Effect of Dexamethasone and Deflazacort on the Function and Gene Expression of the Primary Cultured Human Osteoblast-Like Cells / 대한내분비학회지

ABSTRACT

Background: Chronic use of glucocorticoid is known to result in osteoporosis. Deflazacort (DFZ), a synthetic glucocorticoid, has been reported to have bone sparing properties in vivo eompared to dexamethasone(DEX). Not only the direct effect of DFZ on human osteoblast but the mechanism by which the drug spares bone remains unclear. This study, therefore, is aimed to investigate the direct effect of DFZ on the proliferation and differentiation of human osteoblast as well as on the gene expression of osteocalcin and osteoblast as well as on the gene expression of osteocalcin and growth factor produced in osteoblast. Methods: Human osteoblast-like cells were cultured from a piece of the tibia removed during selective orthopedic surgery for patients without metabolic bone diseases. The morphological iden- tification of osteoblast-like cell was performed under the light microscope after alkaline phosphatase staining. Cell proliferation rate was determined by [3H] thymidine incorporation into DNA. Cell differentiation was determined by alkaline phophatase activity. mRNA expression was quanti- tatively measured by the competitive reverse transcription-polymerase ehain reaction(RT-PCR). Results: The cultured cells demonstrated 1,25-dihydroxyvitamin D3-induced increases in alkaline phophatase activity and osteocalcin mRNA expression which are the properties of osteoblast. Twenty six percent of the cultured cells were identified as osteoblast-like cells by alkaline phophatase staining. After 24hr incubation with DEX or DFZ, the [3H) thymidine incorporation was significantly inhibited by 100nM DEX or DFL Alkaine phophatase activity was significantly increased by 100nM DEX. Osteocalcin mRNA was significantly decreased by both glueocorticoids. While DEX significantly suppressed expression of asteocalcin mRNA at 10nM and 100nM, DFZ did so only at 100nM. IGF-I mRNA was significantly decreased by 100nM DEX. Conclusion: These results suggest that the inhibitory effect of DFZ on the cell proliferation and protein synthesis is less than that of DEX, which might be responsible for the bone sparing effect of DFZ in vivo.