Frozen ovaries transplanted in sheep

Israeli scientists have successfully retrieved eggs from ovaries that had been frozen, thawed and transplanted in sheep in a project that could provide new hope for infertile women.

Researchers at the Institute of Animal Science, Agriculture Research Organisation in Bet Dagan, has said that the research showed it was possible to restore ovarian function following a transplant in a large animal.

They now hope to test the technique in humans.

"This approach could revolutionise the field of cryopreservation [freezing] for diverse human applications, such as organ transplants, as well as helping women who face the loss of their fertility," said Dr Amir Arav, the head of the research team.

The technique could help young cancer patients whose fertility could be damaged by treatments such as radiotherapy, chemotherapy and radical surgery which can cause premature menopause and infertility.

If the ovary is removed and frozen before the treatment begins and transplanted afterwards patients may still be able to use their own eggs to have children.

Two babies have been born after fertility had been restored following transplants with thawed ovarian tissue but Arav said it was a delicate procedure and severe bleeding could occur.

Earlier attempts at transplanting whole ovaries, which had not been frozen or thawed, in women had failed.

"There is a lot of research still to be done, but we hope that it will not take more than a few years for this to become a practicable option for women, such as young cancer patients, who would otherwise be left infertile after their treatment," said Yehudit Natham, of the biotech company Core Dynamics which funded the project.

The Israeli team, who reported their achievement in the journal Human Reproduction, tested the technique on sheep because their ovaries are similar to those in humans.

They removed the right ovary from the animals, froze and thawed them and replaced the organs in the sheep two weeks later. Eggs released from the ovaries were collected from two of the sheep and later developed into eight-cell embryos.

The scientists have also frozen the ovary of an endangered sub-species of the gazelle which they plan to transplant into a surrogate mother.