Matrix metalloproteinases in mild and severe temporomandibular joint internal derangement synovial fluid

Salivary Biomarkers and Temporomandibular Disorders: A Systematic Review conducted according to PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions

BACKGROUND

The present review aimed to investigate the association between salivary biomarkers and temporomandibular disorders (TMD). TMD is a multifactorial condition characterised by pain and dysfunction in the temporomandibular joint (TMJ) and surrounding structures. Salivary biomarkers have emerged as potential diagnostic tools due to their non-invasiveness and easy accessibility. However, the literature on salivary biomarkers in relation to TMD is limited and inconsistent.

METHODS

Electronic databases of Pubmed, Embase, Web of Science, Scopus, Cochrane Library, PsychINFO, CINAHL and Medline were searched using specific search terms and Boolean operators. The search was limited to articles published in English that assessed salivary biomarkers in individuals diagnosed with TMD. Two reviewers independently screened the articles and extracted data. ROB-2 was used to assess the risk of bias.

RESULTS

Eleven clinical papers met the inclusion criteria and were included in the review. The findings provided consistent evidence of a clear association between salivary biomarkers and TMD. Various biomarkers, including cortisol, IL-1, glutamate and several others, were assessed. Some studies reported higher levels of cortisol and IL-1 in TMD patients, indicating potential involvement in stress and inflammation. Glutamate levels were found to be elevated, suggesting a role in pain modulation. Other biomarkers also showed alterations in TMD patients compared to controls: CONCLUSION: The findings from the included studies suggest that salivary biomarkers may play a role in TMD pathophysiology. Though a definitive conclusion can be drawn regarding the specific salivary biomarkers and their association with TMD, the results must be interpreted with caution considering the heterogeneity of the biomarkers assessed. Further research with larger sample sizes, standardised methodology and rigorous study designs is needed to elucidate the role of salivary biomarkers in TMD.

Associations of tissue damage induced inflammatory plasticity in masseter muscle with the resolution of chronic myalgia

Gene plasticity during myogenous temporomandibular disorder (TMDM) development is largely unknown. TMDM could be modeled by intramuscular inflammation or tissue damage. To model inflammation induced TMDM we injected complete Freund's adjuvant (CFA) into masseter muscle (MM). To model tissue damage induced TMDM we injected extracellular matrix degrading collagenase type 2 (Col). CFA and Col produced distinct myalgia development trajectories. We performed bulk RNA-seq of MM to generate gene plasticity time course. CFA initiated TMDM (1d post-injection) was mainly linked to chemo-tacticity of monocytes and neutrophils. At CFA-induced hypersensitivity post-resolution (5d post-injection), tissue repair processes were pronounced, while inflammation was absent. Col (0.2U) produced acute hypersensitivity linked to tissue repair without inflammatory processes. Col (10U) generated prolonged hypersensitivity with inflammatory processes dominating initiation phase (1d). Pre-resolution phase (6d) was accompanied with acceleration of expressions for tissue repair and pro-inflammatory genes. Flow cytometry showed that immune processes in MM was associated with accumulations of macrophages, natural killer, dendritic and T-cells, further confirming our RNA-seq findings. Altogether, CFA and Col treatments induced different immune processes in MM. Importantly, TMDM resolution was preceded with muscle cell and extracellular matrix repairs, an elevation in immune system gene expressions and distinct immune cell accumulations in MM.

Metalloproteases in Pain Generation and Persistence: A Possible Target?

Matrix metalloproteinases (MMPs) are a large family of zinc-dependent proteolytic enzymes associated with extracellular matrix protein turnover and tissue degradation. They participate to many different physiological reactions but are also hyperactivated in several diseases. Various literature studies have documented that MMPs play a role in the modulation of neuropathic and nociceptive pain. The heterogeneity of clinical and pre-clinical data is an important issue in this experimental context. Despite the presence of a good number of studies on MMP inhibitors, these drugs showed scarce efficacy and relevant side effects. In the present manuscript, we reviewed studies in the literature that define a possible role of MMPs in pain and the effects of their modulation.

MMPs in tissues retrieved during surgery from patients with TMJ disorders relate to pain more than to radiological damage score

Orofacial pain is among the most common chronic pain conditions and can result from temporomandibular disorders (TMDs) of the temporomandibular joint (TMJ). Matrix metalloproteinases (MMPs) drive degeneration of TMJ tissues and likely mediate pain in TMJ disorders given their role in nociception. However, few studies have assessed MMPs in the TMJ innervated tissues nor in the context of pain. This study defined the extent of MMP-1, MMP-9, and MMP-2 in TMJ tissues from patients undergoing total joint replacement (TJR) or arthroplasty discectomy for painful TMJ disorders. Protein expression was probed by Western blot in TMJ disc and capsular ligaments taken during TJR (n = 6) or discectomy (n = 3) for osteoarthritis or internal derangement in an IRB-approved study. Pro- and active MMP-1, active MMP-9, and pro- and active MMP-2 are detectable. MMP-1 and MMP-9 correlate positively to each other (Kendall's τ = 0.63; p = 0.01), strengthening the hypothesis that they are mechanistically related in regulatory cascades. Active MMP-1 and active MMP-9 correlate positively with self-reported pain scores (τ ≥ 0.51; p ≤ 0.04), suggesting their involvement in peripheral nociception. Overall, neither MMPs nor pain correlate with the functional vertical opening of the jaw. MMP-1 varies with the observed stage of degeneration during surgery (p = 0.04). Neither overall MMPs nor pain correlate with the overall magnetic resonance imaging scores, corroborating the longstanding, but confounding, clinical observation that pain and radiological evidence of joint damage are not always related. Clinical significance: These findings suggest that MMPs mediate pain in innervated soft tissues and may be targets for diagnosing disease stage and treatments in painful TMJ disorders.

