Effect And Mechanism Of 17beta-estradiol On Division And Differentiation Of Rat Neural Stem Cell

Introduction Gonadal steroid hormones can act on the brain during development in many aspects both reproductive and nonreproductive including neuroendocrine function, cognitive function, and others. Most of previous studies are designed on mature neural cells whereas the role of estrogen on neural stem cell is not known yet. Neural stem cell in culture condition can not only mimic the beginning state of CNS development, but also provide a simple environment for analysis .The present study is to examine the effect on mechanism of estrogen on division and differention of the neural stem cell derived from embryonic rat cortex.Objective We examined the effet of 17beta-estradiol on division and differentiation of rat neural stem cell and the regulation of expression of estrogen receptor -alpha by its ligand, 17beta-estradiol.Methods The neural stem cells derived from 12-12.5 day embryonic rat cortex were planted in suspended condition(three-dimension)and on coverslip precoated by poly-L-lysine. The cells were exposed to 17beta-estradiol (10ng/ml) and co-incubated with BrdU to mark new DNA synthesis. Then we measured the number and diamater of neurospheres suspended in the medium and detected the BrdU-immunoreactive cells on coverslips. The expression of Estrogen receptor- a in primary neural stem cells and the cells incubated with 17 - estradiol was detected using immunochemical method.Results The number and diameter of neurospheres were both decreased markedly in the estradiol group ( P=0.006 ). No significant differences in the number of total stem cells and BrdU-immunoreactive cells was found between the estradiol and control group after 4h culture (P=0.259, P=0.067) . After 12h culture, BrdU- immunoreactive cell number was decreased in the estradiol group, compared with the control ( P=0.003). But the optical density of BrdU-immunoreactive cells was increased in estradiol group (P<0.001). Also,40% of BrdU- immunoreactive cells with processes were found in estradiol group while no process could be seen in the control. There was no differences in total cell number between the two groups ( P=0.06 ). The cells of subculturing showed obvious sensitivity to estradiol in vitro. No estrogen receptor- a was detected on neural stem cell under control condition, but ER-a immunoreactive cells were detected after estrogen incubation.Conclusions We have set up the model of neural stem cell in vitro. All results suggested that estradiol may inhibit division of neural stem cell and induce cell differentiation morphologically. No estrogen receptor expressed in neural stem cell derived from embryonic 12-12.5 day rat, and estrogen signaling may active the expression of estrogen receptor.