For many, a substantial part of the American Dream is to marry, settle down, and have a family. But for an estimated 10 percent of couples, a part of their dream becomes a nightmare when they find themselves unable to have children due to infertility issues of either or both prospective parents. However, new hope for forward advancement in battling infertility has sprung from the research of an international team that has discovered how a human egg catches a sperm in the fertilization process.
Results of the new study, led by Professor Anne Dell from the Department of Life Sciences at Imperial College London, have shown that a sugar chain called the sialyl-lewis-x sequence, or SLeX, is responsible for egg/sperm binding since it is highly abundant on the egg's outer coat.
The sugar molecule makes the outer layer of the egg “sticky,” which allows the egg and sperm to bind. Dell was joined in the research by a team of researchers from the college, as well as teams from the University of Missouri, the University of Hong Kong, and the Academia Sinica in Taiwan.
Although researchers have known for years that proteins on the head of sperm are able to find and identify an egg by a variety of sugars contained in the egg’s outer coating, until now it has remained unclear as to which specific sugar molecule led to an egg match, allowing the outer surfaces to bind together before merging, and leading to the sperm releasing its DNA to fertilize the egg.
Regarding the breakthrough, Dell said, “Unraveling the composition of the sugar coat that shrouds the human egg is the culmination of many years of painstaking research by mass spectrometry colleagues at Imperial.” She commended the team of researchers by saying, “This endeavor was an enormously difficult task because human eggs are very tiny—about the size of a full stop—so we didn’t have much material to work with.”
Couples facing infertility can experience extreme emotional and physical stress, and the inability to start a family can wreak havoc on a marriage. Women who are unable to conceive suffer depression, and may feel shame because they are unable to do what millions of other women do so easily—have a child. In the United States, the Centers for Disease Control and Prevention estimates that among women ages 15 to 44, about 7.3 million (11.8 percent) have an impaired ability to have children and have turned to infertility services in hopes of conceiving a child. The number of married women in the same age group who are considered infertile (unable to get pregnant for at least 12 consecutive months) totals approximately 2.1 million (7.4 percent).
The researchers are hopeful that their findings will lead to a better understanding of what causes infertility, and that they will lead to the creation of more effective fertility drugs in the long-term that will help childless couples to conceive.
“We hope that our study will open up new possibilities for understanding and addressing the fertility problems that many couples face,” said senior study author Dr. Poh-Choo Pang, from the Department of Life Sciences at Imperial College London. Pang then added, “Although clinical treatments are still a way off, we are very excited about the new research into fertility that we hope will now be possible, building on our work.”
While the new research brings hope to millions of childless couples, the American Society for Reproductive Medicine (ASRM) points out that many factors can affect a woman’s ability to conceive that range from age, smoking history, and presence of sexually transmitted infections, to whether they are overweight or underweight. In addition, a recent U.S. study found that 20 percent of infertile women suffered from some type of eating disorder.
However, couples who are unable to conceive right away need not panic. According to the National Institute for Health and Clinical Excellence, among women aged 35, approximately 94 out of every 100 who have regular unprotected sexual intercourse will get pregnant within 3 years. Yet, as women age, the percentages of success decline. For example, at the age of 38, only 77 out of every 100 women who regularly have unprotected sex will conceive.
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