Validation of a chemical osteoarthritis model in rabbit temporomandibular joint: a compliment to biomechanical models

NG2/CSPG4 attenuates motility in mandibular fibrochondrocytes under serum starvation conditions

The migration of mandibular fibrochondrocytes is important for the development of the mandible, the homeostasis of the mandibular cartilage, and for the capacity of the tissue to respond to injury. Mandibular fibrochondrocytes have to overcome formidable obstacles during migration including a dense and heterogeneous three-dimensional matrix. Guiding the direction of cell migration and commitment to a migratory phenotype in this microenvironment necessitates a multivalent response to chemotactic and extracellular matrix-mediated stimuli. One of the key matrix components in the cartilage of the temporomandibular joint is type VI collagen. Neuron/glial antigen 2 (NG2/CSPG4) is a transmembrane proteoglycan that binds with collagen VI and has been implicated in a wide range of cell behaviors including cell migration, motility, adhesion, and proliferation. While NG2/CSPG4 has been shown to be a key regulator of mandibular cartilage homeostasis, its role in the migration of mandibular fibrochondrocytes during normal and cell stress conditions has yet to be resolved. Here, we address this gap in knowledge by characterizing NG2/CSPG4-dependent migration in mandibular fibrochondrocytes using primary mandibular fibrochondrocytes isolated from control and full length NG2/CSPG4 knockout mice, in primary mandibular fibrochondrocytes isolated from NG2|DsRed reporter mice and in an immortalized mandibular fibrochondrocyte cell line with a mutated NG2/CSPG4 ectodomain. All three cells demonstrate similar results, with loss of the full length or truncated NG2/CSPG4 increasing the rate of cell migration in serum starvation/cell stress conditions. These findings clearly implicate NG2/CSPG4 as a key molecule in the regulation of cell migration in mandibular fibrochondrocytes in normal and cell stress conditions, underscoring the role of NG2/CSPG4 as a mechanosensitive signaling hub in the mandibular cartilage.

Effective Technical Protocol for Producing a Mono-Iodoacetate-Induced Temporomandibular Joint Osteoarthritis in a Rat Model

An animal model of osteoarthritis (OA) induced by monosodium iodoacetate (MIA) can be effectively adjusted based on the concentration of MIA to control the onset, progression, and severity of OA as required. The rat temporomandibular joint osteoarthritis (TMJOA) model using MIA is a useful tool for studying the effectiveness of disease-modifying OA drugs in TMJOA research. However, the intricate and complex anatomy of the rat TMJ often poses challenges in achieving consistent TMJOA induction during experiments. In the previous article, a reference point was established by drawing parallel lines based on the line connecting the external ear and the zygomatic arch. However, this is not suitable for the anatomical characteristics of the rat. We used the zygomatic arch as a reference, which is a technical protocol that considers it. In our protocol, we designated a point ∼1 mm away from the point where the zygomatic arch bends toward the ear as the injection site. To ensure precise injection of MIA and increase the likelihood of inducing OA, it is recommended to insert the needle at a 45° angle so that the needle tip contacts the joint projection. To confirm TMJOA induction, we identified changes in the condyle using in vivo microcomputed tomography (CT) in a rat model of MIA-induced OA and measured the degree of pain-related inflammation using head withdrawal threshold (HWT) measurements. Micro-CT scanning revealed typical OA-like lesions, including degenerative changes and subchondral bone remodeling induced by MIA in the TMJ. Pain, a major clinical feature of OA, showed an appropriate response corresponding to the structural changes shown in micro-CT scanning. In addition, the MIA concentration suitable for long-term observation of lesions was determined through ex vivo micro-CT imaging and HWT measurements. The 8 mg concentration exhibited a significant difference compared with others, confirming the sustained presence of lesions, particularly through changes in subchondral bone over an extended period. Consequently, we have successfully established a reliable rat TMJOA induction model and identified the MIA concentration suitable for long-term observation of subchondral bone research, which will greatly contribute to the study of TMJOA-an incurable disease lacking specific treatment options. The Clinical Trial Registration number is 2021-12-208.

