Synthetic human sperm have been grown from embryonic stem cells for the first time, scientists claimed yesterday, raising the prospect of advances in male infertility treatment.

The culture of swimming human cells with tails and some of the biological characteristics of real sperm has been created at Newcastle University.

The achievement, from a team led by Professor Karim Nayernia, suggests that it may be possible to grow new reproductive cells from stem cells, enabling men who make none of their own to father children.

That, however, would require a change in the law, because the use of such in-vitro derived (IVD) sperm for reproduction was banned in Britain by the Human Fertilisation and Embryology Act last year.

The research also suggests that it is impossible to create synthetic sperm from female stem cells, ruling out the prospect that lesbian couples could conceive without a male sperm donor.

Professor Nayernia said that the IVD sperm had key traits of real sperm, including a haploid nucleus that has 23 chromosomes, instead of the 46 found in non-reproductive cells. “These cells are haploid, they have tails and a head, and they swim,” he said. “The only cells in the body that are like that are sperm.”

Other scientists, however, said that although the cells had some similarities to sperm, further tests would be needed to confirm that they were the real thing. Professor Nayernia accepted that more research was needed.

He said that the findings, published in the journal Stem Cells and Development, nonetheless represented a milestone in efforts to grow sperm from stem cells and should provide insights into fertility.

“This is an important development as it will allow researchers to study in detail how sperm forms and will lead to a better understanding of infertility in men — why it happens and what is causing it,” he said. “This understanding could help us develop new ways to help couples suffering infertility so they can have a child which is genetically their own.”

Professor Nayernia’s team has previously grown immature human sperm from stem cells taken from bone marrow, and has made sperm from mouse embryonic stem cells that is capable of fertilising eggs and producing pups.

The Newcastle research has gone farther, using human embryonic stem cells to produce what appear to be mature sperm. Professor Nayernia intends to inject the sperm into animal eggs to determine whether they are capable of fertilisation and to conduct microscopic examinations to check their similarity to genuine sperm.

If the work progresses, it could be possible to reprogramme adult cells from an infertile man into an embryo-like state and then grow these into sperm that carry his genetic material.

Professor Nayernia had previously suggested that this process might also be capable of making “female sperm”, to allow lesbian couples to conceive without a man, but his research has ruled this out. It showed that although female stem cells could make immature sperm, only stem cells with a Y chromosome could make the mature version.

Independent experts welcomed the research but questioned whether the cells produced were true sperm. Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: “While the cells produced may possess some of the distinctive genetic features and molecular markers seen in sperm, fully differentiated human spermatozoa have specific cellular morphology, behaviour and function that are not described here.”

He added, however, that he supported the research, which “could help us answer some important questions about how sperm are made and why some men are sub-fertile”.

The Liberal Democrat MP Evan Harris said progress could be held up by the law. “It is very sad that the recent Human Fertilisation and Embryology Act did not take the opportunity to provide a power for Parliament to approve clinical trials of stem cell derived sperm as a treatment for male infertility by regulations. Instead, the actual use of these gametes [sperm and eggs] — even when derived from adult stem cells where no embryo is used — in the treatment of infertile couples will require primary legislation. This makes it more difficult to attract funding for the application of this research despite the Government always banging on about the importance of translational research.”

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