慢性牙周炎中核因子κB受体活化子、护骨素和肿瘤坏死因子-α的蛋白表达

目的　比较慢性牙周炎牙槽骨吸收处肉芽组织中的核因子κB受体活化子 (RANKL)、护骨素 (OPG)和肿瘤坏死因子(TNF) -α的水平 ,研究慢性牙周炎牙槽骨吸收与这些调节因子间的关系。方法　应用鼠抗人单克隆抗体、半定量分析及数字成像技术分析慢性牙周炎组织中RANKL、OPG和TNF α的蛋白表达。结果　慢性牙周炎牙槽骨吸收处肉芽组织中有较高的RANKL和TNF α蛋白表达 ,OPG蛋白表达相对较低 (P <0 .0 5 ) ;非牙周炎组织中显示较强的OPG蛋白表达和较弱的RANKL和TNF -α蛋白水平 (P <0 .0 5 ) ;OPG蛋白表达与牙周组织中内皮细胞相关。结论　RANKL可能与慢性牙周炎牙槽骨吸收相关 ;RANKL和OPG平衡的变化在慢性牙周炎骨吸收的分子机制中起重要调节作用 ;TNF α可能协同参与牙槽骨的吸收     

壳寡糖对牙周炎大鼠牙槽骨吸收及Th17/Treg平衡和OPG/RANKL/RANK通路的影响

目的: 探讨壳寡糖对牙周炎大鼠牙槽骨吸收及Th17/Treg平衡和OPG/RANKL/RANK通路的影响。方法: 建立牙周炎大鼠模型,随机分为模型组、壳寡糖低剂量组、壳寡糖中剂量组、壳寡糖高剂量组和甲硝唑组,每组12只,另取12只作为对照组。分组处理后,评估牙龈指数、牙槽骨吸收值;H-E染色观察牙周组织病理形态学变化;流式细胞术检测外周血中Th17/Treg细胞比值;酶联免疫吸附试验（ELISA）检测各组大鼠血清中IL-17、TGF-β、RANKL、OPG水平,实时荧光定量PCR（qRT-PCR）检测各组大鼠牙周组织OPG、RANKL mRNA表达水平。采用SPSS 24.0软件包对数据进行统计学分析。结果: 与对照组相比,模型组大鼠牙周组织呈现牙周膜纤维束断裂、排列紊乱,毛细血管扩张、增生,炎症细胞浸润等病理损伤;牙龈指数、牙槽骨吸收值、Th17/Treg比值、血清RANKL及IL-17水平、牙周组织RANKL mRNA水平显著升高（P<0.05）,血清OPG及TGF-β水平、牙周组织OPG mRNA水平显著降低（P<0.05）。与模型组相比,壳寡糖低、中、高剂量组和甲硝唑组大鼠牙周组织病理损伤减轻;牙龈指数、牙槽骨吸收值、Th17/Treg比值、血清RANKL及IL-17水平、牙周组织RANKL mRNA水平显著降低（P<0.05）,血清OPG及TGF-β水平、牙周组织OPG mRNA水平显著升高（P<0.05）,且壳寡糖各组呈剂量依赖性,壳寡糖高剂量组与甲硝唑组相比,差异无统计学意义（P>0.05）。结论: 壳寡糖可促使Th17/Treg平衡恢复正常,上调OPG表达,下调RANKL表达,抑制牙周炎大鼠牙槽骨吸收,改善其临床症状。     

