Neuron-specific in vitro screening strategies have the potential to accelerate the evaluation of chemicals or nanomaterials for neurotoxicity. We examined the effect of lithium ion, which is known to inhibit neurite outgrowth in neuron monocultures, on rat cortex progenitor cell cultures which differentiate into neural and glial cells during the exposure period. Beta-III-tubulin positive neurons were identified after 5 days in culture and neurite length increased significantly with time. Expression of glial fibrillary acidic protein, an astrocyte marker, also increased with time. Neurite outgrowth was influenced by cell cell spacing. After 10 days, cultures seeded at 50k cells/cm2 had significantly shorter neurites than cultures seeded at densities up to 150k cells/cm2. Lithium chloride (LiCl) effects were studied over 10 days of exposure. Culture-level response was evaluated with an assay quantifying adenosine triphosphate (ATP) levels. At intermediate timepoints, cultures exposed to 30 mmol/L or 10 mmol/L LiCl had significantly lower levels than control cultures and no neurons were observed after 10 days of exposure. Cultures exposed to 0.3 mmol/L to 3.0 mmol/L LiCl exhibited concentration-dependent decreases in neurite outgrowth after 10 days of exposure. The progenitor cell culture was sensitive to lower concentrations of lithium chloride than mature neural cultures. Length of longest neurite, a simpler parameter to measure, was as sensitive as total neurite outgrowth. This work demonstrates that neurite outgrowth in differentiating progenitor cell cultures can be a sensitive endpoint at non-cytotoxic exposure conditions.
Pub Type: Journals
neurite outgrowth, progenitor cells, lithium chloride