Cytokine profile in the synovial fluid of patients with temporomandibular joint disorders: A systematic review

TRIM52 knockdown inhibits proliferation, inflammatory responses and oxidative stress in IL-1β-induced synovial fibroblasts to alleviate temporomandibular joint osteoarthritis

To explore the mechanism of tripartite motif 52 (TRIM52) in the progression of temporomandibular joint osteoarthritis (TMJOA). Gene and protein expression were tested by quantitative real-time polymerase chain reaction and western blot, respectively. The levels of pro-inflammatory cytokines and oxidative stress factors were evaluated using enzyme-linked immunosorbent assay and biochemical kit, respectively. Cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays were carried out to assess cell proliferation. Immunofluorescence was used to detect the expression of CD68 and Vimentin in primary synovial fibroblasts (SFs). Haematoxylin and eosin staining and Safranin O/Fast green were used to evaluate the pathological damage of synovial and cartilage tissue in rats. TRIM52 was upregulated in the synovial tissue and SFs in patients with TMJOA. Interleukin (IL)-1β treatment upregulated TRIM52 expression in TMJOA SFs and normal SF (NSF), promoting cell proliferation, inflammatory response and oxidative stress in NSF, SFs. Silence of TRIM52 relieved the cell proliferation, inflammatory response and oxidative stress induced by IL-1β in SFs, while overexpression of TRIM52 enhanced IL-1β induction. Meanwhile, IL-1β induction activated toll-like receptor 4 (TLR4)/nuclear factor (NF)-κB pathway, which was augmented by upregulation of TRIM52 in NSF, and was attenuated by TRIM52 knockdown in SFs. Besides, pyrrolidinedithiocarbamic acid ameliorated IL-1β-induced proliferation and inflammatory response by inhibiting TLR4/NF-κB signalling. Meanwhile, TRIM52 knockdown inhibited cell proliferation, oxidative stress and inflammatory response in IL-1β-induced SFs through downregulation of TLR4. TRIM52 promoted cell proliferation, inflammatory response, and oxidative stress in IL-1β-induced SFs. The above functions were mediated by the activation of TLR4/NF- κB signal pathway.

Probing the antinociceptive and therapeutic potential of probiotics in managing temporomandibular joint arthritis

This literature review explored the antinociceptive and therapeutic effects of probiotic therapy (PT) in the treatment of arthritic conditions affecting the temporomandibular joint (TMJ). Indexed databases were searched without time and language restrictions up to and including February 2023, to identify studies addressing the question: "Is PT effective for the management of TMJ arthritis?" The following keywords were used in different combinations with Boolean operators: arthritis, osteoarthritis, pain, probiotic, rheumatoid, temporomandibular disorders, and temporomandibular joint. Original clinical and experimental studies assessing the therapeutic efficacy of PT in the management of osteoarthritis were eligible for inclusion. Letters to the editor, reviews, commentaries, perspectives, and expert opinions were not sought. The structure of the current review was tailored to encapsulate relevant information. A total of 297 relevant studies were identified during the initial literature search, and the full text and reference lists of these studies were scrutinized. To date, the potential role of PT in managing osteoarthritis of the TMJ region remains uninvestigated. No clinical trials in the indexed literature have assessed the efficacy of PT in managing TMJ arthritis; however, this finding does not preclude a potential role of probiotics as antinociceptive and therapeutic agents in susceptible populations.

Artificial intelligence-based preventive, personalized and precision medicine for cardiovascular disease/stroke risk assessment in rheumatoid arthritis patients: a narrative review

The challenges associated with diagnosing and treating cardiovascular disease (CVD)/Stroke in Rheumatoid arthritis (RA) arise from the delayed onset of symptoms. Existing clinical risk scores are inadequate in predicting cardiac events, and conventional risk factors alone do not accurately classify many individuals at risk. Several CVD biomarkers consider the multiple pathways involved in the development of atherosclerosis, which is the primary cause of CVD/Stroke in RA. To enhance the accuracy of CVD/Stroke risk assessment in the RA framework, a proposed approach involves combining genomic-based biomarkers (GBBM) derived from plasma and/or serum samples with innovative non-invasive radiomic-based biomarkers (RBBM), such as measurements of synovial fluid, plaque area, and plaque burden. This review presents two hypotheses: (i) RBBM and GBBM biomarkers exhibit a significant correlation and can precisely detect the severity of CVD/Stroke in RA patients. (ii) Artificial Intelligence (AI)-based preventive, precision, and personalized (aiP3) CVD/Stroke risk AtheroEdge™ model (AtheroPoint™, CA, USA) that utilizes deep learning (DL) to accurately classify the risk of CVD/stroke in RA framework. The authors conducted a comprehensive search using the PRISMA technique, identifying 153 studies that assessed the features/biomarkers of RBBM and GBBM for CVD/Stroke. The study demonstrates how DL models can be integrated into the AtheroEdge™-aiP3 framework to determine the risk of CVD/Stroke in RA patients. The findings of this review suggest that the combination of RBBM with GBBM introduces a new dimension to the assessment of CVD/Stroke risk in the RA framework. Synovial fluid levels that are higher than normal lead to an increase in the plaque burden. Additionally, the review provides recommendations for novel, unbiased, and pruned DL algorithms that can predict CVD/Stroke risk within a RA framework that is preventive, precise, and personalized.

Association between axial spondyloarthritis and temporomandibular disorders: A systematic review

This study aimed to assess the frequency of temporomandibular disorders (TMDs) in patients with axial spondyloarthritis (axSpA) compared with the healthy individuals. We systematically searched PubMed, Embase, Scopus, Web of Science, CINAHL, and Google Scholar databases from their inception until 2022, without language restriction. A standardized dataset was used to extract data from the observational studies. Patients were required to have axial spondyloarthritis and clinical and/or radiographic evidence of temporomandibular joint dysfunction. Meta-analysis was performed with a random effects model. A systematic review was registered under number CRD42020206283. We identified seven relevant studies, which provided data for 745 patients and 216 temporomandibular disorders events. The combined odds ratio (OR) showed that the risk of temporomandibular disorders in individuals with axial spondyloarthritis was higher than the control group (pooled OR = 5.26, 95% CI 2.50-11, 06; p < 0.02; I2  = 58%). Also, these individuals do not appear to refer possible temporomandibular joint symptoms to the rheumatologist or dentist. The results of this systematic review and meta-analysis suggest that patients with axial spondyloarthritis have an increased frequency of temporomandibular disorders. TMDs seem to be secondary to postural alterations rather than direct involvement of the temporomandibular joints (TMJs).

Bioinformatics analysis of synovial fluid-derived mesenchymal stem cells in the temporomandibular joint stimulated with IL-1β

The stimulation of interleukin-1β (IL-1β) is the risk factor for temporomandibular joint osteoarthritis (TMJOA). We aim to investigate IL-1β stimulation-related gene and signal pathways in synovial fluid-derived mesenchymal stem cells (SF-MSCs) inflammatory activation to predict the occurrence of TMJOA. The microarray dataset GSE150057 was downloaded from the gene expression omnibus (GEO) database, and principal component analysis (PCA) was performed on the involved genes to obtain differential genes (DEGs). Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway were performed based on the DAVID database. The protein-protein interaction (PPI) network was constructed by the STRING database to identify hub genes. Based on the correlation between differential expression levels of lncRNAs and mRNAs, the co-expression network of lncRNA-mRNA was established. A total of 200 DEGs were obtained. Among 168 differential mRNAs, 126 were up-regulated and 42 were down-regulated; among 32 differential lncRNAs, 23 were up-regulated and 9 were down-regulated. Then, GO analysis showed that DEGs were mainly involved in signal transduction, inflammation, and apoptosis processes. KEGG pathway mainly involved the TNF signaling pathway, NF-κB signaling pathway, NOD-like receptor signaling pathway, and cytokine-cytokine-receptor interaction. Ten hub genes were recognized by PPI analysis, including CXCL8, CCL2, CXCL2, NFKBIA, CSF2, IL1A, IRF1, VCAM1, NFKB1, and TNFAIP3. In conclusion, our study has indicated the role of IL-1β stimulation in the progression of SF-MSCs inflammation and predicted DEGs and downstream pathways.

