Osteoarthritis: toward a comprehensive understanding of pathological mechanism

Prevalence rates of arthritis among US older adults with varying degrees of depression: Findings from the 2011 to 2014 National Health and Nutrition Examination Survey

OBJECTIVE

Arthritis and depressive symptoms often interact and negatively influence one another to worsen mental and physical health outcomes. Better characterization of arthritis rates among older adults with different levels of depressive symptoms is an important step toward informing mental health professionals of the need to detect and respond to arthritis and related mental health complications. The primary objective is to determine arthritis rates among US older adults with varying degrees of depression.

METHODS

Using National Health and Nutrition Examination Survey 2011 to 2014 data (N = 4792), we first identified participants aged ≥50 years. Measures screened for depressive symptoms and self-reported doctor-diagnosed arthritis. Weighted logistic regression models were conducted.

RESULTS

Prevalence of arthritis was 55.0%, 62.9%, and 67.8% in participants with minor, moderate, and severe depression, respectively. In both unadjusted and adjusted regression models, a significant association between moderate depression and arthritis persisted. There were also significant associations between minor and severe depression with arthritis.

CONCLUSIONS

Arthritis is commonly reported in participants with varying degrees of depression. This study highlights the importance of screening for and treating arthritis-related pain in older adults with depressive symptoms and the need for future geriatric psychiatry research on developing integrated biopsychosocial interventions for these common conditions.

Strengthening the quadriceps femoris muscle versus other knee training programs for the treatment of knee osteoarthritis

People with knee osteoarthritis have atrophy of the muscles surrounding the knee joint. Therefore, exercise programs primarily have been focused on the strengthening of quadriceps femoris muscle (QFM). Primary aim of this systematic review was to determine which exercise increases strength of the QFM and describe the details of the training programs. Secondary aim was to determine effectiveness of strengthening of the QFM alone on pain and dysfunction in patient with knee osteoarthritis. PubMed, PEDro, and Cochrane were searched. PEDro for methodological quality of randomized controlled trials and Cochrane Collaborations' tool for risk of bias were used. A total of 1128 articles were identified from the database searches. Ten studies which were moderate-to-high level of evidence were included. In the comparison of different strengthening exercises of the QFM, significant difference was not found between training groups. However, strengthening of the QFM exercise training was superior to proprioceptive training. Additional hot packs plus shortwave diathermy or ultrasound or transcutaneous electrical nerve stimulation had superiority to isokinetic strengthening of the QFM alone. Only additional Russian electrical stimulation showed the significant difference compared with strengthening of the QFM exercise. Most of the included studies showed that strengthening of the QFM exercises has an effect on pain reduction and improvement of function. This review indicated that the strengthening of QFM training compared with other knee exercises provided muscle strengthening, pain reduction, and improved function while combination with other electrotherapy modalities or combination with Russian electrical stimulation had superiority to alone strengthening QFM training.

Is knee osteoarthritis related to coffee drinking? A nationwide cross-sectional observational study

AIMS

Coffee is one of the most consumed beverages globally, and coffee consumption is increasing. Osteoarthritis (OA), the most common musculoskeletal disease in the elderly, is also becoming more prevalent. Coffee is associated with various diseases, but there has not yet been a study of the relationship between coffee and knee OA. Therefore, we investigated this relationship in elderly Koreans.

METHODS

Data from 2012 to 2013 were collected from the Korea National Health and Nutrition Examination Survey. We included 2302 participants in our study: 897 men and 1405 women. Participants with knee OA were defined as those whose knee joints exhibited radiographic change of Kellgren-Lawrence grade 2 or higher. Daily coffee consumption amounts were categorized as none, < 2 cups, 2-3 cups, 4-6 cups, and ≥ 7 cups based on self-reporting.

RESULTS

A multiple logistic regression model, the odds ratios (ORs) of knee OA in the < 2 cup, 2-3 cup, 4-6 cup, and ≥ 7 cup groups compared to the no-coffee group in men were 1.13 (95% CI 0.50-2.55), 1.79 (95% CI 0.81-3.97), 2.21 (95% CI 0.91-5.35), and 3.81 (95% CI 1.46-12.45), respectively. There was no significant association between coffee consumption and knee OA prevalence in women.

