Animal Models of Temporomandibular Joint Osteoarthritis: Classification and Selection

Exploring the therapeutic potential of urine-derived stem cell exosomes in temporomandibular joint osteoarthritis

Temporomandibular joint osteoarthritis (TMJOA) is a degenerative ailment that causes slow cartilage degeneration, aberrant bone remodeling, and persistent discomfort, leading to a considerable reduction in the patient's life quality. Current treatment options for TMJOA have limited efficacy. This investigation aimed to explore a potential strategy for halting or reversing the progression of TMJOA through the utilization of exosomes (EXOs) derived from urine-derived stem cells (USCs). The USC-EXOs were obtained through microfiltration and ultrafiltration techniques, followed by their characterization using particle size analysis, electron microscopy, and immunoblotting. Subsequently, an in vivo model of TMJOA induced by mechanical force was established. To assess the changes in the cartilage of TMJOA treated with USC-EXOs, we performed histology analysis using hematoxylin-eosin staining, immunohistochemistry, and histological scoring. Our findings indicate that the utilization of USC-EXOs yields substantial reductions in TMJOA, while concurrently enhancing the structural integrity and smoothness of the compromised condylar cartilage surface. Additionally, USC-EXOs exhibit inhibitory effects on osteoclastogenic activity within the subchondral bone layer of the condylar cartilage, as well as attenuated apoptosis in the rat TMJ in response to mechanical injury. In conclusion, USC-EXOs hold considerable promise as a potential therapeutic intervention for TMJOA.

Loss of β-arrestin2 aggravated condylar cartilage degeneration at the early stage of temporomandibular joint osteoarthritis

OBJECTIVE

Temporomandibular joint osteoarthritis (TMJOA) is a chronic degenerative joint disorder characterized by extracellular matrix degeneration and inflammatory response of condylar cartilage. β-arrestin2 is an important regulator of inflammation response, while its role in TMJOA remains unknown. The objective of this study was to investigate the role of β-arrestin2 in the development of TMJOA at the early stage and the underlying mechanism.

METHODS

A unilateral anterior crossbite (UAC) model was established on eight-week-old wild-type (WT) and β-arrestin2 deficiency mice to simulate the progression of TMJOA. Hematoxylin-eosin (HE) staining and microcomputed tomography (micro-CT) analysis were used for histological and radiographic assessment. Immunohistochemistry was performed to detect the expression of inflammatory and degradative cytokines, as well as autophagy related factors. Terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) assay was carried out to assess chondrocyte apoptosis.

RESULTS

The loss of β-arrestin2 aggravated cartilage degeneration and subchondral bone destruction in the model of TMJOA at the early stage. Furthermore, in UAC groups, the expressions of degradative (Col-X) and inflammatory (TNF-α and IL-1β) factors in condylar cartilage were increased in β-arrestin2 null mice compared with WT mice. Moreover, the loss of β-arrestin2 promoted apoptosis and autophagic process of chondrocytes at the early stage of TMJOA.

CONCLUSION

In conclusion, we demonstrated for the first time that β-arrestin2 plays a protective role in the development of TMJOA at the early stage, probably by inhibiting apoptosis and autophagic process of chondrocytes. Therefore, β-arrestin2 might be a potential therapeutic target for TMJOA, providing a new insight for the treatment of TMJOA at the early stage.

Influence on the temporomandibular joint induced by mandibular malpositioning caused by vertical dimension elevation and occlusal loss in adult rats: An imaging, histological and immunohistochemical study

BACKGROUND

Mandibular malpositioning may result in an abnormal concentration of stresses within the temporomandibular joint (TMJ) in adult rats, which may further lead to a series of pathological changes, such as articular cartilage wear, subchondral bone sclerosis and osteophyte formation. However, the pathological and adaptive changes in condylar cartilage caused by different stress distributions are still controversial.

OBJECTIVE

The aim of this study was to observe the effect of sagittal changes in mandibular position on condylar cartilage by changing the occlusal vertical dimension (OVD) in adult rats.

METHODS

Fifteen-week-old female rats were divided into three groups: control (CON), increased OVD (iOVD) and loss of occlusion (LO) groups. An occlusal plate and tooth extraction were used to establish the animal model. TMJ samples of the experimental and CON groups were observed and investigated by bone morphological, histomorphological and immunohistochemical staining analyses at 3 days, 1 week, 2 weeks, 4 weeks and 8 weeks. Weight curves were plotted.

