An extra-erythrocyte role of haemoglobin body in chondrocyte hypoxia adaption.

Although haemoglobin is a known carrier of oxygen in erythrocytes that functions to transport oxygen over a long range, its physiological roles outside erythrocytes are largely elusive1,2. Here we found that chondrocytes produced massive amounts of haemoglobin to form eosin-positive bodies in their cytoplasm. The haemoglobin body (Hedy) is a membraneless condensate characterized by phase separation. Production of haemoglobin in chondrocytes is controlled by hypoxia and is dependent on KLF1 rather than the HIF1/2α pathway. Deletion of haemoglobin in chondrocytes leads to Hedy loss along with severe hypoxia, enhanced glycolysis and extensive cell death in the centre of cartilaginous tissue, which is attributed to the loss of the Hedy-controlled oxygen supply under hypoxic conditions. These results demonstrate an extra-erythrocyte role of haemoglobin in chondrocytes, and uncover a heretofore unrecognized mechanism in which chondrocytes survive a hypoxic environment through Hedy.

miR-708-5p deficiency involves the degeneration of mandibular condylar chondrocytes via the TLR4/NF-κB pathway.

OBJECTIVE: Ageing and aberrant biomechanical stimulation are two major risk factors for osteoarthritis (OA). One of the main characteristics of aged cartilage is cellular senescence. One of the main characteristics of osteoarthritic joints is cartilage degeneration. The cells in the temporomandibular joint (TMJ) cartilage are zonally arranged. The deep zone cells are differentiated from the superficial zone cells (SZCs). The purpose of the present study was to investigate whether degenerative shear stress (SS) stimulates the senescence programme in TMJ SZCs, and to determine which miRNA is involved in this process. METHOD: SZCs were isolated from the TMJ condyles of 3-week-old rats and treated with continuous passaging or SS. RNA sequencing was conducted to identify miRNA(s) that overlap with those involved in the replication senescence process and the SS-induced degeneration programme. Unilateral anterior crossbite (UAC), which is TMJ-OA inducible, was applied to 2-month-old and 12-month-old mice for 3 weeks. The effect of TMJ local injection of agomiR-708-5p was evaluated histologically. RESULTS: Both replication and SS treatment induced SZC senescence. miR-708-5p was identified. Knocking down miR-708-5p in SS-treated SZCs led to more severe senescence by alleviating the inhibitory impact of miR-708-5p on the TLR4/NF-κB pathway. miR-708-5p expression in mouse TMJ cartilage decreased with age. UAC induced more severe osteoarthritic cartilage lesions in 12-month-old mice than in 2-month-old mice. Injection of agomiR-708-5p suppressed UAC-induced osteoarthritic cartilage lesions. CONCLUSIONS: Age-related miR-708-5p deficiency is involved in the mechanically stimulated OA process. Intra-articular administration of agomiR-708-5p is a promising new strategy for OA treatment.

CaSR modulates proliferation of the superficial zone cells in temporomandibular joint cartilage via the PTHrP nuclear localization sequence.

The superficial zone cells in mandibular condylar cartilage are proliferative. The present purpose was to delineate the relation of calcium-sensing receptor (CaSR) and parathyroid hormone-related peptide nuclear localization sequence (PTHrP87-139 ), and their role in the proliferation behaviors of the superficial zone cells. A gain- and loss-of-function strategy were used in an in vitro fluid flow shear stress (FFSS) model and an in vivo bilateral elevation bite model which showed mandibular condylar cartilage thickening. CaSR and PTHrP87-139 were modulated through treating the isolated superficial zone cells with activator/SiRNA and via deleting CaSR or parathyroid hormone-related peptide (PTHrP) gene in mice with the promoter gene of proteoglycan 4 (Prg4-CreERT2 ) in the tamoxifen-inducible pattern with or without additional injection of Cinacalcet, the CaSR agonist, or PTHrP87-139 peptide. FFSS stimulated CaSR and PTHrP expression, and accelerated proliferation of the Prg4-expressing superficial zone cells, in which process CaSR acted as an up-streamer of PTHrP. Proteoglycan 4 specific knockout of CaSR or PTHrP reduced the cartilage thickness, suppressed the proliferation and early differentiation of the superficial zone cells, and inhibited cartilage thickening and matrix production promoted by bilateral elevation bite. Injections of CaSR agonist Cinacalcet could not improve the phenotype caused by PTHrP mutation. Injections of PTHrP87-139 peptide rescued the cartilage from knockout of CaSR gene. CaSR modulates proliferation of the superficial zone cells in mandibular condylar cartilage through activation of PTHrP nuclear localization sequence. Our data support the therapeutic target of CaSR in promoting PTHrP production in superficial zone cartilage.

Zonal interdependence in the temporomandibular joint cartilage.

The temporomandibular joint (TMJ) cartilage is biomechanical sensitive. Cells in TMJ cartilage are zonally arranged, earlier differentiated in the super zone and late differentiated in the deep zone. The purpose was to detect the zonal interdependence in TMJ cartilage under dental biomechanical stimulations. Here, we obtained the Sox9CreER ; Rosa26tdTomato and Col10CreER ; Rosa26tdTomato mice to label super zone Sox9-expressing (Sox9+ ) or deep zone Col10-expressing (Col10+ ) cells by tdTomato (TdT), and Sox9CreER ; Rosa26DTA and Col10CreER ; Rosa26DTA mice to ablate Sox9+ or Col10+ cells selectively. These mice were subjected to unilateral anterior crossbite (UAC) or bilateral anterior elevation (BAE) dental stimulation, which promoted terminal differentiation or proliferation of TMJ chondrocytes, respectively. In both UAC and BAE models, the Sox9-TdT+ cells performed as proliferation and mature differentiation, showing as expressing Ki67 and Col-X, respectively; while the Col10-TdT+ cells performed as terminal differentiation, showing as expressing osteocalcin (OCN). In both Sox9+ - and Col10+ -cells ablation groups, there were reductions in cell number, cartilage thickness and matrix amount, subchondral bone loss, and condylar deformation. The UAC-promoted terminal differentiation was enhanced, and the BAE-promoted cellular proliferation was ruined. Impressively, when Col10+ cells were ablated, the UAC-promoted DAP3 expression, an anoikis marker, was further increased, while the BAE-suppressed DAP3 expression was instead greatly increased. These findings demonstrated that the cartilage zones function interdependently. The super zone harbors the cells that undergo differentiation to deep zone cells, the deep zone contains load-bearing matrix which is structural essential for the cells located inside or superficial.

The effect of miR-381 on proliferation and prognosis of breast cancer by altering CCNA2 expression.

BACKGROUND: MiR-381 can regulate the expression of cyclin A2 (CCNA2) to inhibit the proliferation and migration of bladder cancer cells, but whether miR-381 has the same function in breast cancer is not well know. METHODS: The over express or silence miR-381 expressing cell lines were constructed by lentivirus infection to reveal the biological functions of miR-381 in vitro. The expression of miR-381 and CCNA2 in 162 breast cancer patients were detected to further reveal their impact and predictive value on progression-free survival (PFS) and overall survival (OS). RESULTS: After transfection of MDA-MB-231 and MCF-7 cells with miR-381 mimics, the expression of miR-381 was effectively up-regulated and CCNA2 was effectively down-regulated, while the opposite results were observed in tumour cell which transfected with miR-381 inhibitors. After transfection of cell lines with miR-381 mimics, tumour cell activity was significantly reduced, while the opposite results were observed in tumour cell which transfected with miR-381 inhibitors. The area under curves (AUCs) of miRNA-381 and CCNA2 for predicting PFS and OS were 0.711, 0.695, 0.694 and 0.675 respectively. Cox regression analysis showed that miRNA-381 ≥ 1.65 2-ΔΔCt and CCNA ≥ 2.95 2-ΔΔCt were the influence factors of PFS and OS, the hazard ratio (HR) values were 0.553, 2.075, 0.462 and 2.089, respectively. CONCLUSION: miR-381 inhibitors breast cancer cells proliferation and migration by down-regulating the expression of CCNA2, both of them can predict the prognosis of breast cancer.

miR-381 can regulate the expression of cyclin A2 and inhibit the proliferation and migration of bladder cancer cells, but whether miR-381 has the same function in breast cancer is not well know. We analysed the levels of miR-381 and cyclin A2 in breast cancer patients and breast cancer cells to reveal the mechanism of miR-381 affecting the expression of cyclin A2. We found miRNA-381 affects the proliferation and migration of breast cancer cells by down-regulating the expression of cyclin A2. The expression of serum miR-381 and cyclin A2 have important values in predicting the prognosis of breast cancer. Our findings provide mechanistic insights into how miR-381 regulates the proliferation and migration of breast cancer, as well as a new target for clinical treatment. Future research may focus on how to improve patient prognosis by up-regulating expression of miR-381 and down-regulating the expression of cyclin A2.

Reconstructed magnetic resonance image-based effusion volume assessment for temporomandibular joint arthralgia.

BACKGROUND: Joint effusion is often noticed in magnetic resonance image (MRI) and its diagnostic value for arthralgia of the temporomandibular joint (TMJ) remains obscure. OBJECTIVE: To develop a method for quantitatively evaluating the joint effusion revealed in MRI and its diagnostic value for arthralgia of the TMJ. METHODS: Two-hundreds and twenty-eight TMJs, 101 with arthralgia (Group P) and 105 without (Group NP) from 103 patients, and 22 TMJs (Group CON) from 11 asymptomatic volunteers were examined by using MRI. The effusion volume was measured after constructing a three-dimensional structure of the joint effusion revealed in MRI by using the ITK-SNAP software. The diagnostic capabilities of the effusion volume on arthralgia were evaluated with receiver operating characteristic (ROC) curve analysis. RESULTS: Totally 146 joints showed MRI signs of joint effusion, including nine joints from Group CON. However, the medium volume was greater in Group P (66.65 mm3 ), but was much similar in Group CON (18.33 mm3 ) to Group NP (27.12 mm3 ). The effusion volume larger than 38.20 mm3 was validated to discriminate Group P from Group NP. The AUC value was 0.801 (95% CI 0.728 to 0.874), with a sensitivity of 75% and specificity of 78.9%. The median volume of the joint effusion was larger in those with than without bone marrow oedema, osteoarthritis, Type-III disc configurations, disc displacement and higher signal intensity of the retrodiscal tissue (all, p < .05). CONCLUSION: The present method for evaluate joint effusion volume well discriminated painful TMJs from non-pain ones.

Uptight responses between clenching and forearm raising with factors of visual feedback and maintenance effort in healthy young women: An experimental study on factorial design.

BACKGROUND: To achieve different central preset force levels requires various fine-tuning efforts and may elicit different uptight responses. The mandibular lever system has a distinct regularity in the fine-tuning function of the upper limbs. The purpose of the present study was to detect whether the uptight responses elicited from motivating clenching differ from those induced by motivating forearm raising at different force levels. METHODS: Twenty-five healthy females were enrolled in this study. The target was low, medium, and maximum force levels with or without visual feedback and/or maintenance effort. Surface electromyographic (SEMG) activity was recorded from the bilateral anterior temporalis and masseter or left biceps brachii muscle (BicL), and the T-Scan III System synchronously recorded the sensitive force values. The uptight responses and task difficulties were recorded for occlusal and left forearm lifting tasks using a unique visual analogue scale. RESULTS: The highest uptight response value was achieved at a low clenching force level with visual feedback requiring no maintenance effort but at a maximum forearm-raising force level with visual feedback and maintenance effort. The SEMG activities of both jaw-closing muscles and BicL were associated with the central preset force level (P < 0.001). However, the maintenance effort only increased the jaw-closing muscles' SEMG activity at the maximal force level (P < 0.001). CONCLUSIONS: Clenching at the central preset lower force level with visual feedback is prone to elicit a higher degree of uptight response. The constant need for a low-intensity bite can have a negative effect on an individual's mood.

Long-term effect of bilateral anterior elevation of occlusion on the temporomandibular joints.

OBJECTIVE: Incisors tubed prosthesis with bilateral anterior elevation (BAE) relation had been reported to stimulate the proliferative response in the mandibular condylar cartilage of mice, thus the prosthetic occlusion elevation had been proposed to treat cartilage degeneration. Currently, we aimed to detect the long-term effect of BAE on temporomandibular joints (TMJs). MATERIALS AND METHODS: Twelve 6-week-old female mice were assigned to age-matched control and BAE groups (n = 6). Micro-CT images and the macro- and micro-morphology of the mandibular condyles were analyzed at 29 weeks. RESULTS: Compared with the age-matched controls, in BAE group, there were loss of subchondral cortical bone and heavy loss of the subchondral trabecular bone at the superior sites of the TMJ condyles, but hyperostosis at the inferior sites as revealed by micro-CT images and histological slices. In BAE group, cartilage thickness and matrix area were increased with upregulated expression of type II, type X collagen, and Ki67, but the expression of cleaved caspase-3 was downregulated (all, p < 0.05). CONCLUSION: In addition to cartilage thickening, long-term BAE induces loss of the subchondral cortical bone and heavy loss of the underneath subchondral trabecular bone, but hyperostosis further underneath. Using BAE as a treatment remains double-edged.

Effect of dental malocclusion on cerebellar neuron activation via the dorsomedial part of the principal sensory trigeminal nucleus.

Occlusion has been proposed to play a role for body posture and balance, both of which are mediated mainly by the cerebellum. The dorsomedial part of the principal sensory trigeminal nucleus (Vpdm) has direct projection to the cerebellum. The experimental unilateral anterior crossbite (UAC) has an impact on the motor nuclei in the brain stem via trigeminal mesencephalic nucleus (Vme). The current aim was to explore whether UAC has an impact on Vpdm-cerebellum circuit. The inferior alveolar nerve was injected into cholera toxin B subunit (CTb), the cerebellum was injected into fluoro-gold (FG), and the Vpdm was injected into biotinylated dextran amine (BDA) to identify the activation of Vpdm-cerebellum circuit by UAC. Data indicated that there were more neuronal nuclei (NeuN)/CTb/FG triple-labelled neurons and NeuN/CTb/vesicular glutamate transporter 1(VGLUT1) triple-labelled neurons in the Vpdm, and more NeuN/BDA/ VGLUT1 triple-labelled neurons in the cerebellum of rats with UAC than in control rats. The VGLUT1 expression in the Vpdm and cerebellum in the UAC group was higher than that in control rats. These findings indicate an excitatory impact of UAC on the Vpdm-cerebellum pathway and support the role of occlusion for body posture and balance.

Effects of stereotactic radiofrequency thermocoagulation in the globus pallidus internus on refractory tic disorders.

