Oral and Maxillofacial Pathology: Interleukin-1 β, interleukin-6, and tissue inhibitor of metalloproteinase-1 in the synovial fluid of the temporomandibular joint with respect to cartilage destruction

Genetic Influences of Proinflammatory Cytokines on Pain Severity in Patients with Temporomandibular Disorders

This case-control study investigated single nucleotide polymorphism (SNP) genotypes (CXC motif chemokine ligand 8 (CXCL8): rs2227306 and rs2227307 and tumor necrosis factor (TNF): rs1800629) in 85 patients with pain-related temporomandibular disorders (TMDp) and 85 controls to explore their associations with TMDp presence, pain intensity (low/high), and the presence of chronic arthralgia/myalgia. TMDp was diagnosed using a validated protocol, and polymorphisms were genotyped from buccal mucosa swabs using TaqMan assays. High pain intensity individuals had an increased risk for carrying minor allele "G" (rs2227307) and "T" (rs2227306) compared to controls (76% vs. 55.3%, p = 0.012; 72% vs. 54.1%, p = 0.030, respectively). Carriers of the minor allele "G" (rs2227307) were more prevalent in TMDp patients with arthralgia compared to controls (70.30% vs. 55.30%, p = 0.037). According to logistic regression, the most important predictors for high pain intensity were minor allele "G" of rs2227307 (OR 2.435, 95% CI 1.123-5.282), increasing age (OR 1.038, 95% CI 1.002-1.075), and female sex (OR 4.592, 95% CI 1.289-16.361). The explored gene polymorphisms were not significant risk factors for TMDp presence. These findings highlight the importance of genetic variations, particularly rs2227307, in understanding the diverse clinical manifestations of temporomandibular disorders.

A Randomized Controlled Trial Evaluating the Levels of the Biomarkers hs-CRP, IL-6, and IL-8 in Patients with Temporomandibular Disorder Treated with LLLT, Traditional Conservative Treatment, and a Combination of Both

Temporomandibular disorders (TMDs) are a type of idiopathic orofacial pain. Inflammation, particularly elevated circulating levels of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), and interleukin-8 (IL-8), has been linked to pain symptoms. The purpose of this study was to compare hs-CRP, IL-6, and IL-8 biomarkers and pain intensity with different treatment strategies (LLLT, standard conservative treatment, and combination) for TMD patients. Methods: A total of 32 participants were randomly included in the study and divided into three groups (Group I, Group II, and Group III) referred from the Dental Clinic, School of Dental Science, HUSM. Patients received LLLT (Groups II and III) in five sessions for the duration of 10 days. Patients in Groups I and III received standard conservative TMD treatment (diet and stress counseling, jaw exercises, physical therapy, which was a hot towel application) by the principal investigator. All blood samples for biomarkers were performed before starting treatments and directly after finishing the treatment protocols, where all results were recorded. Results: The result showed a significant difference in the mean IL-8 (p = 0.001) between the three intervention groups (LLLT, standard treatment, and combined treatment). IL-6 showed an increase in the mean of IL-6 levels from baseline to post-treatment with a better mean in the LLLT treatment group without any significant differences. Additionally, there were no significant mean differences found between the groups and in the group for the hs-CRP biomarker. Conclusions: A statistically non-significant difference was found in hs-CRP and IL-6 before and after LLLT, conservative, and combined treatment strategies of TMD. A statistically significant difference was observed in the mean levels of IL-8 between the LLLT intervention group and the combined treatment group. Although there was no statistically significant correlation between pain intensity and biomarkers, a statistically significant difference was found in pain intensity before and after LLLT, conservative, and combined treatment strategies. TMJ degeneration could be exacerbated by elevated IL-8 levels. Thus, this can be an important biomarker to mark or identify the painful condition of TMJ.

