Cryopreservation of Mammalian Embryos: The State of the Art

Karen Moore, Aline Quadros Bonilla


Moore K, Bonilla AQ. Cryopreservation of Mammalian Embryos: the State of the Art. ARBS Annu Rev Biomed Sci 2006;8:19-32. Embryo cryopreservation has been a useful tool for embryology since the early 1970s. It has become an essential part of assisted reproductive technologies, allowing long term storage of valuable embryos from lab animals, livestock, endangered species and humans. Initially, work was done with conventional slow cooling technologies, using cryoprotectants, such as glycerol or ethylene glycol and sucrose. More recently, however, greater advances have been made with vitrification, a procedure that bypasses ice crystal formation and places the embryo in a glass-like state. This technology is receiving greater attention as it is simpler, faster and less expensive, and provides the embryo with greater protection from cryoinjury. Successful cryopreservation requires a good understanding of the proper use of cryoprotectants, sugars, and macromolecules in order to allow the highest survival rates and ultimately pregnancy and live offspring following embryo transfer. Although this technology has been in existence for over three decades, it still yields variable results. It is clear now that success is dependent upon many variables, including embryo stage and quality, embryo species and derivation, cooling and warming rates and culture conditions, to name a few. Efforts to optimize these conditions will further enhance survival and future developmental potential of the embryo. This review will briefly summarize the current understanding of embryo cryopreservation technologies, including key areas of concern and strategies to achieve the greatest successes, as well as possible future directions for this field.

Full Text: