Scientists reveal embryos secrets

 

Discovery could lead to help for infertility, new contraceptives

 

WASHINGTON, Jan. 17 Scientists have identified the glue-like action that causes embryos to stick to the lining of a womans 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 the University of California, San Francisco, and 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 womans 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 dont get pregnant, said Fisher, noting that failure to implant on the uterus is one of the most common causes of a failed conception

Only 50 to 60 percent of all conceptions advance beyond 20 weeks and of pregnancies that are lost, 75 percent represent a failure of implantation, she said.

FERTILITY TREATMENTS
       With this understanding of implantation, researchers may find new ways to help women time their efforts to get pregnant, both naturally and in fertility clinics.

Fisher said it may be possible in fertility clinics to coat embryos with the sugar molecule and help uterus adhesion.
       If we can launch the implantation (process) in the culture dish then you might be able to implant fewer embryos and have greater certainty of a successful pregnancy, she said.

Currently, fertility clinics can prompt successful pregnancies 25 percent to 40 percent of the time. By more precisely timing implantation, based on the readiness of the uterus to adhere to the embryo, these chances could improve, said Fisher.