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.

Insights for temporomandibular disorders management: From psychosocial factors to genetics-A case report

AIMS

This case report aimed to discuss the multifactorial etiology and also the management of temporomandibular disorders (TMD) by addressing important associated psychosocial and biological factors, emphasizing the interaction between these factors and a probable genetic predisposition.

METHODS AND RESULTS

A 21-year-old female patient was evaluated according to Research Diagnostic Criteria for TMD and diagnosed with arthralgia, myofascial pain, disc displacement without reduction, and temporomandibular joint (TMJ) degenerative disease. TMJ alterations were confirmed through magnetic resonance imaging and cone-beam computed tomography. Pressure pain threshold of masticatory structures was evaluated using a pressure algometer. Sleep bruxism, poor sleep quality, migraine with aura, mild anxiety, and history of facial trauma were also identified through anamnesis and clinical examination. Following this, genetic analysis was performed to evaluate the presence of single nucleotide polymorphisms (SNPs) already associated with TMD: SNP COMT Val¹⁵⁸ Met (rs4680), MMP1-1607 (rs1799750), and tumor necrosis factor alpha-308 (rs1800629), which were all present. A personalized treatment for TMD management was performed, and it included self-management programs, occlusal appliance therapy, pharmacotherapy, anxiety management, and stress control. An 8-year follow-up demonstrated long-term stabilization of TMJ degenerative disease.

CONCLUSION

Genetic evaluation, added to anamnesis and clinical examination, could be useful for TMD prognosis and management.

Overexpression of MMPs, cytokines, and RANKL/OPG in temporomandibular joint osteoarthritis and their association with joint pain, mouth opening, and bone degeneration: A preliminary report

OBJECTIVE

This study aimed to determine the expression of distinct matrix metalloproteinases, cytokines, and bone resorptive factors in temporomandibular joint osteoarthritis (TMJ-OA) patients and their association with joint pain, mouth opening, and subchondral bone degeneration.

MATERIALS AND METHODS

Twelve patients affected with TMJ-OA (n = 5), disk displacement without reduction (DDWoR) (n = 3), or disk displacement with reduction (DDWR) (n = 4) were selected. Joint pain was quantified by using visual analog scale, mouth opening was quantified at the maximum pain-free aperture, and bone degeneration was quantified using joint imaging. Synovial fluid samples were collected and immediately processed for cell and synovial fluid recovering. From cells, the MMP-1, MMP-2, MMP-8, MMP-13, IL-6, IL-23, and TNF-α expression was quantified by qPCR. From synovial fluid, the RANKL and OPG levels were quantified by ELISA.

RESULTS

Higher levels of MMP-1, MMP-8, MMP-13, IL-6, IL-23, TNF-α, and RANKL/OPG ratio were detected in TMJ-OA compared with DDWoR and DDWR patients (p < .05). Joint pain significantly correlated with TNF-α levels (r = .975, p = .029). Besides, imaging signs of bone degeneration significantly correlated with RANKL/OPG ratio (r = .949, p = .042). Conversely, mouth opening did not correlate with any of the analyzed mediators.

CONCLUSION

During TMJ-OA, a pathological response characterized by the overexpression of TNF-α and RANKL/OPG could be involved in joint pain and subchondral bone degeneration.

Association Between -1607 1G/2G Polymorphism of MMP1 and Temporomandibular Joint Anterior Disc Displacement with Reduction

Anterior disc displacement with reduction (DDWR) is considered one of the most common disorders within the temporomandibular joint (TMJ), with a prevalence of 41% in adults. Matrix metalloproteinases play an important role in the degradation of the TMJ and the matrix metalloproteinase 1 (MMP1) 1607 1G/2G polymorphism increases the local expression of MMP1 thus leading to accelerated degradation of the extracellular matrix. The objective of this study was to evaluate the association between the 1607 1G/2G polymorphism of MMP1 gene and DDWR in a group of Mexican individuals from western Mexico. A total of 67 unrelated individuals, between the ages of 18 and 36 years, of both genders, were included in this study. Study participants with DDWR were required to meet the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), while a second control group of 90 individuals without DDWR were also included. Both groups were required to have paternal and maternal ancestry (grandparents) of the same geographic and ethnic region. Genotypes were determined using the nested PCR technique. The 1G/2G polymorphism was found in 68.7%, followed by 2G/2G in 25.4% and 1G/1G in 6.0% of the cases group. While the prevalence in the control group was 55.5% for the 1G/2G polymorphism, 26.6% for 1G/1G and 17.7% for 2G/2G. An association was found between the 2G allele of the 1607 1G/2G polymorphism of MMP1 gene and the presence of DDWR in the patients of western Mexico.

Stromal cell-derived factor-1 regulates the secretion of interleukin-1β in the temporomandibular joint of rats with synovial inflammation

BACKGROUND

Synovitis is characterized by the infiltration of inflammatory cells and often accompanies the pathological progression of the clinical symptoms affecting the temporomandibular joint (TMJ), such as pain, snapping, and limited mouth opening. It has been suggested that the signal transduction pathway and resultant proinflammatory mediators play important roles in the pathogenesis of synovitis. Therefore, in this present research, we aimed to investigate the changes in the expressions of stromal cell-derived factor 1 (SDF-1) and interleukin (IL)-1β in rats with occlusal interference.