Therapeutic effect of alendronate in an experimental temporomandibular joint osteoarthritis

BACKGROUND

Temporomandibular joint osteoarthritis is a common degenerative joint disease. This disease negatively affects the daily life, speech and chewing functions of patients.

OBJECTIVE

This study aimed to evaluate the effects of intra-articular injection of alendronate to osteoarthritis, which has a protective effect on bone and cartilage tissue and helps reduce inflammation in temporomandibular joint osteoarthritis.

METHODS

A total of 24 Wistar albino rats were used in the study. Rats were divided into four groups: study, saline, control and sham. In both saline and control groups, monosodium iodoacetate was injected intra-articularly to induce osteoarthritis. Alendronate was administered intra-articularly to the study group weekly for 4 weeks. In the saline group, saline was administered by intra-articular injection. At the end of the 12th week, all groups were sacrificed. Mandibular condyle tissues were examined histopathologically.

RESULTS

According to the results, osteoarthritic changes in the control group were higher than those in the study group (p < .05). No significant reduction in osteoarthritic changes was observed in the saline group (p > .05). Significant osteoarthritis findings were observed in all groups compared with the sham group (p < .05).

CONCLUSION

Intra-articular injection of alendronate was found to have positive results on TMJ osteoarthritis. In addition, it was seen that alendronate has effects on reducing cartilage tissue degeneration and loss of matrix proteins.

Animal Models of Temporomandibular Joint Osteoarthritis: Classification and Selection

Temporomandibular joint osteoarthritis (TMJOA) is a common degenerative joint disease that can cause severe pain and dysfunction. It has a serious impact on the quality of lives of patients. Since mechanism underlying the pathogenesis of TMJOA is not fully understood, the development of effective tools for early diagnosis and disease-modifying therapies has been hindered. Animal models play a key role in understanding the pathological process of diseases and evaluating new therapeutic interventions. Although some similarities in disease processes between animals and humans are known, no one animal model is sufficient for studying all characteristics of TMJOA, as each model has different translatability to human clinical conditions. For the past 4 decades, TMJOA animal models have been studied by numerous researchers and can be broadly divided into induced, naturally occurring, and genetically modified models. The induced models can be divided into invasive models (intra-articular injection and surgical induction) or non-invasive models (mechanical loading, high-fat diet, and sleep deprivation). Different types of animal models simulate different pathological expressions of TMJOA and have their unique characteristics. Currently, mice, rats, and rabbits are commonly used in the study of TMJOA. This review sought to provide a general description of current experimental models of TMJOA and assist researchers in selecting the most appropriate models for different kinds of research.

Animal Models of Temporomandibular Disorder

Temporomandibular disorders (TMD) are a group of diseases in the oral and maxillofacial region that can manifest as acute or chronic persistent pain, affecting millions of people worldwide. Although hundreds of studies have explored mechanisms and treatments underlying TMD, multiple pathogenic factors and diverse clinical manifestations make it still poorly managed. Appropriate animal models are helpful to study the pathogenesis of TMD and explore effective treatment measures. At present, due to the high cost of obtaining large animals, rodents and rabbits are often used to prepare TMD animal models. Over the past decade, various animal models have been intensively developed to understand neurobiological and molecular mechanisms of TMD, and seek effective treatments. Although these models cannot carry out all clinical features, they are valuable in revealing the mechanisms of TMD and creating curative access. Currently, there are multitudinous animal models of TMD research. They can be constructed in different means and summarized into four ways according to the various causes and symptoms, including chemical induction (intra-articular injection of ovalbumin, collagenase, formalin, vascular endothelial growth factor, intramuscular injection of complete Freund’s adjuvant, etc.), mechanical stress stimulation (passive mouth opening, change of chewing load), surgical operation (partial disc resection, joint disc perforation) and psychological stress induction. Here, we summarize and discuss different approaches of animal models for determining neurophysiological and mechanical mechanisms of TMD and assess their advantages and limitations, respectively.

Effects of low and high molecular weight hyaluronic acid on the osteoarthritic temporomandibular joint in rabbit

OBJECTIVE

To compare the effect between intra-articular infiltration of low molecular weight (LMW-HA) and high molecular weight hyaluronic acid (HMW-HA) on the histopathological characteristics of the cartilage and disc of the temporomandibular joint (TMJ) osteoarthritis (OA) induced in rabbits.