Influence of TRPV1 on Thermal Nociception in Rats with Temporomandibular Joint Persistent Inflammation Evaluated by the Operant Orofacial Pain Assessment Device (OPAD)

Background

Temporomandibular joint (TMJ)-associated inflammation contributes to the pain reported by patients with temporomandibular disorders (TMD). It is common for patients diagnosed with TMD to report pain in the masticatory muscles and temporomandibular joints, headache, and jaw movement disturbances. Although TMD can have different origins, including trauma and malocclusion disorder, anxiety/depression substantially impacts the development and maintenance of TMD. In general, rodent studies on orofacial pain mechanisms involve the use of tests originally developed for other body regions, which were adapted to the orofacial area. To overcome limitations and expand knowledge in orofacial pain, our group validated and characterized an operant assessment paradigm in rats with both hot and cold stimuli as well mechanical stimuli. Nevertheless, persistent inflammation of the TMJ has not been evaluated with this operant orofacial pain assessment device (OPAD).

Methods

We characterized the thermal orofacial sensitivity for cold, neutral, and hot stimuli during the development of TMD using the OPAD behavior test. In addition, we evaluated the role of transient receptor potential vanilloid 1 (TRPV1) expressing nociceptors in rats with persistent TMJ inflammation. The experiments were performed in male and female rats with TMJ inflammation induced by carrageenan (CARR). Additionally, resiniferatoxin (RTX) was administered into the TMJs prior CARR to lesion TRPV1-expressing neurons to evaluate the role of TRPV1-expressing neurons.

Results

We evidenced an increase in the number of facial contacts and changes in the number of reward licks per stimulus on neutral (37°C) and cold (21°C) temperatures. However, at the hot temperature (42°C), the inflammation did not induce changes in the OPAD test. The prior administration of RTX in the TMJ prevented the allodynia and thermal hyperalgesia induced by CARR.

Conclusion

We showed that TRPV-expressing neurons are involved in the sensitivity to carrageenan-induced pain in male and female rats evaluated in the OPAD.

Sick leave and disability pension among TMD patients with musculoskeletal diseases, mental and behavioural disorders - a SWEREG-TMD population-based cohort study

BACKGROUND

Temporomandibular disorders (TMD) are associated with musculoskeletal diseases (MSD), mental and behavioural disorders (MBD), and patients with TMD have been shown to have 2-3 times more days of sick leave (SL) and disability pension (DP) than the general population. MSD and MBD are two of the most common causes for SL and DP, and the association between TMD and the influence of comorbidities on the need for SL and DP among TMD patients need further clarification. This study investigates the impact of MSD and MBD comorbidity on SL and DP among TMD patients diagnosed in a hospital setting and/or surgically treated.

METHODS

All incident TMD patients diagnosed or treated in a hospital setting between 1998 and 2016 and aged 23-59 were included. A non-exposed comparison cohort was collected from the general population. The cohorts were grouped based on the presence of comorbidity: No comorbidity (Group I); MSD comorbidity (Group II); MBD comorbidity (Group III); and combined MSD and MBD comorbidity (Group IV). Main outcomes were mean annual days of SL and DP, and statistical analysis was conducted using generalized estimated equations.

RESULTS

TMD subjects with no comorbidities (Group I) and with MSD/MBD comorbidity (Group II and III) were 2-3 times more often on SL and DP than the corresponding groups from the general population. However, in the group with both MSD and MBD comorbidity (Group IV), the difference between the TMD subjects and the general population was diminishing, suggesting an additive effect.

CONCLUSION

TMD patients are more dependent on SL and DP benefits compared to general population and the difference remains even after considering MSD and MBD comorbidity. In individuals with combined MSD and MBD comorbidity, concurrent TMD has less impact on the need for social insurance benefits. The results accentuate the impact TMD has on the patients' impaired ability to return to work and why TMD should be recognized as having a substantial impact on individual and economic suffering as well as on societal costs, with emphasis on the influence of comorbidities on patient suffering.

The degeneration-pain relationship in the temporomandibular joint: Current understandings and rodent models

Temporomandibular disorders (TMD) represent a group of musculoskeletal conditions involving the temporomandibular joints (TMJ), the masticatory muscles and associated structures. Painful TMD are highly prevalent and conditions afflict 4% of US adults annually. TMD include heterogenous musculoskeletal pain conditions, such as myalgia, arthralgia, and myofascial pain. A subpopulations of TMD patients show structural changes in TMJ, including disc displacement or degenerative joint diseases (DJD). DJD is a slowly progressing, degenerative disease of the TMJ characterized by cartilage degradation and subchondral bone remodeling. Patients with DJD often develop pain (TMJ osteoarthritis; TMJ OA), but do not always have pain (TMJ osteoarthrosis). Therefore, pain symptoms are not always associated with altered TMJ structures, which suggests that a causal relationship between TMJ degeneration and pain is unclear. Multiple animal models have been developed for determining altered joint structure and pain phenotypes in response to various TMJ injuries. Rodent models of TMJOA and pain include injections to induce inflammation or cartilage destruction, sustained opening of the oral cavity, surgical resection of the articular disc, transgenic approaches to knockout or overexpress key genes, and an integrative approach with superimposed emotional stress or comorbidities. In rodents, TMJ pain and degeneration occur during partially overlapping time periods in these models, which suggests that common biological factors may mediate TMJ pain and degeneration over different time courses. While substances such as intra-articular pro-inflammatory cytokines commonly cause pain and joint degeneration, it remains unclear whether pain or nociceptive activities are causally associated with structural degeneration of TMJ and whether structural degeneration of TMJ is necessary for producing persistent pain. A thorough understanding of the determining factors of pain-structure relationships of TMJ during the onset, progression, and chronification by adopting novel approaches and models should improve the ability to simultaneously treat TMJ pain and TMJ degeneration.

Recent Advances in Animal Models, Diagnosis, and Treatment of Temporomandibular Joint Osteoarthritis

Temporomandibular joint osteoarthritis (TMJOA) is a gradual degenerative jaw joint condition. Until recent years, TMJOA is still relatively unrecognized and ineffective to be treated. Appropriate animal models with reliable detection methods can help researchers understand the pathophysiology of TMJOA and find therapeutic options. In this study, we summarized common animal models of TMJOA created by chemical, surgical, mechanical, and genetical approaches. The relevant pathological symptoms and induction mechanisms were outlined. In addition, different pathological indicators, furthermore, emerging therapeutic regimens, such as intra-articular drug delivery and tissue engineering-based approaches to treat TMJOA based on these animal models, were summarized and updated. Understanding the physiology and pathogenesis of the TMJOA, together using various ways to diagnose the TMJOA, were elaborated, including imaging techniques, molecular techniques for detecting inflammatory cytokines, histochemical staining, and histomorphometry measures. A more reliable diagnosis will enable the development of new prevention and more effective treatment strategies and thereby improve the quality of life of TMJOA patients. Impact statement Temporomandibular joint osteoarthritis (TMJOA) affects 8 to 16 percent of the population worldwide. However, TMJOA is still relatively unrecognized and ineffective to be treated in the clinic. Appropriate animal models with reliable diagnostic methods can help researchers understand the pathophysiology of TMJOA and find therapeutic options. We herein summarized common animal models of TMJOA and various ways to diagnose the TMJOA. More importantly, emerging therapeutic regimens to treat TMJOA based on these animal models were summarized. With the aid of strategies listed, more effective treatment strategies will be developed and thereby improve the life quality of TMJOA patients.

Association between an Increased Serum CCL5 Level and Pathophysiology of Degenerative Joint Disease in the Temporomandibular Joint in Females

Degenerative joint disease of the temporomandibular joints (DJD-TMJ) clinically manifests with symptoms such as orofacial pain, joint sounds and limited jaw movements. Our research group previously reported the functional necessity of a chemokine-chemokine receptor axis of CCL5-CCR5 in osteoclasts. Accumulated studies reported that this axis was involved in the pathogenesis of bone and joint destructive diseases, suggesting CCL5 as a potent biomarker. This study investigated whether or not the serum level of CCL5 can be a biomarker of DJD-TMJ and concomitantly analyzed changes in the serum and urine levels of bone markers to see whether or not changes in the rate of bone metabolism were predisposing. We enrolled 17 female subjects with diagnosed DJD-TMJ and sexually and age-matched 17 controls. The serum CCL5 level in DJD-TMJ subjects was significantly higher than that in the control subjects. Multivariate analyses indicated an association between an augmented CCL5 level and the rate of bone metabolism, especially in relatively young DJD-TMJ subjects without other systemic symptoms. A principal component analysis of serum markers and our pharmacological experiment using a postmenopausal model of ovariectomized rats suggested that an augmented serum CCL5 level specifically reflected DJD-TMJ and that covert changes in the rate of bone metabolism predisposed individuals to DJD-TMJ.

