Directional freezing of reproductive cells and organs

Directional freezing is based on a simple thermodynamic principle where ice crystals are precisely controlled through the sample by regulating the velocity of the sample movement through the predetermined temperature gradient. Directional freezing permits a precise and uniform cooling rate in both small and large volume samples. Directional freezing was used for slow and rapid freezing, as well as for vitrification of oocytes and embryos using the minimum drop size technique. Sperm samples from a wide range of domestic and wild animals were successfully cryopreserved using the directional freezing method. The method enabled, for the first time, successful freezing of a whole ovary and freeze-drying of mammalian cells followed by thawing and transplantation and rehydration, respectively.