Parameters of cell freezing: implications for the cryopreservation of stem cells.

The overall objective of this review has been to discuss specific parameters that may influence the ability to successfully cryopreserve stem cells and, more importantly, stem-cell-based therapies. This discussion of factors is in no way complete. Specifically, the effect of temperature and the duration of storage, sensitivities to cryopreservation of bone marrow cells from patients with specific disorders (for example, chronic myelogenous leukemia), and the postfreeze processing of cells are factors of clinical significance that, for the sake of brevity, have been omitted. As new stem-cell-based therapies (gene, stem cell transplant, or immunotherapy) become the standard of care for a wide variety of diseases, appropriate cryopreservation protocols will be necessary to increase patient access, reduce cost, and enhance the safety and effectiveness of these therapies. Appropriate protocols must include methods and reagents appropriate for human use. The cryopreservation protocols developed must also reflect the biological and physical properties of the cells that can be altered significantly by the culture process. Finally, cryopreservation studies should be performed concurrently with in vitro culture studies to reduce the overall cost and time required for the development or validation of a cryopreservation protocol.