Serotype b of Aggregatibacter actinomycetemcomitans increases osteoclast and memory T‐lymphocyte activation

During periodontitis, alveolar bone resorption is associated with activation of T helper type 17 (Th17) lymphocytes and receptor activator of nuclear factor‐κB ligand (RANKL) ‐induced osteoclasts. We previously reported that serotype b of Aggregatibacter actinomycetemcomitans has a higher capacity to trigger Th17‐type differentiation and function in activated T lymphocytes and its lipopolysaccharide is a more potent immunogen compared with the other serotypes. This study aimed to investigate whether serotype b of A. actinomycetemcomitans induces higher Th17‐associated RANKL production, RANKL‐induced osteoclast activation, and antigen‐specific memory T lymphocyte proliferation. On naive CD4⁺ T lymphocytes stimulated with autologous dendritic cells primed with different A. actinomycetemcomitans serotypes, RANKL production, T‐bet, GATA‐3, RORC2 and Foxp3 expression, RORC2/RANKL intracellular double‐expression, TRAP⁺ osteoclast activation, and bone resorption were quantified. The frequency of proliferating memory T lymphocytes in response to A. actinomycetemcomitans serotypes was determined in periodontitis and healthy subjects. Naive CD4⁺ T lymphocytes stimulated by serotype b‐primed dendritic cells elicited higher levels of RANKL, RORC2, TRAP⁺ osteoclasts, and bone resorption than the same cells stimulated with the other serotypes. RANKL positively correlated and co‐expressed with RORC2. Memory T lymphocytes responding to serotype b were more frequently detected in periodontitis patients than healthy subjects. These results indicate that serotype b of A. actinomycetemcomitans is associated with higher production of RANKL and these increased levels are associated with Th17 lymphocyte induction, osteoclast activation, and bone resorption.     

Role of subchondral bone during early-stage experimental TMJ osteoarthritis

Temporomandibular joint osteoarthritis (TMJ OA) is a degenerative disease that affects both cartilage and subchondral bone. We used microarray to identify changes in gene expression levels in the TMJ during early stages of the disease, using an established TMJ OA genetic mouse model deficient in 2 extracellular matrix proteins, biglycan and fibromodulin (bgn(-/0)fmod(-/-)). Differential gene expression analysis was performed with RNA extracted from 3-week-old WT and bgn(-/0)fmod(-/-) TMJs with an intact cartilage/subchondral bone interface. In total, 22 genes were differentially expressed in bgn(-/0)fmod(-/-) TMJs, including 5 genes involved in osteoclast activity/differentiation. The number of TRAP-positive cells were three-fold higher in bgn(-/0)fmod(-/-) TMJs than in WT. Quantitative RT-PCR showed up-regulation of RANKL and OPG, with a 128% increase in RANKL/OPG ratio in bgn(-/0)fmod(-/-) TMJs. Histology and immunohistochemistry revealed tissue disorganization and reduced type I collagen in bgn(-/0)fmod(-/-) TMJ subchondral bone. Early changes in gene expression and tissue defects in young bgn(-/0)fmod(-/-) TMJ subchondral bone are likely attributed to increased osteoclast activity. Analysis of these data shows that biglycan and fibromodulin are critical for TMJ subchondral bone integrity and reveal a potential role for TMJ subchondral bone turnover during the initial early stages of TMJ OA disease in this model.     

