| Background:Porphyromonas gingivalis is an important periodontal pathogenic bacteria,which can generate large amounts of virulence factors, such as endotoxin,collagenase and trypsin-like protease. These virulence factors will cause thedestruction of periodontal tissue and alveolar bone resorption.Lipopolysaccharide is known as a key factor which can cause alveolar boneresorption. On one hand, it can promote bone resorption by promoting osteoclastdifferentiation, on the other hand, it can also inhibit differentiation of osteoblastand suppress bone formation. The research on the mechanism of LPS-inducedimbalance of bone homeostasis has been extensive carried out. However, theexact molecular mechanism has yet no clear conclusion. In recent years, theeffect of Eph/ephrin cell signaling pathway on the regulation of bonehomeostasis is on the list of concern. Recent studies have shown that EphA2/ephrinA2signaling pathway between osteoblast and osteoclast play a key rolein the initial process of bone remodeling. When the communication betweenosteoblast and osteoclast occurs, the forward signal and reverse signal receivedby osteoclasts can promote the differentiation of osteoclast and accelerate boneresorption. The forward signal mediated by EphA2receptor on osteoblast caninhibit the differentiation of osteoblast and the process of bone formation. Withthe functional status of bone cells change, the state of bone homeostasistransform to bone resorption ultimately. However, there has no been report thatwhether Pg-LPS activates the process of bone resorption though EphA2/ ephrinA2signaling pathway.In this study, we try to investigate the effect ofPg-LPS on the expression of EphA2in MC3T3-E1cell and have somepreliminary understanding of the effect of Pg-LPS on EphA2/ephrinA2signalingpathway.Methods:MC3T3-E1cell was co-cultured with1g/ml of Pg-LPS at3,7and14d.EphA2and the osteogenic related genes (Runx2, ColⅠ, ALP andSp7) weredetected by RT-PCR. EphA2protein was detected by Western blotting. Thealkaline phosphatase activity was determined by PNPP method.Results:1. RT-PCR result showed that: After MC3T3-E1cell was co-cultured withPg-LPS,EphA2gene expression in the experimental group was significantlyhigher than control group. In10min group, compared with the control group,there is no significant difference of EphA2gene expression in the experimentalgroup. In1h group, the experimental group had an obviously increase on EphA2gene expression.2. RT-PCR results showed that: After MC3T3-E1cell was co-cultured withPg-LPS, at3d and7d, EphA2gene expression in the experimental group wassignificantly higher than control group (P<0.01), peak in the3d. At14d, EphA2gene expression between the two groups had no significant difference. At3d and7d, ALP and Sp7genes expression were significantly reduced. ALP gene wasdecline obviously at7d. At14d, there were no significant differences. The geneexpressions of ColⅠ and Runx2had no significant differences at3d,7d and14d.3. Western blotting result showed that: After MC3T3-E1cell wasco-cultured with Pg-LPS, at7d, EphA2expression in the experimental groupwas significantly higher than control group. However, at3d and14d, there were no significant differences.4. ALP activity result showed that: After MC3T3-E1cell was co-culturedwith Pg-LPS, at3d,7d and14d, ALP activity was significantly reduced byPg-LPS (P<0.05), peak in the3d. At3d, compared with the control group, theexperimental group reduced by35%(P<0.01). At7d, the experimental groupreduced by17%(P<0.05).Conclusions:1. In the absence of osteogenic conditions, Pg-LPS can promoteMC3T3-E1cells expressing EphA2gene.2. In osteogenic conditions, Pg-LPS can inhibit MC3T3-E1celldifferentiate into osteoblast at premetaphase stage, but it has no effect atterminal stage.3. Pg-LPS could inhibit MC3T3-E1cell differentiate into osteoblast byEphA2/ephrinA2signaling pathway. |
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