The effects of various synthetic polymers on oxidative stress in ovarian tissue subjected to cryoprotectant exposure and vitrification

To enhance the post-thaw viability of ovarian tissue, cryopreservation methods are continually being refined. Therefore, we aimed to explore whether ovarian tissue vitrification in closed high-security tubes could be improved with ice-blocking polymers. Bovine ovarian fragments (n = 10) were exposed to varying concentrations of a vitrification solution containing glycerol and ethylene glycol (VS1 (54 % (w/v)), VS2 (57 % (w/v)), VS3 (60 % (w/v))), supplemented with synthetic polymers (Super cool X-1000, Super cool Z-1000, and polyvinylpyrrolidone (PVP K-12)), with (VVS1, VVS2, VVS3) or without subsequent vitrification. In the second phase (n = 6), we explored the individual effects of each polymer. A lower percentage of abnormal follicles was observed in the fresh and VVS2 groups compared to other groups. Additionally, the fresh, VVS2, and VVS3 groups exhibited less tissue fibrosis than the VVS1 group. Higher tissue viability, total antioxidant levels, and lower reactive oxygen species (ROS) levels were observed in the fresh and VVS2 groups. In groups exposed to CPA, there was an increase in ROS and a decrease in antioxidants compared to the fresh group. We also observed higher tissue viability and improved follicular morphology in the vitrification solution supplemented with Super cool X-1000, either alone or in combination with PVP K-12 and Super cool Z-1000. Lower ROS were found in the group supplemented with PVP K-12, either alone or in combination with Super cool X-1000 and Super cool Z-1000. In conclusion, combining a closed vitrification system with an optimized concentration of cryoprotective agents and synthetic polymers improved bovine ovarian tissue vitrification outcomes including post thaw viability and follicular morphology when compared to standard cryopreservation protocols.