Short-Term Storage of Mobilized Peripheral Blood Stem Cells in a Closed System Changes the Microenvironment and May Affect the Quantity of CD34⁺ and CD34⁺CD38^-CD45RA^-CD90⁺ Cells

Hypoxic conditions preserve the multipotency and self-renewing capacity of murine bone marrow and human cord blood stem cells. Blood samples stored in sealed blood gas tubes become hypoxic as leukocytes metabolize and consume oxygen. Taken together, these observations suggest that peripheral blood stem cell (PBSC) samples stored under airtight conditions become hypoxic, and that the stem cells contained may undergo qualitative or quantitative changes. This study aimed to determine the effect of storage for 8 hours in a sealed system on PBSC samples. Granulocyte colony-stimulating factor-mobilized PBSC samples were collected prospectively from 9 patients with myeloma or amyloidosis prior to apheresis, followed by measurement of CO2, O-2, hydrogen ion (pH), lactate, and glucose concentrations in the blood and immunophenotyping of stem cell and multipotent progenitor cell populations before and after 8 hours of storage in sealed blood collection tubes. Blood concentrations of O-2 and glucose and pH measurements were significantly decreased, whereas concentrations of CO2 and lactate were significantly increased after storage. Significantly higher concentrations of CD34(+) cells (552 +/- 84 cells/10(6) total nucleated cells [TNCs] versus 985 +/- 143 cells/106 TNCs; P =.03), CD34(+)CD38(-) cells (98 +/- 32 cells/10(6) TNCs versus 158 +/- 52 cells/10(6) TNCs; P =.03), CD34(+)CD38(+) cells (444 +/- 92 cells/10(6) TNCs versus 789 +/- 153 cells/10(6) TNCs; P =.03), and CD34(+)CD38-CD45RA-CD90(+) cells (55 +/- 17 cells/10(6) TNCs versus 89 +/- 25 cells/10(6) TNCs; P =.02) were detected after 8 hours of storage. The changes in concentrations of CD34(+)CD38(+) cells and CD34(+) cells were inversely associated with the change in glucose concentration (P =.003 and P <.001, respectively) and positively associated with the change in lactate concentration (P =.01 and P <.001, respectively) after 8 hours of airtight storage. Storage of PBSC samples in a sealed, airtight environment is associated with microenvironmental changes consistent with hypoxia and increased concentrations of immunophenotypically defined stem cells. These results may have clinical implications with regard to the collection and processing of stem cell products and warrant confirmation with functional andmechanistic studies. (c) 2022 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.