胰岛素治疗对糖尿病大鼠牙槽骨RANKL/OPG mRNA影响的研究

目的通过研究胰岛素治疗对糖尿病大鼠牙周组织病理改变及牙槽骨中NF-κB受体活化因子配体(Receptor activator of nuclear factor-κB ligand,RANKL)和骨保护素(osteoprotegerin,OPG)mRNA水平比值情况的影响,探讨糖尿病影响牙周病时牙槽骨吸收的机理。方法将12只大鼠采用静脉注射链脲佐菌素的方法建立糖尿病模型,并随机分为治疗组和对照组。治疗组给予胰岛素皮下注射,对照组注射等量生理盐水。分别于实验开始时、造模成功后和8周后处死时测量大鼠体重和血糖。右下磨牙区牙周组织脱钙后HE染色观察组织病变状况;应用RT-PCR检测左下磨牙区牙槽骨RANKL和OPG mRNA表达情况,并比较两组大鼠RANKL/OPG比值差异。结果胰岛素治疗组较糖尿病组牙周组织炎症反应减轻,牙槽骨吸收减弱;血糖值(P<0.05)及RANKL/OPGmRNA比值(P<0.01)降低。结论胰岛素治疗可能增加牙周组织修复和再生能力,降低糖尿病大鼠的牙槽骨RANKL/OPGmRNA比值。提示血糖水平增高可能是影响糖尿病大鼠的牙槽骨吸收危险因素之一。     

抗牙龈素粘附片段Hgp44卵黄抗体对实验性牙周炎的抑制作用

目的: 观察抗牙龈素粘附片段Hgp44卵黄抗体(抗Hgp44-IgY)对大鼠实验性牙周炎的抑制作用。方法: 24只雄性SD大鼠随机分为4组:空白组(A),生理盐水孵育组(B),抗Hgp44-IgY孵育组(C)和西吡氯铵孵育组(D)。采用细线结扎大鼠4颗第一磨牙,分别接种经处理的牙龈卟啉单胞菌,辅以蔗糖饮水。4周后检测大鼠牙龈指数(GI),龈下菌斑的BANA试验。处死大鼠后检测牙槽骨丧失量(ABL),牙龈的HE染色,利用qRT-PCR检测牙龈中IL-10、OPG和RANKL mRNA相对表达水平以及OPG/RANKL比率。结果: C组和D组与B组相比,GI、ABL以及BANA结果均显著降低(P<0.01),牙龈组织中IL-10和OPG的mRNA表达水平均显著增高(P<0.01),RANKL mRNA的表达水平显著下降(P<0.05),OPG/RANKL比率显著增高(P<0.001),C组与D组相比,GI、ABL、BANA、IL-10,OPG mRNA水平和OPG/RANKL比率无统计学意义,OPG mRNA 表达水平显著降低(P<0.05)。结论: 抗Hgp44-IgY能减少牙槽骨的吸收,减缓大鼠实验性牙周炎的发展进程。     

染料木素对牙周炎小鼠牙周组织的影响

目的 本研究旨在评估染料木素（genistein,GEN）对丝线结扎诱导的牙周炎小鼠牙槽骨吸收以及牙龈组织中炎症因子表达情况的影响。方法 以雄性C57小鼠为研究对象,采用丝线结扎法建立小鼠牙周炎模型,实验组给予GEN。4周后使用显微镜和ImageJ软件分析GEN对小鼠牙槽骨吸收情况的影响。并采用实时荧光定量PCR法检测GEN治疗后,牙周炎小鼠牙龈组织中肿瘤坏死因子（tumor necrosis factor-α,TNF-α）、白细胞介素-1β(interleukin-1β,IL-1β)、白细胞介素-6(interleukin-6,IL-6)以及白细胞介素17a(interleukin-17a,IL-17a)的mRNA表达情况。结果 给予GEN(20mg/kg和40mg/kg)治疗后,牙周炎小鼠的牙槽骨吸收明显少于无GEN治疗组（P <0.05）。并且GEN治疗小鼠牙龈组织中TNF-α、IL-1β、IL-6和IL-17a的mRNA表达亦显著降低（P <0.05）。结论 染料木素可显著减轻牙周炎导致的牙周组织破坏,有望成为一种新型的牙周炎治疗药物。     