OBJECTIVE: To investigate the effect of stereotactic radiofrequency thermocoagulation in the globus pallidus internus on refractory tic disorders. MATERIALS AND METHODS: Forty patients with refractory tic disorders were enrolled between January 2015 and July 2017 to experience stereotactic radiofrequency thermocoagulation in the globus pallidus internus. All clinical data, Yale Global Tic Severity Scale (YGTSS) scores, serum dopamine (SDA), and 5-hydroxytryptamine (5-HT) were analyzed. RESULTS: Radiofrequency thermocoagulation was successfully performed in all patients. Periprocedural complications occurred in two patients (5.0%), one with fever (2.5%) and one with a urination disorder (2.5%); both returned to normal after treatment. After 12 months of follow-ups, excellent improvement was exhibited in 18 patients (45.0%), marked improvement in 10 (25.0%), good improvement in 9 (22.5%), and invalid in 3 (7.5%), with a total efficacy rate of 92.5% (37/40). Twenty-eight patients (70%) showed excellent or marked improvement without additional treatment after surgery. YGTSS scores were significantly (p < 0.05) decreased after compared with before thermocoagulation. SDA was significantly (p < 0.05) decreased 6 months (80.78 ± 18.82 ng/ml) and 12 months (75.65 ± 15.23 ng/ml) after compared with before (125.63 ± 35.26 ng/ml) surgery, whereas 5-HT was significantly (p < 0.05) increased 6 months (58.93 ± 16.88 ng/ml) and 12 months (62.63 ± 15.21 ng/ml) after compared with before (35.62 ± 3.41 ng/ml) surgery. CONCLUSION: Stereotactic radiofrequency thermocoagulation can be safely applied in the globus pallidus internus to treat refractory tic disorders, resulting in significant tic symptom relief and a decrease in SDA but increase in 5-HT.

Stereotactic radiofrequency thermocoagulation application in the anterior limbs of patients' internal capsules in treating intractable tic disorders.

Purpose: To investigate the effect of applying stereotactic radiofrequency thermocoagulation in the anterior limbs of patients' internal capsules in treating intractable tic disorders.Materials and methods: Patients diagnosed with intractable tic disorders were prospectively enrolled and treated using stereotactic radiofrequency thermocoagulation in the anterior limbs of the internal capsules. Periprocedural complications, effects, and follow-up outcomes were then analyzed.Results: Fifty patients were enrolled, including 38 with Tourette syndrome and 12 with persistent refractory vocal or motor tic disorders. The radiofrequency thermocoagulation procedure was performed successfully in all patients. Five participants (10%) experienced periprocedural complications, including one having a slight hemiplegia, two developing fevers (4%), and two developing urination disorders (4%). The participants underwent a follow-up for 12 months, with excellent effects being achieved in 23 patients (46%), prominent results in 13 (26%), good results in 10 (20%), and invalid results in 4 (8%), reaching an efficacy rate of 92% (46/50). Thirty-six patients experienced excellent and prominent effects, with no additional management after the radiofrequency ablation being needed, achieving a success rate of 72%. After radiofrequency thermocoagulation, the Yale Global Tic Severity Scale (YGTSS) scores were significantly reduced (p < .01) when compared with those before the procedure. Following this procedure, participants' serum dopamine levels (SDA) significantly decreased (p < .05), while their serotonin levels were significantly elevated (p < .05) when compared to the measurements taken before the procedure.Conclusion: Stereotactic radiofrequency thermocoagulation applied to the anterior limbs of patients' internal capsules may be effective for treating intractable tic disorders, without risk of serious complications.

Effects of occlusion modification on the remodelling of degenerative mandibular condylar processes.

OBJECTIVE: The temporomandibular joint (TMJ) displays a high remodelling capability in response to occlusion changes. The purpose of the current study was to investigate the responses of TMJ condyles of growing mice to the installation of a unilateral anterior crossbite (UAC) prosthesis and the replacement of the UAC prothesis with a bilateral anterior elevation (BAE) prosthesis. MATERIALS AND METHODS: C57BL/6J mice were randomly assigned to the blank control and experimental groups. In mice in the experimental groups, UAC was created, while in others, BAE was created after the creation of UAC or removal of UAC. Changes in TMJ condylar cartilage and subchondral bone were assessed. RESULTS: The degradation of condylar cartilage induced by UAC was reversed by BAE, as evaluated by cartilage histochemical changes, collagen II-positive area, collagen X-positive chondrocytes and expression levels of Adamts-5, Mmp13, Tnf-α and Il-1ß. Subchondral bone was assessed based on the subchondral bone volume, the number of TRAP-positive cells and the Opg/Rankl ratio. CONCLUSION: The growing mouse TMJ condyle displays a high remodelling capability, which can be degenerative or rehabilitative in response to the creation of UAC and the replacement of UAC with BAE. Early correction of occlusion is beneficial for the recovery of degenerative condyles.

