BACKGROUND:Exercise training is an important non-drug rehabilitation method for many heart diseases,and it can also enhance the heart's tolerance to adverse stressors(such as myocardial ischemia),that is,exercise preconditioning.Granulocyte colony-stimulating factor can effectively mobilize stem cell homing and differentiation and promote the repair of damaged myocardium.However,the effect of the combination of the two treatments is not yet clear. OBJECTIVE:To explore the effect of granulocyte colony-stimulating factor supplementation combined with high-intensity intermittent exercise preconditioning on cardiac remodeling in rats with acute myocardial infarction and investigate its possible mechanism. METHODS:Totally 58 male Wistar rats were divided into sham group(n=10),model group(n=12),model drug group(n=12),model exercise group(n=12)and model combined treatment group(n=12).The myocardial infarction rat model was made by coronary artery ligation.The model exercise group and the model combined treatment group were pretreated with 8 weeks of high-intensity intermittent exercise on an electric treadmill before modeling.The model drug group and the model combined treatment group were subcutaneously injected with human recombinant granulocyte colony-stimulating factor 3 hours after modeling for 5 days(10 μg/kg per day).At 8 weeks after administration,echocardiography was used to detect heart structure and function;heart was stained with 2,3,5-triphenyltetrazolium chloride and Masson staining to obtain myocardial infarct area and collagen volume fraction,respectively.Vessel density and cell apoptosis rate were detected by immunofluorescence.Real-time fluorescent quantitative PCR was utilized to detect the mRNA expression of embryonic genes(brain natriuretic peptide,β-myosin heavy chain)and myocardial contraction regulatory factors(α-myosin heavy chain,sarcoplasmic reticulum Ca2+-ATPase).Western blot assay was used to detect the protein expression of cardiac stromal cell-derived factor 1,CXC chemokine receptor protein 4,Janus kinase 2(JAK2),signal transducer and activator of transcription 3(STAT3),Bcl2,Bax,and cleaved caspase-3. RESULTS AND CONCLUSION:(1)Compared with sham group,myocardial infarct size,collagen volume fraction,and apoptosis rate increased(P<0.05);vessel density,left ventricular fractional shortening,and left ventricular ejection fraction decreased(P<0.05);brain natriuretic peptide and β-myosin heavy chain mRNA increased(P<0.05),α-myosin heavy chain and sarcoplasmic reticulum Ca2+-ATPase mRNA and α-myosin heavy chain/β-myosin heavy chain ratio decreased(P<0.05);stromal cell-derived factor 1,CXC chemokine receptor protein 4,Bax,cleaved caspase-3 protein expression increased(P<0.05);p-JAK2,p-STAT3,and Bcl-2 protein expression decreased(P<0.05)in the model group.(2)Compared with the model group,the above indexes in the model drug and model exercise groups were significantly improved(P<0.05).Compared with the model drug and model exercise groups,the above parameters were further ameliorated(P<0.05)in the model combined treatment group.(3)The results showed that supplementation of granulocyte colony-stimulating factor or high-intensity intermittent exercise preconditioning alone can improve cardiac remodeling in rats with acute myocardial infarction,and the combined therapy has a better effect,which may be related to the induction of stem cell homing and the activation of JAK2/STAT3 signaling pathway to inhibit cardiomyocyte apoptosis.