Isolation of adult stem cells and their differentiation to Schwann cells

Peripheral nerve injuries are an economic burden for society in general and despite advanced microsurgical reconstruction of the damaged nerves the functional result is unsatisfactory with poor sensory recovery and reduced motor functions (Wiberg and Terenghi, Surg Technol Int 11:303-310, 2003). In the treatment of nerve injuries transplantation of a nerve graft is often necessary, especially in nerve gap injuries. Schwann cells (SC) are the key facilitators of peripheral nerve regeneration and are responsible for the formation and maintenance of the myelin sheath around axons in peripheral nerve fibers. They are essential for nerve regeneration after nerve injuries as they produce extracellular matrix molecules, integrins, and trophic factors providing guidance and trophic support for regenerating axons (Wiberg and Terenghi, Surg Technol Int 11:303-310, 2003; Bunge, J Neurol 242:S19-21, 1994; Ide, Neurosci Res 25:101-121, 1996; Mahanthappa et al. J Neurosci 16:4673-4683, 1996). However, the use of ex vivo cultured SC within conduits is limited in its clinical application because of the concomitant donor site morbidity and the slow growth of these cells in vitro (Tohill et al. Tissue Eng 10:1359-1367, 2004). Mesenchymal stem cells (MSC or bone marrow stromal cells) and adipose-derived stem cells (ASC) are easily accessible non-hematopoietic stem cells that have proven essential for research purposes due to their plasticity and ability to differentiate into several functional cell types. This alternative source of cells is relatively simple to isolate and expand in culture. We have demonstrated that MSC and ASC can trans-differentiate along a SC lineage with functional properties and growth factor synthesis activities similar to those of native SC and could provide nerve fiber support and guidance during nerve regeneration.