The effect of 3D-printed plastic teeth on scores in a tooth morphology course in a Chinese university.

BACKGROUND: The tooth morphology course is an important basic dental course. However, it is difficult to fully reflect the three-dimensional (3D) morphological characteristics of tooth structure in two-dimensional pictures in traditional textbooks. The aim of this study was to assess the effect of 3D-printed plastic model teeth in the teaching of tooth morphology. METHODS: Twenty-two undergraduate students who matriculated at the School of Stomatology, the Fourth Medical University, in 2014 and 23 who matriculated in 2016 participated in the study. Each student who matriculated in 2016 was given a full set of fourteen standard 3D-printed plastic model teeth for use during the learning process, and an anonymous questionnaire was used to evaluate the usefulness of the 3D-printed plastic model teeth from the perspective of the students. RESULTS: There was no significant difference between the two groups in the scores of the theoretical examination or the total score. However, for the score of the sculpted gypsum teeth, the students who used the 3D-printed plastic model teeth in their studies scored significantly higher (P = 0.002). More than 90% of the students thought that the 3D-printed plastic model teeth were of great help or were very helpful for mastering the anatomy of teeth and for carving the gypsum teeth. CONCLUSION: Standard 3D-printed plastic teeth can effectively assist students in learning tooth morphology by transforming two-dimensional pictures and descriptions in the textbook into a 3D conformation, effectively promoting students' learning and mastery of tooth morphology and structure. Additionally, the results suggest that 3D-printed plastic model teeth are of great help to the students in mastering and improving their carving skills.

Bilateral anterior elevation prosthesis boosts chondrocytes proliferation in mice mandibular condyle.

OBJECTIVE: We aimed to develop a mouse model predominating in a proliferative response in the articular cartilage of the temporomandibular joints. MATERIALS AND METHODS: Bilateral anterior elevation of occlusion was developed by installing metal tubes onto the incisors of mice with edge-to-edge relation to prevent tooth wear, leading to an increase in the vertical height of the dental occlusion with time. Morphological changes and expression changes in Cyclin D1, Aggrecan, and type II and type X collagen in the mandibular condylar cartilage were detected. In addition, cells were isolated from the mandibular condylar cartilage and exposed to cyclic tensile strain (CTS). RESULTS: Compared with age-matched controls, the tooth length was longer at 3 weeks, 7 weeks, and 11 weeks in BAE mice (p < 0.05), with increased condylar cartilage thickness, matrix amount, and cell number (p < 0.05). Compared with the deep zone cells, CTS stimulated the superficial zone cells to express a higher level of proliferating cell nuclear antigen, Cyclin D1, Aggrecan, and type II collagen but a lower level of type X collagen and alkaline phosphatase. CONCLUSION: Bilateral anterior elevation stimulated the proliferative response in the mandibular condylar cartilage, offering a new therapeutic strategy for cartilage degeneration.

Early growth response 1 reduction in peripheral blood involving condylar subchondral bone loss.

OBJECTIVES: To detect whether early growth response 1 (EGR1) in peripheral blood leucocytes (PBLs) indicates temporomandibular joint (TMJ) osteoarthritis (OA) lesions. MATERIALS AND METHODS: Egr1 mRNA expression levels in PBLs were detected in eight malocclusion patients without temporomandibular disorder (TMD) signs and 16 malocclusion patients with clinical TMD signs with (eight) or without (eight) imaging signs of TMJ OA. Twelve 6-week-old rats were randomized to a control group and a unilateral anterior crossbite (UAC) group and were sampled at 4 weeks. The Egr1 mRNA expression levels in PBLs and protein expression levels in different orofacial tissues were measured. RESULTS: Patients with TMD signs with/without TMJ OA diagnosis showed lower Egr1 mRNA expression levels in PBLs than patients without TMD signs. The lower Egr1 mRNA expression was also found in the PBLs of UAC rats, which were induced to exhibit early histo-morphological signs of TMJ OA lesions. In subchondral bone of UAC rats, EGR1 protein expression was decreased, co-localization of EGR1 with osterix or dentin matrix protein-1 was identified, and the number of EGR1 and osterix double-positive cells was reduced (all p < .05). CONCLUSION: Egr1 reduction in PBLs potentially indicates subchondral bone OA lesions at an early stage.