Evidence That a TRPA1-Mediated Murine Model of Temporomandibular Joint Pain Involves NLRP3 Inflammasome Activation

This study investigates the role of transient receptor potential ankyrin 1 (TRPA1) in murine temporomandibular joint (TMJ) inflammatory hyperalgesia and the influence of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome. Two distinct murine models of TMJ pain and inflammation (zymosan and CFA) were established. Spontaneous pain-like behaviours were observed as unilateral front paw cheek wipes. Ipsilateral cheek blood flow was used as a measure of ongoing inflammation, which, to our knowledge, is a novel approach to assessing real-time inflammation in the TMJ. Joint tissue and trigeminal ganglia were collected for ex vivo investigation. Both zymosan and CFA induced a time-dependent increase in hyperalgesia and inflammation biomarkers. Zymosan induced a significant effect after 4 h, correlating with a significantly increased IL-1β protein expression. CFA (50 µg) induced a more sustained response. The TRPA1 receptor antagonist A967079 significantly inhibited hyper-nociception. The NLRP3 inhibitor MCC950 similarly inhibited hyper-nociception, also attenuating inflammatory markers. In the trigeminal ganglia, CFA-induced CGRP expression showed trends of inhibition by A967079, whilst lba1 immunofluorescence was significantly inhibited by A967079 and MCC950, where the effect of TRPA1 inhibition lasted up to 14 days. Our results show that stimulation of TRPA1 is key to the TMJ pain. However, the inflammasome inhibitor exhibited similar properties in attenuating these pain-like behaviours, in addition to some inflammatory markers. This indicates that in addition to the therapeutic targeting of TRPA1, NLRP3 inhibition may provide a novel therapeutic strategy for TMJ inflammation and pain.

A comprehensive review on biomarkers associated with painful temporomandibular disorders

Pain of the orofacial region is the primary complaint for which patients seek treatment. Of all the orofacial pain conditions, one condition that possess a significant global health problem is temporomandibular disorder (TMD). Patients with TMD typically frequently complaints of pain as a symptom. TMD can occur due to complex interplay between peripheral and central sensitization, endogenous modulatory pathways, and cortical processing. For diagnosis of TMD pain a descriptive history, clinical assessment, and imaging is needed. However, due to the complex nature of pain an additional step is needed to render a definitive TMD diagnosis. In this review we explicate the role of different biomarkers involved in painful TMD. In painful TMD conditions, the role of biomarkers is still elusive. We believe that the identification of biomarkers associated with painful TMD may stimulate researchers and clinician to understand the mechanism underlying the pathogenesis of TMD and help them in developing newer methods for the diagnosis and management of TMD. Therefore, to understand the potential relationship of biomarkers, and painful TMD we categorize the biomarkers as molecular biomarkers, neuroimaging biomarkers and sensory biomarkers. In addition, we will briefly discuss pain genetics and the role of potential microRNA (miRNA) involved in TMD pain.

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.

Long-term Changes of Temporomandibular Joint Osteoarthritis on Computed Tomography

This study aimed to understand long-term changes of the osteoarthritic temporomandibular joint (TMJ) condyle using computed tomography (CT) and to verify its correlation with clinical characteristics of temporomandibular disorders. Eighty-nine patients (152 joints; 76 female, 13 male) who had taken follow-up CTs (mean follow-up period: 644.58 ± 325.71 days) at least once in addition to their initial evaluation were selected. Cross-sectional demographic and clinical data and longitudinal CT images were collected. Data were analyzed by analysis of variance and logistic regression. Overall destructive change index (number of TMJ condyle sections in which destructive change was observed) decreased from 1.56 to 0.66. Improvement was seen in 93 joints (61.2%) and 27 joints (17.8%) worsened. In the pain positive group, both initial and final destructive change index were significantly higher compared to the pain negative group (p = 0.04). Occlusal stabilization splint therapy and nonsteroidal anti-inflammatory drug administration showed a significant effect on improving the prognosis of TMJ osteoarthritis (p = 0.015 and 0.011). In conclusion, TMJ osteoarthritis showed long-term improvement in the majority of cases. TMJ osteoarthritis accompanied by pain showed unfavorable prognosis with additional bone destruction. Occlusal stabilization splint and nonsteroidal anti-inflammatory drug administration were beneficial on the prognosis of TMJ osteoarthritis.

