Cryopreservation of hematopoietic progenitor cells with 5‐percent dimethyl sulfoxide at −80° C without rate‐controlled freezing

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Abstract
Background: Cryopreservation of hematopoietic cells with the rate‐controlled method is used in the majority of centers. In recent years, there has been a trend toward the simplification of the process. Study Design and Methods: A simplified method for cryopreservation was developed with 5‐percent dimethyl sulfoxide (DMSO) as the sole cryoprotectant without rate‐controlled freezing. Experiments were done with progressive concentrations of DMSO, ranging from 0 to 10 percent. With DMSO concentrations from 5‐ to 10‐percent, the best recovery and viability for hematopoietic progenitor cells were observed. Hematopoietic progenitor cells with plasma and 5‐percent DMSO were frozen and stored in a −80° C mechanical freezer. Ten patients with solid and hematologic malignancies underwent transplantation with autologous hematopoietic progenitor cells. Results: The median number of transfused mononuclear cells and CD34+ cells was 3.70 (3.1–8.2) × 108 per kg and 1.70 (0.8‐6.5) × 106 per kg, respectively. The median number of transfused colony‐forming units‐granulocyte‐macrophage was 12.45 (3.4–55.3) × 104 per kg. All patients showed rapid and sustained engraftment. The mean times to reach a neutrophil count of 0.5 × 109 per L and a platelet count of 50 × 109 per L were 11.50 ± 1.70 and 13.90 ± 3.98 days, respectively. All patients are alive and without transfusion requirements in complete remission 2 to 8 months after transplantation. Conclusion: This simplified cryopreservation technique will be useful for institutions without rate‐controlled freezing facilities. Moreover, this method diminishes the amount of DMSO infused to patients, as well as its toxicity.