The reproductive community took note recently with the publication of research stating that ovarian tissue cryopreserved using a technique called vitrification, has resulted in a live human birth. Ovarian tissue cryopreservation is an experimental fertility preservation technique that involves the surgical removal of an ovary, freezing, and later thawing and transplantation when the woman is ready to have children. This technique is an option for women and girls who may not be able to undergo more established fertility preservation options but to-date only about 20 human live births have been reported using this technique.
All of the live births from frozen and thawed ovarian tissue were cryopreserved using a slow-freezing method but the recently reported birth came from tissue that was vitrified, which is a specialized fast-freezing method of cryopreservation. Vitrification has been used to significantly increase the success rates of oocyte (egg) banking over the past decade.
Ovarian tissue cryopreservation is a fertility preservation option for women and girls who may loose their fertility due to cancer treatments or disorders such as primary ovarian insufﬁciency. Patient 3 in the article, “Hippo signaling disruption and Akt stimulation of ovarian follicles for infertility treatment,” underwent removal of both ovaries at age 29 after losing her menstrual cycles at age 25. The ovarian cortices were dissected and vitrified. The article, published in the journal, Proceedings of the National Academy of Sciences of the United States of America (PNAS), describes how the tissue was processed with fragmentation into smaller cubes and treated with a set of drugs designed to stimulate the growth of ovarian follicles.
Between 40 to 80 cubes of ovarian tissue (1-2 mm2 each) were autotransplanted back to the patient via surgical placement into the oviductal serosa (the outer layer of the fallopian tube). Estradiol levels were monitored to assess when the transplanted tissue contained functional follicles, the patient was given exogenous follicle stimulating hormone (FSH) with subsequent ultrasound to monitor growth of mature antral follicles, followed by human chorionic gonadotropin (hCG) treatment. Six oocytes were retrieved and then fertilized with her husband’s sperm using intracytoplasmic sperm injection resulting in four embryos, two of which were transferred to the patient’s uterus. Thirty-seven weeks and two days later a healthy baby boy was born.
According to Mary Zelinski, PhD, and Associate Scientist in the Division of Reproductive & Developmental Sciences at Oregon National Primate Research Center of Oregon Health & Science University, “The exciting finding is that this is the first demonstration of a live human birth from vitrified (not slow-frozen) ovarian cortical tissue after transplantation, intra-cytoplasmic sperm injection of retrieved oocytes and embryo transfer.”
While this moves the field of reproductive research forward, there is still significant work needed to improve ovarian tissue cryopreservation success rates for both slow-frozen and vitrified tissue. For example, in the current study, 27 patients received similar treatments, eight had evidence of antral follicle growth and oocytes were retrieved, but only one gave birth. In order for next-generation technologies like ovarian tissue cryopreservation to become established treatments, further research is needed to improve success rates and ensure the health of children born from such treatments. To see more information about this research, watch one of the study researchers, Nao Suzuki, PhD, discuss it at the 2013 Oncofertility Conference (http://oncofertility.northwestern.edu/media/ovarian-tissue-vitrification...).