PORPHYROMONAS-GINGIVALIS LIPOPOLYSACCHARIDE MODULATES THE RESPONSIVENESS OF HUMAN PERIODONTAL-LIGAMENT FIBROBLASTS TO PLATELET-DERIVED GROWTH-FACTOR

Lipopolysaccharides (LPS) prepared from periodontopathic bacteria have been known to induce various biological responses which may lead to p eriodontal tissue breakdown. The purpose of this study was to determin e if Porphyromonas gingivalis LPS could affect cellular functions of h uman periodontal ligament fibroblasts (HPLF). We showed here the respo nsiveness of cultured HPLF to platelet-derived growth factor (PDGF)-BB , a growth factor for mesenchymal cells, in the presence of P. gingiva lis LPS. DNA synthesis of HPLF was enhanced in a dose-dependent manner when LPS were co-incubated for 48 h; thereafter, it decreased to the baseline level within 24 h incubation. The stimulating effect of PDGF- BB was further enhanced by the pretreatment of HPLF with LPS (10 mu g/ ml) for 48 h. The binding assay of [I-125]PDGF-BB and the flow cytomet ric assay using rabbit antiserum to human PDGF receptor (PDGF-R) beta- type indicated that this enhancement was due to the increase of the nu mber of PDGF-R beta-type on HPLF. Immunoprecipitation using antiserum to human PDGF-R beta-type also showed that the synthesis of PDGF-R bet a-type was augmented in the LPS-treated HPLF. These results indicate t hat P. gingivalis LPS stimulate cellular proliferation and responsiven ess to PDGF-BB of cultured HPLF. These cellular reactions may be media ted by PDGF-BB binding, followed by increased synthesis of the recepto r protein.