While sporadic PD cases are the most prevalent, and lack specific causative genes and a definite genetic basis, there still exists a barrier toward making any genotypic verification from the obtained differentiated cells (Park et al., 2008a). Previously, studies on PD animal models and ESC-derived dopaminergic transplantation has shown to be successful (Ganat et al., 2012; Grealish et al., 2014; Kang et al., 2014). Neuroprogenitor cells (NPCs) differentiated from iPSCs were transplanted in mouse fetal brain and were able to migrate into various regions of the brain, differentiate into both glia and neurons, and integrate into pre-existing brain network (Wernig et al., 2008). When neurons were transplanted, they exhibited a normal behavior and started branching and forming synapses. Eventually, they matured releasing dopamine and thus reducing the motor manifestations of PD in PD rat and monkey models (Wernig et al., 2008; Hallett et al., 2015; Han et al., 2015). Applying such cell therapy for PD in particular is very promising and is under a lot of extensive research for better optimization before reaching human clinical trials.
