Cryobiology: Slow Freezing and Vitrification of Embryos

Abstract To cryopreserve cells alive without decreasing survival with the duration of storage, they must be preserved at temperatures below the glass transition temperature, which is around –130°C. In practice, liquid nitrogen (–196°C) is used for maintaining such a temperature. To date, various methods for embryo cryopreservation have been developed, and embryos of more than 20 mammalian species have been successfully cryopreserved (1). Cryopreservation, coupled with embryo transfer, is used to preserve genetic variants in laboratory animals (mainly mice), for breeding and reproduction in farm animals (mainly cattle), and for treatment of infertility in humans. Furthermore, embryo cryopreservation is expected to be used for the conservation of wild species. Here we give a brief outline of embryo cryobiology and describe some reliable protocols for embryo cryopreservation.