Effects of poly lactic-co-glycolic acid-Nogo A antibody delayed-release microspheres on regeneration of injured spinal cord in rats

BACKGROUND: Nogo A antigen is the major inhibiting factor blocking regeneration of the injured spinal cord. Neutralizing Nogo A antigens using Nogo A antibodies may help promote neurite regeneration and nervous function recovery. For successful regeneration, sustained release of the antibody from a biodegradable material loaded with Nogo A antibodies to the injury site is required. OBJECTIVE: To compare the therapeutic effects of poly lactic-co-glycolic acid (PLGA)-Nogo A antibody delayed-release microspheres and Nogo A antibody alone on spinal regeneration in Sprague-Dawley rats with complete transverse injury to the spinal cord. DESIGN, TIME AND SETTING: A randomized, controlled animal trial was performed at the Pharmacological Laboratory of West China Center of Medical Sciences, Sichuan University, between October 2007 and January 2008. MATERIALS: Goat anti-rat Nogo A monoclonal antibody was purchased from Santa, American; goat anti-rat neurofilament 200 monoclonal antibody was from Zhongshan Goldenbridge, Beijing, China; PLGA-Nogo A antibody delayed-release microspheres were provided by the College of Pharmacy, Sichuan University. METHODS: A total of 36 adult female Sprague Dawley rats were used to establish models of completely transected spinal cord injury, at T-10. Animals were randomly divided into three groups (n=12): model, Nogo A antibody alone, and Nogo A antibody delayed-release microsphere groups. After transverse injury of the spinal cord, 50 P L normal saline solution, 50 11 L normal saline solution containing 50 P g Nogo A antibody, and 50 mu L normal saline solution containing 50 mu g Nogo A antibody microspheres were administered to the respective groups at the injury site. MAIN OUTCOME MEASURES: The expression of Nogo A and neurofilament 200 in injured spinal cord was tested immunohistochemically, and motor function of rats was assessed by Basso-Beattie-Bresnahan (BBB) locomotor rating scale. RESULTS: Four weeks after injury, expression of Nogo A in microsphere group was significantly less than model and Nogo A antibody alone groups (P < 0.05); while there was no significant difference between model and Nogo A antibody alone groups (P > 0.05). Ten weeks after injury, microsphere group showed a significantly greater expression of neurofilament 200 than model and Nogo A antibody alone groups (P < 0.05); while no significant difference was found between model and Nogo A antibody alone groups (P > 0.05). At postoperative weeks 5 and 6, the score of BBB locomotor rating scale in microsphere group was significantly greater than the model group (P < 0.05), and at postoperative weeks 7-10, the score was much greater than model and Nogo A antibody alone groups (P < 0.05). CONCLUSION: Nogo A antibody delayed-release microspheres decreased Nogo A expression, increased neurofilament 200 expression in the injured spinal cord of rats, and promoted recovery of motor function through sustained drug release over a long-term period.