Therapeutic Application of Human Tonsil-Derived Mesenchymal Stem Cells for Peripheral Nerve Regeneration

Since Schwann cells (SCs) provide structural support and guidance for axonal regeneration by producing neurotrophic factors and adherent molecules, SCs are indispensable mediators of the repair process of the injured nervous tissue. Although autologous SCs transplantation has shown promising clinical results, this procedure is limited by donor site morbidity and difficulty to generate sufficient number of cells. We have evaluated that the differentiation of tonsil-derived mesenchymal stem cells (T-MSCs) into SC-like cells (T-MSC-SCs) can be an alternative cell source for the generation of SCs. To neurosphere formation, T-MSCs were cultured in DMEM with 20 ng/ml bFGF, 20 ng/ml EGF, 2% B27 supplement and then to differentiate into SCs, mechanically dissociated cells were grown in DEME/F12 with 10% FBS, 5 ng/ml PDGF, 10 ng/ml bFGF, and 200 ng/ml heregulin. At neurosphere stage, all of Schwann cell markers including CAD19, GFAP, MBP, NGFR, S100B and Krox20 were up-regulated. However, in fully differentiated stage, only GFAP, NGFR, S100B and Krox20 were up-regulated. The expression of CAD19 and MBP were down-regulated in differentiated SCs. Myelination of axons was observed by coculture of mouse dorsal root ganglion neurons with differentiated SCs. The application of T-MSC-SCs to a mouse model with sciatic nerve injury showed marked improvement in gait and promoted regeneration of damaged nerves. These results suggest that the transplantation of human T-MSCs might be suitable for assisting in peripheral nerve regeneration.