目的探讨小鼠脊髓发育过程中血管-干细胞龛对神经干细胞分化、增殖和迁移的影响;探讨龛中的各种细胞、血管在发育中的变化及相互作用。方法发育过程中的胚胎鼠或生后小鼠150只,取脊髓腰膨大处的横断面切片。采用5-溴脱氧尿嘧啶核苷(BrdU)免疫荧光标记神经干细胞;用尼氏(Nissl)染色观察神经元的发育和形态变化;利用血管墨汁灌注结合免疫荧光三重标记的方法检测神经干细胞、神经元和神经胶质细胞在小鼠胚胎期及生后的形态分布变化;同时对脊髓内血管发育的动态变化进行形态学观察和体视学处理。结果妊娠14d(E14)小鼠脊髓内即有BrdU标记的阳性细胞,均匀分布。新生的神经元自神经管侧脑室下带迁移至中间层附近,逐渐分化为神经元,并集中于灰质呈现典型的“H”型。统计学分析表明,BrdU阳性细胞计数在发育中呈现抛物线,高峰值位于出生3d(P3)左右。此外,神经胶质细胞的祖细胞最早集中于边缘白质,随后又向中央的灰质回迁。血管发育经历了早期均匀分布,成年后集中在灰质分布的过程。血管、神经干细胞、神经元和神经胶质细胞构成了所谓的血管-干细胞龛。血管-干细胞龛主要位于侧脑室下带和灰质附近,其中的血管、神经干细胞、神经元和神经胶质细胞互相交织、紧密-一神经干细胞龛为脊髓发育及神经元和神经胶质细胞分化提供了适宜的微环境。
Objective To study how the vascular and stem-cellular niche affect the neural proliferation, differentiation and migration in the mouse spinal cord and to investigate the interaction among neurons, neuroglia and vasculature in the developing spinal cord. Methods A total of 150 mice from El7 to P180 were used in this project. BrdU assay, Nissl' s staining and immunofluorescent labeling (NeuN and GFAP) methods were applied. Blood vessels and neural stem cells were measured with stereological methods. Results BrdU positive neural stem cells appeared evenly in the embryonic spinal cord at as early as El4, and the newborn neurons migrated from the subventicular zone of the neural tube to the intermediate layer around it. With age increasing, the neural stem cells differentiated into neurons gradually, and the neurons mainly concentrated in the putative gray matter as a " H" shape. According to the statistical analysis, the BrdU positive stem cells developed as parabolic curve with the peak at P3. The neuroglial cells migrated from the "periphery" area of spinal cord ( marginal layer, the putative white matter) into the "center" ( gray matter). Blood vessels were uniform distribution at the early age, and later concentrated in the gray matter gradually. The vasculature, stem ceils, neurons and neuroglia formed a so called vascular and stem-cellular niche. The vascular stem-cellular niches were mainly located in the subventricular zone and gray matter. Vasculature, stem cells, neuron and neuroglia were woven together tightly. Conclusion The vascular and stem-cellular niche formed closely with the development of the spinal cord, which provides a suitable microenvironment for the development of the spinal cord and the differentiation of neurons and neuroglia.