The Expression Of MMP-9 In Sudden Death Due To Dilated Cardiomyopathy

【Background】Sudden cardiac death plays an important role in study of forensic pathology. Dilated Cardiomyopathy (DCM), also known as congestive heart failure, is an important cause of occurrence of sudden cardiac death, and the age of onset is mostly between the ages of 20-50, which seriously threatens to human health. The major clinical manifestation about DCM is heart failure of unknown reason. With the progress of the disease it behaves as palpitation, fatigue, chest tightness, edema, shortness of breath, even dyspnea and other symptoms. As DCM has no specificity in clinical features, which resulted in that difficult to differentiated from coronary heart disease and other heart diseases (such as ischemic cardiomyopathy (ICM)) in diagnose.Previous studies deem that DCM is developed from viral myocarditis [2-3], autoimmune disorders and viral infection are main pathogenis of Dilated Cardiomyopathy. In pathomorphology, DCM represents as heart weight increased as well as volume, which can reaching 500-800g or even more. The diagnostic criteria in male exceed 350g and in female greater than 300g. The left and right atrium and the two ventricular all have dilation ,and some ventricular walls are slightly thicker or normal (eccentric hypertrophy), walls of the apex of heart has a blunt rounded ,mitral and tricuspid valves can cause incompetence because of ventricular distension, bilateral endocardium may thickening, scarring and so on.In the case of the practice of forensic pathology examination, through the comprehensive and system of anatomy, and ruled out the mechanical damage, choking, and other causes of sudden death , DCM are not rare case, its diagnosis mainly based on morphological changes of the heart. But there are still some cases, no significant change in heart weight, its ventricular walls are slightly thicker or normal, and mainly behaves as atrial and ventricular expansion, due to lack of clear diagnostic criteria, after exclusion of other causes of sudden death can diagnosed as DCM . So can cause disputes as lack of convincing, more easily bring questions that the cause of death is unknown, the mechanism is unclear. Myocardial fibrosis is the pathological changes of DCM develops to a certain stage, which will lead myocardial remodeling , and ultimately lead to sudden death from acute respiratory and circulatory failure as systolic dysfunction. Therefore, the formation mechanism of myocardial fibrosis is the most important study in research of dilated cardiomyopathy.The formation mechanism of myocardial fibrosis is complicated, there are many systems involved in the metabolism and degradation of collagen, the current mechanism is relatively clear with AngⅡ-BK system, ET-NO system, platelet-derived growth factor (PDGF) and thromboxane (TXA2) - PGI2 system [5-7], other studies have reported its occurrence, development and TGF-β1 pathway and abnormal expression of MMPs.Matrix metalloproteinase system (MMPs) have identified 26 members , name as MMPs1-26, and named from its high dependence on metal ions in activation process. MMPs-9 is one member of the metalloproteinase (MMPs) family, mainly involved in degradation of gelatin andⅠ,Ⅱ,Ⅱ,Ⅱ,Ⅱcollagen, which are main components of myocardial interstitial. While imbalance of collagen synthesis and metabolic leading to myocardial fibrosis, that is the ultimate reason of heart function in patients of dilated cardiomyopathy. So there is necessary link between MMP-9 and sudden death from dilated cardiomyopathy . This study from the perspective of forensic pathology, analysis expression changes of MMP-9 between sudden death of dilated cardiomyopathy and other causes. Aims at exploring whether there is correlation between MMP-9 and myocardial fibrosis, ventricular remodeling and sudden death of dilated cardiomyopathy and the correlation degree. And expecting to provide information to forensic pathological diagnosis of this kind of sudden death .【purpose】By the application of Masson staining and MMP-9 immunohistochemical staining to the DCM group with sudden death and the control group, observing the degree of myocardial fibrosis and the expression of MMP-9 and comparing with the control group. Through probing the differences of above-mentioned indicators about different causes of death , aims to providing information to forensic pathological diagnosis of this kind of sudden death .【Materials and methods】All samples were forensic autopsy and inspection cases of 2003-2009 from the Department of Forensic Medicine Department of Pathology, Tongji Medical College, Huazhong University of Science and Technology. According to different diagnosis of death screening two groups, which are the experimental group and control group. Experimental group has 7 patients, its inclusion criteria is that the first cause of sudden death cases is dilated cardiomyopathy. While the control group has 21 cases, including seperately seven cases from coronary heart disease death group, carbon monoxide poisoning and injury death group, its inclusion criteria are cases that have specific diagnosis and no competition about death cause.Conventional drawning, producing, HE staining, and observing under the microscope whether it have the following pathological changes, cardiac muscle fibers thick, myocardial interstitial fibrosis, interstitial infiltration of inflammatory cells. Conventional drawning, producing, Masson trichrome staining , and observing contents of myocardial interstitial collagen fiber.Immunohistochemical staining to observe expression of MMP-9. After image analysis of each group by micrographs, and calculated the values of AD and AOD respectively. All data were statistically treated with SPSS16.0 package.【Result】1.From HE staining of the experimental group, we can see all the 7 cases have cardiac muscle fiber s hypertrophy or atrophy and interstitial myocardial fibrosis, 4 cases have myocardial interstitial infiltration of inflammatory cells, of which 1 case has myocardial fiber degeneration. The HE staining detail results of control groups are in Table 2.2.By Masson staining ,in experimental group and coronary heart disease death group, myocardial interstitial showed a different degree of blue dye (shown positive). CO poisoning and injury death group showed .only a small range of blue dye Or no blue dye. The color intensity and size of the two groups were significantly different, has statistical significance (P <0.05).3.After MMP-9 immunohistochemical staining of myocardium, in DCM sudden death group myocardial hyalomitome showed a varying degrees of brown-yellow granules (shown positive), while in the control group of SCD group apart myocardial hyalomitome showed brown particles, and in CO poisoning group and injury death group only one case showed light brown particles. By statistical analysis about values of AOD and AD that have positive products , the experimental group (DCM sudden death group) and every control group (group of sudden coronary death, CO poisoning and injury death group), there were significant difference ,which means has statistical Significance (P <0.05).4.In the DCM sudden death group, do correlation analysis of AOD values and AD values between Masson positive products and MMP-9 positive products . We get a conclusion that MMP-9 expression and AOD and AD values of Masson-positive product have significantly positive correlation(r = 0.745 , 0.638, P <0.05).【Conclusion】These results suggest that, myocardial cytoplasm of DCM all have different levels of MMP-9 expression, cardiac tissue have different levels of myocardial fibrosis. And the expression of MMP-9 of DCM sudden death myocardium has positive correlation with the extent of myocardial fibrosis .This study confirms that by the comprehensive application of immunohistochemistry and image analysis to qualitative and quantitative of MMP-9,which approving reference about diagnosis of sudden death cases from dilated cardiomyopathy in forensic pathological diagnosis.