Biomarkers in Temporomandibular Disorder and Trigeminal Neuralgia: A Conceptual Framework for Understanding Chronic Pain

In this review, we will explore the use of biomarkers in chronic pain, using the examples of two prototypical facial pain conditions: trigeminal neuralgia and temporomandibular disorder. We will discuss the main categories of biomarkers and identify various genetic/genomic, molecular, neuroradiological, and psychophysical biomarkers in both facial pain conditions, using them to compare and contrast features of neuropathic, nonneuropathic, and mixed pain. By using two distinct model facial pain conditions to explore pain biomarkers, we aim to familiarize readers with different types of biomarkers currently being studied in chronic pain and explore how these biomarkers may be used to develop new precision medicine approaches to pain diagnosis, prognosis, and management.

Muscle-Bone Crosstalk in the Masticatory System: From Biomechanical to Molecular Interactions

The masticatory system is a complex and highly organized group of structures, including craniofacial bones (maxillae and mandible), muscles, teeth, joints, and neurovascular elements. While the musculoskeletal structures of the head and neck are known to have a different embryonic origin, morphology, biomechanical demands, and biochemical characteristics than the trunk and limbs, their particular molecular basis and cell biology have been much less explored. In the last decade, the concept of muscle-bone crosstalk has emerged, comprising both the loads generated during muscle contraction and a biochemical component through soluble molecules. Bone cells embedded in the mineralized tissue respond to the biomechanical input by releasing molecular factors that impact the homeostasis of the attaching skeletal muscle. In the same way, muscle-derived factors act as soluble signals that modulate the remodeling process of the underlying bones. This concept of muscle-bone crosstalk at a molecular level is particularly interesting in the mandible, due to its tight anatomical relationship with one of the biggest and strongest masticatory muscles, the masseter. However, despite the close physical and physiological interaction of both tissues for proper functioning, this topic has been poorly addressed. Here we present one of the most detailed reviews of the literature to date regarding the biomechanical and biochemical interaction between muscles and bones of the masticatory system, both during development and in physiological or pathological remodeling processes. Evidence related to how masticatory function shapes the craniofacial bones is discussed, and a proposal presented that the masticatory muscles and craniofacial bones serve as secretory tissues. We furthermore discuss our current findings of myokines-release from masseter muscle in physiological conditions, during functional adaptation or pathology, and their putative role as bone-modulators in the craniofacial system. Finally, we address the physiological implications of the crosstalk between muscles and bones in the masticatory system, analyzing pathologies or clinical procedures in which the alteration of one of them affects the homeostasis of the other. Unveiling the mechanisms of muscle-bone crosstalk in the masticatory system opens broad possibilities for understanding and treating temporomandibular disorders, which severely impair the quality of life, with a high cost for diagnosis and management.

Effect of occlusal splint on interleukin 6, malondialdehyde and 8-hydroxydeoxyguanosine levels in the synovial fluid of patients with temporomandibular disorders

The actual role of splint therapy in preventing excessive loading of the temporomandibular joint (TMJ) is still debated. Lower intra-articular pressure levels have been measured in patients wearing occlusal splints, which may also reduce oxidative stress in the articular spaces. The aim of this study was to determine whether splint therapy reduces oxidative stress and inflammation in TMJ internal derangement patients by measuring interleukin 6 (IL-6), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) levels in the synovial fluid (SF). Twenty-four patients with a temporomandibular disorder (TMD) were included in the study. TMJ SF samples were obtained prior to arthrocentesis. Twelve patients used a 2-mm hard acrylic, maxillary stabilization-type splint for 3 months after arthrocentesis. Twelve patients had no treatment after the SF aspiration. Second SF samples were obtained from all patients at 3 months post arthrocentesis. IL-6, MDA, and 8-OHdG levels in the samples were evaluated. All patients showed a significant symptomatic improvement after treatment (P < 0.005). No statistical correlation was found between the two groups concerning pre-treatment and 3-month SF levels of MDA, 8-OHdG, and IL-6. Although splint therapy was found to be successful in eliminating clinical symptoms of TMD, the results showed no beneficial effect on inflammation and oxidative stress markers in the synovial fluid.

