Figure 5. hiPS-derived OL specification by instruction through the specific culture medium.

Human pluripotent stem cells can be obtained from skin fibroblasts, by introducing the 4 transcription factors described by Takahashi and Yamanaka (2006). Then, the components of the culture medium direct and determine the fate of hiPS. Our culture medium previously designed to favor the OL phenotype when starting from neural stem cells (Espinosa et al., 2002), needed to be enriched with the specific molecules present during the development of the CNS to successfully direct human induced pluripotent stem cells to the neural and OL phenotype (see pink highlighted area). Once this transition has been accomplished, OL undergo sequential morphological changes from OLP and acquire characteristics inherent to a functional OL. A partial list of OL markers below each developmental stage is not exhaustive but represents frequently used markers to identify OLs and their specific developmental stage. The main difference between the culture medium for lineage progression and maintenance of hiPS-derived OL is that they need N2 while in the progenitor stage, and IGF-1 + T3 when a mature phenotype is desired. When starting cultures from brain-derived neural stem cells, we have previously described the neural stem cell medium (STM; Espinosa-Jeffrey et al., 2002); OL specification medium (OSM; Espinosa-Jeffrey et al., 2002); glia defined medium (GDM; Espinosa de los Monteros and de Vellis, 1996); OLDEM (Espinosa de los Monteros et al,1988, 1997). Chart Modified from (Espinosa-Jeffrey et al., 2009).