One of the side effects associated with glucocorticoid therapy is glucocorticoid-induced
bone loss. Glucocorticoids partly detain bone formation via the inhibition of osteoblastic
function, however, the exact mechanism of this inhibition remains elusive. In this
study, we examined the effect of dexamethasone, an active glucocorticoid analogue,
on cell viability and expression of bone remodelling-related genes in primary mouse
calvarial and cloned MC3T3-E1 osteoblasts. Using sensitive biochemical assays, we
demonstrated the apoptotic effect of dexamethasone on osteoblastic cells. Then, utilizing
Taqman probe-based quantitative RT-PCR technology, gene expression profiles of 111
bone metabolism-related genes were determined. As a result of dexamethasone treatment
we have detected significant apoptotic cell death, and six genes, including Smad3,
type-2 collagen alpha-1, type-9 collagen alpha-1, matrix metalloproteinase-2, bone
morphogenetic protein-4 and bone morphogenetic protein-8 showed (BMP-8) significant
changes in their expression on a time- and concentration-dependent manner. BMP-8,
(a novel player in bone-metabolism) exhibited a two orders of magnitude elevation
in its mRNA level and highly elevated protein concentration by Western blot in response
to dexamethasone treatment. The knockdown of BMP-8 by RNA interference significantly
increased dexamethasone-induced cell death, confirming a protective role for BMP-8
in the glucocorticoid-induced apoptosis of osteoblasts. Our results suggest that BMP-8
might be an essential player in bone metabolism, especially in response to glucocorticoids.
(C) 2011 Elsevier Inc. All rights reserved.
