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Estrogen regulates expression of osteoprotegerin and RANKL in human periodontal ligament cells through estrogen receptor beta.

BACKGROUND
The function of periodontal ligament (PDL) cells may be affected by estrogen. PDL cells synthesize the receptor activator of nuclear factor-kappa B ligand (RANKL) and its decoy receptor, namely, osteoprotegerin (OPG), which directly controls osteoclastogenesis. The primary aim of this study was to investigate how estrogen affects the expression of OPG and RANKL in human PDL (hPDL) cells.


METHODS
We used a short interfering RNA technique to inhibit estrogen receptor beta (ERbeta) expression in hPDL cells; the cells were cultured with a saturating concentration of 17beta-estradiol (10(7) M) for 48 hours. Changes in the expression of OPG and RANKL were determined by reverse transcription-polymerase chain reaction and supported by Western blot analysis.


RESULTS
Estradiol caused an increase in OPG expression and decreased RANKL expression in hPDL cells. However, it had no effect on the expression of OPG and RANKL in hPDL-siERbeta (the short interfering RNA to block ER beta) cells.


CONCLUSION
Estrogen may play an important role in exerting antiresorptive effects on alveolar bone, at least in part, by increasing the expression level of OPG versus that of RANKL via ERbeta in hPDL cells.