Altered expression balance of matrix metalloproteinases and their inhibitors in human carotid plaque disruption: Results of quantitative tissue analysis using real-time RT-PCR method

Background: The balance between degradation and synthesis of extracellular matrix determines its content in atherosclerotic tissue. To examine the role of expression balance of matrix metalloproteinases (MMPs) to their inhibitors, tissue inhibitors of metalloproteinases (TIMPs) and tissue factor pathway inhibitor-2 (TFPI-2) in the development and disruption of atherosclerotic plaque, these gene expressions in human carotid plaque were quantitatively determined by real-time reverse transcription (RT)-polymerase chain reaction (PCR) method. Methods: Total RNA for cDNA synthesis was extracted from tissues in 24 patients with carotid endarterectomy. The amounts of cDNAs for MMP-1, -2, -3 and -9, TFPI-2 and TIMP-1, -2 and -3 were determined by real-time RT-PCR method, and normalized with glutaraldehyde 3-dehydrogenase. Results: In plaques, the expression MMP-1 (1.53 ± 0.25, mean ± S.E.M.), MMP-3 (1.99 ± 0.59) and MMP-9 (2.00 ± 0.51) was augmented compared to those in the adjacent control regions (0.60 ± 0.16, 0.46 ± 0.18 and 0.58 ± 0.21, respectively, p < 0.05). The expression of TFPI-2 was lower in plaques (0.32 ± 0.08) than in controls (0.94 ± 0.23, p < 0.01). Although the expression of TIMP-1 was higher in plaques (1.28 ± 0.23) than in controls (0.81 ± 0.10, p < 0.05), the indices of MMP-1/TIMP-1, MMP-3/TIMP-3 and MMP-9/TIMP-1 were still significantly higher in plaques. Interestingly, MMP-9 and the resulting MMP-9/TIMP-1 balance in plaques with disruption were significantly higher (3.36 ± 1.52 and 1.66 ± 0.12, n = 11) than those in non-disrupted plaques (1.11 ± 0.52 and 0.76 ± 0.12, n = 13, p < 0.05). Conclusion: With the decreased expression of TFPI-2, upregulation of MMPs in atherosclerotic plaque was disproportional to that of TIMPs, suggesting that imbalanced degradation and synthesis of extracellular matrix persists in advanced lesions, particularly in plaques with disruption.