The Effect And Mechanism Of CAMR_85 Gene On Cardiac Hypertrophy And Remodeling In TAC-intervention Mice

According to the 2019 Summary of China Cardiovascular Health and Disease report,the prevalence and mortality of cardiovascular diseases are still rising,affected by unhealthy lifestyles or other diseases such as hypertension,hyperlipidemia and diabetes.The mortality rate of cardiovascular disease is much higher than that of other malignant diseases.As an adverse change process of adapting to stress state,pathological cardiac hypertrophy presented enlarged cardiomyocytes as well as apoptosis,tissue fibrosis and inflammation.Meanwhile,the gene-regulated cell proliferation,ion channel-mediated contraction coupling,intracellular and extracellular metabolic pathways which calcium-related proteins involved were changed.The above changes will lead to malignant arrhythmias and eventually lead to heart failure.Therefore,it is of great significance to explore the electrophysiological changes,histopathological changes and specific molecular mechanisms of calcium-related CAMR 85 transgenic mice in the process of cardiac hypertrophy and remodeling.In this study,CAMR?85(CAM?85)transgenic mice were used as experimental objects,and WT-129 mice as control.Through the intervention of transverse aortic constriction(TAC)in thoracic aortic stenosis,we explored the physiological and molecular changes of CAMR 85 gene under continuous overload pressure,as well as the mechanism of CAMR?85 gene in cardiac hypertrophy and remodeling.Through surgical intervention,the mice were divided into four groups:wild sham operation group(WT-sham),wild aortic stenosis group(WT-TAC),CAM?85 sham operation group(CAM?85-sham)and CAM?85 aortic stenosis group(CAM?85-TAC).The electrocardiogram of the four groups mice was recorded every two weeks,and the electrophysiological changes of the heart were observed and analyzed.The pathological changes of heart tissue in each group were observed by routine section staining;the expression and distribution of inflammation-related proteins and calcium-related proteins in the hearts of each group mice were detected by immunohistochemistry.The transcriptional expression of hypertrophy,fibrosis and apoptosis-related genes in the hearts of each group mice was detected by real-time quantitative PCR.The experimental results are as follows:(1)Physiological parameter analysis:compared with WT-sham group,abnormal waveforms such as elevation of J wave,T wave and ST segment,prolongation of QT interval were found in WT-TAC group.The QT interval of mice in CAM?85-sham group also increased at 10 and 12 weeks after operation.In addition to the above abnormalities,the ECG waveforms of mice in CAM?85-TAC group also showed serious abnormalities such as extrasystole,arrhythmia and atrioventricular block.(2)Histopathological analysis:compared with the control group,the ratio of heart weight to body weight and the ratio of heart weight to tibia length in WT-TAC group and CAM?85-TAC group increased significantly at 4,8 and 12 weeks after operation,and the ratio of heart weight to tibia length in CAM?85-TAC group was significantly higher than that in WT-TAC group at 12 weeks after operation.At 4,8 and 12 weeks after operation,the cross section of cardiomyocytes in CAM?85-TAC group was significantly higher than that in CAM?85-sham group and WT-TAC group,and the cross section of cardiomyocytes in WT-TAC group was significantly larger than that in WT-sham group.The severity of fibrosis and the expression of type ? collagen in WT-TAC group and CAM?85-TAC group were significantly higher than those in control group at 4,8 and 12 weeks after operation,and the fibrosis and type ? collagen content in CAM?85-TAC group were significantly higher than those in WT-TAC group at 8 and 12 weeks after operation.Compared with the control group,the number of cardiomyocyte apoptosis in WT-TAC group and CAM?85-TAC group increased significantly,and the degree of apoptosis in CAM?85-TAC group was significantly higher than that in WT-TAC group.(3)Immunohistochemical staining analysis:12 weeks after operation,the expression of inflammation-related proteins CD45 and CD68 in WT-TAC group was significantly higher than that in WT-sham group,the expression of CD45 and CD68 in CAM?85-TAC group was significantly higher than that in CAM?85-sham group and WT-TAC group.Similarly,the expression of CAMR1 and CAMR2 in the heart of WT-TAC group was significantly higher than that of control group at 4,8 and 12 weeks after operation,and the expression of calcium-associated protein in heart tissue of CAM?85-TAC group was significantly higher than that of CAM?85-sham group and WT-TAC group.(4)Real-time quantitative PCR analysis:after 12 weeks of intervention,the expression of cell hypertrophy related genes Nppa and ?-MHC in WT-TAC group was significantly higher than that in WT-sham group,and the expression of Nppb in WT-TAC group was also increased.The expression of Nppa,Nppb and ?-MHC in CAM?85-TAC group increased significantly compared with CAM?85-sham group,and also significantly up-regulated compared with WT-TAC group.The expression of tissue fibrosis related genes col1a1 and col3a1 in the left ventricle of WT-TAC group and CAM?85-TAC group was significantly higher than that of each control group,and the expression of col3a1 in CAM?85-TAC group was significantly higher than that of WT-TAC group,and the expression of Tgfb in CAM 85-TAC group was also significantly higher than that of CAM?85-sham group.The expression of apoptosis-related genes Casp3 and Bcl2 in the left ventricle of WT-TAC group and CAM?85-TAC group was significantly increased compared with the control group,and the expression of Casp3 in CAM?85-TAC group was higher than that in WT-TAC group,and the expression of Bax in TAC group was also significantly higher than that in sham group.Conclusion:The heart will undergo pathological hypertrophy and remodeling changes under the stimulation of continuous overload pressure.In this process,the structural remodeling and dysfunction of the electrophysiological signal transduction system in the heart will occur,resulting to different kinds of arrhythmias.Meanwhile,myocardial tissue was remodeled,including the increase of cardiomyocyte volume and the number of apoptosis,tissue fibrosis and inflammatory reaction:and other pathological changes.CAMR 85 gene is involved in the regulation of calcium signaling pathway in the heart,and the deletion of this gene will aggravate the related pathological changes in the process of cardiac hypertrophy and remodeling induced by TAC.Therefore,exploring the effect and mechanism of CAMR?85 gene on the process of pathological cardiac hypertrophy and remodeling can provide a new potential gene therapy target for the treatment of cardiac hypertrophy-related heart disease.