Background: The freezing curve currently used for the cryopreservation of peripheral blood stem cell transplants (PBSCTs) has been determined empirically. Although the use of cryopreserved PBSCTs is successful and usually leads to rapid hematopoietic recovery, the freeze-thawing process is known to induce a significant degree of cell death. Furthermore, the infusion of dimethyl sulfoxide (DMSO), used to protect the cells against damage induced by freezing, can cause morbidity. Therefore, optimizing the current cryopreservation protocol (with 10% DMSO and a slow linear cooling curve) with theoretically optimized freezing curves and a lower DMSO concentration might improve the recovery after transplantation.
Study design and methods: A theoretical model was used to predict optimal freezing curves for 5 and 10 percent DMSO. CD34+-selected and -unselected PBSCs were cryopreserved with the current or the new freezing curves. Postthaw quality was evaluated by cell viability, colony formation, and megakaryocyte outgrowth.
Results: With 10 percent DMSO, the use of the predicted optimal freezing curve resulted in increased postthaw viability of CD34+ cells, colony formation, and megakaryocyte outgrowth. Lowering the DMSO concentration to 5 percent resulted in improved postthaw viability and functionality, which was not further improved by use of the theoretically optimized freezing curve.
Conclusions: Our results indicate that the current cryopreservation method for PBSCTs can be improved by either lowering the DMSO concentration to 5 percent or by using the theoretically optimized freezing curve. Infusion of less DMSO and more viable cells might improve the outcome of PBSCT.