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Infertility Breakthrough in Reproductive Research

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About 15 per cent of reproductive age couples are deemed to be infertile. Among those, about six per cent have difficulties conceiving even if they undergo conventional assisted reproduction treatment like IVF.

In the past, there would have been little hope for identifying these couples. Now, as a result of a discovery by an international team, these couples can be identified and be provided with the appropriate treatment to increase their chances of conception. 

Researchers at the University of Hong Kong have been working alongside scientists from Imperial College London, Academia Sinica in Taiwan and the University of Missouri to unlock one of the secrets of sperm-egg binding.

Professor William Yeung and his team at HKU's Department of Obstetrics and Gynaecology played a key role in identifying the role of the sugar chain molecule sialyl-lewis-x sequence, or SLeX, on the egg that binds to a sperm. The discovery of the SLeX molecule has eluded researchers for 20 years.

SLeX makes the outer coat, or zona pellucida, of the egg sticky, allowing the sperm to bind to it, locking it in place. This sperm can then merge with the egg and begin the fertilisation process.

Using mass-spectrometric technology at Imperial College, the researchers were able to examine the chemical structure of the outer egg coat, while Professor Yeung and his team tested the theory that SLeX was the key egg-binding molecule. They conducted their research on donated, non-living eggs that had undergone failed assisted reproduction at Queen Mary Hospital.

"Our research is on infertility, specifically on molecules that affect the binding of the sperm to the outer coat of the eggs," said Professor Yeung. "Recently we found that one sequence, a sugar sequence on the outer coat of the eggs, is responsible for 70 per cent of the binding of the sperm to the eggs."

Infertile couples could now be tested to identify any defects in this key molecule or the related receptors, meaning more aggressive treatments could be targeted. Professor Yeung believes the discovery could also lead to new drugs that will treat infertility more effectively.