The role of vascular nets in intestinal villi formation.

对小鼠肠道绒毛的初步形成与血管网络的发育进行了研究。妊娠12天和13天，小肠及其上皮细胞形成圆柱状管状结构，间充质内形成疏松的血管丛。在14天的小肠内，疏松的神经丛内形成致密的小血管丛，其分支位于上皮之下。这些上皮细胞开始在树枝之间长出长出的东西。管腔的延伸已经穿透了内生的上皮组织，使其基本简化。大约一半的上皮细胞和间充质细胞掺入BrdU进行2小时标记。标记细胞在内生体的上皮和邻近的间充质中明显。妊娠15天，胎盘内长入，大量上皮细胞被BrDU标记，内生细胞间凹陷加深，形成初始绒毛。毛细血管分支形成环状，一直延伸到绒毛顶端。随着发育的进行，绒毛延长，毛细血管环也延长。毛细血管环的顶部始终保持在绒毛顶部的位置。在妊娠14天前服用甲氨蝶呤经常干扰VIII的形成。妊娠15天后，甲氨蝶呤对绒毛密度影响不大。这些结果表明，胎鼠肠道绒毛的初始形成是由上皮的内生完成的，在绒毛形成之前抑制细胞增殖干扰了它。发育中的血管网在绒毛形成过程中起一定作用。

The initial formation of intestinal villi in the mouse was investigated in association with the development of vascular networks. On 12 and 13 days of gestation, the small intestine and its epithelium formed cylindrical tube and a loose plexus of vessels was builded in the mesenchyme. In the small intestine of 14 days of gestations, a dense plexus of smaller vessels was formed inside of the loose plexus and some branches from the former were placed beneath the epithelium. The epithelium began to make an ingrowth between the branches. An extension of the lumen had penetrated in the epithelium of the ingrowth to make it mostly simplified. Approximately half of the epithelial and mesenchymal cell incorporated BrdU for 2hr labelling. The labelled cell was prominent in the epithelium of the ingrowth and in the mesenchyme adjoining it. On 15 days of gestation, the ingrowth proceeded and lots of its epithelial cells were labelled with BrdU.The concavity between ingrowths deepened and formed an initial villus. The capillary branch formed a loop and extended into the villus as far as the top of the villus. As the development proceeded, the villus elongated and the capillary loop also extended. The top of the capillary loop always kept it position of the top of the villus. Administration of methotrexate before 14 days of gestation frequently disturbed the viii formation. After 15 days of gestation, the density of the villus was rarely affected by methotrexate administration. These results suggest that the initial formation of intestinal villi in the fetal mouse is performed by the ingrowth of the epithelium and that inhibition of cell proliferation before the villi formation disturbs it. The developing vascular nets would play some roles during the villi formation.