[Morphological research on brain development and expression of vital cytokines in brain of human 6-8 week old embryo aborted for unexpected cause].

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.