The Expression And Detection Of MicroRNA In Rat Brain After Diffuse Axonal Injury

Objective:To investigate the expression of microRNA (miRNA) in injured sites of rat brains after diffuse axonal injury (DAI).Methods:6Sprague-Dawley rats of9were objected to DAI according to Marmarou’s methods. Every3rats were sacrificed on the1st and7th day after injury and their brains were harvested and brain tissue of neocortex, hippocampus and brain stem were isolated.3rats in control group experienced sham operation without injury and their brain tissue were also obtained. Total RNA were extracted and miRNA microarray were used to detect the expression of miRNA in every brain tissue. Then we used TargetScan (Release6.2), Pictar and miR Base to determine the expression of related target gene after DAI.Results:In the brain tissue of neocortex, there were19miRNAs up-regulated significantly (set1.5folds as threshold, so as the following)1d after DAI, and79miRNAs down-regulated significantly (set1.5folds as threshold, so as the following); there were146miRNAs up-regulated significantly7d after DAI and115miRNAs down-regulated significantly. In the tissue of hippocampus, there were195miRNAs up-regulated significantly1d after DAI, and87miRNAs down-regulated significantly; the expression of48miRNAs were up-regulated significantly7d after DAI and70miRNAs down-regulated significantly. In the tissue of brain stems, there were142miRNAs up-regulated significantly1d after DAI, and115miRNAs down-regulated significantly; the expression of101miRNAs were up-regulated significantly7d after DAI and145miRNAs down-regulated significantly. Further comparative analysis indicated that there were6miRNAs up-regulated significantly in the tissue of neocortex both1d and7d after DAI and34miRNAs down-regulated significantly. The expression of15miRNAs were up-regulated significantly in the tissue of hippocampus both1d and7d after DAI and25miRNAs down-regulated significantly. The expression of30miRNAs were up-regulated significantly in the tissue of brain stems both1d and7d after DAI and41miRNAs down-regulated significantly. Target genes reverse exploring indicated that the expression of miRNA-190b, which is related to CAPN2, miRNA-let-7a, miRNA-let-7b, miRNA-let-7c, miRNA-let-7d, miRNA-let-7i and miRNA-let-7f, related to CASP3, and miRNA-23a, related to CASP7, varied significantly. Especially notable is that miRNA-let-7a、miRNA-let-7c and miRNA-23a turned out to be significant varied expression in all the injured sites of neocortex, hippocampus and brain stem1d after DAI in rats.Conclusion:The comprehensive changes of miRNA expression were detected after DAI in rat brain tissue of neocortex, hippocampus and brain stem. MiRNA-let-7a、 miRNA-let-7c and miRNA-23a potentially play important roles in the secondary axonal disconnection through their target genes after DAI.