Wilting J, Papoutsi M, Othman-Hassan K, Rodriguez-Niedenführ M, Pröls F, Tomarev S I, Eichmann A
Anatomisches Institut der Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.
Microsc Res Tech. 2001 Oct 15;55(2):81-91. doi: 10.1002/jemt.1159.
Recently, highly specific markers of the lymphatic endothelium have been found enabling us to reinvestigate the embryonic origin of the lymphatics. Here we present a review of our studies on the development of the lymphatic system in chick and quail embryos. We show that the lymphatic endothelium is derived from two sources: the embryonic lymph sacs and mesenchymal lymphangioblasts. Proliferation studies reveal a BrdU-labeling index of 11.5% of lymph sac endothelial cells by day 6.25, which drops to 3.5% by day 7. Lymphangioblasts are able to integrate into the lining of lymph sacs. Lymphatic endothelial cells express the vascular endothelial growth factor (VEGF) receptors-2 and -3. Their ligand, VEGF-C, is expressed almost ubiquitously in embryonic and fetal tissues. Elevated expression levels are found in the tunica media of large blood vessels, which usually serve as major routes for growing lymphatics. The homeobox gene, Prox1, is expressed in lymphatic but not in blood vascular endothelial cells throughout all stages examined, namely, in developing lymph sacs of day 6 embryos and in lymphatics at day 16. Experimental studies show the existence of lymphangioblasts in the mesoderm, a considerable time before the development of the lymph sacs. Lymphangioblasts migrate from the somites into the somatopleure and contribute to the lymphatics of the limbs. Our studies indicate that these lymphangioblasts already express Prox1.
最近，已发现淋巴管内皮的高度特异性标志物，这使我们能够重新研究淋巴管的胚胎起源。在此，我们对我们关于鸡和鹌鹑胚胎淋巴管系统发育的研究进行综述。我们发现淋巴管内皮来源于两个来源：胚胎淋巴囊和间充质淋巴管母细胞。增殖研究显示，到第6.25天时，淋巴囊内皮细胞的BrdU标记指数为11.5%，到第7天时降至3.5%。淋巴管母细胞能够整合到淋巴囊的内衬中。淋巴管内皮细胞表达血管内皮生长因子（VEGF）受体-2和-3。其配体VEGF-C在胚胎和胎儿组织中几乎普遍表达。在大血管的中膜中发现表达水平升高，大血管通常是生长中的淋巴管的主要路径。在所有检测阶段，同源盒基因Prox1在淋巴管内皮细胞中表达，而不在血管内皮细胞中表达，即在第6天胚胎发育中的淋巴囊中以及第16天的淋巴管中表达。实验研究表明，在淋巴囊发育前相当长的一段时间，中胚层中就存在淋巴管母细胞。淋巴管母细胞从体节迁移到体壁，并参与四肢淋巴管的形成。我们的研究表明，这些淋巴管母细胞已经表达Prox1。
