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BACKGROUND:Olfactory ensheathing cell(OEC)transplantation promotes repair of spinal cord injury. Neural regeneration inhibits binding of the myelin protein Nogo to its receptor(NgR),activates downstream inhibitory signal RhoA, and leads to axonal degeneration.OBJECTIVE: To determine the relationship between OECs transplantation for spinal cord injury and NogoA, NgR, and RhoA protein expression in the damaged zone.DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed from September 2006 to May 2007 at the Key Laboratory of Environment and Genes in Xi'an Jiaotong University School of Medicine, China.MATERIALS: OECs were harvested from healthy, adult, male, Sprague Dawley rats aged 6 months. Mouse anti-rat NogoA, NgR, and RhoA monoclonal antibodies were utilized for detection.METHODS: A total of 40 adult Sprague Dawley rats were randomly assigned to four groups: normal, model, OECs, and DF12, with 10 animals in each group. Transverse section spinal cord injury was established in the OECs and DF12 groups, followed by injection of 1 μL OECs suspension(1×108/mL)or equivalent DF12 medium at 1 mm above and below the injury site.MAIN OUTCOME MEASURES: Immunohistochemistry and Western blot were utilized to detect NogoA, NgR, and RhoA expression in the spinal cord injury lesions. Morphological changes were observed by argyrophilia staining, and lower extremity function of the animals was assessed using Basso, Beattie, and Bresnahan scores.RESULTS: Eight weeks following OECs transplantation, a significant increase in new axons was observed in the OECs group, and nerve fibers crossed the injury site to repair spinal cord injury.Qualitative and quantitative results from the OECs group were superior to the model and DF12 groups. At 8 weeks after transplantation, Basso, Beattie, and Bresnahan scores were significantly greater in the OECs group compared with the model and DF12 groups(P< 0.01), but expression of NogoA, NgR, and RhoA protein was significantly decreased compared with the model and DF12 groups(P< 0.05).CONCLUSION: OEC transplantation could inhibit NogoA, NgR, and RhoA expression in spinal cord injury lesions, thereby promoting repair of spinal cord injury.