Cartilage Metabolism is Modulated by Synovial Fluid Through Metalloproteinase Activity

Synovial fluid (SF) contains various cytokines that regulate chondrocyte metabolism and is dynamically associated with joint disease. The objective of this study was to investigate the effects of diluted normal SF on catabolic metabolism of articular cartilage under inflammatory conditions. For this purpose, SF was isolated from healthy bovine joints, diluted, and added to cartilage explant cultures stimulated with interleukin-1 (IL-1) for 12 days. The kinetic release of sulfated glycosaminoglycan (sGAG) and collagen, as well as nitric oxide and gelatinase matrix metalloproteinases were analyzed in the supernatant. Chondrocyte survival and matrix integrity in the explants were evaluated with Live/Dead and histological staining. Diluted synovial fluid treatment suppressed sGAG and collagen release, downregulated the production of nitric oxide and matrix metalloproteinases, reduced IL-1-induced chondrocyte death, and rescued matrix depletion. Our results demonstrate that normal SF can counteract inflammation-driven cartilage catabolism. This study reports on the protective function of healthy SF and the therapeutic potential of recapitulation of SF for cartilage repair.

Glucosamine oral administration as an adjunct to hyaluronic acid injection in treating temporomandibular joint osteoarthritis

OBJECTIVE

To investigate the therapeutic effect of oral glucosamine (GS) as an adjunct to hyaluronic acid (HA) injection on patients with temporomandibular joint osteoarthritis (TMJ OA).

METHODS

In this clinical trial, 136 participants, diagnosed as TMJ OA clinically and radiographically, were enrolled and randomized into two groups (group GS + HA: oral GS + HA injection; group placebo + HA: oral placebo + HA injection). Pain, maximum interincisal mouth opening (MMO), the levels of IL-1β, IL-6, and TGF-β in TMJ synovial were defined as the outcome measurements and conducted before operation, and at 1-month and 1-year follow-up.

RESULTS

In both groups, pain scores were decreased and MMOs were increased at 1-month and 1-year follow-up, the changes at 1-year follow-up showed statistically significant intergroup differences. At 1-month follow-up, only IL-6 concentration was lower in group GS + HA than that in group placebo + HA. One year later, TGF-β concentration was higher and IL-6 and IL-1β concentrations were lower in group GS + HA than those in group placebo + HA.

CONCLUSIONS

Both strategies alleviated symptoms in short term, but the patients treated with GS benefited more than those with placebo in long term, which may be due to the suppression of IL-1β and IL-6 and the stimulation of TGF-β.

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.

Intra-articular controlled release of anti-inflammatory siRNA with biodegradable polymer microparticles ameliorates temporomandibular joint inflammation

We investigated the in vivo therapeutic efficacy of an intra-articular controlled release system consisting of biodegradable poly(dl-lactic-co-glycolic acid) (PLGA) microparticles (MPs) encapsulating anti-inflammatory small interfering RNA (siRNA), together with branched poly(ethylenimine) (PEI) as a transfecting agent, in a rat model of painful temporomandibular joint (TMJ) inflammation. The in vivo effects of PLGA MP dose and siRNA-PEI polyplex delivery were examined via non-invasive meal pattern analysis and by quantifying the protein level of the siRNA target as well as of several downstream inflammatory cytokines. Controlled release of siRNA-PEI from PLGA MPs significantly reduced inflammation-induced changes in meal patterns compared to untreated rats with inflamed TMJs. These changes correlated to decreases in tissue-level protein expression of the siRNA target to 20-50% of the amount present in the corresponding control groups. Similar reductions were also observed in the expression of downstream inflammatory cytokines, e.g. interleukin-6, whose tissue levels in the siRNA-PEI PLGA MP groups were 50% of the values for the corresponding controls. This intra-articular sustained release system has significant implications for the treatment of severe TMJ pain, and also has the potential to be readily adapted and applied to mitigate painful, chronic inflammation in a variety of conditions.

Interleukin-6 and soluble interleukin-6 receptor suppress osteoclastic differentiation by inducing PGE(2) production in chondrocytes