Validity of IL-6 and Arthrocentesis in the Cause and Management of Internal Derangement of TMJ

Purpose

The aim of this clinical study was to evaluate the level of Interleukine-6 (IL-6), pre and post arthrocentesis to validate it as a biomarker in the Internal Derangement (ID) of TMJ.

Material and Methods

This study included 30 patients (20 females and 10 males) of Temporo-Mandibular Dysfunction (TMD) with Disc displacement without reduction (DDwoR) Wilkes stage III, who were refractory to conservative management. Arthrocentesis was performed as a therapeutic modality. Synovial fluid aspirates were obtained prior to arthrocentesis and post arthrocentesis with 300 ml of Ringer Lactate solution into the superior joint compartment for the assessment of level of IL-6. The clinical parameters used for correlating the level of IL-6 were degree of pain (VAS I), chewing ability (VAS II), Maximal Mouth Opening (MMO) in both pre and post op phase with the follow-up period of 01 day, 01 week, 01 month, 03 month and 06 month and the results were compared. ELISA was performed to analyze the levels of IL-6 in the aspirates. The clinical parameters and the level of IL-6 were recorded and analyzed statistically.

Results

The study showed ID of TMJ (Wilkes stage III) s are more prevalent in females especially in the fourth decades of life with the mean age of 38.4 years. The post operative assessment in terms of pain, maximum mouth opening, lateral movements of the mandible and the levels of IL-6 were found to be statistically significant with a P value <0.01.

Conclusion

This study validates the role of IL-6 as a definitive biomarker for the pathogenesis of ID of TMJ Wilkes stage III and arthrocentesis proved to be a minimally invasive therapeutic modality for its management.

Plastic changes in nociceptive pathways contributing to persistent orofacial pain

BACKGROUND

Pain is a warning signal for the body defense mechanisms and is a critical sensation for supporting life. However, orofacial pain is not a vital sensation, but a disease. However, there are still many unclear points about the pathophysiological mechanism of orofacial pain. This situation makes it difficult for many clinicians to treat orofacial pain hypersensitivity.

HIGHLIGHT

Noxious information on the orofacial region received by trigeminal ganglion neurons is recognized as "orofacial pain" by being transmitted to the somatosensory cortex and limbic system via the spinal trigeminal nucleus and the thalamic sensory nuclei. Orofacial inflammation or trigeminal nerve injury causes neuropathic changes in various nociceptive signaling pathways, resulting in persistent orofacial pain. It is considered that persistent oral facial pain is triggered by plastic changes in nociceptive signaling pathways involving various cells such as satellite glial cells, astrocytes, microglia, and macrophages, as well as nociceptive neurons.

CONCLUSION

Recent studies have shown that hyperexcitability of nociceptive neurons in the nociceptive signaling pathways of the orofacial region caused by a variety of factors causes persistent orofacial pain. This review outlines the pathophysiology of orofacial pain along with the results of our study.

Efficacy of the use of chondroitin sulphate and glucosamine for the treatment of temporomandibular joint dysfunction: A systematic review and meta-analysis

OBJECTIVE

To evaluate the efficacy of chondroitin sulfate (CS) and glucosamine (GS), the most relevant drugs of "Symptomatic Slow Acting Drug for Osteoarthritis" (SYSADOA), in the functional and symptomatic improvement of temporomandibular dysfunction. Although, controversy exists regarding their benefit.

METHODS

An electronic search was conducted to retrieve randomized controlled clinical trials (RCTs). The risk of bias assessment was evaluated using the Cochrane Collaboration's tool. Data were meta-analyzed with a random effect model whenever possible.

RESULTS

Three RCTs were included. Qualitative results showed a decrease in pain, joint noise, and inflammatory biomarkers in synovial fluid and an improvement in maximum mouth opening without significant adverse effects. Meta-analysis showed a significant increase in maximum mouth opening with the use of CS-GS (p = 0.19). No statistically significant differences were found in pain reduction compared to tramadol.

CONCLUSION

CS-GS is effective and safe in the symptomatic and functional improvement of patients with TMD.

Biological and Molecular Docking Evaluation of a Benzylisothiocyanate Semisynthetic Derivative From Moringa oleifera in a Pre-clinical Study of Temporomandibular Joint Pain

Objective

Moringa oleifera possesses multiple biological effects and the 4-[(4′-O-acetyl-α-L- rhamnosyloxy) benzyl] isothiocyanate accounts for them. Based on the original isothiocyanate molecule we obtained a semisynthetic derivative, named 4-[(2′,3′,4′-O-triacetyl-α-L-rhamnosyloxy) N-benzyl] hydrazine carbothioamide (MC-H) which was safe and effective in a temporomandibular joint (TMJ) inflammatory hypernociception in rats. Therefore, considering that there is still a gap in the knowledge concerning the mechanisms of action through which the MC-H effects are mediated, this study aimed to investigate the involvement of the adhesion molecules (ICAM-1, CD55), the pathways heme oxygenase-1 (HO-1) and NO/cGMP/PKG/K⁺_ATP, and the central opioid receptors in the efficacy of the MC-H in a pre-clinical study of TMJ pain.

Methods

Molecular docking studies were performed to test the binding performance of MC-H against the ten targets of interest (ICAM-1, CD55, HO-1, iNOS, soluble cGMP, cGMP-dependent protein kinase (PKG), K⁺_ATP channel, mu (μ), kappa (κ), and delta (δ) opioid receptors). In in vivo studies, male Wistar rats were treated with MC-H 1 μg/kg before TMJ formalin injection and nociception was evaluated. Periarticular tissues were removed to assess ICAM-1 and CD55 protein levels by Western blotting. To investigate the role of HO-1 and NO/cGMP/PKG/K⁺_ATP pathways, the inhibitors ZnPP-IX, aminoguanidine, ODQ, KT5823, or glibenclamide were used. To study the involvement of opioid receptors, rats were pre-treated (15 min) with an intrathecal injection of non-selective inhibitor naloxone or with CTOP, naltrindole, or norbinaltorphimine.

Results

All interactions presented acceptable binding energy values (below −6.0 kcal/mol) which suggest MC-H might strongly bind to its molecular targets. MC-H reduced the protein levels of ICAM-1 and CD55 in periarticular tissues. ZnPP-IX, naloxone, CTOP, and naltrindole reversed the antinociceptive effect of MC-H.

Conclusion

MC-H demonstrated antinociceptive and anti-inflammatory effects peripherally by the activation of the HO-1 pathway, as well as through inhibition of the protein levels of adhesion molecules, and centrally by μ and δ opioid receptors.

Cytokines in temporomandibular joint synovial fluid and tissue in relation to inflammation

BACKGROUND

Synovial tissue is known to be the origin of inflammation in joint disease. Despite this, synovial fluid is the main biological specimen of choice in temporomandibular joint (TMJ) inflammation and pathology biomarker research. No comparison of TMJ protein content between synovial fluid and synovial tissue has been made.

OBJECTIVES

To investigate if cytokine concentrations in synovial fluid can be related to cytokine concentrations in synovial tissue, and to analyse correlation of clinical parameters reflecting local inflammation to cytokine concentrations.

METHODS

Synovial tissue and fluid samples were obtained during the same surgical procedure from a cohort of 101 patients with TMJ disorders. Interleukin (IL) 1β, IL-6, IL-8, IL-10, and tumor necrosis factor α (TNF-α) were analysed in the samples and an intraindividual correlation made. Various patient-specific factors relating to TMJ inflammation were associated to the cytokine concentrations in synovial fluid and tissue.

