Immunohistochemical analysis of MMP-9 and COX-2 expression in carotid atherosclerotic plaques among patients undergoing carotid endarterectomy: A prospective study

Abstract

Background: Matrix metalloproteinase-9 protein (MMP-9) and cyclooxygenase-2 (COX-2) proteins may have a role in remodelling of atherosclerotic plaques. We analysed and compared the radiological, histological and immunohistochemical characteristics of carotid atherosclerotic plaques between symptomatic and asymptomatic patients who underwent carotid endarterectomy (CEA).

Methods: This prospective single-blinded study included 31 patients (70 [64-75] years, 58% males, 42% symptomatic) who underwent CEA and a total of 155 carotid plaque sections that were analysed. Preoperative assessment and multimodality diagnostic imaging with magnetic resonance imaging (MRI) or computed tomography angiography (CTA), histological and immunohistochemical analyses of carotid plaques including the expression of MMP-9 and COX-2 proteins were performed.

Results: Symptomatic and asymptomatic patients did not significantly differ in respect to preoperative characteristics. Unstable plaques were detected in 12/13 (92.3%, p = 0.020) symptomatic patients using MRI or CTA. There was no perioperative mortality and perioperative outcomes were comparable in both groups. A significantly higher expression of MMP-9 in macrophages was observed among symptomatic patients (p = 0.020). ROC curve analysis showed statistically significant associations of both the higher intensity of COX-2 staining in CD68 PG-M1 positive macrophages (area under the curve [AUC]=0.701, p = 0.014) and higher MVD (AUC=0.821, p < 0.001) within the plaque with cerebrovascular symptoms. The expression of COX-2 and the intensity of COX-2 staining in macrophages within the unstable carotid plaques detected by preoperative MRI or CTA were significantly higher (76.1% vs. 40.0%, p = 0.038; 76.2% vs. 30.0%, p = 0.01, respectively).

Conclusions: Advanced non-invasive multimodality diagnostic imaging including MRI or CTA is reliable in differentiating unstable from stable carotid plaques. High expression of MMP-9 and COX-2 in macrophages within the symptomatic plaque is associated with increased risk of cerebrovascular complications.

Trial registration: This study has been registered at the ISRCTN registry (ID ISRCTN46536832), isrctn.org Identifier: https://www.isrctn.com/ISRCTN46536832.

Keywords: Atherosclerosis; Carotid endarterectomy; Matrix metalloproteinase; Multimodality diagnostic imaging; Unstable plaque; cyclooxygenase.