MATERIALS AND METHODS

We divided 36 male Wistar rats into the following groups: Group A (control group), Group B (occlusal interference group), and Group C (AMD3100 group). Synovial inflammation was induced in the rats in Groups B and C to establish the occlusal interference model. The inflammatory changes were detected, and the expressions of SDF-1 and IL-1β in the synovium were assayed via immunostaining and a real-time quantitative polymerase chain reaction (PCR).

RESULTS

In Group B, obvious inflammatory changes were observed in the synovial membranes; additionally, the SDF-1 and IL-1β expression levels were significantly higher at the protein and mRNA levels. However, in Group C, these experimental results were inhibited by an injection with AMD3100.

CONCLUSION

These results may indicate that SDF-1 regulates the expression level of inflammatory factors, such as IL-1β, in the synovial membranes of rats with occlusal interference. Our findings suggest that the SDF-1 axis may contribute to the onset of synovitis during the development of TMJ joint disease.

MMP-7 and MMP-9 are overexpressed in the synovial tissue from severe temporomandibular joint dysfunction

Matrix metalloproteinases (MMPs) are tissue-enzymes that play a key role during the remodeling process, such as in inflammatory diseases. MMP-7 and MMP-9 have been shown to be implicated in extracellular matrix homeostasis and in joint disc remodeling. The objective of this study was to determine the relation of MMP-7 and MMP-9 expression with severe temporomandibular joint dysfunction, in particular with anterior disk displacement without reduction (ADDwoR), using an immunohistochemical approach. Therefore, twenty human temporomandibular synovia in the test group and ten in the control group were collected. The results showed there was a statistically significant difference (P<0.001) for morphometric and densitometric analysis of both detected MMPs in control and test groups. In conclusion, MMP-7 and MMP-9 were overexpressed in the synovial tissue of patients with ADDwoR.

Matrix Metalloproteinases and Temporomandibular Joint Disorder: A Review of the Literature

Temporomandibular disorders (TMD) are progressive degenerative disorders that affect the components of the temporomandibular joint (TMJ), characterized by pain and limitations in function. Matrix metalloproteinases (MMP) are enzymes involved in physiological breakdown of tissue that can have a pathological effect from an increase in activity during inflammation. A PubMed search of the current literature (within the past 10 years) was conducted to identify human studies involving matrix metalloproteinases activity in TMJ components of patients with TMD. Two separate searches results in 34 studies, six of which met inclusion criteria. Immunohistochemistry and gene analysis were used to evaluate MMP expression in the study groups. This review showed the strongest evidence for involvement of MMP-1, MMP-2, and MMP-9 in TMD; however, limitations included low sample sizes and a lack of recent clinical studies. Future research with more definitive conclusions could allow for additional pharmaceutical targets in MMP when treating patients with temporomandibular disorders.

Minimally Invasive Approach for Diagnosing TMJ Osteoarthritis

This study's objectives were to test correlations among groups of biomarkers that are associated with condylar morphology and to apply artificial intelligence to test shape analysis features in a neural network (NN) to stage condylar morphology in temporomandibular joint osteoarthritis (TMJOA). Seventeen TMJOA patients (39.9 ± 11.7 y) experiencing signs and symptoms of the disease for less than 10 y and 17 age- and sex-matched control subjects (39.4 ± 15.2 y) completed a questionnaire, had a temporomandibular joint clinical exam, had blood and saliva samples drawn, and had high-resolution cone beam computed tomography scans taken. Serum and salivary levels of 17 inflammatory biomarkers were quantified using protein microarrays. A NN was trained with 259 other condyles to detect and classify the stage of TMJOA and then compared to repeated clinical experts' classifications. Levels of the salivary biomarkers MMP-3, VE-cadherin, 6Ckine, and PAI-1 were correlated to each other in TMJOA patients and were significantly correlated with condylar morphological variability on the posterior surface of the condyle. In serum, VE-cadherin and VEGF were correlated with one another and with significant morphological variability on the anterior surface of the condyle, while MMP-3 and CXCL16 presented statistically significant associations with variability on the anterior surface, lateral pole, and superior-posterior surface of the condyle. The range of mouth opening variables were the clinical markers with the most significant associations with morphological variability at the medial and lateral condylar poles. The repeated clinician consensus classification had 97.8% agreement on degree of degeneration within 1 group difference. Predictive analytics of the NN's staging of TMJOA compared to the repeated clinicians' consensus revealed 73.5% and 91.2% accuracy. This study demonstrated significant correlations among variations in protein expression levels, clinical symptoms, and condylar surface morphology. The results suggest that 3-dimensional variability in TMJOA condylar morphology can be comprehensively phenotyped by the NN.

The dynamic mechanical viscoelastic properties of the temporomandibular joint disc: The role of collagen and elastin fibers from a perspective of polymer dynamics

The temporomandibular joint disc is a structure, characterized as heterogeneous fibrocartilage, and is composed of macromolecular biopolymers. Despite a large body of characterization studies, the contribution of matrix biopolymers on the dynamic viscoelastic behavior of the disc is poorly understood. Given the high permeability and low concentration of glycosaminoglycans in the disc, it has been suggested that poro-elastic behavior can be neglected and that the intrinsic viscoelastic nature of solid matrix plays a dominant role in governing its time-dependent behavior. This study attempts to quantify the contribution of collagen and elastin fibers to the viscoelastic properties of the disc. Using collagenase and elastase, we perturbed the collagen and elastin fibrillar network in porcine temporomandibular joint discs and investigated the changes of dynamic viscoelastic properties in five different regions of the disc. Following both treatments, the storage and loss moduli of these regions were reduced dramatically up to the point that the tissue was no longer mechanically heterogeneous. However, the proportion of changes in storage and loss moduli were different for each treatment, reflected in the decrease and increase of the loss tangent for collagenase and elastase treated discs, respectively. The reduction of storage and loss moduli of the disc correlated with a decrease of biopolymer length. The present study indicates that the compositional and structural changes of collagen and elastin fibers alter the viscoelastic properties of the disc consistent with polymer dynamics.

