New Ovarian Tissue Freezing Technique May Extend Fertility

Advancement in the techniques used for ovarian transplants gives new fertility hope to cancer survivors and career women. A new ultra-fast ovarian tissue freezing technique that may extend fertility in cancer survivors and career women was outlined by Dr. Sherman Silber at the 25th annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) on June 29, 2009. Dr. Sherman Sibler is the Director of the St. Louis Infertility Center in St. Louis, Missouri.

Infertility Concerns For Cancer Survivors
The toxic drugs used in chemotherapy often leave cancer survivors infertile. One infertility solution for young female cancer patients is to have ovarian transplants using their own ovaries. The procedure involves removing one or both ovaries, freezing the ovarian tissue, and then transplanting it back into the patient once the cancer treatment has been successful.

In the past, ovarian transplants have had a low success rate, with only a few resulting in natural pregnancy. One reason for this is the damage that occurs to the oocytes (immature ovum, or eggs) within the ovary due to the formation of ice crystals during the controlled rate slow-freezing process. A second major reason is the amount of time it takes the body to re-establish a full blood supply to the ovarian tissue after transplant.

Referring to the difficulty of re-establishing blood flow during his own discussion on advancements in ovarian transplant surgical procedures, Dr. Pascal Piver, who manages the IVF (in vitro fertilization) Centre at Limoges University Hospital, Limoges, France, explained, "In order for a woman to become pregnant, the ovaries need to be responsive to the action of hormones that cause them to release eggs each month. If the blood supply to the ovaries is insufficient, this will not happen, even though the transplant may look as though it has been successful."

New Ovarian Tissue Freezing Technique
The new ultra-fast ovarian tissue freezing technique, called vitrification, addresses the concern of oocyte damage. Using a highly concentrated mixture of antifreeze (DMSO and ethylene glycol) and rapid temperature drop, the ovarian tissue instantly freezes into a solid with no ice crystal formation.

Dr. Silber and his colleagues conducted a study that followed 15 female cancer patients and nine identical twin sisters. Ovarian tissue from the female cancer patients was frozen using either the slow-freezing process or rapid cooling vitrification. The twin sisters experienced fresh ovary transplantation. The medical team used standard viability testing with fluorescent microscopy to determine the preservation or loss of oocytes.

"We found that 91.9 percent of the fresh oocytes were viable compared with 88.9 percent of those vitrified. However, slow freezing resulted in a 56 percent loss of viability," said Dr. Silber.

The study further showed no difference between fresh ovarian tissue and ultra-fast frozen ovarian tissue in terms of ovulatory menstrual cycling and pregnancy after transplantation. Ovarian function was restored for more than four years in five of the seven cases followed up that long. All the patients experienced a normal ovarian cycle within four to five months after the ovarian transplant.

New Ovarian Transplant Surgical Technique For Restoring Blood Flow
Dr. Silber and his colleagues also introduced a new ovarian transplant surgical technique designed to re-establish blood flow to the transplanted ovary faster than traditional methods. The procedure uses cortical grafting, which involves transplanting very thin slices of ovarian cortical tissue. Ovarian cortical tissue refers to tissue from the outer or superficial part of the ovary.

Cortical grafting takes the place of the more delicate and time consuming microvascular surgery introduced by Dr. Silber in 2008. In microvascular surgery, time is taken to directly link the tiny blood vessels that supply blood to the ovarian tissue.

"We believed that microvascular transplant would give us a longer duration of ovarian function," said Dr. Silber, "but our current research has proved us wrong. This is not only good news for surgeons, but also for patients who will be able to undergo a simpler procedure with equally successful results."

Eight women received cortical transplants during the ovarian transplant study conducted by Dr. Silber and his medical team. Six of those women have had one or more spontaneous pregnancies, resulting in seven healthy babies.

Extended Fertility Hope for Cancer Survivors and Career Women
Discussing his hope for the use of the new ultra-fast ovarian tissue freezing and cortical grafting, Dr. Sibler said, "We are in the middle of a massive global infertility epidemic, caused by the new structure of our society where women choose not to have children until they are older. As a result, many of them become infertile because of the aging of their eggs and ovaries."

"This procedure is a solution to that social dilemma, allowing women to have children when they are older by preserving their ovaries when they are younger and transplanting them back at a later date. It can also be used to preserve the fertility of young women with cancer who are likely to be cured of their cancer, but who will become sterile as a result of the cancer treatment without such intervention," he said.