大鼠血视神经屏障特性的观察

目的研究大鼠视神经血视神经屏障与血脑屏障微血管内皮细胞在超微结构、标记物表达及通透性方面的差异。方法SD雄性大鼠20只,分别取筛板前区、筛板区、筛板后区、眶内段、管内段、颅内段和前额叶皮层。10只用电镜观察各部位微血管内皮细胞的超微结构;10只用免疫组织化学的方法检测内皮屏障抗原（EBA）的表达及微血管周围纤维蛋白原外渗情况。结果电镜显示视神经各段和前额叶皮层微血管内皮细胞均为紧密连接,以30000倍拍摄微血管内皮细胞。将5mm透明方格网重叠于照片上,随机数3个方格质膜囊泡数,最终折算成每μm^2内膜内质膜囊泡的数量。筛板前区内皮细胞质膜囊泡为（108．0±12．0）个,多于前额叶皮层质膜囊泡（31．8±2．9）个],差异有统计学意义（P〈0．05）;而筛板区内皮细胞质膜囊泡（30．4±2．8）个、筛板后区（30．3±3．0）个、眶内段（31．3±3．8）个、管内段（28．9±2．0）个和颅内段（30．1±2．1）个与前额叶皮层比较差异均无统计学意义（均P〉O．05）。免疫组织化学显示筛板前区微血管内皮细胞EBA表达阴性。微血管周围纤维蛋白原阳性;而筛板区、筛板后区、眶内段、管内段、颅内段和前额叶皮层EBA阳性表达。微血管周围纤维蛋白原阴性。结论视神经筛板前区微血管内皮细胞在超微结构、标记物表达及通透性方面与前额叶皮层存在差异,因而不具有血脑屏障特性,而筛板区、筛板后区、眶内段、管内段和颅内段与前额叶皮层存在相似的特性,故具有血脑屏障特性。

Characteristics of blood-optic nerve barrier: experiment with rats

OBJECTIVE: To investigate the difference of endothelial cells in ultrastructure, marker expression, and permeability between blood-brain barrier and blood-optic nerve barrier. METHODS: The optic nerve, including the prelaminar region, lamina cribrosa, retro-laminar region, intraorbital portion, intracanalicular portion, and intracranial portion, and frontal cortex of 20 male SD rats were obtained to undergo electron microscopy and immunohistochemistry was used to detect the expression of endothelial barrier antigen (EBA) and the extravasation of fibrinogen around the microvessels. RESULTS: Electron microscopy showed tight junction among the endothelial cells in the microvessels of all portions of optic nerve and cerebral cortex. The number of plasmalemmal vesicles of the prelaminar region was (108.0 +/- 12.0)/microm2, significantly greater than that of the cerebral cortex (31.8 +/- 2.9)/microm2, P < 0.05]. However, there was no significantly difference in the number of plasmalemmal vesicle among the other portion of optic nerve and cerebral cortex (all P > 0.05). Immunohistochemistry showed that EBA was negative in the endothelial cells in the microvessels of prelaminar region, but strongly positive in the microvessels in the other portions of the optic nerve and in the cerebral cortex. Fibrinogen was present around the microvessels in the prelaminar region of optic nerve in a small amount, however, not present in the other portions of optic nerve and cerebral cortex. CONCLUSION: There is significant differences in the number of plasmalemmal vesicle, EBA expression, and permeability between the prelaminar region of optic nerve and cerebral cortex, which demonstrates that this region lacks the characteristics of typical blood-brain barrier. However, the other parts of optic nerve possess the properties of classical blood-brain barrier.