Differentiation of the nonadherent trophectoderm cells of the mammalian embryo into attachmentcompetent trophoblast cells appears to be a prerequisite to invasion of the uterine stroma. To investigate the molecular basis of trophoblast differentiation free of maternal environmental constraints, we used a model system in which attachment and outgrowth of trophoblast cells occurs in vitro. Recently, it was found that either fibronectin or laminin, both of which are extracellular matrix glycoproteins of the uterine stroma, will support trophoblast outgrowth in vitro. In this study we report that the outgrowth of blastocysts on fibronectin-coated dishes is inhibited in a dose-dependent manner by the presence of a hexapeptide containing the sequence ArgGly-Asp, which has been shown previously to be recognized by the fibronectin receptor. This peptide had no effect on lamininmediated trophoblast outgrowth, suggesting that the trophoblasts contain different cell surface receptors for fibronectin and laminin. Trophoblast attachment and limited outgrowth also could be obtained on dishes to which the hexapeptide Gly-Arg-Gly-Asp-Ser-Pro was coupled. Under these conditions, however, outward migration of the trophoblast cells appeared to be reduced. Vitronectin, another adhesion molecule that apparently binds to cells via a cell surface receptor that recognizes Arg-Gly-Asp sequences, also was capable of supporting trophoblast outgrowth. These findings suggest that differentiation of cells of the trophectoderm into trophoblast cells with an invasive phenotype may involve the production of cell surface receptors for fibronectin and possibly for other proteins that contain the Arg-Gly-Asp recognition sequence.Over the past few decades, considerable information has accumulated about molecular events in early embryonic development of echinoids and amphibians. Progress with these organisms has been rapid because large numbers of embryos are available, and they can be cultured in vitro in simple medium containing only inorganic salts. In contrast, progress on mammalian embryos has been relatively slow: the supply of embryos is limited and, under normal physiological conditions, the embryos develop within the complex environment of the oviduct and the uterus. A major step forward in studies on the development of mammalian embryos was made when a culture medium was described that permitted mammalian development in vitro to the somite stage (1). Since that time, however, efforts to simplify the medium have met with limited success.Recently, however, we reported that all undefined protein components in an in vitro system for mouse embryos could be eliminated (2). It was established that embryos cultured in a defined medium supplemented with only bovine serum albumin developed normally from the four-cell stage, with subsequent trophoblast attachment to and outgrowth on plastic dishes precoated with either fibronectin or laminin, two known components of the endometrium (3-5).A number of studies have revealed the presence of a cel...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.