BACKGROUND: Changes of brain-derived neurotrophic factor (BDNF) expression reflect function of nerve cells; meanwhile, they play a significant role in researching interventions on plerosis of nerve injury.OBJECTIVE: To observe and compare the effects on changes of BDNF expression in rats with spinal cord injury between microencapsulated sciatic nerve cells of rabbits and only transplanting sciatic nerve cells of rabbits.DESIGN: Randomized controlled animal study.SETTING: Medical School of Jiujiang College.MATERIALS: The experiment was carried out in the Medical Science Researching Center, Jiujiang College from May 2004 to May 2006. A total of 90 healthy adult SD rats, weighing 250 - 300 g, of either gender; and 10 rabbits, weighing 2.0 - 2.5 kg, of either gender, were provided by Jiangxi Experimental Animal Center.METHODS: Sciatic nerve tissue of rabbits was separated to make cell suspension. After centrifugation,suspension was mixed with 15 g/L alginate saline solution and ejaculated to 20 mmol/L barium chloride saline solution by double-cavity ejaculator. The obtained cell microcapsules were suspended in saline. Rats were randomly divided into microencapsulated group, only suspension group, and only injured group with 30 animals in each group. After anesthesia, T10 spinous process and vertebra lamina of rats in the former two groups were exposed. Spinal cord tissue in 2-mm length was removed from rats by spinal cord right hemi-section. The gelatin sponges with the size of 2 mm × 2 mm × 2 mm were grafted as filing cage,and absorbed 10 μμ L microencapsulated sciatic nerve cells of rabbit in the microencapsulated group and 10 μ L sciatic nerve cells of rabbits in the only suspension group; respectively. No graft was placed in the only injured group.MAIN OUTCOME MEASURES: On the 1st, 3rd, 7th, 14th and 28th days after operation,immunohistochemistry (SABC technique) was used to detect distribution and amount of positive-reactive neurons in BDNF of spinal cord samples which were selected as 2 cm away from the injured surface.RESULTS: All the 90 rats were involved in the final analysis. Masses of brown-yellow particles were found in the microencapsulated group, and most of them were distributed in the spinal cord anterior horn neurons and glial cells. The positive-reactive neuron particles were also found in the white matter and gray matter. On the 3rd, 7th, 14th and 28th days after operation, amount of positive-reactive neurons in BDNF in the microencapsulated group was higher than that in the only injured group (P ＜ 0.01) and only suspension group (P ＜ 0.05).CONCLUSION: After transplanting microencapsulated nerve cell suspension into injured spinal cord of rats,distribution and amount of positive-reactive neurons in BDNF of local samples at injured surface are increased remarkably as compared with those by using tissue cell transplantation.