A long and winding road: Differentiating human embryonic stem cells into dopaminergic neurons

Abstract: Parkinson’s disease is a progressive neurodegenerative disorder. Since the motor manifestations of the disease is associated with the loss of dopaminergic (DAergic) neurons in the substantia nigra pars compacta, cell replacement therapy is a promising approach for treatment. Although several different cell types have been used in clinical trials, with the recent findings of somatic cell nuclear transfer in humans, human embryonic stem cells (hESCs) offer a promising “personalized” source of cells in this quest. In the present study, we established a simple protocol for large-scale generation of dopaminergic neurons from hESCs using PA6 cells as feeders. We showed that the intermediate cell type, DAergic neural progenitors (NP), generated during the differentiation could be expanded for long time and cryopreserved without loosing their full capacity to differentiate into DAergic neurons. We further revealed that within the heterogenous PA6 population, adipocytes robustly express all the factors previously identified to be associated with SDIA. Coculturing with PA6-derived adipocytes reliably promoted the dopaminergic differentiation of the hESCs. Moreover, we identified three candidate molecules that might be involved in the SDIA of PA6 and PA6-derived adipocytes. We also demonstrated that S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin A (DZNep) efficiently induced apoptosis in proliferating neural progenitors through the TRAIL pathway, and promoted the DAergic differentiation of the hESCs. Additionally, we also identified twelve candidate surface markers that can be used in MACS for purifying DAergic neural progenitors within the heterogeneous population.