| Abstract: | Murine spleen cells were cultured in vitro to study the induction of committed granulopoietic stem cell (CFU-C) proliferation and maturation. Marbrook-type diffusion cultures were established with and without the addition of colony-stimulating activity (CSA) and harvested at intervals up to 14 days for viable and differential cell counts, [3H]TdR autoradiography, and quantitation of CFU-C by the agar plate method. Without CSA there was poor cell viability and little proliferative capacity. In CSA-stimulated cultures there was a prominent rise in viable cell counts and [3H]TdR labeling indices rose from a mean of 2% at 0 time to 47% after 5 days in vitro. CFU-C increased by 70-fold in these cultures. Peak numbers of CFU-C, immature cells, and [3H]TdR-labeled cells occurred at about 7 days. Thereafter, mature granulocytes and macrophages predominated in culture. Because the liquid spleen cell culture system begins in a resting state and undergoes a wave of proliferative activity in response to CSA, it can provide a useful model system for studying phenomena associated with stem cell activation and differentiation in vitro. |
