Differential expression of receptor activator of nuclear factor-kappaB ligand and osteoprotegerin mRNA in periodontal diseases

BACKGROUND AND OBJECTIVE: Receptor activator of nuclear factor-kappaB ligand (RANKL) is responsible for the induction of osteoclastogenesis and bone resorption, whereas its decoy receptor, osteoprotegerin, can directly block this action. Because this dyad of cytokines is crucial for regulating the bone remodelling process, imbalances in their expression may cause a switch from the physiological state to enhanced bone resorption or formation. This study investigated the mRNA expression of RANKL and osteoprotegerin, as well as their relative ratio, in the gingival tissues of patients with various forms of periodontal diseases. MATERIAL AND METHODS: Gingival tissue was obtained from nine healthy subjects and 41 patients, who had gingivitis, chronic periodontitis, generalized aggressive periodontitis, and chronic periodontitis and were receiving immunosuppressant therapy. Quantitative real-time polymerase chain reaction was employed to evaluate the mRNA expression of RANKL and osteoprotegerin in these tissues. RESULTS: Compared with healthy individuals, patients in all periodontitis groups, but not those with gingivitis, exhibited stronger RANKL expression and a higher relative RANKL/osteoprotegerin ratio. In addition, osteoprotegerin expression was weaker in patients with chronic periodontitis. When patients with generalized aggressive periodontitis and chronic periodontitis were compared, the former exhibited stronger RANKL expression, whereas the latter exhibited weaker osteoprotegerin expression, and there was no difference in their relative ratio. When chronic periodontitis patients were compared with chronic periodontitis patients receiving immunosuppressant therapy, osteoprotegerin, but not RANKL, expression was stronger in the latter. CONCLUSION: This study demonstrates that RANKL and osteoprotegerin expression are differentially regulated in various forms of periodontitis, and the relative RANKL/osteoprotegerin ratio appears to be indicative of disease occurrence. This information may confer diagnostic and therapeutic value in periodontitis.     

Reduction of orthodontic tooth movement by experimentally induced periodontal inflammation in mice

Orthodontic therapy is known to have an aggravating effect on the progression of destructive periodontitis if oral hygiene is not maintained. However, it is largely unknown how active periodontitis affects the velocity of orthodontic tooth movement. In this study, we examined the effect of periodontal inflammation on orthodontic tooth movement using a mouse model. Orthodontic force was applied on the maxillary first molar of mice, with or without ligature wire to induce experimental periodontitis. The distance moved by the first molar was significantly reduced by the ligature-induced experimental periodontitis. Tartrate-resistant acid phosphatase staining revealed that the number of osteoclasts present during orthodontic treatment was lower in the pressure zone of alveolar bone in the presence of periodontal inflammation. Consistently, the expression level of receptor activator of nuclear factor-κB ligand (RANKL) in the pressure zone was decreased in the ligature group. By contrast, experimental periodontitis increased the expression of cyclooxygenase-2 mRNA in the periodontal tissues, while in vitro treatment with prostaglandin E₂ decreased extracellular signal-regulated kinase phosphorylation and RANKL expression induced by mechanical stress in osteoblasts. Taken together, these results suggest that the orthodontic force-induced osteoclastogenesis in alveolar bone was inhibited by the accompanying periodontal inflammation, at least partly through prostaglandin E₂, resulting in reduced orthodontic tooth movement.     

Mitogen-activated protein kinases mediate interleukin-1beta-induced receptor activator of nuclear factor-kappaB ligand expression in human periodontal ligament cells

BACKGROUND AND OBJECTIVE: Interleukin-1beta-stimulated receptor activator of nuclear factor-kappaB ligand (RANKL) expression in human periodontal ligament cells is partially mediated by endogenous prostaglandin E2, whereas mitogen-activated protein kinases (MAPKs) are implicated in regulating various interleukin-1-responsive genes. We investigated herein the involvement of MAPKs in interleukin-1beta-stimulated RANKL expression in human periodontal ligament cells. MATERIAL AND METHODS: Human periodontal ligament cells were pretreated separately with specific inhibitors of MAPKs, including extracellular signal-regulated kinase, p38 MAPK and c-Jun N-terminal kinase, and subsequently treated with interleukin-1beta. Following each treatment, the phosphorylation of each MAPK, the expression of RANKL, and the production of prostaglandin E2 were determined. RANKL activity was evaluated using an assay to determine the survival of prefusion osteoclasts. RESULTS: Interleukin-1beta induced RANKL expression at the mRNA and protein levels, as well as RANKL activity in human periodontal ligament cells. Interleukin-1beta also activated extracellular signal-regulated kinase, p38 MAPK, and c-Jun N-terminal kinase. Pretreatment with each MAPK inhibitor partially, but significantly, suppressed interleukin-1beta-induced RANKL expression and its activity, as well as prostaglandin E2 production. CONCLUSION: In human periodontal ligament cells, three types of MAPK inhibitor may abrogate RANKL expression and activity induced by interleukin-1beta, directly or indirectly through partial suppression of prostaglandin E2 synthesis. In addition, extracellular signal-regulated kinase, p38 MAPK, and c-Jun N-terminal kinase signals may co-operatively mediate interleukin-1beta-stimulated RANKL expression and its activity in those cells.     

