Ovarian tissue cryopreservation for patients with premature ovary insufficiency caused by cancer treatment: optimal protocol

Objective: Premature ovary insufficiency is frequent after chemotherapy/radiotherapy in cancer patients. Ovarian tissue (OT) cryopreservation and later retransplantation, the routine method in Europe, has recently been implemented at the first center in China. We investigated the protective effect of the antioxidant N-acetyl-l-cysteine (NAC) during the decisive freezing–thawing steps.Methods: Fifteen OT samples were obtained from each of 13 cancer patients prospectively and randomly assigned to a control group and four groups with different NAC concentrations (Group 1, 0 mM NAC; Group 2, 0.5 mM NAC; Group 3, 1 mM NAC; Group 4, 5 mM NAC; Group 5, 25 mM NAC). After thawing, the follicle viability, DNA fragmentation, levels of reactive oxygen species (ROS), and total antioxidant capacity (TAC) were evaluated.Results: OT cryopreserved and thawed with 25 mM NAC (Group 5) has the lowest proportion of apoptotic stroma cells, but the worst follicle viability. The other four groups show similar anti-apoptosis and good follicle viability. Group 4 presented the lowest ROS and highest TAC levels.Conclusions: OT cryopreserved and thawed in medium supplemented with 5 mM NAC shows the highest antioxidant and lowest ROS capability, good apoptotic parameters, and follicle viability. Our results need to be confirmed in larger patient cohorts prior to being accepted as a standard protocol.