| Objective:A rat model of myocardial infarction was established to study the quantitative expression of microRNA 21 and cytoskeletal proteins in different stages of myocardial infarction and different tissues.The distribution and dynamic changes of microRNA 21 and cytoskeletal proteins before and after myocardial infarction were analyzed.To explore the role of the two in myocardial injury and ventricular remodeling after myocardial infarction.Methods:Thirty-two SD male rats,weighing 200±20 g,were randomly divided into four groups,8 in each group,including 3 operation groups(1 week after surgery,4 weeks after surgery,8 weeks after surgery)and 1 sham operation group.In the operation groups,the left anterior descending coronary artery ligation was performed.The sham operation group was only threaded and not ligated,and the rest of the operation was the same as the operation group.Blood was collected from the tail vein of the rats before and after the modeling,1 week,4 weeks,and 8 weeks.The expression level of microRNA 21 in the circulating serum was quantified by q-PCR at different time points before and after modeling.After that,the operation group was sacrificed at 1 week,4 weeks,and 8 weeks after surgery.The heart was taken out,rinsed with physiological saline,and frozen sectioned.TTC staining was used to observe myocardial infarction and quantitatively detect infarct size.The expression level of microRNA 21 in the gray zone tissue at different time points after modeling was quantitatively detected by q-PCR.Immunohistochemistry was used to detect the expression of cytoskeletal proteins(desmin,actin,myoglobin)in different regions of the tissue(including infarct core,gray zone,normal zone)and quantitative analysis.Finally,paired t-test and one-way ANOVA were used to analyze the data between groups.Results:1.The expression of microRNA 21 in circulating serum was not significantly difference before modeling(F=0.055,P>0.05),and the difference was statistically significant after modeling(F=22.5 89,P<0.001).The expression of microRNA 21 after modeling was 0.99 times,1.89 times,3.85 times,and 1.42 times before modeling.The expression of microRNA 21 in each operation group(1 week,4 weeks,and 8 weeks after myocardial infarction)was 1.93 times,3.82 times,and 1.39 times higher than that of the sham operation group,respectively.2.The expression of microRNA 21 in the gray zone tissue was statistically significant after modeling(F=29.309,P<0.001).The expression of microRNA 21 in each operation group(1 week,4 weeks,and 8 weeks after myocardial infarction)was 4.46 times,8.26 times,and 2.03 times higher than that of the sham operation group,respectively.3.The infarct size of the sham operation group,1 week,4 weeks,and 8 weeks after surgery were 0 mm3,30.790±6.810 mm3,22.430±5.401 mm3,and 65.454±29.492mm3,respectively.The infarct size was the largest at 8 weeks after surgery,followed by the first week after surgery,and the infarct size was the smallest at 4 weeks after surgery.4.In the circulating serum and gray zone tissues,the infarct size and microRNA 21 expression in the sham operation group were lower than those in the operation group.In the three operation groups,the maximal infarct size corresponded to the lowest microRNA 21 expression at 8 weeks postoperatively;the minimum infarct size at 4 weeks postoperatively corresponded to the highest expression of microRNA 21.5.The cytoskeletal proteins(desmin,actin,myoglobin)in the infarct core zone and the gray zone of each operation group(1 week,4 weeks,and 8 weeks after myocardial infarction)were lower than the normal zone(There was no statistical difference in the expression of desmin in the myocardial infarct core zone and the normal zone 1 week after surgery.).And gradually decreased with time after myocardial infarction.6.In the infarct core zone and the gray zone,the ratio of desmin,actin,myoglobin and sham operation were less than 1 at 1 week,4 weeks,and 8 weeks after surgery.The expression of cytoskeletal protein was down-regulated in the infarct core zone and gray zone of rat model of myocardial infarction,and gradually decreased with time after myocardial infarction.Conclusion:1.The expression levels of microRNA 21 in circulating serum and gray zone tissues after myocardial infarction were consistent and changed with time.It is suggested that the expression level of microRNA 21 may be affected by myocardial injury after myocardial infarction and ventricular remodeling in the late stage.2.The expression level of microRNA 21 and infarct size changed with time after myocardial infarction.The maximum infarct size at 8 weeks postoperatively corresponds to the lowest expression for microRNA 21.The minimum infarct size at 4 weeks postoperatively corresponds to the highest expression of microRNA 21.It is suggested that high expression of microRNA 21 may protect against myocardial infarction.3.The expression levels of cytoskeletal proteins(deprotein,actin,myoglobin)in the infarct core zone and gray zone of rats with myocardial infarction decreased with time It is suggested that the destruction of cytoskeletal proteins is irreversible and may be related to ventricular remodeling after chronic myocardial infarction. |
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