CONCLUSION

Daily more than 7 cups of coffee drinking was associated with a prevalence of knee OA in Korean men, and although the ORs did not increase significantly across consumption levels, the prevalence of knee OA tended to increase with increasing coffee consumption.

A Randomized, Double Blind, Placebo Controlled, Parallel-Group Study to Evaluate the Safety and Efficacy of Curene® versus Placebo in Reducing Symptoms of Knee OA

Background

Curene® is a bioavailable formulation of turmeric  Curcucma longa extract comprising naturally derived curcuminoids formulated with proprietary Aquasome® technology. Curcuminoids were found to have anti-inflammatory properties by inhibiting Cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) enzyme and hence have potential application in the treatment of Osteoarthritis (OA). To evaluate the safety and efficacy of Curene® a randomized, double blind, placebo controlled, parallel-group study was conducted in subjects with knee OA. Significant improvements in clinical endpoints were observed during the trial along with excellent safety profile.

Methods

Fifty (50) subjects aged between 40 and 75 years who were suffering from unilateral or bilateral OA of the knee for greater than 3 months according to American College of Rheumatology (ACR) criteria were enrolled. They were randomized into two treatment groups; one group received Curene® 500 mg once daily and the other group received placebo. Efficacy was evaluated using change from baseline in Visual Analogue Scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Biochemical and hematological parameters including urine analysis were performed to evaluate the safety of Curene® in OA patients.

Result

Forty-six (46) subjects completed the study. The reduction from baseline in total WOMAC score (also subscale scores) and VAS score resulted in statistically significant difference when compared to placebo. It was also found to be safe and well tolerated as there was no incidence of treatment related AEs.

Conclusion

Curene® results in statistically significant and clinically meaningful reduction in pain, stiffness, and improvement in physical functioning in subjects suffering from knee OA. Curene® also demonstrates excellent safety profile during the study.

Trial Registration

This trial is registered with Clinical Trial Registry, India, CTRI/2017/07/009044, registered on 14th July 2017, http://ctri.nic.in/Clinicaltrials/showallp.php?mid1=19264&EncHid=&userName=ocius%20life%20sciences.

Bioinformatics analysis to identify key genes and pathways influencing synovial inflammation in osteoarthritis

Osteoarthritis (OA) is a chronic arthropathy that occurs in the middle-aged and elderly population. The present study aimed to identify gene signature differences between synovial cells from OA synovial membrane with and without inflammation, and to explain the potential mechanisms involved. The differentially expressed genes (DEGs) between 12 synovial membrane with inflammation and 12 synovial membrane without inflammation from the dataset GSE46750 were identified using the Gene Expression Omnibus 2R. The DEGs were subjected to enrichment analysis, protein-protein interaction (PPI) analysis and module analysis. The analysis results were compared with text-mining results. A total of 174 DEGs were identified. Gene Ontology enrichment results demonstrated that functional molecules encoded by the DEGs primarily had extracellular location, molecular functions predominantly involving ‘chemokine activity’ and ‘cytokine activity’, and were associated with biological processes, including ‘inflammatory response’ and ‘immune response’. The Kyoto Encyclopedia of Genes and Genomes results demonstrated that DEGS may function through pathways associated with ‘rheumatoid arthritis’, ‘chemokine signaling pathway’, ‘complement and coagulation cascades’, ‘TNF signaling pathway’, ‘intestinal immune networks for IgA production’, ‘cytokine-cytokine receptor interaction’, ‘allograft rejection’, ‘Toll-like receptor signaling pathway’ and ‘antigen processing and presentation’. The top 10 hub genes [interleukin (IL)6, IL8, matrix metallopeptidase (MMP)9, colony stimulating factor 1 receptor, FOS proto-oncogene, AP1 transcription factor subunit, insulin-like growth factor 1, TYRO protein tyrosine kinase binding protein, MMP3, cluster of differentiation (CD)14 and CD163] and four gene modules were identified from the PPI network using Cytoscape. In addition, text-mining was used to identify the commonly used drugs and their targets for the treatment of OA. It was initially verified whether the results of the present study were useful for the study of OA treatment targets and pathways. The present study provided insight for the molecular mechanisms of OA synovitis. The hub genes and associated pathways derived from analysis may be targets for OA treatment. IL8 and MMP9, which were validated by text-mining, may be used as molecular targets for the OA treatment, while other hub genes require further validation.

