Dr Jess Buxton, Progress Educational Trust
19 July 2007
[BioNews, London]
Researchers in South Korea have developed a new method for choosing the best sperm to use during ICSI (intracytoplasmic sperm injection) treatment - a variation of IVF in which a single sperm is injected directly into an egg. The team, based at the Chung-Ang University in Gyeonggi-Do, found that when placed in a solution that makes them swell up, genetically abnormal sperm tend to differ in appearance to healthy sperm. Study leader Myung-Geol Pang presented the findings at the annual European Society for Human Reproduction and Embryology conference earlier this month, New Scientist reports.During natural conception, healthy sperm are much more likely to fertilise an egg than sperm containing major genetic faults. So any 'aneuploid' sperm - those which have chromosome errors that could affect normal development - are usually left behind. However, this selection process is bypassed in ICSI, a method used to help treat men with very low sperm counts. As Ulrik Kvist, of the Karolinska Institute's Andrology Centre in Stockholm, Sweden explains: 'It's a short cut to the egg, so better methods are needed to screen out the bad sperm from the good'.
In the latest study, the scientists used the 'hypo-osmotic swelling test' (HOST) to examine the appearance of normal and abnormal sperm, and stained the sperms' chromosomes using fluorescent dyes, to find out which were genetically normal. They examined more than 16,000 sperm cells from three fertile men and six with low sperm counts, and found that faulty sperm look different to their healthy counterparts when subjected to this analysis. Their results showed that when selected in this way, there was a 20-fold decrease in the numbers of aneuploid sperm in the samples taken from men with low sperm counts. According to Pang, 'this is much lower than the frequency of anueplidy in sperm taken from healthy men'.
The team now wants to test whether sperm selected using the new method result in healthier embryos. 'If it works it would potentially be very beneficial', Alan Handyside of the Bridge Fertility Clinic in London told New Scientist.
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Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.