DEXAMETHASONE REGULATION OF MARROW STROMAL-DERIVED OSTEOBLASTIC CELLS

The clonal subtypes of cells in the osteogenic family represented by f ibroblastaoid MBA-15.33, preosteoblast MBA-15.4, and mature osteoblast ic MBA-15.6 cells were used to study the effects of glucocorticoid (de xamethasone). The role of dexamethasone was monitored on cell attachme nt when plated on various protein substrata (BSA, collagen I, and Matr igel). A 24 h exposure of the cells to 10(-6) M or 10(-7) M dexamethas one differential affects their attachment preference. MBA-15.33 and MB A-15.4 cells increased their attachment capability on collagen I, whil e MBA-15.6 cells' attachment was inhibited. Pretreatment with (10(-6) M) dexamethasone caused an increase in attachment on Matrigel by MBA-1 5.33 cells and to less extent by MBA-15.4 cells. Additionally, measure ments of two enzymatic activities were monitored; one is alkaline phos phatase (ALK-P), and the second is neutral endopeptidase (CD10/NEP).MB A-15.33, MBA-15.4, and MBA-15.6 cells were exposed to dexamethasone or to various growth factors (bone morphogenic protein (BMP-2 and BMP-3) , TGF beta, and IGF-I). In some experiments, pretreatment oi cells by dexamethasone was followed by exposure to the growth factors. The cell s' challenged cellular responses were not uniform and revealed a diffe rential pattern when their ALK-P and CD10/NEP enzymatic activities wer e measured. (C) 1996 Wiley-Liss, Inc.