RESULTS

No correlation between cytokine concentration in synovial fluid and synovial tissue was found, except for IL-8 (ρ=.284, P=.024). Synovial tissue cytokines correlated strongly to inflammation-related factors: diagnosis (IL-1β, P=.001; TNF-α, P=.000; IL-10, P=.000), TMJ palpation pain (IL-1β, P=.024; TNF-α, P=.025), synovitis score (IL-1β, P=.015), and subjective TMJ pain (TNF-α, P=.016). Synovial fluid cytokines showed no significant relations to inflammation.

CONCLUSIONS

The investigated cytokine concentrations showed weak correlations between synovial fluid and synovial tissue, besides IL-8. Synovial tissue appeared to reflect inflammation to a higher extent than synovial fluid. Thus, suggesting that synovial tissue research should complement synovial fluid in future explorations of TMJ pathology and inflammation.

Oxygen-Ozone Therapy for Reducing Pro-Inflammatory Cytokines Serum Levels in Musculoskeletal and Temporomandibular Disorders: A Comprehensive Review

To date, the application of oxygen-ozone (O₂O₃) therapy has significantly increased in the common clinical practice in several pathological conditions. However, beyond the favorable clinical effects, the biochemical effects of O₂O₃ are still far from being understood. This comprehensive review aimed at investigating the state of the art about the effects of O₂O₃ therapy on pro-inflammatory cytokines serum levels as a modulator of oxidative stress in patients with musculoskeletal and temporomandibular disorders (TMD). The efficacy of O₂O₃ therapy could be related to the moderate oxidative stress modulation produced by the interaction of ozone with biological components. More in detail, O₂O₃ therapy is widely used as an adjuvant therapeutic option in several pathological conditions characterized by chronic inflammatory processes and immune overactivation. In this context, most musculoskeletal and temporomandibular disorders (TMD) share these two pathophysiological processes. Despite the paucity of in vivo studies, this comprehensive review suggests that O₂O₃ therapy might reduce serum levels of interleukin 6 in patients with TMD, low back pain, knee osteoarthritis and rheumatic diseases with a concrete and measurable interaction with the inflammatory pathway. However, to date, further studies are needed to clarify the effects of this promising therapy on inflammatory mediators and their clinical implications.

Histone deacetylase inhibitors attenuated interleukin-1β-induced chondrogenesis inhibition in synovium-derived mesenchymal stem cells of the temporomandibular joint

Aims

In the repair of condylar cartilage injury, synovium-derived mesenchymal stem cells (SMSCs) migrate to an injured site and differentiate into cartilage. This study aimed to confirm that histone deacetylase (HDAC) inhibitors, which alleviate arthritis, can improve chondrogenesis inhibited by IL-1β, and to explore its mechanism.

Methods

SMSCs were isolated from synovium specimens of patients undergoing temporomandibular joint (TMJ) surgery. Chondrogenic differentiation potential of SMSCs was evaluated in vitro in the control, IL-1β stimulation, and IL-1β stimulation with HDAC inhibitors groups. The effect of HDAC inhibitors on the synovium and condylar cartilage in a rat TMJ arthritis model was evaluated.

Results

Interleukin (IL)-1β inhibited the chondrogenic differentiation potential of SMSCs, while the HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and panobinostat (LBH589), attenuated inhibition of IL-1β-induced SMSC chondrogenesis. Additionally, SAHA attenuated the destruction of condylar cartilage in rat TMJ arthritis model. IL-6 (p < 0.001) and matrix metalloproteinase 13 (MMP13) (p = 0.006) were significantly upregulated after IL-1β stimulation, while SAHA and LBH589 attenuated IL-6 and MMP13 expression, which was upregulated by IL-1β in vitro. Silencing of IL-6 significantly downregulated MMP13 expression and attenuated IL-1β-induced chondrogenesis inhibition of SMSCs.

Conclusion

HDAC inhibitors SAHA and LBH589 attenuated chondrogenesis inhibition of SMSC induced by IL-1β in TMJ, and inhibition of IL-6/MMP13 pathway activation contributes to this biological progress. This study provides a theoretical basis for the application of HDAC inhibitors in the treatment of TMJ arthritis.

Cite this article: Bone Joint Res 2022;11(1):40–48.

Glycyrrhizin regulates rat TMJOA progression by inhibiting the HMGB1-RAGE/TLR4-NF-κB/AKT pathway

To investigate the role of glycyrrhizin on the progression of temporomandibular joint osteoarthritis (TMJOA) and the underlying mechanism by regulation of the high‐mobility group box 1 (HMGB1) receptor for advanced glycation end products (RAGE)/toll‐like receptor 4 (TLR4)‐nuclear factor kappa B (NF‐κB)/protein kinase B (AKT) pathway. After a rat model of TMJOA was built by intra‐articular injection of monosodium iodoacetate, glycyrrhizin was intragastrically administered at low concentration (20 mg/kg) or high concentration (50 mg/kg). Micro‐computed tomography, histological and immunohistochemical analysis were used to reveal the progression of TMJOA. Rat TMJ chondrocytes and disc cells were cultured in inflammatory condition with different doses of glycyrrhizin. Western blot was used to evaluate the effect of glycyrrhizin on the HMGB1‐RAGE/TLR4‐NF‐κB/AKT pathway. Administration of glycyrrhizin alleviated cartilage degeneration, lowered the levels of inflammatory and catabolic mediators and reduced the production of HMGB1, RAGE and TLR4 in TMJOA animal model. Increased production of RAGE and TLR4, and activated intracellular NF‐κB and/or AKT signalling pathways in chondrocytes and disc cells were found in inflammatory condition. Upon activation, matrix metalloprotease‐3 and interleukin‐6 were upregulated. Glycyrrhizin inhibited not only HMGB1 release but also RAGE and TLR4 in inflammatory condition. Glycyrrhizin alleviated the pathological changes of TMJOA by regulating the HMGB1‐RAGE/TLR4‐NF‐kB/AKT signalling pathway. This study revealed the potential of glycyrrhizin as a novel therapeutic drug to suppress TMJ cartilage degradation.

The Role of TNF-α in the Pathogenesis of Temporomandibular Disorders

Temporomandibular disorder (TMD) is an oral dentofacial disease that is related to multiple factors such as disordered dental occlusion, emotional stress, and immune responses. In the past decades, tumor necrosis factor-alpha (TNF-α), a pleiotropic cytokine, has provided valuable insight into the pathogenesis of TMD, particularly in settings associated with inflammation. It is thought that TNF-α participates in the pathogenesis of TMD by triggering immune responses, deteriorating bone and cartilage, and mediating pain in the temporomandibular joint (TMJ). Initially, TNF-α plays the role of "master regulator" in the complex immune network by increasing or decreasing the production of other inflammatory cytokines. Then, the effects of TNF-α on cells, particularly on chondrocytes and synovial fibroblasts, result in pathologic cartilage degradation in TMD. Additionally, multiple downstream cytokines induced by TNF-α and neuropeptides can regulate central sensitization and inflammatory pain in TMD. Previous studies have also found some therapies target TMD by reducing the production of TNF-α or blocking TNF-α-induced pathways. All this evidence highlights the numerous associations between TNF-α and TMD; however, they are currently not fully understood and further investigations are still required for specific mechanisms and treatments targeting specific pathways. Therefore, in this review, we explored general mechanisms of TNF-α, with a focus on molecules in TNF-α-mediated pathways and their potential roles in TMD treatment. In view of the high clinical prevalence rate of TMD and damage to patients' QOL, this review provides adequate evidence for studying links between inflammation and TMD in further research and investigation.

Preclinical models of deep craniofacial nociception and temporomandibular disorder pain

Chronic pain in temporomandibular disorder (TMD) is a common health problem. Cumulating evidence indicates that the etiology of TMD pain is complex with multifactorial experience that could hamper the developments of treatments. Preclinical research is a resource to understand the mechanism for TMD pain, whereas limitations are present as a disease-specific model. It is difficult to incorporate multiple risk factors associated with the etiology that could increase pain responses into a single animal. This article introduces several rodent models which are often employed in the preclinical studies and discusses their validities for TMD pain after the elucidations of the neural mechanisms based on the clinical reports. First, rodent models were classified into two groups with or without inflammation in the deep craniofacial tissues. Next, the characteristics of each model and the procedures to identify deep craniofacial pain were discussed. Emphasis was directed on the findings of the effects of chronic psychological stress, a major risk factor for chronic pain, on the deep craniofacial nociception. Preclinical models have provided clinically relevant information, which could contribute to better understand the basis for TMD pain, while efforts are still required to bridge the gap between animal and human studies.