Expression of receptor activator of nuclear factor kappa B ligand relates to inflammatory bone resorption, with or without occlusal trauma, in rats

BACKGROUND AND OBJECTIVE: Receptor activator of nuclear factor kappa B ligand (RANKL) is an important factor in osteoclast differentiation, activation and survival; however, its involvement in inflammatory bone resorption, with or without occlusal trauma, is unclear. The purpose of the present study was to investigate the distribution of RANKL-expressing cells in rat periodontium during lipopolysaccharide-induced inflammation with or without occlusal trauma. MATERIAL AND METHODS: Lipopolysaccharide was injected into rat gingiva of the lower left first molar to induce inflammation. In addition, the occlusal surface of the upper left first molar of rat was raised by placing a gold inlay to induce occlusal trauma in the lower left first molars. The distribution of RANKL-expressing cells was immunohistochemically observed. RESULTS: In the inflammatory model, many osteoclasts were observed at the apical inter-radicular septum on day 5 and they were reduced by day 10. On the other hand, in the inflammatory model with occlusal trauma, many osteoclasts were still observed on day 10. RANKL expression was similar to the changes in osteoclast number. The expression of RANKL increased in endothelial cells, inflammatory cells and periodontal ligament cells. CONCLUSION: These findings clearly demonstrated that RANKL expression on endothelial cells, inflammatory cells and periodontal ligament cells is involved in inflammatory bone resorption and the expression is enhanced by traumatic occlusion. These results suggest that RANKL expression on these cells is closely involved in the increase of osteoclasts induced by occlusal trauma.     

骨化三醇对人牙周膜细胞维生素D受体、RANKL和骨保护因子表达的调节

目的 探讨骨化三醇(又称1α,25-二羟维生素D3,以下简称VD3)对人牙周膜细胞(human periodontal ligament cells,hPDLC)维生素D受体(vitamin D receptor,VDR)、核因子κB受体活化因子配体(receptor activator of nuclear factor-kappa B ligand,RANKL)和骨保护因子(osteoprotegerin,OPG)表达的调节作用及相关机制.方法 原代培养12个供体来源的hPDLC群,传代培养至第3代,分别以10-8 mol/L VD3(VD,组)和0.1%无水乙醇处理(对照组),6 d后用实时荧光定量反转录聚合酶链反应(RT-PCR)法检测VDR、RANKL和OPG mRNA的表达水平.分析12个细胞群RANKL基因转录起始位点上游调控区DNA碱基序列.结果 VD3组与对照组相比,VDR mRNA表达水平显著上调(P=0.003),为对照组的(3.04±1.06)倍;RANKL mRNA表达水平显著升高(P=0.001),为对照组的9.82(0.75～119.18)倍;OPG mRNA表达水平为对照组的(94.48±39.15)%,P=0.136;OPG/RANKL比值显著下调(P=0.003),为对照组的10.36%(1.01%～138.00%).未发现RANKL基因上游调控区序列突变位点;-1832(m7984870,C/G)多态性位点基因型与RANKL mRNA的表达和调节之间无显著相关性.结论 在hPDLC中,VD3可以促进VDR mRNA的表达;VD3可显著上调RANKL mRNA的表达从而降低OPG/RANKL比值,而对OPG mRNA的表达水平影响较小.在VD3作用下,细胞群间RANKL mRNA表达的差异性可能与RANKL基因上游调控区碱基序列无关.     

