慢性全脑低灌注大鼠侧脑室旁白质改变及其与基质金属蛋白酶表达的关系

The correlation between periventricular white matter changes and matrix metalloproteinase-3 expression after chronic cerebral hypoperfusion in rats

目的观察慢性全脑低灌注大鼠模型侧脑室旁白质髓鞘改变及其与基质金属蛋白酶-3（MMP-3）表达的关系。方法Wistar雄性大鼠40只，随机分为假手术组和模型组（术后20d组、40d组、60d组），每组各10只，模型组行双侧颈总动脉永久结扎术（2VO）制备慢性全脑低灌注模型。选择侧脑室旁白质胼胝体和内囊为观察和检测部位，采用透射电镜观察假手术组及模型组侧脑室旁白质髓鞘改变，免疫印迹法检测髓鞘重要成分髓鞘碱性蛋白（MBP）的水平，免疫组织化学染色和免疫印迹法检测MMP3的表达。结果模型20d组侧脑室旁白质有髓纤维髓鞘发生变形、板层结构疏松、崩溃等脱髓鞘改变，血管旁水肿等，假手术组无明显改变。各模型组MBP（20d组54．5±4．1，40d组47．8±4．8，60d组36．5±4．2）随低灌注时间延长水平逐渐下降，较假手术组（65．0±7．7）差异均有明显统计学意义（F=29．07，P〈0．01）。各模型组MMP-3表达（20d组39．2±4．2，40d组43．3±3．5，60d组54．2±2．8）均较假手术组（26．7±3．8）增多（F=59．37，P〈0．01）。MMP-3表达变化与MBP水平改变呈明显负相关（r=-0．883，P％0．01）。结论大鼠慢性全脑低灌注引起持续性的侧脑室旁白质脱髓鞘改变，MMP-3表达上调可能参与其损伤机制。

[Abstract] Objective To observe periventricular white matter changes and matrix metalloproteinase-3 （MMP-3） expression after two vessel occlusion in rats. Methods A total of 40 Wistar rats were randomly divided into four groups： sham operation group, model group 1 （20 days after operation）, model group 2 （40 days after operation） , model group 3 （60 days after operation） （n = 10 per group）. Model of chronic cerebral hypoperfusion was induced by permanent ligation of the bilateral common carotid arteries in the rat. The change of periventricular white matter was observed by electron microscope. The myelin basic protein （MBP） levels was determined by Western blotting, and the expression of MMP-3 was analysed by immunohistochemical stain and Western blotting. Results Permanent ligation of the bilateral common carotid arteries resulted in demyelination in the corpus callosum and internal capsule in rats. The expressions of MMP-3 in model groups were markedly elevated compared with sham group （model group 1, 39.17 ±4. 167; model group 2, 43.33±3. 502; model group 3, 54. 16±2. 787; sham group, 26.67±3. 830; all P〈0.01）. The content of MBP in model groups was gradually decreased compared with sham group （model group 1, 54.50±4. 087; model group 2, 47.83±4. 875; model group 3, 36.50±_4. 231; sham group, 65.01±7. 688; all P〈0. 01）. Additionally, the upregulation of MMP 3 had significant correlation with the loss of MBP in the periventricular white matter （r= --0. 883,P〈0. 01）. Conclusions Chronic cerebral hypoperfusion induces progressive periventricular white matter demyelination, and the upregulation of MMP-3 may involve in the pathological process.