Mapping the Secretome of Dental Pulp Stem Cells Under Variable Microenvironmental Conditions

There is substantial evidence supporting the anti-inflammatory and regenerative potential of dental pulp stem cells (DPSCs) through direct cell transplantation or paracrine action. However, DPSC secretome profile remains inadequately studied. This study provides proteomic profiling of the human DPSC secretome by comparatively analysising cell lysates and respective culture supernatants (i.e. conditioned media-CM) under variable oxygen tension conditions (normoxia-20% O₂/CM_Norm vs. hypoxia 2% O₂/CM_Hyp) and/or stimulation with Tumor Necrosis Factor alpha (TNF-α). DPSC-CM samples and respective crude lysates (DPSC-CL) were collected and subjected to SDS-PAGE, followed by LC-MS/MS analysis. The identified proteins were analyzed by Gene Ontology, Reactome, and String databases. The anti-inflammatory properties of DPSC-CMs were validated via an in vitro RAW_246.7 murine macrophages model through evaluation of the expression of pro-and anti-inflammatory markers by real-time PCR. Results showed a total of 2413 proteins identified in CM_Norm, 2479 in CM_Norm+TNF-α, 1642 in CM_Hyp, and 2002 in CM_Hyp + TNF-α samples. CM_Norm contained 122 proteins statistically significantly upregulated compared to the CM_Hyp and involved in pathways related to "ECM organization", "cellular response to hypoxia", and "IL signaling". Functional network analysis showed that TGFβ1, TIMP1 and TIMP2 were key nodes among proteins significantly upregulated in the CM_Norm compared to the CM_Hyp, interacting with more than 10 proteins, each. DPSC-CM application in the in vitro RAW_246.7 model decreased the expression of pro-inflammatory markers (MMP-3, MMP-9, MMP-13, MCP-1), while increasing anti-inflammatory markers (IL-10). Overall, DPSC-CM collected under normoxic conditions is enriched with anti-inflammatory, tissue repair and regenerative factors, which prompts further investigation on its therapeutic applications.

The effect of association of aspirin and omega 3 in rat temporomandibular joint with induced arthritis

This study aimed to evaluate the effects of omega-3 (ω3) polyunsaturated fatty acids, in association with aspirin (AA), on the morphology of cytokine release in the temporomandibular joint (TMJ) of rats induced with rheumatoid arthritis (IR) by injecting 100 μL of complete Freund's adjuvant with bovine type II collagen at the tail base. Thirty-two adult male rats were divided into treatment groups: Sham, treated with 0.9% sodium chloride (NaCl) p.o.; IR-control, treated with 0.9% NaCl p.o.; IR-ω3 treated with ω3 PUFAS (85 mg/kg/day p.o.); and IR-ω3 + AA treated with ω3 (85 mg/kg/day p.o.) + AA (20 mg/kg/day i.p.). After maintained treatment for seven days, the animals were euthanized. Bilateral TMJs from each rat were removed and one was subjected to histological immunoassays and enzyme-linked immunosorbent assays to assess interleukin (IL)-1β, tumor necrosis factor-α, and IL-10 levels. Data analysis was performed using the Kruskal-Wallis and Dunn tests. In the IR-ω3 and IR-ω3 + AA groups, the TMJ was greater than in the IR-control group (P < 0.0001). The addition of AA did not improve the effects of ω3 (P = 0.0698). Similarly, the addition of AA conferred no additional effects on the cytokine levels (P > 0.05); however, it increased the proteoglycan density, compared with ω3 alone. We found that ω3 exhibited anti-inflammatory activity in arthritic rats, and the addition of AA increased proteoglycan density, but did not affect cytokine expression.

Selonsertib Alleviates the Progression of Rat Osteoarthritis: An in vitro and in vivo Study

Osteoarthritis (OA) is a prevalent degenerative joint disease. Its development is highly associated with inflammatory response and apoptosis in chondrocytes. Selonsertib (Ser), the inhibitor of Apoptosis Signal-regulated kinase-1 (ASK1), has exhibited multiple therapeutic effects in several diseases. However, the exact role of Ser in OA remains unclear. Herein, we investigated the anti-arthritic effects as well as the potential mechanism of Ser on rat OA. Our results showed that Ser could markedly prevent the IL-1β-induced inflammatory reaction, cartilage degradation and cell apoptosis in rat chondrocytes. Meanwhile, the ASK1/P38/JNK and NFκB pathways were involved in the protective roles of Ser. Furthermore, intra-articular injection of Ser could significantly alleviate the surgery induced cartilage damage in rat OA model. In conclusion, our work provided insights into the therapeutic potential of Ser in OA, indicating that Ser might serve as a new avenue in OA treatment.

Transcriptomes in peripheral blood of young females with temporomandibular joint osteoarthritis

This study aimed to investigate immune-related pathophysiology of the temporomandibular joint (TMJ) osteoarthritis (OA) in young females by analyzing transcriptional profiles of peripheral blood mononuclear cells. The RNA-sequencing (RNA-seq) was conducted on 24 young females with TMJ OA (mean age 19.3 ± 3.1 years) (RNAOA) and 11 age and sex matched healthy controls (mean age 20.5 ± 3.7 years) (CON). RNA-seq datasets were analyzed to identify genes, pathways, and regulatory networks of those which were involved in the development of TMJ OA. RNA-seq data analysis revealed 41 differentially expressed genes (DEGs) between RNAOA and CON. A total of 16 gene ontology (GO) terms including three molecular and 13 biological terms were annotated via the GO function of molecular function and biological process. Through ingenuity pathway analysis (IPA), 21 annotated categories of diseases and functions were identified. There were six hub genes which showed significant results in both GO enrichment analysis and IPA, namely HLA-C, HLA-F, CXCL8, IL11RA, IL13RA1, and FCGR3B. The young females with TMJ OA showed alterations of the genes related to immune function in the blood and some of changes may reflect inflammation, autoimmunity, and abnormal T cell functions.

Bidirectional relationship between temporomandibular disorder and ankylosing spondylitis: a population-based cohort study

OBJECTIVES

This study aimed to determine the relation between temporomandibular disorder (TMD) and ankylosing spondylitis (AS) bidirectionally and ascertain the important comorbidities for AS occurrence in TMD patients.

MATERIALS AND METHODS

We conducted this population-based cohort study through Longitudinal Health Insurance Database, Taiwan. Study 1 investigated the risk of TMD in AS patients. Study 2 assessed the risk of AS in TMD patients.

RESULTS

In total, 3204 AS patients and 12,816 age-matched and gender-matched comparisons were enrolled in study 1. The TMD incidence in the AS cohort was 2.88-fold higher when compared with the comparisons (1.54 vs. 0.53 per 10,000 person-years). After adjusting for age, gender, and comorbidity, the AS cohort had a 2.66-fold (95% CI = 1.79-3.97) increased risk of TMD occurrence (P < 0.0001). The second study recruited 4998 TMD patients and 19,991 age-matched and gender-matched comparisons. Both TMD and comparison cohorts showed similar AS risk (HR = 1.49, 95% CI = 0.91-2.43, P = 0.1108) in the adjusted model. Study 2 identified a 3.66-fold increased risk of AS occurrence in TMD patients with comorbidity, including parapsoriasis, rheumatoid arthritis, osteoporosis, Cushing's syndrome, and climacteric arthritis (P < 0.012).

CONCLUSIONS

AS appears to significantly impact the occurrence of TMD. TMD might play a synergic role in AS development.

CLINICAL RELEVANCE

Clinicians have to be vigilant about the increased risk of TMD in AS patients and take care of AS disease activity and prognosis. The symptoms and signs of TMD could be a predictor of AS in patients with the aforementioned comorbidities.

