Comparison between proliferative and neuron-like SH-SY5Y cells as an in vitro model for Parkinson disease studies

The molecular mechanisms underlying the cellular lost found in the nigrostriatal pathway during the progression of Parkinson's disease (PD) are not completely understood. Human neuroblastoma cell line SH-SY5Y challenged with 6-hydroxydopamine (6-OHDA) has been widely used as an in vitro model for PD. Although this cell line differentiates to dopaminergic neuron-like cells in response to low serum and retinoic acid (RA) treatment, there are few studies investigating the differences between proliferative and RA-differentiated SH-SY5Y cells. Here we evaluate morphological and biochemical changes which occurs during the differentiation of SH-SY5Y cells, and their responsiveness to 6-OHDA toxicity. Exponentially growing SH-SY5Y cells were maintained with DMEM/F12 medium plus 10% of fetal bovine serum (FBS). Differentiation was triggered by the combination of 10 µM RA plus 1% of FBS during 4, 7 and 10 days in culture. We found that SH-SY5Y cells differentiated for 7 days show an increase immunocontent of several relevant neuronal markers with the concomitant decrease in non-differentiated cell marker. Moreover, cells became two-fold more sensitive to 6-OHDA toxicity during the differentiation process. Time course experiments showed loss of mitochondrial membrane potential triggered by 6-OHDA (mitochondrial dysfunction parameter), which firstly occurs in proliferative than neuron-like differentiated cells. This finding could be related to the increase in the immunocontent of the neuroprotective protein DJ-1 during differentiation. Our data suggest that SH-SY5Y cells differentiated by 7 days with the protocol described here represent a more suitable experimental model for studying the molecular and cellular mechanisms underlying the pathophysiology of PD.