| Background and Purpose Initiation and development of atherosclerosis is a chronic process that is affected by various factors. The stableness of the patient was associated with not only the extent of luminal loss, but also the activeness of plaque inflammation. Inflammatory cells and cytokines play a part in the pathological process of atherosclerosis. Matrix metalloproteinase 9 (MMP-9) plays important roles in the process of atherosclerosis. By degrading the collagen, decreasing the strength of the fibrotic cap, MMP-9 decreases the strength of plaque stableness, and leads to acute coronary syndrome.The present study was designed to investigate the expression of MMP-9 in human atherosclerotic tissues, and the effect of IGF-1, TNF-α, IL-1β, MCP-1 and statins on the expression of MMP-9.Methods: Atherosclerotic tissues were obtained during elective open-chest surgeries, and characterized by pathologic examination to be atherosclerotic. The control arteries were obtained from autopsy, and confirmed to be normal aortic tissues. All samples were fixed in 4% polyformaldehyde for 12h, routinely dehydrated, embedded and sliced. HE staining and standard immunohistochemistry.Human vascular smooth muscle cells were obtained in open chest surgery. The cells were isolated, cultured, harvested, cryopreserved and thawed for subsequent experiments. The effects of TNF-αon MMP-9 and ET-1 expression was determined by RT-PCR and Western blot. The effects of pitvastatin along with TNF-αwas also assessed.Immunohistochemistry observation: Each slice was observed by 2 pathologists in a double-blinded manner. The criteria of positive reaction was: 10 non-crossed fields (×400) were chosen randomly. Negative (score:0) was defined as <25% positive cells, weak positive(score:1) was defined as 26%～50% positive cells, moderate positive (score:2)was defined as 51-75% positive cells, and strong positive(score:3) was defined as 76-100% positive cells.Interpretation of RT-PCR results: Positive means the concomitant expression of internal marker and target gene strips. Negative was defined where only the internal marker shows.Western blot results: Grey scale scanning was performed to all strips. The results were analyzed by Image Tool Version 2.0 software. The level of each protein was determined by the ratio of darkness of each protein's strip to the darkness ofβ-actin scale.Results: There were no obvious expression of MMP–9,MCP-1,IL-1βwithin the normal abdominal aortic vessels, and weak to fair positive expression of TNF-αand IGF-1. MMP-9 was primarily expressed in inflammatory cells infiltrated areas in the intima and media, in a continuous or flake manner. MCP-1 was expressed in the focus of inflammatory cells, most of positively stained cells were fibroblasts or macrophages. IGF-1 cells was weakly stained or negative in the arterial wall. IL-1βand TNF-αwere not expressed in the normal aorta, with occasional expression in the vascular smooth muscle cells. IL-1βwas primarily expressed in the endothelium and proliferated smooth muscle cells.TNF-αwas primarily expressed in the vessel media and adventitia, and areas infiltrated by inflammatory cells including macrophages.TNF-αsignificantly increases the expression of MMP-9 in the smooth muscle cells in a dose-dependent manner(P<0.01). Pitvastatin could antagonize the effects of TNF-α(P<0.01).Conclusions: There are expression of MMP-9,TNF-α,MCP-1,IGF-1 and IL-1βin the human atherosclerotic tissues, but the distributions of these molecules are not the same. TNF-αincreases the expression of MMP-9, while pitvastatin could antagonize the effects of TNF-α. The results indicate that the pathologic basis of atherosclerotic plaque instability was the interaction and imbalance of different cytokines, and statins may play a role in the treatment of atherosclerosis by regulating the interactions of cytokines.
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