Principles of Cell and Tissue Cryopreservation

Cryopreservation is the use of low temperatures to stabilize biological materials over long periods of time. The preserved material may be living or nonliving according to the intended use. A range of techniques is available but most involve the addition and removal of cryoprotectants (CPAs); the removal and restoration of heat (cooling and warming); and appropriate conditions of storage. High concentrations of CPAs are necessary and they work by raising the total osmolality of the system thereby reducing the temperature at which ice forms and also reducing the amount of ice that forms as cooling proceeds. Important factors controlling the formation of ice crystals are discussed and the importance of control of cooling rate is emphasized. Conventional cryopreservation methods, vitrification and freeze drying are all discussed. We use illustrations from three specific fields of application: the cryopreservation of tissues – arteries, corneas, and cartilage; the cryopreservation of tissue engineered or decellularized constructs; and the use of cryopreservation in assisted reproductive therapy.