Targeting Notch Signalling to Generate Bone Marrow-derived Schwann Cells for Transplantation in Spinal Cord Injury

Abstract

There has been significant interest in Schwann cell transplantation for cell therapy in spinal cord injury. Schwann cells secrete neurotrophic factors, phagocytose inhibitory myelin debris, and remyelinate denuded axons. Although readily harvested from the sural nerve, there is donor site morbidity and hence there remains the need to find an alternative source of easily expansible autologous Schwann cells. Our strategy of deriving Schwann cells from bone marrow stromal cells exploited exposure to growth factors to generate Schwann cell–like cells followed by coculture with purified dorsal root ganglia (DRG) neurons to provide juxtacrine cues mediating commitment to the Schwann cell fate. Immunocytochemistry demonstrated expression of Notch ligands DLL1 and Jagged1 on DRG neurons, while the Notch-1 receptor was expressed by bone marrow–derived Schwann cell–like cells. In cocultures with DRG neurons during which Schwann cell–like cells progressed towards fate commitment, translocation of the Notch intracellular domain to the nucleus was indicative of Notch signalling. Subsequently, ErbB2/B3 receptor heterodimers were upregulated on immunocytochemistry and Western blotting, allowing neuregulins to drive Schwann cell–like cells to fate commitment. Conversely, addition of the Notch inhibitor DAPT led to decreased expression of ErbB receptors. In ongoing work, we are using a neuron-free coculture platform to present Notch ligands to drive Schwann cell–like cells to fate commitment. By understanding the mechanism of coculture-induced fate commitment, we hope to generate an unlimited supply of autologous Schwann cells for use in cell therapy.