The effect of glucocorticosteroids on bone marrow mononuclear phagocytes in culture

The effect of hydrocortisone and dexamethasone both in vivo and in vitro was studied in mouse bone marrow cultures in methylcellulose and in two liquid culture systems, one using Leighton tubes with a flying coverslip to grow adherent colonies and the other using Teflon culture bags to obtain suspension cultures. Although the total number of nucleated bone marrow cells was not greatly influenced by glucocorticosteroid treatment of the mice, a marked decrease in the number of colony-forming units and of mononuclear phagocytes was observed. Inhibition of colony growth in methylcellulose and of growth of mononuclear phagocytes in Teflon culture bags also occurred when glucocorticosteroids were added to in vitro cultures. Both drugs caused an almost complete inhibition of the growth of adherent colonies, and 3H-thymidine labeling of the cells was correspondingly low. When the glucocorticosteroids were added to cultures pre-incubated for 5 days in the presence of conditioned medium, the 3H-thymidine labeling of macrophages and promonocytes was markedly reduced, whereas there was no change in the labeling of monoblasts.