UMR935, Inserm, Villejuif, France.
Université Paris Saclay, Université Paris Sud, Faculty of Medicine, Le Kremlin Bicêtre, France.
Reproduction. 2020 Mar;159(3):R151-R172. doi: 10.1530/REP-19-0348.
In ungulates, early embryonic development differs dramatically from that of mice and humans and is characterized by an extended period of pre- and peri-implantation development in utero. After hatching from the zona pellucida, the ungulate blastocyst will stay free in the uterus for many days before implanting within the uterine wall. During this protracted peri-implantation period, an intimate dialog between the embryo and the uterus is established through a complex series of paracrine signals. The blastocyst elongates, leading to extreme growth of extra-embryonic tissues, and at the same time, the inner cell mass moves up into the trophoblast and evolves into the embryonic disc, which is directly exposed to molecules present in the uterine fluids. In the peri-implantation period, uterine glands secrete a wide range of molecules, including enzymes, growth factors, adhesion proteins, cytokines, hormones, and nutrients like amino and fatty acids, which are collectively referred to as histotroph. The identification, role, and effects of these secretions on the biology of the conceptus are still being described; however, the studies that have been conducted to date have demonstrated that histotroph is essential for embryonic development and serves a critical function during the pre- and peri implantation periods. Here, we present an overview of current knowledge on the molecular dialogue among embryonic, extraembryonic, and maternal tissues prior to implantation. Taken together, the body of work described here demonstrates the extent to which this dialog enables the coordination of the development of the conceptus with respect to the establishment of embryonic and extra-embryonic tissues as well as in preparation for implantation.
在有蹄类动物中，早期胚胎发育与小鼠和人类有很大的不同，其特点是在子宫内有一个延长的胚胎前期和植入前期发育阶段。从透明带孵出后，有蹄类动物的囊胚将在子宫内自由停留数天，然后再植入子宫壁内。在这个漫长的植入前期，胚胎和子宫之间通过一系列复杂的旁分泌信号建立了密切的对话。囊胚伸长，导致胚胎外组织的极度生长，同时，内细胞团向上移动到滋养层中，并演变成胚胎盘，胚胎盘直接暴露于子宫液中存在的分子。在植入前期，子宫腺分泌多种分子，包括酶、生长因子、黏附蛋白、细胞因子、激素和营养物质，如氨基酸和脂肪酸，统称为组织滋养层。这些分泌物质的鉴定、作用和对胚胎生物学的影响仍在描述中；然而，迄今为止进行的研究表明，组织滋养层对于胚胎发育是必不可少的，并在植入前和植入前期发挥关键作用。在这里，我们概述了目前关于植入前胚胎、胚胎外和母体组织之间分子对话的知识。总之，这里描述的工作表明，这种对话在多大程度上协调了胚胎的发育，以及胚胎和胚胎外组织的建立，并为植入做准备。
