Image-Based Analysis of a Human Neurosphere Stem Cell Model for the Evaluation of Potential Neurotoxicants

Developmental neurotoxicity (DNT) of environmental chemicals is a threat to human health, as the developing nervous system is particularly susceptible to toxicant exposure. Resulting neurological deficits may have longterm financial and emotional impacts on families and society. Current DNT testing guidelines involve use of animal models; primarily rodents, and the large quantities needed can be extremely time- and cost-intensive; particularly due to the backlog of chemicals requiring testing. This demand, in addition to current and future proposed regulations on the use of animal test models makes it imperative to find new models that reduce animal experimentation while providing a suitable method to test new chemicals. Three-dimensional cell models, incorporating human neural stem cells (hNSCs) aggregated into neurospheres, are proposed as a viable alternative for use in DNT testing. The in vitro system can recapitulate the processes of brain development, including proliferation, migration, differentiation and apoptosis. By including human instead of murine cells, the system also meets recommendations to circumvent the drawback of species differences between in vivo testing and actual exposure effects. Here we demonstrate a 3D neurosphere model, composed of hNSCs, to conduct toxicity testing of several potential neurotoxicants. A specialized spheroid microplate was used to create and maintain cells in the 3D model. 3D neurosphere proliferation, multipotency, and continued differentiation into neurons, astrocytes, and oligodendrocytes was initially validated. Neurotoxicity testing was then performed using neurospheres maintained in the 3D spheroid plate. Induced levels of oxidative stress, apoptotic and necrotic activity within treated neurospheres were evaluated and compared to negative control spheres.