Association of risk factors with temporomandibular disorders in the Northern Finland Birth Cohort 1966

OBJECTIVE

To investigate the association between risk factors and pain-related symptoms and clinical signs of temporomandibular disorders (TMD) in Northern Finland Birth Cohort (NFBC) 1966.

MATERIAL AND METHODS

A total of 1962 subjects (1050 women, 912 men) attended the follow-up study. The questionnaires included the subjects' background information concerning living conditions and general health, socioeconomic factors, and dental health. The clinical examination was performed using the modified protocol of Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) presented at the International Association for Dental Research (IADR) Conference in 2010. Cross-tabulation, a chi-square test and Fisher's exact test were used to analyze differences between groups.

RESULTS

Female gender showed statistically significant association with symptoms and signs of TMD, while marital status, living conditions, and socioeconomic group showed no association. A strong association was found between self-reported health condition as well as general health problems [i.e. depression, migraine, fibromyalgia (FM), gastrointestinal diseases] and TMD pain-related symptoms and pain on palpation in the masticatory muscles and TMJs.

CONCLUSION

In conclusion, general health problems and female gender had a strong association with pain-related symptoms and clinical signs of TMD. These findings are important to take into account when diagnosing and treating TMD patients. Conversely to earlier presented results, no statistically significant association was shown here between marital status, living conditions or socioeconomic group and pain-related symptoms and clinical signs of TMD.

The role of occlusion in temporomandibular disorders (TMD) in the Northern Finland Birth Cohort (NFBC) 1966

OBJECTIVE

To investigate the role of occlusion in temporomandibular disorders (TMDs) in the Northern Finland Birth Cohort 1966 (NFBC 1966).

METHODS

Subjects (n = 1962) participated in clinical medical and dental examinations. The association between TMD signs and diagnoses with occlusal disturbances, i.e. malocclusions and occlusal interferences, was examined. Pearson's chi-square test, as expressed by odds ratios (OR) and 95% confidence intervals (CI) and logistic regression models, were used in the analysis.

RESULTS

A statistically significant association was found between myalgia and lateral scissor bite and also between arthralgia and lateral deviation in the retruded contact position and intercuspal contact position (RCP-ICP) slide. Pain in the masticatory muscles was associated with negative overjet and the amount of RCP-ICP slide.

DISCUSSION

Occlusal factors showed a statistically significant association with TMD. The TMD signs were associated with unstable occlusion, especially the amount and lateral deviation in RCP-ICP slide, as well as negative overjet.

Effect of Toll-Like Receptor 4 on Synovial Injury of Temporomandibular Joint in Rats Caused by Occlusal Interference

Synovitis is an important disease that causes intractable pain in TMJ. Some investigations suggested that the increasing expression of IL-1β secreted by synovial lining cells plays an important role in synovial inflammation and cartilage destruction in TMJ. In our previous research, the results demonstrated that TLR4 is involved in the expression of IL-1β in SFs from TMJ with lipopolysaccharide stimulation. However, the inflammatory response that occurred in synovial membrane is not caused by bacterial infection. In the current study, we investigated whether or not TLR4 participates in the inflammatory responses and the expression of IL-1β in synovial membrane of rats induced by occlusal interference. The results showed that obvious inflammation changes were observed in the synovial membranes and the expression of TLR4 and IL-1β was increased at both mRNA and protein levels in the occlusal interference rats. In addition, the inflammation reactions and the increased expression of IL-1β could be restrained by treatment with TAK-242, a blocker of TLR4 signaling. The results prompted us that the activation of TLR4 may be involved in the inflammatory reactions and increased expression of IL-1β in patients with synovitis and participate in the mechanisms of the initiation and development of synovial injury by regulating the expression of inflammatory mediators like IL-1β in synovial membranes.

Low-level laser therapy stimulates tissue repair and reduces the extracellular matrix degradation in rats with induced arthritis in the temporomandibular joint

The objective of this study was to characterize morphological and biochemistry action of low-level laser therapy (LLLT) on induced arthritis in the temporomandibular joint (TMJ) of rats. Twenty-four male Wistar rats were randomly divided into groups with 12 animals each: (AG) group with arthritis induced in the left TMJ and (LG) group with arthritis induced in the left TMJ and treated with LLLT (830 nm, 30 mW, 3 J/cm(2)). Right TMJs in the AG group were used as noninjected control group (CG). Arthritis was induced by intra-articular injection of 50 μl Complete Freund's Adjuvant (CFA) and LLLT began 1 week after arthritis induction. Histopathological analysis was performed using sections stained with hematoxylin-eosin, Toluidine Blue, and picrosirius. Biochemical analysis was determined by the total concentration of sulfated glycosaminoglycans (GAGs) and evaluation of matrix metalloproteinases (MMP-2 and MMP-9). Statistical analysis was performed using paired and unpaired t tests, with p < 0.05. Compared to AG, LG had minor histopathological changes in the TMJ, smaller thickness of the articular disc in the anterior (p < 0.0001), middle (p < 0.0001) and posterior regions (p < 0.0001), high birefringence of collagen fibers in the anterior (p < 0.0001), middle (p < 0.0001) and posterior regions (p < 0.0001) on the articular disc, and statistically lower activity of MMP-2 latent (p < 0.0001), MMP-2 active (P = 0.02), MMP-9 latent (p < 0.0001), and MMP-9 active (p < 0.0001). These results suggest that LLLT can increase the remodeling and enhancing tissue repair in TMJ with induced arthritis.

