Peer Reviewed

1

Document Type

Article

Publication Date

9-2010

Keywords

Cell Culture, Cell Differentiation, Cytology, Drug Effect, Gene Expression Regulation, Gene Silencing, Genetics, Human, Metabolism, Osteoblast, Physiology

Comments

The origingal publication is available from http://www.biomedcentral.com

Abstract

BACKGROUND: The Wnt/β-catenin pathway is a major signaling cascade in bone biology, playing a key role in bone development and remodeling. The objectives of this study were firstly, to determine the effects of dexamethasone exposure on Wnt/β-catenin signaling at an intracellular and transcriptional level, and secondly, to assess the phenotypic effects of silencing the Wnt antagonist, Dickkopf-1 (Dkk1) in the setting of dexamethasone exposure. METHODS: Primary human osteoblasts were exposed in vitro to 10-8 M dexamethasone over a 72 h time course. The phenotypic marker of osteoblast differentiation was analyzed was alkaline phosphatase activity. Intracellular β-catenin trafficking was assessed using immunoflourescence staining and TCF/LEF mediated transcription was analyzed using a Wnt luciferase reporter assay. Dkk1 expression was silenced using small interfering RNA (siRNA). RESULTS: Primary human osteoblasts exposed to dexamethasone displayed a significant reductions in alkaline phosphatase activity over a 72 h time course. Immunoflourescence analaysis of β-catenin localization demonstrated a significant reduction in intracytosolic and intranuclear β-catenin in response to dexamethasone exposure. These changes were associated with a reduction of TCF/LEF mediated transcription. Silencing Dkk1 expression in primary human osteoblasts exposed to dexamethasone resulted in an increase in alkaline phosphatase activity when compared to scrambled control. CONCLUSIONS: Wnt/β-catenin signaling plays a key role in regulating glucocorticoid-induced osteoporosis in vitro. Silencing Dkk1 expression rescues dexamethasone-induced suppression of primary human osteoblast differentiation. Targeting of the Wnt/β-catenin signaling pathway offers an exciting opportunity to develop novel anabolic bone agents to treat osteoporosis and disorders of bone mass.

Disciplines

Medicine and Health Sciences | Orthopedics | Surgery

Citation

Butler JS, Queally JM, Devitt BM, Murray DW, Doran PP, O'Byrne JM. Silencing Dkk1 expression rescues dexamethasone-induced suppression of primary human osteoblast differentiation. BMC Musculoskeletal Disorders. 2010; 11:210.

PubMed ID

20843343

DOI Link

10.1186/1471-2474-11-210

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