The studies described thus far used hGPCs derived from human brain tissue, of both adult and fetal origin. Yet a number of groups have reported protocols by which GPCs, and their derived astrocytes and oligodendrocytes, might be alternatively derived from pluripotential stem cells (Hu et al. 2009; Izrael et al. 2007; Wang et al. 2013). These protocols have improved over the past 2 years in both efficiency and speed, so that bipotential oligodendrocyte-astrocyte progenitors may be produced in quantity from pluripotential cells in less than three months, while myelinating oligodendroglia may be produced within four (Douvaras et al. 2014; Piao et al. 2015; Stacpoole et al. 2013). The cells produced by these protocols are at least as efficient at myelinogenesis in vivo as their tissue-derived counterparts, myelinating most axons within the hypomyelinated shiverer forebrain within several months after neonatal transplant (Figure 4), and rescuing at least a fraction of neonatally-engrafted shiverer mice from otherwise certain death (Wang et al. 2013). Yet while these hGPC differentiation protocols were developed so as to scale up production of hGPCs to clinically-useful levels, the
