| Abstract No.: | 217 |
| Country: | Canada |
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| Title: | STEM CELLS FOR NERVE REGENERATION |
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| Authors/Affiliations: | 1 Raj Midha*;
1 University of Calgary, AB, Canada
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| Content: | Previous work has shown that clones of progenitor cells isolated from the dermis of the neonatal and adult murine skin have the ability to differentiate in vitro into neural crest cell types, including peripheral neurons and glia (1). These cells, termed skin-derived precursors (SKPs), also respond to the milieu of the regenerating nerve in vivo and are able to differentiate into GFAP/S-100β positive Schwann cells that myelinate regenerating axons when transplanted distal to a nerve injury (2). In our ongoing studies, we are exploring the viability and differentiation of SKPs in various nerve injury models to ascertain their role in promoting nerve regeneration. To this end, the sciatic nerves of CD-1 mice were transected and chronically denervated. SKPs or SKP-SCs were injected into the subepineurium distal to the transection either immediately following injury or after 8 weeks of denervation. Immunohistochemical analysis 2-8 weeks following transplantation revealed survival and differentiation of both naïve and pre-differentiated SKPs, with 73% of the surviving cells injected after established chronic denervation expressing Schwann cell markers. Eight weeks following SKP transplant, survival of pre-differentiated SKPs was significantly higher than that of the naïve preparation. Next, we examined the potential for SKPs to improve nerve regeneration across a gap bridged by a freeze-thawed nerve graft. Donor sciatic nerves were collected from adult Lewis rats and decellularized by repeated cycles of freezing in liquid nitrogen and thawing in warm water bath. These syngeneic grafts were then used to bridge a 12 mm nerve injury gap in Lewis rat recipients and SKPs-SCs or cultured Schwann cells were injected into the grafted area. Immunohistology after 4 weeks showed survival of both cell types and early regeneration in SKP seeded grafts (as deemed by NF-stained axon counts) was comparable to those seeded with Schwann cells. Morphometrical (fiber diameter, N-ratio, axon counts) and electrophysiological measurements (distal latency and CMAP amplitude) of cell-treated nerve segments after 8 weeks survival showed significantly improved regeneration indices as compared to diluent controls. Furthermore, when the integration of host Schwann cells into the graft was inhibited by local application of mitomycin C, SKP seeded grafts demonstrated even more pronounced disparity in outcomes when compared to controls. We therefore conclude that SKPs represent an accessible, autologous source of Schwann cells for transplantation therapies that have the potential to survive over long time periods and improve nerve regeneration outcomes.
1. Toma et al., Nature Cell Biol, 2001
2. McKenzie et al., J. Neurosci., 2006
Funded by: Canadian Institute for Health Research and David Kline Research Award (AANS/CNS Spine and Nerve Joint Section)
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