Mechanical strain-mediated reduction in RANKL expression is associated with RUNX2 and BRD2.

Autor: Galea GL; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA; Developmental Biology and Cancer, UCL GOS Institute of Child Health, London, UK; Comparative Bioveterinary Sciences, Royal Veterinary College, London, UK., Paradise CR; Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, USA; Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA., Meakin LB; School of Veterinary Sciences, University of Bristol, Bristol, UK., Camilleri ET; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA., Taipaleenmaki H; Molecular Skeletal Biology Laboratory, Department of Trauma, Hand and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany., Stein GS; Department of Biochemistry, University of Vermont College of Medicine, Burlington, VT, USA., Lanyon LE; School of Veterinary Sciences, University of Bristol, Bristol, UK., Price JS; School of Veterinary Sciences, University of Bristol, Bristol, UK., van Wijnen AJ; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA; Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA. Electronic address: vanWijnen.Andre@mayo.edu., Dudakovic A; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA; Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA. Electronic address: Dudakovic.Amel@mayo.edu.
Jazyk: angličtina
Zdroj: Gene [Gene] 2020 Dec; Vol. 763S, pp. 100027. Date of Electronic Publication: 2020 Jan 16.
DOI: 10.1016/j.gene.2020.100027
Abstrakt: Mechanical loading-related strains trigger bone formation by osteoblasts while suppressing resorption by osteoclasts, uncoupling the processes of formation and resorption. Osteocytes may orchestrate this process in part by secreting sclerostin (SOST), which inhibits osteoblasts, and expressing receptor activator of nuclear factor-κB ligand (RANKL/TNFSF11) which recruits osteoclasts. Both SOST and RANKL are targets of the master osteoblastic transcription factor RUNX2. Subjecting human osteoblastic Saos-2 cells to strain by four point bending down-regulates their expression of SOST and RANKL without altering RUNX2 expression. RUNX2 knockdown increases basal SOST expression, but does not alter SOST down-regulation following strain. Conversely, RUNX2 knockdown does not alter basal RANKL expression, but prevents its down-regulation by strain. Chromatin immunoprecipitation revealed RUNX2 occupies a region of the RANKL promoter containing a consensus RUNX2 binding site and its occupancy of this site decreases following strain. The expression of epigenetic acetyl and methyl writers and readers was quantified by RT-qPCR to investigate potential epigenetic bases for this change. Strain and RUNX2 knockdown both down-regulate expression of the bromodomain acetyl reader BRD2. BRD2 and RUNX2 co-immunoprecipitate, suggesting interaction within regulatory complexes, and BRD2 was confirmed to interact with the RUNX2 promoter. BRD2 also occupies the RANKL promoter and its occupancy was reduced following exposure to strain. Thus, RUNX2 may contribute to bone remodeling by suppressing basal SOST expression, while facilitating the acute strain-induced down-regulation of RANKL through a mechanosensitive epigenetic loop involving BRD2.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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