Live mice have been born from eggs grown to maturity under the kidney capsules of rats.
Immature eggs from mammals, including humans, are notoriously difficult to grow in test tubes. So if the new technique works for species other than mice, it would provide an better way of growing eggs that could be used to help save endangered species, and even to improve fertility treatments for women.
鈥淚t鈥檚 an important proof of concept. It shows you can get live offspring from grafted ovarian tissue,鈥� says Jock Findlay, deputy director of the Prince Henry鈥檚 Institute in Melbourne, Australia.
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Shae-Lee Cox and her colleagues at Monash University in Melbourne took ovaries out of young mice, cut them in half, and transplanted them under the kidney capsules of female rats. The type of rat used has a defective immune system, and so was less likely to reject transplanted tissue. Three weeks later the mature eggs were collected, inseminated with mouse sperm, and the resulting embryos put into surrogate mother mice.
Five pups were born from the 65 embryos that were transplanted into the mice. 鈥淚t sounds low, but if we get even one animal from an endangered species using this technique that would be a success,鈥� Cox told 快猫短视频.
The announcement of the work comes shortly after other researchers revealed success in developing ways of collecting semen from live and dead animals, and for growing testes tissue on the backs of mice.
Hairy-nosed wombat
One potential use for the egg-growing technique is to increase the numbers of endangered species, such as the Northern hairy-nosed wombat. Only 100 or so of these are left in the wild.
Ovarian tissue collected from those species could be grown into eggs in rats, fertilised and implanted into closely related species that are not endangered.
Team members Melanie Snow and Michelle Cleary are already developing methods for collecting ovarian tissues from wallabies and wombats that have been killed on the road. 鈥淚f you get to them within 24 hours, they still contain viable eggs,鈥� says Cox.
Freeze and thaw
The new technique could also be used to develop better ways of treating infertility in women. Other researchers have grown human eggs to the stage just prior to ovulation in mice (Human Reproduction, vol 16, p 417).
Women with cancer would like to be able to freeze their ovarian tissue and have it transplanted back after they have had their cancer therapy, which kills eggs. But although there have been a few attempts at such transplants, none has yet resulted in a pregnancy.
Growing human ovarian tissue in rats is also is a good way of testing new freezing and thawing techniques, says Cox.
In the future, the techniques might even be developed to use rats to grow human eggs for IVF procedures. 鈥淏ut it鈥檚 a long way down the track, and it could only happen after a lot of testing, and careful thought about the ethical and infectious disease ramifications,鈥� says Findlay.
Journal Reference: Science (vol 297, p 2227)