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.

Low-frequency pulsed electromagnetic fields alleviate the condylar cartilage degeneration and synovitis at the early stage of temporomandibular joint osteoarthritis.

BACKGROUND: Temporomandibular joint osteoarthritis (TMJOA) is characterized by articular cartilage degeneration and progressive synovitis. How to effectively inhibit TMJOA in the early stage has been a hot topic in the biomedical field. As a non-invasive physiotherapy, pulsed electromagnetic field (PEMF) treatment has shown great potential in the treatment of osteoarthritis (OA) in extremity joints. OBJECTIVE: This study aims to investigate the biological effect of PEMF intervention on TMJ cartilage degeneration and synovium inflammation at the early stage of TMJOA. METHODS: PEMF (2.0 mT, 15 Hz, 2 h/day) treatment was given to rats in which TMJOA was induced by applying the unilateral anterior crossbite (UAC). Histological and immunohistochemical staining, TUNEL assay, real-time PCR and western blotting assay were performed to detect the changes of the morphology and the expression of pro-inflammatory and degradative factors in condylar cartilage and synovium. RESULTS: Obvious condylar cartilage degeneration, characterized by decreased cartilage thickness, degraded cartilage extracellular matrix, increased expression of pro-inflammatory and degradative factors (TNF-α, IL-1ß, MMP-13, ADAMTS-5, IL-6, MMP-3, MMP-9 and COL-X) and increased chondrocytes death, was observed in UAC group, accompanied by synovium hyperplasia and up-regulation of pro-inflammatory and degradative factors in synovium. PEMF intervention reversed the decreased cartilage thickness at 3 weeks and degraded cartilage extracellular matrix at 6 weeks. Moreover, the up-regulation of pro-inflammatory, degradative and hypertrophyic factors and chondrocytes death in condylar cartilage induced by UAC were inhibited to some extent. In addition, the synovium hyperplasia and the up-regulation of pro-inflammatory and degradative factors in synovium were inhibited at 3 weeks and 6 weeks. CONCLUSIONS: Appropriate PEMF stimulation can reverse the loss of cartilage extracellular matrix, the chondrocytes death, the increased expression of pro-inflammatory and degradative factors in cartilage, the decreased cartilage thickness and synovium inflammation induced by UAC at the early stage of TMJOA to some extent. PEMF stimulation may be a promising method in clinical TMJOA treatment.

Low frequency pulsed electromagnetic fields exposure alleviate the abnormal subchondral bone remodeling at the early stage of temporomandibular joint osteoarthritis.

BACKGROUND: Temporomandibular joint osteoarthritis (TMJOA) is characterized by abnormal subchondral bone remodeling and cartilage degeneration. As a non-invasive biophysical technology, pulsed electromagnetic field (PEMF) treatment has been proven to be efficient in promoting osteogenesis. However, the potential bone protective effect and mechanism of PEMF on abnormal subchondral bone remodeling in TMJOA are unknown. METHODS: Unilateral anterior crossbite (UAC) was used to create TMJOA model in rats, and 17ß-estradiol (E2) were injected daily to mimic patients with high-physiological levels of estrogen. Mouse osteoblast-like MC3T3-E1 cells treated with recombinant murine IL-1ß was used to establish inflammatory environment in vitro. The treatment group were subjected to PEMF (2.0mT, 15 Hz, 2 h/d). Micro-CT scanning, histological staining, real-time PCR and western blotting assays were preformed to observe the changes in the subchondral bone. RESULTS: Abnormal resorption of subchondral bone induced by UAC, characterized by decreased bone mineral density, increased osteoclast activity and expression of osteoclast-related factors (RANKL) and down-regulated expression of osteogenesis-related factors (OPG, ALP, Runx2 and OCN) at the early stage, could be reversed by PEMF exposure, which was similar to the effect of estrogen. In addition, PEMF exposure and E2 supplement may have a synergistic effect to some extent. Moreover, PEMF exposure could promote the ALP activity and osteogenic mineralization ability of MC3T3-E1 cells. PEMF promoted the expression of factors related to Wnt/ß-Catenin signal pathway both in vivo and in vitro. CONCLUSIONS: Appropriate PEMF exposure have a protective effect on subchondral bone in TMJOA at early stage, in which canonical Wnt/ß-Catenin pathway may be involved. PEMF may be a promising biophysical approach for early intervention of TMJOA in clinic.

