Kimber S J
School of Biological Sciences, University of Manchester, 3.239 Stopford Building, Oxford Road, Manchester, M13 9PT, UK.
Semin Reprod Med. 2000;18(3):237-53. doi: 10.1055/s-2000-12562.
In mammals the embryo must implant in the uterus and develop a placenta to gain nutrition and facilitate gas exchange. In this article, the earliest events in this process are reviewed. The embryo can implant only when it has reached the blastocyst stage. The blastocyst is composed of an inner clump of cells, the inner cell mass, that gives rise to the fetus and an outer layer of trophectoderm (TE), the precursor of the placenta. Both blastocyst and uterus must differentiate in parallel to reach the appropriate state of maturity (activated blastocyst and receptive uterus) at which implantation can occur. Interaction between TE and the luminal epithelium (LE) lining the uterus initiates implantation, and both soluble signals and association between molecules on apposed surfaces appear to be involved. A number of cell surface molecules have been implicated in the initial attachment between TE and LE. These include HSPG, Le-y and the H-type-1 antigen, HB-EGF, trophinin-tastin-bystin complex, integrins, and extracellular matrix molecules such as osteopontin and laminin. Others, such as mucins, may need to be removed or modified to allow adhesion to proceed. Evidence for the role of these components is discussed.
在哺乳动物中，胚胎必须植入子宫并发育出胎盘以获取营养并促进气体交换。本文回顾了这一过程中最早发生的事件。胚胎只有在达到囊胚阶段时才能植入。囊胚由一团内部细胞即内细胞团和一层外层滋养外胚层（TE）组成，内细胞团发育成胎儿，滋养外胚层是胎盘的前体。囊胚和子宫都必须同步分化，以达到植入能够发生的适当成熟状态（活化的囊胚和接受性子宫）。TE与子宫内衬的腔上皮（LE）之间的相互作用启动了植入过程，可溶性信号以及相对表面上分子之间的结合似乎都参与其中。许多细胞表面分子与TE和LE之间的初始附着有关。这些分子包括硫酸乙酰肝素蛋白聚糖、Le-y和H-1型抗原、肝素结合表皮生长因子（HB-EGF）、滋养素-味觉素-贝辛复合物、整合素以及细胞外基质分子，如骨桥蛋白和层粘连蛋白。其他分子，如粘蛋白，可能需要被去除或修饰以允许粘附继续进行。文中讨论了这些成分作用的证据。
