Factors affecting low temperature survival of mammalian oocytes

Abstract

Abstract The ability to cryopreserve mammalian oocytes effectively would greatly increase their availability for a broad range of reproductive technologies. Oocytes have been frozen using both equilibrium and non-equilibrium approaches originally developed for mammalian cleavage-stage embryos, but rates of fertilization and development are typically much lower than with unfrozen oocytes. Production of live young from frozen oocytes of domestic animals has not been reported. Sensitivity of cytoskeletal elements, the meiotic spindle and other components of the cortical ooplasm to chilling and cryoprotective agents may contribute to the limited success in oocyte cryopreservation. Oocytes are also subject to physical events during freezing which influence cell survival. Estimates of biophysical parameters which influence the osmotic and cryobiological responses of oocytes are becoming available and may be useful for developing freezing protocols.