The effects of various estrogen doses on the proliferation and differentiation of cultured neural stem cells.

The brain has long been known as a dimorphic organ and as a target of estrogen. Neurogenesis, including proliferation and differentiation of neural stem cells (NSCs), could be stimulated and regulated by estrogen. However, the dose and timing of estrogen treatment is controversial, and the underlying mechanism remains unclear. In this study, we tested the effects of various estrogen doses on the neurogenesis of NSCs derived from Sprague-Dawley rat embryos. First, we identified that the estrogen receptor-ERα, ERβ and GPR30 were highly expressed in NSCs. The results from cell cycle and Western blot analyses revealed that 10 nM 17β-estradiol (E2) treatment for 3 days significantly increased NSCs proliferation of and p-ERK1/2 expression level but that 50 nM E2 exposure markedly decreased NSCs proliferation and p-ERK1/2 expression level. According to immunofluorescence staining and Western blot analyses, 10 nM E2 treatment for 7 days significantly stimulated NSCs to differentiate into neurons and inhibited their differentiation into astrocytes. These results demonstrate that NSCs are a target of estrogen and that an appropriate dose of E2 (10 nM) can significantly increase the proliferation of NSCs and stimulate NSCs to differentiate into neurons, which contributes to knowledge regarding the regulatory effects of estrogens on neurogenesis.