RESULTS

Micro-computed tomography showed that, compared with the CON group, cartilage destruction followed by repair occurred in both experimental groups, which was similar to the trend observed in haematoxylin-eosin staining. All experimental results for the iOVD group showed an approximately similar time trend. Compared with the iOVD group, the toluidine blue and immunohistochemical staining results in the LO group showed no obvious change trend over time.

CONCLUSION

Compared with occlusal loss, an increase in OVD caused faster and more severe damage to condylar cartilage, and subchondral bone repair occurred later.

Long-term haplodeficency of DSPP causes temporomandibular joint osteoarthritis in mice

BACKGROUND

Extracellular matrix (ECM) protein malfunction or defect may lead to temporomandibular joint osteoarthritis (TMJ OA). Dentin sialophophoprotein (DSPP) is a mandibular condylar cartilage ECM protein, and its deletion impacted cell proliferation and other extracellular matrix alterations of postnatal condylar cartilage. However, it remains unclear if long-term loss of function of DSPP leads to TMJ OA. The study aimed to test the hypothesis that long-term haploinsufficiency of DSPP causes TMJ OA.

MATERIALS AND METHODS

To determine whether Dspp+/- mice exhibit TMJ OA but no severe tooth defects, mandibles of wild-type (WT), Dspp+/-, and Dspp homozygous (Dspp-/-) mice were analyzed by Micro-computed tomography (micro-CT). To characterize the progression and possible mechanisms of osteoarthritic degeneration over time in Dspp+/- mice over time, condyles of Dspp+/- and WT mice were analyzed radiologically, histologically, and immunohistochemically.

RESULTS

Micro-CT and histomorphometric analyses revealed that Dspp+/- and Dspp-/- mice had significantly lower subchondral bone mass, bone volume fraction, bone mineral density, and trabecular thickness compared to WT mice at 12 months. Interestingly, in contrast to Dspp-/- mice which exhibited tooth loss, Dspp+/- mice had minor tooth defects. RNA sequencing data showed that haplodeficency of DSPP affects the biological process of ossification and osteoclast differentiation. Additionally, histological analysis showed that Dspp+/- mice had condylar cartilage fissures, reduced cartilage thickness, decreased articular cell numbers and severe subchondral bone cavities, and with signs that were exaggerated with age. Radiographic data showed an increase in subchondral osteoporosis up to 18 months and osteophyte formation at 21 months. Moreover, Dspp+/- mice showed increased distribution of osteoclasts in the subchondral bone and increased expression of MMP2, IL-6, FN-1, and TLR4 in the mandibular condylar cartilage.

CONCLUSIONS

Dspp+/- mice exhibit TMJ OA in a time-dependent manner, with lesions in the mandibular condyle attributed to hypomineralization of subchondral bone and breakdown of the mandibular condylar cartilage, accompanied by upregulation of inflammatory markers.

Glutathione peroxidase 4 restrains temporomandibular joint osteoarthritis progression by inhibiting ferroptosis

There are few effective therapeutic strategies for temporomandibular joint osteoarthritis (TMJOA) due to the unclear pathology and mechanisms. We aimed to confirm the roles of GPX4 and ferroptosis in TMJOA progression. ELISA assay was hired to evaluate concentrations of ferroptosis-related markers. The qRT-PCR assay was hired to assess gene mRNA level. Western blot assay and immunohistochemistry were hired to verify the protein level. CCK-8 assay was hired to detect cell viability. Human fibroblast-like synoviocytes (FLSs) were cultured to confirm the effects of GPX4 and indicated inhibitors, and further verified the effects of GPX4 and ferroptosis inhibitors in TMJOA model rats. Markers of ferroptosis including 8-hidroxy-2-deoxyguanosine (8-OHdG) and iron were notably increased in TMJOA tissues and primary OA-FLSs. However, the activity of the antioxidant system including the glutathione peroxidase activity, glutathione (GSH) contents, and glutathione/oxidized glutathione (GSH/GSSG) ratio was notably inhibited in TMJOA tissues, and the primary OA-FLSs. Furthermore, the glutathione peroxidase 4 (GPX4) expression was down-regulated in TMJOA tissues and primary OA-FLSs. Animal and cell experiments have shown that ferroptosis inhibitors notably inhibited ferroptosis and promoted HLS survival as well as up-regulated GPX4 expression. Also, GPX4 knockdown promoted ferroptosis and GPX4 overexpression inhibited ferroptosis. GPX4 also positively regulated cell survival which was the opposite with ferroptosis. In conclusion, GPX4 and ferroptosis regulated the progression of TMJOA. Targeting ferroptosis might be an effective therapeutic strategy for TMJOA patients in the clinic.