Herbal Composition LI73014F2 Alleviates Articular Cartilage Damage and Inflammatory Response in Monosodium Iodoacetate-Induced Osteoarthritis in Rats

The aim of this study was to determine the anti-osteoarthritic effects of LI73014F2, which consists of Terminalia chebula fruit, Curcuma longa rhizome, and Boswellia serrata gum resin in a 2:1:2 ratio, in the monosodium iodoacetate (MIA)-induced osteoarthritis (OA) rat model. LI73014F2 was orally administered once per day for three weeks. Weight-bearing distribution and arthritis index (AI) were measured once per week to confirm the OA symptoms. Synovial membrane, proteoglycan layer, and cartilage damage were investigated by histological examination, while synovial fluid interleukin-1β level was analyzed using a commercial kit. Levels of pro-inflammatory mediators/cytokines and matrix metalloproteinases (MMPs) in the cartilage tissues were investigated to confirm the anti-osteoarthritic effects of LI73014F2. LI73014F2 significantly inhibited the MIA-induced increase in OA symptoms, synovial fluid cytokine, cartilage damage, and expression levels of pro-inflammatory mediators/cytokines and MMPs in the articular cartilage. These results suggest that LI73014F2 exerts anti-osteoarthritic effects by regulating inflammatory cytokines and MMPs in MIA-induced OA rats.

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.

MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders

This research aimed to identify differences in polypeptide/protein profiles of the unstimulated whole saliva between patients with temporomandibular joint disorders (TMDs) and healthy individuals. A fraction of the polypeptides/proteins (<30 kDa) was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The spectra were recovered from methanoic acid/acetonitrile salivary samples overlaid with an α-cyano-4-hydroxy-cinnamic acid matrix in positive linear mode at an interval of 1,500–20,000 m/z mass acquisition range. The data were analyzed for the selection of characteristic peaks by using the ClinProTools 3.0 software. Discriminative classification models were generated by using a quick classifier, supervised neural network, and genetic algorithms. From the 23 peaks exhibiting the highest discriminatory power, the ten top-scored peaks with the area under the receiver operating characteristic >0.8 were selected. A panel of salivary markers that predicted the patients with TMDs was selected (2728.0, 4530.2, 5174.2, 5193.3, 6303.4, 6886.7, 8141.7, 8948.7, 10663.2, 10823.7 and 11009.0 m/z). Although carried out on relatively small datasets, the classification algorithm used in this study allows the differentiation between salivary samples from subjects with TMDs and healthy individuals and confirms the usefulness of a proteomic profiling approach in the monitoring of the disease.

Synovial tissue cytokine profile in disc displacement of the temporomandibular joint

BACKGROUND

Symptomatic disc displacement (DD) of the temporomandibular joint (TMJ) may cause pain and limited mouth opening. The aetiopathogenesis is obscure and probably complex, which makes the diagnostic classification crude and mainly based on clinical criteria rather than disease mechanisms, and tissue characteristics.

OBJECTIVES

The study aim was to characterise and quantify synovial tissue in DD, where specific cytokine patterns might serve as potential biomarkers.

METHODS

An observational cohort study was performed harvesting synovial tissue from 63 patients: 44 with DD without reduction (DDwoR) and 19 with DD with reduction (DDwR). DDwoR was subdivided depending on type of onset (sudden, n = 17; delayed, n = 27), and DDwR served as the control group. Proteins were extracted from tissue samples and investigated in a multi-analytic profiling system.

RESULTS

DDwoR patients had significantly higher concentrations in 12 out of 28 analysed cytokines compared to DDwR. In the same statistical model, significantly lower concentrations of interferon gamma-induced protein (IP) 10, osteoprotegerin (OPG) and RANTES were detected in DDwoR patients. Women showed significantly higher concentrations of epidermal growth factor and interleukin (IL) 1ra compared to men. DDwoR with sudden onset had significant higher concentrations of bone morphogenetic protein 4, eotaxin and IL-8 compared to DDwoR with delayed onset.

CONCLUSIONS

Characterising the biomarker panel for TMJ conditions may serve as suggestible targets for disease classification and novel treatment options. The significantly lower concentrations of IP-10, OPG and RANTES could be proposed as putative markers for the separation of the studied conditions to other TMJ diseases.

Increased chemokine RANTES in synovial fluid and its role in early-stage degenerative temporomandibular joint disease

BACKGROUND

Degenerative joint disease (DJD) of the temporomandibular joints (TMJs) in adolescents and young adults is closely associated with disc displacement without reduction (DDw/oR).

OBJECTIVE

This study aimed to determine the pathogenesis of early-stage TMJ DJD induced by DDw/oR.

METHODS

31 female subjects aged 12-30 years were enrolled, comprising 12 patients with DDw/oR without DJD, 13 with DDw/oR and early-stage DJD, and 6 healthy volunteers. The synovial fluid samples of the subjects were screened for 27 inflammatory-related cytokines using multiple cytokine array. Significantly increased cytokines and a key regulator of osteoclastogenesis "receptor activator of nuclear factor-κB ligand" (RANKL) were further determined by sandwich immunoassay. These factors were also assessed for the possible pathophysiologic actions on RAW264.7 cell proliferation, migration, osteoclastogenesis and bone-resorbing activity using Cell Counting Kit-8, Transwell system, tartrate-resistant acid phosphatase staining and osteo assay plates.

RESULTS

Macrophage-derived inflammatory protein-1 beta (MIP-1β) and regulated upon activation normal T cell expressed and secreted (RANTES) were found to vary significantly in relation to the controls. In contrast to an unchanged concentration of RANKL, a strong increase in the level of RANTES was detected in subjects with DDw/oR and early-stage DJD. MIP-1β concentrations were only elevated in subjects with DDw/oR without DJD. Functionally, both MIP-1β and RANTES could enhance macrophage migration in a concentration-dependent manner, while only RANTES exhibited a promoting effect on osteoclast formation and bone-resorbing activity.

CONCLUSIONS

Chemokine RANTES was significantly upregulated and might be a key regulator of osteoclastogenesis contributing to DDw/oR-induced early-stage TMJ DJD.

Osteoarthritis of the Temporomandibular Joint can be diagnosed earlier using biomarkers and machine learning

After chronic low back pain, Temporomandibular Joint (TMJ) disorders are the second most common musculoskeletal condition affecting 5 to 12% of the population, with an annual health cost estimated at $4 billion. Chronic disability in TMJ osteoarthritis (OA) increases with aging, and the main goal is to diagnosis before morphological degeneration occurs. Here, we address this challenge using advanced data science to capture, process and analyze 52 clinical, biological and high-resolution CBCT (radiomics) markers from TMJ OA patients and controls. We tested the diagnostic performance of four machine learning models: Logistic Regression, Random Forest, LightGBM, XGBoost. Headaches, Range of mouth opening without pain, Energy, Haralick Correlation, Entropy and interactions of TGF-β1 in Saliva and Headaches, VE-cadherin in Serum and Angiogenin in Saliva, VE-cadherin in Saliva and Headaches, PA1 in Saliva and Headaches, PA1 in Saliva and Range of mouth opening without pain; Gender and Muscle Soreness; Short Run Low Grey Level Emphasis and Headaches, Inverse Difference Moment and Trabecular Separation accurately diagnose early stages of this clinical condition. Our results show the XGBoost + LightGBM model with these features and interactions achieves the accuracy of 0.823, AUC 0.870, and F1-score 0.823 to diagnose the TMJ OA status. Thus, we expect to boost future studies into osteoarthritis patient-specific therapeutic interventions, and thereby improve the health of articular joints.

