EXPRESSION OF RECEPTORS FOR BASIC FIBROBLAST-GROWTH-FACTOR ON HUMAN PERIODONTAL-LIGAMENT CELLS

Basic fibroblast growth factor (FGF-2; bFGF) is a major mitogen for co nnective tissue cells, and participates in the healing process. It has already been reported that FGF-2 could be applicable to enhance perio dontal regeneration. In the present study, we examined FGF receptor (F GFR) expression on human periodontal ligament (PDL) cells. The binding of [I-125]-labeled FGF-2 to human PDL cells was studied by radiorecep tor assay. The binding of [I-125]-FGF-2 to PDL cells reached a plateau after 2.5 h incubation at 4 degrees C and was inhibited by the additi on of unlabeled FGF-2 and acidic FGF (FGF-1; aFGF), but not insulin-li ke growth factor-I, platelet-derived growth factor and transforming gr owth factor-beta(1). Scatchard analysis revealed the presence of appro ximately 1.0 x 10(5) FGF-2 binding sites per cell with an apparent Kd of 1.2 x 10(-10) M. Interestingly, the binding of [I-125]-FGF-2 on PDL cells reached its maximum at d 6 of the culture and then gradually de creased. Scatchard analysis also demonstrated that the number of FGFRs on a PDL cell was altered during the course of the culture: while the affinity between FGF-2 and its receptor was not. The responsiveness o f PDL cells to FGF-2, which was monitored by the inhibitory effect on alkaline phosphatase activity, was reduced in proportion to the decrea se in the number of FGFRs on the PDL cells. The present study suggests that PDL cells alter the responsiveness to FGF-2 during the course of the culture by changing the density of its receptor, and that the den sity of FGFR expression might be a marker of the cytodifferentiation o f PDL cells into mineralized tissue forming cells.