Dexamethasone Modulates BMP-2 Effects on Mesenchymal Stem Cells In Vitro

Dexamethasone/ascorbic acid/glycerolphosphate (DAG) and bone morphogenic protein (BMP)-2 are potent agents in cell proliferation and differentiation pathways. This study investigates the in vitro interactions between dexamethasone and BMP-2 For an osteoblastic differentiation of mesenchymal stein cells (MSCs). Bone marrow-derived human MSCs were cultured with DAG (group A), BMP-2+DAG (group B), and DAG+BMP-2 combined with a porous collagen I/III scaffold (group C). RT-PCR, ELISA, immuncytochemical stainings and flow cytometry analysis served to evaluate the osteogenic-promoting potency of each of the above conditions in terms of cell morphology/viability, antigen presentation, and gene expression. DAG induced Collagen I secretion from MSCs, which was further increased by the combination of DAG+BMP-2 In comparison. the collagen scaffold and the control samples showed no significant influence on Collagen I secretion of MSCs. DAG stimulation of MSCs led also to a steady but not significant increase of BMP-2 level. A DAG and more, a DAG+BMP-2, stimulation increased the number of mesenchymal cells (CD105+/CD73+). All samples showed mRNA of ALP, osteopontin, Runx2, Twist 1. and 2, Notch-1/2, osteonectin, osteocalcin, BSP, and collagen-A1 after 28 days of in vitro culture. Culture media of all samples showed a decrease in Ca2+ and PO42- concentration, whereas a collagen-I-peak only occurred at day 28 in DAG- and DAG+BMP-2-stimulated bone marrow cells. In conclusion, BMP-2 enhances DAG-induced osteogenic differentiation in mesenchymal bone marrow cells. Both agents interact in various ways and can modify osteoblastic bone formation. (C) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1440-1448, 2008