Osteoclastogenesis inhibitory factor/osteoprotegerin in synovial fluid from patients with temporomandibular disorders

Histopathology of the temporomandibular joint disc: Findings in 30 samples from joints with degenerative disease

Aim

The aim of this study is to show the anatomical and histological features of the displaced temporomandibular joint (TMJ) disc in joints with degenerative disease.

Methods

This study was performed on a total of 30 TMJ discs extracted from 22 patients, who underwent surgical discectomy after failure of conservative non‐surgical treatment regimens to control pain and/or limited range of motion. All joints had imaging signs of an anteriorized disc position and degenerative joint disease. Samples of the extracted discs were stored in formalin, cut into 3 micron‐thick sections imbedded in paraffin and processed with hematoxylin‐eosin.

Result

All the samples present irreversible morphologic and histological alterations. The macroscopical evaluation showed that 14 discs were worn and fragmented in several parts, and one disc was perforated. Morphological alterations with deformation and degenerative signs were shown in all discs, which were all severely worn and compromised. Histologically, various alterations were found, such as pre‐fibrous sclerosis with myxoid degeneration and collagen deposits (N = 25), an increase in fibro‐hyaline and fibrous tissues, with loss of elasticity (N = 25), scattered calcifications (N = 15), and synovial inflammation with microvascular proliferation and increased cellularity, presence of lymphocytes, histiocytes and plasma cells (N = 18). After the intervention, all patients reported decreased pain levels and showed improved function at 6 months.

Conclusion

These observations suggest that degenerative joint disease is accompanied by a anteriorized discs featuring abnormal macroscopical and histological changes. From a clinical viewpoint, this may suggest that, when treatment escalation leads to consider TMJ surgery, total discectomy is the most reasonable approach.

Ahmad WMA, Ahmed Asif J, Khoo SP, Husein A, Ab-Ghani Z, Kassim NK. Biomarkers for Temporomandibular Disorders: Current Status and Future Directions

Numerous studies have been conducted in the previous years with an objective to determine the ideal biomarker or set of biomarkers in temporomandibular disorders (TMDs). It was recorded that tumour necrosis factor (TNF), interleukin 8 (IL-8), IL-6, and IL-1 were the most common biomarkers of TMDs. As of recently, although the research on TMDs biomarkers still aims to find more diagnostic agents, no recent study employs the biomarker as a targeting point of pharmacotherapy to suppress the inflammatory responses. This article represents an explicit review on the biomarkers of TMDs that have been discovered so far and provides possible future directions towards further research on these biomarkers. The potential implementation of the interactions of TNF with its receptor 2 (TNFR2) in the inflammatory process has been interpreted, and thus, this review presents a new hypothesis towards suppression of the inflammatory response using TNFR2-agonist. Subsequently, this hypothesis could be explored as a potential pain elimination approach in patients with TMDs.

OPG is Required for the Postnatal Maintenance of Condylar Cartilage

Osteoprotegerin (OPG) is one of the protective factors of bony tissue. However, the function of OPG in cartilage tissues remains elusive. The aim of this study is to explore the function of OPG in the postnatal maintenance and the occurring of osteoarthritis (OA) of temporomandibular joint (TMJ) in the rodent models. We found that OPG expressed in the hypertrophic layer of the condylar cartilage and upregulated in the hyperocclusion-induced-TMJ-trauma rat. In the absence of OPG, the cartilage degradation occurred prior to that in WT mice, and the 3-month-old OPG-Knockout (OPG-KO) condyle showed decreased chondrocyte proliferation and increased chondrocyte apoptosis, whereas the number of chondroclasts was comparable to WT condyle. The isolated chondrocytes from the OPG-KO mice also showed impaired survival and promoted chondrogenic differentiation. Furthermore, the hyperocclusion model deteriorated TMJ degradation in the OPG-KO mice. OPG plays a protective role in the condylar chondrocytes' survival, and it is required for the postnatal maintenance of TMJ.