Combinatorial Prg4 and Il-1ra Gene Therapy Protects Against Hyperalgesia and Cartilage Degeneration in Post-Traumatic Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of synovial joints characterized by progressive loss of articular cartilage, subchondral bone remodeling, and intra-articular inflammation with synovitis that results in chronic pain and motor impairment. Despite the economic and health impacts, current medical therapies are targeted at symptomatic relief of OA and fail to alter its progression. Given the complexity of OA pathogenesis, we hypothesized that a combinatorial gene therapy approach, designed to inhibit inflammation with interleukin-1 receptor antagonist (IL-1Ra) while promoting chondroprotection using lubricin (PRG4), would improve preservation of the joint compared to monotherapy alone. Employing two surgical techniques to model mild, moderate and severe posttraumatic OA, we found that combined delivery of helper-dependent adenoviruses (HDVs), expressing IL-1Ra and PRG4, preserved articular cartilage better than either monotherapy in both models as demonstrated by preservation of articular cartilage volume and surface area. This improved protection was associated with increased expression of proanabolic and cartilage matrix genes together with decreased expression of catabolic genes and inflammatory mediators. In addition to improvements in joint tissues, this combinatorial gene therapy prolonged protection against thermal hyperalgesia compared to either monotherapy. Taken together, our results show that a combinatorial strategy is superior to monotherapeutic approaches for treatment of posttraumatic OA.

Novel treatments for osteoarthritis: an update

Osteoarthritis is the most prevalent chronic joint condition worldwide. The principles of osteoarthritis treatment are to alleviate pain and stiffness as well as maintain function, with current consensus guidelines recommending the use of a combination of conservative measures including physical therapy, analgesia, and surgical interventions such as arthroplasty. In recent years, several pharmacological therapies have emerged as potential alternatives. Although a disease-modifying osteoarthritis drug has yet to be identified, promising results have been reported in recent trials especially with serotonin-norepinephrine reuptake inhibitors, IL-1 antagonists, and antibodies to nerve growth factor. The present review aims to summarize and discuss the latest results of novel treatments for osteoarthritis and potential targets for future research.

Exosomes derived from miR-92a-3p-overexpressing human mesenchymal stem cells enhance chondrogenesis and suppress cartilage degradation via targeting WNT5A

Background

WNT5A is known to be involved in the pathogenesis of osteoarthritis. This study investigated the molecular mechanism of exosomal miR-92a-3p and WNT5A in chondrogenesis and cartilage degeneration.

Methods

Exosomal miR-92a-3p expression was assessed in vitro in a human mesenchymal stem cell (MSC) model of chondrogenesis and in normal and OA primary human chondrocytes (PHCs). MSCs and PHCs were treated with exosomes derived from MSC-miR-92a-3p (MSC-miR-92a-3p-Exos) or its antisense inhibitor (MSC-anti-miR-92a-3p-Exos), respectively. Small interfering RNAs (siRNAs) and luciferase reporter assay were used to reveal the molecular role of exosomal miR-92a-3p and WNT5A in chondrogenesis. The protective effect of exosomes in vivo was measured using Safranin-O and Fast Green staining and immunohistochemical staining.

Results

Exosomal miR-92a-3p expression was elevated in the MSC chondrogenic exosome, while it was significantly reduced in the OA chondrocyte-secreted exosome compared with normal cartilage. Treatment with MSC-miR-92a-3p-Exos promoted cartilage proliferation and matrix genes expression in MSCs and PHCs, respectively. In contrast, treatment with MSC-anti-miR-92a-3p-Exos repressed chondrogenic differentiation and reduced cartilage matrix synthesis by enhancing the expression of WNT5A. Luciferase reporter assay demonstrated that miR-92a-3p suppressed the activity of a reporter construct containing the 3’-UTR and inhibited WNT5A expression in both MSCs and PHCs. MSC-miR-92a-3p-Exos inhibit cartilage degradation in the OA mice model.

