Amsterdam, The Netherlands: Ultra-fast freezing of ovarian tissue from women who have lost their fertility as a result of cancer treatment can lead to it being used in transplants with the same success rate as fresh tissue, a researcher told the 25th annual conference of the European Society of Human Reproduction and Embryology today (Monday 29 June). Dr. Sherman Silber, Director of the St. Louis Infertility Centre, St. Louis, Missouri, USA, said that freezing tissue by the vitrification method, which avoids ice formation, meant that oocyte (egg) viability was almost identical with that seen in fresh oocytes.
Dr. Silber and colleagues used standard viability testing with fluorescent microscopy to determine the loss or preservation of oocytes in fresh and frozen ovarian tissue of 15 young women undergoing cancer treatment. They also followed up nine homozygotic twin patients after fresh ovary transplantation for the duration of ovarian function and pregnancy outcome, and tested spare tissue that had also been frozen from their ovaries at the time of transplant. Tissue was preserved either by rapid cooling vitrification or by classical slow freezing methods.
"We found that 91.9% of the fresh oocytes were viable compared with 88.9% of those vitrified. However, slow freezing resulted in a 56% loss of viability", said Dr. Silber.
Transplantation of the tissue resulted in a duration of ovarian function of more than four years in five of the seven cases followed up for that long, and all patients regained a normal ovarian cycle within four to five months after the transplant. There was no difference in terms of pregnancy or ovulatory menstrual cycling between fresh and frozen grafts. The scientists used the cortical grafting technique, where very thin slices of tissue are transplanted. This technique is much easier to perform than the delicate microvascular technique, which they described last year in an effort to prevent egg loss and to le
European Society for Human Reproduction and Embryology