BACKGROUND: It has been reported that nuclear factor-kappa B (NF- k B), activated after spinal cord injury in rats, plays a key role in inflammatory responses in the central nervous system.OBJECTIVE: To investigate the effects of transplantation of microencapsulated rabbit sciatic nerve on NF- k B expression and motor function after spinal cord injury in rats, and to compare the results with the transplantation of rabbit sciatic nerve alone.DESIGN, TIME AND SETTING: This completely randomized, controlled study was performed at the Department of Neurobiology, Medical College of Nanchang University between December 2007 and July 2008.MATERIALS: A rabbit anti-NF- k B P65 monoclonal antibody was made by the Santa Cruz Company, USA and a streptavidin peroxidase immunohistochemical kit was provided by the Sequoia Company, China.METHODS: Eight rabbits were used to prepare a sciatic nerve cell suspension that was divided into two parts: one stored for transplantation, and the other mixed with a 1.5% sodium alginate solution. One hundred and twenty adult Sprague Dawley rats weighing 220-250 g were randomly divided into four groups: the microencapsulated cell group (n = 36), the non-encapsulated cell group (n = 36), the saline group (n = 36) and the sham operation group (n = 12). The first three groups underwent a right hemisection injury of the spinal cord at the T<,10> level, into which was transplanted a gelatin sponge soaked with 10 μ L of a microencapsulated nerve tissue/cell suspension (microencapsulated cell group), a tissue/cell suspension (non-encapsulated cell group) or physiological saline (saline group). In the sham operation group the vertebrae were exposed, but the spinal cord was not injured, and no implantation was given.MAIN OUTCOME MEASURES: Pathological changes were detected using hematoxylin-eosin staining; NF- K B expression was quantified using immunohistochemical staining; motor function was assessed using the Basso, Beattie and Bresnahan (BBB) scale.RESULTS: Spinal cord injuries, such as neuronal death and inflammatory cell infiltration, were found in the microencapsulated cell group, the non-encapsulated cell group and the saline group.However, the damage in the microencapsulated cell group was milder than in the non-encapsulated cell or saline groups. NF- K B expression in the microencapsulated cell group,the non-encapsulated cell group and the saline group was increased after spinal cord injury; it reached a peak after 24 hours, gradually decreased after 3 days, and was close to normal levels after 7 days. NF- k B expression in the microencapsulated cell group was significantly lower than in the saline group and the non-encapsulated cell group (P < 0.05). With time, the motor function of the animals in each group improved to a certain extent, but did not reach normal levels. There were no significant differences in BBB scores between the different groups on post-operative day 3; however, the BBB scores for the microencapsulated cell group and the non-encapsulated cell group were significantly higher than the saline group on post-operative day 7 (P < 0.05). In addition, the motor function recovered better in the microencapsulated cell group than in the non-encapsulated cell group (P < 0.05).CONCLUSION: The transplantation of microencapsulated rabbit sciatic nerve can inhibit NF- k B expression and inflammatory reactions and promote recovery of motor function after spinal cord injury in rats. The effects of microencapsulated cell transplantation are superior to those of transplantation of cells alone.