Co-Transplantation of Human Umbilical Cord Mesenchymal Stem Cells and Human Neural Stem Cells Improves the Outcome in Rats with Spinal Cord Injury

Neural stem cells (NSCs) and mesenchymal stem cells (MSCs) are promising graft materials for cell therapies in spinal cord injury (SCI) models. Previous studies have demonstrated that MSCs can regulate the microenvironment of NSCs and promote their survival rate. Furthermore, several studies indicate that MSCs can reduce stem cell transplantation-linked tumor formation. To our knowledge, no previous studies have determined whether co-transplantation of human umbilical cord mesenchymal stem cells (hUC-MSCs) and human neural stem cells (hNSCs) could improve the outcome in rats with SCI. Therefore, we investigated whether the transplantation of hUC-MSCs combined with hNSCs through an intramedullary injection can improve the outcome of rats with SCI, and explored the underlying mechanisms. In this study, a moderate spinal cord contusion model was established in adult female Wistar rats using an NYU impactor. In total, 108 spinal cord-injured rats were randomly selected and divided into the following five groups: 1) hUC-MSCs group, 2) hNSCs group, 3) hUC-MSCs+hNSCs group, 4) PBS (control) group, and 5) a Sham group. Basso, Beattie and Bresnahan (BBB) behavioral test scores were used to evaluate the motor function of all animals before and after the SCI weekly through the 8th week. Two weeks after transplantation, some rats were sacrificed, immunofluorescence and immunohistochemistry were performed to evaluate the survival and differentiation of the transplanted stem cells, and brain-derived neurotrophic factor (BDNF) was detected by ELISA in the injured spinal cords. At the end of the experiment, we evaluated the remaining myelin sheath and anterior horn neurons in the injured spinal cords using Luxol Fast Blue (LFB) staining. Our results demonstrated that the surviving stem cells in the hUC-MSCs+hNSCs group were significantly increased compared with those in the hUC-MSCs alone and the hNSCs alone groups 2 weeks post-transplantation. Furthermore, the results of the BBB scores and the remaining myelin sheath evaluated via LFB staining in the injured spinal cords demonstrated that the most significantly improved outcome occurred in the hUC-MSCs+hNSCs group. The hUC-MSCs alone and the hNSCs alone groups also had a better outcome compared with that of the PBS-treated group. In conclusion, the present study demonstrates that local intramedullary subacute transplantation of hUC-MSCs, hNSCs, or hUC-MSCs+hNSCs significantly improves the outcome in an in vivo moderate contusion SCI model, and that co-transplantation of hUC-MSCs and hNSCs displayed the best outcome in our experiment.