The Growth of Bone Marrow Cells in Liquid Culture

S ummary . Liquid suspension cultures of mouse bone marrow cells at high and low density were prepared in supplemented Eagle's medium containing 10% of a partially purified extract of mouse embryos and pregnant mouse uterus (PMU). In the low cell density cultures the number of cells decreased for 2 days; by 4 days the agar colony-forming cells (agar CFC) had risen ten-fold and the spleen colony-forming units (spleen CFU) had fallen to one tenth; between 4 and 8 days the total cell count showed a four-fold increase and the final cell number exceeded the number of the original culture. The cells produced were mainly macrophages. If PMU was not included in the culture the agar CFC disappeared after 4 days and there was no cell multiplication. In the high cell density cultures a similar pattern was observed; in the presence of PMU the agar CFC showed an increase in number, the spleen CFU decreased and an increase in cell number occurred between 4 and 8 days. However, the cells produced were predominantly granulocytes. In the absence of PMU from this cell culture, agar CFC were maintained for 6 days and the cell population remained predominantly granulocytic. These methods of growing cell enable cell recovery from the cultures to be made at any stage and provide an opportunity to study the kinetics and functional capacity of the cells produced.