In Vitro Sensitivity of Neural Stem Cell to Low-Dose Radiation

Abstract

With the prolongation of survival time of brain tumor patients, radiation-induced cognitive impairment has attracted much attention. Despite clinical research reveal that radiation-induced cognitive deficits was accompanied with significant decline of neurogenesis,the underlying mechanisms at cellular level remained unclear. Neural stem cells (NSCs), which play an important role in organization of the brain, are responsible for neurogenesis. Therefore, it is necessary to investigated several biological changes in hippocampus neural stem cells after exposure to X-rays irradiation. Primary cultures of neural stem cell were prepared from hippocampus of fetal E16-18 C57BL/6 mouse. The rate of cell apopotosis and the variation of cell cycle were observed by flow cytometry using cell cycle and apoptosis detection kit. Furthermore, the cell proliferation influenced by different dose of X-Rays was determined by cell counts. Finally,the expression of neural stem cells markers nestin, neuronal marker Tuj1, astrocyte marker GFAP were detected by immunofluorescent analysis. Flow cytometry results suggested that the apoptosis rate of neural stem cells increased at 24h, 48h and 72h after irradiation with 1Gy (P<0.01). Besides, even 0.2Gy of X-Rays significantly decreased the proliferation of neural stem cells 24h, 48h and 72h post irradiation (P<0.01). Irradiated cells showed a trend of G1 accumulation at 6h and 12h after irradiation with 0.2Gy. Moverover, the results suggested that 0.5Gy of X-Rays attenuated the ability of neural stem cell to differentiate into neurons 72h post irradiation (P<0.05), but no significant change in the positive rate of astrocyte (P>0.05). Low dose irradiation can lead to neurogenesis deficits,primarily by inducing apoptosis, affecting neural stem cell proliferation and differentiation. Irradiation results in dose-dependent inhibition of hippocampal neurogenesis. Besides, Neurogenesis occurs throughout the whole of the developing central nervous system (CNS), while it occurs only in the subventricular zone (SVZ) or the hippocampus in the adult CNS. So it is important to pay attention to the protection of these area which exist neural stem cells in radiotherapy.