Effects of endoplasmic reticulum stress on chondrocyte apoptosis via the PI3K/AKT signaling pathway.

Chondrocytes undergo endoplasmic reticulum stress (ERS)-induced apoptosis under abnormal stimulation. However, the underlying molecular mechanism remains unclear. We investigated the regulatory effect of the PI3K/AKT signaling pathway on ERS and its effect on chondrocyte apoptosis. In addition, we established a unilateral anterior crossbite (UAC) model in rats to induce temporomandibular joint osteoarthritis (TMJOA). Chondrocytes were isolated from the temporomandibular joints and treated with lipopolysaccharide (LPS) in vitro. Protein expression of ERS and apoptosis markers (GRP78 and CASP12) was analyzed by immunohistochemistry and western blotting. The expression of GRP78, CASP12, p-PI3K, and p-AKT significantly increased in the UAC group. LY294002, a PI3K/AKT signaling pathway inhibitor, reduced the protein expression of GRP78, ATF4, CHOP, and CASP12, whereas 740 Y-P, an activation agent, elevated the expression of proteins GRP78, ATF4, CHOP, and CASP12. In the present study, UAC and LPS stimulation induced apoptosis of chondrocytes in the ERS pathway. Inhibition of the PI3K/AKT signaling pathway reduced ERS-induced chondrocyte apoptosis.

A comparison of the burden of knee osteoarthritis attributable to high body mass index in China and globally from 1990 to 2019.

Background: Excess body mass index (BMI) plays a key role in the onset and progression of knee osteoarthritis (knee OA). However, the burden of knee OA attributable to high BMI at the global, Chinese, and regional levels have received far too little attention. The aim of this study is to provide evidence to support the design of policy by investigating long-term trends of years lived with disability (YLDs) for knee OA. Methods: To illustrate the trends of YLDs for knee OA attributable to high BMI and the temporal trends of the YLDs rate by age, period, and cohort, Joinpoint regression software and age-period-cohort (APC) were used to analyze the YLDs data of knee OA from the Global Burden of Disease (GBD) 2019. Results: In China, there were 549,963.5 YLDs for knee OA attributable to high BMI in 2019, which had increased by 460.7% since 1990. From 1990 to 2019, age-standardized disability-adjusted life year rate (ASDR) of knee OA attributable to high BMI trended upwards. The average annual percent change (AAPC) of knee OA attributable to high BMI in China and globe were 3.019, 1.419%, respectively. The longitudinal age curve of the APC model showed that the YLDs rates of knee OA due to high BMI increased with age, and YLDs rates were higher among females than males. The period rate ratios (RRs) of knee OA due to high BMI increased significantly. The cohort RRs of knee OA due to high BMI increased among those born between 1900 and 1970. The net drifts of knee OA attributable to high BMI in China and globe were above 1. Compared with global condition, the net drift values of knee OA attributable to high BMI in China was higher. Compared with females, males had higher net drift value. Countries with high socio-demographic index (SDI) have a much higher burden of knee OA caused by high BMI than countries with low SDI. Conclusion: In China, high BMI is a substantial cause of knee OA, the incidence of which has been increasing since 1990. In addition, women and the elderly are more vulnerable to knee OA caused by high BMI. The Chinese government must take the long-term impact of high BMI on knee OA into account and implement effective public health policies and resort to interventions to reduce the burden as soon as possible.

The current status of stimuli-responsive nanotechnologies on orthopedic titanium implant surfaces.

With the continuous innovation and breakthrough of nanomedical technology, stimuli-responsive nanotechnology has been gradually applied to the surface modification of titanium implants to achieve brilliant antibacterial activity and promoted osteogenesis. Regarding to the different physiological and pathological microenvironment around implants before and after surgery, these surface nanomodifications are designed to respond to different stimuli and environmental changes in a timely, efficient, and specific way/manner. Here, we focus on the materials related to stimuli-responsive nanotechnology on titanium implant surface modification, including metals and their compounds, polymer materials and other materials. In addition, the mechanism of different response types is introduced according to different activation stimuli, including magnetic, electrical, photic, radio frequency and ultrasonic stimuli, pH and enzymatic stimuli (the internal stimuli). Meanwhile, the associated functions, potential applications and developing prospect were discussion.