Elastin‑derived peptides are involved in the processes of human temporomandibular disorder by inducing inflammatory responses in synovial cells

Temporomandibular joint dysfunction (TMD) is a collection of clinical symptoms that involve masticatory muscles and the temporomandibular joint (TMJ). Common symptoms include limited jaw motion and joint sound/pain, along with TMJ disc displacement. TMD is frequently associated with synovitis, a chronic inflammation of the synovium. Fibroblast-like synovial cells have been identified to produce several inflammatory mediators and may have an important role in the progression of TMJ inflammation. Degradation of the extracellular matrix molecule elastin may lead to the release of bioactive peptides. The present study aimed to explore the role of elastin-derived peptides (EDPs) in human temporomandibular disorders. Therefore, interleukin-6 (IL-6) expression in the synovial fluid obtained from patients with TMD correlated significantly with two clinical parameters, specifically TMJ locking and pain/jaw function on a visual analog scale (VAS). To the best of our knowledge, this is the first study to determine that the concentration of EDPs in synovial fluid from patients with TMD may also be significantly correlated with the duration of TMJ locking, the VAS score and IL-6 expression. In vitro, EDPs act on human TMJ synovial cells to promote upregulation of IL-6 and the elastin-degrading enzyme matrix metalloproteinase-12 (MMP-12). The upregulation of IL-6 and MMP-12 expression by EDPs may be mediated through elastin-binding proteins (EBP) and a protein kinase A signalling cascade. These findings suggest a model for inflammation in the TMJ where EDPs are generated by harmful mechanical stimuli, induce both a pro-inflammatory cascade and increase expression of MMP-12 through activation of the EBP signalling cascade. This may lead to further increases in EDP levels, establishing a positive feedback loop leading to chronic inflammation in the TMJ. Therefore, significantly elevated levels of EDPs and IL-6 in the synovial fluid of the TMJ may be indicators of the pathological conditions of the joint.

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.

Temporomandibular joint pain and synovial fluid analysis: a review of the literature

The pathophysiology of temporomandibular joint pain is not well understood. A significant amount of research has been conducted to evaluate synovial fluid in these patients and in healthy controls. Qualitative and quantitative analyses of the synovial fluid have shown a significant difference between these groups. A multitude of inflammatory mediators and degradation products have been identified. The concentration of these products has been shown to correlate with several clinical parameters including pain, chronicity, severity of degenerative change, and response to treatment. A common inflammatory pathway would appear to be involved in most patients. At the present time, synovial fluid analysis does not have the sensitivity or specificity to allow specific diagnoses and targeted treatment. Continued research with the specific aim of establishing more appropriate therapeutic modalities based on the biochemical pathways is warranted.

Bacterial diversity in synovial fluids of patients with TMD determined by cloning and sequencing analysis of the 16S ribosomal RNA gene

OBJECTIVE

The purpose of this study was to examine the presence of bacteria in synovial fluids from patients with temporomandibular joint disorder (TMD) by polymerase chain reaction (PCR) targeting the 16S ribosomal RNA (rRNA) gene, followed by cloning and sequencing.

STUDY DESIGN

Universal bacterial primers were used to amplify 16S rRNA genes in 28 synovial fluid samples from 27 patients with TMD (TMD group) as well as control subjects: 5 patients with dislocation of TMJ (non-TMD group). Subsequently, PCR amplicons were purified and cloned. Partial 16S rRNA sequences of the cloned insert were used to determine the species identities or closest relative by comparison with known sequences using GeneBank.

RESULTS

Nineteen (67.86%) of 28 samples from patients in the TMD group were identified with the presence of bacterial DNA by PCR. The 5 control samples from the nonTMD group were all negative in this study. After cloning and sequencing, a total of 11 bacterial species was detected, including Granulicatella adiacen (6 samples), Pseudomonas sp. (6 samples), Methylobacterium sp. (5 samples), and Beta proteobacterium (4 samples). Other species, such as Acidovorax sp., Bradyrhizobium sp., Sphingomonas, Streptococcus, Leptothrix sp. oral clone, Thiobacillus denitrificans, and Comamonadaceae bacterium, were also identified. Eight patients were found with mixed bacteria, with 2-4 bacteria per sample. The patients with fastidious bacteria such as Granulicatella adiacen and mixed bacteria were more likely to be older than 45 years (P < .05).