This study examined how interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6r) influence osteoclastic differentiation through the function of chondrocytes. Chondrocytes were cultured with or without IL-6 and/or sIL-6r in the presence or absence of NS398, a specific inhibitor of cyclooxygenase (COX)-2, for up to 28 days. Chondrocytes were also cultured with or without IL-6 and sIL-6r for 28 days, and the conditioned medium from cells cultured without IL-6 and sIL-6r was used to induce differentiation of RAW264.7 cells into osteoclast precursors. Osteoclastic differentiation was assessed by tartrate-resistant acid phosphatase (TRAP) staining. Expression of osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), COX-2, and prostaglandin E(2) (PGE(2)) increased in cells exposed to IL-6 and sIL-6r, whereas expression of macrophage colony-stimulating factor (M-CSF) and bone resorption-related enzymes decreased. NS398 blocked the stimulatory/suppressive effects of IL-6 and sIL-6r on the expression of OPG, RANKL, and M-CSF. Fewer TRAP-positive multinucleated cells were detected after treatment with conditioned medium from IL-6- and sIL-6r-treated chondrocytes than after treatment with conditioned medium from untreated chondrocytes. These results suggest that IL-6 and sIL-6r interfere with osteoclast function through the involvement of chondrocytes. Specifically, they appear to suppress the differentiation of osteoclast precursors into osteoclasts by inducing chondrocytic PGE(2) production, which, in turn, increases OPG secretion and decreases M-CSF secretion by chondrocytes.

Expression of hyaluronan synthase 3 in deformed human temporomandibular joint discs: in vivo and in vitro studies

The present study aimed at investigating the expression of a hyaluronan synthase (HAS) 3 in tissue samples of deformed human temporomandibular joint (TMJ) discs and cells obtained from the discs. Fifteen adult human TMJ discs (twelve diseased discs and three normal discs) were used in this study. The twelve diseased discs were obtained from twelve patients with internal derangement (ID) of TMJ. These patients all had anteriorly displaced discs and deformed discs. The tissues were immunohistochemically stained using HAS3 antibodies. In addition, the subcultured TMJ disc cells under both normal and hypoxic conditions (O₂: 2%) were incubated for 3, 6, 12, and 24 h after addition of interleukin-1β (IL-1β) (1 ng/mL). Subsequently, the expression of HAS3 was examined using real-time reverse transcription-polymerase chain reaction (RT-PCR). The control group showed from negative to weak positive reactions for HAS3 on immunohistochemical staining. The discs extracted from twelve cases with ID presented from moderate to strong positive reactions for HAS3. The quantity of HAS3 mRNA was compared with a control group, and showed a 204-fold increase at 3 h, a 26-fold increase at 6 h, a 2.5-fold increase at 12 h and a 32-fold increase at 24 h under hypoxia with the addition of IL-1β. The expression of HAS3 mRNA was significantly enhanced at 3 h and 24 h. The results obtained suggest that HAS3 is related to the pathological changes of human TMJ discs affected by ID.

Quantification of condylar resorption in temporomandibular joint osteoarthritis

OBJECTIVE

This study was performed to determine the condylar morphologic variation of osteoarthritic (OA) and asymptomatic temporomandibular joints (TMJs) and to determine its correlation with pain intensity and duration.

STUDY DESIGN

Three-dimensional surface models of mandibular condyles were constructed from cone-beam computerized tomography images of 29 female patients with TMJ OA (Research Diagnostic Criteria for Temporomandibular Disorders group III) and 36 female asymptomatic subjects. Shape correspondence was used to localize and quantify the condylar morphology. Statistical analysis was performed with multivariate analysis of covariance analysis, using Hotelling T(2) metric based on covariance matrices, and Pearson correlation.

RESULTS

The OA condylar morphology was statistically significantly different from the asymptomatic condyles (P < .05). Three-dimensional morphologic variation of the OA condyles was significantly correlated with pain intensity and duration.

CONCLUSION

Three-dimensional quantification of condylar morphology revealed profound differences between OA and asymptomatic condyles, and the extent of the resorptive changes paralleled pain severity and duration.

IL-1beta suppresses the formation of osteoclasts by increasing OPG production via an autocrine mechanism involving celecoxib-related prostaglandins in chondrocytes

Elevated interleukin (IL)-1 concentrations in synovial fluid have been implicated in joint bone and cartilage destruction. Previously, we showed that IL-1beta stimulated the expression of prostaglandin (PG) receptor EP4 via increased PGE(2) production. However, the effect of IL-1beta on osteoclast formation via chondrocytes is unclear. Therefore, we examined the effect of IL-1beta and/or celecoxib on the expression of macrophage colony-stimulating factor (M-CSF), receptor activator of NF-kappaB ligand (RANKL), and osteoprotegerin (OPG) in human chondrocytes, and the indirect effect of IL-1beta on osteoclast-like cell formation using RAW264.7 cells. OPG and RANKL expression increased with IL-1beta; whereas M-CSF expression decreased. Celecoxib blocked the stimulatory effect of IL-1beta. Conditioned medium from IL-1beta-treated chondrocytes decreased TRAP staining in RAW264.7 cells. These results suggest that IL-1beta suppresses the formation of osteoclast-like cells via increased OPG production and decreased M-CSF production in chondrocytes, and OPG production may increase through an autocrine mechanism involving celecoxib-related PGs.

