Cryopreservation of precision-cut tissue slices for application in drug metabolism research

Cryopreservation of tissue slices greatly facilitates their use in drug metabolism research, leading to efficient use of human organ material and a decrease of laboratory animal use. In the present review, various mechanisms of cryopreservation such as equilibrium slow freezing, rapid freezing and vitrification, and their application to cryopreservation of tissue slices are discussed as well as the viability parameters often used to evaluate the success of cryopreservation. Equilibrium freezing prevents intracellular ice formation by inducing cellular dehydration, but (large) ice crystals are still formed in the interstitial space of the slices. Upon rapid freezing, (small) intra- and extracellular ice crystals are formed which slices from some tissues can resist. Vitrification prevents the formation of both intra- and extracellular ice crystals while an amorphous glass is formed of the slice liquid constituents. To vitrify, however, high molarity solutions of cryoprotectants are required that may be toxic to the slices. The use of mixtures of high molarity of cryoprotectants overcomes this problem. We conclude that vitrification is the approach that most likely will lead to the development of universal cryopreservation methods for tissue slices of various organs from various animal species. In the future this may lead to the formation of a tissue slice bank from which slices can be derived at any desirable time point for in vitro experimentation.