Viability and engraftment of hematopoietic progenitor cells after long-term cryopreservation: Effect of diagnosis and percentage dimethyl sulfoxide concentration

Background aims. We carried out a retrospective analysis of viability by diagnosis and dimethyl sulfoxide (DMSO) concentration in patients who had undergone autologous transplants using hematopoietic progenitor cells (HPC) after long-term storage (up to 17.8 years). Methods. Viability was tested using flow cytometry for HPC that were harvested and preserved using a controlled rate freezer and 5% or 10% DMSO with human serum albumin, then stored in liquid nitrogen. Data from 262 samples were analyzed (249 myeloma patients and 13 other diagnoses): 100 consecutively thawed samples with a storage time of <1 year (all 10% DMSO), 50 consecutive samples stored for 14.9 years (10% DMSO), 50 samples stored for 59 years (5% DMSO) and all samples stored and used for transplant after >9 years (60 samples, 5% DMSO; two samples, 10% DMSO). Results. No statistically significant difference in viability between the 5% DMSO and 10% DMSO groups was observed (P 0.08), so the 14.9 years and 59 years were combined and the three groups (<1 year, 19 years and >9 years) were compared using an anova test. There was no difference in viability based on cryostorage period (P 0.23) or between myeloma and other diagnoses (P 0.45). No difference was seen in time to White blood cell (WBC) engraftment (P 0.10) or to platelet engraftment between groups (P 0.52). Conclusions. These data suggest that long-term storage in 5% DMSO and human serum albumin is safe.