不同强度减重步行训练对脊髓损伤模型大鼠脊髓组织中TrkB和BDNF蛋白表达水平的影响及其对运动功能恢复的促进作用

目的：观察减重步行训练（BWSTT）对脊髓损伤（SCI）大鼠脊髓组织中受体酪氨酸蛋白激酶B （TrkB）及脑源性神经营养因子（BDNF）蛋白表达水平和运动功能的影响，并探讨其可能的作用机制。方法：50只成年雄性SD大鼠随机分为假手术组、SCI组、BWSTT-A组（低强度训练）、BWSTT-B组（中强度训练）和BWSTT-C组（高强度训练），每组10只。应用自制的打击器制备SCI模型。假手术组大鼠仅行椎板切除术暴露硬脊膜，不予打击，直接缝合，术后不给予任何治疗；SCI组大鼠造模后不给予任何治疗；BWSTT组大鼠在SCI后给予康复锻炼，3组大鼠步行速度分别为7、15和21 cm·s^-1。在造模后35 d采用Basso、Beattie和Bresnahan （BBB）评分评定SCI大鼠后肢功能恢复情况，免疫蛋白印记法检测各组大鼠脊髓组织中TrkB和BDNF蛋白表达水平，尼氏染色法检测各组大鼠脊髓尼氏小体的形态和数量。结果：与SCI组比较，BWSTT-B组和BWSTT-C组大鼠BBB评分升高（P<0.01）；与BWSTT-A组比较，BWSTT-B组和BWSTT-C组大鼠BBB评分升高（P<0.01）。免疫蛋白印记法检测，与假手术组比较，SCI组大鼠脊髓组织中TrkB蛋白表达水平降低（P<0.01）；与SCI组比较，BWSTT-B组和BWSTT-C组大鼠脊髓组织中TrkB蛋白表达水平升高（P<0.01）；与假手术组比较，SCI组大鼠脊髓组织中BDNF蛋白表达水平降低（P<0.01）；与SCI组比较，BWSTT-B组和BWSTT-C组大鼠脊髓组织中BDNF蛋白表达水平均升高（P<0.01）。尼氏染色法检测，与SCI组比较，BWSTT组细胞尼氏小体数量较多，细胞形态较好。结论：中和高强度的BWSTT可在一定程度上促进SCI大鼠运动功能恢复，其机制可能与上调脊髓组织中TrkB和BDNF蛋白的表达有关。

Effects of body weight support treadmill training with different exercise intensities on expressions of TrkB and BDNF proteins in spinal cord tissue and its promotion effect on motor function recovery of rats with spinal cord injury

Objective: To observe the effects of body weight support treadmill training(BWSTT) with different exercise intensities on the expression levels of tyrosine protein kinase B (TrkB) and brains-derived neurotrophic factor (BDNF) proteins in spinal cord tissue and motor function of the spinal cord injury(SCI) rats, and to explore the possible mechanism. Methods: Fifty adult male SD rats were randomly divided into sham operation group, SCI group, BWSTT-A group(given low intersity exercise), BWSTT-B group (given middle intensity exercise)and BWSTT-C group (given high intersity exercise); there were ten rats in each group. the SCI model was prepared by using a self-made striker.The rats in sham operation group only underwent laminectomy to expose the dura mater and were sutured directly, and the rats didn't receive any treatment after surgery;the rats in SCI group weren't given any treatment after modeling;the rats in BWSTT groups were given rehabilitation exercise after SCI and the walking speeds of the rats in three groups were 7, 15, and 21 cm·s^-1, respectively.The recovery status of hind limb function of the rats in various groups was evaluated by Basso,Beattie,and Bresnahan(BBB) score 35 d after modeling;the expression levels of TrkB and BDNF proteins in spinal cord tissue of the rats in various groups were detected by Western blotting method,and the morphology and the number of Nissl bodies of the rats in various groups were analyzed by Nissl staining. Results: Compared with SCI group, the BBB scores of the rats in BWSTT-B and BWSTT-C groups were increased (P<0.01); compared with BWSTT-A group, the BBB scores of the rats in BWSTT-B and BWSTT-C groups were increased (P<0.01).Compared with sham operation group,the expression level of TrkB protein in spinal cord tissue of the rats in SCI group was decreased(P<0.01);compared with SCI group, the expression levels of TrkB protein in spinal cord tissue of the rats in BWSTT-B and BWSTT-C groups were increased (P<0.01). Compared with sham operation group, the expression level of BDNF protein in spinal cord tissue of the rats in SCI group were decreased(P<0.01); compared with SCI group, the expression levels of BDNF protein in spinal cord tissue of the rats in BWSTT-B group and BWSTT-C group were increased (P<0.01). The Nissl staining results showed that compared with SCI group, the number of Nissl cells in BWSTT groups was more and the morphology of cells was better. Conclusion: Middle and high intensities of BWSTT may promote the recovery of motor function of the SCI rats, and its mechanism may be related to up-regulation of the expressions of TrkB and BDNF proteins in spinal cord tissue.