Machined Surface Quality Monitoring Using a Wireless Sensory Tool Holder in the Machining Process.

The quality of a machined surface plays a critical role in assembly performance, especially for precise matching parts, and therefore it is necessary to develop a surface quality monitoring system in the machining process. In this paper, an indirect surface quality monitoring approach is proposed with a wireless sensory tool holder. First, experimentation is conducted to collect the machining process signals from the tool holder. Then, the time domain, frequency domain and time-frequency domain features are extracted, and the deep forest algorithm is adopted to identify the surface quality, which is evaluated through the surface average parameter. Finally, the results of the experiment and the comparisons with other approaches demonstrate the effectiveness of the proposed method, which could be applied to ensure the surface quality, improve the machining efficiency and reduce the rejection rate of the machining process.

Catabolic changes of rat temporomandibular joint discs induced by unilateral anterior crossbite.

BACKGROUND: The temporomandibular joint (TMJ) disc plays a role in joint movement and in load absorbance and distribution. An experimental unilateral anterior crossbite (UAC) prosthesis induces mandibular condylar cartilage degeneration in rats. However, the changes in the articular disc are still unknown. OBJECTIVE: To describe changes in the TMJ discs of UAC rats. METHODS: The discs of fifty-four Sprague-Dawley rats, equally distributed into a UAC group and an age-matched sham-operated control group at 4, 12 and 20 weeks (n = 9), were evaluated by gross and histomorphological observation and by detection at the mRNA or protein expression levels of the markers related to the matrix elements. RESULTS: No macro- or micro-morphological differences were observed between groups. However, there were catabolic degradative changes at the molecular level in the UAC group, showing a significant reduction in the mRNA and/or protein expression levels of many molecules. The reduction became worse with time (P < 0.05). The reduced molecules included: (a) those related to the extracellular matrix, such as type I collagen, decorin and fibromodulin; (b) those related to chondrogenesis, such as type II collagen and aggrecan; and (c) those related to osteogenesis, such as alkaline phosphatase and runt-related transcription factor 2. The mRNA expression of vascular endothelial growth factor did not change. In contrast, fibronectin, which can promote wound healing, and its N-terminal fragment, which can induce cartilage degradation, were accumulated (P < 0.05). CONCLUSION: TMJ discs were stimulated to catabolic changes by the aberrant dental occlusion and seemed to go to inanimate with time.

Molecular changes in peripheral blood involving osteoarthritic joint remodelling.

Biomarkers of temporomandibular joint (TMJ) osteoarthritis (OA) remain unknown. The objective was to detect whether molecular biomarkers from peripheral blood leucocytes (PBLs) engage in TMJ OA lesions. Thirty-four six-week-old Sprague Dawley rats were used. The top upregulated gene ontology categories and gene-fold changes in PBLs were detected by a microarray analysis comparing rats that received 20-week unilateral anterior crossbite (UAC) treatment with age-matched controls (n = 4). Twenty weeks of UAC treatment had been reported to induce TMJ OA-like lesions. The other twenty-four rats were randomly placed in the UAC and control groups at 12- and 20-week time points (n = 6). The mRNA expression levels of the selected biomarkers derived from the microarray analysis and their protein expression in the alveolar bone and TMJ were detected. The microarray analysis indicated that the three most highly involved genes in PBLs were Egr1, Ephx1 and Il10, which were confirmed by real-time PCR detection. The increased protein expression levels of the three detected molecules were demonstrated in cartilage and subchondral bone (P < 0.05), and increased levels of EPHX1 were reported in discs (P < 0.05); however, increased levels were not present in the alveolar bone. Immunohistochemistry revealed the increased distribution of EGR1-positive, EXPH1-positive and IL10-positive cells predominantly in the osteochondral interface, with EXPH1 also present in TMJ discs. In conclusion, the increased mRNA expression of Egr1, Ephx1 and Il10 in PBLs may serve as potential biomarkers for developed osteoarthritic lesions relating to osteochondral interface hardness changes induced by dental biomechanical stimulation.

