Influence of lipopolysaccharide on EPHRIN/EPH expression in human periodontal ligament fibroblasts

Abstract

AIMS: To clarify the mechanism of periodontitis-induced alveolar bone modification through ephrin/Eph signalling in periodontal ligament fibroblasts (PDLF) at the time-dependent level. MATERIALS AND METHOD: Primary human PDLF were isolated from premolars extracted during orthodontic treatment in juvenile patients. PDLF were challenged with 0.1 μg/mL P. gingivalis lipopolysaccharide (LPS) for 6 to 48 hours. Untreated PDLF served as the control. Quantitative real-time polymerase chain reaction was performed to evaluate the expression of ephrinA2/EphA2 and ephrinB2/EphB4 released by PDLF. RESULTS: After stimulation with LPS, the mRNA expression of ephrinA2 was significantly up-regulated in a time-dependent manner from 12 to 24 hours. At 48 hours, the ephrinA2 expression level was slightly decreased but remained markedly higher than the control. EphA2 expression showed no change for the first 24 hours, after which there was a significant increase at 48 hours. EphB4 expressed lower mRNA at 12 and 24 hours compared to the control group, followed by an insignificant change at 48 hours. In contrast, the gene expression of ephrinB2 showed no dramatic change when treated with LPS up to 48 hours. CONCLUSION: LPS has a suppressive effect on EphB4 expression contributing to osteogenesis inhibition and a stimulative influence on ephrinA2/EphA2 expression in PDLF leading to bone resorption. At the early stage of LPS challenge (12 and 24 hours), the up-regulation of ephrinA2 and down-regulation of EphB4 have a synergistic effect on bone resorption. However, the insignificant change of EphB4 and increase of ephrinA2 and EphA2 by 48 hours implies that ephrinA2/EphA2 may play a dominant role at the later stage of LPS stimulation. Elucidation of the PDLF communication stimulated by LPS sheds light on the difference between pathologic bone resorption caused by periodontitis and bone remodelling induced by orthodontic force loading, which contributes to a better understanding of the mechanism in orthodontic treatment with periodontal inflammation.