受精胚が子宮に接着するしくみが判明した

受精卵が子宮内膜に着床する第一段階の仕組みが発見された。胚はselectinsという蛋白質に被われているが、排卵後の子宮内膜の表面にはselectinsと結合する炭水化物が産生され着床が成立するという。この発見は不妊症の治療や流産の治療に役立つものと考えられている。

Scientists Discover How Embryo 'Catches' in Womb
By Amy Norton
NEW YORK (Reuters Health) - Scientists have discovered what might be the first crucial step needed for an embryo to take up residence in the womb--a finding experts say could prove useful in treating infertility.
The study shows that during the short window of time that implantation in the uterus is possible, human embryos are coated with proteins called selectins, which are designed to latch onto carbohydrates.
Meanwhile, after ovulation, the lining of the uterus develops carbohydrate molecules that reach out to these selectins.
The synchronization of these two events means that when the early embryo comes rolling along, it is able to firmly take hold of the uterine wall, burrow beneath the surface and go about the business of forming a placenta.
"We think we have discovered an important part of the mechanism that initiates the implantation process," Dr. Susan J. Fisher of the University of California, San Francisco told Reuters Health.
This is "significant," according to Fisher, because researchers may be able to use this knowledge to improve treatments for the infertile.
On the "uterine side" of things, she noted, it might be possible to determine whether a woman's womb is fully ready to support an embryo by looking at the carbohydrate molecules on the uterine lining.
Fisher and her colleagues report their findings in the January 17th issue of Science.
Human reproduction as a whole is considered "terribly inefficient," Fisher said, adding that a majority of pregnancy losses occur around the time of implantation.
Indeed, despite recent advances in infertility treatment, the mystery of normal embryo implantation has been a "major limiting factor" in treatment success, according to a commentary published with the report.
Now this study suggests that the selectin-carbohydrate bond "may constitute the initial step in the implantation process," write Asgerally T. Fazleabas and J. Julie Kim of the University of Illinois in Chicago.
"We can now begin to unravel the molecular mechanisms that are critical for understanding the process of human embryo implantation," they write.
It's problems in these initial steps, the authors note, that may be responsible for early miscarriages that are not caused by chromosome defects in the embryo.
SOURCE: Science 2003;299:405-408.