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Effect of Anti-c-fms Antibody on Osteoclast Formation and Proliferation of Osteoclast Precursor In Vitro
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Does TNF have anti-osteoclastogenic actions?

Jameel Iqbal1

  • 1Department of Endocrinology (1055), Mount Sinai School of Medicine, One Gustave L. Levy Place New York, NY 10029, USA. jameel.iqbal@mssm.edu

Annals of the New York Academy of Sciences
|July 13, 2006
PubMed

Insights

Tumor necrosis factor (TNF) contributes to bone loss by increasing osteoclast precursors, not directly enhancing osteoclast differentiation. This finding revises understanding of TNF

Area of Science:

  • Immunology
  • Bone Biology
  • Cell Biology

Background:

  • Tumor necrosis factor (TNF) is implicated in bone resorption and degradation.
  • Existing models suggest TNF directly promotes osteoclast formation and activity.
  • Observed osteopenia severity with TNF differs from genetic models (OPG-/-), prompting re-evaluation.

Purpose of the Study:

  • To investigate the direct effects of TNF on osteoclast differentiation.
  • To test the hypothesis that TNF directly enhances osteoclast formation.
  • To elucidate the precise mechanisms underlying TNF-induced bone loss.

Main Methods:

  • Examined TNF's impact on RANKL-induced osteoclast formation.
  • Assessed expression of osteoclast markers (TRAP, cathepsin K) with TNF treatment.
  • Quantified osteoclast differentiation in the presence of varying TNF concentrations.

Main Results:

  • TNF decreased RANKL-induced expression of osteoclast markers TRAP and cathepsin K.
  • TNF did not significantly increase RANKL-induced osteoclast differentiation at tested doses.
  • TNF appears to promote osteoclastogenesis by increasing the pool of osteoclast precursors (macrophages).

Conclusions:

  • TNF's pro-osteoclastogenic effects are not mediated by direct enhancement of osteoclast differentiation.
  • TNF's role in bone resorption may involve indirect mechanisms, such as modulating precursor availability.
  • Findings necessitate a revised understanding of TNF's contribution to bone metabolism and disease.

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