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Women might soon be able to produce their own sperm in a development that could allow lesbian couples to have their own biological daughters, a pioneering study says.
Scientists are seeking ethical permission to produce synthetic sperm cells from a woman's bone marrow tissue after they showed it was possible to produce rudimentary sperm cells from male bone marrow tissue.
The researchers said they had already produced early sperm cells from bone-marrow tissue taken from men. They believe the findings show it may be possible to restore fertility to men who cannot produce sperm naturally.
But the results also raise the prospect of taking bone-marrow tissue from women and coaxing the stem cells within the female tissue to develop into sperm cells, said Professor Karim Nayernia of the University of Newcastle upon Tyne.
Creating sperm from women would mean they would be able to produce only daughters because the Y chromosome of male sperm would still be needed to produce sons.
The latest research brings the prospect of female-only conception a step closer.
"Theoretically it is possible. The problem is whether the sperm cells are functional or not. I don't think there is an ethical barrier so long as it's safe," Professor Nayernia said.
"We are in the process of applying for ethical approval. We are preparing now to apply to use the existing bone marrow stem cell bank here in Newcastle."
If sperm cells can be developed from female bone tissue they will be matured in the laboratory and tested for their ability to penetrate the outer "shell" of a hamster's egg - a standard fertility test for sperm.
But there is no intention at this stage to produce female sperm that would be used to fertilise a human egg, which would require the approval of the Human Fertilisation and Embryology Authority, Professor Nayernia said.
The immediate aim is to see if female bone marrow can be lured into developing into the stem cells that can make sperm cells. The ultimate aim is to see whether these secondary stem cells can then be made into other useful tissues of the body, he said.
The latest findings, published in the journal Reproduction: Gamete Biology, show that male bone marrow can be used to make the early "spermatagonial" stem cells that normally mature into fully developed sperm cells.
"Our next goal is to see if we can get the spermatagonial stem cells to progress to mature sperm in the laboratory and this should take around three to five years of experiments," Professor Nayernia said.
Last year, Professor Nayernia led scientists at the University of Gottingen in Germany who became the first to produce viable artificial sperm from mouse embryonic stem cells, which were used to produce seven live offspring.
Professor Nayernia's latest work suggests that it could be possible to develop the techniques to help men who cannot produce their own sperm naturally.
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