Experimental studies on the initial trophoblast endometrial interaction.

6.1. Attachment and penetration of the uterine epithelium in the human: The present studies describe to our knowledge the only studies of human in vitro attachment of blastocysts to uterine epithelial monolayers. From these studies, using other mammalian species as controls, it is concluded that initial attachment and penetration of the epithelium in the human might be of the intrusive type also seen in the Rhesus monkey (Lindenberg et al, 1986; 1989; Enders, 1972; 1976). This implicates an intensive and intimate cell-cell recognition and interaction already at the stage of epithelial attachment of the human embryo. 6.2. Oligosaccharide determinants in implantation: In the mouse we have identified an oligosaccharide Lacto-N-fuco-pentaose I, which inhibits blastocyst attachment to uterine epithelial cells in vitro. Monoclonal antibodies recognizing this epitope have identified LNF I-like determinants in the secretion and on the surface of the mouse endometrial epithelium during early pregnancy. LNF I-HSA/BSA-FITC conjugates have identified a receptor for LNF I on the surface of the blastocyst at the time of implantation. Furthermore, this study demonstrates a redistribution of these determinants prior to the day of implantation, supporting the hypothesis, that LNF I on the surface of the uterine lumen may contribute to the recognition and attachment even during the initiation of implantation. Component(s) carrying LNF-1 in the secretion might be regulatory molecules helping to secure the proper time for implantation in the mouse. 6.3: Future aspects. Whether the proposed mechanism of blastocyst-endometrium adhesion can be applied to species other than the mouse has still to be determined, but there are indications that this is worth testing.(ABSTRACT TRUNCATED AT 250 WORDS)