Oestrogen inhibits osteoclast formation induced by periodontal ligament fibroblasts

Objective: Since tooth-associated fibroblasts are taken to participate in the formation of osteoclasts and it is unknown whether oestrogen affects this process, the effects of 17 beta-estradiol (17 beta-E(2)) were studied on osteoclastogenesis induced by human periodontal ligament fibroblasts (PLFs) and gingival fibroblasts (GFs). Methods: Human peripheral blood mononuclear cells (PBMCs) were seeded on monolayers of PLFs and GFs and cocultured for 14 days in the presence or absence of various concentrations of 17 beta-E(2). The number of tartrate resistant acid phosphatase (TRACP)-positive osteoclast-like cells (OCs) was assessed. In addition, we analysed the PBMC-induced withdrawal of the fibroblasts. mRNA expression was determined of oestrogen receptor (ER)-alpha, ER-beta, receptor activator nuclear factor kappa B ligand (RANKL), and osteoprotegerin (OPG) by PLFs and GFs. Results: PBMCs induced a higher number and larger fibroblast-free areas if cocultured with PLFs than with GFs. Concomitantly, the number of TRACP-positive OCs was significantly higher in PLF cocultures. 17 beta-E(2) inhibited the formation of OCs in PLF cocultures. 17 beta-E(2) did not alter the expression of RANKL, OPG, and ER-alpha mRNAs in either fibroblast cell population. Conclusion: Our data indicate that PLFs may promote osteoclastogenesis more strongly than GFs. 17 beta-E(2) inhibits the PLF-induced formation of osteoclast-like cells. Thus, the inhibitory effect of oestrogen on osteoclast formation appears to be cell type dependent. (C) 2010 Elsevier Ltd. All rights reserved.