In addition to the involvement in erythropoiesis, erythropoietin (EPO) and its receptor (EPO-R) have been shown to be expressed in various nonhematopoietic organs and tissues with diverse biological effects. The purpose of this study was to evaluate the expression patterns of EPO and EPO-R in healthy and inflamed human dental pulp tissues. To gain insight into the possible mechanisms involved in the regulation of EPO and EPO-R expression, we further investigated the hypothesis that their expression in cultured human dental pulp cells (DPCs) may be regulated upon hypoxia, an important factor involved in dental pulp inflammation.
Methods
Samples of healthy and inflamed dental pulp tissues were obtained from patients undergoing surgical or orthodontic treatment. The protein localization and messenger RNA levels of EPO and EPO-R in the pulp tissues were detected by immunohistochemistry and quantitative real-time polymerase chain reaction (PCR), whereas the EPO and EPO-R expressions in DPCs in vitro were evaluated by Western blotting and quantitative real-time PCR.
Results
EPO and EPO-R proteins were detected in inflamed dental pulp, whereas no obvious EPO expression was detected in healthy dental pulp. The EPO messenger RNA level was significantly up-regulated in inflamed pulps compared with healthy pulps. Moreover, the messenger RNA and protein levels of EPO and EPO-R were up-regulated in DPCs under hypoxia in vitro.
Conclusions
The up-regulation of EPO might be involved in dental pulp inflammation, which is probably attributed to hypoxia. Further studies are needed to investigate the potential role of EPO and EPO-R in dentin-pulp repair and regeneration.