Cytokines in healthy temporomandibular joint synovial fluid

Analysis of temporomandibular joint (TMJ) synovial fluid may elucidate the aetiology of temporomandibular disorders and arthritic conditions, as well as the inflammatory mechanisms involved. Knowledge about healthy synovial fluid is necessary to understand TMJ pathologies. We aimed to quantify the proinflammatory cytokines interleukin (IL)‐1β, IL‐2, IL‐6 and tumour necrosis factor (TNF), and the anti‐inflammatory cytokines IL‐10 and interferon (IFN)‐γ in healthy TMJ synovial fluid to serve as reference values for future studies on TMJ pathologies. Twenty healthy, young adult volunteers without temporomandibular dysfunction were included. Bilateral synovial fluid samples were obtained using the push‐pull technique with hydroxocobalamin described by Alstergren in 1999. Cytokines were quantified with Luminex multiplex assays and compared using nonparametric statistical analysis. No serious adverse effects were reported. Of 40 possible samples, 14 fulfilled the strict sampling criteria and were included in the analysis. Cytokine values (reported as medians with interquartile ranges) were as follows: TNF, 23 (13–37) pg mL^?1; IL‐2, 1·8 (0–22) pg mL^?1; and INF‐γ, 10 (0–47) pg mL^?1. IL‐1β, IL‐6 and IL‐10 were almost undetectable. In addition, TNF and INF‐γ cytokine levels correlated. We demonstrated that TNF was consistently detected and IFN‐γ and IL‐2 sporadically detected in the TMJ synovial fluid of healthy individuals using the hydroxocobalamin method and a multiplex assay. The cytokines IL‐10, IL‐1β and IL‐6 were barely detectable in this sample of healthy TMJs.     

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。     

Kinetics of Th17‐related cytokine expression in experimentally induced rat periapical lesions

Th17‐related cytokines are essential factors in various pathological states, including inflammatory bone destruction. This study investigated the contribution of Th17‐related cytokines to the progress of experimentally induced rat periapical lesions. Periapical pathoses were induced by unsealed exposure of the pulp chamber of the lower first molars. A variety of immunocompetent cells, including CD68⁺ macrophages, Ia antigen⁺ cells and TCRαβ⁺ T cells, were observed in the lesions. The expression levels of Th17‐related cytokines, IL‐17 and IL‐23, and of pro‐inflammatory cytokines, IL‐1β and IL‐6, were significantly increased at 14 days (expansion stage) compared with normal periapical tissues. The expression levels of Foxp3, a regulatory T cell (Treg)‐related gene, and of IL‐10, an anti‐inflammatory cytokine, were higher at 28 days (chronic stage) than at 14 days. These findings suggest that Th17‐related cytokines may be primary contributors to the initiation of periapical bone destruction, and that lesion expansion may be regulated by anti‐inflammatory mediators.     

Dry Extract of Matricaria recutita L. (Chamomile) Prevents Ligature‐Induced Alveolar Bone Resorption in Rats via Inhibition of Tumor Necrosis Factor‐α and Interleukin‐1β

Background: Matricaria recutita L. (chamomile) has demonstrated anti‐inflammatory activity. Accordingly, the ability of the Matricaria recutita extract (MRE) to inhibit proinflammatory cytokines and its influence on alveolar bone resorption (ABR) in rats. Methods: Wistar rats were subjected to ABR by ligature with nylon thread in the second upper‐left molar, with contralateral hemiarcade as control. Rats received polysorbate TW₈₀ (vehicle) or MRE (10, 30, and 90 mg/kg) 1 hour before ligature and daily until day 11. The periodontium was analyzed by macroscopy, histometry, histopathology, and immunohistochemistry for the receptor activator of nuclear factor‐kappa B ligand (RANKL), osteoprotegerin (OPG), and tartrate‐resistant acid phosphatase (TRAP). The gingival tissue was used to quantify the myeloperoxidase (MPO) activity and tumor necrosis factor (TNF)‐α and interleukin (IL)‐1β levels by enzyme‐linked immunosorbent assay. Blood samples were collected to evaluate bone‐specific alkaline phosphatase (BALP), leukogram, and dosages of aspartate and alanine transaminases, urea, and creatinine. Aspects of liver, kidneys, spleen, and body mass variations were also evaluated. Results: The 11 days of ligature induced bone resorption, low levels of BALP, leukocyte infiltration; increase of MPO, TNF‐α, and IL‐1β; immunostaining increase for RANKL and TRAP; reduction of OPG and leukocytosis, which were significantly prevented by MRE, except for the low levels of BALP and the leukocytosis. Additionally, MRE did not alter organs or body weights of rats. Conclusion: MRE prevented the inflammation and ABR by reducing TNF‐α and IL‐1β, preventing the osteoclast activation via the RANKL–OPG axis, without interfering with bone anabolism.     

