Hollow fiber vitrification allows cryopreservation of embryos with compromised cryotolerance

Purpose: This study aims to demonstrate vitrification methods that provide reliable cryopreservation for embryos with compromised cryotolerance. Methods: Two-cell stage mouse embryos and in vitro produced porcine embryos were vitrified using the hollow fiber vitrification (HFV) and Cryotop (CT) methods. The performance of these two methods was compared by the viability of the vitrified-rewarmed embryos. Results: Regardless of the method used, 100% of the mouse 2-cell embryos developed successfully after vitrification-rewarming into the blastocyst stage, whereas vitrification tests using porcine morulae with the HFV method produced significantly better results. The developmental rates of vitrified porcine morula into the blastocyst stage, as well as blastocyst cell number, were 90.3% and 112.3 +/- 6.9 in the HFV group compared with 63.4% and 89.5 +/- 8.1 in the CT group (P < .05). Vitrification tests using 4- to 8-cell porcine embryos resulted in development into the blastocyst stage (45.5%) in the HFV group alone, demonstrating its better efficacy. The HFV method did not impair embryo viability, even after spontaneous rewarming at room temperature for vitrified embryos, which is generally considered a contraindication. Conclusion: Vitrification test using embryos with compromised cryotolerance allows for more precise determining of effective cryopreservation methods and devices.