运动训练对脊髓损伤大鼠脊髓内BDNF及其受体TrkB表达的影响

Effects of Exercise on Expressions of Brain-Derived Neurotrophic Factor and Tyrosine Kinase Receptor B in Injured Spinal Cord of Rats

目的：研究运动训练对脊髓损伤（SCI）大鼠脊髓内脑源性神经营养因子（BDNF）及其酪氨酸激酶受体B（TrkB）表达的影响。方法24只SD大鼠随机均分为假手术组、损伤对照组和运动训练组。采用通用型脊髓打击器建立T10 SCI大鼠模型。运动训练组于损伤后1周起对大鼠进行4周运动训练，假手术组和损伤对照组不进行运动训练。采用BBB评分观察损伤前及损伤后第1~5周大鼠后肢运动功能的变化。运动训练结束后取大鼠T12～L1节段脊髓，免疫组化结合图像平均光密度分析观察脊髓组织BDNF和TrkB的表达及分布，Western blot检测脊髓内BDNF和TrkB蛋白含量。结果损伤前，3组大鼠BBB评分为21.00分。损伤后，损伤对照组及运动训练组BBB评分均低于假手术组（均P＜0.05）。损伤3周后运动训练组BBB评分高于损伤对照组（P＜0.05）。BDNF、TrkB免疫反应阳性产物均多分布于脊髓前角、脊髓后角及中央管周围；运动训练组BDNF、TrkB阳性染色颗粒均增多，平均光密度值均高于假手术组和损伤对照组（均P＜0.05）。运动训练组大鼠脊髓内BDNF及TrkB的表达高于假手术组和损伤对照组。结论运动训练能诱导SCI大鼠脊髓内BDNF及其受体TrkB表达，促进其运动功能恢复。

Objective To investigate the effects of exercise on expressions of brain-derived neurotrophic factor （BDNF） and tyrosine kinase receptor B （TrkB） in spinal cord of spinal cord injury （SCI） rats. Methods Spinal cord injury models were produced by universal spinal cord impact system. Twenty-four Sprague-Dawley rats were randomly divided into 3 groups, exercise group （SCI-induction and exercises, n=8）, control group （SCI-induction without exercises,n=8） and sham-operation group （no operation, without SCI nor exercises, n=8）. Exercise training began from the 7th day after injury for 4 weeks. The locomotor function was assessed by Basso-Beattic-Bresnahan （BBB） scale before injury and at the 1st, 2nd, 3rd, 4th and 5th week post injury. The expressions level of BDNF and TrkB in spinal cords were detected by immunohistochemis-try and Western blot. Results Since the 3rd week after injury （after 2 weeks of exercise training）, BBB scores in exercise group were higher than that in control group （P 〈 0.05）. In immunohistochemistry test, positive immunologic reaction to BDNF protein was mainly located in anterior horn of spinal cord, and the expression level in exercise group was significantly higher than that in sham-operation group and control group （P〈0.05）. In immunohistochemistry test, positive immunologic reaction to TrkB protein was located in anterior horn and dorsal horn and central canal of spinal cord, and the expression lev-el in exercise group was significantly higher than that in sham-operation group and control group （P〈0.05）. Expression of BDNF and TrkB in exercise group rats after exercise for 4 weeks were significantly increased, compared with that in control group. Conclusion Exercise training may effectively induce BDNF and TrkB expression in spinal cords and promote the re-covery of locomotor function of SCI rats.