NF-kB受体激活蛋白配体抗体抑制T细胞介导的牙周骨吸收

目的 通过牙周病动物模型,评价NF-KB受体激活蛋白配体(receptor activator of NF-κB ligand,RANKL)抗体对T细胞诱导的牙周骨吸收的作用.方法 经鼠尾静脉回输体外分离、纯化、扩增的T淋巴细胞,牙龈局部微量注射T细胞特异性抗原,形成牙周病动物模型,实验前1d及实验第1、3d,在牙龈同样部位注射不同浓度RANKL F(ab′)2抗体片段进行干预.酶联免疫吸附测定法检测血清中鼠抗兔IgG抗体水平及牙龈组织中可溶性RANKL( soluble RANKL,sRANKL)的表达水平；显微镜下测量上颌磨牙牙槽骨吸收；抗酒石酸酸性磷酸酶染色法测定牙槽骨表面破骨细胞的形成.结果 鼠牙周病模型经RANKL抗体干预后,小剂量抗体(0.015、0.15及1.5μg/鼠)不产生免疫性,与实验当天相比差异无统计学意义(P＞0.05)；高浓度组(10μg/鼠)在实验后7、10 d测得的血清中鼠抗兔IgG A405值分别为0.64 ±0.12及0.55±0.03,差异有统计学意义(P＜0.01),可产生明显的免疫反应；牙龈组织匀浆液中sRANKL的表达水平及牙槽骨吸收明显减少,除0.015 μg组与对照组相比差异无统计学意义外,其他浓度抗体组牙龈组织中sRANKL的表达水平(由279.11±19.32分别降至146.03±11.21、118.24±20.52、110.72±7.11)及牙槽骨吸收率(由20.83±0.78分别降至15.95±1.21、12.72±0.82、12.61±0.79)均明显减少,与对照组相比差异有统计学意义(P＜0.05)；牙槽骨表面的破骨样细胞数也明显减少[由(83.57±7.73)个/mm减少至(58.07±9.57)个/mm],抗体组与非抗体组相比差异有统计学意义(P＜0.05)；牙龈组织中RANKL的表达与牙周骨吸收呈显著正相关(r2 =0.995,P＜0.01).结论 RANKL抗体可通过减少RANKL的表达水平,直接阻断RANKL的作用,抑制T细胞诱导的牙周骨吸收.     

大鼠正畸牙移动压力侧牙槽骨中cathK、RANKL和OPG的表达

目的检测大鼠正畸牙移动压力侧cathK、RANKL和OPG蛋白表达变化及时间分布特点。方法选用80只6周龄SD雄性大鼠建立正畸牙移动模型,分别在加力后2d、5d、7d、10d和14d各处死16只大鼠。HE染色观察大鼠牙周组织的形态学变化;TRAP染色计数压力侧牙槽骨组织中的破骨细胞数量;免疫组化方法定位及相对定量检测压力侧牙槽骨中cathK、RANKL和OPG蛋白表达变化及时间分布特点。结果压力侧牙槽骨组织中的TRAP染色阳性破骨细胞计数随加力时间的增加而增加,第7d达到高峰,此后逐渐降低;压力侧牙槽骨组织中的cathK、RANKL和OPG蛋白的表达水平均随加力时间的增加而增加,第7d达到高峰,以后均逐渐降低。结论cathK、RANKL和OPG蛋白表达的变化规律与骨改建过程一致,与正畸牙移动骨改建过程中破骨细胞的分化、形成和功能密切相关。     

内毒素耐受对人牙龈上皮细胞分泌IL-1β、IL-6和IL-8的影响

目的:观察脂多糖(lipopolysaccharides,LPS)反复刺激细胞,诱导产生的内毒素耐受对人牙龈上皮细胞(human gingival epithelial cells,HGECs)分泌细胞因子IL-1β、IL-6和IL-8的影响。方法:采用1mg/L牙龈卟啉单胞菌(Porphyromonas gingivalis,P.gingivalis)LPS或1mg/L大肠杆菌(Escherichia coli,E.coli)LPS刺激HGECs 24h,洗涤细胞后,分别采用相同的LPS再次刺激24h,构建内毒素耐受模型。采用ELISA技术检测细胞条件培养液中IL-1β、IL-6和IL-8分泌水平的变化。结果:P.gingivalis LPS或E.coli LPS刺激HGECs 24h后,3种细胞因子的分泌水平均较刺激前明显增高(P<0.05)。2种LPS重复刺激,诱导细胞耐受后,IL-6和IL-8的分泌水平较第1次刺激后明显降低(P<0.05),但P.gingivalis LPS重复刺激后,IL-1β的分泌水平与第1次刺激后无明显差别。结论:内毒素耐受能抑制HGECs分泌细胞因子IL-6和IL-8,进而可能影响牙周组织的炎症和免疫反应。     

