The in vitro growth pattern of human bone marrow in methylcellulose stimulated by different concentrations of conditioned medium.

The proliferation of human bone marrow in methylcellulose stimulated by various concentrations of conditioned medium (CM) and observed at various intervals was studied. The growth kinetics of granulocytic aggregates was found to differ from monocytic clusters and colonies. Granulocytic aggregates showed a consistent and reproducible dose-response relationship; at day 7, the maximum number of granulocytic aggregates was found at 4% CM. At higher levels, the total number of aggregates decreased, while the number of cells per aggregate increased. The number of macrophage aggregates was far less, depending on the CM concentration. Photographic interval studies showed that at high concentrations of CM, clusters and colonies were formed earlier, but also coalesce to form one colony. Our results suggest that the proliferation kinetics of granulocytic aggregates are complex and preclude simple statements about sensitivity to colony-stimulating activity.