Glucocorticoids Antagonize RUNX2 During Osteoblast Differentiation in Cultures of ST2 Pluripotent Mesenchymal Cells

Authors

  • Theodora Koromila,

    1. Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
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  • Sanjeev K. Baniwal,

    1. Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
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  • Yae S. Song,

    1. Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
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  • Anthony Martin,

    1. Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
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  • Jian Xiong,

    1. Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
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  • Baruch Frenkel

    Corresponding author
    1. Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
    2. Department of Orthopedic Surgery, Institute for Genetic Medicine, Keck School of Medicine of the University of Southern California, Los Angeles, California
    • Correspondence to: Prof. Baruch Frenkel, USC Institute for Genetic Medicine, 2250 Alcazar Street, CSC-240, Los Angeles, CA 90033.

      E-mail: frenkel@usc.edu

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ABSTRACT

The efficacy of glucocorticoids (GCs) in treating a wide range of autoimmune and inflammatory conditions is blemished by severe side effects, including osteoporosis. The chief mechanism leading to GC-induced osteoporosis is inhibition of bone formation, but the role of RUNX2, a master regulator of osteoblast differentiation and bone formation, has not been well studied. We assessed effects of the synthetic GC dexamethasone (dex) on transcription of RUNX2-stimulated genes during the differentiation of mesenchymal pluripotent cells into osteoblasts. Dex inhibited a RUNX2 reporter gene and attenuated locus-dependently RUNX2-driven expression of several endogenous target genes. The anti-RUNX2 activity of dex was not attributable to decreased RUNX2 expression, but rather to physical interaction between RUNX2 and the GC receptor (GR), demonstrated by co-immunoprecipitation assays and co-immunofluorescence imaging. Investigation of the RUNX2/GR interaction may lead to the development of bone-sparing GC treatment modalities for the management of autoimmune and inflammatory diseases. J. Cell. Biochem. 115: 27–33, 2014. © 2013 Wiley Periodicals, Inc.

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