DEXAMETHASONE INHIBITS THE DEVELOPMENT OF MAST-CELLS FROM DISPERSED HUMAN FETAL LIVER-CELLS CULTURED IN THE PRESENCE OF RECOMBINANT HUMAN STEM-CELL FACTOR

Human fetal liver cells cultured in the presence of recombinant human stem cell factor (rhuSCF) give rise to highly purified mast cell popul ations. This study examined the effect of steroid hormones on mast cel l differentiation. Dispersed fetal liver cells cultured in the presenc e of rhuSCF at 50 ng/ml and in the presence or absence of various ster oid hormones for 4 weeks, were analysed for the presence of mast cells by metachromatic staining with toluidine blue, by immuno-histochemist ry with a monoclonal antibody against tryptase, and by immunofluoresce nt flow cytometry with a monoclonal antibody against Kit. Dexamethason e added to the cultures at day 0 resulted in a dose-dependent inhibiti on of rhuSCF-induced mast cell differentiation with > 85% inhibition s een at a dose of 10(-6) M. A similar effect was seen with hydrocortiso ne, but not with oestradiol or progesterone. The addition of dexametha sone resulted in decreased DNA synthesis in 14-day-old cultured cells, as assessed by incorporation of bromodeoxyuridine. Addition of dexame thasone to 3-week-old SCF-dependent fetal liver mast cells had no sign ificant effect on mast cell survival. Removal of dexamethasone after 3 weeks of culture with SCF did not result in mast cell development. Th us, dexamethasone inhibits SCF-induced development of mast cells from fetal liver cells, but shows no appreciable effect on developed mast c ells.