Differentiation pathways of pluripotent hemopoietic stem cells in long-term mouse bone marrow culture

Differentiation pathways of CFU-S were examined in mouse bone marrow long-term culture system. E/G ratios of non-adherent CFU-S in this system increased from 2 to 7-9 by 2-3 weeks of culture and then fluctuated during the culture period. On the other hand, E/G ratios of adherent CFU-S were lower than that of non-adherent CFU-S, and always remained under 2. Some of the supernatants collected from culture flasks at weekly intervals increased E/G ratios of normal bone marrow CFU-S after 18-20 h of incubation. These results suggest that the differentiation of CFU-S is controlled by humoral factors, secreted from yet unknown cells in bone marrow, in this system.