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.

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.

The effect of methamphetamine abuse on dental caries and periodontal diseases in an Eastern China city.

BACKGROUND: Dental diseases are among the most frequently reported health problems in drug abusers. However, few studies have been conducted on oral health of methamphetamine (meth) abusers in China. The aim of the present study was to investigate the caries and periodontal health profile of former meth abusers in Eastern China. METHODS: A cross-sectional study was conducted on 162 former meth abusers in the male Zhoushan Compulsory Detoxification Center. A standardized questionnaire, which collected information about age, drug-use duration / pattern, oral hygiene habit and systemic diseases, was administered. Then, a dental examination was performed to investigate the severity of dental caries and periodontal diseases. In evaluating dental caries, the prevalence of dental caries, the scores of decayed teeth (DT), missing teeth (MT), filled teeth (FT), and decayed, missing, filled teeth (DMFT) were recorded. In evaluating periodontal diseases, community periodontal index (CPI), and the prevalence of gingival bleeding, dental calculus, periodontal pocket and loose teeth, were recorded. Additionally, the non-parametric test was adopted to analyze the potential risk factors via SPSS. RESULTS: All the participants abused meth by inhalation. The mean scores of DT, MT, FT and DMFT in the former meth users were 2.72 ± 2.78, 3.07 ± 3.94, 0.33 ± 1.03 and 6.13 ± 5.20 respectively. The prevalence of gingival bleeding, dental calculus, periodontal pocket and loose teeth was 97.53%, 95.68%, 51.23% and 9.26% respectively. The DT, DMFT and CPI scores in those who had abused meth for longer than 4 years were significantly higher than those who abused for less than 4 years (P = 0.039, 0.045, P < 0.001, respectively). The DT score in those who brushed their teeth more than twice a day were significantly lower than those who brushed less (P = 0.018). CONCLUSIONS: The status of caries and periodontal diseases among former male meth users in Eastern China was poor. Prolonged drug abuse and lower frequency of tooth brushing may be the risk factors of their poor status of caries and periodontal diseases.

Zinc Finger Protein 259 (ZNF259) Polymorphisms are Associated with the Risk of Metabolic Syndrome in a Han Chinese Population.

BACKGROUND: Zinc finger protein 259 (ZNF259) binds to the cytoplasmic domain of epidermal growth factor receptor (EGFR) in quiescent cells and contributes tolipid metabolism. This case and control study investigated the association between ZNF259 single nucleotide polymorphisms (SNPs) and metabolic syndrome (MetS). METHODS: This study included 1,812 MetS patients and 2,036 controls from the Jilin province of Northeastern China. MetS was diagnosed using the International Diabetes Federation (IDF) criteria. Three ZNF259 SNPs (rs964184, rs2075290 and rs2075294) were genotyped using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS). RESULTS: There were significant differences between metabolic syndrome and healthy control subjects for the ZNF259 rs964184 and rs2075290 genotypes. The minor alleles of both SNPs were associated with an increased risk of MetS and associated conditions (elevated triglycerides, elevated blood pressure, increased abdominal obesity, fasting hyperglycemia, and low HDL-C; p < 0.05). The distribution of haplotype G-G-G (rs964184, rs2075290 and rs2075294) was significantly different between MetS patients and controls (OR = 1.39; 95% CI, 1.24 - 1.56; p < 0.01). CONCLUSIONS: This study demonstrated that ZNF259 variants were associated with elevated MetS risk in a Han Chinese population from the Jilin province of Northeastern China.

