脑缺血再灌注后少突胶质细胞转录因子Olig1、轴突生长抑制因子Nogo—A基因表达与白质损伤

Expressions of Oligl and Nogo-A genes related to white matter injury after cerebral ischemiareperfusion

目的检测少突胶质细胞转录因子Oligl、轴突生长抑制因子Nogo—A在大鼠脑缺血再灌注后不同时间点基因表达的变化规律，观察白质损伤的病理变化，探讨两者之间的关系。方法利用线栓法制备大鼠大脑中动脉缺血（middle cerebral artery occlusion，MCAO）再灌注模型，实时定量PCR方法（relative quantification PCR，RQ—PCR）检测各时问点Oligl、Nogo—A在大脑损伤白质区的基因表达，髓鞘快蓝-高碘酸雪夫（LFB—PAS）染色法标记大脑神经髓鞘，Bielschowsky银染法标记大脑神经轴突，并计算缺血侧与健侧髓鞘染色的积分吸光度（IAs）比值以代表白质受损程度。结果（1）Olig1：Olig1在缺血再灌注不同时间点，在大脑白质区的基因表达量不同。缺血再灌注6h Oligl表达量减低至假手术组的83％（与假手术组相比，q=2．074，P=0．042），7d时表达量降至最低，14d时恢复至基础水平，21d时表达量升高至假手术组的1．52倍（与假手术组相比，q=6．362，P〈0．01，差异具有统计学意义）。Nogo—A：Nogo-A在缺血再灌注不同时间点，在大脑白质区的基因表达量不同。Nogo-A基因表达在缺血再灌注1d时开始减低，表达量降至假手术组的84％（与假手术组相比，q=2．230，P=0．029），7d时降至最低，14～21d表达量开始上调，21d时表达量上调至假手术组的66％（与假手术组相比，q=4．681，P〈0．01）。（2）缺血再灌注不同时间点髓鞘染色／As比值不同，再灌注6h时开始下降（0．91±0．05），与假手术组（1．03±0．09）相比，q=3．829，P〈0．01；12h时有空洞形成，再灌注14d髓鞘损伤达到高峰，IAs比值降到最低（0．31±0．07），髓鞘脱失明显；21d的髓鞘IAs比值（0．30±0．06）与14d（O．31±0．07）相比较差异无统计学意义（g=0．257，P=0．798）。轴突变化规律与髓鞘基本相同。结论Oligl、Nogo—A在脑缺血再灌注损伤过程中呈现动态变化规律，并与白质损伤的变化规律基本相同，提示Oligl、Nogo-A可能参与了再灌注损伤的病理生理过程，并与缺血再灌注白质损伤及修复密切相关。

Objective To investigate expressions of oligodendrocyte transcription factor 1 （ Oligl ） and neurite outgrowth inhibitor-A （Nogo-A） and white matter injury after focal cerebral ischemia in rats, and explore their relationship. Methods Sprague-Dawley male rats were subjected to middle cerebral artery occlusion for 2 hours. RQ-PCR was performed to examine the expression of Oligl and Nogo-A in white matter at different reperfusion time points in both testing group and shame-operation control group. Myelin sheath was stained by LFB-PAS protocol, and axon was stained by Bielschowsky＇ s silver stain. Integrated optical densities （IAs） in LFB-PAS staining in both hemispheres were measured, and the IAs ratio was calculated to represent the severity of the white matter damage. Results （ 1 ） The expreesion of Oligl and Nogo-A ： F =29. 556 and 22. 816 respectively. In the testing group, the expression levels of Oligl and Nogo-A in the white matter began to decrease 6 h and 1 d post-reperfusion, respectively, to 83% and 84% of the levels in sham-operation group （ q = 2. 074, P = 0. 042 and q = 2. 230, P = 0. 029 respectively） , and both reached their lowest level at 7 d. They increased afterwards. At 14 d, Olig-1 reached the base level similar to the sham-operation group （q =0. 625,P =0. 534）. At 21 d, Olig-1 and Nogo-A increased to 1.52 times and 66%, respectively, of those in sham-operation group （ q = 6. 362, P 〈 0. 01 and q = 4. 681, P 〈 0. 01 respectively）. （2）LFB-PAS staining： F = 122. 181 ,myelin sheaths lost their LFB-PAS staining and IAs ratio decreased at 6 h after ischemia-reperfusion （0. 91 ± 0. 05, q = 3. 829, P 〈 0. 01 vs sham-operation group）. Vacuoles appeared separating myelin sheaths at 12 h. The IAs ratio decreased gradually and reached its lowest point at 14 d （0. 31 ±0. 07）. There was no significant difference in IAs ratio between 14 and 21 d （ q = 0. 257, P = 0. 798）. The change in axons was similar to that in Myehn sheaths. Conclusions The Oligl and Nogo-A expression show biphasic change in time-lapse study and the changes by time are in accordance with the pattern in pathologic findings in the white matter by LFB and Bielschowsky ＇ s silver staining. Oligl and Nogo-A might participate in the pathogenesis of cerebral white matter lesion and plasticity.