Long-term storage at -80°C of hematopoietic progenitor cells with 5-percent dimethyl sulfoxide as the sole cryoprotectant

BACKGROUND: Hematopoietic progenitor cells (HPCs) can be cryopreserved and stored below -120 degrees C in liquid nitrogen or at -80 degrees C in mechanical freezers. STUDY DESIGN AND METHODS:The feasibility of long-term storage of HPCs at -80 degrees C was investigated. The studies included a comparison of 5- and 10-percent dimethyl sulfoxide (DMSO) as cryoprotectant at various lengths of storage time. Mononuclear cell (MNC) recovery and viability and colony-forming unit-granulocyte-macrophage (CFU-GM) and burst-forming unit-erythroid (BFU-E) recovery assays were performed. The peripheral blood HPCs of 24 consecutive patients included in the program of autologous transplantation were studied. RESULTS: The MNC viability decreased progressively with the length of time from cryopreservation, reaching 32 percent after 31 months of storage. The recovery rates of CFU-GM and BFU-E also decreased progressively with the duration of frozen storage, to 50 and 43.5 percent, respectively, after 12 months and to 0 percent (both) after 24 months. At 6 months of storage, MNC viability was 80 percent, and CFU-GM and BFU-E recovery was 63.5 and 80.5 percent, respectively. There were no differences between MNCs cryopreserved with 5- or 10-percent DMSO in terms of cell viability. There were no differences between CFU-GM recovery or BFU-E recovery from HPCs cryopreserved in 5- or 10-percent DMSO. Patients given HPCs stored in these conditions for periods ranging between 123 and 202 days showed a complete and rapid hematologic recovery. CONCLUSION: HPCs can be cryopreserved at -80 degrees C with 5-percent DMSO and stored at -80 degrees C no longer than 6 months. A 5-percent DMSO concentration is comparable to a with 10-percent concentration in terms of recovery and MNC viability.