大鼠脑创伤后损伤区miRNA-21的差异表达及干预研究

An intervention study of differential expressions of miRNA-21 in rats with traumatic brain injury

目的探讨大鼠脑创伤后损伤区miRNA．21表达的动态变化，以及外源性miRNA．21对大鼠脑创伤后细胞凋亡及神经功能的影响。方法84只大鼠采用随机数字表法分为假手术对照组、创伤组、空白干预组及miRNA-21干预组，每组21只。假手术对照组行头皮切开和磨除骨窗，不进行打击：另外3组按液压打击法制造创伤模型．空白干预组与miRNA-21干预组再分别注射空白阳离子脂质体及含有miRNA-21的阳离子脂质体。创伤后或干预后2h、12h、24h、48h、72h、7d及14d进行神经功能学评分，而后取脑组织行实时定量PCR检测创伤区miRNA-21表达量，采用石蜡包埋切片原位末端标记（TUNEL）法检测凋亡细胞。结果miRNA-21干预组大鼠脑创伤后2hmiRNA-21表达开始升高，48h达高峰后逐渐下降，伤后7d时仍高于假手术对照组，差异均有统计学意义（P〈0．05）。伤后24h、48h、72h时高于创伤组与空白干预组，差异均有统计学意义（P〈0．05）。评分结果显示，miRNA-21干预组自干预后24h开始。评分明显低于创伤组及空白干预组，差异有统计学意（P〈0．05）。TUNEL染色结果显示，miRNA．21干预组各时间点凋亡细胞数均较创伤组明显降低，差异有统计学意义（P〈0．05）。结论miRNA-21可能参与颅脑创伤后的修复过程，抑制创伤区的细胞凋亡。

Objective To evaluate the dynamic changes of miRNA-21 expression in injured brain tissues of rats with traumatic brain injury （TBI）, and explore the effect of ectogenic miRNA-21 on neuronal apoptosis of the rats and their neurological functions. Methods Eighty-four rats were randomly divided into sham-operated group, TBI model group, blank-intervention group and miRNA-21-intervention group （n=21）. Rats in the sham-operated group were only performed scalp incision and window bone removal without beating, and those in the other three groups were performed beating to induce TBI models; liposomes with/without miRNA-21 were injected into the latter two groups. Several time points after the brain injury/intervention： 12, 24, 48 and 72 h, and 1 and 2 weeks, respectively, were chosen to measure the neurological functions using Modified Neurological Severity Scale （mNSS） and footfault test. Then, the animals were sacrificed to observe the miRNA-21 expression levels by using quantitative real-time-PCR and to examine the neuronal apoptosis in rat cerebral cortices by TUNEL. Results The miRNA-21 expression began to obviously increase in injured brain tissues at 2 h after TBI, peaked at 48 h after TBI in the cerebral cortices; the miRNA-21 expression level was still higher than that in the sham-operated group 7 d after TBI （P〈0.05）; the miRNA-21 expression level was higher than that in the TBI model group and blank-intervention group at 24, 48 and 72 h after TBI （P〈 0.05）. Began with 24 h of TBI, mNSS showed that the scores of miRNA-21-intervenion group weresignificantly lower than those in the TBI model group and blank-intervention （P〈0.05）. TUNEL indicated that the count of apoptotic cells in the traumatic area of miRNA-21-intervenion group was significantly smaller than that in the TBI model group （P〈0.05） Conclusion MiRNA-21 may be involved in the process of recovery after traumatic brain injury to inhibit the apoptosis in the traumatic area.