FlexPro MD®, a Combination of Krill Oil, Astaxanthin and Hyaluronic Acid, Reduces Pain Behavior and Inhibits Inflammatory Response in Monosodium Iodoacetate-Induced Osteoarthritis in Rats

Osteoarthritis (OA) is a degenerative joint disease and a leading cause of adult disability. Since there is no cure for OA and no effective treatment to slow its progression, current pharmacologic treatments, such as analgesics and non-steroidal anti-inflammatory drugs (NSAIDs), only alleviate symptoms, such as pain and inflammation, but do not inhibit the disease process. Moreover, chronic intake of these drugs may result in severe adverse effects. For these reasons, patients have turned to the use of various complementary and alternative approaches, including diverse dietary supplements and nutraceuticals, in an effort to improve symptoms and manage or slow disease progression. The present study was conducted to evaluate the anti-osteoarthritic effects of FlexPro MD^® (a mixture of krill oil, astaxanthin, and hyaluronic acid; FP-MD) in a rat model of OA induced by monosodium iodoacetate (MIA). FP-MD significantly ameliorated joint pain and decreased the severity of articular cartilage destruction in rats that received oral supplementation for 7 days prior to MIA administration and for 21 days thereafter. Furthermore, FP-MD treatment significantly reduced serum levels of the articular cartilage degeneration biomarkers cartilage oligomeric matrix protein (COMP) and crosslinked C-telopeptide of type II collagen (CTX-II), and the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), as well as mRNA expression levels of inflammatory mediators, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and matrix-degrading enzymes, matrix metalloproteinase (MMP)-2 and MMP-9, in the knee joint tissue. Our findings suggest that FP-MD is a promising dietary supplement for reducing pain, minimizing cartilage damage, and improving functional status in OA, without the disadvantages of previous dietary supplements and medicinal agents, including multiple adverse effects.

LncRNA PVT1 induces chondrocyte apoptosis through upregulation of TNF-α in synoviocytes by sponging miR-211-3p

Temporomandibular joint osteoarthritis (TMJ OA) is an important subtype of temporomandibular disorders (TMD). Articular cartilage destruction is considered a common pathological feature of TMJ OA, which is reported to be mainly induced by chondrocyte apoptosis. Synovial sterile inflammation is an initial factor of TMJ OA-associated articular cartilage destruction. Therefore, determining the mechanism of synovial membrane inflammation-induced articular cartilage destruction in TMJ OA is important for the TMJ OA therapy. In this study, we detected the function of synoviocytes in chondrocyte apoptosis under lipopolysaccharide (LPS)-induced inflammatory conditions and explored the underlying mechanism. We found that synoviocytes in inflammatory conditions facilitated LPS-induced chondrocytes apoptosis by secreting increased Tumor Necrosis Factor α (TNF-α), which was induced by long non-coding RNA plasmacytoma variant translocation 1 (PVT1) upregulation. PVT1 served as a competing endogenous RNA that sponged the microRNA miR-211-3p and prevented the inhibition of TNF-α expression. In conclusion, our in vitro study revealed that PVT1 has a previously unknown role in chondrocyte apoptosis, which may also be a mechanism underlying synoviocyte involvement in TMJ OA.

DPSCs Attenuate Experimental Progressive TMJ Arthritis by Inhibiting the STAT1 Pathway

Severe inflammation, progressive cartilage, and bone destruction are typical pathologic changes in temporomandibular joint (TMJ) arthritis and lead to great difficulty for treatment. However, current therapy is inefficient to improve degenerative changes in progressive TMJ arthritis. This study investigated the therapeutic effects of human dental pulp stem cells (DPSCs) on severe inflammatory TMJ diseases. Progressive TMJ arthritis in rats was induced by intra-articular injection of complete Freund's adjuvant and monosodium iodoacetate. DPSCs were injected into the articular cavity to treat rat TMJ arthritis, with normal saline injection as control. Measurement of head withdrawal threshold, micro-computed tomography scanning, and histologic staining were applied to evaluate the severity of TMJ arthritis. Results showed that local injection of DPSCs in rats with TMJ arthritis relieved hyperalgesia and synovial inflammation, attenuated cartilage matrix degradation, and induced bone regeneration. Inflammatory factors TNF-α and IFN-γ were elevated in progressive TMJ arthritis and partially decreased by local injection of DPSCs. MMP3 and MMP13 were elevated in the arthritis + normal saline group and decreased in the arthritis + DPSCs group, which indicated amelioration of matrix degradation. The isolated primary synoviocytes were cocultured with DPSCs after inflammatory factors stimulated to explore the possible biological mechanisms. The expression of MMP3 and MMP13 in synoviocytes was elevated after TNF-α and IFN-γ stimulation and partially reversed by DPSC treatment in the in vitro study. The signal transducer and activator of transcription 1 (STAT1) was activated by inflammatory stimulation and suppressed by DPSC coculture. The upregulation of MMP3 and MMP13 triggered by inflammation was blocked by STAT1-specific inhibitor, suggesting that STAT1 regulated the expression of MMP3 and MMP13. In conclusion, this study demonstrated the possible therapeutic effects of local injection of DPSCs on progressive TMJ arthritis by inhibiting the expression of MMP3 and MMP13 through the STAT1 pathway.

Extracellular matrix turnover and inflammation in chemically-induced TMJ arthritis mouse models

The temporomandibular joint (TMJ) is a fibrocartilaginous tissue critical for chewing and speaking. In patients with temporomandibular disorders (TMDs), permanent tissue loss can occur. Recapitulating the complexity of TMDs in animal models is difficult, yet critical for the advent of new therapies. Synovial fluid from diseased human samples revealed elevated levels of tumor necrosis factor alpha (TNF-alpha). Here, we propose to recapitulate these findings in mice by subjecting murine TMJs with TNF-alpha or CFA (Complete Freund’s Adjuvant) in mandibular condyle explant cultures and by local delivery in vivo using TMJ intra-articular injections. Both TNF-alpha and CFA delivery to whole mandibular explants and in vivo increased extracellular matrix deposition and increased cartilage thickness, while TNF-alpha treated explants had increased expression of inflammatory cytokines and degradative enzymes. Moreover, the application of TNF-alpha or CFA in both models reduced cell number. CFA delivery in vivo caused soft tissue inflammation, including pannus formation. Our work provides two methods of chemically induced TMJ inflammatory arthritis through a condyle explant model and intra-articular injection model that replicate findings seen in synovial fluid of human patients, which can be used for further studies delineating the mechanisms underlying TMJ pathology.

Experimental Methods to Inform Diagnostic Approaches for Painful TMJ Osteoarthritis

Temporomandibular joint (TMJ) osteoarthritis (OA) is a degenerative disease of the joint that can produce persistent orofacial pain as well as functional and structural changes to its bone, cartilage, and ligaments. Despite advances in the clinical utility and reliability of the Diagnostic Criteria for Temporomandibular Disorders, clinical tools inadequately predict which patients will develop chronic TMJ pain and degeneration, limiting clinical management. The challenges of managing and treating TMJ OA are due, in part, to a limited understanding of the mechanisms contributing to the development and maintenance of TMJ pain. OA is initiated by multiple factors, including injury, aging, abnormal joint mechanics, and atypical joint shape, which can produce microtrauma, remodeling of joint tissues, and synovial inflammation. TMJ microtrauma and remodeling can increase expression of cytokines, chemokines, and catabolic factors that damage synovial tissues and can activate free nerve endings in the joint. Although studies have separately investigated inflammation-driven orofacial pain, acute activity of the trigeminal nerve, or TMJ tissue degeneration and/or damage, the temporal mechanistic factors leading to chronic TMJ pain are undefined. Limited understanding of the interaction between degeneration, intra-articular chemical factors, and pain has further restricted the development of targeted, disease-modifying drugs to help patients avoid long-term pain and invasive procedures, like TMJ replacement. A range of animal models captures features of intra-articular inflammation, joint overloading, and tissue damage. Although those models traditionally measure peripheral sensitivity as a surrogate for pain, recent studies recognize the brain's role in integrating, modulating, and interpreting nociceptive inputs in the TMJ, particularly in light of psychosocial influences on TMJ pain. The articular and neural contributors to TMJ pain, imaging modalities with clinical potential to identify TMJ OA early, and future directions for clinical management of TMJ OA are reviewed in the context of evidence in the field.

