Assessment of MMP-9, TIMP-1, and COX-2 in normal tissue and in advanced symptomatic and asymptomatic carotid plaques

Abstract

BackgroundMature carotid plaques are complex structures, and their histological classification is challenging. The carotid plaques of asymptomatic and symptomatic patients could exhibit identical histological components.ObjectivesTo investigate whether matrix metalloproteinase 9 (MMP-9), tissue inhibitor of MMP (TIMP), and cyclooxygenase-2 (COX-2) have different expression levels in advanced symptomatic carotid plaques, asymptomatic carotid plaques, and normal tissue.MethodsThirty patients admitted for carotid endarterectomy were selected. Each patient was assigned preoperatively to one of two groups: group I consisted of symptomatic patients (n = 16, 12 males, mean age 66.7 ± 6.8 years), and group II consisted of asymptomatic patients (n = 14, 8 males, mean age 67.6 ± 6.81 years). Nine normal carotid arteries were used as control. Tissue specimens were analyzed for fibromuscular, lipid and calcium contents. The expressions of MMP-9, TIMP-1 and COX-2 in each plaque were quantified.ResultsFifty-eight percent of all carotid plaques were classified as Type VI according to the American Heart Association Committee on Vascular Lesions. The control carotid arteries all were classified as Type III. The median percentage of fibromuscular tissue was significantly greater in group II compared to group I (p < 0.05). The median percentage of lipid tissue had a tendency to be greater in group I than in group II (p = 0.057). The percentages of calcification were similar among the two groups. MMP-9 protein expression levels were significantly higher in group II and in the control group when compared with group I (p < 0.001). TIMP-1 expression levels were significantly higher in the control group and in group II when compared to group I, with statistical difference between control group and group I (p = 0.010). COX-2 expression levels did not differ among groups. There was no statistical correlation between MMP-9, COX-2, and TIMP-1 levels and fibrous tissue.ConclusionsMMP-9 and TIMP-1 are present in all stages of atherosclerotic plaque progression, from normal tissue to advanced lesions. When sections of a plaque are analyzed without preselection, MMP-9 concentration is higher in normal tissues and asymptomatic surgical specimens than in symptomatic specimens, and TIMP-1 concentration is higher in normal tissue than in symptomatic specimens.

Molecular imaging of matrix metalloproteinases in atherosclerotic plaques

“…In a normal artery, pro-MMP2, TIMP-1 and TIMP-2 are well detectable and appropriately balanced. Within human atherosclerotic plaques, MMP control systems might be pathologically down regulated (9). In particular, TIMP-1 intraplaque expression has been shown as reduced in symptomatic plaque speci-mens (9).…”

“…Within human atherosclerotic plaques, MMP control systems might be pathologically down regulated (9). In particular, TIMP-1 intraplaque expression has been shown as reduced in symptomatic plaque speci-mens (9). Conversely, TIMP-1 serum levels were not altered in vulnerable patients with acute myocardial infarction (10) or ischaemic stroke (11), when compared with asymptomatic controls.…”

Videodensitometric analysis of advanced carotid plaque: correlation with MMP-9 and TIMP-1 expression

“…In the present study, we correlated parameters from videodensitometric analyses with protein expression in plaques. In our previous study [ 2 ], we determined that expression levels of MMP-9 and TIMP-1 were higher in surgical specimens from asymptomatic patients, which corresponded to more stable chronic plaques. In that study, the entire section of plaque was analyzed and the total expression of each protein was determined.…”

“…Specific regions of each plaque were not preselected for this analysis. The section was analyzed entirely, as described previously [ 2 ]. Briefly, carotid samples (n = 30) were minced and homogenized in lysis buffer containing PBS (pH 7.2), 0.5% Triton X-100, 0.1% SDS, 0.5% sodium deoxycholate, and a protease inhibitor cocktail (Roche) at 4°C.…”

“…It is not currently possible to predict whether a carotid plaque will produce symptoms or when symptoms will occur [ 1 ]. The American Heart Association classification of human atherosclerotic lesions considers the presence or absence of different tissue components in plaques, but does not account for the proportion of each component or its location in the plaques [ 2 ]. Because plaques are dynamic structures, changing through processes of stabilization and destabilization, the locations and the proportions of different plaque components are constantly being modified.…”