The use of an open-freezing system with self-seeding for cryopreservation of mouse ovarian tissue

Chemoradiotherapy in young women with cancer has substantially improved life expectancy in these patients, but these treatments often cause infertility. One method of preserving fertility is to cryopreserve ovarian tissue. In this study, an automatic open-vessel freezing system with self-seeding was tested for cryopreservation of murine ovarian tissue; the mouse is a species widely used in human and veterinary medical research. The freezing system concerned, is used for cryopreservation of oocytes and embryos in Europe. Twenty severe combined immunodeficiency (SCID) mice were ovariectomized. The ovarian tissue was either directly transplanted heterotopically into the neck muscle (group 1, n = 6) or cryopreserved after equilibration with 1.5 M dimethylsulphoxide and propanediol. After thawing, the tissue was transplanted in SCID mice (group 2, n = 6). Before and after thawing, a part of the ovarian tissue was examined with the LIVE/DEAD fluorescent viability staining. The count of follicles revealed intact (fresh 24.1%/thawed 21.7%), impaired (fresh 35.1%/thawed 35.4%), and dead follicles (fresh 40.8%/thawed 42.9%). The healthy follicular loss because of the cryopreservation was 10.0%. All recipient mice were killed after 3 weeks. Transplanted ovarian tissue was found macroscopically in all mice. Histological examination showed several growing follicles in all developmental phases in both groups of SCID mice [group 1 (fresh grafts): 315 +/- 76.3 (mean +/- SD); group 2 (cryopreserved grafts): 237 +/- 63.4]. These results demonstrate that the use of an open-freezing system allows the survival of cryopreserved mouse ovarian tissue.