Cryopreservation of mammalian embryos and oocytes: recent advances.

The cryopreservation of embryos of most domestic species has become a routine procedure in embryo transfer, and recently, advances have been made in the cold storage of mammalian oocytes. The ability to sustain viable oocytes and embryos from mammalian species at low temperature for prolonged periods of time has important implications to basic and applied biotechnology. Recent advances in the study of physico-chemical behaviour of different cryoprotectants, use of various macromolecule additives in cryoprotective solutions and isolation and use of proteins of plant and animal origin with antifreeze activity offers many new options for cryopreservation of oocytes and embryos of animal and human origin. At the same time rapidly developing methods of oocyte/embryo manipulation such as in vitro embryo production, embryo splitting, embryo biopsying for gene and sex determination, embryo cloning and the isolation of individual blastomers, create new challenges in cryopreservation. Very recent advances in the cryopreservation of mammalian oocytes, in vivo- and in vitro-derived embryos, and micromanipulated embryos are reviewed in this manuscript.