Spermatid injection technique allows 'sterile' men to become fathers

Men previously considered sterile have successfully fathered children thanks to a newly improved technique called round spermatid injection (ROSI).

The technique was trialled by Japanese scientists, and resulted in 14 children born to 12 couples from 2011 to 2014. The men were classed as sterile because their sperm had not developed into a classic tadpole shape, instead remaining round.

Dr Atsushi Tanaka, from the Institute for Assisted Reproductive Technology in Fukuoka, Japan, who led the trial, said: 'Although the current success rate of round spermatid injection is not very high compared with ICSI, intracytoplasmic sperm injection, this procedure can be the last resort for men who cannot produce spermatozoa but wish to use their own genetic material to produce offspring.'

These round cells are found in 30 percent of men with non-obstructive azoospermia, which affects just under one percent of the general male population. These men are deemed sterile, and couples are advised to use donor sperm to conceive.

The technique involves injecting these immature sperm directly into a woman's egg. It was first used in the 1990s, resulting in the birth of several babies, including one in the UK (Susan Louise Oxburgh, born in 1996). However, it was banned by the UK HFEA, Human Fertilisation and Embryology Authority, because of concerns about potential genetic abnormalities in these immature sperm as well as low success rates.

In the recent study, which was published in PNAS, the scientists further developed the ROSI technique by including activation with an electric current. They trial involved 76 men, using 734 eggs in total. The success rate was 16 percent overall. The children were found not to have any unusual physical, mental or epigenetic problems.

'This study is a bit like a rugby ball from leftfield. We thought that this idea was dead, that it would never be useful again. This potentially offers some of the one percent of men who don't produce sperm an interesting option,' Allan Pacey, Professor of Andrology at Sheffield University, told the Guardian.

Incorporating electrical charge to the ROSI was 'a modern twist on an old idea', he said, adding, 'This new study goes some way to making us rethink whether or not this is an avenue that we should be looking at again.'

The study authors acknowledge that further studies are needed to establish the safety and clinical value of ROSI, especially as it is less efficient than well-established methods such as IVF or ICSI. They also believe efficiency could be improved by screening sperm before use.