IL-1β-regulating angiogenic factors expression in perforated temporomandibular disk cells via NF-κB pathway

BACKGROUND

A high density of blood vessels is observed in the perforated disks of temporomandibular joint (TMJ), but the underlying mechanism is unknown. This study aimed to explore the regulation of disk angiogenesis in the perforated disks.

METHODS

Expressions of vascular endothelial growth factor (VEGF), angiogenin-1 (Ang-1), chondromodulin-1 (ChM-1), and thrombospondins-1 (TSP-1) were compared between healthy and perforated TMJ disk cells with or without interleukin-1β (IL-1β) incubation. The tube formation, cell migration, and expressions of matrix-metalloproteinases (MMPs) in human umbilical vein endothelial cell line (HUV-EC-C) were investigated in conditional media of disk cells. Western blot was performed to determine protein level of VEGF, Ang-1, ChM-1 and TSP-1 in IL-1β-induced disk cells cultured by NF-κB- or P38-specific pathway inhibitors, respectively.

RESULTS

Conditional media from perforated disk cells induced more tube formation, cell migration, and MMPs' expression in HUV-EC-C. Expressions of VEGF and Ang-1 were significantly higher, and ChM-1 and TSP-1 were lower in perforated disks compared to healthy disks. The VEGFA concentration was 291.1 ± 36.09 pg/ml in perforated disk cell conditioned media, markedly larger than that in NDCCM (144.9 ± 33.69 pg/ml). IL-1β induced VEGF through NF-κB signaling pathway and Ang-1 through p38 MAPK pathway, while repressed expression of ChM-1 and TSP-1 was through NF-κB pathway. Blockade of each pathway markedly restrained inducing effect of cultural media on HUV-EC-C tube formation and migration.

CONCLUSIONS

Perforated disk cells secreted more angiogenic factors which might induced via NF-κB pathway.

Effect of TLR4/MyD88 signaling pathway on expression of IL-1β and TNF-α in synovial fibroblasts from temporomandibular joint exposed to lipopolysaccharide

Accumulating evidence from previous studies suggested that interleukin-1 (IL-1β) and tumor necrosis factor-α (TNF-α) play an important role in pathogenesis of temporomandibular disorders (TMD). However, the cell surface receptors and the intracellular signal pathways leading to these cytokines expression are not fully understood. In the current study, we investigated the roles of Toll-like receptor 4 (TLR4) and its adaptor myeloid differentiation factor 88 (MyD88) in the expression of IL-1β and TNF-α in synovial fibroblasts (SFs) separated from rat temporomandibular joint (TMJ) with lipopolysaccharide (LPS) stimulation. The results showed that treatment with LPS could increase TLR4, MyD88, IL-1β, and TNF-α expression at both mRNA and protein levels. In addition, increased expression of IL-1β and TNF-α could be blocked by treatment with TAK-242, a blocker of TLR4 signaling, and also by MyD88 inhibitory peptide (MIP). These findings suggested that maybe TLR4/MyD88 signal transduction pathway participates in enhanced expression of IL-1 and TNF-α in patients with TMD. The activation of TLR4/MyD88 signal transduction pathway which results in production of proinflammatory factors may play a role in the pathogenesis of TMD.

Effects of chronic sleep deprivation on the extracellular signal-regulated kinase pathway in the temporomandibular joint of rats

Objectives

To examine the possible involvement and regulatory mechanisms of extracellular signal-regulated kinase (ERK) pathway in the temporomandibular joint (TMJ) of rats subjected to chronic sleep deprivation (CSD).

Methods

Rats were subjected to CSD using the modified multiple platform method (MMPM). The serum levels of corticosterone (CORT) and adrenocorticotropic hormone (ACTH) were tested and histomorphology and ultrastructure of the TMJ were observed. The ERK and phospho-ERK (p-ERK) expression levels were detected by Western blot analysis, and the MMP-1, MMP-3, and MMP-13 expression levels were detected by real-time quantitative polymerase chain reaction (PCR) and Western blotting.

Results

The elevated serum CORT and ACTH levels confirmed that the rats were under CSD stress. Hematoxylin and eosin (HE) staining and scanning electron microscopy (SEM) showed pathological alterations in the TMJ following CSD; furthermore, the p-ERK was activated and the mRNA and protein expression levels of MMP-1, MMP-3, and MMP-13 were upregulated after CSD. In the rats administered with the selective ERK inhibitor U0126, decreased tissue destruction was observed. Phospho-ERK activation was visibly blocked and the MMP-1, MMP-3, and MMP-13 mRNA and protein levels were lower than the corresponding levels in the CSD without U0126 group.

Conclusion

These findings indicate that CSD activates the ERK pathway and upregulates the MMP-1, MMP-3, and MMP-13 mRNA and protein levels in the TMJ of rats. Thus, CSD induces ERK pathway activation and causes pathological alterations in the TMJ. ERK may be associated with TMJ destruction by promoting the expression of MMPs.

