A component-by-component characterisation of high-risk atherosclerotic plaques by multiphoton microscopic imaging

Specific matrix metalloproteinases and calcification factors are associated with the vulnerability of human carotid plaque

The rupture of atherosclerotic plaque provokes the majority of acute cerebrovascular events. Studies have demonstrated that various matrix metalloproteinases (MMPs) may promote atherosclerotic plaque progression and rupture. However, results have been incongruous and the mechanisms of this remain obscured. Therefore, in the current study, carotid plaques were characterized by assessing the levels of MMPs and calcification factors, and evaluating their association with plaque vulnerability. Human carotid plaques were obtained from carotid endarterectomies, and classified into stable and vulnerable groups by ultrasonography and histological analyses. The mRNA and protein levels of MMPs, vascular endothelial growth factor (VEGF), bone sialoprotein 2 (BSP) and osteopontin were investigated by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. Immunohistochemistry was used to localize MMP-2 and MMP-14 in stable and vulnerable plaques. The activation of various associated signaling pathways was also investigated using western blotting. The mRNA levels of MMP-2, -7, -9 and -14 were elevated in vulnerable plaques, among which expression of MMP-2 and -14 were the highest. Consistent with the mRNA levels, the protein levels of MMP-2 and -14 were also elevated. Immunohistochemistry also demonstrated positive staining of MMP-2 and MMP-14 in vulnerable plaques. Factors that indicate neovascularization and calcification, including VEGF and BSP, were concurrently elevated in vulnerable plaques. In addition, the protein levels of extracellular regulated kinase (ERK) and protein kinase C (PKC) were upregulated in vulnerable plaques. The current study provides novel insights into the MMP profiles of vulnerability plaques, and may assist in the development of novel methods for the diagnosis of plaque vulnerability and the prevention of plaque rupture.