MATERIAL AND METHODS

An experimental study was conducted on 38 rabbit TMJs. The effect of different hyaluronic acids was compared at 30 and 135 days. Histopathological analysis was performed. Cartilage damage was assessed with the OARSI scale.

RESULTS

The severity of the induced OA according to OARSI was 3.4 degrees in the mandibular condyle (MC) and 3.2 in the mandibular fossa (MF); the articular disc (AD) presented disorganization of the collagen fibers, with randomly arranged hypertrophic chondrocytes. At 30 days, untreated TMJs worsened. TMJ treated with LMW-HA reduced its severity to 1.5 degrees in MC and 1.6 in MF, the AD presented histological aspects within normal limits. TMJ treated with HMW-HA presented 2.4 degrees in MC and 2.2 in MF, the AD maintained characteristics similar to the group with OA. At 135 days, all groups worsened.

CONCLUSION

Exogenous HA is effective in the management of TMJ-OA induced in rabbits, showing cartilage and articular disc repair at 30 days. The LMW-HA group had better effects on joint tissue than HMW-HA 30 days after treatment. However, at 135 days, both groups presented regression of joint tissue repair.

CLINICAL RELEVANCE

HA is effective in the anti-arthritic treatment of TMJ-OA induced in rabbits; LMW-HA shows better results in cartilage and articular disc repair than HMW-HA.

Repeated Live Imaging in the Temporomandibular Joint of an Anterior Crossbite Mouse Model Using a 7T Magnetic Resonance Device

BACKGROUND/AIM

Few studies have performed magnetic resonance (MR) imaging on live animals. The aim of this study was to perform 7T MR microimaging of the temporomandibular joint (TMJ) multiple times in the same living mice with malocclusion, and to compare between MR imaging and histopathological findings.

MATERIALS AND METHODS

Mice were examined by MR imaging at 3-4, 6 and 12 weeks following the attachment of a metal tube on the left mandibular incisor. Histopathological examination was done at 3, 6 and 12 weeks.

RESULTS

The detailed structure of the TMJ was evident from MR microimaging. The histopathological examination showed some changes in the cartilage, but no changes in the bone structure of these mice.

CONCLUSION

We successfully performed multiple 7T MR imaging in living mice. Even if the TMJ showed no obvious changes on MR images, minute changes may be present in the cartilage.

Reduction of osteoarthritis severity in the temporomandibular joint of rabbits treated with chondroitin sulfate and glucosamine

Osteoarthritis is a degenerative disease that causes substantial changes in joint tissues, such as cartilage degeneration and subchondral bone sclerosis. Chondroitin sulfate and glucosamine are commonly used products for the symptomatic treatment of osteoarthritis. The aim of the present study was to investigate the effects of these products when used as structure-modifying drugs on the progression of osteoarthritis in the rabbit temporomandibular joint. Thirty-six New Zealand rabbits were divided into 3 groups (n = 12/group): control (no disease); osteoarthritis (disease induction); and treatment (disease induction and administration of chondroitin sulfate and glucosamine). Osteoarthritis was induced by intra-articular injection of monosodium iodoacetate. Animals were killed at 30 and 90 days after initiation of therapy. The treatment was effective in reducing disease severity, with late effects and changes in the concentration of glycosaminoglycans in the articular disc. The results indicate that chondroitin sulfate and glucosamine may have a structure-modifying effect on the tissues of rabbit temporomandibular joints altered by osteoarthritis.

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.

