Embryos stick at it

Researchers from the University of California at San Francisco (UCSF) have discovered the process by which early embryos attach to the wall of the uterus and continue development. The research, published in the journal Science, may lead to new diagnostic processes and treatments for infertility and new contraceptives.

The research team, led by Susan Fisher from UCSF, took biopsies of the lining of the uterus from volunteers. This was done once at the time of the month when the uterus was known to be 'receptive' to the implantation of embryos, and again when the uterus was 'most receptive'. They discovered that the amount of carbohydrate on the uterine wall was at its highest when the uterus was at its most receptive.

The scientists worked out that embryos begin to secrete a sticky protein called L-selectin at about six days after fertilisation. As the embryo travels along the wall of the uterus, the protein binds to the carbohydrate causing the embryo to gradually slow until it stops. Fisher described the process as 'analogous to a tennis ball rolling over a table top covered with syrup. The embryo's journey is arrested by the sticky interaction with the uterine wall'. She added that failure of embryos to implant is one of the 'most common' causes of infertility.

Dr Roger Searle from the University of Newcastle in the UK said the study was further evidence of a 'dialogue' that takes place between the embryo and the womb before implantation. He added 'it's a radical idea, which is gaining more support, that the embryo is actually communicating with the uterus'.