Juxtacrine signalling via Notch and ErbB receptors in the switch to fate commitment of bone marrow-derived Schwann cells.

The phenotypic instability of adult tissue-derived Schwann cell-like cells (SCLCs) as revealed upon withdrawal of glia-inducing culture supplements limits their clinical utility for cell therapy and disease modelling. We previously overcame this limitation by co-culturing bone marrow-derived SCLCs with neurons purified from developing rat and subsequently human sensory neurons such that direct contact between cell types accomplished the cell-intrinsic switch to the Schwann cell fate. Here, our search for juxtacrine instructive signals found both Notch ligands and neuregulin-1 type III localized on the surface of DRG neurons via live cell immunocytochemistry. Bypassing ligand-induced release of the Notch intracellular domain (NICD) by transient transfection of SCLCs with the pAdlox/V5-His-NICD construct was shown to upregulate ErbB2/3. Interaction of ErbB2/3 with neuregulin-1 type III (NRG1 type III) as presented on neurons then mediated the switch to the Schwann cell fate as demonstrated by expression of S100ß/p75/ Sox10/Krox20. In contrast, treatment of cocultures with γ-secretase inhibitor perturbed Notch signalling in SCLCs and consequently deterred both upregulation of ErbB2/3 and the transition to the Schwann cell fate. Taken together, juxtacrine signalling via Notch is key to the upregulation of ErbB receptors for neuregulin-driven commitment of SCLCs to the Schwann cell fate.

Hypoxic Preconditioning of Marrow-derived Progenitor Cells As a Source for the Generation of Mature Schwann Cells.

This manuscript describes a means to enrich for neural progenitors from the marrow stromal cell (MSC) population and thereafter to direct them to the mature Schwann cell fate. We subjected rat and human MSCs to transient hypoxic conditions (1% oxygen for 16 h) followed by expansion as neurospheres upon low-attachment substratum with epidermal growth factor (EGF)/basic fibroblast growth factor (bFGF) supplementation. Neurospheres were seeded onto poly-D-lysine/laminin-coated tissue culture plastic and cultured in a gliogenic cocktail containing ß-Heregulin, bFGF, and platelet-derived growth factor (PDGF) to generate Schwann cell-like cells (SCLCs). SCLCs were directed to fate commitment via coculture for 2 weeks with purified dorsal root ganglia (DRG) neurons obtained from E14-15 pregnant Sprague Dawley rats. Mature Schwann cells demonstrate persistence in S100ß/p75 expression and can form myelin segments. Cells generated in this manner have potential applications in autologous cell transplantation following spinal cord injury, as well as in disease modeling.