Increase in RANKL: OPG ratio in synovia of patients with temporomandibular joint disorder

Although a recent study suggested the involvement of RANKL and osteoprotegerin (OPG) in the pathogenesis of bone-destructive disease, no study has focused on the RANKL:OPG ratio in the synovial fluid of patients with temporomandibular joint (TMJ) disorder. This communication reports on the concentrations of RANKL and OPG in synovial fluid from TMJ patients and healthy control individuals. In contrast to an unchanged concentration of RANKL, a strong decrease in the concentration of OPG was detected in the synovial fluid from patients with TMJ internal derangement. Treatment with the synovial fluid of osteoarthritis (OA) patients resulted in the high production of osteoclast-like cells from blood mononuclear cells in vitro, as well as in pit formation in dentin slices. The addition of anti-RANKL IgG or OPG attenuated OA-synovial fluid-induced osteoclast formation, suggesting that the increase in the RANKL:OPG ratio in the microenvironment of the joint has the potential to induce osteoclastogenesis in TMJ osteoarthritis.     

Simultaneous analysis of T helper subsets (Th1, Th2, Th9, Th17, Th22, Tfh,Tr1 and Tregs) markers expression in periapical lesions reveals multiple cytokine clusters accountable for lesions activity and inactivity status

Previous studies demonstrate that the balance between pro- and anti-inflammatory mediators determines the stable or progressive nature of periapical granulomas by modulating the balance of the osteoclastogenic factor RANKL and its antagonist OPG. However, the cytokine networks operating in the development of periapical lesions are quite more complex than what the simple pro- versus anti-inflammatory mediators'' paradigm suggests. Here we simultaneously investigated the patterns of Th1, Th2, Th9, Th17, Th22, Thf, Tr1 and Tregs cytokines/markers expression in human periapical granulomas.

Methods

The expression of TNF-α, IFN-γ, IL-17A, IL23, IL21, IL-33, IL-10, IL-4, IL-9, IL-22, FOXp3 markers (via RealTimePCR array) was accessed in active/progressive (N=40) versus inactive/stable (N=70) periapical granulomas (as determined by RANKL/OPG expression ratio), and also to compare these samples with a panel of control specimens (N=26). A cluster analysis of 13 cytokine levels was performed to examine possible clustering between the cytokines in a total of 110 granulomas.

Results

The expression of all target cytokines was higher in the granulomas than in control samples. TNF-α, IFN-γ, IL-17A and IL-21 mRNA levels were significantly higher in active granulomas, while in inactive lesions the expression levels of IL-4, IL-9, IL-10, IL-22 and FOXp3 were higher than in active granulomas. Five clusters were identified in inactive lesion groups, being the variance in the expression levels of IL-17, IL-10, FOXp3, IFN-γ, IL-9, IL-33 and IL-4 statistically significant (KW p<0.05). Three clusters were identified in active lesions, being the variance in the expression levels of IL-22, IL-10, IFN-γ, IL-17, IL-33, FOXp3, IL-21 and RANKL statistically significant (KW p<0.05).

Conclusion

There is a clear dichotomy in the profile of cytokine expression in inactive and active periapical lesions. While the widespread cytokine expression seems to be a feature of chronic lesions, hierarchical cluster analysis demonstrates the association of TNF-α, IL-21, IL-17 and IFN-γ with lesions activity, and the association of FOXP3, IL-10, IL-9, IL-4 and IL-22 with lesions inactivity.     

