Characterization of factors controlling the differentiation of periodontal ligament cells

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The purpose of this research was to characterize molecules which control the differentiation and function of periodontal ligament (PDL) cells. We constructed cDNA library of bovine PDL tissue and cloned cDNA of S100A4, one of the calcium binding proteins. We observed that mRNA expression level of S100A4 in PDL of erupted teeth was high and that PDL cells secreted this protein, which localized adjacent to collagen fibers. Addition of recombinant S100A4 protein to oseteoblastic culture inhibited mineralization. In culture, PDL cells under mechanical stress inceased mRNA expression of S100A4 together with cytoskeletal proteins. Although the expression level of this protein in MC3T3-E1 cells (osteoblastic cells) was low, inhibition of S100A4 expression in MC3T3-E1 cells stimulated mineraliztion in culture. These results strongly indicate that S100A4 is an inhibitor of meranlization in PDL tissue. On the other hand, porcine enamel matrix derivative (EMD) stimulated growth and differentiation of bovine PDL cells and Kusa cells (derived from mouse bone marrow), resulting the stimulation of mineralization in these culture. The stimulatory effects on osteoblastic cells could also contribute to periodontal tissue regeneration. It is important to clarify effective molecule (s) in EMD and Kusa cells are useful for this investigation. Porcine recombinant amelogenin stimulated the differentiation of Kusa cells indicating the possibility that amelogenin is the effective molecule.Although further studies are necessary, we could apply recombinant amelogenin to periodontal tissue regeneration.