Inhibition of Ihh Reverses Temporomandibular Joint Osteoarthritis via a PTH1R Signaling Dependent Mechanism.

The temporomandibular joint (TMJ), which is biomechanically related to dental occlusion, is often insulted by osteoarthritis (OA). This study was conducted to clarify the relationship between Indian hedgehog (Ihh) and parathyroid hormone receptor 1 (PTH1R) signaling in modulating the enhanced chondrocyte terminal differentiation in dental stimulated TMJ osteoarthritic cartilage. A gain- and loss-of-function strategy was used in an in vitro model in which fluid flow shear stress (FFSS) was applied, and in an in vivo model in which the unilateral anterior cross-bite (UAC) stimulation was adopted. Ihh and PTH1R signaling was modulated through treating the isolated chondrocytes with inhibitor/activator and via deleting Smoothened (Smo) and/or Pth1r genes in mice with the promoter gene of type 2 collagen (Col2-CreER) in the tamoxifen-inducible pattern. We found that both FFSS and UAC stimulation promoted the deep zone chondrocytes to undergo terminal differentiation, while cells in the superficial zone were robust. We demonstrated that the terminal differentiation process in deep zone chondrocytes promoted by FFSS and UAC was mediated by the enhanced Ihh signaling and declined PTH1R expression. The FFSS-promoted terminal differentiation was suppressed by administration of the Ihh inhibitor or PTH1R activator. The UAC-promoted chondrocytes terminal differentiation and OA-like lesions were rescued in Smo knockout, but were enhanced in Pth1r knockout mice. Importantly, the relieving effect of Smo knockout mice was attenuated when Pth1r knockout was also applied. Our data suggest a chondrocyte protective effect of suppressing Ihh signaling in TMJ OA cartilage which is dependent on PTH1R signaling.

Dental malocclusion stimulates neuromuscular circuits associated with temporomandibular disorders.

Unilateral anterior crossbite (UAC) has been demonstrated to cause masseter hyperactivity via the periodontal trigeminal mesencephalic nucleus (Vme)-trigeminal motor nucleus circuit. Here, we studied activation of motor neurons of the facial nucleus (VII), hypoglossal nucleus (XII), nucleus ambiguus (Amb), and spinal nucleus of the accessory nerve (SNA) in rats with UAC via their similar connections with Vme. An anterograde tracer, biotinylated dextran amine (BDA), was injected into the Vme to identify the central axon terminals around the motor neurons of VII, XII, Amb, and SNA. The expression of vesicular glutamate transporter 1 (VGLUT1) in neurons of VII, XII, Amb, and SNA, and the expression of acetylcholinesterase (AChE) were measured in the stapedius, lingualis, palatopharyngeal, and sternocleidomastoid muscles. In BDA-treated rats, many BDA-labeled cell bodies in the Vme and terminals in VII, XII, Amb, and SNA were identified. Compared with control rats, rats with UAC showed higher expression of VGLUT1 in these nuclei, and statistically significantly higher expression of AChE in the stapedius, lingualis, and sternocleidomastoid muscles, but not in the palatopharyngeal muscle. These findings suggest that UAC activates orofacial, head, and cervical multimotor behaviors via connections between the Vme and the corresponding motor nuclei.