嗅球摘除后嗅觉神经元凋亡的实验研究

Apoptosis of olfactory receptor neurons induced by bulbetomy

目的研究凋亡是否参与嗅上皮正常生理更替和嗅球摘除后嗅觉神经元死亡而后再生的过程,探讨凋亡与神经元再生的关系。方法应用原位末端标记法和透射电镜观察正常成年大鼠以及摘除嗅球后大鼠嗅上皮16、32、48 h和3、7、30 d时凋亡的出现和改变情况。结果正常成年大鼠嗅上皮中有末端脱氧核苷酸转移酶介导的脱氧三磷酸尿苷缺口末端标记(TUNEL)的阳性细胞(1.93±0.31)个/200μm。摘除嗅球后TUNEL阳性细胞数增加,32 h达峰值(90.9±18.03)个/200μm,以后迅速下降,维持于低水平。透射电镜下见嗅球摘除术后嗅觉神经元出现胞质浓缩、胞核染色质边聚等细胞凋亡的特征性超微结构改变。尚可见少量胞质内出现自噬泡以及除线粒体以外的细胞器扩张,但胞核正常的嗅觉神经元。结论凋亡参与成年大鼠嗅觉神经元生理性更替以及实验性嗅觉神经元死亡和再生的过程。此外,尚存在自噬型和胞质型神经元死亡。

Objective To study whether apoptosis plays a role in controlling the number of olfactory receptor neurons, so as to reveal the speciality and mystery of neurogenesis. Methods Using terminal deoxynucleotidyl transferase-mediated dUTP-fluoreacein nick end labeling （TUNEL） and transmission electron microscopy to detect apoptosis in olfactory mucosa of normal adult rats and damaged olfactory mucosa of 16, 32, 48 hours and 3, 7, 30 days after bulbectomy. Results In normal olfactory epithelium, a subpopulation of immature neurons, as well as mature neurons, showed internucleosomal DNA- fragmentation. The number of TUNEL-labeled neurons increased dramatically 32 hours after removal of olfactory bulb. Then it declined quickly and remained at low level. Ultrastructural data of olfactory mucosa showed that the feature of apoptotic neurons was chromafin condensation and cell shrinkage. Besides, some dying cells were characterized by the formation of numerous autophagic vacuoles, and few had some of the features of necrosis but without obvious mitochondrial swelling. Conclusions Apoptosis might play a role in turnover of the olfactory epithelium and regeneration in adult rats. There might be other two types of neural death through different mechanism.