Sclerostin expression in trabecular bone is downregulated by osteoclasts

Sci Rep. 2020 Aug 13;10(1):13751. doi: 10.1038/s41598-020-70817-1.

Abstract

Bone tissues have trabecular bone with a high bone turnover and cortical bone with a low turnover. The mechanisms by which the turnover rate of these bone tissues is determined remain unclear. Osteocytes secrete sclerostin, a Wnt/β-catenin signaling antagonist, and inhibit bone formation. We found that sclerostin expression in cortical bone is more marked than in trabecular bone in Sost reporter mice. Leukemia inhibitory factor (LIF) secreted from osteoclasts reportedly suppressed sclerostin expression and promoted bone formation. Here, we report that osteoclasts downregulate sclerostin expression in trabecular bone and promote bone turnover. Treatment of C57BL/6 mice with an anti-RANKL antibody eliminated the number of osteoclasts and LIF-positive cells in trabecular bone. The number of sclerostin-positive cells was increased in trabecular bone, while the number of β-catenin-positive cells and bone formation were decreased in trabecular bone. Besides, Tnfsf11 heterozygous (Rankl+/-) mice exhibited a decreased number of LIF-positive cells and increased number of sclerostin-positive cells in trabecular bone. Rankl+/- mice exhibited a decreased number of β-catenin-positive cells and reduced bone formation in trabecular bone. Furthermore, in cultured osteoclasts, RANKL stimulation increased Lif mRNA expression, suggesting that RANKL signal increased LIF expression. In conclusion, osteoclasts downregulate sclerostin expression and promote trabecular bone turnover.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Antibodies / immunology
  • Biomarkers, Tumor / metabolism
  • Bone Density
  • Bone Remodeling / physiology*
  • Cancellous Bone / metabolism*
  • Cortical Bone / metabolism
  • Leukemia Inhibitory Factor / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Osteoclasts / metabolism*
  • RANK Ligand / genetics*
  • RANK Ligand / immunology
  • Up-Regulation / genetics
  • Wnt Signaling Pathway / physiology

Substances

  • Adaptor Proteins, Signal Transducing
  • Antibodies
  • Biomarkers, Tumor
  • Leukemia Inhibitory Factor
  • Lif protein, mouse
  • RANK Ligand
  • Sost protein, mouse
  • Tnfsf11 protein, mouse