Measuring persistent temporomandibular joint nociception in rats and two mice strains

Temporomandibular joint (TMJ) pain has been reported to last for prolonged periods in humans. In rodents a variety of methods have been used to measure TMJ nociception, but for most of these methods the period of measurement has been minutes to a couple of hours. In addition, most measurement protocols required restraint or training of the animal. Previous studies from our laboratory demonstrated that feeding behavior, particularly meal duration, was an indicator of TMJ nociception in unrestrained and untrained male and female Sprague-Dawley rats for up to two days. In this study, we first found that injection of complete Freund's adjuvant (CFA) into the TMJ of rats significantly lengthened meal duration for 19 days and also decreased meal frequency for 42 days. Interestingly, the meal duration varied significantly from day to day within the 19 day period. TMJ interleukin-1 beta (IL-1 beta) and calcitonin gene-related peptide (CGRP) were significantly elevated in the TMJ tissues of CFA-injected animals and the level of these markers was attenuated as the meal duration decreased with time. Control animals injected with saline into the TMJ or CFA into the knee did not show a significant lengthening in meal duration but did show a decrease in meal frequency. In a second study, DBA/1LacJ mice given TMJ CFA injections showed a significantly lengthened meal duration on four of the seven days measured using end-of-the meal definition of 5 or 10 min. No other meal pattern changed significantly. Two days post-CFA injection, the DBA/1LacJ mice showed significantly elevated interleukin-6 (IL-6), but not elevated IL-1 beta. Seven days post-injection, both IL-6 and IL-1 beta were significantly elevated. No change in CGRP was detected. In this study C57Bl/6 mice also received TMJ CFA injections, but they did not show a lengthening in any meal pattern or significant increases in IL-1 beta, IL-6 or CGRP. Our data show, for the first time, that meal duration can be used to measure CFA-induced nociception in the TMJ over the course of several weeks in unrestrained rats and for up to seven days in the DBA/1LacJ mouse strain. In addition, C57Bl/6 mice are resistant to CFA-induced TMJ nociception at the same dose used in the DBA/1LacJ mice.

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.

Current diagnosis of temporomandibular pathologies

The current scientific knowledge of TMJ pathologies points to the importance of etiological research and the need for differential diagnosis using the most modem technological resources. Those include MRI, computed tomography, serologic studies, genetic mapping, and bioelectronic instruments which allow clinicians to study, understand, and measure respectively, the structural changes of soft and hard tissues, infections, genetic susceptibility for autoimmune diseases, and stomatognathic function. The purpose of this article is an overview of the current knowledge and related tools for the diagnosis of TMJ pathologies.

IL-1beta stimulates the expression of prostaglandin receptor EP4 in human chondrocytes by increasing production of prostaglandin E2

Prostaglandin (PG) E(2), which exerts its actions via the PG receptors EP1-4, is produced from arachidonic acid by cyclooxygenase (COX)-1 and COX-2. The aim of this study was to investigate the mechanisms by which interleukin (IL)-1beta induces the expression of PG receptors in cultured human chondrocytes and to explore the role of PGE(2) in this process. The cells were cultured with 0, 10, or 100 U/mL IL-1beta with or without 1 muM celecoxib, a specific inhibitor of COX-2, for up to 28 days. Expression of the genes encoding COX-1, COX-2, and EP1-4 was quantified using real-time PCR, and expression of the corresponding proteins was examined using immunohistochemical staining. PGE(2) production was determined using ELISA. IL-1beta treatment caused a marked dose- and time-dependent increase in the levels of PGE(2), COX-2, and EP4 as compared with the untreated control. It did not affect the expression of COX-1, and it decreased the expression of EP1 and EP2. EP3 expression was not detected in either the absence or the presence of IL-1beta. When celecoxib was also present, IL-1beta failed to stimulate PGE(2) production and EP4 expression, but its stimulatory effect on COX-2 expression and its inhibitory effect on EP1 and EP2 expression were unchanged. IL-1beta increases the production of PGE(2), COX-2, and the PG receptor EP4 in cultured human chondrocytes. The increase in EP4 expression appears to be a result of the increased PGE(2) production.