Conclusions

Our results suggest that exosomal miR-92a-3p regulates cartilage development and homeostasis by directly targeting WNT5A. This indicates that exosomal miR-92a-3p may act as a Wnt inhibitor and exhibits potential as a disease-modifying osteoarthritis drug.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1004-0) contains supplementary material, which is available to authorized users.

ANP32A regulates ATM expression and prevents oxidative stress in cartilage, brain, and bone

Osteoarthritis is the most common joint disorder with increasing global prevalence due to aging of the population. Current therapy is limited to symptom relief, yet there is no cure. Its multifactorial etiology includes oxidative stress and overproduction of reactive oxygen species, but the regulation of these processes in the joint is insufficiently understood. We report that ANP32A protects the cartilage against oxidative stress, preventing osteoarthritis development and disease progression. ANP32A is down-regulated in human and mouse osteoarthritic cartilage. Microarray profiling revealed that ANP32A protects the joint by promoting the expression of ATM, a key regulator of the cellular oxidative defense. Antioxidant treatment reduced the severity of osteoarthritis, osteopenia, and cerebellar ataxia features in Anp32a-deficient mice, revealing that the ANP32A/ATM axis discovered in cartilage is also present in brain and bone. Our findings indicate that modulating ANP32A signaling could help manage oxidative stress in cartilage, brain, and bone with therapeutic implications for osteoarthritis, neurological disease, and osteoporosis.

MicroRNA-128a represses chondrocyte autophagy and exacerbates knee osteoarthritis by disrupting Atg12

Chondrocyte loss is a prominent feature of osteoarthritis (OA). Autophagy is indispensable in maintaining the metabolic activities of cells exposed to deleterious stress. The contribution of microRNA signaling to chondrocyte autophagy in OA development remains elusive. We uncovered an association between poor autophagy and increased miR-128a expressions in articular chondrocytes of patients with end-stage knee OA and in a rat anterior cruciate ligament transection (ACLT) model for OA development. Cartilage matrix degradation and severe OA histopathology was evident upon forced miR-128a expression within the articular compartment. Intra-articular injections with miR-128a antisense oligonucleotide stabilized chondrocyte autophagy and slowed ACLT-mediated articular tissue destruction, including cartilage erosion, synovitis, osteophyte formation, and subchondral plate damage. In vitro, miR-128 signaling hindered Atg12 expression, LC3-II conversion, and autophagic puncta formation through targeting the 3′-untranslated region of Atg12. It increased apoptotic programs, diminishing cartilage formation capacity of articular chondrocytes. Inactivating histone methyltransferase EZH2 reduced methyl histone H3K27 enrichment in the miR-128a promoter and upregulated miR-128a transcription in inflamed chondrocytes. Taken together, miR-128a-induced Atg12 loss repressed chondrocyte autophagy to aggravate OA progression. EZH2 inactivation caused H3K27 hypomethylation to accelerate miR-128a actions. Interruption of miR-128a signaling attenuated chondrocyte dysfunction and delayed OA development. Our data provide new insights into how miR-128a signaling affects chondrocyte survival and articular cartilage anabolism and highlight the potential of miR-128a targeting therapy to alleviate knee OA.

Krogh's principle for musculoskeletal physiology and pathology

August Krogh was a comparative physiologist who used frogs, guinea pigs, cats, dogs, and horses in his research that led to his Nobel Prize on muscle physiology. His idea to choose the most relevant organism to study problems in physiology has become known as Krogh's principle. Indeed, many important discoveries in physiology have been made using naturally occurring animal models. However, the majority of research today utilizes laboratory mouse and rat models to study problems in physiology. This paper discusses how Krogh's principle can be invoked in musculoskeletal research as a complementary approach to using standard laboratory rodent models for solving problems in musculoskeletal physiology. This approach may increase our ability to treat musculoskeletal diseases clinically. For example, it has been noted that progress in osteogenesis imperfecta research has been limited by the absence of a naturally occurring animal model. Several examples of naturally occurring animal models are discussed including osteoarthritis and osteosarcoma in dogs, resistance to disuse induced bone and skeletal muscle loss in mammalian hibernators, and bone phenotypic plasticity in fish lacking osteocytes. Many musculoskeletal diseases (e.g., osteoarthritis) occur naturally in companion animals, which may provide clues on etiology and progression of musculoskeletal diseases and accelerate the development of pharmaceutical therapies for humans.

