Influence of glucocorticoids on human osteoclast generation and activity.
Using human peripheral blood mononuclear cells as osteoclast precursors, we showed that dexamethasone stimulated osteoclast generation at a pharmacological concentration but did not affect the life span of human osteoclasts. Dexamethasone also dose-dependently increased signals for osteoclastogenesis.


BACKGROUND
Glucocorticoid-induced osteoporosis is a common and serious disease. Glucocorticoids predominantly affect osteoblast proliferation and life span. Much of the bone loss is caused by reduced bone formation, but there is also an element of increased bone resorption.


METHODS
Human peripheral blood mononuclear cells were cultured on whale dentine and induced to differentiate to osteoclasts by RANKL and human macrophage-colony stimulating factor (M-CSF). Osteoclast activity was quantified by pit area. RANKL and osteoprotegerin (OPG) expression in osteoblasts were measured by real-time RT-PCR.


RESULTS
In the early phase of osteoclast generation (0-16 days), cultures from two different donors showed that dexamethasone at 10(-8) M increased pit area by 2.5-fold, whereas lower concentrations had no effect. At the highest dexamethasone concentration (10(-7) M), pit area was reduced. In 21-day cultures from three other donors, a similar increase was seen with dexamethasone at 10(-8) M. There was, however, no evidence of increased life span of osteoclasts with dexamethasone. In human primary osteoblasts, dexamethasone dose-dependently reduced OPG and increased RANKL expression as measured by quantitative real time RT-PCR.


CONCLUSIONS
These data provide some explanation at a cellular and molecular level for the observed increase in bone resorption seen in patients treated with glucocorticoids and indicate that there are clear direct effects of glucocorticoids on bone resorption in human cell systems that may differ from other species.
Sivagurunathan
Sutharshani
S
Department of Physiology, University of Sydney, New South Wales, Australia.
Muir
Meloni M
MM
Brennan
Tara C
TC
Seale
J Paul
JP
Mason
Rebecca S
RS
D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000502:physiology* / Q000648:ultrastructure; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D010010:Osteoclasts / Q000502:physiology* / Q000648:ultrastructure; D010012:Osteogenesis / Q000187:drug effects; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B
D002352:Carrier Proteins; D005938:Glucocorticoids; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D003907:Dexamethasone; D016173:Macrophage Colony-Stimulating Factor