Human Periodontal Ligament Cells Secrete Macrophage Colony‐Stimulating Factor in Response to Tumor Necrosis Factor‐Alpha In Vitro

Abstract

Human periodontal ligament (HPDL) cells may support osteoclastogenesis by expressing receptor activator of nuclear factor-kappa B ligand (RANKL) in response to periopathogenic factors and inflammatory cytokines. Because osteoclastogenesis requires the presence of macrophage colony-stimulating factor (M-CSF), we examined whether HPDL cells secrete M-CSF in response to tumor necrosis factor-alpha (TNF-alpha). Cultured HPDL cells were treated with TNF-alpha in serum-free condition. The expression of M-CSF and RANKL was determined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Inhibitors and anti-TNF receptor (TNFR) neutralizing antibodies were used for the inhibitory experiments. A migration assay was performed. TNF-alpha upregulated M-CSF and RANKL in HPDL cells. The effect on M-CSF expression could be partially blocked by pyrrolidine-dithiocarbamate ammonium salt and LY294002 but not by NS398. Neutralizing antibody to TNFR1 could diminish the effect of TNF-alpha. In addition, TNF-treated culture medium exhibited chemotactic effect for RAW264.7. HPDL cells are capable of secreting M-CSF and expressing RANKL in response to TNF-alpha. The upregulation of M-CSF is possibly one of the mechanisms essential for periodontal tissue destruction in response to inflammatory cytokines. The upregulation is partly through nuclear factor-kappa B (NF-kappaB) and phosphatidylinositol 3'-kinase and possibly involves TNFR1.