Green tea catechin inhibits lipopolysaccharide-induced bone resorption in vivo

Nakamura H, Ukai T, Yoshimura A, Kozuka Y, Yoshioka H, Yoshinaga Y, Abe Y, Hara Y. Green tea catechin inhibits lipopolysaccharide‐induced bone resorption in vivo. J Periodont Res 2009; doi: 10.1111/j.1600‐0765.2008.01198.x. © 2009 John Wiley & Sons A/S Background and Objective: Bone resorption is positively regulated by receptor activator of nuclear factor‐κB ligand (RANKL). Pro‐inflammatory cytokines, such as interleukin (IL)‐1β, promote RANKL expression by stromal cells and osteoblasts. Green tea catechin (GTC) has beneficial effects on human health and has been reported to inhibit osteoclast formation in an in vitro co‐culture system. However, there has been no investigation of the effect of GTC on periodontal bone resorption in vivo. We therefore investigated whether GTC has an inhibitory effect on lipopolysaccharide (LPS)‐induced bone resorption. Material and Methods: Escherichia coli (E. coli) LPS or LPS with GTC was injected a total of 10 times, once every 48 h, into the gingivae of BALB/c mice. Another group of mice, housed with free access to water containing GTC throughout the experimental period, were also injected with LPS in a similar manner. Results: The alveolar bone resorption and IL‐1β expression induced by LPS in gingival tissue were significantly decreased by injection or oral administration of GTC. Furthermore, when GTC was added to the medium, decreased responses to LPS were observed in CD14‐expressing Chinese hamster ovary (CHO) reporter cells, which express CD25 through LPS‐induced nuclear factor‐κB (NF‐κB) activation. These findings demonstrated that GTC inhibits nuclear translocation of NF‐κB activated by LPS. In addition, osteoclasts were generated from mouse bone marrow macrophages cultured in a medium containing RANKL and macrophage colony‐stimulating factor with or without GTC. The number of osteoclasts was decreased in dose‐dependent manner when GTC was added to the culture medium. Conclusion: These results suggest that GTC suppresses LPS‐induced bone resorption by inhibiting IL‐1β production or by directly inhibiting osteoclastogenesis.     

Expression of proinflammatory cytokines in osteoarthritis of the temporomandibular joint

OBJECTIVE: This study reports the expression of proinflammatory cytokines in temporomandibular joint (TMJ) of patients affected with temporomandibular osteoarthritis (OA). DESIGN: In twelve OA of the TMJ (OA-TMJ) affected patients and in six healthy volunteer subjects studied as control, the expression of IL1beta (interleukin-1beta), IL2, IL4, IL5, IL6, IL10, IL12p35, IL12p40, IL17, IFNgamma (interferon-gamma), TNFalpha (tumor necrosis factor-alpha), and TNFbeta mRNAs was evaluated. Using quantitative real-time RT-PCR technique, the cytokine levels, reported as Ct (cycle threshold), DeltaCt (Ct cytokine-Ct 18S rRNA) and RQ (relative quantification), in patient and control groups were compared. RESULTS: Expression of IL1beta, IL2, IL12p35, IL12p40, IL17, TNFalpha, TNFbeta, and IFNgamma mRNAs was significantly higher in patients as compared with controls. In particular, IL12 was the predominant cytokine expressed in patients (IL12p35 RQ=30.2 and IL12p40 RQ=29.0). Conversely, IL10 mRNA levels were higher in controls (RQ=1.8). CONCLUSIONS: These data suggest that not only IL1beta, IFNgamma, and TNFalpha but also IL10, IL12, and IL17 are involved in the OA-TMJ pathogenesis. Furthermore, an inflammatory response characterised by the predominant expression of IL12 mRNA and down-regulated expression of IL10 mRNA is associated with the degenerative changes observed in OA-TMJ.     

RANKL-independent modulation of osteoclastogenesis

Osteoclasts are functional cells required for bone resorption. They are derived from hematopoietic precursors and undergo a series of differentiation and fusion steps in response to various humoral factors. Depending on the importance in osteoclastogenesis, the pathways for the differentiation of hematopoietic precursors to mature osteoclasts can be divided into two categories: canonical and the non-canonical. Receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast formation is considered as an important canonical pathway. Non-canonical pathways of osteoclastogenesis mainly involve several humoral factors that can substitute for RANKL to induce osteoclast formation. Among these factors, tumor necrosis factor (TNF)-α, interleukin (IL)-1, “homologous to lymphotoxins, exhibiting inducible expression, and competing with herpes simplex virus glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes” (LIGHT), a proliferation-inducing ligand (APRIL), and B cell-activating factor (BAFF) belong to the TNF superfamily. Other RANKL substitutes are primarily cytokines and growth factors including transforming growth factor β (TGFβ), IL-6, IL-11, nerve growth factor (NGF), insulin-like growth factor (IGF)-I, and IGF-II. In this review, we summarize the involvement of these factors in inducing osteoclastogenesis in vitro. Although these factors weakly induce osteoclast formation, they may play a major role in pathological bone resorption.     

