Low-oxygen and high-carbon-dioxide atmosphere improves the conservation of hematopoietic progenitors in hypothermia

BACKGROUND: During short-term storage of hematopoietic cells (HCs) at 4 degrees C a substantial decline in number and in functional capacity of progenitors occurs after 3 days. We hypothesized that physiologic O-2 and CO2 concentrations of hematopoietic tissue microenvironment (approx. 3% O-2 and approx. 6% CO2) could improve cell viability and functionality during storage at 4 degrees C. STUDY DESIGN AND METHODS: Mobilized peripheral blood (PB) CD34+ cells from multiple myeloma or non-Hodgkin's lymphoma patients were stored in flasks containing air (approx. 20% O-2 and approx. 0.05% CO2) or 3% O-2/6% CO2 atmosphere, for 3, 5, and 7 days at 4 degrees C. The total number of cells, the number of cells in G0 or G1 phase of cell cycle, and the apoptosis rate were determined. The functional capacity of stored cells was assessed by the capacity of progenitors to form colonies in methylcellulose (colony-forming cells [CFCs]) and of stem cells to repopulate the bone marrow (BM) of immunodeficient mice (SCID-repopulating cell [SRC] assay). RESULTS: The total number of viable cells and cells in G1 phase as well as the number of total CFCs were significantly higher at 3% O-2/6% CO2 than in air at all time points. Cells in G0 phase and SRC were equally preserved in both conditions. CONCLUSION: Atmosphere with low O-2 and high CO2 concentration (3% O-2/6% CO2) in hypothermia (+4 degrees C) during 7 days of storage prevents cell damage and preserves a high number of functional HSCs and progenitors mobilized in PB by granulocyte-colony-stimulating factor.