Development of an ultrathin sheet plastination technique in rat humeral joints with osteoarthritis induced by monosodium iodoacetate for neovascularization study

Injection with monosodium iodoacetate (MIA) is widely used to produce osteoarthritis (OA). Ultrathin sheet plastination has been used to study the morphology of structures, with strong application in anatomical education and research. Our aim was to carry out, for the first time, ultrathin sheet plastination of rat humeral joints to observe the neovascularization provoked by OA. We injected 0.1 mL of MIA into the left humeral joints of ten Sprague-Dawley rats. The right shoulders of the same rats were used as control. Sixteen weeks after the injection, the animals were euthanized and were given an immediate red epoxy resin injection through the thoracic aorta. The samples were fixed in 10% formalin, prior to the plastination process, without decalcification. Samples were dehydrated with acetone (100%) at - 25 °C, for 10 days. Later, for degreasing, samples were immersed in methylene chloride at room temperature during 1 week. Forced impregnation was performed inside a stove within a vacuum chamber. The plastinated blocks obtained were cut with a slow velocity diamond blade saw. Slices were placed in curing chambers to achieve curing and final tissue transparentation. 230 μm thickness slices were obtained. The slices were analyzed under magnifying glass and microscope, achieving visualization of OA neovascularization. The cartilage affected by OA loses its ability to remain avascular, and blood vessels invade it from the subchondral bone to the calcified and uncalcified cartilage. Ultra-thin sheet plastination is useful to observe articular cartilage neovascularization, caused by OA induced with MIA in humeral rat joint.

Condylotomy to Reverse Temporomandibular Joint Osteoarthritis in Rabbits

PURPOSE

Osteoarthritis (OA) of the temporomandibular joint (TMJ) is characterized by local tissue degeneration and pain. Treatments have been aimed at reducing symptoms, and only some can interfere with the progression of pathophysiologic changes caused by OA. Condylotomy is an alternative treatment for patients with OA refractory to conventional treatment. The aim of the present animal study was to investigate the influence of condylotomy on TMJ OA in New Zealand rabbits.

MATERIALS AND METHODS

The 36 rabbits were divided into 3 groups: the osteoarthritis group (OG; induced OA), treatment group (TG; induced OA plus condylotomy), and control group (CG; neither OA nor surgery). OA was induced using intra-articular monosodium iodoacetate injection for 40 days. The rabbits in the TG underwent condylotomy and were killed 20, 40, and 60 days after treatment. The rabbits in the CG and OG were killed at the same points.

RESULTS

The articular joint condition was better in the TG 60 days after surgery (P = .032). A direct comparison revealed regression of TMJ OA over time among the treated rabbits (P = .008). Surgical treatment promoted mandibular condylar remodeling in the TG, reversing the tissue degeneration caused by OA.

CONCLUSIONS

Our findings suggest that condylotomy could be an option for the treatment of OA and prevent damage to TMJ structures. This could be of particular importance for patients without satisfactory responses to more conservative treatment.

Remaining Hurdles for Tissue-Engineering the Temporomandibular Joint Disc

The temporomandibular joint (TMJ) disc, a fibrocartilaginous structure between the mandible and temporal bone, is implicated in temporomandibular disorders (TMDs). TMDs symptomatically affect approximately 25% of the population, of which 70% have internal derangement of the disc. Treatments lack efficiency, motivating novel therapies, including tissue-engineering toward TMJ disc regeneration. Recent developments in scaffold-based or scaffold-free approaches, cell sources, and biochemical and mechanical stimulation have resulted in constructs exhibiting native tissue mechanics. Safety and efficacy of tissue-engineered implants have shown promising results in orthotopic animal studies. However, many hurdles need to be overcome in tissue-engineering approaches, and clinical and regulatory pathways. Future studies present an opportunity for clinicians and researchers to work together toward safe and effective clinical trials.

Effect of platelet-rich plasma on temporomandibular joint cartilage wound healing: Experimental study in rabbits

PURPOSE

The aim of the study is to evaluate the effect of platelet-rich plasma (PRP) injection on temporomandibular joint (TMJ) cartilage and subchondral bone healing.

MATERIALS AND METHODS

Sixteen New Zealand rabbits were divided into two groups, including single PRP and multiple PRP injection groups. Sodium mono-iodoacetate (MIA) was injected bilaterally into the TMJ of all rabbits to create osteoarthritis (OA). PRP was injected once into the right TMJ in the single PRP group and was injected three times (once a week) into the right TMJ in the multiple injection group 4 weeks after injection of MIA. At the time of each PRP injection, isotonic NaCl solution was injected into the left TMJ in the control groups. All animals were sacrificed 30 days after the first PRP injection.

