For the midbrain dopaminergic neurons lost in Parkinson’s disease in particular, preclinical animal studies using hESC and iPSC-derived neurons have proven sufficiently promising to justify both the scaled production of cells appropriate for clinical transplantation (Hallett et al., 2015; Hargus et al., 2010; Kikuchi et al., 2011; Kriks et al., 2011; Roy et al., 2006; Takahashi et al., 2009), and the design of new clinical trials by which to evaluate the efficacy of those cells in disease amelioration. To that end, new efforts have been initiated both in the US and UK, respectively by Studer and Barker and their colleagues using hESC-derived dopaminergic neurons as donor cells, and in Japan, by Takahashi and colleagues with human iPSC-derived neurons. While each study is promising, having inculcated lessons from past fetal tissue-based studies (Barker et al., 2015) (Moore et al., 2014), a number of issues may still limit the promise of this approach. As noted, past trials of fetal human midbrain tissue implanted into the striata of Parkinson’s patients yielded inconsistent results, with durable efficacy in selected cases (Kefalopoulou et al., 2014),
