A new technique for preserving sperm could offer men with low sperm counts, cancer, or viruses such as HIV the hope of fathering healthy children.
Experts found that fast-freezing sperm preserves its ability to swim towards an egg far more efficiently than the slow-freezing method currently in use.
The study, from experts in Chile and Germany, will be presented at the World Congress of Fertility and Sterility in Munich.
Current slow-freezing techniques mean the sperm only retains 30 to 40 per cent of activity. But rapid freezing - also known as vitrification - allows that figure to rise to almost 80 per cent.
Vitrification is already used to quick-freeze eggs and embryos with success, allowing spare ones to be used in IVF at a later date.
Following thawing, more eggs and embryos survive with vitrification than with older, slower cooling techniques.
In vitrification, cryopreservation agents are added to lower the water content in cells and prevent ice crystals building up.
In the latest study, plasma was separated and removed and the sperm placed in a sucrose solution before being plunged into liquid nitrogen to fast-freeze.
When sperm was rethawed in the study, it regained motility (77 per cent versus 29 per cent with slow cooling) and showed less damage.
The removal of plasma means HIV and other viruses can be removed, giving HIV positive men the chance of fathering a child without the likelihood of passing on the virus to mother or baby.
Men with a low sperm count and whose sperm is deteriorating in quality over time would also benefit from the technique.
Some men with low sperm counts fail to produce a good enough sample when it is time for IVF. The new technique could also allow several samples to be put together as one.
Lead researcher Professor Raul Sanchez, from La Frontera University in Chile, said: 'This work shows that we can preserve functional sperm via vitrification, which gives a greater chance of success for patients with low sperm counts.
'The other great advantage of this technique is that it can eliminate potential sources of infection such as Aids or hepatitis B, which are present in seminal plasma.
'It (also) has the potential to allow HIV positive men to have children without worrying about transmitting the virus.'
Ian Cooke, professor emeritus at Sheffield University and education director for the International Federation of Fertility Societies, said: 'This looks a very exciting technique as it is much faster than the conventional slow-freeze procedure.
'In addition, the prospect of use with HIV positive patients has great potential, although we'd want to confirm the absence of residual HIV in sperm samples before going ahead.'
Article: Monday 13th September 2010 www.dailymail.co.uk
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