The Pattern of Cell Proliferation and Apoptosis in Human Embryonic and Fetal Brain

ABSTRACT

BACKGROUND: Cell proliferation and apoptosis account for the major morphogenetic mechanisms during development of the central nervous system. We investigated these processes in developing human brains. METHODS: We examined human embryonic and fetal brains. Cell proliferation was analysed by classical histology and MIB-1 immunohistochemistry; cell death was investigated by the TdT-mediated dUTP-biotin nick end labelling method. RESULTS: Most proliferating cells were observed in the ventricular zone (VZ) in the 3rd-10th week of gestational age (GA), and in both the VZ and the subventricular zone (SV) in the 19-24th week of GA. The proliferation index of the VZ was highest in the 8th week of GA and then decreased as the GA advanced. Apoptotic cells were observed in the VZ as early as the 5th week of GA. They were also observed in the intermediate zone in the 19-24th week of GA, although they were significantly lower in amount compared to that in the VZ and SV. CONCLUSIONS: These results suggest that apoptosis occurring early in the embryonic period is related to a cellular mechanism which selects and determines the cells that are committed to migration and differentiation during the development of the human brain.