The association of platelet-derived growth factor (PDGF) receptor tyrosine phosphorylation to mitogenic response of human osteoblastic cells in vitro.

OBJECTIVES: The purpose of this study was to make clear the relationship of human osteoblastic ceil growth, induced by platelet-derived growth factor (PDGF), to PDGF receptor tyrosine phosphorylation. MATERIALS AND METHODS: Osteoblastic cells derived from human maxilla were cultured with human PDGF. The cell growth was evaluated by cell number and DNA synthesiS. PDGF receptor tyrosine phosphorylation was detected by immunoblot analysis using anti-PDGF receptor α, β subunits and anti-phosphotyrosine antibodieS. Genistein, a tyrosine kinase inhibitor, was added to the culture to investigate the effect on osteoblastic cell growth and PDGF receptor tyrosine phosphorylation induced by PDGF. RESULTS AND CONCLUSIONS: PDGF stimulated the proliferation of human osteoblastic cells and this effect was synergetic with serum stimulation. DNA synthesis of osteoblastic cells was elevated by PDGF in a dose dependent manner at the minimum concentration of I ng ml-1.PDGF also induced PDGF receptor tyrosine phosphorylation within 1 min on osteoblastic cells, and tyrosine phosphorylation occurred on PDGF receptor subunits α and β.Genistein inhibited cell growth and receptor tyrosine phosphorylation, which was induced by PDGF on these cellS. In conclusion, human osteoblastic cell growth induced by PDGF is shown to relate to tyrosine kinase of PDGF receptors.