Chick osteocyte-derived protein inhibits osteoclastic bone resorption

Akiko Maejima-Ikeda, Mari Aoki, Katsuki Tsuritani, Kayo Kamioka, Kenji Hiura, Toshio Miyoshi, Hiroshi Hara, Teruko Takano-Yamamoto, Masayoshi Kumegawa

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


In order to investigate the role of osteocytes in bone resorption, we examined the homogenate and conditioned medium from purified chick calvarial osteocytes in a pit-formation assay using unfractionated bone cells from mice. The osteocyte homogenate markedly inhibited pit formation, whereas the conditioned medium of osteocytes had no effect. This inhibitory activity was not the result of cytotoxicity of the homogenate. A novel bone-resorption-inhibitory protein was purified from collagenase-digested chick calvarial fragments enriched in osteocytes. The inhibitory protein, of molecular mass 18.5 kDa, showed significant dose-dependent inhibition of pit formation by unfractionated bone cells from mice and rabbits, and by human giant tumour cells. This protein also inhibited the bone-resorbing activity of purified osteoclasts in the pit-formation assay in the absence of other effector cells. Microinjection of the protein into osteoclasts caused disruption of the podosomes in the cells. The N-terminal 25-amino-acid sequence of the protein showed 68% identity to a part of Rho-GTP-dissociation inhibitor. Thus chick calvarial osteocytes may be involved in the regulation of bone resorption by osteoclasts.

Original languageEnglish
Pages (from-to)245-250
Number of pages6
JournalBiochemical Journal
Issue number1
Publication statusPublished - 1997 Feb 15
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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