The birth of baby mice made from artificial eggs has prompted calls for a public debate on whether the same approach should ever be offered by fertility clinics.
Nearly a dozen rodents were born after scientists created the early-stage mouse eggs from stem cells and nurtured them in the lab until they were mature enough to fertilise with mouse sperm.
The team went on to make hundreds of embryos from the lab-grown eggs and implanted them into female mice, leading some to give birth to apparently healthy mouse pups.
Though far from ready for use in humans today, the procedure could potentially be improved upon in coming years and eventually made safe enough to treat couples with fertility problems, scientists said. The technology suggests it may one day be possible for doctors to make viable eggs for the skin cells of an infertile woman.
“This is the first report of anyone being able to develop fully mature and fertilisable eggs in a laboratory setting right through from the earliest stages,” said Richard Anderson, a consultant in reproductive medicine at the Royal Infirmary of Edinburgh.
“One day this approach might be useful for women who have lost their fertility at an early age, as well as for improvements in more conventional infertility treatments,” he added.
Writing in the journal Nature, Katsuhiko Hayashi at Kyushu University describes how he created some of the primitive mouse eggs from embryonic stem cells, and others from skin tissue taken from a mouse tail. The scientists went on to put more than 300 two-day-old embryos into female mice, but only 11 pregnancies ended in normal births.
The high failure rate, and the potential risks to the young, are among the many hurdles that scientists will have to solve to perfect the procedure. Tests on the artificial eggs found that many had unusual patterns of gene expression, suggesting they had not developed in the same way as natural eggs.
But with stem cell science progressing so fast, some researchers are keen to thrash out the potential implications for humans now. “Ethically, this issue has yet to be discussed fully by scientists and society,” said Azim Surani, a stem cell scientist at the Gurdon Institute at Cambridge University, who was not involved in the latest work. “This indeed is the right time to start a debate and involve the wider public in these discussions, long before, and in case, the procedure becomes feasible in humans.”
Labs around the world are now expected to repeat the experiments before attempting the same procedure in larger animals, such as pigs, sheep and cows. Before it can help humans to multiply, it might benefit other animals. “With such technology we might be able to rewind the process of mammalian extinction,” said Dusko Ilic at stem cell scientist at King’s College London.