Abstract
In the fetal brain, neural stem cells (NSCs) can proliferate by self-renewal and subsequently differentiate into neurons, astrocytes and oligodendrocytes, which construct the central nervous system. Thus, radiation damage to NSCs in the developing brain may result in serious neurological disorders, such as dysfunctions, microcephalia, and mental retardation. In this study, we investigated effects of X-irradiation on capabilities of proliferation and differentiation in NSCs derived from ES cells of C57BL/6 mice. When proliferating NSCs were irradiated with various doses of X-ray, the survival and proliferation of NSCs were affected dose-dependently. The cells irradiated with 5 Gy and over showed a remarkable decrease in number, and the cells stopped proliferation. In contrast, the cells irradiated with 1 Gy proliferated exponentially like non-irradiated cells with a lag time of about 1 day. Realtime RT-PCR and fluorescent immunostaining analysis demonstrated that the proliferating cells expressed the gene and protein of nestin, a marker for NSC. The proliferating cells were sub-cultured at day 4 after irradiation and shown to maintain potential of proliferation. When the sub-cultured cells were induced differentiation into neural cells, the cells exhibited morphological changes and differentiated into NF-H positive neurons and GFAP positive astrocytes. Gene analysis showed that expression of nestin decreased but, in contrast, expression of MAP2 and GFAP, markers for neuron and astrocyte, respectively, increased during the culture. These results suggest that the NSCs irradiated with 1 Gy maintain their capabilities for proliferation and differentiation into neural cells.