An ex vivo study on immunohistochemical localization of MMP-7 and MMP-9 in temporomandibular joint discs with internal derangement

Internal derangement (ID) is among the most common disorders of the temporomandibular joint (TMJ). Previous research by our group highlighted a correlation between apoptosis and TMJ ID. Metalloproteinases (MMP)-7 and -9 have been shown to play an important role in extracellular matrix ECM) homeostasis and, through it, in joint disc remodelling. The immunohistochemical expression of MMP-7 and -9 was investigated in discs from patients with TMJ ID and from healthy donors and compared with the degree of histological tissue degeneration. The collagen fibre arrangement in pathological discs exhibited varying degrees of disruption. New vessels were consistently detected; endothelial cells from these vessels were immunolabelled with both MMP-7 and MMP-9. More or less intense MMP-7 and MMP-9 immunolabelling was detected in the cytoplasm of disc cells from all patients. MMP-7 and MMP-9 immunostaining was significantly different between pathological and normal discs and correlated with the extent of histopathological degeneration. MMP-7 and MMP-9 upregulation in discs from patients with TMJ ID demonstrates their involvement in disc damage in this disorder. A greater understanding of these processes could help identify ways to curb MMP overproduction without affecting their tissue remodelling action. The design of specific inhibitors for these MMPs would not only help to gain insights into the biological roles of MMPs, but would also aid in developing therapeutic interventions for diseases associated with abnormal ECM degradation.

Osteoarthritis-like damage of cartilage in the temporomandibular joints in mice with autoimmune inflammatory arthritis

OBJECTIVE

To study temporomandibular joint (TMJ) involvement in an autoimmune murine model of rheumatoid arthritis (RA), a disease characterized by inflammatory destruction of the synovial joints. Although TMJ dysfunction is frequently found in RA, TMJ involvement in RA remains unclear, and TMJ pathology has not been studied in systemic autoimmune animal models of RA.

METHODS

Proteoglycan (PG) aggrecan-induced arthritis (PGIA) was generated in genetically susceptible BALB/c mice. TMJs and joint tissues/cartilage were harvested for histological and immunohistochemical analyses and RNA isolation for quantitative polymerase chain-reaction. Serum cytokine levels were measured in mice with acute or chronic arthritis, and in non-arthritic control animals.

RESULTS

Despite the development of destructive synovitis in the limbs, little or no synovial inflammation was found in the TMJs of mice with PGIA. However, the TMJs of arthritic mice showed evidence of aggrecanase- and matrix metalloproteinase-mediated loss of glycosaminoglycan-containing aggrecan, and in the most severe cases, structural damage of cartilage. Serum levels of pro-inflammatory cytokines, including interleukin (IL)-1β, were elevated in arthritic animals. Expression of the IL-1β gene was also high in the inflamed limbs, but essentially normal in the TMJs. Local expression of genes encoding matrix-degrading enzymes (aggrecanases and stromelysin) was upregulated to a similar degree in both the limbs and the TMJs.

CONCLUSION

We propose that constantly elevated levels of catabolic cytokines, such as IL-1β, in the circulation (released from inflamed joints) create a pro-inflammatory milieu within the TMJ, causing local upregulation of proteolytic enzymes and subsequent loss of aggrecan from cartilage.

MMP-13 (collagenase 3) localization in human temporomandibular joint discs with internal derangement

The normal articular disc of the human temporomandibular joint (TMJ) consists of regularly arranged collagen fibers and fibroblast-like cells. Disc tissue is subjected to various types of loading. Adaptive remodelling entails microscopic changes in which different types of collagen and non-collagen proteins, as well as matrix metalloproteinases (MMPs), are involved. Collagenase-3 (MMP-13) seems to play a key role. The aim of the study was to evaluate its involvement in TMJ disc histopathology. We studied 10 discs from patients with arthropathy of the TMJ. Paraffin wax-embedded sections were processed for histological and immunohistochemical analysis. A well-characterized mouse monoclonal anti-MMP-13 antibody (anti-collagenase 3) was used. The results showed increased MMP-13 immunoreactivity in TMJ diseased disc tissue was correlated with the severity of the histopathological changes. The more severe the pathological changes, the greater the number of immunolabelled cells detected. Nearly all chondrocyte-like cells were immunopositive, whereas fibroblast-like cells and fibrochondrocytes were more rarely labelled. MMP-13 upregulation in disc tissue from patients with TMJ internal derangement suggests that MMP-13 is involved in disc histopathology, and that disc cells actively participate in the synthesis of extracellular matrix-degrading proteinases.

Pushing the limit: masticatory stress and adaptive plasticity in mammalian craniomandibular joints

Excessive, repetitive and altered loading have been implicated in the initiation of a series of soft- and hard-tissue responses or ;functional adaptations' of masticatory and locomotor elements. Such adaptive plasticity in tissue types appears designed to maintain a sufficient safety factor, and thus the integrity of given element or system, for a predominant loading environment(s). Employing a mammalian species for which considerable in vivo data on masticatory behaviors are available, genetically similar domestic white rabbits were raised on diets of different mechanical properties so as to develop an experimental model of joint function in a normal range of physiological loads. These integrative experiments are used to unravel the dynamic inter-relationships among mechanical loading, tissue adaptive plasticity, norms of reaction and performance in two cranial joint systems: the mandibular symphysis and temporomandibular joint (TMJ). Here, we argue that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures. Our study also suggests that the short-term duration of earlier analyses of cranial joint tissues may offer a limited notion of the complex process of developmental plasticity, especially as it relates to the effects of long-term variation in mechanical loads, when a joint is increasingly characterized by adaptive and degradative changes in tissue structure and composition. Indeed, it is likely that a component of the adaptive increases in rabbit TMJ and symphyseal proportions and biomineralization represent a compensatory mechanism to cartilage degradation that serves to maintain the overall functional integrity of each joint system. Therefore, while variation in cranial joint anatomy and performance among sister taxa is, in part, an epiphenomenon of interspecific differences in diet-induced masticatory stresses characterizing the individual ontogenies of the members of a species, this behavioral signal may be increasingly mitigated in over-loaded and perhaps older organisms by the interplay between adaptive and degradative tissue responses.

