FN1 and myeloid sarcoma: In MS lesions, fibronectin dimers are cross-linked to form aggregates and hyaluronan is present in its high molecular weight form, and their persistent presence contribute to the non-permissive nature of this scar for remyelination and to impaired remyelination by inhibiting OPC differentiation (Back et al., 2005; Sisková et al., 2006; Stoffels et al., 2013a).