Liquid Storage of Peripheral Blood Stem Cell Products: Effects of Time and Temperature on Product Quality

Unrelated donor peripheral blood stem cell (PBSC) products often require transport to distant locations, which may take up to 72 hours. Temperature is an important variable that can be controlled during PBSC storage or transport; therefore, we studied the impact of temperature on prolonged storage of clinical-grade, mobilized PBSC products. PBSC products were collected by apheresis from 3 granulocyte colony-stimulating factor-mobilized donors, split into 2 PVC blood bags of equal volume, and stored at room temperature (RT) (18°C to 25 ºC) or 4 °C (2°C to 8 ºC) for 96 hours. Samples were obtained at 24-hour intervals for pH, cell counts, flow cytometry phenotyping and viability (7AAD), and hematopoietic colony-forming units (CFU). Starting PBSC products contained 52, 65, and 38 × 10⁹ total nucleated cells (TNCs), with cell concentrations of 125, 263, and 94.6 × 10⁶ TNCs/mL, respectively. Product pH dropped during storage, with significantly lower values for RT stored products than for 4 ºC stored products, and was greatest in the product with the highest TNC count. The percent recovery of viable CD34⁺ progenitor cells, CD3⁺ T cells, CD4⁺ T helper cells, CD8⁺ cytotoxic T cells, CD19⁺ B cells, CD15⁺ granulocytes, CD14⁺ monocytes, and CD16⁺/56⁺ natural killer (NK) cells all decreased over 96 hours but decreased more dramatically in the RT group. Cell recovery differences were statistically significant at most time points for all cell populations except CD15⁺ granulocytes. For CD34⁺ cells stored at 4 °C, mean recovery from prestorage values were 97 ± 3% at 24 hours, 87 ± 4% at 48 hours, 88 ± 10% at 72 hours, and 78 ± 1% at 96 hours, compared to RT product values of 45 ± 11%, 19 ± 19%, 2 ± 2%, and 0 ± 0%, respectively. CFUs were well preserved through 96 hours at 4 ºC but not at RT. During PBSC storage, pH and content of viable CD34⁺ cells, T cells, B cells, monocytes, NK cells, and CFU all declined. However, at 4 ºC, viable cell recoveries are relatively well preserved, even at 72 hours, whereas RT storage resulted in rapid product deterioration. PBSC products requiring prolonged liquid storage or transport before cryopreservation or infusion should be maintained at 4 ºC.