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The embryos developed normally  CREDIT: DR. KATSUHIKO HAYASHI
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Artificial eggs have been grown in a petri dish for the first time and used to create living animals in a breakthrough hailed as ‘remarkable’ by British experts.

Scientists in Japan proved it is possible to take tissue cells from the tail of a mouse, reprogramme them as stem cells and then turn them into eggs in the lab.

The ‘eggs in a dish’ were then fertilised and the resulting embryos were implanted in  female mice which went on to give birth to 11 healthy pups.This  is a remarkable achievementProf Martin Johnson, University of Cambridge

If the procedure is found to work in humans it could help more women become mothers. Women are born with all their eggs, so can struggle to conceive as they grow older because their eggs also age.

But if eggs could be made from stem cells they would be brand new, and may even produce healthier babies.

The technique could also help women who are born with fewer eggs than normal, or whose ovaries have stopped releasing eggs. Scientists say it could even help to bring back extinct animals.

Professor Katsuhiko Hayashi, of the department of developmental stem cell biology at Kyushu University, said: “This is the first time a functional egg has been produced from stem cells in culture which gives us some clue to human egg production from stem cells.

“We need to now carefully look at the quality of mouse artificial eggs. This kind of quality check will contribute to an application to humans in future.”

The scientists took cells from a mouse tail and programmed them to become pluripotent stem cells, which can go on to produce any type of cell.

They then created a chemical soup in the lab which mimicked the conditions of  an ovary, to encourage the stem cells to become follicles – tiny tubes found in the ovaries which produce eggs. From those follicles, the scientists were able to harvest healthy eggs.

The team then fertilised the eggs using mouse sperm and implanted them into female mice, from which 11 healthy pups were born.

British experts hailed the research as ‘very important’, a ‘remarkable achievement’ and the ‘first convincing evidence’ that eggs could be made entirely artificially.

Richard Anderson, professor of clinical reproductive science at theUniversity of Edinburgh, said: “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 of egg development.

“Although we are a long way from making artificial eggs for women at the moment, this study also provides us with a basis for experimental models to explore how eggs develop from other species, including in women.

“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.”

Mouse pups born through the procedure 
Mouse pups born through the procedure  CREDIT: DR. KATSUHIKO HAYASHI

Martin Johnson, professor of reproductive science at the University of Cambridge, added: “This  is a remarkable achievement, involving good quality research.

“(It is) potentially of clinical interest to those patients lacking eggs of their own.”

However some scientists said the process could be hindered by the fact that in humans eggs take more than 10 years to fully develop after birth, not maturing until puberty.

Prof Robin Lovell-Badge, group leader, The Francis Crick Institute, said “This is the first convincing evidence that it is possible to go all the way from pluripotent stem cells to functional eggs entirely [in the lab], which can then be fertilised and give rise to apparently healthy mice.

“Clearly, if applied to humans, being able to get functional eggs would have importance in overcoming female infertility, e.g. due to cancer treatment as a child, but it also opens up many other uses in research, in regenerative medicine, and potentially in avoiding genetic disease

“There is a long way to go before these methods could be adapted and used in humans. There is the question of time. It usually takes longer than a decade to have fully grown eggs in humans.

“Will it take this long to recapitulate the process in vitro, which would pose immense practical challenges, or will parts of the process speed up in vitro where the constraints that normally operate in vivo will be absent?”

The mouse pups at four weeks old 
The mouse pups at four weeks old  CREDIT: DR. KATSUHIKO HAYASHI

The Japanese team warned that the pups had different genetic expression compared with control animals, and some chromosomal abnormalities, although all appeared to be healthy. British experts warned that the research could throw up ethical problems if used in humans.

“I would say that fully mature and functional ‘eggs in a dish’ should be first produced in large animals – pigs, sheep and cows – before attempting human,”  said Prof James Adjaye, director of the institute for stem cell research and regenerative medicine at the University of Düsseldorf.

“It is all a matter of ethics. It would be interesting to allow deriving human ‘eggs in a dish’ but not to be fertilised.”

The research was published in the journal Nature.

 
 

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