大鼠正畸压力侧牙槽骨改建中RANKL和OPG mRNA的表达

目的研究破骨细胞核因子kB受体活化因子配基（receptor activator nuclear factor kappa B ligand,RANKL）及其伪受体骨保护因子（osteoprotegerin,OPG）的mRNA在大鼠正畸牙移动压力侧牙槽骨改建中的表达变化及时问分布特点。方法选用80只6周龄SD雄性大鼠建立正畸牙移动模型,分别在加力后2d、5d、7d、10d和14d各处死16只大鼠。HE染色观察大鼠牙周组织的形态学变化;TRAP染色计数压力侧牙槽骨组织中的破骨细胞数量;实时定量PCR方法检测RANKL和OPGmRNA的表达变化及时问分布特点。结果骨改建的最活跃期为正畸加力后的第7d,压力侧牙槽骨组织中的TRAP染色阳性破骨细胞计数随加力时间的增加而增加,第7d达到高峰,而后逐渐降低。压力侧牙槽骨组织中的RANKL和OPGmRNA表达水平均随加力时间的增加而增加,第7d达到高峰,而后均逐渐降低。结论RANKL和OPG mRNA表达的变化规律不仅与骨改建过程一致,而且也与TRAP染色阳性破骨细胞数量的变化规律一致。RANKL和OPG与正畸牙移动骨改建过程中破骨细胞的分化、形成和功能密切相关。     

低能量激光对正畸力作用下牙周膜细胞骨改建相关因子mRNA表达的影响

目的 研究低能量激光对正畸张应力及压应力作用下人牙周膜细胞骨改建相关因子mRNA表达的影响.方法 培养人牙周膜细胞,模拟正畸加力,结合低能量激光照射,在不同条件下(激光、应力、激光+应力)培养6 h,通过Realtime PCR检测IL-1β、Runx2、OPN、OPG、RANKL mRNA的表达并计算RANKL/OPG的比值.结果 人牙周膜细胞在培养6 h后,IL-1β、Runx2、OPN、OPG、RANKL mRNA的表达都呈现出激光+应力组大于单纯应力组及单纯激光组.结论 模拟正畸加力及低能量激光照射均可使得人牙周膜细胞骨改建相关因子的表达量增加,两者可起到协同作用,促进正畸牙齿移动过程中的牙槽骨改建.     

IL-1β对人牙周膜成纤维细胞OPG、RANKL mRNA表达的影响

目的:以体外培养的人牙周膜成纤维细胞(HPDLF)为研究对象,观察不同浓度的白细胞介素-1β(IL-1β)对人牙周膜成纤维细胞(HPDLF)中骨保护素(OPG)、核因子κB受体活化剂配体(RANKL)mR-NA表达的影响。方法:组织块法体外原代培养HPDLF并鉴定,以第5代HPDLF作为实验靶细胞,分别用不同浓度(0、0.01、0.1、1、10、100 ng/mL)的IL-1β进行干预,半定量逆转录聚合酶链反应(RT-PCR)检测HPDLF中OPG、RANKL mRNA的表达。结果:IL-1β在0.01～10 ng/mL浓度范围内能明显上调HPDLF中OPG mRNA的表达(P<0.05),并在0.1 ng/mL时上调作用达到最大(P<0.05)。此后,随着IL-1β浓度的增加,OPG mRNA的表达量逐渐减少。IL-1β在0.01～100 ng/mL浓度范围内均可明显上调HPDLF中RANKL、RANKL/OPGmRNA的表达(P<0.05),且呈剂量依赖性,即随着IL-1β浓度增加,HPDLF中RANKL、RANKL/OPG mRNA的表达也逐渐增加,各浓度组两两比较除10 ng/mL与100 ng/mL相比无显著性差异外,其余各组间差异均有统计学意义(P<0.05)。结论:IL-1β可促进HPDLF中RANKL mRNA的表达,上调RANKL/OPG mRNA的比值。     

