PF779 VIABILITY OF HEMATOPOETIC STEM CELLS FOLLOWING STORAGE AT −80OC WITH 5% DIMETHYLSULFOXIDE AND HEMATOLOGIC RECOVERY IN TRANSPLANTED MYELOMA PATIENTS

Abstract

Background:Dimethylsulfoxide (DMSO) is a major intracellular cryoprotectant, used for cryopreservation of stem cells. It is toxic to both cells and patients at temperatures above 0oC. Reduction of this effect is achieved by either washing of cells after thawing or by reduction of DMSO during freezing and storage. The latter requires addition of extracellular cryoprotectants to the freezing media.Aims:We assessed the effect of low DMSO concentration and different hematocrits of the frozen cells on cell viability and hematologic recovery in patients, transplanted for multiple myeloma.Methods:Cells were non‐programmed frozen and stored at −80oC in a cryoprotectant solution achieving final concentrations of 5% DMSO, 3.6% of hydroxyethyl starch (HES, Weight average molecular weight 450 000 Da) and 3% of human serum albumin. The cell concentration in the frozen product for the first 77 patients (84 transplantations) varied between 100x106 and 250x106 cells/ml. In an attempt to reduce the amount of DMSO infused, for the rest of the patients (n = 172; 192 transplantations) we further decreased the volume of the freezing suspension by removal of the entire plasma.The average age of the transplanted patients was 55 (35 ‐ 71). The cells were bedside thawed at 37oC water bath. The average cell dose was 2,95x106/kg (1,3 – 9,2x106/kg).Results:Viability of the stem cells following thawing assessed by trypan blue exclusion was 95,34% (70–99). The hematocrit of the frozen cells had no effect on cell viability (94,80%(low) vs 95,52%(high)). The major complaints, if any, during stem cell infusion were coughing and an increase in nausea and vomiting induced by the prior conditioning.The average time for hematological recovery was 11,66 days (between 9 and 19) for the neutrophils, and 12,17 (between 9 and 20) days for the platelets. There was no significant difference in viability and hematologic recovery (11,86 and 12,60 vs 11,59 and 12,02) between patients receiving cells frozen with low or high hematocrit.Summary/Conclusion:Dimethylsulfoxide, despite its cryoprotective properties, is toxic for stem cells at temperatures above zero C and induces many side effects (cardiac, neurologic, respiratory, etc.) in the patients. To reduce those side effects we use lower DMSO concentration, high hematocrit resulting in lower volume of the frozen cell suspension, thus reducing the final quantity of DMSO to be infused to the patients. This does not affect the cell viability or the hematologic recovery of patients after transplantation. Our easily performed method for unprogrammed freezing of stem cells with final DMSO concentration 5% at −80oC is safe, well tolerated, and provides cryopreservation, which allows high viability and stable cell engraftment, while reducing the undesired side effects of DMSO.