不同正畸力对大鼠牙周组织压力侧核因子κB受体活化因子配基表达影响研究

目的探讨大鼠实验性牙齿移动中不同正畸力对牙槽骨核因子KB受体活化因子配基（RANKL）表达的影响。方法本研究于2010年9-12月在山西医科大学寄生虫实验室完成。选用健康雄性Wistar大鼠36只,随机分为对照组、轻力组、中力组、大力组（各9只）,分别施加0、0．29、0．49、0．98N正畸力,建立大鼠牙齿移动模型。免疫组化法检测大鼠牙周组织压力侧RANKL的表达。结果对照组RANKL有少量表达,主要分布于破骨细胞的胞核,正畸加力各组RANKL表达主要分布于压力侧牙周膜及骨改建区的破骨细胞,在基质细胞和牙周膜成纤维细胞也有表达,且其黄染程度强于对照组。各实验组牙周组织压力侧不同程度地出现血管被挤压、玻璃样变区和骨吸收陷窝。正畸力与RANKL的表达呈正相关（r=O．834,P〈0．01）。结论正畸力与大鼠牙槽骨压力侧RANKL的表达呈正相关,且0．49N为促进RANKL表达的最佳力值。     

Evidence of the presence of T helper type 17 cells in chronic lesions of human periodontal disease

Introduction:  Periodontal disease is a chronic inflammation of the attachment structures of the teeth, triggered by potentially hazardous microorganisms and the consequent immune-inflammatory responses. In humans, the T helper type 17 (Th17) lineage, characterized by interleukin-17 (IL-17) production, develops under transforming growth factor-β (TGF-β), IL-1β, and IL-6 signaling, while its pool is maintained by IL-23. Although this subset of cells has been implicated in various autoimmune, inflammatory, and bone-destructive conditions, the exact role of T lymphocytes in chronic periodontitis is still controversial. Therefore, in this study we investigated the presence of Th17 cells in human periodontal disease.
Methods:  Gingival and alveolar bone samples from healthy patients and patients with chronic periodontitis were collected and used for the subsequent assays. The messenger RNA expression for the cytokines IL-17, TGF-β, IL-1β, IL-6, and IL-23 in gingiva or IL-17 and receptor activator for nuclear factor-κB ligand in alveolar bone was evaluated by real-time polymerase chain reaction. The production of IL-17, TGF-β, IL-1β, IL-6, and IL-23 proteins was evaluated by immunohistochemistry and the presence of Th17 cells in the inflamed gingiva was confirmed by immunofluorescence confocal microscopy for CD4 and IL-17 colocalization.
Results:  Our data demonstrated elevated levels of IL-17, TGF-β, IL-1β, IL-6, and IL-23 messenger RNA and protein in diseased tissues as well as the presence of Th17 cells in gingiva from patients with periodontitis. Moreover, IL-17 and the bone resorption factor RANKL were abundantly expressed in the alveolar bone of diseased patients, in contrast to low detection in controls.
Conclusion:  These results provided strong evidence for the presence of Th17 cells in the sites of chronic inflammation in human periodontal disease.     

An acute injection of Porphyromonas gingivalis lipopolysaccharide modulates the OPG/RANKL system and interleukin-6 in an ovariectomized mouse model

Background/aims:  In the present study, we attempted to develop a simulated model to explore the causal effects of periodontal pathogens on skeletal homeostasis in postmenopausal osteoporosis.
Methods:  Fifty-three female adult ICR mice were randomly assigned to an experimental group (ovariectomized) or a control group. A single injection of Porphyromonas gingivalis lipopolysaccharide ( P. gingivalis -LPS, ATCC 33277) or Escherichia coli lipopolysaccharide ( E. coli -LPS) was administered intraperitoneally 4 weeks after an ovariectomy. Concentrations of interleukin-6 (IL-6), osteoprotegerin (OPG), and the receptor activator of nuclear factor-κB ligand (RANKL) in serum were subsequently analyzed using an enzyme-linked immunosorbent assay (ELISA).
Results:  Under stimulation with P. gingivalis -LPS or E. coli -LPS, the concentration of OPG rose in both groups. The serum level of RANKL showed a decreasing trend 24 h after the injection in both groups. After injection of P. gingivalis -LPS in both the experimental and control animals, the OPG : RANKL ratio increased 24 h after the booster (22.26–620.99, P  < 0.05). The serum level of IL-6 in the experimental group significantly increased 1–6 h after administration of E. coli -LPS and 1–3 h after administration of P. gingivalis -LPS ( P  < 0.05).
Conclusions:  A single booster injection of P. gingivalis -LPS induced short-term changes in OPG, RANKL, and IL-6 serum levels in this ovariectomized mouse model.     

Comparative immunohistochemical expression of RANK, RANKL and OPG in radicular and dentigerous cysts

Objective

Receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG) are members of the superfamily of ligands and receptors of tumour necrosis factor family involved in bone metabolism. The formation, differentiation and activity of osteoclasts are regulated by these proteins. To clarify the roles of osteoclast regulatory factors in cystic expansion of odontogenic cysts, expression of these proteins were analysed in radicular and dentigerous cysts.

