Estradiol-induced Osteoprotegerin In Dental Pulp Cells Via Surface Estrogen Receptor

Introduction: Estrogen plays an important role in bone remodeling. Evidences from ovarectomized rat also indicated that estrogen affect the rate of dentin formation. Moreover, it has been shown that both odontoblast and dental pulp cells expressed estrogen receptor. Objective: The aim of this study was to investigate the effect of 17beta estradiol in human dental pulp cells, especially on the expression of receptor activator of nuclear factor kB ligans (RANKL) and osteoprotegerin (OPG). Methods: Cultured of human dental pulp cells was treated with 10^-5 to 10^-8 M of 17beta estradiol for 24 hours. The cell number was determined by MTT assay. Reverse transcription polymerase chain reaction was used to determine the pattern of gene expression. Western analysis or ELISA was used to confirm the change in protein level. Results: The results showed that estradiol could reduce RANKL/OPG expression ratio both in transcription and translation levels. Up-regulation of OPG also observed when cell were treated with BSA conjugated estradiol indicated that the signal was generated from cell surface. Application of ERK inhibitor could suppress the inductive effect of estrogen, indicating the involvement of ERK signaling pathway. Conclusion: This study indicated that human dental pulp cells responded to 17 beta estradiol by increasing the expression and synthesis of OPG. The signaling pathway was possibly occurred at the cell surface, indicating the presence of estrogen cell surface receptor and involved the ERK signaling pathway. The results support the importance of estrogen in dental pulp homeostasis.