Cytokines in temporomandibular joint arthritis

As the article in the current issue by Shinoda and colleagues shows, during the last two decades, there has been a dramatic increase in the understanding of basic biology behind chronic temporomandibular joint (TMJ) pain, inflammation and destruction. The involvement and contribution of cytokines to TMJ pain and inflammation must now be considered as established, evident and fundamental. Based on the present knowledge, it is now possible to design and investigate novel therapeutic strategies. These new and very encouraging approaches include manipulation of cytokine function, immune reactivity and the behaviour of inflammatory cells while maintaining the integrity of the affected tissue.

Pro-inflammatory cytokine, matrix metalloproteinases and TIMP-1 are involved in wound healing after mastectomy in invasive breast cancer patients

BACKGROUND

Mastectomy provides a good model to study the wound healing process after surgery. The involved factors include selectins, pro-inflammatory cytokines such as interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), matrix metalloproteinases (MMPs), and their natural inhibitors (TIMPs). In the present study, we observed the kinetic changes of these factors in the process of wound healing after a mastectomy, and analyzed the relationship between these factors and the clinical outcomes.

MATERIALS AND METHODS

Twenty-nine patients, who received a modified radical mastectomy, were recruited to this study. The wound was inspected daily for the presence of flap necrosis, infection and seroma. Drain fluid was collected on days 1, 2 and 5. IL-6, P-selectin, MMP-2, 3, 9 and TIMP-1 were screened by ELISA kits for their impacts on wound healing after mastectomy.

RESULTS

IL-6 demonstrated the highest level on Day 1 after operation and was negatively correlated with MMP-2, which in turn showed a consistently negative correlation with MMP-9 for days 1, 2 and 5. Incidences of seroma formation and skin flap necrosis were 27.6% and 20.7%, respectively. Seroma formation was associated with low MMP-2 levels on Day 5. While skin flap necrosis seemed to correlate with high MMP-2 levels and low levels of MMP-9 and TIMP-1.

CONCLUSION

IL-6, P-selectin, MMP-2, MMP-3, MMP-9 and TIMP-1 are important in the process of wound healing after mastectomy. A low MMP-2 level correlates with the formation of seroma, while MMP-2, MMP-9 and TIMP-1 are associated with skin flap necrosis.

Regulation of HAS expression in human synovial lining cells of TMJ by IL-1beta

Hyaluronan (HA), a major glycosaminoglycan of synovial fluid, is synthesised by a class of membrane-bound HA synthase (HAS) proteins. In the present study, we investigated the regulatory roles of IL-1beta on HAS gene expression and HA production by the fibroblastic synovial lining cells. The synovial lining cells from synovial membrane in human temporomandibular joint (TMJ) were cultured and characterised using immunocytochemistry with CD14, CD44, and vimentin monoclonal antibodies. With or without treatment with IL-1beta, the production of HA was detected with radiometric assay and the expression of HAS mRNAs were analysed with a semi-quantitative reverse transcribed polymerase chain reaction (RT-PCR). HA synthesis was significantly augmented with 1ng/ml of IL-1beta for both 24 and 48h stimulation, however the production of HA declined if stimulated with 10ng/ml of IL-1beta. The expression of HAS2 and 3 mRNA were enhanced about 4.2- and 7.2-fold after 4h stimulation with 1ng/ml of IL-1beta, respectively. From these results, it is concluded that IL-1beta functions on regulating HAS expression and consequently promoting the secretion of HA in synovial lining cells from TMJ.

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.

