The Expression Changes Of MMP-9mRNA TIMP-1mRNA And Caspase-3 MRNA In The Brain Of Neonatal Rats With Hypoxic-ischemic Brain Damage(HIBD)

ObjectiveThe purpose of this study is to explore the mechanism of brain edema and apoptosis of neonatal rats induced by hypoxia-ischemia and provide new ideas for clinical treatment of HIE.Method1.Establishment of HIBD model:Neonatal 7-day-old Wistar rats were randomly divided into sham-operation control group,HIBD 6h,12h,24h,48h and 72h groups (n=12 per group).The model of HIBD was induced by unilateral carotid ligation followed by timed exposure to 8%oxygen.Only separated the left common carotid artery ligation,sham-operation control group rats were executed at 24h after the operation.The behavior of the rats was observed during hypoxic.2.General examination of the brain:Observed the appearance of the brain.3.Expression of MMP-9 mRNA,TIMP-1 mRNA and caspase-3mRNA:The expression of MMP-9mRNA,TIMP-1mRNA and caspase-3mRNA in brain tissue of neonatal rats was measured by Real-time Q-PCR method.4.Apoptosis rate:Detected the apoptosis rate of the flesh brain tissue by flow cytometryResults1.Behavior of experimental animals:The behavior of all neonatal rats was normal at before operation.Sham-operated control group demonstrated no abnormal behavior;But after experiencing serious hypoxia the rats of HIBD groups showed obvious dystropy.2.General examination of the brain:The ligated brainhemisphere of HIBD groups showed obvious pallor and edema at 24h,and showed liquefactive necrosis lesion at 72h,or even brain tissue was completely liquefied with dural adhesions.The two brain hemispheres of sham group showed no pathological change.3.Expression of MMP-9 mRNA,TIMP-1 mRNA and caspase-3mRNA in the brain:①The expression of MMP-9mRNA was very low in the sham-operation control group,but in HIBD groups,it began to increase at 6h,and reached a peak at 24h,then gradually decreased,but still maintained the high level at 72h,compared to the control group,each group was statistically significant(P＜0.01);②The expression of TIMP-1mRNA was aslo very low in the sham-operation control group.But in HIBD groups,it increased slightly at 6h,12h and 24h,compared to the control group,each group was statistically significant(P＜0.05),with no significant difference among the three groups(P＞0.05),then decreased at 48h and 72h,but with no significant difference from control group(P＞0.05);③The ratio of MMP-9mRNA/TIMP-1 mRNA was normal in the sham-operation control group and HIBD 6h group,it began to increase at 12h,and reached a peak at 48h,then gradually decreased,but still maintained the high level at 72h,compared to the control group,each group was statistically significant(P＜0.01);④The expression level of caspase-3mRNA was aslo very low in the sham-operation control group,but in HIBD groups,it began to increase at 6h,and reached a peak at 24h,then gradually decreased,but still maintained the high level in HIBD 72h,compared to the control group,each group was statistically significant(P＜0.01).There was no significant difference between the HIBD 12h and 48h group,also HIBD12h and 72h group.The ratio of MMP-9mRNA/TIMP-1mRNA and the expression of caspase-3 mRNA was positively correlated(r=0.774,p＜0.01).4.Apoptosis rate of brain tissue:The apoptosis rate of brain tissue was very low in the sham-operation control group and HIBD 6h group,but it began to increase at 12h,and reached a peak at 48h,then gradually decreased,but still maintained the high level at 72h,compared to the control group,except for HIBD6h group,each group was statistically significant(P＜0.01).The ratio of MMP-9mRNA/TIMP-1mRNA and the apoptosis rate of brain tissue were positively correlated(r=0.782,p＜0.01);the apoptosis rate of brain tissue and the expression of caspase-3mRNA were positively correlated(r=0.703,p＜0.01).Conclusions 1.The HIBD model was successfully established.2.Hypoxia-ischemia increased the expression of MMP-9mRNA in brain tissue of neonatal rats,and the unbalanced expression between MMP-9mRNA and TIMP-1mRNA possibly was one cause of brain edema induced by HIBD.3.After hypoxia-ischemia of neonatal rats,the expression of caspase-3mRNA in brain tissue increased,meanwhile,the apoptosis rate of brain tissue was increased,and the ratio of MMP-9mRNA/TIMP-1mRNA had a positive correlation with the apoptosis rate of brain tissue and the expression of caspase-3mRNA. Therefore MMP-9 may participate in the process of apoptosis induced by HIBD.