缺氧与加力在正畸骨吸收作用中的细胞学研究

目的 观察缺氧对正畸压力侧破骨细胞形成的影响,探讨缺氧、加力在正畸骨改建中各自所起的作用,并分析其在破骨细胞形成过程中的相互作用关系.方法 建立人牙周膜细胞与外周血单个核细胞接触式共培养模型,模拟正畸缺氧、加力、缺氧+加力,不同条件作用1、3、6h后培养3d,TRAP染色检测破骨样细胞的形成.Reahime PCR检测骨改建相关因子HIF-1α 、IL-1β、RANKL、OPGmRNA的表达并计算RANKL/OPG比值.结果 TRAP染色阳性细胞在缺氧+加力组各个处理时间段都有出现,缺氧组则在处理3、6h中出现,加力组仅在处理6h中出现,且缺氧+加力组的阳性细胞数目均大于单独缺氧、加力组.HIF-1α、IL-1β、RANKL、OPGmRNA的表达及RANKL/OPG比值都呈现出缺氧+加力组均大于单纯缺氧、加力组.结论 缺氧和加力分别可以诱导与人牙周膜细胞共培养的单个核细胞向破骨细胞分化,缺氧和加力相互协同、共同促进正畸牙齿移动过程中骨吸收的发生.     

Effect of bisphosphonates on human gingival fibroblast production of mediators of osteoclastogenesis: RANKL,osteoprotegerin and interleukin‐6

Tipton DA, Seshul BA, Dabbous MKh. Effect of bisphosphonates on human gingival fibroblast production of mediators of osteoclastogenesis: RANKL, osteoprotegerin and interleukin‐6. J Periodont Res 2011; 46: 39–47.© 2010 John Wiley & Sons A/S Background and Objective: Osteonecrosis of the jaw (ONJ) is associated with bisphosphonate (BP) therapy. BPs alter osteoblast production of mediators of osteoclastogenesis, including interleukin (IL)‐6, RANKL and osteoprotegerin (OPG), a RANKL antagonist. This can inhibit bone turnover and lead to necrosis. There is little information on the contribution of gingival fibroblasts, near bone‐resorption sites, to the IL‐6/RANKL/OPG network, the effects of BPs, or fibroblast involvement in ONJ pathogenesis. Therefore, the objective of this study was to determine the effects of alendronate and pamidronate on the constitutive production, or the lipopolysaccharide (LPS)‐ or IL‐1β‐stimulated production, of IL‐6, RANKL and OPG by human gingival fibroblasts. Material and Methods: Human gingival fibroblasts were derived from explants obtained from healthy individuals with noninflamed gingiva. Cytotoxicity was determined by measuring the activity of a mitochondrial enzyme. Fibroblasts were pre‐incubated or not with BPs (0.01 nm–1 μm ), then incubated or not with LPS or IL‐1β. The concentrations of IL‐6, OPG and RANKL were measured using ELISA. Data were analyzed using analysis of variance (ANOVA) and Scheffé’s F procedure. Results: LPS and BPs were not cytotoxic. The cells produced IL‐6, OPG and RANKL, all of which were stimulated by IL‐1β or LPS (p ≤ 0.04). BPs generally increased the production of IL‐6 and OPG (p ≤ 0.04) and decreased the production of RANKL (p ≤ 0.02). BPs generally further increased the production of LPS‐ or IL‐1β‐stimulated IL‐6 (p ≤ 0.04) and had no effect on, or further increased, the production of LPS‐ or IL‐1β‐stimulated OPG (p ≤ 0.04). BPs decreased the production of LPS‐ or IL‐1β‐stimulated RANKL (p ≤ 0.04) and decreased constitutive, LPS‐stimulated and IL‐1β‐stimulated RANKL/OPG ratios (p ≤ 0.02). Conclusion: The action of alendronate and pamidronate on human gingival fibroblasts, through altering the production of RANKL and OPG, appears to contribute to a microenvironment favoring the inhibition of bone resorption and ONJ.     

