Osteogenic induction and 1,25-dihydroxyvitamin D3 oppositely regulate the proliferation and expression of RANKL and the vitamin D receptor of human periodontal ligament cells

Objective: Human periodontal ligament cells (hPDLCs) may play an important role in osteoclastogenesis in alveolar bone by expressing the receptor activator of NF-KappaB ligand (RANKL) and osteoprotegerin (OPG). The present study aimed to investigate the differences between the effects of osteogenic induction and 1,25-dihydroxyvitamin D-3 (VD3) on hPDLC proliferation and the expression of RANKL, osteoprotegerin, and the vitamin D receptor (VDR) in hPDLCs. Methods: Primary cultures of 11 hPDLC populations from 11 donors were obtained. Three samples of each hPDLC population from passage 3 were, respectively, treated with osteogenic induction medium, 10(-8) M VD3, or vehicle as a control. Cell proliferation at days 0, 1, 3, 5, and 7 was estimated with the MTT method. At day 6, the mRNA levels of RANKL, CPG and VDR were determined with real-time RT-PCR. Results: Osteogenic induction significantly promoted hPDLC proliferation, while VD3 inhibited proliferation. Osteogenic induction significantly down-regulated the mRNA level of RANKL by 1.61-fold (P = 0.033) and decreased the level of VDR by 2.13-fold (P = 0.003), while there was no change in the level of OPG and OPG/RANKL ratio with osteogenic induction. on the contrary, VD3 significantly up-regulated the level of RANKL by 9.58-fold (P = 0.001) and increased the level of VDR by 3.15-fold (P = 0.004), while down-regulating the OPG/RANKL ratio by 7.14-fold (P = 0.004). Conclusion: Osteogenic induction and VD3 exert opposite effects in regulating hPDLC proliferation and mRNA expression of RANKL and VDR. This may induce hPDLCs to play different roles in alveolar bone metabolism. (C) 2009 Elsevier Ltd. All rights reserved.