vivo cul-ture and IGF-1 treatment of 11 symptomatic carotid plaques induced proteome changes, compared to 11 controls, consistent with features of plaque stabiliza-tion.
Take home Message
The insulin-like growth factor axis is a potential regulator of carotid atherosclerotic plaque stability, as revealed by proteomic analysis and ex vivo plaque culture.
