The cryopreservation of composite tissues: Principles and recent advancement on cryopreservation of different type of tissues.

Cryopreservation of human cells and tissue has generated great interest in the scientific community since 1949, when the cryoprotective activity of glycerol was discovered. Nowadays, it is possible to reach the optimal conditions for the cryopreservation of a homogeneous cell population or a one cell-layer tissue with the preservation of a high pourcentage of the initial cells. Success is attained when there is a high recovery rate of cell structures and tissue components after thawing. It is more delicate to obtain cryopreservation of composite tissues and much more a whole organ. The present work deals with fundamental principles of the cryobiology of biological structures, with special attention to the transfer of liquids between intra and extracellular compartments and the initiation of the formation and aggregation of ice during freezing. The consequences of various physical and chemical reactions on biological tissue are described for different cryoprotective agents. Finally, we report a review of results on cyropreservation of various tissues, on the one hand, and various organs, on the other. We also report immunomodulation of antigenic responses to cryopreserved cells and organs.