| 【Background】Arrhythmogenic cardiomyopathy(ACM), one of primary cardiomyopathies, is a threat to peoples’ life and health. It was once named as “arrhythmogenic right ventricular cardiomyopathy/dysplasia”. Recently, researchers gradually found that the disease predominantly affects left ventricular and biventricular, so they proposed the nomenclature of “arrhythmogenic cardiomyopathy”(ACM). The prevalence is estimated between 1:1000 and 1:5000, and accounts for about 25% of sudden cardiac deaths in patients who were less than 30 years old. The pathological feature of ACM is myocardial degeneration with progressive fibrofatty replacement. It is not only the common cause of heart transplantation in patients with end-stage heart failure, but also the main cause of sudden cardiac deaths especially in young athletes.ACM is a disease associated with gene mutations encoding desmosomal proteins, which include desmocollin2(DSC2), desmoglein2(DSG2), desmoplakin(DSP), plakoglobin/gama-catenin(PKG) and plakophilin2(PKP2). Besides these five desmosomal proteins, there are also gap junctions(eg: Connexin43, Cx43) and adherence junctions(eg: N-cadherin) located in the intercalated disc. Many researchers use the cellular and animal models to explore the mechanisms of ACM. In the PKG knock-out mouse, the canonical Wnt signaling pathway is down-regulated to reduce the adiposegenic gene expression; therefore the β-catenin signaling is increased. In the DSP knock-out mouse, PKG is translocated to the cellular nuclear to promote adipose formation. However, the previous studies are restricted to the cellular and animal levels because of limited human samples, and the studies of sudden deaths and heart transplantation about ACM are very rare.【Objective】1. To compare the contents of fatty, fibrosis and residual myocyte in the epicardium, midzone and endocardium in ACM and non-ACM groups; and assess the pathological changes and the contents of different tissues. To investigate the PKG, PKP2, DSP, DSC2, DSG2, Cx43 and N-cadherin expressions in ACM group, and to find out the remodeling intercalated disc proteins in ACM group.2. To compare ACM group with implantable cardioverter defibrillator and the group without ICD(ICD-ACM and Non-ICD-ACM), and to analysis the PKG, PKP2, Cx43 and N-cadherin expressions, and to explore the underlying basis for malignant ventricular arrhythmia and provide guidlines for preventing malignant ventricular arrhythmia.【Methods】1. Eight cases of sudden deaths due to ACM and other twenty-three sudden deaths due to Non-ACM(eight patients with dilated cardiomyopathy, eight with hypertrophic cardiomyopathy and seven with non-cardiac sudden deaths) were selected from the Department of Forensic Pathology, Tongji Medical College, Huazhong University of Science and Technology. H&E and masson staining were performed to calculate the residual myocyte, fibrosis and fatty contents. Furthermore, immunohistochemistry stain was performed in eight ACM sudden deaths and seven non-cardiac deaths. Then the semi-quantitative and statistical analysis was carried out.2. Six ICD-ACM, six Non-ICD-ACM transplanted hearts and six donor hearts were selected from the Fuwai Hospital in Beijing. Use second-generation sequencing technology to perform whole genome sequencing. H&E and masson staining were performed to assess the residual myocyte, fibrosis and fatty contents. Then the immunohistochemical and western blot analysis were performed to measure PKG, PKP2, Cx43 and N-cadherin expressions.【Results】1. Eight cases of sudden deaths due to ACM include six females(75%; 26-57 years old; average 46.3 ± 10.8 years old) and two males(25%; 23-46 years old; average 34.5 ± 16.3 years old). Six deaths(75%) occurred between 40 and 60 years of age. The deaths occurred during work(3 cases, 37.5%), sleep(3 cases, 37.5%), childbirth(1 case, 12.5%), and emotional stress(1 case, 12.5%). One patient(12.5%) had a history of syncopal episodes. The heart weight ranges from 240 g to 560g(415.0 ± 106.2) g, and 6 cases(75%) had cardiomegaly. The left ventricular(LV) thickness ranges from 10 mm to 17 mm(13.8 ± 2.5mm), and half of them had LV hypertrophy(≥15mm). The right ventricular(RV) thickness ranges from 1 mm to 6 mm(3.4 ± 1.4 mm). 6 cases(75%) were restricted to the right ventricle, with biventricular subtype in the remaining cases. Chamber enlargemnet was seen in 7(87.5%) patients. Fatty pattern was seen in 6 cases(75%), and fibrofatty pattern was seen in 2 cases(25%). Transmural RV fatty infiltration was seen in 25% of patients. The semi-quantitative results of ACM group showed, A. Compared with the controls, the PKG, PKP2, DSP, DSG2, DSC2 and N-cadherin expressions were comparable in ACM group, but Cx43 expression was decreased. B. Cx43 signals were decreased in the ACM-sudden deaths, 6 cases(75%) showed decreased PKG signals, 3 cases(37.5%) showed decreased DSP, 1 case(12.5%) had decreased DSG2 or DSC2 signals.C. N-cadherin and PKP2 expressions were normal. In the controls, PKG, PKP2, DSP, DSG2, DSC2, Cx43 and N-cadherin were uniformly located in intercalated disc and showed strong positive signals.2. Twelve ACM patients(Six patients with ICD and six patients without ICD, ICD-ACM and Non-ICD-ACM) with heart transplantations conform to the 2010 Task Force Criteria. The age distribution, the disease-transplantation interval time and cardiac function and the incidence of gene mutations were comparable in two groups. The residual myocyte, fibrosis and fat contents were comparable in two groups. In the controls, PKG, PKP2, N-cadherin and Cx43 were uniformly located in the intercalated disc. The semi-quantitative immunohistochemical analysis showed, A. Cx43 expression in ICD-ACM patients was lower than the control group, and the expression in Non-ICD-ACM group was similar to the controls. B. The PKP2 expressions in ICD-ACM and Non-ICD-ACM groups were both reduced. C. The PKG and N-cadherin expressions had no difference between three groups. The western blotting results were similar to immunohistochemical analysis.【Conclusion】1. Most sudden deaths due to ACM occur in the asymptomatic patients during sleep and non-strenuous activities. The common pathological change of sudden deaths was right ventricular fatty replacement. The right ventricular midzone was more suitable for describing the morphological changes in patients with ACM. Reduced PKG signal was helpful to diagnose ACM. Cx43 remodeling might be related with malignant ventricular arrhythmia.2. The malignant ventricular arrhythmia had no relation with the degree of fibrofatty changes.Cx43 remodeling might be the predictive indicator of lethal ventricular arrhythmia. |
