| Objective: To study the protective effect and myocardial cell apoptosis of granulocyte colony-stimulating factor (G-CSF) and ischemia postconditioning (Post) on rabbit's acute myocardial ischemia/reperfusion.Methods: A model of ischemia/reperfusion was established by left Ventricular artery (LVA) occlusion for 30 minutes. New Zealand rabbits are randomly allocated to five groups: (1) shame operation group (shame group): there was a thread through muscles of heart around LVA which was not ligates; (2) ischemia/reperfusion group (I/R group): LVA occlusion and reperfusion only with no other intervention. Then subcutaneous injection of 0.5ml normal saline for 5 days; (3) granulocyte colony-stimulating factor group (G-CSF group): subcutaneous injection of G-CSF (10μg/kg/d) for 5 days after ischemia/reperfusion. (4) ischemia postconditioning group (Post group): three episodes of 30 seconds reperfusion and 30 seconds occlusion after 30 minutes ischemic. Then subcutaneous injection of 0.5ml normal saline for 5 days; (5) granulocyte colony-stimulating factor group + ischemia postconditioning group (G-CSF group + Post group): three episodes of 30 seconds reperfusion and 30 seconds occlusion after 30 minutes ischemic. Then subcutaneous injection of G-CSF (10μg/kg/d) for 5 days. We open the rabbit chest cavity to use the method of six sutures and six knots. Dynamic electrocardiogram were performed during the experiment for we observe the heart rate, ST-segment and cardiac arrythmia. electrocardiogram aboutⅡLeads were recorded before operation, after ischemia 15 minutes and reperfusion 15 minutes later. Blood was drawn from femoral vein to evaluate cardiac troponin (cTnI) values with ELISA before operation and 1 week after reperfusion in every group. In shame group blood was drawn through the same way. After four weeks cardiac muscle tissues of eight rabbits in each group were determined myocardial infarct size by staining with triphenyltetrazolium chloride (TTC) dye and were done using optical microscope. Morphologic examination of cardiac muscle tissues of another two rabbits in each group was done using transmission electron microscope. myocardial cell apoptosis of five rabbits in each group was determined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL).Results: 1. During coronary occlusion there were trends for an increase in heart rate, but this change were not significant compared with the baseline value (P>0.05). 2. There were ST-segment elevations after LVA occlusion and ST-segment resolutions 15 min after reperfusion in ischemia-reperfusion groups. Compare I/R group, at the end of 15 min reperfusion the average values of ST-segment elevation in lead II displayed on the ECG was smaller, and the rate of arrhythmia occurrence were decreased in Post group and G-CSF group + Post group than that in the I/R group and G-CSF group (P<0.05). 3. There were no significant differences in cTnI values among four groups before LVA occlusion (P>0.05). After reperfusion cTnI values of I/R group, G-CSF group, Post group and G-CSF group + Post group were 3.34±2.21, 1.62±1.65, 1.69±1.70, 1.54±1.02 ng/ml respectively. The cTnI values of G-CSF group, Post group and G-CSF group + Post group were significantly lower than that of I/R group (P<0.05). 4. Mycardial infarct sizes of I/R group, G-CSF group, Post group and G-CSF group + Post group were 31.37±12.18%, 19.56±7.39%, 18.27±4.76% and 16.42±6.03% respectively. Compare to I/R group infarct sizes of G-CSF group, Post group and G-CSF group + Post group were significantly reduced (P<0.05). 5. Morphologic examination indicated that there were milder injuries of the cardiomyocyte of rabbits in G-CSF group, Post group and G-CSF group + Post group compared with I/R group. 6. TUNEL detection showed that the apoptotic index of I/R group, G-CSF group, Post group and G-CSF group + Post group were (32±4)%, (16±2)%, (17±2)% and (15±1)% respectively. G-CSF group, Post group and G-CSF group + Post group were lower than that in the I/R group (P<0.05). Conclusion: The method of six sutures and six knots can successfully reduce intercostal arterial hemorrhage and Pneumothorax formation. Ischemic postconditioning at onset of reperfusion can obviously reduce myocardial reperfusion injury and inhibiting cardiomyocyte apoptosis. G-CSF protected the heart by inhibiting cardiomyocyte apoptosis, inducing neovascularisation after acute myocardial ischemia/reperfusion. There were no obvious difference heart protective effects between Post and G-CSF in our study. The protective effects of Post in combination with G-CSF through reducing reperfusion injury, inhibiting cardiomyocyte apoptosis and inducing neovascularisation, which are better than Post or G-CSF alone (p>0.05, mostly). Post in combination with G-CSF is a safe and feasible strategy in the treatment of acute myocardial ischemia/reperfusion. |
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