British researchers have turned human bone marrow tissue into primitive sperm cells, raising hopes that it may be possible for women to produce their own sperm. Biologist Karim Nayernia, of the University of Newcastle-upon-Tyne, obtained mesenchymal stem cells from four adult men about to undergo bone marrow transplants. His team managed to morph these into spermatogonium cells, from which mature sperm capable of fertilising eggs originate.

This work is quite preliminary, as no functioning sperm have been created yet. Furthermore, other biologists warned that manipulating the stem cells could lead to permanent genetic changes and abnormalities. However, Dr Nayernia is optimistic that infertile men could use the technique to conceive naturally. And lesbians could also use the technique to produce their own biological daughters. No time line was reported.