Ovarian Tissue Cryopreservation
Chemotherapy and radiation regimens often cause cancer patients to become infertile. Ovarian tissue cryopreservation may be the next big thing for these women. With this surgical technique, doctors remove small strips of ovarian tissue containing thousands of immature eggs, and freeze the tissue prior to the start of treatment.
After treatment, when a woman is ready to become pregnant, the tissue is thawed and sewn back into the ovary. The hope is that the transplanted tissue will start to function within a few months, and will begin to ovulate. One advantage to this technique over egg freezing is that it doesn’t require injections of hormones that might fuel the cancer’s growth. Plus, “When we vitrify ovarian tissue we get absolutely no egg loss at all,” says Dr. Silber, who believes this technique may also have mainstream appeal some day. “With ovarian tissue, one laparoscopy and [a woman] has 100,000 eggs in the freezer. I think ovarian tissue freezing is a better and cheaper option [than freezing eggs].”
So far, about 14 births have resulted from the technology worldwide, and most of the mothers conceived spontaneously—without the need for assisted reproduction technologies like IVF. The Oncofertility Consortium (oncofertility .northwestern.edu), a nationwide network of fertility experts, has begun making the technology available at 50 facilities, including Northwestern University Medical Center in Chicago; Montefiore Medical Center in New York City; and Duke University in Durham, North Carolina.
Advances are also being made in cryopreserving entire ovaries for women undergoing cancer treatment. Approximately 20 healthy births have occurred so far, and the prospect of freezing an ovary for a decade or more could eventually become an option for healthy women who simply want to delay reproduction for lifestyle reasons. “Imagine being 35 with the ovary of a 19-year-old,” says Dr. Silber. “Women could conceive naturally and with a better chance of success.”
Since 2004, Dr. Silber has performed fresh ovarian tissue transplants and one complete ovary transplant between nine sets of identical twins. In these pairs of twins (who share the same genes), one twin was fertile, but the other was not. The result: All of the women have conceived, and seven have had babies, with two of them delivering twins. And all nine women who received the transplants have normal menstruation and ovulation.
When Dr. Silber’s team first tried transplanting an ovary from one non-identical twin to the other in 2007, the body of the twin who received the organ rejected it. In a later attempt with another pair of non-identical twins, Dr. Silber used mild immunosuppressant drugs to prevent rejection. That organ is functioning normally, and the woman has no negative effects.
Similar challenges face doctors who seek to transplant a human uterus. The surgery has been done in animals, but has not been successfully performed in humans. Much of the work being done to perform a successful uterus transplant is taking place in countries like Saudi Arabia that prohibit gestational surrogacy. The transplants would allow women who ovulate normally but have no uterus, a damaged uterus, or uterine abnormalities to become pregnant and carry their own children.
Last fall, surgeons at Britain’s Hammersmith Hospital in London announced they had perfected a womb transplant technique in rabbits. The breakthrough, they said, was figuring out how to maintain a good blood supply to the transplanted organ. The scientists plan to try the technique in humans in 2011.
This story was originally published in the Summer 2010 issue of Conceive Magazine.
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