Scientists have for the first time managed to create sperm from mouse stem cells capable of fertilising eggs and resulting in live births. A team led by Professor Karim Nayernia, now Professor of Stem Cell Biology at Newcastle University, began with mouse embryonic stem cells (ES cells) which they sorted in order to isolate cells that were capable of becoming sperm precursor cells. These spermatogonial stem cells were then encouraged to grow into adult sperm and, when mature, were injected into mouse eggs. The resulting early embryos were implanted into surrogate mouse mothers. Two hundred and ten eggs were injected with the artificially-derived sperm, 65 began to undergo cell division and seven live births resulted, with six of the animals achieving adulthood. The work was done in Professor Nayernia's previous position at the Georg-August University in Gottingen and is reported in the journal Developmental Cell.
The mice that resulted from the research were able, with one exception, to develop into adult animals. However, despite managing to achieve maturity, all the animals suffered from problems and died within five months of birth. The mice were either larger or smaller than normal animals due to abnormal growth rates, probably through problems with imprinting - changing the pattern of genes expressed in the embryo - similar to that suffered by cloned animals. The work is important for the insight that it gives to researchers looking at problems in sperm development and may one day help to develop new treatments for male infertility. Professor Nayernia was optimistic that the problems with the mice could be solved reasonably quickly, and he predicted that although, 'we cannot find a universal treatment for all male infertility - at least we can find, I believe in five years, a resolution for some kinds of male infertility'.
Estimates suggest that one in seven couples in the UK have difficulty conceiving, about one per cent of all men don't produce sperm and a further 3-4 per cent of men have a low sperm count. Dr Allan Pacey, honorary secretary of the British Fertility Society and a senior lecturer in andrology, said, 'To be able to make functional sperm under controlled conditions in the laboratory will be very useful to study the basic biology of sperm production. There are currently many things we don't know about how sperm are formed let alone why it sometimes goes wrong and leads to infertility in some men'.
There are also many ethical considerations raised by this work. Anna Smajdor, a researcher in medical ethics at Imperial College London, described the work as 'a hugely significant breakthrough', but warned that, 'being able to create these cells in the laboratory will pose a serious conceptual challenge for our society. Who is the father of offspring born from laboratory sperm? A collection of stem cells in a Petri dish?' She continued: 'Sperm and eggs play a unique role in our understanding of kinship and parenthood, and being able to create these cells in the laboratory will pose a serious conceptual challenge for our society'.