Cytokine pattern determines the progression of experimental periodontal disease induced by Actinobacillus actinomycetemcomitans through the modulation of MMPs, RANKL, and their physiological inhibitors

OBJECTIVE: Inflammatory and immune reactions raised in response to periodontopathogens are thought to trigger periodontal tissue destruction. We therefore investigated the expression of matrix metalloproteinases (MMPs) and the osteoclastogenic factor RANKL (receptor activator of nuclear factor-kappaB ligand), their respective inhibitors TIMPs (tissue inhibitors of metalloproteinases) and OPG (osteoprotegerin) and their possible correlation with the expression of inflammatory and regulatory cytokines in the course of experimental periodontal disease in mice. METHODS: We characterized the time course of leukocyte migration and alveolar bone loss in C57BL/6 mice infected with Actinobacillus actinomycetemcomitans. Quantitative polymerase chain reaction (RealTime PCR) and ELISA were performed to determine the expression of MMPs, TIMPs, RANKL, OPG and cathepsin K, interleukin-1beta, tumor necrosis factor-alpha, interferon-gamma, interleukin-12, interleukin-4 and interleukin-10 in periodontal tissue samples harvested throughout the course of experimental disease. RESULTS: Oral inoculation of A. actinomycetemcomitans results in an intense and widespread migration of leukocytes to the gingival tissues, besides marked alveolar bone resorption. Our data also demonstrate two distinct patterns of MMP/TIMP and RANKL/OPG expression in the course of experimental periodontal disease. The expression of MMPs (MMP-1, 2 and 9) and RANKL was correlated with the expression of interleukin-1beta, tumor necrosis factor-alpha and interferon-gamma, in a time period characterized by the intense increase of inflammatory reaction and alveolar bone loss. On the other hand, interleukin-4 and interleukin-10 were associated with higher expression of TIMPs (TIMP 1, 2 and 3) and OPG, with a lower expression of MMPs and RANKL, and with reduced rates of increase of cellular infiltration in periodontal tissues and alveolar bone loss. CONCLUSIONS: It is possible that the pattern of cytokines produced in periodontal tissues determines the progression and the severity of experimental periodontal disease, controlling the breakdown of soft and bone tissues through the balance between MMPs/TIMP and RANKL/OPG expression in gingival tissues.     

Prostaglandin E(2) is a main mediator in receptor activator of nuclear factor-kappaB ligand-dependent osteoclastogenesis induced by Porphyromonas gingivalis, Treponema denticola, and Treponema socranskii

BACKGROUND: Periodontitis is an inflammatory disease that often leads to destruction of alveolar bone; a number of bacteria in subgingival plaque are associated with bone destruction in periodontitis. To understand the mechanism of how periodontopathogens induce osteoclastogenesis, we determined which mediators are involved in the osteoclastogenesis. METHODS: We investigated effects of sonicates from three periodontopathic bacteria, Porphyromonas gingivalis, Treponema denticola, and Treponema socranskii, on osteoclast formation in a co-culture system of mouse calvaria-derived osteoblasts and bone marrow cells. The osteoclast formation was determined by tartrate resistant acid phosphatase (TRAP) staining. The expression of the receptor activator of nuclear factor-kappa B ligand (RANKL), prostaglandin E(2) (PGE(2)) and osteoprotegerin (OPG) in mouse calvaria-derived osteoblasts was determined by immunoassay. RESULTS: Each bacterial sonicate induced the osteoclast formation in the co-culture system. These bacterial sonicates increased the expression of RANKL and PGE(2), and decreased the expression of OPG in osteoblasts. The addition of OPG, an inhibitor of RANKL, in the co-culture completely suppressed the osteoclastogenesis that was stimulated by each bacterial sonicate. Indomethacin, which is an inhibitor of PGE(2) synthesis, reduced more than 88% of the osteoclast formation induced by each bacterial sonicate. Indomethacin inhibited more than 80% of RANKL expression in osteoblasts induced by T. denticola and T. socranskii, and 59% by P. gingivalis. Indomethacin completely recovered the depression of OPG expression in osteoblasts by T. denticola and T. socranskii to the level of the untreated osteoblasts. Indomethacin recovered the reduction of OPG expression by P. gingivalis to 67%. CONCLUSION: These findings suggest that the osteoclastogenesis by P. gingivalis, T. denticola, and T. socranskii is mediated by a RANKL-dependent pathway and that PGE(2) is a main factor in the pathway by the enhancing of RANKL expression and the depression of osteoprotegerin, a RANKL inhibitor.     

