Abstract
Implantation is a complex developmental process in which the early embryo becomes embedded in the uterine wall. A key step appears to be transformation of the uterine epithelium from a non-adhesive to an adhesive (hospitable) state under the influence of steroid hormones and cytokines. This period of uterine receptivity is known to be associated with numerous glycosylation changes, including changes in the glycolipid and glycoprotein composition of the uterine epithelium, the size and charge of the apical glycocalyx, and the profile of glycoproteins secreted into the luminal fluid. The embryo also undergoes rapid changes in carbohydrate antigen expression prior to implantation. These stage-specific changes may regulate the time and place of blastocyst attachment within the uterus. Severval testable hypotheses concerning the role of saccharides in implantation have emerged, invoking both carbohydrate-protein and carbohydrate-carbohydrate interactions.