RESULTS

As a result of the histological evaluation, there was no statistically significant difference in cartilage and subchondral bone regeneration between the groups (p > 0.05).

CONCLUSIONS

Although there was no statistically significant difference between PRP and control groups, it was seen that improvement were better in PRP groups. According to the Results of our study, it seems that different methods should be tried to investigate the efficacy of PRP on the TMJ healing.

Short term histopathological effects of GaAlAs laser on experimentally induced TMJ osteoarthritis in rabbits

The aim of this study was to evaluate the biostimulation (BS) effect of the gallium-aluminum-arsenide (GaAlAs) diode laser by histopathology with an experimental osteoarthritis (OA) model in the temporomandibular joints (TMJ) of rabbits, in the early period. GaAlAs diode laser is used for pain reduction in TMJ disorders. Twenty-four adult male New Zealand white rabbits were randomly divided into three equal groups: Control Group (CG), Study Group 1 (SG-1), and Study Group 2 (SG-2). Mono-iodoacetate (MIA) was administered to the right TMJs of all rabbits. The rabbits did not undergo any treatment for four weeks to allow the development of osteoarthritis. In SG-1, laser BS was applied to the rabbits at 940 nm, 5 W, and 15 J/cm2 in continuous wave mode at 48-hour intervals for 14 sessions; and in SG-2, laser BS was applied with the same parameters at 24-hour intervals for 28 sessions. Laser BS was not applied to the rabbits in CG. All rabbits were sacrificed simultaneously. The TMJ cartilage, osteochondral junction, chondrocyte appearance, and subchondral ossification were evaluated histopathologically. There was no statistically significant difference between the groups in terms of cartilage, osteochondral junction, chondrocyte appearance, and subchondral ossification values (p > 0.05). The laser BS protocol used in the study had no positive histopathological effects on TMJ OA in the early period.

Effect of hyaluronic acid on the regulation of inflammatory mediators in osteoarthritis of the temporomandibular joint: a systematic review

Osteoarthritis is one of the most frequent pathologies affecting the temporomandibular joint (TMJ). There is evidence that the use of intra-articular hyaluronic acid (HA) for the treatment of this disorder achieves positive effects through a reduction in inflammatory mediators. A systematic review of the available evidence regarding the regulation of inflammatory mediators when applying HA in osteoarthritis of the TMJ in humans was performed. The Web of Science, Embase, ScienceDirect, MEDLINE, Scopus, EBSCOhost, and LILACS databases, SciELO library, and search engine Trip Database were searched systematically. Two thousand eight hundred and sixty-three related articles were found, of which only two met the selection criteria (both were clinical trials and evidence level 2b for treatment studies). These two articles represented a population of 87 patients. Both articles reported that the application of HA had a positive effect on the regulation of inflammatory mediators; the mediators studied were those of the plasminogen activator system and levels of nitric oxide. The limited evidence available suggests that the application of HA regulates various inflammatory mediators in osteoarthritic processes in the TMJ. Nevertheless, further evidence in this regard is required, through the study of specific pathologies of the TMJ, complementing the assessment of clinical parameters with molecular studies, and generating good quality clinical studies with larger sample sizes.

Rabbit model for osteoarthrosis of the temporomandibular joint as a basis for assessment of outcomes after intervention

Osteoarthritis can be induced in the temporomandibular joint (TMJ) by primary or secondary trauma, or overloading of the joint. We have therefore systematically evaluated the histological progression of experimental osteoarthritis induced by a high concentration of monosodium iodoacetate into the rabbit TMJ. These findings may contribute to the establishment of a protocol to investigate the benefits of treatment of osteoarthritis of the TMJ. We used 21 male New Zealand rabbits; the 15 in the test group were given an intra-articular injection of monosodium iodoacetate 10mg/ml into the right TMJ and were killed after 60 (n=5), 80 (n=5), and 100 days (n=5). The six in the control group were given an injection of saline into the right TMJ. The assessment system for osteoarthritis based on six grades was used for the histological analysis of severity. The model was effective in producing histological changes in the cartilage consistent with those found in osteoarthritis at all time points. The within-group analysis indicated that the disease did not progress after 60 days. The successful induction of osteoarthritis in this way, its stabilisation after 60 days, and the appropriate size of the animal suggest that this experimental model is ideal for future studies of the effectiveness of treatment in osteoarthritis of the TMJ.

