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 cellsinto the contusion model of spinal cord injury (SCI) promotes locomotor function and improvesfunctional recovery, it induces a painful response, Allodynia. Different studies indicatethat bone marrow stromal cells (BMSCs) and Schwann cells (SCs) can improvelocomotor recovery when transplanted into the injured rat spinal cord. Since these cellsare commonly used in cell therapy, we investigated whether co-transplantation of thesecells leads to the development of Allodynia.Materials and Methods: In this experimental research, the contusion model of SCI was inducedby 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 culturedand prelabeled with 5-bromo-2-deoxyuridine (BrdU) and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanineperchlorate (DiI) respectively. The rats were divided into five groupsof 8 including: a control group (laminectomy only), three experimental groups (BMSC, SCand 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 shamgroup received serum only. Locomotion was assessed using Basso, Beattie and Bresnahan(BBB) test and Allodynia by the withdrawal threshold test using Von Frey Filamentsat 1, 7, 14, 21, 28, 35, 42, 49 and 56 days after SCI. The statistical comparisons betweengroups were carried out by using repeated measures analysis of variances (ANOVA).Results: Significant differences were observed in BBB scores in the Co- transplant groupcompared to the BMSC and SC groups (p< 0.05). There were also significant differencesin 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 meansshowed that co-transplation improved functioning but greater Allodynia compared to theother experimental groups.Conclusion: The present study has shown that, although transplantation of BMSCs, SCsand a combination of these cells into the injured rat spinal cord can improve functionalrecovery, it leads to the development of mechanical Allodynia. This finding indicates thatstrategies to reduce Allodynia in cell transplantation studies are required.