An effect of FGF on periodontal ligament-derived epithelial cell proliferation and differentiation for a regenerative dental implant therapy

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Human periodontal ligament-derived epithelial cells (Epithelial rests of Malassez : ME) are derived from Hertwig's epithelial root sheath. In this study, we have developed a serum-free culture system of ME. The mitogenic effect of fibroblast growth factor (FGF) in the ME, human periodontal ligament-derived fibroblast cells (PLF) were investigated by serum-free growth assay. In addition, we demonstrated the expression of FGF receptor (FGFR) in the ME and the expression of FGF in the PLF by reverse transcription-polymerase chain reaction (RT-PCR), PCR-Southern hybridization, immunohistochemical examination, western blotting and ribonuclease protection assay (RPA). Both FGF-1 and FGF-7/keratinocyte growth factor (KGF) stimulated cell growth of the ME. On the other hand, both FGF-1 and FGF-2 stimulated cell growth of the PLF. RT-PCR and PCR-Southern analysis revealed that the ME expressed FGFR2-(IIIb) mRNA but not mRNAs for FGFR1-(IIIc), FGFR2-(IIIc), FGFR3-(IIIb), FGFR3-(IIIc) and FGFR4. An immunohistochemical analysis of FGF-7/KGF revealed that immunoreactive FGF-7/KGF were detected predominantly in the cytoplasm of which type of cell. PCR-Southern, western blotting and RPA revealed that the PLF expressed FGF-7/KGF mRNA. These results suggest that the FGF-FGFR2-(IIIb) system play an important role in the growth and differentiation of ME. In addition, endogenously produced FGFs work as paracrine interactive regulators of the growth and differentiation between ME and PLF.