| [Objective]To study the intervention effect of methylprednisolone (MP) and IN-1(Nogo-A monoclonal antibody)alone and combination therapy respectively on Nogo-A and GAP-43expression in rats after acute spinal cord injury,to investigate the efficacy and possible mechanisms of MP and IN-1alone and combined treatment of acute spinal cord injury.[Methods]The model of moderate spinal cord injury in rats was established by Allen method. Rats were divided randomly into4groups:group A (spinal cord injury group), group B (MP treated group after ASCI), group C (IN-1treated group after ASCI), group D (MP combined with IN-1treated group after ASCI). Group B received injection of MP with a dosage of30mg/kg and received in fusion of MP with a dose of5.4mg/kg/h for the following23h; Group C placed PE-10catheter in the subarachnoid space and received IN-1through PE-10catheter with a dose of25μ1/d for consecutive7days; Group D received injection of MP with a dosage of30mg/kg and received in fusion of MP with a dose of5.4mg/kg/h for the following23h; and received IN-1through PE-10catheter with a dose of25μ1/d for consecutive7days; Group A received normal saline daily instead of MP with the same method. At day1,3,7,14and21post-operation, the nerve function of rats were observed and evaluated by BBB score in each group and the morphology of injured spinal cord was observed by HE staining. The expression and distribution of Nogo-A and GAP-43protein were detected by immunohistochemistry staining and observed under microscope. The expression of Nogo-A protein was detected by Western blot at each study time point.[Results] 1. BBB score:The BBB score of group B, C and D was higher than that of group A, and showed statistically significant changes at day7,14and21(P<0.05) The BBB score of group B and group C was lower than that of group D, and showed statistically significant changes at day7,14and21(P<0.05); while the differences of the BBB score between groups B and group C were not statistically significant (P>0.05).2. HE staining:Organization and cell edema were the most significant in group A at the early stage after ASCI in HE staining, and scar tissue was formed later. Group B and group C had less structure damage, while group D has lightest structure changes.3. Immunohistochemistry:The positive expression of Nogo-A and GAP-43protein detected by immunohistochemistry were shown in all groups at different time points after SCI. Which the expression of Nogo-A increased after injury Id and reached a peak at day7and then decreased; The expression of Nogo-A in group B, C and D was lower than that in group A, the difference was statistically significant at day1,3,7and14(P<0.05); The expression of Nogo-A in group D was lower than that in group B and group C, the difference was statistically significant at day1,3,7and14(P<0.05); while The expression of Nogo-A in group C was lower than that in group B, the difference was statistically significant at day1,3and7(P<0.05). the expression of GAP-43increased after injury Id and reached a peak at day7and then decreased; The expression of GAP-43in group B, C and D was higher than that in group A, the difference was statistically significant at day3,7and14(P<0.05); The expression of GAP-43in group D was higher than that in group B and group C, the difference was statistically significant at day7and14(P<0.05); while the differences of the expression of GAP-43in groups B and group C were not statistically significant (P>0.05).4. Western Blot:The expression of Nogo-A consistent with the trend of immunohistochemistry results, the expression of Nogo-A increased after injury1d and reached a peak at day7and then decreased; The expression of Nogo-A in group B, C and D was lower than that in group A, the difference was statistically significant at day1,3,7and14(P<0.05); The expression of Nogo-A in group D was lower than that in group B and group C, the difference was statistically significant at day1,3,7and14(P<0.05); while The expression of Nogo-A in group C was lower than that in group B, the difference was statistically significant at day1,3,7and14(P<0.05).[Conclusions]1. The expression of Nogo-A and GAP-43were significantly increased after acute spinal cord injury. The expression of Nogo-A began to increase at day1and reached a peak at day7and then decreased; the expression of GAP-43began to increase at day1and reached a peak at day7and then decreased.2. The expression of Nogo-A in the combination group were lower than that of IN-1group, the MP group and the control group; The expression of GAP-43in the combination group were higher than that of IN-1group, the MP group and the control group; and The BBB score of the combined group was the highest.3. In the treatment of acute spinal cord injury with IN-1and MP showed a synergistic effect, the mechanism may be as follows:(1) synergistic inhibition of Nogo-A expression in the acute phase;(2) in the subacute phase, synergistic strengthen the GAP-43protein neurons et synthesis protein and improve the micro-environment and promote axonal regeneration;(3) reduce the secondary injury, reduce scar formation and promote the recovery of spinal cord function;(4) GAP-43antagonistic Nogo-A, weakening the Nogo-A inhibition of axonal regeneration. |
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