AMD3100 Attenuates Matrix Metalloprotease-3 and -9 Expressions and Prevents Cartilage Degradation in a Monosodium Iodo-Acetate-Induced Rat Model of Temporomandibular Osteoarthritis

PURPOSE

Temporomandibular joint osteoarthritis (TMJOA) is an important subtype of temporomandibular disorder. This study investigated the inflammatory role of the stromal cell-derived factor-1 (SDF-1) and C-X-C chemokine receptor-4 (CXCR4) axis and the probable signaling pathway involved in matrix metalloprotease (MMP)-3 and MMP-9 productions stimulated by the SDF-1-CXCR4 axis in an experimental rat model of TMJOA.

MATERIALS AND METHODS

Rats were randomly divided into a control group, a pathologic model group, and an AMD3100 group. Effects of the bicyclam derivative AMD3100 (the specific antagonist of SDF-1-CXCR4 axis) were studied in TMJOA experimentally induced by monosodium iodo-acetate. Productions of SDF-1 and CXCR4 were compared in the normal and pathologic model groups, and cartilage changes and expressions of MMP-3, MMP-9, and phosphorylated extracellular signal-regulated kinase (p-ERK) were compared in the control, pathologic model, and AMD3100 groups.

RESULTS

Expressions of SDF-1 and CXCR4 in the pathologic model group were increased compared with the control group (P < .05). Releases of MMP-3, MMP-9, and p-ERK and cartilage changes were downregulated in the AMD3100 group compared with the pathologic model group (P < .05), and these changes occurred in a dose-dependent manner with AMD3100 concentrations. Moreover, there were strong predictive relations between the expression of p-ERK with MMP-3 (r(2) = 0.419; P < .001) and with MMP-9 (r(2) = 0.542; P < .001).

CONCLUSIONS

The SDF-1-CXCR4 signaling pathway plays a proinflammatory role in experimental TMJOA, the bicyclam derivative AMD3100 can alleviate the severity of experimental TMJOA, and there might be a potential relation between the SDF-1-CXCR4 axis and the ERK signaling pathway.

Synovial TRPV1 is upregulated by 17-β-estradiol and involved in allodynia of inflamed temporomandibular joints in female rats

Women with reproductive capability are more likely to suffer from temporomandibular disorders (TMD), with orofacial pain as the most common complaint. In the past, we focused on the role of estradiol in TMD pain through the nervous system. In this study, we explored estradiol's influence on synoviocyte gene expressions involved in the allodynia of the inflamed TMJ. The influence of 17-β-estradiol on NGF and TRPV1 expression in TMJ synovium was determined in vivo and in vitro and analyzed by Western blot and real-time PCR. Complete Freund's adjuvant (CFA) injection into the TMJ was used to induce TMJ arthritis. Capsazepine served as a TRPV1 antagonist. Head withdrawal threshold was examined using a von Frey Anesthesiometer. We observed that estradiol upregulated the expressions of TRPV1 and NGF in a dose-dependent manner. In the primary cultured synoviocytes, TRPV1 was upregulated by lipopolysaccharide (LPS), estradiol, and NGF, while NGF antibodies fully blocked LPS and estradiol-induced upregulation of TRPV1. Activation of TRPV1 in the primary synoviocytes with capsaicin, a TRPV1 agonist, dose-dependently enhanced COX-2 transcription. Moreover, intra-TMJ injection of TRPV1 antagonist, capsazepine, significantly attenuated allodynia of the inflamed TMJ induced by intra-TMJ injection of CFA in female rats. This article presents a possible local mechanism for estradiol that may be involved in TMJ inflammation or pain in the synovial membrane through the pain-related gene TRPV1. This finding could potentially help clinicians understand the sexual dimorphism of TMD pain.

