Yuan K, Lin M T
Periodontics Division, Department of Dentistry, National Cheng Kung University Hospital, Tainan, Taiwan.
Oral Dis. 2004 May;10(3):179-85. doi: 10.1046/j.1601-0825.2003.00997.x.
The molecular mechanism for the regression of pregnancy pyogenic granuloma after parturition remains unclear. It has been proposed that, in the absence of vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2) causes blood vessels to regress. Therefore, we investigated the roles of Ang-2 and VEGF in the regression of pregnancy pyogenic granuloma.
The effects of tumor necrosis factor-alpha (TNF-alpha) on the transcription of Ang-2 were tested in endothelial cells by reverse transcriptase-polymerase chain reaction. A total of 15 specimens, including granulomas taken from five gravidas during pregnancy, five after parturition, and five from normal gingiva were compared by immunoblot assays for their relative expressions of Ang-1, Ang-2, Tie-2, VEGF, and beta-actin. Double staining, immunohistochemistry for Ang-2, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling for apoptotic cells, were used to evaluate their regression. Finally, a fibrin gel culture system was used to investigate whether the withdrawal of VEGF and addition of Ang-2 could cause newly grown microvessels to regress.
TNF-alpha upregulated the expression of Ang-2 in all endothelial cell types tested. The protein levels of Ang-2 and Tie-2 were highest in the granulomas in pregnancy, followed by those after parturition and normal gingiva, while Ang-1 and beta-actin exhibited no significant differences. The amount of VEGF was high in the granulomas in pregnancy and almost undetectable after parturition. Double staining on granulomas after parturition revealed more apoptotic cells and less Ang-2 than did those in pregnancy. In the fibrin gel assay, VEGF alone or in combination with Ang-2 could protect microvessels from apoptosis, while Ang-2 alone had no effect.
Our findings suggest that a lack of VEGF is associated with apoptosis of endothelial cells and regression of granuloma. The roles of Ang-2 require additional study.
产后妊娠性化脓性肉芽肿消退的分子机制尚不清楚。有人提出，在缺乏血管内皮生长因子（VEGF）的情况下，血管生成素-2（Ang-2）会导致血管消退。因此，我们研究了Ang-2和VEGF在妊娠性化脓性肉芽肿消退中的作用。
通过逆转录聚合酶链反应检测肿瘤坏死因子-α（TNF-α）对内皮细胞中Ang-2转录的影响。通过免疫印迹分析比较了总共15个标本，包括取自5名孕妇孕期的肉芽肿、5名产后肉芽肿以及5名正常牙龈组织，检测它们Ang-1、Ang-2、Tie-2、VEGF和β-肌动蛋白的相对表达。采用双重染色、Ang-2免疫组化以及凋亡细胞的末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法来评估它们的消退情况。最后，使用纤维蛋白凝胶培养系统研究去除VEGF并添加Ang-2是否会导致新生长的微血管消退。
TNF-α上调了所有测试内皮细胞类型中Ang-2的表达。Ang-2和Tie-2的蛋白水平在孕期肉芽肿中最高，其次是产后肉芽肿和正常牙龈组织，而Ang-1和β-肌动蛋白无显著差异。孕期肉芽肿中VEGF含量较高，产后几乎检测不到。产后肉芽肿的双重染色显示，与孕期相比，凋亡细胞更多，Ang-2更少。在纤维蛋白凝胶试验中，单独的VEGF或与Ang-2联合使用可保护微血管免于凋亡，而单独的Ang-2则无作用。
我们的研究结果表明，VEGF缺乏与内皮细胞凋亡和肉芽肿消退有关。Ang-2的作用需要进一步研究。
