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

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Abstract
BACKGROUND: Hematopoietic progenitor cells (HPCs) can be cryopreserved and stored below −120°C in liquid nitrogen or at −80°C in mechanical freezers. STUDY DESIGN AND METHODS: The feasibility of long-term storage of HPCs at −80°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-granulocytemacrophage (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°C with 5-percent DMSO and stored at −80°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.