Carcinogenesis promotion in oral squamous cell carcinoma: KDM4A complex-mediated gene transcriptional suppression by LEF1.

Oral squamous cell carcinoma (OSCC) is the most prevalent cancer of the mouth, characterised by rapid progression and poor prognosis. Hence, an urgent need exists for the development of predictive targets for early diagnosis, prognosis determination, and clinical therapy. Dysregulation of lymphoid enhancer-binding factor 1 (LEF1), an important transcription factor involved in the Wnt-ß-catenin pathway, contributes to the poor prognosis of OSCC. Herein, we aimed to explore the correlation between LEF1 and histone lysine demethylase 4 A (KDM4A). Results show that the KDM4A complex is recruited by LEF1 and specifically binds the LATS2 promoter region, thereby inhibiting its expression, and consequently promoting cell proliferation and impeding apoptosis in OSCC. We also established NOD/SCID mouse xenograft models using CAL-27 cells to conduct an in vivo analysis of the roles of LEF1 and KDM4A in tumour growth, and our findings show that cells stably suppressing LEF1 or KDM4A have markedly decreased tumour-initiating capacity. Overall, the results of this study demonstrate that LEF1 plays a pivotal role in OSCC development and has potential to serve as a target for early diagnosis and treatment of OSCC.

Influence of different education approaches on the implantation performance of dental practitioners in aesthetic zone.

PURPOSE: To investigate the influence of different education approaches on the implantation performance (operation time, three-dimensional deviation) of inexperienced operators. METHODS: Eighteen students who met the inclusion criteria were randomly assigned to traditional training group or digital training group. After training, the average operation time and implant deviation (platform deviation, apex deviation, and angle deviation) of the two groups were calculated by Student's t-test. A self-developed questionnaire was used to evaluate the students' grasp of clinical knowledge and skill. RESULT: Compared with the traditional training group, the duration of implant installation and temporary prosthesis placement of the digital training group decreased significantly (p < 0.05). The implant deviation of the digital training group was lower than that of the traditional training group. The apex deviation (p = 0.015) and angle deviation (p = 0.015) significantly improved with digital training, but differences in platform deviation (p = 0.065) were not statistically significant. The questionnaire survey showed that the overall perception of the inexperienced operators in the digital training group was better than that in the traditional training group. CONCLUSION: In the hands of inexperienced operators, digital training reduced the operation time and improved the implant accuracy in comparison with traditional training.

Whole-transcriptome sequencing and ceRNA interaction network of temporomandibular joint osteoarthritis.

Purpose: The aim of this study was to conduct a comprehensive transcriptomic analysis to explore the potential biological functions of noncoding RNA (ncRNAs) in temporomandibular joint osteoarthritis (TMJOA). Methods: Whole transcriptome sequencing was performed to identify differentially expressed genes (DEGs) profiles between the TMJOA and normal groups. The functions and pathways of the DEGs were analyzed using Metascape, and a competitive endogenous RNA (ceRNA) network was constructed using Cytoscape software. Results: A total of 137 DEmRNAs, 65 DEmiRNAs, 132 DElncRNAs, and 29 DEcircRNAs were identified between the TMJOA and normal groups. Functional annotation of the DEmRNAs revealed that immune response and apoptosis are closely related to TMJOA and also suggested key signaling pathways related to TMJOA, including chronic depression and PPAR signaling pathways. We identified vital mRNAs, including Klrk1, Adipoq, Cryab, and Hspa1b. Notably, Adipoq expression in cartilage was significantly upregulated in TMJOA compared with normal groups (10-fold, p < 0.001). According to the functional analysis of DEmRNAs regulated by the ceRNA network, we found that ncRNAs are involved in the regulation of autophagy and apoptosis. In addition, significantly DEncRNAs (lncRNA-COX7A1, lncRNA-CHTOP, lncRNA-UFM1, ciRNA166 and circRNA1531) were verified, and among these, circRNA1531 (14.5-fold, p < 0.001) and lncRNA-CHTOP (14.8-fold, p < 0.001) were the most significantly downregulated ncRNAs. Conclusion: This study showed the potential of lncRNAs, circRNAs, miRNAs, and mRNAs may as clinical biomarkers and provides transcriptomic insights into their functional roles in TMJOA. This study identified the transcriptomic signatures of mRNAs associated with immunity and apoptosis and the signatures of ncRNAs associated with autophagy and apoptosis and provides insight into ncRNAs in TMJOA.