Enhancement of chondrocyte autophagy is an early response in the degenerative cartilage of the temporomandibular joint to biomechanical dental stimulation.

Autophagy is a cell protective mechanism for maintaining cellular homeostasis. The present study aimed to investigate whether autophagy is enhanced in the biomechanically induced degenerative cartilage of the temporomandibular joint (TMJ) and the potential role of mitogen-activated protein kinase kinase kinase kinase 3 (MAP4K3) and mammalian Target of rapamycin (mTOR) in this observation. To induce degenerative changes in the TMJs, rats were subjected to biomechanical dental stimulation by moving 4 molars away from their original position as we previously reported. The ultrastructure of autophagosome was observed by transmission electron microscopy. The number of lysosomes was analyzed by flow cytometry. The expression levels of Beclin1 and LC3 and the involvement of MAP4K3 activity were detected by immunohistochemistry, real-time PCR and western blot. The activity of the mTOR pathway indicated by p-mTOR and p-p70S6 K was assayed by western blot. TMJ degeneration, characterized by irregular cell arrangement and cell-free area, was induced in the experimental groups. Under transmission electron microscopy, we observed the presence of autophagosomes, small patches of condensed chromatin, abundant rough endoplasmic reticulum and Golgi apparatus. The number of lysosomes and the expression levels of Beclin1 and LC3 increased, while the activity of mTOR and the expression level of MAP4K3 decreased in the experimental groups. Cartilage in TMJ which was induced to be degenerative biomechanically exhibited autophagy accompanied by reduced mTOR and MAP4K3 activity.

Proteomics based detection of differentially expressed proteins in human osteoblasts subjected to mechanical stress.

Mechanical stress is essential for bone development. Mechanical stimuli are transduced to biochemical signals that regulate proliferation, differentiation, and cytoskeletal reorganization in osteoblasts. In this study, we used proteomics to evaluate differences in the protein expression profiles of untreated Saos-2 osteoblast cells and Saos-2 cells subjected to mechanical stress loading. Using 2-D electrophoresis, MALDI-TOF mass spectroscopy, and bioinformatics, we identified a total of 26 proteins differentially expressed in stress loaded cells compared with control cells. Stress loaded Saos-2 cells exhibited significant upregulation of 17 proteins and significant downregulation of 9 proteins compared with control cells. Proteins that were most significantly upregulated in mechanically loaded cells included those regulating osteogenesis, energy metabolism, and the stress response, such as eukaryotic initiation factor 2 (12-fold), mitochondrial ATP synthase (8-fold), and peptidylprolyl isomerase A (cyclophilin A)-like 3 (6.5-fold). Among the proteins that were significantly downregulated were those involved in specific signaling pathways and cell proliferation, such as protein phosphatase regulatory (inhibitor) subunit 12B (13.8-fold), l-lactate dehydrogenase B (9.4-fold), Chain B proteasome activator Reg (Alpha) PA28 (7.7-fold), and ubiquitin carboxyl-terminal esterase L1 (6.9-fold). Our results provide a platform to understand the molecular mechanisms underlying mechanotransduction.

Excess genistein suppresses the synthesis of extracellular matrix in female rat mandibular condylar cartilage.

AIM: To investigate the effect of excess genistein on the extracellular matrix in mandibular condylar cartilage of female rats in vivo. METHODS: Female SD rats were administered through oral gavage with genistein (50 mg/kg) or placebo daily for 6 weeks. The morphological changes of temporomandibular joints were studied with HE staining. The expression of cartilage matrix compounds (aggrecan and collagen type II), estrogen-related molecules (aromatase, estradiol, ERα and ERß) and proliferating cell nuclear antigen (PCNA) in mandibular condylar cartilage was detected using immunohistochemistry, ELISA and real-time PCR. RESULTS: The genistein treatment significantly reduced the thickness of the posterior and middle regions of mandibular condylar cartilage, and decreased the expression of collagen type II, aggrecan and PCNA. Compared with the control group, the estradiol content and expression levels of the key estradiol-synthesizing enzyme aromatase in the genistein-treatment group were significantly decreased. The genistein treatment significantly increased the expression of ERß, but decreased the expression of ERα. CONCLUSION: Excess genistein suppresses extracellular matrix synthesis and chondrocytes proliferation, resulting in thinner mandibular condylar cartilage. These effects may be detrimental to the ability of mandibular condylar cartilage to adapt to mechanical loads.

