小鼠脊髓发育与神经细胞凋亡

目的通过观察小鼠脊髓发育过程中神经元的增殖、分化与凋亡,探讨小鼠脊髓的发育过程及其调控机制。方法取妊娠第18天(E18)至生后第90天(P90)小鼠173只,用5’-溴脱氧尿嘧啶核苷(BrdU)技术标记增殖的神经干细胞,免疫荧光法(DCX,NeuN和Caspase8)标记脊髓中的新生神经元,成熟神经元和凋亡细胞。结果在胚胎与出生早期,BrdU阳性细胞均匀分布于小鼠脊髓各部位。随着小鼠日龄的增加,脊髓神经干细胞可以分化为神经胶质细胞与神经元。其后,位于神经管侧脑室的新生神经元向中间层(未来的灰质)迁移,逐渐分化为成熟神经元。最后,神经元向脊髓中央聚集,灰质呈现典型的"H"型。随着神经元的分化,一些凋亡神经细胞出现在新生神经元与成熟神经元中。荧光双标显示,大部分的凋亡神经细胞都是新生神经元,说明神经元凋亡常常发生在新生神经元中。统计学分析表明,DCX、NeuN、Caspase-8标记的阳性细胞数均随小鼠日龄的增加而减少,说明神经元的分化和凋亡在脊髓的发育过程中逐渐减少。结论在脊髓的发育过程中存在着神经元的增殖、分化与凋亡。三者相互协同,共同调节脊髓的形成与发育。

Development of the mouse spinal cord and neuroapoptosis

Objective To investigate the neural proliferation, differentiation and apoptosis of the developing spinal cord of the mouse and to discuss the mechanism of spinal cord’s development. Methods 5-Bromodeoxyuridine (BrdU) assay was used to mark the proliferative neural stem cells, and the immunofluorescent stainings (DCX, NeuN and Caspase8) were carried out to visualize the newborn neurons, mature cells and apoptotic cells in the spinal cord with 173 mice arrange from E18 to P90.
Results BrdU positive neural stem cells appeared evenly in the spinal cord at early days. With age increasing, the neural stem cells differentiated into neuroglial cells and neurons. The newborn neurons in the subventricular zone migrated toward the intermediate zone (putative gray matter) and differentiated into mature neurons gradually. With neurons’ concentrating towards the center, the gray matter formed an “H” shape. In the meantime, with neural differentiation, some apoptotic neurons appeared among the newborn neurons and mature neurons. Double immunostaining showed that most apoptotic neurons were newborn neurons, suggesting the neuroapoptosis more likely occurred in newborn neurons. The statistical data showed that the number of DCX, NeuN and Caspase-8 positive cells reduced with age increasing, suggesting neural differentiation and neuroapoptosis decreased during spinal cord’s development. Conclusion Neural proliferation, neural differentiation and neuroapoptosis occur in developing spinal cord. They work together to regulate the formation and development of the spinal cord.