Corrigendum: Circadian rhythm protein Bmal1 modulates cartilage gene expression in temporomandibular joint osteoarthritis via the MAPK/ERK pathway.

[This corrects the article DOI: 10.3389/fphar.2020.527744.].

Animal Models of Temporomandibular Joint Osteoarthritis: Classification and Selection.

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

Low-intensity pulsed ultrasound promotes aggrecan expression via ZNT-9 in temporomandibular joint chondrocytes.

Temporomandibular joint osteoarthritis (TMJ-OA) is one of the most common joint diseases. It causes severe pain and poor quality of life. One key feature of TMJ-OA is degeneration of the chondrocyte extracellular matrix (ECM). Low-intensity pulsed ultrasound (LIPUS) can promote the synthesis of ECM in cartilage. However, the exact mechanism is still unclear. We aimed to explore the mechanism by which LIPUS promotes the expression of aggrecan in chondrocytes. In vivo, TMJ-OA rats established by unilateral occlusal trauma were treated with LIPUS. In our RNA sequencing data, we found that ADAMTS-8 was downregulated by LIPUS. In vitro, chondrocytes were treated with IL-1ß and LIPUS. Among Zn2+ exporters, ZNT-9 was specifically upregulated by LIPUS. Activation of ZNT-9 by LIPUS downregulated ECM-degrading enzymes (MMP-3, ADAMTS-5 and ADAMTS-8) and metal regulatory transcription factor-1 (MTF-1) and upregulated aggrecan in chondrocytes. Furthermore, ZNT-9 knockdown caused upregulation of MMP-3, ADAMTS-5, ADAMTS-8 and MTF-1, with concomitant downregulation of aggrecan. The opposite results were obtained after ZNT-9 overexpression. Our experiments demonstrate that LIPUS protects chondrocytes by increasing the expression of aggrecan through ZNT-9.

Does tourniquet use affect the periprosthetic bone cement penetration in total knee arthroplasty? A meta-analysis.

BACKGROUND: A tourniquet is a device commonly used to control massive hemorrhage during knee replacement surgery. However, the question remains whether the use of tourniquets affects the permeability of the bone cement around the knee prosthesis. Moreover, the long-term effects and stability of the knee prosthesis are still debatable. The aim of this study was to examine whether the use of a tourniquet increases the thickness of the cement mantle and affects the postoperative blood loss and pain during primary total knee arthroplasty (TKA) using meta-analysis. METHODS: We searched the Cochrane Central Library, MEDLINE, Embase, PubMed, CNKI, and Wang Fang databases for randomized controlled trials (RCTs) on primary TKA, from inception to November 2019. All RCTs in primary TKA with and without a tourniquet were included. The meta-analysis was conducted using RevMan 5.2 software. RESULTS: A total of eight RCTs (677 knees) were analyzed. We found no significant difference in the age and sex of the patients. The results showed that the application of tourniquet affects the thickness of the bone cement around the tibial prosthesis (WMD = 0.16, 95%CI = 0.11 to 0.21, p < 0.00001). However, in our study, there was no significant difference in postoperative blood loss between the two groups was observed (WMD = 12.07, 95%CI = - 78.63 to 102.77, p = 0.79). The use of an intraoperative tourniquet can increase the intensity of postoperative pain (WMD = 1.34, 95%, CI = 0.32 to 2.36, p = 0.01). CONCLUSIONS: Tourniquet application increases the thickness of the bone cement around the prosthesis and may thus increase the stability and durability of the prosthesis after TKA. The application of an intraoperative tourniquet can increase the intensity of postoperative pain.

