Ascorbic acid increases the yield of dopaminergic neurons derived from basic fibroblast growth factor expanded mesencephalic precursors

CNS precursors derived from E12 rat mesencephalon proliferate in the presen ce of basic fibroblast growth factor and differentiate in vitro into functi onal dopaminergic neurons, which upon transplantation alleviate behavioral symptoms in a rat model of Parkinson's disease. Here we show that the effic iency of dopaminergic differentiation decreases in the mesencephalic precur sors that were proliferated or passaged for extended periods in vitro. Asco rbic acid treatment restored dopaminergic differentiation in these precurso rs and led to a greater than 10-fold increase in dopamine neuron yield comp ared with untreated cultures. The effect of ascorbic acid was stereospecifi c and could not be mimicked by any other antioxidants. The expression of so dium-dependent vitamin C transporter, a recently identified stereospecific ascorbic acid transporter, was maintained in mesencephalic precursors for e xtended in vitro periods. Pre-treatment of in vitro expanded mesencephalic precursors with ascorbic acid might facilitate the large-scale generation o f dopaminergic neurons for clinical transplantation.