Yasuda Y, Nishi N, Takahashi J A, Konishi H, Ohara I, Fujita H, Ohta M, Itoh N, Hatanaka M, Tanimura T
Department of Anatomy (1st Division), Kinki University School of Medicine, Osaka, Japan.
Dev Biol. 1992 Apr;150(2):397-413. doi: 10.1016/0012-1606(92)90251-b.
Vasculogenesis depends on autocrine secretion of basic fibroblast growth factor (bFGF) from capillary endothelial cells. Retinoic acid (RA) induced avascular yolk sac (AVY) of mouse embryos of dams given 60 mg/kg of RA orally on Day 8 of gestation and sacrificed 3 days later. We studied the localization and transcriptional expression of bFGF and FGF-receptor (flg), heparin-binding growth factor (HBGF) activity, localization of lysosomal enzymes and alpha 1-antitrypsin (AAT), and electron microscopy of the normal mouse visceral yolk sac (VYS) and AVY. bFGF, which is normally present in the endoderm of the VYS of 8-day-old embryos and in all components of the VYS by Day 11 of gestation, was reduced in the AVY. However, in the presence of bFGF in vitro capillary nets were restored in the AVY. The mRNA for bFGF was not detectable in either VYS or AVY, while flg mRNA was detected equally in both organs in Northern blotting. The characteristic distribution pattern of lysosomal enzymes, acid phosphatase, lysozyme, and cathepsin D, and AAT was altered in the AVY. The level of acid phosphatase and AAT was reduced to 10% in the AVY. Electron microscopy revealed a partial or total loss of lysosomal membranes where the contents of lysosomes fused with adjacent lysosomes and the external organelles. These results suggest that vitelline blood vessels are not developed by endogenous autocrine bFGF but by exogenous transcellular bFGF from absorptive endodermal cells. Retinoic acid does not affect the angiogenic capacity of the VYS mesenchyme but destroys lysosomes, which release hydrolytic enzymes, leading to degradation of AAT in the endodermal cells and then digestion of endocytosed bFGF.
血管生成依赖于毛细血管内皮细胞自分泌碱性成纤维细胞生长因子（bFGF）。在妊娠第8天给母鼠口服60mg/kg视黄酸（RA），3天后处死，其胚胎出现无血管卵黄囊（AVY）。我们研究了bFGF和FGF受体（flg）的定位及转录表达、肝素结合生长因子（HBGF）活性、溶酶体酶和α1 -抗胰蛋白酶（AAT）的定位，以及正常小鼠内脏卵黄囊（VYS）和AVY的电子显微镜观察。正常情况下，8日龄胚胎VYS的内胚层中存在bFGF，到妊娠第11天时VYS的所有成分中都有bFGF，但在AVY中bFGF减少。然而，体外加入bFGF后，AVY中可恢复毛细血管网。在VYS和AVY中均未检测到bFGF的mRNA，而在Northern印迹法中，flg mRNA在两个器官中均能等量检测到。AVY中溶酶体酶、酸性磷酸酶、溶菌酶和组织蛋白酶D以及AAT的特征性分布模式发生了改变。AVY中酸性磷酸酶和AAT的水平降至10%。电子显微镜显示溶酶体膜部分或完全丧失，溶酶体内容物与相邻溶酶体及外部细胞器融合。这些结果表明，卵黄血管不是由内源性自分泌bFGF发育而来，而是由吸收性内胚层细胞产生的外源性跨细胞bFGF发育而来。视黄酸不影响VYS间充质的血管生成能力，但会破坏溶酶体，释放水解酶，导致内胚层细胞中AAT降解，进而消化内吞的bFGF。
