Scientists have identified the glue-like action that causes embryos to stick to the lining of a woman's uterus, a discovery that could lead to new treatments for infertility and new kinds of contraceptives.
The research, appearing Friday in the journal Science, explains for the first time what causes the embryo, floating freely in the reproductive tract, to stop and burrow into the wall of the uterus.
Researchers found the explanation by analyzing carbohydrate molecules on the surface of the uterus during different times of the female cycle and by identifying a protein, called L-selectin, on the surface of the embryo.
Susan J. Fisher of UC San Francisco, a co-author of the study, said coatings on the uterus and on the surface of the embryo act like puzzle pieces that touch and quickly lock.
"One piece of the puzzle is a protein on the embryo and the other is a very specialized carbohydrate sugar structure," said Fisher.
The sugar molecule on the surface of the uterus is secreted for only a short time during a woman's monthly cycle and the embryo, with its L-selectin coating, must arrive at the uterus during this time.
"It has to take place in exact synchrony or you don't get pregnant," said Fisher, noting that failure to implant on the uterus is one of the most common causes of a failed conception.
With this understanding of implantation, researchers may find new ways to help women time their efforts to get pregnant. The new research may also help develop contraceptives that are based on blocking the implantation of the embryo.