Progression of cartilage degradation, bone resorption and pain in rat temporomandibular joint osteoarthritis induced by injection of iodoacetate

Background

Osteoarthritis (OA) is an important subtype of temporomandibular disorders. A simple and reproducible animal model that mimics the histopathologic changes, both in the cartilage and subchondral bone, and clinical symptoms of temporomandibular joint osteoarthritis (TMJOA) would help in our understanding of its process and underlying mechanism.

Objective

To explore whether injection of monosodium iodoacetate (MIA) into the upper compartment of rat TMJ could induce OA-like lesions.

Methods

Female rats were injected with varied doses of MIA into the upper compartment and observed for up to 12 weeks. Histologic, radiographic, behavioral, and molecular changes in the TMJ were evaluated by light and electron microscopy, MicroCT scanning, head withdrawal threshold test, real-time PCR, immunohistochemistry, and TUNEL assay.

Results

The intermediate zone of the disc loosened by 1 day post-MIA injection and thinned thereafter. Injection of an MIA dose of 0.5 mg or higher induced typical OA-like lesions in the TMJ within 4 weeks. Condylar destruction presented in a time-dependent manner, including chondrocyte apoptosis in the early stages, subsequent cartilage matrix disorganization and subchondral bone erosion, fibrosis, subchondral bone sclerosis, and osteophyte formation in the late stages. Nociceptive responses increased in the early stages, corresponding to severe synovitis. Furthermore, chondrocyte apoptosis and an imbalance between anabolism and catabolism of cartilage and subchondral bone might account for the condylar destruction.

Conclusions

Multi-level data demonstrated a reliable and convenient rat model of TMJOA could be induced by MIA injection into the upper compartment. The model might facilitate TMJOA related researches.

Sustained inflammation induces degeneration of the temporomandibular joint

The temporomandibular joint (TMJ) undergoes degenerative changes among patients who suffer from arthritis, and yet the pathogenesis of TMJ osteoarthritis and rheumatoid arthritis is poorly understood. We hypothesized that sustained inflammation in the TMJ induces structural abnormalities, and accordingly characterized the disc and synovium in a novel model with double injections of complete Freund's adjuvant (CFA), using behavioral, morphological, cellular, and molecular assessments. Thirty-five days following double CFA injections in seven-week-old female Sprague-Dawley rats, the disc in the CFA-induced inflammation group demonstrated multiple degenerative changes, including marked thickening, opacity, and deformation. The discs in the CFA group further showed significantly greater wet and net weights, and elevated collagen, aggrecan, and total glycosaminoglycan contents. The synovium in the CFA-induced inflammation group showed marked infiltration of mononucleated cells and accumulated sub-synovial adipose tissue. Both the disc and synovium had significantly higher iNOS and IL-1β mRNA expression than controls (saline injections). These findings are consistent with our hypothesis that sustained TMJ inflammation, even within the presently observed 35 days, may be a predisposing factor for structural abnormalities. Insight into TMJ inflammation and degeneration is anticipated to improve our understanding of the pathogenesis of TMJ arthritis and help design clinically relevant strategies for tissue engineering.

The effects of high molecular weight hyaluronic acid (Hylan G-F 20) on experimentally induced temporomandibular joint osteoartrosis: part II

The aim of this study was to determine the efficacy of Hylan G-F 20 on experimentally induced osteoarthritic changes in rabbit temporomandibular joint (TMJ). A 3mg/ml concentration of sodium mono iodoacetate (MIA) had been injected into both joints of 24 rabbits to create osteoartrosis. The study group was injected with Hylan G-F 20 in one joint and saline in the contralateral joint as a control (once a week for 3 weeks). Histological changes in articular cartilage, osteochondral junction, chondrocyte appearance and subchondral bone were determined at 4, 6, and 8 weeks. Regarding cartilage, there was a statistically significant difference between the two groups at 4 weeks. Degenerative bony changes to subchondral bone were significantly higher in the controls. No statistical difference was found in the study group at 6 weeks. A positive correlation was found between osteochondral junction and subchondral bone in the study group at 8 weeks. The changes in chondrocyte appearance were significantly decreased in the study group at all follow-up times. Intra-articular injection of Hylan G-F 20 decreased cartilage changes in early stage TMJ osteoartrosis and clustering of chondrocytes showed the chondroprotective effects of Hylan G-F 20 caused by hypertrophic responses.