CSF-1, RANKL and OPG regulate osteoclastogenesis during murine tooth eruption

During tooth eruption, osteoclast-mediated bone resorption predominates in alveolar bone along the occlusal surface rather than in bone basal to the tooth. CSF-1, RANKL and OPG, regulatory molecules essential for osteoclastogenesis, are expressed during eruption. However, it is unclear if these cytokines exhibit an expression pattern that correlates with sites of osteoclastogenesis in vivo. To address this issue, mouse mandibles, isolated from 1 to 14 days postnatal, were analysed for osteoclast activity using tartrate-resistant acid phosphatase (TRAP) staining as well as colony-stimulating factor-1 (CSF-1), receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG) mRNA expression using in situ hybridisation. Results showed that CSF-1, RANKL and OPG are expressed in a distinct temporal and spatial manner. In the occlusal region, osteoclast activity was maximal at day 5 and correlated with a relative high expression of CSF-1 and RANKL compared to OPG. In basal bone at this time point, osteoclast activity decreased despite persistent CSF-1 expression and was associated with increased expression of OPG compared to RANKL. By day 8, osteoclastogenesis declined and correlated with upregulation of OPG at the occlusal and basal regions, with this effect continuing throughout eruption. These findings suggest that the spatiotemporal pattern and relative abundance of CSF-1, RANKL and OPG during eruption are key determinants of site-specific osteoclast activity in bone surrounding the tooth. Targeting these cytokines to specific regions in alveolar bone may provide a mechanism for regulating osteoclastogenesis in dental disorders associated with altered tooth eruption.     

Facilitation of bone resorption activities in synovial lavage fluid patients with mandibular condyle fractures

The aim of this study was to investigate the bone resorption effect of the mediators delivered in joint cavity of patients with mandibular condyle fractures by detecting osteoclast markers using cellular biochemistry methods, and by analysing bone resorption activities via inducing osteoclast differentiation of the infiltrated cells from arthrocentesis. Sixteen joints in 10 patients with mandibular condyle fractures were evaluated. The control group consisted of synovial fluid (SF) samples from seven joints of four volunteers who had no clinical signs or symptoms involving the temporomandibular joint (TMJ) or disc displacement. We collected SF cells from all patients during therapeutic arthrocentesis. The infiltrating cells from TMJ SF were cultured, differentiated into tartrate‐resistant acid phosphatase (TRAP)‐positive osteoclast‐like cells and examined bone resorption activities. We also investigated factors related to osteoclast induction of SF, using ELISA procedures. Osteoclast‐like cells were induced from the SF cells obtained from all patients with condylar fractures. These multinucleated giant cells were positive for TRAP and actin, and had the ability to absorb dentin slices. The levels of macrophage colony‐stimulating factor (M‐CSF), prostaglandin E2 (PGE2), soluble form of receptor activator of nuclear factor kappa‐B ligand (sRANKL) and osteoprotegerin (OPG), in SF samples from the patients, were significantly higher than in the controls. These findings indicate that bone resorption activities in SF from patients with mandibular condyle fractures were upregulated and may participate in the pathogenesis and wound healing.     

Bone mineral density,bone microstructure,and bone turnover markers in females with temporomandibular joint osteoarthritis

Objective

The pathogenesis of the temporomandibular joint osteoarthritis (TMJ OA) has not been clearly revealed. This study aimed to investigate the pathogenesis of TMJ OA based on bone metabolism.

Methods

Fifty-nine young (mean age 23.4 ± 3.4 years) and 41 post-menopausal females (mean age 57.2 ± 4.6 years) were enrolled. Areal bone mineral density (aBMD) was measured via dual-energy X-ray absorptiometry of the lumbar spine, femoral neck, total hip, and ultradistal radius. Levels of four bone resorption markers, serum ionized calcium and C-telopeptide of type I collagen (CTx) and urinary N-telopeptide of type I collagen and deoxypyridinoline, two bone formation markers, serum bone alkaline phosphatase and osteocalcin, and serum 25-dihydroxyvitamin D were analyzed at baseline and after 12 months. Condylar bone quality was assessed by 3D reconstructed CT images.