A comprehensive patient-specific prediction model for temporomandibular joint osteoarthritis progression

Temporomandibular joint osteoarthritis (TMJ OA) is a prevalent degenerative disease characterized by chronic pain and impaired jaw function. The complexity of TMJ OA has hindered the development of prognostic tools, posing a significant challenge in timely, patient-specific management. Addressing this gap, our research employs a comprehensive, multidimensional approach to advance TMJ OA prognostication. We conducted a prospective study with 106 subjects, 74 of whom were followed up after 2 to 3 y of conservative treatment. Central to our methodology is the development of an innovative, open-source predictive modeling framework, the Ensemble via Hierarchical Predictions through Nested cross-validation tool (EHPN). This framework synergistically integrates 18 feature selection, statistical, and machine learning methods to yield an accuracy of 0.87, with an area under the ROC curve of 0.72 and an F1 score of 0.82. Our study, beyond technical advancements, emphasizes the global impact of TMJ OA, recognizing its unique demographic occurrence. We highlight key factors influencing TMJ OA progression. Using SHAP analysis, we identified personalized prognostic predictors: lower values of headache, lower back pain, restless sleep, condyle high gray level-GL-run emphasis, articular fossa GL nonuniformity, and long-run low GL emphasis; and higher values of superior joint space, mouth opening, saliva Vascular-endothelium-growth-factor, Matrix-metalloproteinase-7, serum Epithelial-neutrophil-activating-peptide, and age indicate recovery likelihood. Our multidimensional and multimodal EHPN tool enhances clinicians' decision-making, offering a transformative translational infrastructure. The EHPN model stands as a significant contribution to precision medicine, offering a paradigm shift in the management of temporomandibular disorders and potentially influencing broader applications in personalized healthcare.

Managing Temporomandibular Joint Osteoarthritis by Dental Stem Cell Secretome

The potential therapeutic role of the Dental Pulp Stem Cells Secretome (SECR) in a rat model of experimentally induced Temporomandibular Joint (TMJ) Osteoarthritis (OA) was evaluated. Proteomic profiling of the human SECR under specific oxygen tension (5% O2) and stimulation with Tumor Necrosis Factor-alpha (TNF-α) was performed. SECR and respective cell lysates (CL) samples were collected and subjected to SDS-PAGE, followed by LC-MS/MS analysis. The identified proteins were analyzed with Bioinformatic tools. The anti-inflammatory properties of SECR were assessed via an in vitro murine macrophages model, and were further validated in vivo, in a rat model of chemically-induced TMJ-OA by weekly recording of the head withdrawal threshold, the food intake, and the weight change, and radiographically and histologically at 4- and 8-weeks post-treatment. SECR analysis revealed the presence of 50 proteins that were enriched and/or statistically significantly upregulated compared to CL, while many of those proteins were involved in pathways related to "extracellular matrix organization" and "immune system". SECR application in vitro led to a significant downregulation on the expression of pro-inflammatory genes (MMP-13, MMP-9, MMP-3 and MCP-1), while maintaining an increased expression of IL-10 and IL-6. SECR application in vivo had a significant positive effect on all the clinical parameters, resulting in improved food intake, weight, and pain suppression. Radiographically, SECR application had a significant positive effect on trabecular bone thickness and bone density compared to the saline-treated group. Histological analysis indicated that SECR administration reduced inflammation, enhanced ECM and subchondral bone repair and regeneration, thus alleviating TMJ degeneration.

