Transplantation of Schwann cells and olfactory ensheathing glia after spinal cord injury: does pretreatment with methylprednisolone and interleukin-10 enhance recovery?

Methylprednisolone (MP) and interleukin-10 (IL-10) are tissue protective acutely after spinal cord injury (SCI); their combination offers additive protection (Takami et al., 2002a). Our study examined if acute administration of MP (30 mg/kg i.v. at 5 min, and 2 and 4 h after injury) and IL-10 (30 mg/kg i.p. at 30 min after injury) increases the efficacy of Schwann cell (SC) or SC plus olfactory ensheathing glia (SC/OEG) grafts transplanted into rat thoracic cord 1 week after contusive injury. Efficacy was determined by histology, anterograde and retrograde tracing, immunohistochemistry for gliosis and specific nerve fibers, and several behavioral tests. Administration of MP/IL-10 or SC or SC/OEG transplantation significantly increased the total volume of a 9-mm segment of cord encompassing the injury site at 12 weeks. The combination of either SC or SC/OEG transplantation with MP/IL-10 most significantly reduced cavitation. The individual treatments all significantly increased the volume of normal-appearing tissue compared to injury-only controls; however, significant decreases in the volume of normal-appearing tissue were seen when MP/IL-10 and cell grafts were combined compared to MP/IL-10 alone. SC/OEG grafts were effective in promoting serotonergic fiber growth into the graft and led to more reticulospinal fibers caudal to the graft; combination with MP/IL-10 did not further increase fiber number. Only the combination of MP/IL-10 with SC/OEG transplants significantly improved gross locomotor performance (BBB scores) over injury-only controls. MP/IL-10 given prior to SC-only transplants, however, worsened behavioral outcome. Because beneficial effects of MP/IL-10 were not always additive when combined with cell transplantation, we need to understand (1) how tissue protective agents may transform the milieu of the injured spinal cord to the benefit or detriment of later transplanted cells and (2) whether neuroprotectants need to be re-administered at the time of cell grafting or less invasive transplantation techniques employed to reduce damage to tissue spared by an earlier protection strategy.