Results

Significant differences in condylar bone quality and aBMDs of the lumbar spine in accordance with TMJ OA stages were observed in young and post-menopausal females. The level of CTx was significantly associated with the development and progression of TMJ OA only in young females, whereas 25-dihydroxyvitamine D demonstrated significant associations in young and post-menopausal females. Progression of TMJ OA was accompanied by reduced condylar bone quality and concomitant with lower lumbar spine aBMDs in young and post-menopausal females.

Conclusion

Bone metabolism and condylar quality might be involved in the development and progression of TMJ OA.

Clinical relevance

CTx could be considered as a potential diagnostic and monitoring marker in young females, and vitamin D showed a therapeutic potential for TMJ OA.

     

T-helper 17 cells mediate the osteo/odontoclastogenesis induced by excessive orthodontic forces

Oral Diseases (2012) 18 , 375–388 Objective: The aim of this study was to investigate how T‐helper 17 cells (Th17 cells), interleukin (IL)‐17, and interleukin‐6 contribute to root resorption during orthodontic tooth movement. Materials and Methods: Fifteen male 6‐week‐old Wistar rats were subjected to orthodontic force of 10 or 50 g to induce a mesially tipping movement of the upper first molars for 7 days. The expression levels of TRAP, IL‐17, the IL‐17 receptor (IL‐17R), and IL‐6 proteins were determined in periodontal ligament (PDL) by immunohistochemical analysis. Moreover, the fluorescent localization immunoassay was performed to detect Th17 cells. Furthermore, the effects of IL‐17 on IL‐6 release were investigated using human PDL cells in vitro. The effect of IL‐17 on osteoclastogenesis was evaluated by TRAP staining, actin ring staining, and the pit formation assay. Results: The immunoreactivity for Th17, IL‐17, IL‐17R, and IL‐6 was detected in PDL tissue subjected to the orthodontic force on day 7. IL‐17 increased the release of IL‐6 from human periodontal ligament cells in a time‐dependent manner. Moreover, IL‐17 stimulated osteoclastogenesis from human osteoclast precursor cells, and these effects were partially suppressed by an anti‐IL‐6 antibody. Conclusion: These results suggest that Th17 cells may aggravate the process of orthodontically induced inflammatory root resorption.     

Td92, an outer membrane protein of Treponema denticola,induces osteoclastogenesis via prostaglandin E2‐mediated RANKL/osteoprotegerin regulation

Kim M, Jun H‐K, Choi B‐K, Cha J‐H, Yoo Y‐J. Td92, an outer membrane protein of Treponema denticola, induces osteoclastogenesis via prostaglandin E₂‐mediated RANKL/osteoprotegerin regulation. J Periodont Res 2010; 45: 772–779. © 2010 John Wiley & Sons A/S Background and Objective: Periodontitis is a chronic inflammatory disease of the periodontium that causes significant alveolar bone loss. Osteoclasts are bone‐resorbing multinucleated cells. Osteoblasts regulate osteoclast differentiation by expression of RANKL and osteoprotegerin (OPG). Td92 is a surface‐exposed outer membrane protein of Treponema denticola, a periodontopathogen. Although it has been demonstrated that Td92 acts as a stimulator of various proinflammatory mediators, the role of Td92 in alveolar bone resorption remains unclear. Therefore, in this study, we investigated the role of Td92 in bone resorption. Material and Methods: Mouse bone marrow cells were co‐cultured with calvariae‐derived osteoblasts in the presence or absence of Td92. Osteoclast formation was assessed by TRAP staining. Expressions of RANKL, osteoprotegerin (OPG) and prostaglandin E₂ (PGE₂) in osteoblasts were estimated by ELISA. Results: Td92 induced osteoclast formation in the co‐cultures. In the osteoblasts, RANKL and PGE₂ expressions were up‐regulated, whereas OPG expression was down‐regulated by Td92. The addition of OPG inhibited Td92‐induced osteoclast formation. The prostaglandin synthesis inhibitors NS398 and indomethacin were also shown to inhibit Td92‐induced osteoclast formation. The effects of Td92 on the expressions of RANKL, OPG and PGE₂ in osteoblasts were blocked by NS398 or indomethacin. Conclusion: These results suggest that Td92 promotes osteoclast formation through the regulation of RANKL and OPG production via a PGE₂‐dependent mechanism.