Control of pH in human long-term bone marrow cultures with low-glucose medium containing zwitterion buffer lengthens the period of haemopoietic activity

Primary long-term bone marrow cultures grown in 40 mM HEPES-buffered McCoy's 5A medium produced granulocyte-macrophage colony-forming units (CFU-GM) for a median of 9 weeks compared with 7 weeks with CO2/bicarbonate-buffered cultures. Reducing the medium glucose concentration (from 12.5 to 2.75 mM) extended the culture longevity to 17 weeks. The median period of erythroid colony detection increased from 6 to 8 weeks. Secondary cultures (5 x 106 cord blood mononuclear cells seeded on irradiated stroma) showed statistically similar myeloid and erythroid longevity to primary cultures. Improved control of medium pH significantly improved the capacity of long-term stromal layers to maintain stem cells in vitro