Evaluation of a new freezing protocol containing 20% dimethyl sulphoxide concentration to cryopreserve human ovarian tissue

Could a modification in the ovarian tissue freezing protocol improve follicle survival after cryopreservation and xenotransplantation? Ovarian tissue was used from 13 adult patients, frozen either with our original protocol, or a modified version involving a higher concentration of dimethyl sulphoxide (DMSO), larger volume of cryopreservation solution and lower seeding temperature. After thawing, the ovarian fragments were xenotransplanted to six mice with severe combined immunodeficiency (SCID) for 3 weeks. The proportion of primordial follicles decreased, and the proportion of growing follicles increased significantly (all P < 0.01) after cryopreservation and xenografting compared with fresh controls for both protocols. Follicle density, development, ultrastructure and function were similar between treatments. This study showed that, although the higher DMSO concentration did not improve survival of preantral follicles, it did not seem to induce any major toxicity in the follicle population either.