MEK抑制剂对脊髓损伤后胶质瘢痕形成的影响

Effect of MEK inhibitors on glial scar formation after acute spinal cord injury

中文关键词:  脊髓损伤  MEK抑制剂  胶质瘢痕  神经胶质原纤维酸性蛋白  波形蛋白

英文关键词:Spinal cord injury  Inhibitors of mitogen-activated ERK-regulating kinase  Glial scar formation  Glial fibrillary acidic protein  Vimentin

中文摘要:

  【摘要】 目的：观察MEK（mitogen-activated ERK-regulating kinase，丝裂原活化的细胞外信号调节激酶之调节激酶）抑制剂对脊髓损伤后胶质瘢痕形成的影响，并探讨胶质瘢痕形成的机制。方法：36只SD大鼠随机分为3组。Ⅰ组为假手术组，只打开椎板，不打击脊髓；Ⅱ组及Ⅲ组分别为脊髓损伤组及脊髓损伤后干预组，均造成T12脊髓损伤，Ⅲ组每天给予腹腔注射MEK抑制剂（U0126）共9d，其余组给予腹腔注射等量的二甲基亚砜（DMSO）。在术后当天、1d、3d、5d、7d、14d、21d、28d时对每组大鼠行BBB评分；术前及术后当天、14d及28d时对大鼠行体感诱发电位检测；术后14d及28d时分别处死大鼠，灌注固定，取原打击处脊髓标本行HE染色、神经胶质原纤维酸性蛋白（GFAP）及波形蛋白（Vim）免疫组化染色并光镜下进行观察，计算阳性细胞数。结果：Ⅰ组各时间点BBB评分及其他指标均无明显变化。脊髓损伤后，Ⅱ组及Ⅲ组大鼠双后肢运动功能均表现出不同程度的恢复，术后28d时Ⅱ组BBB评分为12.00±1.70分，Ⅲ组为16.5±1.08分，Ⅲ组恢复速度较Ⅱ组更快（P<0.05）。脊髓损伤后，大鼠双后肢感觉诱发电位潜伏期明显延长，波幅明显降低；术后观察，Ⅲ组潜伏期及波幅恢复较Ⅱ组明显增快（P<0.05），Ⅲ组在28d时可达到潜伏期16.86±0.55ms、波幅4.19±0.11μV。脊髓损伤后，HE染色可看到胶质细胞明显增多，胶质瘢痕形成，28d时Ⅲ组较Ⅱ组瘢痕范围小；损伤后星形胶质细胞明显活化增殖，GFAP及Vim的镜下表达数量明显增多。Ⅱ组、Ⅲ组损伤后14d时GFAP的表达分别为143.56±1.09和133.56±3.31，Vim的表达分别为93.82±4.48和89.32±6.50；28d时两组的GFAP表达分别为110.68±9.41和102.44±6.93，Vim的表达分别为72.96±4.16和66.44±4.46，干预后明显下调了GFAP及Vim的表达（P<0.05）。结论：MEK抑制剂能通过抑制星形胶质细胞的增殖，下调GFAP及Vim的表达，减少胶质瘢痕形成；同时可促进脊髓损伤后大鼠双后肢行为学及神经功能的恢复。

英文摘要:

  【Abstract】 Objectives: To investigate the influence and mechanism of the MEK inhibitors on glial scar formation after acute spinal cord injury in a rat model. Methods: Thirty-six adult female Sprague-Dawley rats were divided randomly into sham injury group(group I), SCI group(group Ⅱ), and U0126 treatment group(group Ⅲ). SCI lesions in group II and III were made by modified Allen′s impact device; while the sham injury group only accepted the pseudo-operation. Locomotor capacity was assessed based on the 21-point Basso, Beattie and Bresnahan score at 1d, 3d, 5d, 7d, 14d, 21d and 28d after injury. Somatosensory evoked potentials were used to assess neurologic recovery. While the lesions were obtained and studied by conventional histology, GFAP and Vim immunohistochemistry(HIC) by using light microscopy at 14d and 28d after injury. The rats were sacrificed at 14 and 28 days after SCI, perfusion fixed. Results: There was no obvious changes in BBB score and other index in group Ⅰ. After SCI, hind limbs motor function in group Ⅱ and group Ⅲ showed varied degrees of recovery, after 28 days, the BBB score in group Ⅱ was 12.00±1.70, and it was 16.5±1.08 in group Ⅲ, group Ⅲ improved more remarkably than group Ⅱ(P<0.05). Somatosensory evoked potentials prolonged after SCI, while the amplitude decreased significantly; the latency and amplitude in group Ⅲ increased significantly than group Ⅱ(P<0.05), the incubation period in group Ⅲ at 28 days was 16.86±0.55ms, and the amplitude was 4.19±0.11μV. HE staining showed glial cells increased after SCI, glial scar formed obviously at 28 days. Compared with group Ⅱ, the scar volume in group Ⅲ was smaller; astrocytes activation and proliferation of GFAP expression significantly increased in group Ⅱ and group Ⅲ. At 14 days, the GFAP expression in two groups was 143.56±1.09 and 133.56±3.31 respectively; Vim expression of the two groups was 110.68±9.41 and 102.44±6.93 respectively. At 28 days, the GFAP and Vim of the two groups were 110.68±9.41, 102.44±6.93 and 72.96±4.16, 66.44±4.46 respectively. The expressions of GFAP and Vim significantly decreased after intervention of U0126(P<0.05). Conclusions: MEK inhibitors can inhibit star glial cell proliferation as well as the expression of GFAP and Vim, which can decrease glial scar formation, and then improve the hindlimb motor function.