Co- transplantation of Bone Marrow Stromal Cells with Schwann Cells Evokes Mechanical Allodynia in the Contusion Model of Spinal Cord Injury in Rats

Objective: Several studies have shown that, although transplantation of neural stem cells into the contusion model of spinal cord injury (SCI) promotes locomotor function and improves functional recovery, it induces a painful response, Allodynia. Different studies indicate that bone marrow stromal cells (BMSCs) and Schwann cells (SCs) can improve locomotor recovery when transplanted into the injured rat spinal cord. Since these cells are commonly used in cell therapy, we investigated whether co-transplantation of these cells leads to the development of Allodynia. Materials and Methods: In this experimental research, the contusion model of SCI was induced by laminectomy at the T8-T9 level of the spinal cord in adult female wistar rats (n=40) weighting (250-300g) using the New York University Device. BMSCs and SCs were cultured and prelabeled with 5-bromo-2-deoxyuridine (BrdU) and 1,1ʹ-dioctadecyl-3,3,3ʹ,3ʹ-tetramethylindocarbocyanine perchlorate (DiI) respectively. The rats were divided into five groups of 8 including: a control group (laminectomy only), three experimental groups (BMSC, SC and Co-transplant) and a sham group. The experimental groups received BMSCs, SCs, and BMSCs and SCs respectively by intraspinal injection 7 days after injury and the sham group received serum only. Locomotion was assessed using Basso, Beattie and Bresnahan (BBB) test and Allodynia by the withdrawal threshold test using Von Frey Filaments at 1, 7, 14, 21, 28, 35, 42, 49 and 56 days after SCI. The statistical comparisons between groups were carried out by using repeated measures analysis of variances (ANOVA). Results: Significant differences were observed in BBB scores in the Co- transplant group compared to the BMSC and SC groups (p < 0.05). There were also significant differences in the withdrawal threshold means between animals in the sham group and the BMSC, SC and the Co-transplant groups (p < 0.05).BBB scores and withdrawal threshold means showed that co-transplation improved functioning but greater Allodynia compared to the other experimental groups. Conclusion: The present study has shown that, although transplantation of BMSCs, SCs and a combination of these cells into the injured rat spinal cord can improve functional recovery, it leads to the development of mechanical Allodynia. This finding indicates that strategies to reduce Allodynia in cell transplantation studies are required.