| Background: Acute myocardial infarction (AMI) can lead to malignant arrhythmia, low blood pressure shock and serious complications such as heart failure. The pathophysiological performance shows the weakening of the heart contraction, reduce compliance, in infarction and non-infarction ventricular zone structure, shape, size and function of change, that is, ventricular remodeling, thus affecting the patient's heart function and hemodynamics, and decided the cardiac events and long-term prognosis.The studies demonstrate that MMPs (matrix metalloproteinases, MMPs) play an important role in the cardiac remodeling after AMI. In rats, rabbits, pigs and other animal models of myocardial infarction, part of myocardial MMPs isozyme, especially MMP-9, increased the expression level and biological activity, thus changing the extracellular matrix, lowering left ventricular diastolic function and participating in ventricular remodeling. Therefore, the expression of MMP-9 and its regulatory mechanism after AMI have been becoming the focus of attention and study in recent years.CD147, also known as the extracellular MMP inducer (EMMPRIN), are diffusely distributed in the human tissues, participating in a variety of pathological and physiological process and playing a variety of functions. In cancer, rheumatoid arthritis and atherosclerosis plaque rupture, the expression of CD147 increased significantly. After AMI, the characteristic of CD147 expression and the relationship with MMPs are still unclear.Objective: This study is to observe the expression of CD147 and MMP-9 after AMI, through the establishment of rat model of AMI, and to further investigate the relationship between the expression of CD147 and MMP-9 after AMI and its biological functions during the ventricular remodeling. This study is divided into four parts.Methods and Results:1. Establishment of rat model of AMI:Methods 120 Healthy male Sprague-Dawley rats were randomly divided into 8 groups:(1)Sham group(n=15);(2)AMI4h group(n=15);(3)AMI12h group(n=15)(;4)AMI24h group(n=15)(;5)AMI3d group(n=15);(6)AMI1w group(n=15);(7)AMI2w group(n=15);(8)AMI4w group(n=15)。Anesthetized by 3% pentobarbital sodium(35 mg/ kg), AMI rats model was established by ligation of left anterior descending coronary artery (LAD);.The standardization of successful operation were the color of myocardial tissues turned to prunosus from bright red and the elevation of I , avL ST segment more than 0.2 mV and lasted more than 30 minutes.Sham group was operated as the AMI groups but not ligated the coronary artery. Results (1) The color of myocardial tissues turned to prunosus from bright red.The myocardial pulsation was weaken. (2) The I , avL ST segment elevated more than 0.2 mV and lasted more than 30 minutes. (3)The index of ventricle weight was increased at three days after AMI and lasting to four weeks. (4) It was showed from the morphology by the light microscope that myocardial destruction with focal infiltration of lymphocytes and polymorphonuclear leukocytes was evident in the left ventricular free wall of AMI 4 hours. Infiltration of inflammatory cells was more diffuse. (5) LVEDP was lasting increase and LVSP,±dp/dtmax were lasting decrease from 4 hours to 4 weeks after AMI. Sham group had no the changes.2. The relationship between the expression of MMP-9 and ventricular remodeling after AMI:Methods RT-PCR was performed in the non-myocardial infarction area of the rat AMI model, observing changes of MMP-9 expression at mRNA level and investigating the relationship of MMP-9 expression with heart function and the weight of left ventricle. Results (1) The MMP-9 mRNA expression in AMI had no significant difference with in Sham in four hour; However, in 12 hour , the MMP-9 mRNA expression in AMI significantly increased, reaching the peak in one week and keeping at this level for four weeks. (2) In the AMI group, there was a positive correlation between MMP-9 mRNA and LVEDP (r = 0.831, P <0.05), and a negative correlation between MMP-9 mRNA and LVSP (r=-0.802,P<0.05). (3) There was a positive correlation between the MMP-9 mRNA expression and the index of ventricle weight (r = 0.817, P <0.05).3. The study of CD147 expression in AMI rat model:Methods RT-PCR and Western blotting were performed in the non-myocardial infarction area of the rat AMI model, observing changes of CD147 expression at mRNA as well as protein level. 5 ml peripheral blood was extracted and monocytes were isolated, to observe the changes of CD147 mRNA expression in monocytes. Results (1) In the non-myocardial infarction area, the CD147 mRNA expression was increased in four hours, reaching the peak in one week and keeping at this level for two weeks, declining in four weeks; (2) In the non-myocardial infarction area, the CD147 protein expression was increased in twelve hours, reaching the peak in one week and keeping at this level for four weeks; (3) The expression of CD147 mRNA was lower in peripheral monocytes than in the non-myocardial infarction area, but the increasing trend was similar, there was a positive correlation between them (r = 0.981, P <0.01).4. The study of correlation between CD147 and MMP-9 in AMI rat modelMethods 5 ml peripheral blood was extracted from AMI rat in 24 hours and monocytes were isolated. The ventricles of 10 SD rats were dissected under sterile conditions and cardiac fibroblasts were isolated. Cardiac fibroblasts were co-cultured with monocytes in different ratios of 0.5:1, 1:1 and 2:1. The expression of MMP-9 mRNA was examined by real-time RT-PCR. The cardiac fibroblasts were co-cultured with monocytes in the ratio of 2:1 and 1μl/l,2μl/l and 4μl/l of CD147 monoclonal antibody was added to the system respectively. After 24 hours incubation, the expression of matrix metalloproteinase-9 mRNA was examined using real-time RT-PCR. Results (1)The expression of CD147 on monocytes was significantly increased in acute myocardial infarction rats(the rate of expression is 99.2% VS 60.1%, the average of fluorescence intensity is 289.3 VS 91.4, P < 0.05). (2)The expression of matrix metalloproteinase-9 mRNA was 0.52±0.11,0.71±0.13,0.83±0.10 respectively as cardiac fibroblasts were co-cultured with monocytes in different ratios of 0.5:1,1:1 and 2:1 (P<0.05). (3)The expression of matrix metalloproteinase-9 mRNA was 0.66±0.07,0.53±0.05,0.37±0.09 respectively when 1μl/l,2μl/l and 4μl/l CD147 monoclonal antibody was added to the system in which cardiac fibroblasts were co-cultured with monocytes in the ratio of 2:1 (P<0.05).Conclusions:1 The MMP-9 mRNA expression significantly increased in the non-myocardial infarction area of AMI model.2 In the non-myocardial infarction area of the rat AMI model, the CD147 expression significantly up-regulated at mRNA as well as protein level, and there was a positive correlation between the MMP-9 mRNA expression and the CD147 expression.3 CD147 is the important regulatory factor of regulating the expression of MMP-9 mRNA in the non-myocardial infarction area of AMI model.4 There is a positive correlation of CD147 mRNA expression between the peripheral monocytes and the non-myocardial infarction area, which can be used as a clinical indirect indicator to monitor the CD147 mRNA expression of myocardium.
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