In vivo induction of proinflammatory cytokines in mouse tissue by Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans

Periodontitis is a chronic inflammatory disease initiated by a multitude of bacteria. Persistent infection leads to generation of various inflammatory mediators, resulting in tissue destruction and osteoclastic resorption of the alveolar bone. This study describes a novel in vivo murine calvarial model to assess the effects of oral pathogens on the expression of three proinflammatory cytokines [interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha] which are involved in bone resorption. We chose Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans as prototype oral pathogens. We also tested the effects of Streptococcus gordonii, an oral commensal supragingival microorganism, considered a non-pathogen. Live bacteria were injected into subcutaneous tissue overlying the parietal bone of mice calvaria for 6 days. At the end of the experimental period, tissues overlying the calvaria were removed and analyzed for proinflammatory cytokine expression by Northern blotting. Cytokine mRNA was not detected in the tissue over the calvaria of control animals. In contrast, P. gingivalis and A. actinomycetemcomitans elicited mRNA expression of all three cytokines, TNFalpha being the highest (TNFalpha > > IL-1beta > IL-6). P. gingivalis was more potent than A. actinomycetemcomitans in inducing cytokine expression. In contrast, S. gordonii induced only low levels of mRNA for IL-1beta and TNFalpha but no IL-6 mRNA induction. These results suggest that oral microorganisms with access to host tissues elicit a battery of proinflammatory cytokines. There were clear differences in profiles and, interestingly, a commensal bacterium also stimulated bone resorptive cytokine expression in host tissues.     

Local osteoprotegerin gene transfer to periodontal tissue inhibits lipopolysaccharide-induced alveolar bone resorption

Background and Objective:  Osteoclastogenesis is primarily activated by receptor activator of nuclear factor κB ligand (RANKL) and is inhibited by osteoprotegerin (OPG). A previous study demonstrated that local OPG gene transfer to periodontal tissue inhibited RANKL-mediated osteoclastogenesis and experimental tooth movement. In the present study, we tested the hypothesis that local OPG gene transfer to the periodontium can neutralize RANKL activity induced by lipopolysaccharide injection, thereby inhibiting osteoclastogenesis and diminishing alveolar bone resorption in experimental periodontal disease.
Material and methods:  Seven-week-old male Wistar rats received an injection of lipopolysaccharide or phosphate-buffered saline in the palatal gingiva of the upper first molars on both the right and left sides. An inactivated haemagglutinating virus of Japan (HVJ) envelope vector containing a mouse OPG expression plasmid [pcDNA3.1(+)-mOPG] or mock vector was injected periodically into the palatal periodontal tissue of the upper first molars.
Results:  Lipopolysaccharide injection induced severe periodontal bone resorption. Local OPG gene transfer induced OPG production, and osteoclastogenesis was inhibited. Local OPG gene transfer significantly decreased alveolar bone resorption.
Conclusion:  Osteoprotegerin gene transfer to periodontal tissue inhibited osteoclastogenesis and alveolar bone resorption in lipopolysaccharide-induced experimental 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.