Circadian Rhythm Protein Bmal1 Modulates Cartilage Gene Expression in Temporomandibular Joint Osteoarthritis via the MAPK/ERK Pathway.

The purpose of this study was to elucidate the role of the circadian gene Bmal1 in human cartilage and its crosstalk with the MAPK/ERK signaling pathway in temporomandibular joint osteoarthritis (TMJ-OA). We verified the periodical variation of the circadian gene Bmal1 and then established a modified multiple platform method (MMPM) to induce circadian rhythm disturbance leading to TMJ-OA. IL-6, p-ERK, and Bmal1 mRNA and protein expression levels were assessed by real-time RT-PCR and immunohistochemistry. Chondrocytes were treated with an ERK inhibitor (U0126), siRNA and plasmid targeting Bmal1 under IL-6 simulation; then, the cells were subjected to Western blotting to analyze the relationship between Bmal1 and the MAPK/ERK pathway. We found that sleep rhythm disturbance can downregulate the circadian gene BMAL-1 and improve phosphorylated ERK (p-ERK) and IL-6 levels. Furthermore, Bmal1 siRNA transfection was sufficient to improve the p-ERK level and aggravate OA-like gene expression changes under IL-6 stimulation. Bmal1 overexpression relieved the alterations induced by IL-6, which was consistent with the effect of U0126 (an ERK inhibitor). However, we also found that BMAL1 upregulation can decrease ERK phosphorylation, whereas ERK downregulation did not change BMAL1 expression. Collectively, this study provides new insight into the regulatory mechanism that links chondrocyte BMAL1 to cartilage maintenance and repair in TMJ-OA via the MAPK/ERK pathway and suggests that circadian rhythm disruption is a risk factor for TMJ-OA.

Low-Intensity Pulsed Ultrasound Modulates RhoA/ROCK Signaling of Rat Mandibular Bone Marrow Mesenchymal Stem Cells to Rescue Their Damaged Cytoskeletal Organization and Cell Biological Function Induced by Radiation.

Osteoradionecrosis of the jaw (ORNJ) is an infrequent yet potentially devastating complication of head and neck radiation therapy. Low-intensity pulsed ultrasound (LIPUS) has been widely accepted as a promising method for the successful management of ORNJ, but the mechanism remains unclear. In this study, the effects of LIPUS on cytoskeletal reorganization, cell viability, and osteogenic differentiation capacity of rat mandible-derived bone marrow mesenchymal stem cells (M-BMMSCs) induced by radiation were determined by immunofluorescence staining, CCK-8 cell proliferation assay, quantification of alkaline phosphatase (ALP) activity, alizarin red staining, and real-time RT-PCR, respectively. Moreover, the involvement of the RhoA/ROCK signaling pathway underlying this process was investigated via western blot analysis. We found that radiation induced significant damage to the cytoskeleton, cell viability, and osteogenic differentiation capacity of M-BMMSCs and downregulated their expression of RhoA, ROCK, and vinculin while increasing FAK expression. LIPUS treatment effectively rescued the disordered cytoskeleton and redistributed vinculin. Furthermore, the cell viability and osteogenic differentiation capacity were also significantly recovered. More importantly, it could reverse the aberrant expression of the key molecules induced by radiation. Inhibition of RhoA/ROCK signaling remarkably aggravated the inhibitory effect of radiation and attenuated the therapeutic effect of LIPUS. In the light of these findings, the RhoA/ROCK signaling pathway might be a promising target for modifying the therapeutic effect of LIPUS on osteoradionecrosis.

The Optimal Regimen for the Treatment of Temporomandibular Joint Injury Using Low-Intensity Pulsed Ultrasound in Rats with Chronic Sleep Deprivation.

