Cryopreservation Principles

Cryopreservation of cells has been increasingly successful over the past 50 years. The collective works of Lovelock, Meryman, Mazur, Polge, Smith, Farrant, Willadsen, Luyet, Fahy, Rall, and Leibo have laid the groundwork for successful gamete and embryo storage. Since the cell is comprised mostly of water, successful cryopreservation by modern strategies requires the cell to be partially dehydrated, loaded with a cryoprotectant, and cooled either slowly or rapidly until a temperature at which the remaining liquid solidifies. The cell can be rescued from its frozen/vitrified state by warming and rehydration. Problems of intracellular ice formation, solution effects, and other issues can arise and have detrimental consequences. Phase diagrams help visualize what occurs when a cell is cooled, and calculations can be made to theoretically optimize cryopreservation success. The basic principles apply to cellular cryopreservation as a whole but are more focused here towards the storage of mammalian gametes and embryos.