C6脑胶质瘤血-瘤屏障通透性与超微结构研究

An experimental study on the mechanism of altered endothelial permeability and its relantionship with the ultrastructure of microvessle in C6 glioma in vivo

目的观察C6脑胶质瘤血-瘤屏障(BTB)通透性及超微结构,探讨BTB通透性增高的主要途径。方法建立SD大鼠C6脑胶质瘤模型,以肿瘤中心、肿瘤边缘、邻近肿瘤脑组织(BAT)、远隔肿瘤脑组织(BDT)和正常脑组织(NBT)为研究点,经免疫组织化学半定量分析内源性白蛋白血管外渗,外源性硝酸镧(La3+)和辣根过氧化物酶(HRP)示踪电镜观察脑血管内皮细胞(BMECs)紧密连接(TJs)和胞饮的改变。结果C6胶质瘤间质呈中-强度白蛋白阳性反应,BAT弱阳性,BDT与NBT阴性(P<0.05);光镜示肿瘤区HRP在血管腔及管壁周围弥散分布,而非肿瘤区限于血管腔;电镜示肿瘤区La3+/HRP通过TJs渗至脑间质裂隙内,BAT有La3+/HRP渗至局部基膜(BM),而NBT/BDT完全封闭于管腔内;BM呈线状连续型,管腔内无瘤细胞;肿瘤BMECs胞质内吞饮囊泡数显著高于非肿瘤组(P<0.05),但两者均几乎无充填HRP的囊泡(P>0.05)。结论TJs开放是C6胶质瘤BTB通透性增高的结构基础和主要原因,胞饮作用甚微;C6胶质瘤诱导的屏障功能破坏随至肿瘤距离的增加而减弱;胶质瘤细胞仍具有部分诱导形成BBB的能力。

Objective To investigate the changes of permeability and tdtrastructure of bloodtumor barrier （BTB） in C6 glioma and verify the mechanisms of enhanced BTB permeability. Methods In male SD rats, the brain-beating C6 glioma models were established. The tumor core, tumor periphery region,brain around tumor （ BAT）, brain distant to tumor （BDT） and normal brain tissue （NBT） were studied. The extravasation of endogenous albumin was tested by immunohistochemistry. The uhrastructures of BBB/BTB were observed by lanthanum nitrate-tracing and horseradish peroxidase （HRP）-tracing transmission electronic microscope （EM）. Results （ 1 ） Moderate and intensive albumin positive staining appeared in the interstitial spaces of C6 glioma. However,the albumin staining was weak and negtive in BAT and NBT, respectively. （2） Under a light microscope, HRP was restricted in the capillary lumen in non-tumorous tissues, while HRP was located both in the lumen and along the outer wall of capillary in C6 glioma. （3） Under EM, La3 ＋/HRP was excluded from tight junctions （TJs） in non-tumorous tissues. Occasionally, extravasation to basement membrane （BM） was seen in certain sites of the capillaries in BAT. But La3 ＋/HRP penetrated TJs and seeped in BM and interstitial spaces in glioma. There was a significant increase in the number of vesicles in cytoplasm of tumor capillaries endothelial cells as compared with non- tumorous tissues （ P 〈 0.05 ）. However, very few HRP-filled vesicles were seen in both of them （ P 〉 0.05 ）. The BM of microvessels in glioma was continued, compact and lineal. No glioma cells were found in the blood vessels. Conclusion Opened TJs provide the main route of transport of different-sized molecular substances through endothelial wall. The disruptions of BBB in C6 glioma are decreased quickly with the increased distance to the solid tumor. The glioma cells show some atypia ,however they still remain part of ability to induce the formation of BBB.