Sustained and repeated mouth opening leads to development of painful temporomandibular disorders involving macrophage/microglia activation in mice

Temporomandibular disorder (TMD) is a set of heterogeneous musculoskeletal conditions involving the temporomandibular joint (TMJ) and/or the masticatory muscles. Up to 33% of the population has had at least 1 symptom of TMD with 5% to 10% of them requiring treatment. Common symptoms include limited jaw movement, joint sound, and pain in the orofacial area. Once TMD becomes chronic, it can be debilitating with comorbidities that greatly reduce one's overall quality of life. However, the underlying mechanism of TMD is unclear because of the multicausative nature of the disease. Here, we report a novel mouse model of TMD where a bite block was placed in between the upper and lower incisors such that the mouth was kept maximally open for 1.5 hours per day for 5 days. After sustained mouth opening, mice developed persistent orofacial mechanical allodynia and TMJ dysfunction. At the cellular level, we found masseter muscle dystrophy, and increased proteoglycan deposition and hypertrophic chondrocytes in the mandibular condyle. Increased F4/80 macrophages were also observed in the masseter muscles and the TMJ posterior synovium. We also found ATF3 neuronal injury and increased F4/80 macrophages in the trigeminal ganglia. Microglia activation was observed in the trigeminal subnucleus caudalis. Inhibiting macrophage and microglia activation with a colony stimulating factor-1 receptor inhibitor prevented the development of orofacial mechanical allodynia, but not TMJ dysfunction. This study suggests that mouth opening for an extended period during dental treatments or oral intubations may risk the development of chronic TMD and inflammation associated with macrophage and microglia in the tissue and trigeminal system contributes to the development of TMD pain.

Leptin Levels in the Synovial Fluid of Patients With Temporomandibular Disorders

PURPOSE

This study was conducted to measure concentrations of leptin and interleukin-6 (IL-6) in the synovial fluid (SF) of 38 patients with temporomandibular disorders (TMDs) and 7 healthy controls and to analyze the correlation between leptin and IL-6.

PATIENTS AND METHODS

Patients with TMDs were divided into 3 subgroups according to imaging and clinical findings: displaced disc with reduction (DDR; n = 12), displaced disc without reduction (DDNR; n = 13), and osteoarthritis (OA; n = 13). SF samples were collected, and leptin and IL-6 levels were measured by enzyme-linked immunosorbent assay.

RESULTS

No relevant difference in leptin level was found between the control group and the DDR or DDNR group, whereas the OA group presented a higher leptin concentration than all other groups. IL-6 concentrations were markedly higher in all patient groups than in the control group. Levels were markedly higher in the OA group than in the DDR or DDNR group, but no relevant differences were found between the DDR and DDNR groups. No relevant correlation was found between leptin and IL-6 concentrations.

CONCLUSION

Distinct changes in leptin and IL-6 concentrations in the SF occurred at different stages of TMDs, suggesting their potential role in the pathogenesis of TMDs.

Selection and Investigation of a Primate Model of Spontaneous Degenerative Knee Osteoarthritis, the Cynomolgus Monkey (Macaca Fascicularis)

BACKGROUND The aim of this study was to identify a primate model of degenerative knee osteoarthritis (KOA) that may be more relevant for research studies on degenerative KOA in humans. MATERIAL AND METHODS Sixteen specific-pathogen-free (SPF) male cynomolgus monkeys (Macaca fascicularis) were divided into group A (n=8), an old group (22.0-25.3 years of age), and group B (n=8), a young group (3.0-5.2 years of age). For each primate, the behavior was observed, knee circumference was measured, knee joint X-rays were performed, and peripheral blood white blood cell (WBC) counts were measured, and the Kellgren and Lawrence (K-L) system was used for the classification of osteoarthritis. An enzyme-linked immunoassay (ELISA) was performed on knee joint fluid to measure levels of interleukin (IL)-1β, transforming growth factor (TGF)-β1, and matrix metalloproteinase (MMP)13. Changes in articular cartilage were evaluated using the Brittberg score and the Mankin histopathology grading score, respectively. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot were used to measure the expression of the NOTCH3, JAG1, and ACAN genes in knee cartilage specimens, and the findings in the two groups of primates were compared. RESULTS Seven old aged primates in group A were compared with group B, and showed significant differences in WBC count, synovial fluid IL-1β, TGF-β1, and MMP13 levels, expression levels of the NOTCH3, JAG1, and ACAN genes in knee cartilage specimens, and in the Brittberg and Mankin scores (all, P<0.05). CONCLUSIONS Cynomolgus monkeys (Macaca fascicularis) might be a model for age-related degenerative KOA.

Th1/Th17/Th22 immune response and their association with joint pain, imagenological bone loss, RANKL expression and osteoclast activity in temporomandibular joint osteoarthritis: A preliminary report

It is well accepted that the presence of cytokines belonging to the Th1/Th17/Th22 axis of immuno-inflammatory response in the joint environment, such as IL-1β, IL-17 and IL-22, respectively, are associated with pathogenesis of several synovial joint degenerative disorders. During temporomandibular joint osteoarthritis (TMJ-OA), IL-1β and IL-17 have been implicated in the inflammation and resorption of sub-chondral bone; however, the role of Th22 response in the TMJ-OA pathophysiology has not been established. This study aimed to compare the expression of Th1/Th17/Th22-type cytokines, chemokines and chemokine receptors in synovial fluid samples obtained from TMJ-OA or disk displacement with reduction (DDWR) patients. In addition, it aimed to associate these levels with joint pain, imagenological signs of bone degeneration, RANKL production, osteoclastogenesis and osteoclast-induced bone resorption. Higher levels of IL-1β, IL-17 and IL-22 were expressed in TMJ-OA compared with DDWR subjects, and these increased levels significantly correlated with RANKL expression, joint pain and articular bone degeneration. Higher levels of CCR5, CCR6 and CCR7, as well as their respective ligands CCL5 and CCL20, responsible for recruitment of IL-1β, IL-17 and IL-22-producing cells, were over-expressed in TMJ-OA compared with DDWR subjects. Osteoclastogenesis and osteoclast-induced bone resorption were significantly greater in presence of synovial fluid from TMJ-OA compared with DDWR subjects. These data demonstrate that cytokines, CCLs and CCRs associated with the Th1/Th17/Th22 axis of immuno-inflammatory response are involved in TMJ-OA pathogenesis. These findings suggest that IL-22 is involved in the RANKL expression in TMJ-OA, which in turn induces differentiation of osteoclasts and subsequent resorption of sub-chondral bone.

Anesthetic drug propofol inhibits the expression of interleukin-6, interleukin-8 and cyclooxygenase-2, a potential mechanism for propofol in suppressing tumor development and metastasis

Previous studies have indicated that anesthesia-associated drugs may directly inhibit cellular immunity and humoral immunity, which may be associated with tumor recurrence. The present study demonstrated that propofol may suppress the proliferation of MCF-7 cells and inhibit the expression of interleukin (IL)-6 and IL-8. Subsequent to treatment with propofol, MCF-7 cells demonstrated downregulated cyclooxygenase-2 (COX-2) protein expression and decreased levels of vascular endothelial growth factor and prostaglandin E2 in the supernatant. Therefore, the mechanism of propofol in suppressing tumor development and metastasis may be associated with the inhibition of IL-6, IL-8 and COX-2.

TNFα in the Trigeminal Nociceptive System Is Critical for Temporomandibular Joint Pain

Previous studies have shown that tumor necrosis factor alpha (TNFα) is significantly increased in complete Freund's adjuvant (CFA)-treated temporomandibular joint (TMJ) tissues. However, it is unclear whether TNFα in the trigeminal nociceptive system contributes to the development of TMJ pain. In the present study, we investigated the role of TNFα in trigeminal ganglia (TG) and spinal trigeminal nucleus caudalis (Sp5C) in CFA-induced inflammatory TMJ pain. Intra-TMJ injection of CFA (10 μl, 5 mg/ml) induced inflammatory pain in the trigeminal nerve V2- and V3-innervated skin areas of WT mice, which was present on day 1 after CFA and persisted for at least 10 days. TNFα in both TG and Sp5C of WT mice was upregulated after CFA injection. The CFA-induced TMJ pain was significantly inhibited in TNFα KO mice. The immunofluorescence staining showed that intra-TMJ CFA injection not only enhanced co-localization of TNFα with Iba1 (a marker for microglia) in both TG and Sp5C but also markedly increased the expression of TNFα in the Sp5C neurons. By the methylated DNA immunoprecipitation assay, we also found that DNA methylation at the TNF gene promoter region in the TG was dramatically diminished after CFA injection, indicating that epigenetic regulation may be involved in the CFA-enhanced TNFα expression in our model. Our results suggest that TNFα in the trigeminal nociceptive system plays a critical role in CFA-induced inflammatory TMJ pain.