BACKGROUNDTransforming growth factor-beta (TGF-beta) and matrix metalloproteinases-9 (MMP-9) have been implicated in the pathogenesis of human atherosclerosis but their relationship during lesion progression are poorly understood. The objective of this study was to investigate the expression of MMP-9, TGF-beta1 and TGF-beta receptor I (TbetaR-I) in human atherosclerotic plaque and their relationship and plaque stability.

METHODSSpecimens of human coronary artery atherosclerotic plaques were obtained from 41 patients undergoing coronary endarterectomy, and were paraffin embedded, sectioned at 4 microm intervals then stained with haematoxylin and eosin. They were divided into stable (with no or only little lipid core) and unstable plaque groups (with lipid core size > 40%): the immunohistochemical staining were performed for MMP-9, TGF-beta1 and TbetaR-I.

RESULTSThe expression of MMP-9 in the unstable plaques was much higher than in the stable ones, but the expression of TGF-beta1 was higher in the stable plaques. There was no similar significant difference for TbetaR-I. Correlation analysis showed that there was a negative correlation between the expression of MMP-9 and TGF-beta1 (r = -0.332, P = 0.034 for average areal density; r = -0.373, P = 0.016 for average optical density).

CONCLUSIONSThere were close relationships between MMP-9, TGF-beta1 and plaque stability. Enhanced production of MMP-9 may participate in the formation of unstable plaque, while TGF-beta1 maybe an important stabilizing factor in preventing transition into an unstable plaque phenotype.