Dose-dependent effects of genistein on bone homeostasis in rats' mandibular subchondral bone.

AIM: To investigate the effect of genistein on bone homeostasis in mandibular subchondral bone of rats. METHODS: Female SD rats were administered with genistein (10 and 50 mg/kg) or placebo by oral gavage for 6 weeks. Then the animals were sacrificed, and histomorphology and micro-structure of mandibular condyle were examined using HE staining and micro-CT analysis, respectively. The expression levels of alkaline phosphatase (ALP), osteocalcin (OC), osteoprotegerin (OPG), the receptor activator of nuclear factor κB ligand (RANKL) and estrogen receptors (ERs) in mandibular condyle were detected using real-time PCR. Cultured osteoblasts were prepared from rat mandibular condyle for in in vitro study. The cells were treated with genistein (10(-7) or 10(-4) mol/L) for 48 h. The expression of the bone homeostasis-associated factors and estrogen receptors (ERs) was detected using real-time PCR, and ER silencing was performed. RESULTS: At both the low- and high-doses, genistein significantly increased the bone mineral density (BMD) and bone volume, and resulted in thicker subchondral trabecular bone in vivo. In both in vivo and in vitro study, the low-dose genistein significantly increased the expression of ALP, OC and OPG, but decreased the expression of RANKL and the RANKL/OPG ratio. The high-dose genistein decreased the expression of all these bone homeostasis-associated factors. Both the low and high doses of genistein significantly increased the expression of ERß, while ERα expression was increased by the low dose genistein and decreased by the high dose genistein. ERß silencing abrogated most of the effects of genistein treatment. CONCLUSION: In rat mandibular condylar subchondral bone, low-dose genistein increases bone formation and inhibit bone resorption, while excess genistein inhibits both bone formation and resorption. The effects of genistein were predominantly mediated through ERß.

Effect of estrogen and dietary loading on condylar cartilage.

AIMS: To study the effect of estrogen deficiency and altered temporomandibular joint loading on the histomorphology of condylar cartilage and on the expression of types II and X collagen and matrix metalloproteinase-3 (MMP-3). METHODS: Thirty-six female rats were divided into four groups: ovariectomized rats on a normal diet, nonovariectomized control rats on a normal diet, ovariectomized rats on a soft diet, and nonovariectomized control rats on a soft diet. Ovariectomy was performed at the age of 60 days. Repeated-measures ANOVA was used to analyze the data. RESULTS: The condylar cartilage in the ovariectomized normal diet group showed a significantly higher number of cells than in the nonovariectomized control rats (P < .001). The proportional amount of MMP-3 expression was significantly higher in the ovariectomized rats than in the nonovariectomized control rats in both diet groups (P < .001). The area covered by types II and X collagen was significantly higher in the experimental groups than in the control groups (P < .01). CONCLUSION: Condylar cartilage is sensitive to both estrogen level and dietary loading.

Changes in the expression of aromatase, estrogen receptor α and ß in mandibular condylar cartilage of rats induced by disordered occlusion.

