Abstract
Valproic acid (VPA), widely used as an antiepileptic drug, exhibits developmental neurotoxicity when exposure occurs during early or late pregnancy, resulting in various conditions ranging from neural tube defects to autism spectrum disorders. However, toxicity during the very early stages of neural development has not been addressed. Therefore, we investigated the effects of VPA in a model where human pluripotent stem cells differentiate into anterior or posterior neural tissues. Exposure to VPA during the induction of neural stem cells induced different developmental toxic effects in a dose-dependent manner. For instance, VPA induced cell death more profoundly during anteriorly guided neural progenitor induction, while inhibition of cell proliferation and enhanced differentiation were observed during posteriorly guided neural induction. Furthermore, acute exposure to VPA during the posterior induction step also retarded the subsequent neurulation-like tube morphogenesis process in neural organoid culture. These results suggest that VPA exposure during very early embryonic development might exhibit cytotoxicity and subsequently disrupt neural differentiation and morphogenesis processes.