Oocyte and embryo cryopreservation – state of art and recent developments in domestic animals

Abstract

During the past few decades, significant progress in cryopreservation of mammalian oocytes and embryos has been observed. Transfer of cryopreserved embryos or oocytes resulted in live offspring in at least 25 species. So far, two major methods have been used for oocyte and embryo cryopreservation: conventional slow-rate freezing and vitrification. This review summarizes the progress in cryopreservation of mammalian oocytes and embryos that has been achieved by modifying oocyte/embryo susceptibility to cryopreservation or vitrification technology through such techniques as solid-surface vitrification, cryoloop, microdrop, cryotop, electron microscopy grids, nylon mesh, open pulled straw method or removal of lipids, addition of antifreeze protein or cytoskeleton- stabilizing agents, cholesterol or liposomes, centrifugation prior to cryopreservation or application of high hydrostatic pressure. In conclusion, the vitrification method opened new perspectives in cryopreservation of embryos and oocytes, both for in vitro fertilized and somatic nuclear transfer. Authors believe that new cryopreservation procedures which modify the susceptibility of oocytes and embryos to cryopreservation will gain importance as a major tool in mammalian gamete and embryo cryopreservation.