Many previous cell transplantation therapies have been approached such as peripheral nerve bridges, Schwann cells, olfactory glia, mesenchymal stem cells and NSCs (Plant et al., 2001; Barry and Murphy, 2004; Ramer et al., 2004; Cummings et al., 2005; Parr et al., 2008). Such therapies function to ameliorate the existing damage and prevent its further exacerbation by providing a scaffold to bridge the lesion, replace the host dead or lost neurons or glia, promote axonal regeneration and overcome glial scar formation (Bregman et al., 1997; Jones et al., 2001; Raisman, 2001; Ikegami et al., 2005; Donnelly and Popovich, 2008). In SCI, the main drawback to regeneration is the inability of the CNS neurons to regenerate axons that can cross through the inhibitory milieu of the glial scar and the injured lesion (Horner and Gage, 2000). Certain studies on rats showed promise that this can be overcome by using iPSCs as these reprogrammed iPSC neurons can extend many axons over very long distances and form synapses with host rat neurons (Parr et al., 2008; Romanyuk et al., 2015).