Allogenic umbilical cord tissue for temporomandibular joint injuries

The temporomandibular joint (TMJ) is crucial for functions of daily living such as mastication and articulation. Common TMJ issues include osteoarthritis, internal derangement, and myofascial pain dysfunction. Conservative methods such as physical therapy and medications are used, with surgical options such as arthroscopy and replacement for severe cases. Emerging regenerative medicine explores non-surgical treatments using human stem cells from umbilical cord derivatives, showing potential for tissue regeneration in TMJ disorders. A systematic search was conducted across PubMed, Embase, Scopus, and Web of Science databases, adhering to PRISMA guidelines, aiming to identify relevant articles published in English until August 2023. The search used specific terms to target in vitro, preclinical, and clinical studies on umbilical cord (UC)-derived tissue and mesenchymal stem cells (MSCs) for treating TMJ disorders. The search was extended to three clinical trial registries for on-going investigations related to UC tissue and MSCs for TMJ disorder management. The studies included in this article report the safety and efficacy profiles of allogenically acquired, umbilical cord-derived tissues and associated mesenchymal stem cells for temporomandibular joint ailments, future adequately powered, randomized controlled trials are warranted to conclusively justify the clinical use of this biologic therapy.

Single-cell RNA sequencing reveals neurovascular-osteochondral network crosstalk during temporomandibular joint osteoarthritis: Pilot study in a human condylar cartilage

Purpose

Temporomandibular joint osteoarthritis (TMJ-OA) is one of the most complex temporomandibular disorders, causing pain and dysfunction. The main pathological feature of TMJ-OA is neurovascular invasion from the subchondral bone to the condylar cartilage. This study aimed to discover the cells and genes that play an important role in the neurovascular-osteochondral network crosstalk in human TMJ-OA.

Materials and methods

Condylar cartilages from patient with TMJ-OA were divided into OA group, and others from patients with benign condylar hyperplasia (CH) were used as control for further single-cell RNA-sequencing (scRNA-seq). Hematoxylin and eosin staining were performed. The cells and genes in the condylar cartilage were identified and analyzed by scRNA-seq.

Results

Histological analysis revealed blood vessel invasion and ossification in the TMJ-OA condylar cartilage. The scRNA-seq identified immune cells, endothelial cells, and chondrocytes in the TMJ-OA condylar cartilage. Macrophages, especially M1-like macrophages, contributed to the inflammation, angiogenesis, and innervation. CD31+ endothelial cells contributed to the bone mineralization. The TMJ-OA cartilage chondrocytes highly expressed genes related to inflammation, angiogenesis, innervation, and ossification. The hub genes contributing to these processes in the TMJ-OA chondrocytes included CTGF, FBN1, FN1, EGFR, and ITGA5.

Conclusion

Our study marks the first time scRNA-seq was used to identify the cells and genes in a human TMJ-OA condylar cartilage, and neurovascular-osteochondral network crosstalk during the human TMJ-OA process was demonstrated. Targeting the crosstalk of these processes may be a potential comprehensive and effective therapeutic strategy for human TMJ-OA.

Atomoxetine and escitalopram migrate the derangement of the temporomandibular joint morphologic and histologic changes in rats exposed to stress-induced depression

PURPOSE

The purpose of this in vivo study was to determine the effects of stress-induced depression and antidepressants on depressive-like behavior, microstructure, and histomorphology of the temporomandibular joint (TMJ) using rats.

METHODS

Experimentally induced depression in rats was created before being treated with two antidepressants; escitalopram (selective-serotonin-reuptake inhibitors) and atomoxetine (norepinephrine-reuptake inhibitors). Micro-computed tomography (Micro-CT) was performed to measure the change in bone volume and bone porosity of the condyle. Further histological evaluation of the condylar cartilage was performed.

RESULTS

Micro-CT scanning revealed a decrease in bone volume in the depression group. The bone porosity percentage significantly increased in both the escitalopram and atomoxetine groups compared with the control group and the depression group. Histopathological analysis showed increased thickness of cartilage layers in the depression group. In the atomoxetine group, there was a significant increase in the pre-hypertrophic and hypertrophic layer thickness and cell count, but a significant decrease in proteoglycans.

CONCLUSION

The present study findings indicated the change in TMJ characteristics, especially on the superficial part of the condylar head in the depression group. Concerning the applicability of the different antidepressants, depression with the treatment of atomoxetine has the most disadvantages due to bone porosity and cartilaginous condyle changes.

