The first human embryo to be created after an ovarian tissue transplant may signal hope for hundreds of thousands of women made infertile by cancer treatment.
Researchers have been attempting to transplant ovarian tissue in humans for many years but this is the first time they have obtained good quality eggs from a transplant, as well as a viable embryo.
Kutluk Oktay, at Cornell University in New York, and colleagues took a strip of ovarian tissue from a 30-year-old woman with breast cancer before chemotherapy made her infertile. They froze the tissue and six years later transplanted it beneath the skin of her abdomen.
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After three months, the tissue started functioning normally and produced eggs. Those that were viable were fertilised in the test tube, resulting in one promising embryo. The ball of four cells was implanted into the woman, but she did not become pregnant.
Deep freeze
鈥淭his research represents a potentially significant reproductive advancement in two respects: first, women can preserve their fertility by freezing their ovarian tissue, and second, pregnancy may be possible even after the tissue remains frozen for a long time,鈥� says Oktay.
He told 快猫短视频 the method might also help children with cancer, offering hope to girls who are too young to have IVF before undergoing cancer treatment.
The American Society for Reproductive Medicine welcomed the research as an 鈥渋mportant advance鈥�. Johan Smitz, research director of follicle biology at the University Hospital of the Vrije Universiteit, Brussels, Belgium agrees: 鈥淭his is a step forward. For a lot of cancer patients this is good news.鈥�
Smitz adds that centres all over the world have been storing ovarian tissue for women undergoing cancer treatment, but until now the only evidence that such transplantation could work came from experiments on animals.
Early stage
Oktay and colleagues have transplanted human ovarian tissue before, but the primordial follicles 鈥� which contain the undeveloped egg 鈥� had been at a very early stage. This means that the eggs harvested had not been sufficiently developed for in-vitro fertilisation (IVF).
However, improvements to the way in which the eggs are harvested enabled the team to obtain 20 eggs in their latest attempt, eight of which were suitable for IVF.
Two of these were fertilised by intracytoplasmic sperm injection (ICSI). One embryo was abnormal, but the other 鈥済ave a beautiful four-cell embryo ready to implant鈥�, says Smitz. Oktay鈥檚 team is now trying to achieve a pregnancy from an ovarian transplant, which he suggests will happen in the next year or two.
The fact that the woman did not fall pregnant this time is not unusual, Smitz told 快猫短视频, as the chances of a four-cell embryo implanting after routine IVF is only one in 10.
But although promising, transplanting ovarian tissue could also pose risks, Smitz cautions: 鈥淲e have to be very careful that by replacing this tissue back into the body of cured cancer patients, we also don鈥檛 reintroduce cancer cells.鈥�
Preliminary work in mice and in-vitro has shown that re-implanting ovarian tissue could be dangerous for certain cancers such as leukaemia. But other cancers such as Hodgkin鈥檚 appear not to pose a risk.
Journal reference: The Lancet (vol 363, p 837)