Expression and function of cell surface extracellular matrix receptors in mouse blastocyst attachment and outgrowth.

Abstract

Abstract. Mouse-hatched blastocysts cultured in vitro will attach and form outgrowths of trophoblast cells on appropriate substrates, providing a model for implantation. Immediately after hatching, the surfaces of blastocysts are quiescent and are not adhesive. Over the period 24-36 h post-hatching, blastocysts cultured in serum-free medium become adhesive and attach and spread on the extracellular matrix components fibronectin, laminin, and collagen type IV in a ligand specific manner. Attachment and trophoblast outgrowth on these substrates can be inhibited by addition to the culture medium of an antibody, anti-ECMr (anti-extracellular matrix receptor), that recognizes a group of 140-kD glycoproteins similar to those of the 140-kD extracellular matrix receptor complex (integrin) recognized in avian cells by CSAT and JG22 monoclonal antibodies. Addition to the culture medium of a synthetic peptide containing the Arg-GlyAsp tripeptide cell recognition sequence of fibronectin inhibits trophoblast outgrowth on both laminin and fibronectin. However, the presence of the peptide does not affect attachment of the blastocysts to either ligand. Immunoprecipitation of 125I surface-labeled embryos using anti-ECMr reveals that antigens recognized by this antibody are exposed on the surfaces of embryos at a time when they are spreading on the substrate, but are not detectable immediately after hatching. Immunofluorescence experiments show that both the ECMr antigens and the cytoskeletai proteins vinculin and talin are enriched on the cell processes and ventral surfaces of trophectoderm cells in embryo outgrowths, in patterns similar to those seen in fibroblasts, and consistent with their role in adhesion of the trophoblast cells to the substratum.

Epidermal Growth Factor Enhances Invasive Activity of BeWo Choriocarcinoma Cells by Inducing .ALPHA.2 Integrin Expression

“…By culturing mouse embryos in culture vessels coated with ECM proteins, it was shown that at least three alpha integrins (a2, a6, and a7) are expressed when embryos attach to the matrix [46]. With regard to EGF action, direct effects of EGF and transforming growth factor alpha (TGF-a) on trophoblast outgrowth of the mouse blastocyst in vitro was demonstrated [20].…”

Complex patterns of expression suggest extensive roles for the α2β1 integrin in murine development

“…The expression pattern of the a2 integrin subunit in the maternal uterus and extraembryonic tissues suggested that asp1 may mediate cell interaction with collagedlaminin containing matrices during placental development. Indeed, Sutherland et al (1988) have shown that p1 integrins are necessary for trophoblast attachment and outgrowth on collagen and laminin in vitro. The ag integrin was expressed by spongiotrophoblasts located at the maternallembryonic junction and by decidual cells of the maternal uterus (Figs.…”

Molecular and cellular events involved in the completion of blastocyst implantation

“…The invasive trophoblasts of mouse blastocysts adhere, spread, and migrate on extracellular matrix (ECM) substrates [36][37][38][39] and penetrate the three-dimensional ECM structures [40]. The TE of the implantation-induced blastocyst alters its functional programming via changes in cell surface molecules.…”