Novel direct cover vitrification for cryopreservation of ovarian tissues increases follicle viability and pregnancy capability in mice.
ABSTRACT Cryopreservation of ovarian tissue is valuable for fertility preservation. We develop an innovative vitrification method using less concentrated cryoprotectants and direct application of liquid nitrogen to the ovarian tissue (direct cover vitrification, DCV) to improve its efficiency.
Ovaries of 5- to 6-week-old C57BL/6J mice were randomly allocated to four groups: DCV, conventional vitrification, slow-freezing and non-frozen controls. Experiment 1: observing the follicle morphology. Experiment 2: assessing viability. Experiment 3: investigating the ultrastructure. Experiment 4: examining the follicle number after grafting. Experiment 5: ascertaining pregnancy potential by allogeneic orthotopic transplantation.
The percentages of morphologically normal or viable follicles from DCV were significantly greater than those achieved from conventional vitrification and slow freezing (P < 0.01). The ultrastructure of primordial follicles from DCV appeared better than that achieved from conventional vitrification and slow freezing. After grafting, the follicle number from DCV was greater than conventional vitrification (P = 0.001) and slow freezing (P = 0.021). The pregnancy rate of DCV was higher than conventional vitrification (P < 0.01). The litter size from DCV was comparable with that from non-frozen graft and was significantly greater than that achieved from conventional vitrification and slow freezing (P < 0.01).
DCV is highly efficient for cryopreservation of ovarian tissue. Using less concentrated cryoprotectants appears to reduce toxicity. Direct cover by liquid nitrogen maximizes cooling that could facilitate vitrification and prevent ice crystal injury.
Article: Cryopreservation of the Ovary[show abstract] [hide abstract]
ABSTRACT: The removal, cryopreservation, and subsequent reimplantation of ovaries would make it possible to treat a young cancer patient and improve her quality of life by preserving her fertility. The current technology requires cutting the ovary into pieces before freezing and does not support preservation of the whole ovary. The ovary has a complex endocrinologic function. It is composed of cells of different form and character and contains oocytes at various stages of development. Successful cryopreservation, transplantation, and functional rehabilitation of the whole ovary would have broad significance, not only for ovaries but also for other organs such as the liver, kidney, and heart. Ovarian cryopreservation technology would lead the way to the establishment of a biological bank for frozen internal organs.Journal of Mammalian Ova Research 12/2010;