A Novel Burn / Synovectomy Mouse Model for Temporomandibular Joint Osteoarthritis

Temporomandibular Disorders (TMDs) is present in 33% of the U.S. population. Currently available animal models do not faithfully simulate the native disease progression of TMJ OA. The initiation of TMJ OA requires both local trauma and systemic inflammation. In this study, we present a novel mouse model which reproduces these two conditions. This is achieved by a procedure involving both synovectomy (local trauma) and a distant burn injury (systemic inflammation). Its efficacy at inducing TMJ OA was assessed with histomorphology and radiographic evaluation at 1,3, and 9 weeks after the procedure. We found that burn/synovectomy mice demonstrated significantly more degenerative changes in TMJ than uninjured control mice or synovotomy mice. The observed histology in burn/synoectomy mice mimicked native TMJ OA disease progression in a faithful manner. This animal model is invaluable in future research of the mechanism and risk factors of TMJ OA.

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.

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.

Temporomandibular Joint Osteoarthritis: Pathogenic Mechanisms Involving the Cartilage and Subchondral Bone, and Potential Therapeutic Strategies for Joint Regeneration

The temporomandibular joint (TMJ) is a specialized synovial joint that is crucial for the movement and function of the jaw. TMJ osteoarthritis (TMJ OA) is the result of disc dislocation, trauma, functional overburden, and developmental anomalies. TMJ OA affects all joint structures, including the articular cartilage, synovium, subchondral bone, capsule, ligaments, periarticular muscles, and sensory nerves that innervate the tissues. The present review aimed to illustrate the main pathomechanisms involving cartilage and bone changes in TMJ OA and some therapeutic options that have shown potential restorative properties regarding these joint structures in vivo. Chondrocyte loss, extracellular matrix (ECM) degradation, and subchondral bone remodeling are important factors in TMJ OA. The subchondral bone actively participates in TMJ OA through an abnormal bone remodeling initially characterized by a loss of bone mass, followed by reparative mechanisms that lead to stiffness and thickening of the condylar osteochondral interface. In recent years, such therapies as intraarticular platelet-rich plasma (PRP), hyaluronic acid (HA), and mesenchymal stem cell-based treatment (MSCs) have shown promising results with respect to the regeneration of joint structures or the protection against further damage in TMJ OA. Nevertheless, PRP and MSCs are more frequently associated with cartilage and/or bone repair than HA. According to recent findings, the latter could enhance the restorative potential of other therapies (PRP, MSCs) when used in combination, rather than repair TMJ structures by itself. TMJ OA is a complex disease in which degenerative changes in the cartilage and bone develop through intricate mechanisms. The regenerative potential of such therapies as PRP, MSCs, and HA regarding the cartilage and subchondral bone (alone or in various combinations) in TMJ OA remains a matter of further research, with studies sometimes obtaining discrepant results.

miR-132-3p participates in the pathological mechanism of temporomandibular joint osteoarthritis by targeting PTEN

OBJECTIVE

This study aimed to investigate the role of miR-132-3p in the progression of temporomandibular joint osteoarthritis (TMJOA) and its potential pathological mechanism.

DESIGN

A TMJOA model was established using six rats via the unilateral anterior crossbite method. The differential expression of miR-132-3p in the TMJOA (n = 6) and control groups (n = 6) was detected via miRNA sequencing and verified via PCR. The chondrocytes in the condylar cartilage of the temporomandibular joint were cultured and stimulated with IL-1β to simulate TMJOA in vitro. The changes in the proliferation, apoptosis, inflammation and extracellular matrix of these chondrocytes were detected after the upregulation of miR-132-3p expression. The targeted relationship of miR-132-3p and PTEN in TMJOA was verified, and rescue experiments were conducted via co-upregulation of the expression of both miR-132-3p and PTEN.

RESULTS

Compared with that in the control group, miR-132-3p expression was lower in the cartilage tissues of TMJOA rats and IL-1β-induced TMJ chondrocytes. After upregulating the expression of miR-132-3p, the cell proliferation activity and expression levels of aggrecan and type II collagen of IL-1β-induced TMJ chondrocytes were increased, and the apoptosis rate and levels of inflammatory factors were decreased. miR-132-3p can regulate PTEN expression in a targeted manner, and upregulating PTEN expression could reverse the influences of the upregulation of miR-132-3p expression on TMJOA cells.

CONCLUSION

miR-132-3p is less expressed in TMJOA, and it regulates the proliferation, extracellular matrix, and inflammatory response of TMJOA chondrocytes and participates in TMJOA progression by targeting PTEN.