An infertility molecule found in mice may help to improve the success rate of millions of women who have fertility treatments each year, an international team of scientists said on Wednesday.

As many as one in six couples may have an infertility problem. Although the causes are varied, the failure of an embryo to implant in the woman’s womb is thought to be an important cause of unexplained infertility.

But scientists in the United States and Japan have identified a receptor molecule called LPA in mice that is linked to implantation and which could lead to new treatments for infertile couples.

“This is a receptor that wasn’t on anyone’s radar screen from a fertility standpoint,” said Jerold Chun, of The Scripps Research Institute in La Jolla, California.

If the molecule works the same way in humans, it could be a new target for treatments to improve implantation rates in women having fertility treatment.

Most couples having treatment are able to produce embryos thanks to advances in technology and an improved understanding of human reproduction. But only about 20 percent of them successfully implant in the womb. Chun and colleagues at the University of Tokyo in Japan and other U.S. centres who worked on the research said the LPA receptor has “a clear effect on the ability of embryos to implant and position normally.”

In research reported in the science journal Nature, the scientists genetically engineered mice that lacked the LPA molecules, which normally appear on the surface of cells in the animal’s womb.

The mice were able to produce normal, healthy embryos but they would not implant and grow in the womb. The loss of the LPA receptors also affected the rodents’ level of prostaglandin, a fatty acid essential for normal implantation.

“Low implantation rates are common in women undergoing assisted reproduction, posing a challenge to both patients and doctors, so researchers are striving towards a deeper understanding of this process,” said S.K. Dey, of Vanderbilt University Medical Center in Nashville, Tennessee, in a commentary.

A healthy couple in their mid-20s having regular sex has about a one-in-four chance of conceiving in a given month. infertility is defined as the inability to achieve a pregnancy after a year of trying.

SOURCE: Nature May 4, 2005.