Co-transplantation of Schwann cells and bone marrow stromal cells versus single cell transplantation on repairing hemisected spinal cord injury of rats

BACKGROUND： Bone marrow stromal cells （BMSCs） or Schwann cells （SCs） transplantation alone can treat spinal cord injury. However, the transplantation either cell-type alone has disadvantages. The co-transplantation of both cells may benefit structural reconstruction and functional recovery of spinal nerves. OBJECTIVE： To verify spinal cord repair and related mechanisms after co-transplantation of BMSCs and SCs in a rat model of hemisected spinal cord injury. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Department of Histology and Embryology, Mudanjiang Medical College from January 2008 to May 2009. MATERIALS： Rabbit anti-S-100, glial fibrillary acidic protein, neuron specific enolase and neurofilament-200 monoclonal antibodies were purchased from Sigma, USA. METHODS： A total of 100 Wistar rats were used in a model of hemisected spinal cord injury. The rats were randomly assigned to vehicle control, SCs transplantation, BMSCs transplantation, and co-transplantation groups; 25 rats per group. At 1 week after modeling, SCs or BMSCs cultured in vitro were labeled and injected separately into the hemisected spinal segment of SCs and BMSCs transplantation groups through three injection points [5 μL （1 x 107 cells/mL）] cell suspension in each point）. In addition, a 15 μL 1 × 10^7 cells/mL SCs suspension and a 15 μL 1 × 10^7 cells/mL BMSC suspension were injected into co-transplantation group by the above method. MAIN OUTCOME MEASURES： The Basso-Beattie-Bresnahan （BBB） locomotor rating scale and somatosensory evoked potential （SEP） tests were used to assess the functional recovery of rat hind limbs following operation. Structural repair of injured nerve tissue was observed by light microscopy, electron microscopy, immunohistochemistry, and magnetic resonance imaging （MRI）. In vivo differentiation, survival and migration of BMSCs were evaluated by immunofluorescence. RESULTS： BBB scores were significantly greater in all three transplantation groups compared with vehicle control group 8 weeks after transplantation. In particular, the co-transplantation group displayed the highest scores among the groups （P 〈 0.05）. Moreover, recovery of SEP latency and amplitude was observed in all the transplantation groups, particularly after 8 weeks. Again, the co-transplantation group exhibited the greatest improvement （P 〈 0.05）. In the co-transplantation group, imaging showed a smooth surface and intact inner structure at the injury site, with no scar formation, and a large number of orderly cells at the injured site. Axonal regeneration, new myelination, and a large amount of cell division were detected in the co-transplantation group by electron microscopy. Neuron specific enolase （NSE）- and glial fibriilary acidic protein （GFAP）-positive cells were observed in the spinal cord sections 1 week following co-transplantation by immunofluorescence staining. CONCLUSION： Co-transplantation of SCs and BMSCs effectively promoted functional recovery of injured spinal cord in rats compared with SCs or BMSCs transplantation alone. This repair effect is probably achieved because of neuronal-like cells derived from BMSCs to supplement dead neurons in vivo.