BACKGROUND: Estrogens play an important role in modulating the morphology and function of temporomandibular joints (TMJs), which is suggested to act via estrogen receptors (ERs). The present study was to investigate the expression of aggrecan, collagen type II (Col II), Col X, aromatase, ERα and ERß in degenerative changes of mandibular condylar cartilage. METHODS: Forty male and 40 female 8-week-old rats were enrolled in this study. In experimental groups, the disordered occlusion was created by moving the first molars mesially and the third ones distally. Immunohistochemistry and real-time PCR were performed at the end of the second or fourth week. RESULTS: Degenerative changes, characterized by interrupted continuity of hypertrophic layer, pyknotic and eosinophilic lesion with few nuclei, areas filled with eosinophilic nuclei, were observed in more joints from female experimental groups than male ones. However, thickening changes in hypertrophic layer were only found in male experimental groups. The gene expression of Col II, Col X and aggrecan increased in 4-wk male experimental subgroup (both P < 0.01), but decreased in 2-wk and 4-wk female subgroups (P < 0.05). The gene expression of ERα decreased in 2-wk male and female experimental subgroups (both P < 0.01), however, that of ERß increased except the 2-wk female experimental subgroup (all P < 0.01). The expression of aromatase decreased in both male and female experimental subgroups (all P<0.01). CONCLUSIONS: Mandibular condylar cartilage responses differently to the disordered occlusion in male and female rats. The levels of locally synthesized estrogen, ERα and ERß may have limited attribution, if any, to the sex-specific cartilage response.

Changes of myelinated nerve and myelin basic protein expression in rats' periodontal ligaments after experimental tooth movement.

INTRODUCTION: Information about the effect of tooth movement on the myelinated nerve in the periodontal ligament is limited. In this study, we aimed to investigate what responses of the periodontal myelinated nerve can be evoked during experimental tooth movement. METHODS: In experimental-I group, the maxillary left and mandibular right third molars were moved distally. In experimental-II group, the maxillary left third molar but not the right one was moved, and the bilateral mandibular third molars were extracted. The ultrastructures of the myelinated nerve in the periodontal ligament of the bilateral maxillary third molars were observed under a transmission electron microscope. The expression of myelin basic protein was evaluated by immunohistochemistry. RESULTS: Degenerative ultrastructural changes of the myelinated nerve in the periodontal ligament were noticed mainly in the myelin sheath; these were observed earlier and were recoverable in the experimental-I group. In contrast, the ultrastructural changes of the myelinated nerve occurred mainly in the axons, were observed later, and were unrecoverable in the experimental-II group. A concomitant decrease of myelin basic protein expression was observed in both groups. CONCLUSIONS: Both experimental tooth movement and occlusal changes accompanying it caused changes of the myelinated nerve in the periodontal ligament.

Degenerative changes in rat condylar cartilage induced by non-matching occlusion created by scattered orthodontic teeth-moving.

The effect of occlusion on the temporomandibular joint (TMJ) is debated. By inserting rubber-bands that were replaced by self-curing resin one week later, the left maxillary and the right mandibular first-molars were moved and kept mesially in Sprague-Dawley (SD) rats in both experimental I (EXP-I) and II (EXP-II) groups, aiming to establish a non-matching cusp-to-fossa occlusal relation. Four weeks later, the left maxillary and the right mandibular third-molars were moved and kept distally in the EXP-II group. Degenerative changes, typically as a cell-free area, were observed in TMJs of the EXP groups. Binary logistical analysis indicated that the odds ratio of EXP group, EXP-II vs. EXP-I, on the incidence of a cell-free area, was 2.8 (p=.036). Time point, gender, and side did not have such effects (p>0.05). The results indicate that the persistence of more scattered non-matching cusp-to-fossa occlusion is more harmful to the condylar cartilage in terms of the incidence of degenerative changes.

GDF11 inhibits abnormal adipogenesis of condylar chondrocytes in temporomandibular joint osteoarthritis.

