Ultimately, it is important to address fundamental issues such as whether human iPSCs can efficiently differentiate into therapeutically relevant cells like dopaminergic neurons as hESCs can, and whether such cells are functional both in vitro and in vivo. Although neurons expressing tyrosine hydroxylase (TH) have been generated from human iPSCs [8,9] and functional dopaminergic neurons have been derived from mouse iPSCs [10], it remains unknown whether authentic substantia nigra (A9) dopaminergic neurons can be efficiently generated from human iPSCs, and whether such cells will function in vivo for potential cell therapy. Thus, there is a lack of robust culture systems for efficient generation of functional A9 dopaminergic neurons from human iPSCs.
