Long-term hematologic reconstitution and clinical evaluation of autologous peripheral blood stem cell transplantation after cryopreservation of cells with 5% and 10% dimethylsulfoxide at –80oC in a mechanical freezer

Current protocols for hematopoietic stem cell (HSC) cryopreservation are usually based on the use of 10% dimethylsulfoxide (DMSO) as an intracellular cryoprotectant with or without hydroxyethylstarch (HES) as an extracellular cryoprotectant. The toxic effects related to DMSO infusion are generally dose-related and while they are usually mild, they can become severe. HES is a relatively non-toxic drug but it is related with long-lasting pruritus and osmotic nephrotoxicity. Cryopreservation protocols usually involve ratecontrolled freezing followed by the storage of the HSC in either the liquid or vapor phase of liquid nitrogen. These procedures are time consuming and require expensive computerassisted devices. Ten years ago we described a simplified –80oC HSC cryopreservation protocol that did not depend on rate-controlled freezing. This protocol involved storage in the same mechanical freezer in solutions containing 5% or 10% DMSO as the sole cryoprotectant without HES. Most studies seem to indicate that this simplified procedure is associated with a reduction in infusion toxicity and lower costs, with a similar hematopoietic reconstitution and clinical outcome to more standard protocols. However, there is little data regarding the long-term hematologic recovery and clinical course when such protocols are used.