AIMS: Abnormal lipid metabolism is involved in the development of osteoarthritis (OA). Growth differentiation factor 11 (GDF11) is crucial in inhibiting the differentiation of bone marrow mesenchymal stem cells into adipocytes. However, whether GDF11 participates in the abnormal adipogenesis of chondrocytes in OA cartilage is still unclear. METHODS: Six-week-old female mice were subjected to unilateral anterior crossbite (UAC) to induce OA in the temporomandibular joint (TMJ). Histochemical staining, immunohistochemical staining (IHC), and quantitative real-time polymerase chain reaction (qRT-PCR) were performed. Primary condylar chondrocytes of rats were stimulated with fluid flow shear stress (FFSS) and collected for oil red staining, immunofluorescence staining, qRT-PCR, and immunoprecipitation analysis. RESULTS: Abnormal adipogenesis, characterized by increased expression of CCAAT/enhancer-binding protein α (CEBPα), fatty acid binding protein 4 (FABP4), Perilipin1, Adiponectin (AdipoQ), and peroxisome proliferator-activated receptor γ (PPARγ), was enhanced in the degenerative cartilage of TMJ OA in UAC mice, accompanied by decreased expression of GDF11. After FFSS stimulation, there were fat droplets in the cytoplasm of cultured cells with increased expression of PPARγ, CEBPα, FABP4, Perilipin1, and AdipoQ and decreased expression of GDF11. Exogenous GDF11 inhibited increased lipid droplets and expression of AdipoQ, CEBPα, and FABP4 induced by FFSS stimulation. GDF11 did not affect the change in PPARγ expression under FFSS, but promoted its post-translational modification by small ubiquitin-related modifier (SUMOylation). Local injection of GDF11 alleviated TMJ OA-related cartilage degeneration and abnormal adipogenesis in UAC mice. CONCLUSION: Abnormal adipogenesis of chondrocytes and decreased GDF11 expression were observed in degenerative cartilage of TMJ OA. GDF11 supplementation effectively inhibits the adipogenesis of chondrocytes and thus alleviates TMJ condylar cartilage degeneration. GDF11 may inhibit the abnormal adipogenesis of chondrocytes by affecting the SUMOylation of PPARγ. Cite this article: Bone Joint Res 2022;11(7):453-464.

Inhibition of Semaphorin 4D/Plexin-B1 signaling inhibits the subchondral bone loss in early-stage osteoarthritis of the temporomandibular joint.

OBJECTIVE: The aim of this study was to demonstrate the biological function of Semaphorin 4D (Sema4D)/Plexin-B1 in the bone formation features of osteoblasts in early-stage temporomandibular joint (TMJ) osteoarthritis. DESIGN: Sema4D/Plexin-B1, expressed by osteoclasts/osteoblasts, plays a balancing role in bone formation and resorption. However, previous studies have mainly focused on bone resorption by osteoclasts in early-stage osteoarthritis. This study used our reported experimental unilateral anterior crossbite (UAC) mouse model to explore subchondral bone changes, which were assessed by micro-CT analysis. The changes in osteoblasts were investigated after the inhibition of Sema4D by BMA-12 injection with the detection of bone formation-related markers. A Transwell migration assay was performed to reveal the specific impact of Sema4D on osteoblasts in vitro. RESULTS: The data demonstrated that subchondral bone loss in early-stage TMJ osteoarthritis was accompanied by the upregulated expression of Sema4D in cartilage and subchondral bone and Plexin-B1 in subchondral bone. Reducing Sema4D levels could inhibit subchondral bone loss and cartilage degeneration in early-stage TMJ osteoarthritis. In vitro, the results revealed that Sema4D could reduce the expression of osteocalcin and alkaline phosphatase and increase the migrating capability of Plexin-B1-positive osteoblasts. CONCLUSIONS: Our results revealed that elevated Sema4D expression in early-stage TMJ osteoarthritis might decrease the bone formation activity of osteoblasts in the subchondral bone by binding to Plexin-B1 expressed by osteoblasts. Inhibiting Sema4D/Plexin-B1 signaling in early-stage osteoarthritis represents a promising strategy for new therapeutic approaches to osteoarthritis.