Development of a multipotent clonal human periodontal ligament cell line.

The periodontal ligament (PDL) that anchors the tooth root to the alveolar bone influences the lifespan of the tooth, and PDL lost through periodontitis is difficult to regenerate. The development of new PDL-regenerative therapies requires the isolation of PDL stem cells. However, their characteristics are unclear due to the absence of somatic PDL stem cell lines and because PDL is composed of heterogeneous cell populations. Recently, we succeeded in immortalizing human PDL fibroblasts that retained the properties of the primary cells. Therefore, we aimed to establish a human PDL-committed stem cell line and investigate the effects of basic fibroblast growth factor (bFGF) on the osteoblastic differentiation of the cells. Here, we report the development of cell line 1-17, a multipotent clonal human PDL cell line that expresses the embryonic stem cell-related pluripotency genes Oct3/4 and Nanog, as well as the PDL-related molecules periostin and scleraxis. Continuous treatment of cell line 1-17 with bFGF in osteoblastic induction medium inhibited its calcification, with down-regulated expression of FGF-Receptor 1 (FGF-R1), whereas later addition of bFGF potentiated its calcification. Furthermore, bFGF induced calcification of cell line 1-17 when it was co-cultured with osteoblastic cells. These results suggest that cell line 1-17 is a PDL-committed stem cell line and that bFGF exerts dualistic (i.e., promoting and inhibitory) effects on the osteoblastic differentiation of cell line 1-17 based on its differentiation stage.