RESTORATION OF FERTILITY TO OOPHORECTOMIZED SHEEP BY OVARIAN AUTOGRAFTS STORED AT -196-DEGREES-C

Cortical slices were prepared from the right ovaries of six lambs and either grafted directly to the ovarian pedicles of origin or cooled sl owly to liquid nitrogen temperatures in medium containing dimethylsulp hoxide. Three weeks later, the contra-lateral ovary was removed and re placed with frozen-thawed slices from the same animal. Two of the anim als mated during their second oestrous cycle 3-4 months later and the remainder had at least one ovulatory cycle. The pregnancies reached fu ll-term development, one lamb being derived from an ovulation in a fre sh graft and the other from a frozen-thawed graft. None of the sheep h ad peripheral plasma concentrations of follicle stimulating hormone or luteinizing hormone consistently in the castrate range, and only one graft was devoid of follicles when the animals were slaughtered 9 mont hs after the operations. Grafts with primordial follicles always conta ined developing follicles, which occasionally attained pre-ovulatory s izes of 7 mm in diameter. A corpus albicans was present in five grafts . Since all developing follicles had degenerated 1 week after grafting in an additional ewe, the large follicles in long-term grafts had pre sumably commenced growing after the operation. There were no obvious d ifferences between fresh and frozen-thawed grafts in either appearance or weight, and all had apparently grown since implantation. Despite s ubstantial depletion of primordial follicle numbers, the results indic ated that frozen storage and replacement of a patient's own ovarian ti ssue might be practicable when fertility potential is threatened by ch emotherapy/radiotherapy.