因意外而中止妊娠的6-8周人胚脑发育及相关因子表达的形态学研究

Morphological Research on Brain Development and Expression of Vital Cytokines in Brain of Human 6-8 Week Old Embryo Aborted for Unexpected Cause

目的研究人胚脑早期发育过程中细胞的增殖、分化、凋亡及相关因子的表达变化，为明确人胚脑发育过程中的细胞增殖、分化和凋亡机制提供依据。方法收集因意外而中止妊娠的6～8周人胚，采用TUNEL染色和免疫组化SABC染色。观察脑的发育、增殖和凋亡细胞的分布及相关因子的表达。结果人胚脑6周时，端脑、间脑、中脑、后脑与末脑已形成。6～8周，各脑均由生发层（GL）、中间层（IL）和边缘带（MZ）组成。6～7周时，TUNEL法标记的细胞及PCNA、Bcl-2、Bax、Fas、Fas—L、Rb和P53阳性细胞分布于各脑的GL和IL，其沉淀物出现在圆形或椭圆形细胞的胞核和胞浆中；8周时，Fas和Rb阳性细胞分布于各脑的IL，其沉淀物出现在梭形细胞的胞浆和突起中，TUNEL法标记的细胞及其它因子阳性细胞的分布同6～7周。各因子的表达与细胞增殖和凋亡的发生在时间和空间上基本一致。结论人胚脑发育过程中，神经祖细胞的增殖和凋亡同时发生，Fas、Fas-L和Bax可能介导凋亡的发生，Bcl-2则可能通过抑制细胞凋亡而维持细胞的存活，Rb与P53可能在神经祖细胞正常增殖和分化中起监控和维持作用。

Objective To clarify the changes in cell proliferation, differentiation, apoptosis and in the expression of vital cytokines during development of 6-8 week old embryo, and hence provide the evidence for identifying the mechanisms of cell proliferation, differentiation, apoptosis during early developing human embryonic brain. Methods Human aborted embryos were obtained with the consents signed by the pregnant women with unexpected abortions in gestation of 6-8 weeks. The histochemical SABC method and TUNEL Staining were employed to this research project. Results At 6 weeks, two telencephalons, diencephalon, mesencephalon, metencephalon, and myelencephalon have been formed, and from week 6 to 8, every cerebral vesicle has had three layer cells including germinal layer （GL）, intermediate layer （ IL ）, and marginal zone （MZ）. At 6-7 weeks, TUNEL-labeled cells and PCNA-, Bcl-2-, Bax-, Fas-, Fas-L-, Rb- and P53-positive cells were all observed in the GL and IL of the five brain regions, positive deposition appeared in nuclei. At week 8, Fas- and Rb-positive cells were observed in the IL of the five brain regions, positive deposition appeared in cytoplasm and cell processes, and no changes in the distributions of TUNEL-labeled cells and positive cells regarding the other five factors. The expressions of the cytokines were in agreement with the occurrence of the neuronal proliferation and apoptosis temporally and in space. Conclusion During development in early embryo brain, neural precursor cell proliferation and apoptosis occur simultaneously. Fas, FasL and Bax may be involved in the induction of cell apoptosis. Bcl-2 probably prevents the cell apoptosis and provides a survival signal for cells. Rb and P53 may play a critical role in monitoring and maintaining the normal neural precursor cell to proliferation and differentiation.