Low-intensity pulsed ultrasound (LIPUS) is an emerging physical therapy for the treatment of early temporomandibular joint injury and has a good effect on promoting cartilage and subchondral bone tissue repair. However, the best LIPUS intensity and treatment duration remain unclear. This study is aimed at observing the preventive and therapeutic effects of different modes of LIPUS and at identifying the optimal LIPUS treatment regimen for temporomandibular joint injury. In the present study, rat models of temporomandibular joint injury were established using a chronic sleep deprivation (CSD) method, and the effect of LIPUS as intensities of 30, 45, and 60 mW/cm2 was observed at 7, 14, and 21 days. After CSD, the condylar cartilage of the rats demonstrated variable degrees of surface roughening, collagen fiber disarrangement or even partial exfoliation, decreased proteoglycan synthesis and cartilage thickness, decreased chondrocyte proliferation, decreased type 2 collagen (COL-2) expression, and increased matrix metalloproteinase- (MMP-) 3 expression at all three time points. When the rats with CSD received different intensities of LIPUS treatment, the pathological changes were alleviated to various extents. The groups receiving 45 mW/cm2 LIPUS showed the most significant relief of cartilage damage, and this significant effect was observed on days 14 and 21. These results demonstrated that LIPUS can effectively inhibit CSD-induced condylar cartilage damage in rats, and LIPUS treatment at an intensity of 45 mW/cm2 for at least 2 weeks is the optimal regimen for temporomandibular joint injury.

Surface sulfonation and nitrification enhance the biological activity and osteogenesis of polyetheretherketone by forming an irregular nano-porous monolayer.

Polyether-ether-ketone (PEEK) is becoming a popular component of clinical spinal and orthopedic applications, but its practical use suffers from several limitations. In this study, irregular nano-porous monolayer with differently functional groups was formed on the surface of PEEK through sulfonation and nitrification. The surface characteristics were detected by field-emission scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectrometry, water contact angle measurements and Fourier transform infrared spectroscopy. In vitro cellular behaviors were evaluated by cell adhesion, morphological changes, proliferation, alkalinity, phosphatase activity, real-time RT-PCR and western blot analyses. In vivo osseointegration was examined through micro-CT and histological assessments. Our results reveal that the irregular nano-porous of PEEK affect the biological properties. High-temperature hydrothermal NP treatment induced early osteogenic differentiation and early osteogenesis. Modification by sulfonation and nitrification can broaden the use of PEEK in orthopedic and dental applications. This study provides a theoretical basis for the wider clinical application of PEEK. a To obtain a uniform porous structure, PEEK samples were treated by concentrated sulfuric acid and fuming nitric acid (82-80%) with magnetic stirring sequentially. b Effects of nanopores on biological behavior of bMSCS.

Tibial plateau fracture related to unicompartmental knee arthroplasty: Two case reports and literature review.

RATIONALE: Unicompartmental knee arthroplasty (UKA) is an effective method to treat single compartment disease of the knee joint. Report about the complications of UKA, especially tibial plateau fractures, is rare. Given its rarity, its pathogenesis is not well described, and a standard of treatment is still not established. Therefore, relevant studies and analysis of this complication have a significant effect on helping physicians avoid risks and guide clinical diagnosis and treatment. PATIENT CONCERNS: The 1st case corresponds to a 70-year-old male patient who complained of knee pain, difficulty walking, nocturnal rest pain, and elevated skin temperature at 3 weeks after the left knee arthroplasty. The second case is a 72-year-old female patient who complained of left knee pain and swelling during movement at 2 weeks after the left knee arthroplasty. DIAGNOSIS: The 1st case showed a fracture of the medial malleolus of the left knee and a secondary depression of the medial tibial plateau in X-rays and the second case showed a fracture of the medial malleolus of the left knee in computed tomography (CT) and X-rays. INTERVENTIONS: The 1st case was treated with plate and screw fixation and the second case was treated conservatively and immobilized using brace and remained nonweight bearing for 6 weeks. OUTCOMES: After 1 year, both patients have good joint activity, and there was no pain or loosening of the prosthesis and fragment displacement. LESSONS: The incidence of tibial plateau fractures (TPF) related to UKA might be low, but fatal and difficult to treat. Its pathogenesis determines procedure-related factors; when fracture develops, treatment should be based on the degree of displacement, stability of implant fixation, etc.