CONCLUSION

A wide variety of bacteria, including some not previously reported associated with TMD, were identified in the synovial fluids from patients with TMD.

p38 MAPK signaling in oral-related diseases

Multiple dental diseases are characterized by chronic inflammation, due to the production of cytokines, chemokines, and prostanoids by immune and non-immune cells. Membrane-bound receptors provide a link between the extracellular environment and the initiation of intracellular signaling events that activate common signaling components, including p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor (NF)-kappaB. Although ERK pathways regulate cell survival and are responsive to extracellular mitogens, p38 MAPK, JNK, and NF-kappaB are involved in environmental stress responses, including inflammatory stimuli. Over the past decade, significant advances have been made relative to our understanding of the fundamental intracellular signaling mechanisms that govern inflammatory cytokine expression. The p38 MAPK pathway has been shown to play a pivotal role in inflammatory cytokine and chemokine gene regulation at both the transcriptional and the post-transcriptional levels. In this review, we present evidence for the significance of p38 MAPK signaling in diverse dental diseases, including chronic pain, desquamative disorders, and periodontal diseases. Additional information is presented on the molecular mechanisms whereby p38 signaling controls post-transcriptional gene expression in inflammatory states.

Cytokine profile in synovial fluid from patients with internal derangement of the temporomandibular joint: a preliminary study

OBJECTIVES

Temporomandibular joint disorders (TMD) comprise a group of chronic painful conditions of mastication in the temporomandibular joint (TMJ). Although the association between TMD and internal derangement of the TMJ is well documented, the functional relevance is still unclear. Increased concentrations of inflammatory mediators have been identified in the synovial fluid of affected patients with TMD, suggesting an underlying degenerative or inflammatory process. The aim of this study was to generate a comprehensive cytokine expression profile in TMD.

METHODS

15 samples from patients with internal derangement of TMJ were analysed using a novel cytokine array that enables the analysis of 79 different cytokines simultaneously.

RESULTS

Cytokine levels were correlated with the presence of joint effusion (JE) determined by MRI. In the majority of synovial fluid samples, angiogenin (Ang), fibroblast growth factor (FGF)-9, insulin-like growth factor-binding protein (IGFBP)-3, interleukin (IL)-1alpha, IL-1beta, IL-8, inducible protein (IP)-10, macrophage inflammatory protein (MIP)-1beta, osteoprotegerin (OPG), transforming growth factor (TGF)-beta2, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, tumour necrosis factor (TNF)-beta and vascular endothelial growth factor (VEGF) were detectable. Furthermore, the expression levels of Ang, brain-derived neurotrophic factor (BDNF), FGF-4, FGF-9, IGFBP-2, IL-8, MIP-1beta, OPG, pulmonary and activation-regulated protein (PARC), TGF-beta2, TIMP-2 and VEGF were significantly associated with the presence of JE; among these, nine cytokines (Ang, BDNF, FGF-4, FGF-9, IGFBP-2, MIP-1beta, PARC, TGF-beta2 and TIMP-2) were hitherto not described in TMD.

CONCLUSIONS

This study confirmed previous reports of elevated cytokine levels in TMD. Additionally, we identified previously undescribed cytokines that were upregulated and correlated significantly with the presence of JE. We were able to identify novel cytokines that have hitherto not been described in TMD. Strategies targeting the identified cytokines may represent a novel therapy option in TMD.

IL-1 beta, IL-1 receptor antagonist and soluble type II IL-1 receptor in synovial fluid of patients with temporomandibular disorders

Among the members of the interleukin-1 (IL-1) family, IL-1 beta, which is a major agonist, has been detected in synovial fluid (SF) of the temporomandibular joint (TMJ) of patients with temporomandibular joint disorders (TMD). However, there is little knowledge regarding suppressive molecules, such as IL-1 receptor antagonist (IL-1ra) and the soluble form of type II IL-1 receptor (sIL-1RII), in TMD patients. The aim of this study was to investigate the levels of IL-1 beta, IL-1ra and sIL-1RII in the TMJ SF of patients with TMD and their relationship. Fifty-two SF samples from TMD patients and nine samples from asymptomatic volunteers were examined. Detected levels of IL-1 beta and sIL-1RII were significantly higher in the TMD group compared with the volunteer group. There was no significant difference in IL-1ra levels between the TMD and volunteer groups. The IL-1 beta/IL-1ra ratio in the TMD group, however, was higher than that in the volunteer group. In the TMD group, positive correlations were found between IL-1 beta and IL-1ra, IL-1ra and sIL-1RII, and IL-1 beta and sIL-1RII. In addition to increased IL-1 beta, development of TMD may also lead to decreased IL-1ra and increased sIL-1RII in response to increasing IL-1.