CXCR4 and myeloid sarcoma: Manipulation of chemotactic pathways such as the C-X-C chemokine receptor type 4, pharmacogenetic targets such as the FGF-2 and Anosmin-1, or guidance cues such as semaphorin-3A and 3F, might promote repopulation of MS lesions by OPCs, as it was shown in experimental in vivo or in vitro models for MS and in human MS brain tissue (Williams et al., 2007; Carbajal et al., 2010; Clemente et al., 2011).