Therapeutic effect of low-intensity pulsed ultrasound on temporomandibular joint injury induced by chronic sleep deprivation in rats.

Low-intensity pulsed ultrasound (LIPUS) treatment is an emerging physical therapy for treating bone, nerve, and muscle disorders. However, there have been no reports on the effectiveness of LIPUS for the treatment of temporomandibular joint injury, and the mechanisms of LIPUS remain unclear. The purpose of this study was to examine the therapeutic effects of LIPUS on temporomandibular joint injury in rats subjected to chronic sleep deprivation (CSD). In this study, after 2 weeks of chronic sleep deprivation in rats, the condylar cartilage exhibited rough surfaces, with a disorganized arrangement and partial sloughing of collagen fibers, decreased proliferation of chondrocytes, increased osteoclast activity in the calcified cartilage layer, and increased ratios of MMP-3/TIMP-1 and RANKL/OPG expression. After 4 weeks of LIPUS intervention in rats, the condylar cartilage displayed prominent reductions in these pathological changes, including noticeable repair of the injured cartilage structure, increased chondrocyte proliferation, a reduced number of osteoclasts, and marked reductions in the expression ratios of MMP-3/TIMP-1 and RANKL/OPG. These results demonstrated that LIPUS can effectively inhibit CSD-induced injury to condylar cartilage in rats. The therapeutic mechanism of LIPUS may involve promoting the repair function of chondrocytes and reducing the expression ratios of MMP-3/TIMP-1 and RANKL/OPG in condylar tissue, thus inhibiting the cleavage activity of MMP-3 on the condylar cartilage matrix and inhibiting osteoclast activation.

RNA sequencing reveals target genes of temporomandibular joint osteoarthritis in rats after the treatment of low-intensity pulsed ultrasound.

PURPOSE: To explore the potential molecular mechanism of low-intensity pulsed ultrasound (LIPUS) in the treatment of temporomandibular joint osteoarthritis (TMJ-OA), and identify the target genes for therapy of TMJ-OA. METHODS: Rat TMJ-OA was induced by unilateral occlusal trauma (UOT). At 8 weeks, the experimental group rats were treated by LIPUS for 4 weeks (5 days every week). The cartilage was examined by histological techniques. Gene expression profile in control, placebo and LIPUS-treated group were measured by RNA sequencing (RNA-Seq). Gene oncology (GO) and kyoto encyclopedia of genes and genomes (KEGG) annotated were performed and ten differentially expressed genes (DEGs) were further validated in another individual by quantitative real-time polymerase chain reaction (qRT-PCR). Per-2, a circadian rhythm gene, was further confirmed by western blot. RESULTS: TMJ-OA model was successfully established in rats through UOT. LIPUS played a positive role in attenuating the retrogression of cartilage. The cartilage lesion was determined by HE and Safranin-O staining. A significant and bran-new gene profile of 58 mRNAs was obtained from the RNA-Seq (LIPUS-treated/placebo) and generated approximately 30GB data. Annotation, functional classification and pathway of the data were analyzed based on GO and KEGG database and ten candidate DEGs were identified. Some of these genes were proved to be related to OA, such as matrix-degrading enzyme (ADAMTS-8), complement (C1qa, C3, C5aR1). Some were reported for the first time in TMJ-OA, such as circadian gene (Per-2, Dbp, Npas2 and Arntl). According to the results of qRT-PCR validation, the sequencing data was with a high degree of credibility. The circadian gene Per-2 was up-regulated by LIPUS in TMJ-OA on the mRNA and protein level. CONCLUSION: This study reveals the potential therapeutic genes related to TMJ-OA. Especially the circadian Per-2 gene was detected up-regulated by the treatment of LIPUS. It provides us a precious, new target OA-related gene and further investigation of gene-function will provide us new insights in understanding the potential mechanical underling TMJ-OA.