Sperm from stem cells?

Researchers in Japan are close to producing mouse sperm from mouse stem cells, according to a report in last week's New Scientist. The article claims that scientists at the Mitsubishi Kagaku Institute of Life Sciences have produced normal mouse sperm by selecting mouse germ cells from embryo stem cell grown in the laboratory, and then transplanting them into testicular tissue. After three months, the team found that the cells had divided and multiplied to produce apparently normal sperm.

Their findings have yet to be verified, and have not appeared in a peer-reviewed publication, but the news has triggered speculation of an 'IVF revolution'. Last week, a group of US scientists reported the first successful production of mouse eggs from stem cells in the laboratory, an achievement that could have implications for both infertility and 'therapeutic cloning' research. In theory, eggs could be produced from both male and female embryo stem cells, the body's 'master cells', capable of turning into a wide range of body tissues. But sperm could only be produced from male stem cells, since they require the presence of a Y chromosome, as well as chemical signals produced by the testes. Although it remains to be seen whether human egg and sperm cells could be produced from stem cells in this way, the New Scientist article speculates that such technology could be used to treat infertility, allow two men to have a biological child of their own, or even allow 'self-fertilisation' by a man to produce a child (the latter two scenarios involving a surrogate mother). Geneticist Azim Surani, of Cambridge University, says that for now, the potential risks of the technology rule out such uses. However, he added that 'it's always good to have these kinds of debates of potential ethical issues'.

The ability to produce human eggs and sperm in the laboratory might eventually provide a safe alternative to human reproductive cloning as a treatment for infertility. US cloning expert Rudi Jaenisch told delegates at a recent human genome meeting in Mexico that the process of egg and sperm production naturally reprogrammes cells in readiness for fertilisation. Producing egg and sperm cells from cloned human embryo stem cells, which could then be used for IVF treatment, might therefore bypass the problems currently associated with animal cloning, thought to arise because of reprogramming errors resulting from the cloning process. Such a technique 'would satisfy the desires of most of the couples who want [reproductive] cloning' said US medical ethicist Dorothy Wertz. 'Most don't want a clone - just a baby' she added.