| Objective:By establishing a rat model of myocardial infarction,investigate whether angiopoietin2(Ang2)promote angiogenesis after acute myocardial infarction through PI3K/Akt signaling pathway.Methods:Male Sprague–Dawley rats weighing 250 to 300 g were used in this study.Rats were randomly divided into 2 groups: sham-operated group(sham group)and myocardial infarction group(MI group),both of them were anesthetized with chloral hydrate(300mg/kg)administered intraperitoneally.Animals of the MI group were ligated the left anterior descending coronary artery(LAD)at the level of the left atrial appendage using a 6–0 polypropylene suture.Myocardial ischaemia was confirmed visually in situ by regional cyanosis,ST elevation and depression,or T wave inversion on the electrocardiogram,and hypokinetic or dyskinetic movement of the myocardium.Animals of the sham group were opened chest sutures without ligation of coronary artery.At 7 and14 days post-MI,the rats were re-anesthetized and the hearts were rapidly excised and rinsed in room-temperature saline.The infarct zone could be readily distinguished from the normal myocardium surrounding it by its distinctive pale coloration after 2,3,5‐triphenyltetrazolium chloride(TTC)staining method.Alternatively,left ventricles were immediately frozen with liquid nitrogen for molecular analysis.The RNA expression of Ang2,Tie2,PI3 K,Akt and CD105 were measured by RT-PCR.The protein expression of Ang2,AKT and phosphorylated AKT were measured by Western blot.Then the correlation between Ang2 and phosphorylated AKT was calculated.Results:TTC staining showed that non-infarcted myocardium tissues were pink,whereas infarcted myocardial tissues was pale.The expression of Ang2、Tie2、PI3K、Akt and CD105 RNA showed a significant increase from 7days to 14 days in the MI group,which did not show significant changes in the sham group.At 14 days,Ang2、Tie2、PI3K、Akt and CD105 RNA expression within the MI group were markedly increased compared to sham group.At 7and 14 days,Ang2 and phosphorylated AKT protein expression within the MI group were markedly increased compared to the sham group,while the total AKT protein expression have no difference.The protein expression of Ang2 and phosphorylated AKT showed a significant increase from 7days to 14 days in the MI group,which did not show significant changes in the sham group.The protein expression of phosphorylated AKT was positively correlated with Ang2.Conclusion:Myocardial ischemia induced by LAD ligation resulted in a sustained increase in Ang-2、Tie2、PI3K、Akt and CD105 RNA expression from 7days to 14 days.The results suggest that Ang2 plays an important role in angiogenesis by binding to Tie2 receptor after MI.What`s more,there was a positive correlation between phosphorylated AKT and Ang2 protein expression in MI group,indicate that the PI3K/AKT pathway was activated and correlated with Ang2.In conclusion,these results indicate that Ang2 exerts its angiogenesis effect through Tie2 receptor binding,and may be through a PI3K/AKT pathway activation in the rat model of myocardial infarction. |
