It may be possible to remove whole ovaries, freeze them, and later thaw and transplant them, according to Israeli scientists.

They did exactly that in tests on sheep. The thawed, transplanted ovaries worked for more than three years after the procedure, the scientists write in Human Reproduction.

It’s not known if the same strategy will work in people. If it does, it could help preserve fertility in women at risk for premature ovarian failure for reasons including cancer treatment, write Amir Arav, DVM, PhD, and colleagues.

Arav is a senior scientist at the Institute of Animal Science, which is part of the Agricultural Research Organization of Israel.

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Ovary Experiment

Arav and colleagues removed ovaries from eight sheep. One whole ovary from each sheep was frozen, along with blood vessels.

Over the next three to 14 days, the sheep were prepped to get their frozen ovary back. The ovaries were thawed in a special solution and transplanted back.

Eggs from the transplanted ovaries were removed one to four months after transplantation.

In lab tests, the researchers were able to show that eggs from the transplanted sheep ovaries divided and developed normally.

According to a news release, the researchers didn’t try to fertilize the eggs with sheep sperm, since the sperm’s quality could have affected the results.

“This way, we knew that the development of the embryo depended solely on the quality of the [egg],” says Arav in the news release.

Tests of hormone production by the transplanted ovary, two and three years later, showed that the ovaries were working.

Sheep ovaries were chosen because they’re similar to human ovaries, states the news release.

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More Work Ahead

“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,” says Yehudit Nathan in the news release.

Nathan is a product manager for Core Dynamics, the biotech company that funded the study, according to the news release.

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Preserving Women’s Fertility

Ovarian tissue transplants have been in the news in recent months, but none involved whole, frozen ovaries.

In June, a 24-year-old woman who had been infertile for a decade naturally conceived and gave birth to a baby after getting a graft of her identical twin sister’s ovarian tissue.

In November 2004, researchers in the Netherlands reported that they preserved a 29-year-old cervical cancer patient’s fertility by removing one of her ovaries before cancer treatment and putting the ovary in the woman’s arm later on.

In March 2004, a study in The Lancet showed that an egg from human ovarian tissue was successfully fertilized in a lab test.

But the process is still experimental. In an editorial in The Lancet’s March 2004 edition, Johan Smitz of the Centre for Reproductive Medicine in Brussels, Belgium, noted safety concerns and questions about freezing ovarian tissue.

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By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Arav, A. Human Reproduction, Sept. 15, 2005. News release, MW Communications. WebMD Medical News: “Woman Gives Birth After Ovarian Transplant.” WebMD Medical News: “Woman Has Successful Ovary Transplant to Arm.” WebMD Medical News: “Ovarian Tissue Banking May Restore Fertility.”