Abstract
The conditions suitable for cryopreservation differ among oocytes and embryos at different stages even in the same species. Differences in cryobiological properties would affect these conditions. Permeability to water and cryoprotectants is important because it modulates major forms of cell injury from cryopreservation. In the mouse, morulae and blastocysts tolerate cryopreservation better than oocytes or early stage embryos, because they are highly permeable to water and cryoprotectants. The permeability appears to stem from a substantial expression of water/cryoprotectant-permeable channels, such as aquaporin-3. Such facilitated diffusion by channel proteins is less dependent on temperature than the process of simple diffusion via the lipid bilayer. Therefore, it is important to know the expression level and permeation properties of water/cryoprotectant channels for efficient cryopreservation of oocytes and embryos.
