Freezing of human ovarian tissue--not the oocytes but the granulosa is the problem.

The freezing of human ovarian tissue may be the key for restoring fertility after systemic therapy of cancer. In contrast to others we investigated the survival rate of whole follicles, and had a special look at the granulosa cells. Ovarian tissue was collected laparoscopically (n = 10) and divided into equal parts for freezing (n = 1570) or as control (n = 1660). The cryopreservation was done slowly, or as a ultrarapid freezing. After thawing the number of follicles, oocytes and granulosa cells surviving was counted and corrected for equal volumina of the samples. While 84.5% of the oocytes survived freezing, only 40.4% of the follicles were intact after thawing. The data show that the procedure damaged follicles, which mainly affected the granulosa cells. As the intactness of follicles may play a critical role for the maturation of the oocytes after thawing the protocols should be optimised to meet the needs of oocytes and granulosa cells.