The Role Of MiR-182 And Hypoxic Ischemic Brain Damage On The Long-term Outcome In Rats Of HIBD

Objective:This study was designed to examine long-term outcome such as motor,energy metabolism,learning and memory ability,circadian rhythm following HIBD in neonatal rats,and to observe the effects of miR-182 overexpression on the long-term prognosis of rats with hypoxia ischemia.Then we analyzed the relationship between HIBD and long-term behavior changes,at the same time,the role of miR-182 on hypoxic ischemic brain damage and the regulation of circadian rhythm is also our concern.Methods:In the first part,7-day-old(P7)SD rats were divided into HIBD group and sham operated group randomly,and HIBD model of neonatal rats were made by Rice-Vannucci method.Then these rats were carried up in normal condition until the age of 2-month-old.The alterations of energy metabolism,rhythm of energy metabolism and activity of rats in two groups were detected by energy metabolism test system concluding metabolic cages and computer analysis system.The metabolic cages were used to measure the energy metabolism,eating and drinking and activity of rats.And data is analyzed by analysis software.Morris water maze was used to study the learning and memory ability of rats,and it conclude of positioning navigation experiment and space exploration experiment.Wheel-running test was used for recording the locomotor activity of rats in the constant darkness,then the data was analyzed to describe the difference of the circadian rhythm of the two groups.In the second part,1-day-old(P1)SD rats were divided into LV-rno-miR-182 treatment group and empty virus control group randomly.The both groups had left ventricular injection with stereotaxic apparatus and micro injector after anesthesia.The treatment group was injected with recombinant lentivirus LV-rno-miR-182,and the other was empty virus.When the groups of rat grew up to 7-day-old age,HIBD model was made.And the transfection was evaluated by small animal imaging technology when rats were 10 days old.The rats were evaluated by open field test,Morris water maze test and wheel-running test when they were 2 months old.Results:1、In the respiratory exchange rate(RER),the result of HIBD group was significantly increased compared with sham operation group and there was statistical difference(p<0.05).The total activity of the two groups had significant difference(p<0.05),and thedata of HIBD group was less than the sham one.It suggests that HIBD can cause long-term motor impairment in rats.There was no difference between the two groups in the total rearing and total food intake,but there were significant differences in the data of the two groups during night and early morning hours.The moving distance andspeedof HIBD group was significantly more than sham operation group(p<0.05)in open field test.Rats in HIBD group were more inclined to activities in the central area compared with sham operation group(p<0.05)and showed obvious anxiety tendency.In Morris water maze test,the result of positioning navigation experiment shows that the descent velocity of average escape latency of sham operation group was faster than that of HIBD group,and the descent velocity tended to smooth in 4～6d while the sham operation one tended to stabilize.There was no significant difference between the sham operation group and the HIBD group in the number of crossing the platform(p>0.05).But compared with sham operated group,the thigmotaxis of HIBD rats was significantly increased.It shows that the learning and memory function of rats in HIBD group decreased obviously.2.The result of diurnal cycle had no significant difference between the two groups(p>0.05)in wheel-running test.But the onset time of HIBD group was delayed compared with the control group(p<0.05).It suggested that HIBD could cause the disorder of circadian rhythm in rats.3.In experiments of the second part,it was found that spontaneous activity of both groups was decreased and there was no significant difference between the two groups in the results of distance,the speed of movement and the peripheral area activity in the open field test(p>0.05).It was suggested that the over expression of miR-182 had no significant effect on the emotional function in rats of HIBD.It was found that the average escape latency of the rats in the LV-rno-miR-182 treatment group was significantly higher than that of the empty virus control group in positioning navigation experiment,and the difference was significant(p<0.05).The number of crossing the platform in the LV-rno-miR-182 treatment group was significantly lower than that of the empty virus control group(p<0.05)in space exploration experiment and the thigmotaxis of the LV-rno-miR-182 treatment group was significantly higher than that of the empty virus control group.It is suggested that overexpression of miR-182 can aggravate the impairment of learning and memory ability in HIBD rats.4、The result of diurnal cycle had no significant difference between the two groups(p>0.05)in wheel-running test,but the LV-rno-miR-182 treatment group had the earlier onset time(p<0.05).These results suggest that miR-182 overexpression can change the effect on the circadian rhythm of HIBD rats.Conclusion:Hypoxic ischemia in neonatal rats could lead to abnormality of movement,emotion,lipid metabolism,learning and memory ability,and the circadian rhythm disorder could also take place.The over expression of miR-182 could aggravate the impairment of learning and memory ability,and change circadian rhythm disorder caused by hypoxia ischemia.But there was no effect on movement and emotion outcome.