Dexamethasone impairs growth and collagen synthesis in condylar cartilage in vitro

Abstract

The in vitro effects of dexamethasone on condylar cartilage from normal newborn mice were tested by measuring protein and DNA content, collagen synthesis, prolyl hydroxylase activity, collagen chains and by immunofluorescence the localization of type I and II collagen and fibronectin. The biochemical assays were complemented by structural studies of hormone-treated and control cultured specimens. It became apparent that both the protein and DNA content of the tissue decreased immediately following the addition of dexamethasone of the incubation system. Protein synthesis was significantly decreased by the hormone by 24 h. The degree of collagen hydroxylation was decreased by 24 h. Dexamethasone-treated condyles did not reveal a significant increase in the percentage of cold hydroxyproline of the total protein. Using the indirect immunofluorescence method, hormone-treated condyles revealed an enhancement of positive reactivity for type I collagen and fibronectin. SDS-gel electrophoresis of 3H-labeled collagen chains isolated by CM-cellulose chromatography indicated that dexamethasone did not significantly affect the ratios of the collagen chains. For further characterization, each chain was subjected to cyanogen bromide cleavage showing that the peptide maps of alpha 1(I) and alpha 1(II) chains were not different in dexamethasone-treated tissues in comparison to controls.