Design

The immunohistochemistry expression of these biomarkers were evaluated and measured in lining epithelium and fibrous capsule of the radicular (n = 20) and dentigerous cysts (n = 20).

Results

A similar expression in lining epithelium was observed in the lesions. The fibrous capsule of dentigerous cyst showed a higher content of RANK-positive and RANKL-positive cells than fibrous capsule of radicular cyst. In the lining epithelium the RANKL/OPG ratio showed higher numbers of OPG-positive than RANKL-positive cells, whereas fibrous capsule of the cysts had a tendency to present a similar expression (OPG = RANKL).

Conclusion

Ours findings indicate the presence of RANK, RANKL and OPG in cysts. Moreover, increased expression of OPG compared to RANKL in the lining epithelium could contribute to the differential bone resorption activity in theses lesions.     

抑制核因子-κB受体活化因子及其配体通路治疗牙周炎的研究进展

核因子-κB受体活化因子（RANK）及其配体（RANKL）在牙周炎患者的牙槽骨吸收中具有重要的作用,抑制RANKL／RANK通路,可有效抑制破骨细胞的分化和激活,从而抑制牙槽骨的吸收。骨保护蛋白（OPG）和RANKL结合,干扰RANKL和RANK的结合,从而防止骨组织的过度破坏。本文就RANKL／RANK／OPG轴、RANKL／RANK／OPG与牙周炎、抑制RANKL／RANK通路治疗牙周炎的可行性等研究进展作一综述。     

Expression of receptor activator of NF-kappa B ligand and osteoprotegerin in culture of human periodontal ligament cells

The receptor activator of NF-kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), are the important proteins implicated in osteoclastogenesis. In this study, we investigated the expressions of RANKL and OPG in cultured human periodontal ligament (PDL) cells and their roles in osteoclastogenesis. Northern blotting revealed that the OPG mRNA was down-regulated remarkably by application of 10-8 m one-alpha, 25-dihydroxyvitamin D3[1,25-(OH)2D3] and 10-7 m dexamethasone (Dex). In contrast, RANKL mRNA was up-regulated by the same treatment. Western blotting demonstrated decrease of OPG by the application of 1,25-(OH)2D3 and Dex. Tartrate-resistant acid phosphatase-positive multinuclear cells were markedly induced when the PDL cells were cocultured with mouse bone marrow cells in the presence of an anti-OPG antibody together with 1,25-(OH)2D3 and Dex. These results indicate that PDL cells synthesize both RANKL and OPG and that inactivation of OPG may play a key role in the differentiation of osteoclasts.     

MTA对牙周膜干细胞RANKL/OPG表达水平的影响

目的 探讨MTA对人牙周膜干细胞（periodontal ligament stem cells,PDLSCs）核因子-κB受体活化因子配体（receptor activator of NF-κB ligand,RANKL）、骨保护素（osteoprotegerin,OPG）表达的影响。方法 通过酶消化法分离培养PDLSCs,依据碱性磷酸酶（alkaline phosphatase,ALP）活性筛选最佳MTA刺激浓度,将PDLSCs分别于对照组（普通培养基）和2 mg/mL MTA条件培养液培养3 d和7 d后,蛋白免疫印迹法分别检测RANKL、OPG蛋白表达。结果 MTA刺激3 d和7 d组,OPG蛋白表达较对照组升高,RANKL蛋白表达较对照组降低。结论 MTA可通过调节RANKL/OPG系统,参与调节PDLSCs成牙/骨及破牙/骨活性。     

牙齿萌出过程中 RANKL mRNA 的表达与破骨细胞的关系

目的:探讨核因子κB受体活化剂配体 RANKL 在大鼠下颌第一磨牙牙胚冠方组织中 mRNA 的表达及破骨细胞的分化情况.方法:运用原位杂交法检测大鼠下颌第一磨牙牙胚冠方组织中 RANKL mRNA 的表达;TRAP 染色观察破骨细胞分化情况.结果:出生1、3、5、7 d大鼠下颌第一磨牙牙胚冠方牙囊成纤维细胞、成釉细胞 RANKL mRNA的阳性表达强于对照组牙龈成纤维细胞(p<0.01).大鼠下颌第一磨牙牙胚冠方出生后1 d破骨细胞多为单核,3 d时多核破骨细胞增多.结论:RANKL mRNA 在大鼠出生后1、3、5、7 d下颌第一磨牙牙囊成纤维细胞、成釉细胞中有表达,可能通过促进破骨细胞的分化及成熟参与牙齿的萌出.