Effects of Dexamethasone on Fibronectin Synthesis Differ Depending on the Differentiation Stages of Chondrocytes in Cultures

The effects of dexamethasone on fibronectin synthesis of epiphyseal chondrocytes were examined using the pelleted culture system of rat costal growth plate chondrocytes as an in vitro model of endochondral ossification.Physiological (1-100nM) and supraphysiological (1 nM) concentrations of dexamethasone administered from the prehypertrophic stage produced a dose-dependent decrease in secreted fibronectin levels into the culture medium quantitated by an enzyme-linked immunosorbent assay and in accumulated fibronectin levels in the cell pellets estimated by densitometric scans of immunoblots.In contrast, treatment with dexamethasone from the hypertrophic or matrix-mineralization stage resulted in less or no significant inhibition of secreted or accumulated fibronectin levels.These data indicate that rat growth plate chondrocytes in pelleted cultures may differentially respond to dexamethasone in regard to fibronectin production, depending on the differentiation stages of chondrocytes.