Comparison of Residual Dimethyl Sulfoxide (DMSO) and Ethylene Glycol (EG) Concentration in Bovine Ovarian Tissue During Warming Steps Between Slow Freezing and Vitrification.

Background: DMSO and EG have been used as cryoprotectants for human ovarian tissue cryopreservation, but residual cryoprotectants concentration and safety have rarely been reported.

Objective: We aimed to compare residual cryoprotectants (DMSO, EG) concentration in bovine ovarian tissue during warming steps between one kind of common slow freezing method and two kinds of vitrification methods, which are usually used for cryopreservation of human ovarian tissue in Japan.

Materials And Methods: In this study, we used five bovine ovaries with an average age of 24.2 months divided into three kinds of cryopreservation methods. All ovarian cortices cut to 1 mm thickness were cryopreserved in slow freezing and two kinds of vitrification methods. Residual cryoprotectants before, during and after warming of cryopreserved ovarian cortices were measured using GC-MS and compared.

Results: Concentrations of residual cryoprotectants in the ovarian tissue just before transplantation into the body after warming were high after both vitrification methods but almost zero with the slow freezing method.

Conclusion: We are concerned about the residual cryoprotectants in ovarian tissue, and continue to study the safety of cryopreservation methods to the woman after reimplantation and her baby.