BACKGROUND: Previous studies have demonstrated that low-power laser (LPL) irradiation can promote the regeneration of peripheral nerves and central nerves, as well as influence cellular proliferation. Therefore, it is thought to be a potential treatment for spinal cord injury.OBJECTIVE: Utilizing histological observations and behavioral evaluations, the aim of this study was to investigate the influence of transplanted olfactory ensheathing cells (OECs), irradiated by LPL, on functional repair of rats following transversal spinal cord injury.DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at the animal experimental center in the First Affiliated Hospital of Xinjiang Medical University between January 2007 and February 2008.MATERIALS: A total of 52 Sprague Dawley rats were included in this experiment. Twelve rats were used to harvest OECs, some of which were irradiated by LPL on days 3, 5, and 7 in culture.The remaining 40 rats were used to establish T12 complete spinal cord transection injury.DMEM/F12 medium was purchased from Sigma, USA, Fluorogold was provided by Chemicon,USA, and the LY/JG650-D500-16 low-power laser was produced by Xian Lingyue Electromechanical Science And Technology Co., Ltd., China.METHODS: The successful rat models were randomly divided into three groups: OEC transplantation, LPL-irradiated OEC transplantation, and control. These animals were microinjected with OEC suspension, LPL-irradiated OEC suspension, and DMEM/F12 medium(10 μL) respectively 4 weeks after spinal cord was completely transected at the T12 level.MAIN OUTCOME MEASURES: Spinal cord injury was observed using hematoxylin-eosin staining.Expression of nerve growth factor receptor p75 and glial fibrillary acidic protein were determined using immunohistochemical staining. Regeneration of spinal nerve fibers in rats was assayed by Fluorogold retrograde labeling method. Basso, Beattie and Bresnahan (BBB) scores were used to evaluate motor functions of rat lower limbs.RESULTS: Structural disturbances were observed following spinal cord injury in each group, and a large amount of scar tissue covered the broken ends, accompanied by porosis and inflammatory cell infiltration. Following OEC transplantation, the distal end connected to the proximal end. nerve growth factor receptor p75 and glial fibrillary acidic protein immunohistochemistry revealed positive OECs in the cephalad and caudal area of rats that received LPL-irradiated OEC transplantation. In the OECs group, only glial fibrillary acidic protein staining was observed. No staining was found in the control group. Neural fibers labeled with Fluorogold extended across the lesion area and into the cephalad and caudal area in the OECs and LPL-irradiated OECs groups,but were not present in the control group. BBB scores revealed statistically significant differences among the three groups (P OECs group > control group.CONCLUSION: Transplantation of OECs and LPL-irradiated OECs promoted functional repair in the injured spinal cord of rats, although LPL-irradiated OECs resulted in greater beneficial effects.