Incubation of murine bone marrow cells in hypoxia ensures the maintenance of marrow-repopulating ability together with the expansion of committed progenitors

We developed previously a hypoxic culture system in which progenitors endow ed with marrow-repopulating ability (MRA), unlike committed progenitors, we re selected and maintained better than in air. We report here an improvemen t to this system targeted at combining the maintenance of progenitors susta ining MRA with the numerical expansion of multipotent and committed progeni tors. Murine bone marrow cells were incubated at 1% oxygen in liquid medium supplemented with stem cell factor, granulocyte colony-stimulating factor, interleukin-6 and interleukin-3. In day 8 hypoxic cultures. the numbers of high proliferative potential and granulocyte/macrophage colony-forming cel ls (HPP-CFC and CFU-GM) were increased with respect to time zero. Colonies generated by HPP-CFC derived from hypoxic cultures exhibited a high replati ng ability, whereas colonies generated by HPP-CFC derived from control cult ures exhibited a low replating ability. MRA was fully maintained in hypoxia and markedly reduced in air. Thus, severe hypoxia is able to ensure a full maintenance of progenitors sustaining, MRA, together with a significant ex pansion of in vitro-detectable clonogenic progenitors, including those endo wed with replating ability. This system could contribute to the improvement of current techniques. for the ill vitro treatment of human haematopoietic cell populations before transplantation.