Direct and indirect markers of cartilage metabolism in synovial fluid obtained from dogs with hip dysplasia and correlation with clinical and radiographic variables

OBJECTIVE

To compare activities of interleukin (IL)-1beta, IL-6, tumor necrosis factor (TNF)-alpha, and matrix metalloproteinase (MMP)-3 and contents of sulfated glycosaminoglycan (S-GAG) in joint fluid obtained from dogs with hip dysplasia (HD) and clinically normal dogs, evaluate correlations among these markers in joint fluid obtained from dogs with HD, and evaluate correlations between each marker and clinical and radiographic variables. Animals-26 dogs with HD (clinical group) and 43 clinically normal Beagles (control group).

PROCEDURE

Joint fluid was aseptically collected from the hip joints of all dogs. For each dog in the clinical group, age, duration of lameness, radiographic osteoarthritis (OA) score, and Norberg angle in each affected joint were recorded. Activities of IL-1beta, IL-6, TNF-alpha, and MMP-3 and S-GAG contents were measured. Values were compared between groups by use of Mann-Whitney U tests, and the Spearman rank correlation test was used to evaluate correlations among markers and between each marker and clinical or radiographic variables.

RESULTS

Values of all markers were significantly higher for the clinical group, compared with values for the control group. There was a moderate positive correlation between lameness duration and IL-6 activity and a strong negative correlation between the Norberg angle and IL-1beta activity.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of our results indicated that there was a significant increase in markers of OA in dogs with HD. Activities of IL-1beta and IL-6 in joint fluid of dogs with HD may be influenced by the severity of laxity in the hip joint and lameness duration, respectively.

Antibody array analysis of peripheral and blood cytokine levels in rats after masseter inflammation

This study was undertaken to evaluate the changes in cytokine levels in response to orofacial deep tissue inflammation. Inflammation was induced by injecting complete Freund's adjuvant (CFA, 0.05 ml 1:1 oil/saline suspension) into the masseter of the male Sprague-Dawley rat under brief halothane anesthesia. At 30 min, 5 h and 24 h after CFA injection (n = 3-4/time point), tissues were dissected from masseter and total proteins isolated. Rat Cytokine Antibody Array 1.1 (RayBiotech) coated with 19 specific cytokine antibodies were probed with protein samples and the relative cytokine levels were compared. Compared to saline-injected rats, there were significant increases (p < 0.05-0.01) in the levels of seven cytokines in the masseter tissue after CFA, including interleukin (IL)-1beta (5 h), IL-6 (5 h), tumor necrosis factor-alpha (5 h), monocyte chemoattractant protein-1 (5 h, 24 h), cytokine-induced neutrophil chemoattractant-2 and -3 (5 h, 24 h), and tissue inhibitor of metalloproteinase-1 (5 h, 24 h). All 19 cytokines were detected in the blood samples, but they did not show significant changes after inflammation. Masseter hyperalgesia and allodynia occurred at 30 min and persisted at 5-24 h after inflammation, as assessed by probing the skin above the masseter with von Frey filaments. The present results indicate selective localized cytokine responses to masseter inflammation. Although different cytokines exist in the blood, their levels did not mirror, nor did not appear to depend on, the local cytokine levels. The findings provide specific targets for further studying the involvement of cytokines in orofacial inflammation and hyperalgesia.

The role of biomechanics and inflammation in cartilage injury and repair

Osteoarthritis is a painful and debilitating disease characterized by progressive degenerative changes in the articular cartilage and other joint tissues. Biomechanical factors play a critical role in the initiation and progression of this disease, as evidenced by clinical and animal studies of alterations in the mechanical environment of the joint caused by trauma, joint instability, disuse, or obesity. The onset of these changes after joint injury generally has been termed posttraumatic arthritis and can be accelerated by factors such as a displaced articular fracture. Within this context, there is considerable evidence that interactions between biomechanical factors and proinflammatory mediators are involved in the progression of cartilage degeneration in posttraumatic arthritis. In vivo studies have shown increased concentrations of inflammatory cytokines and mediators in the joint in mechanically induced models of osteoarthritis. In vitro explant studies confirm that mechanical load is a potent regulator of matrix metabolism, cell viability, and the production of proinflammatory mediators such as nitric oxide and prostaglandin E2. Knowledge of the interaction of inflammatory and biomechanical factors in regulating cartilage metabolism would be beneficial to an understanding of the etiopathogenesis of posttraumatic osteoarthritis and in the improvement of therapies for joint injury.