Sodium iodoacetate induced osteoarthrosis model in rabbit temporomandibular joint: CT and histological study (part I)

Studies to elucidate the pathophysiology of osteoarthrosis have been hampered by the lack of a rapid, reproducible animal model that mimics the histopathology and symptoms associated with the disease. The aim of this study is to evaluate the radiological, histological and histomorphometrical findings of four different concentrations of sodium iodoacetate (MIA) to create osteoarthrosis by using an arthrocentesis technique on rabbit temporomandibular joint (TMJ). 12 New Zealand white male rabbits received an injection of MIA (50 μl dose of 1.5, 2, 2.5, 3mg/ml concentrations) to a single joint of each group by arthrocentesis. Computed tomography (CT) images were obtained pre- and post-injections at 2, 4 and 6 weeks. Early osteoarthritic changes in the rabbit TMJ were found histologically at 4 weeks and with a 3mg/ml concentration of MIA. The mean subchondral bone volume depended on the concentration of MIA and was 62±2.6%, 63±4.1%, 42±3.6% and 38±3.8%, respectively. A minor abnormality was found on CT in six joints at the 4-week follow up. MIA injection and arthrocentesis offer a rapid and minimally invasive method of reproducing histologically osteoarthrotic lesions in the rabbit TMJ.

Chondrogenic effect of the perichondrium graft on the internal derangement and osteoarthritis of the temporomandibular joint of the rabbit

Internal derangement of the temporomandibular joint is usually defined as the disruption of the condyle and disc relationship. In addition to this description the other elements of the joint including the cartilage surface, synovial fluid, the ligaments and the bony surface itself demonstrate varying degrees of pathology in concordance with the stage of the internal derangement, as well. This study is designed to create an osteoarthritic model in the rabbit temporomandibular joint. A 2×2mm defect was performed on the cartilage surface of the both condyles of each animal (n=30). The osteoarthritic changes were demonstrated by computerised tomography sections. The right joints of the animals constituted the control group and the left, the study group. At the time of the defect generation, a perichondrium graft from the animal's ear was implanted onto the defect in the study group. The control group was left to heal secondarily. The joints of three randomized groups of 10 animals for each were inspected at the 4th, 6th, and 8th weeks. Cartilage regeneration and regression of the osteoarthritic changes were demonstrated in the study group both in the 6th and 8th week groups. However, the control group showed less cartilage regeneration and progression of the osteoarthritic changes in all weeks, with progression with time. The perichondrium graft has demonstrated chondrogenic effect on the condyle and this in turn changed the progression to internal derangement.

Analysis of microarchitectural changes in a mouse temporomandibular joint osteoarthritis model

OBJECTIVE

Little is known about the natural progression of the disease process of temporomandibular joint (TMJ) osteoarthritis (OA), which affects approximately 1% of the US population. The goal of this study was to examine the early microarchitectural and molecular changes in the condylar cartilage and subchondral bone in biglycan/fibromodulin (Bgn/Fmod) double-deficient mice, which develop TMJ-OA at 6 months.

METHODS

TMJs from 3-month-old (n=44) and 9-month-old (n=52) wild-type (WT n=46) and Bgn/Fmod (n=50) double-deficient mice were evaluated. Micro-CT analysis of the subchondral bone (n=24), transmission electron microscopy for condylar cartilage fibril diameters (n=26), and real-time PCR analysis for gene expression for bone and cartilage maturation markers (n=45) was performed.

RESULTS

A statistically significant increase in collagen fibril diameter of the condylar cartilage and a decrease in expression of Parathyroid related protein in the mandibular condylar head were observed in the 3-month Bgn/Fmod double-deficient mice compared to WT controls. The 9-month Bgn/Fmod double-deficient mouse demonstrated an increase in bone volume and total volume in subchondral bone, and an increase in the expression of Collagen Type X and Aggrecan in the mandibular condylar head compared to the WT controls.

CONCLUSION

We found that changes in the microarchitecture of the condylar cartilage preceded changes in the subchondral bone during OA in the TMJ in Bgn/Fmod double-deficient mice.