| Objective: To explore the effects of exercise rehabilitation on cardiomyocyte apoptosis,myocardial fibrosis,autophagosomes and cardiac function in rat model of myocardial infraction(MI).Methods: Twenty-four male SD rats were randomly divided into myocardial infarction exercise group(MI-E group),myocardial infarction sedentary(MI-Sed group),sham-operated exercise group(Sham-E group),and sham-operated sedentary(Sham-Sed group),five to seven rats in each group.The MI model was constructed by ligating the left anterior descending coronary artery(LAD),while the Sham groups were needled without ligation.Exercise training had been begun one week after surgery.Exercise program included one week of adaptive motion: 10 m/min x 20 min,20min/day,5 days /week,and four weeks of formal exercise: warm-up of 10 m/min x10 min,and then three groups exercise of 20 m/min x 7 min and 15 m/min x 3 min,40min/day,5 days/week.However,the MI-Sed and Sham-Sed groups did not receive exercise training during the experimental process.After five weeks of exercise training,the left ventricular cardiac structure and function were detected by echocardiography,cardiomyocyte damage and inflammatory response were observed by hematoxylin and eosin(HE)staining,the degree of myocardial fibrosis was detected by Masson staining,cell apoptosis was detected by Tunel staining,and the autophagosomes and ultrastructure of cardiomyocyte were examined by transmission electron microscopy.Results:(1)MI caused the left ventricular wall thinning and cavity enlargement,and reduced systolic function.Compared with the MI-Sed group,exercise training reduced LVESD(4.53±0.67 vs.5.52±0.51,p<0.05),and increased LVEF%(58.99 ±7.60 vs.45.55 ± 3.41,p <0.05)and FS%(30.82 ± 6.60 vs.20.00 ± 2.52,p <0.05).(2)Compared with the Sham groups,the myocardium of MI groups showed different degrees of injury,massive inflammatory cell infiltration and firbroblast hyperplasia,while the MI-Sed group had the most disordered myocardial arrangement and severe cellular damage.(3)Compared with the Sham groups,the number of cardiomyocytes apoptosis increased in MI groups(p <0.05);And compared with the MI-Sed group,the number of cardiomyocytes apoptosis was reduced in MI-E group(14.00 ± 1.98 vs.29.85 ± 4.47,p<0.05).(4)The cardiomyocytes of the Sham groups were closely and orderly organized and locally showed focal myocardial fibrosis,while there were seriously disordered arrangement of cardiomyocytes and significantly increased the degree of myocardial fibrosis in the MI groups.The cardiomyocytes of the MI-E group were neatly aligned compared with MI-Sed group,and CVF% was decreased(7.64 ± 2.11 vs.13.66 ± 2.07,p <0.05)and myocardial fibrosis was improved.(5)In the Sham groups,the cardiomyocyte had normal morphology,with complete and continuous cell nuclear membrane,complete mitochondrial structure,the cristae and muscle fiber bundles were arranged in order,and the autophagosome was not found.While in the MI groups,the myocardium suffered severe injury,cell structure and sorting disordered;severe mitochondrial structure damage with interruption of ridge arrangement;myofibrils looseness disorder and interstitial edema,and formation of autophagomes under the visual field.But compared with the MI-Sed group,the MI-E group had less cardiomyocyte damage,complete mitochondrial structure,mild edema and more autophagomes.Conclusions:(1)Exercise rehabilitation can alleviate cardiomyocyte damage and apoptosis;(2)Exercise rehabilitation can reduce the myocardium infraction area,inhibit myocardial fibrosis and then improving cardiac function;(3)Exercise rehabilitation may play a cardiac protective effect through moderately inducing cardiac autophagy. |
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