Expression of matrix metalloproteinases and aggrecanase in the synovial fluids of patients with symptomatic temporomandibular disorders

OBJECTIVE

To investigate whether matrix metalloproteinases (MMPs) and/or aggrecanase in synovial fluid can be used as biochemical markers in the diagnosis of internal derangement (ID) of the temporomandibular joint (TMJ).

STUDY DESIGN

Forty-four samples of synovial fluid were obtained from 35 patients with ID and osteoarthritis (OA) and 15 normal samples from 10 asymptomatic volunteers. MMP-2, -9, and aggrecanase in the synovial fluid were examined by immunoblotting.

RESULTS

The incidences of MMP-2, -9, and aggrecanase expression in the ID and OA group were significantly higher than those in the normal group (P < .05). Those with anterior disc displacement without reduction and severe OA showed significantly high expression of MMP-9 compared with other disease subgroups (P < .05). Conversely, comparatively high expression of MMP-2 and aggrecanase was shown in the early-stage OA group. However, there was no significant difference in expression of MMP-2 and aggrecanase among disease subgroups.

CONCLUSIONS

These findings suggested that expression of aggrecanase could be a potential biochemical marker for articular cartilage degradation in ID of the TMJ.

Electrophoretic separation of the synovial fluid proteins in patients with temporomandibular joint disorders

OBJECTIVE

The present study was performed to characterize the patterns of protein expression in the synovial fluid (SF) of patients with temporomandibular joint disorders (TMD) by electrophoretic fractionation.

STUDY DESIGN

Samples of the SF of 26 consecutive patients consisting of 16 with closed locking (CL group) and 10 with osteoarthritis (OA group), as well as 7 asymptomatic control subjects (AS group), were analyzed in the present study. SF samples were obtained from the upper compartment of the temporomandibular joint (TMJ) and equal quantities of SF protein were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

The mean total protein concentrations in the SF from both of the TMD groups were higher than that in the AS group (1353 microg/mL in the CL group and 2485 microg/mL in the OA group vs 615 microg/mL in the AS group; P < .01). Moreover, the mean total SF protein concentration was higher in the OA group than in the CL group (P < .01). There was a correlation between the total protein concentration in the SF from both patient groups and the degree of expanded joint effusion (P = .003, r = 0.685). Approximately 22 different protein bands with molecular weights ranging from 14 to 700 kd were clearly discernible on electrophoresis. The relative amounts of specific proteins in the SF of the TMD group were also different from those in the AS group (P < .05). The major difference in total protein concentration appeared to be due to the increased abundance of relatively high molecular weight proteins (>140 kd) in the TMD patients as compared to the AS group.

CONCLUSIONS

The SF of patients with TMD showed significant quantitative differences in total protein abundance as compared to healthy subjects. Moreover, this protein abundance was correlated strongly with the degree of expanded joint effusion. The major difference in total protein concentration appeared to be due to the increased abundance of relatively high molecular weight polypeptides in the TMD patients as compared to the healthy control subjects. These observations of changes in the pattern of protein expression may help in understanding the etiological factors involved in the pathophysiology of TMD.

Aggrecanase analysis of synovial fluid of temporomandibular joint disorders

OBJECTIVES

To determine whether or not aggrecanase in synovial fluid can be used as a biochemical marker in the diagnosis of temporomandibular joint disorder (TMJD).

MATERIALS AND METHODS

Forty-four samples of synovial fluid were obtained from 35 patients with internal derangement or osteoarthritis and 15 control samples from 10 asymptomatic volunteers. Aggrecanase in the synovial fluid was examined by immunoblotting.

RESULT

The incidence of aggrecanase expression in TMJD group were significantly higher than that in the normal control group (P < 0.05). Those with severe OA and anterior disc displacement without reduction showed significantly high expression of aggrecanase compared with other disease subgroups (P < 0.05).

CONCLUSION

These findings suggested that aggrecanase could be a potential biochemical marker for cartilage degeneration in the TMJD.

Histologic evaluation of temporomandibular arthritis induced by mild mechanical loading in rabbits

BACKGROUND

We still lack knowledge of causative factors in arthritis related to temporomandibular disorders (TMD). The goal of the present study was to investigate whether applying a mechanical loading on the glenoid fossa can induce arthritis.

METHODS

Coil springs were placed in 24 rabbits so as to exert a force of 100 g between the orbital edge and the antegonial notch. At 1, 2, 4 and 8 weeks after the surgery, six samples of the temporomandibular joint (TMJ) were removed for histologic examination.

RESULTS

The results showed that mild synovitis began 1-2 weeks after the start of loading, and the degree of synovitis was significant at 4 weeks, and that morphologic changes occurred in the articular eminence and condyle, while type II collagen in the cartilage of the articular eminence degraded prior to that in the condyle.

CONCLUSIONS

Our results revealed that mild, continuous mechanical loading to the glenoid fossa induces synovitis of the articular capsule, and induces organic changes of the articular cartilage without destroying these tissues.

