神经细胞凋亡在脊髓缺血再灌注损伤延迟性瘫痪中的作用

目的研究细胞凋亡在脊髓缺血再灌注损伤发生延迟性瘫痪中的作用。方法将48只新西兰白兔随机分为2组:对照组(sham)和缺血再灌注组(IR)。参照并改进Zivin方法建立兔脊髓腰骶段缺血再灌注延迟性瘫痪模型,比较各组动物不同时间点后肢运动功能及病理形态学变化;采用原位末端脱氧核糖核酸酶转移介导的脱氧尿三磷酸(dUTP)标记法(TUNEL法)检测神经细胞凋亡水平。结果HE染色显示,再灌注8 h组神经细胞形态基本正常,结构清楚,灰质中有少量空泡,但神经元细胞结构完好;再灌注24 h组:灰质中前角神经元细胞破坏严重,空泡形成,无明显炎症细胞浸润;再灌注72 h组:灰质前角中大量空泡形成,尚残存数个结构清楚的运动神经元,有明显炎症细胞浸润;再灌注168 h组:灰质中运动神经元消失,残存数个固缩坏死神经元。TUNEL法染色显示,sham组及再灌注8 h后,仅见非特异性染色。再灌注24 h后出现大量阳性细胞,至再灌注72 h阳性细胞数量达到最高峰,主要分布在前角运动神经元。再灌注1周后,灰质结构破坏严重,仅有少量神经元幸存,但其阳性细胞平均积分吸光度值仍较对照组高。结论脊髓缺血再灌注后发生延迟性瘫痪时,神经元死亡的方式主要是细胞凋亡。

Apoptosis of motor neurons in the spinal cord after ischemia reperfusion injury delayed paraplegia in rabbits

Objective To investigate neural cell apoptosis after spinal cord ischemia-reperfusion injury delayed paraplegia in rabbits.Methods The infrarenal aorta of white New Zealand rabbits(n=48) was occluded for 26 minutes using two bulldog clamps.The rabbits were killed after 8,24,72,or 168 hours(n=6 for each group).The clamps was placed but never clamped in sham-operated rabbits(n=24).The lumbar segment of the spinal cord(L5 to L7) was used for morphological studies,including hematoxylin and eosin staining and a modified terminal deoxynucleotidyltransferase mediated dUTP biotin nick end-labeling(TUNEL) staining method.Results Delayed paraplegia occurred in all the rabbits of ischemia reperfusion group at 16-24 h,but not in sham groups.Motor neurons were selectively lost at 7 days after transient ischemia.After ischemia,the affected areas contained neurons with positive TUNEL staining.Positive neurons were mainly located in gray,although most were concentrated in the intermediate and ventral areas.Adjacent sections were stained with hematoxylin and eosin exhibited ischemic cell changes(red and ghost neurons),while apoptotic bodies were also apparent.In addition,TUNEL study demonstrated that no cells were positively labeled until 24 hours after ischemia,but nuclei of some motor neurons were positively labeled at peak after ischemia reperfusion at 72 hours.Conclusion Spinal cord ischemia in rabbits induces morphological and biochemical changes suggestive of apoptosis.These data raise the possibility that apoptosis contributes to neuronal cell death after spinal cord ischemia.