MMP-3 and -8 expression is found in the condylar surface of temporomandibular joints with internal derangement

BACKGROUND

Internal derangement is one of the most common disorder of the temporomandibular joint (TMJ). The aim of this study was to investigate the associations of matrix metalloproteinase (MMP)-3 and -8 expression in articular condylar surface with different stages of TMJ internal derangement according to Wilkes (Minn Med, 1978; 61: 645-52) and osteoarthrosis (OA) according to Dijkgraaf et al. (J Oral Maxillofac Surg, 1995; 53: 1182-92).

METHODS

The study was based on 54 condylar specimens obtained during TMJ surgery. Immunohistochemistry using antibodies specific to MMP-3 and -8, represented in cartilage destruction, was carried out.

RESULTS

In all tissue specimens, MMP-3 expression was intense in the surface layer but showed less intensive staining in the deeper layers. Some MMP-8 expression was also seen. The severity of TMJ internal derangement, however, did not seem to have a statistically significant correlation (P<0.05) with the expression of these enzymes.

CONCLUSION

The study confirms that distinct expression of MMP-3 and -8 is found in the condylar surface of TMJs with internal derangement.

Novel nonmatrix-metalloproteinase-mediated collagen degradation

Matrix metalloproteinases (MMPs) and their inhibitors have long been believed to play a major role in the collagen loss seen in destructive temporomandibular joint (TMJ) disorders. This project was originally designed to examine the expression of MMPs and the tissue inhibitors of MMPs (TIMPs) by diseased human TMJ synovial fibroblasts and to determine their ability to degrade Type I collagen. Reverse transcriptase-PCR indicated that these TMJ synovial fibroblasts expressed mRNA for multiple MMPs and TIMPs. The collagen degradation assay showed that these TMJ synovial fibroblasts at passage 3 to 8 were capable of digesting the collagen underneath them on collagen-coated plates. This degradation was inhibited by GM6001, a synthetic MMP inhibitor. During passage 8 to 13, these TMJ fibroblasts were able to digest all the collagen in the wells. This degradation was completely inhibited by combining GM6001 and soybean trypsin inhibitor (STI), a serine proteinase inhibitor. The collagen cleavage activity of collected conditioned media was dramatically inhibited by STI but not by 1,10-phenanthroline, an MMP inhibitor. The data suggest that these TMJ cells utilize a MMP-dependent pathway and a novel MMP-independent pathway to digest Type I collagen.

Activation of MMP-2 by Porphyromonas gingivalis in human periodontal ligament cells

It has been reported that matrix metalloproteinase (MMP) produced by host cells plays a major role in periodontal tissue destruction. In addition, secreted virulence factors from Porphyromonas gingivalis can alter MMP secretion and cause activation in host cells that lead to the tissue degradation. In this study, we examine the effects of P. gingivalis supernatant on matrix metalloproteinase-2 (MMP-2) activation in human periodontal ligament (HPDL) cells. Cultures of HPDL cells were treated with P. gingivalis supernatant for 48 h and the level of MMP-2 activation was monitored by gelatin zymography. The profound activation of MMP-2 was seen only in the treated group. The activation of MMP-2 was inhibited by MMP inhibitors phenanthroline and EDTA, but not serine protease or cysteine protease inhibitors. To study the correlation between the expression of membrane-type-1 matrix metalloproteinase (MT1-MMP) and the activation of MMP-2, the level of MT1-MMP was analyzed. The results from reverse-transcription polymerase chain reaction (RT-PCR) and Western analysis indicated that P. gingivalis supernatant up-regulated the expression of MT1-MMP in both transcription and translation levels within 48 h. These results suggest that P. gingivalis supernatant can activate MMP-2 in HPDL cells and the mechanism of activation may involve the increased amount of MT1-MMP. It is possible that the activation of MMP-2 by P. gingivalis plays a role in the process of chronic periodontitis.

Specific expression of inducible nitric oxide synthase in the synovium of the diseased temporomandibular joint

OBJECTIVE

The expression of inducible nitric oxide synthase (iNOS) in temporomandibular joint (TMJ) specimens obtained arthroscopically from diseased TMJs was investigated by using immunohistochemistry and compared with clinical, arthroscopic, and histologic findings.

STUDY DESIGN

Synovial biopsies were obtained arthroscopically from 18 TMJs in 15 patients with symptomatic internal derangement (ID) or osteoarthritis (OA). We also obtained arthroscopic biopsies from 8 control TMJs (3 with habitual luxation of the mandible, one with ID with clicking, and 4 with mandibular condyle fractures). The expression of iNOS was examined by immunohistochemistry and was compared with clinical, arthroscopic, and histologic findings.

RESULTS

Definite or intense iNOS immunoreactivity was observed in both the synovial lining cells and the endothelial cells of TMJs with symptomatic ID or OA. Weaker immunoreactivity was present in synovial fibroblasts. In contrast, in TMJs without synovitis (eg, those with habitual luxation of the mandible) the expression of iNOS was weak or marginal. The expression of iNOS correlated significantly with arthroscopic evidence of synovitis (r = 0.406, P <.05) but not with cartilaginous degeneration (P >.05). The expression of iNOS also correlated with the histologic grade of the synovial lining cell layers (r = 0.530, P <.05). However, in patients with ID or OA of the TMJ, there was no statistically significant correlation between the intensity of iNOS immunoreactivity and clinical, arthroscopic, or histologic findings (P >.05).

CONCLUSION

These data clearly suggest that nitric oxide is locally produced in the synovial lining of the TMJ in ID and OA.