Intra-articular oxygen-ozone versus hyaluronic acid in knee osteoarthritis: A meta-analysis of randomized controlled trials

OBJECTIVE

Knee osteoarthritis (OA) is a common disease, imposing a great burden through pain and decreased function. Numerous methods have been tested for pain management in knee OA and the optimal method is currently still under debate. We performed a meta-analysis from randomized controlled trials (RCTs) to compare the efficacy and safety of intra-articular hyaluronic acid (HA) and oxygen-ozone in the treatment of knee OA.

METHODS

Electronic databases included PubMed, Embase, web of science and the Cochrane Library. High quality RCTs comparing HA with oxygen-ozone in the treatment of knee OA were selected. We assessed statistical heterogeneity for each RCT with the use of a standard Chi2 test and the I² statistic. Quality assessment was performed by using Cochrane Collaboration's tool. All data were carried out with Stata 14.0 software.

RESULTS

A total of four RCTs including 289 patients were included. The present meta-analysis indicated that there was a significant difference between groups regarding the visual analog scale (VAS) and WOMAC stiffness and function. The improvements in WOMAC pain were similar. No significant difference in adverse events occurrence was observed.

CONCLUSION

Intra-articular injection of HA was associated with a significantly reduction in VAS score at 1st month compared to oxygen-ozone. And there was significant differences in WAMAC stiffness, and function at 6-month follow-up between groups. Based on the current evidence available, more RCTs are needed for further investigation.

Injectable hydrogels: a new paradigm for osteochondral tissue engineering

Osteochondral tissue engineering has become a promising strategy for repairing focal chondral lesions and early osteoarthritis (OA), which account for progressive joint pain and disability in millions of people worldwide. Towards improving osteochondral tissue repair, injectable hydrogels have emerged as promising matrices due to their wider range of properties such as their high water content and porous framework, similarity to the natural extracellular matrix (ECM), ability to encapsulate cells within the matrix and ability to provide biological cues for cellular differentiation. Further, their properties such as those that facilitate minimally invasive deployment or delivery, and their ability to repair geometrically complex irregular defects have been critical for their success. In this review, we provide an overview of innovative approaches to engineer injectable hydrogels towards improved osteochondral tissue repair. Herein, we focus on understanding the biology of osteochondral tissue and osteoarthritis along with the need for injectable hydrogels in osteochondral tissue engineering. Furthermore, we discuss in detail different biomaterials (natural and synthetic) and various advanced fabrication methods being employed for the development of injectable hydrogels in osteochondral repair. In addition, in vitro and in vivo applications of developed injectable hydrogels for osteochondral tissue engineering are also reviewed. Finally, conclusions and future perspectives of using injectable hydrogels in osteochondral tissue engineering are provided.

A novel method to assess subchondral bone formation using [18F]NaF-PET in the evaluation of knee degeneration

PURPOSE

Fluorine-18-sodium fluoride-PET ([F]NaF-PET) facilitates direct assessment of subchondral bone formation to evaluate degeneration in articulating joints. No standards exist for the quantification of joint activity using [F]NaF-PET, and many techniques rely on focal uptake to characterize an entire region of interest. This study proposes a novel method of quantitative global knee analysis to assess regions of expected bone remodeling in the evaluation of knee degeneration.

PATIENTS AND METHODS

The study population consisted of 18 patients with rheumatoid arthritis who underwent [F]NaF-PET/computed tomography imaging. The maximum standardized uptake value (knee SUVmax) in addition to a target-to-background ratio (TBR) that represents global knee activity adjusted for systemic bone formation measured at the lateral femoral neck (global knee TBR) were calculated. A radiologist scored standard radiographs of the knee in nine patients using the Kellgren-Lawrence grading system.

RESULTS

Patients with greater [F]NaF uptake demonstrated greater knee deterioration, which was corroborated by the radiograph findings. Average Kellgren-Lawrence grading was strongly associated with both global knee TBR (Spearman ρ=0.69, P=0.04) and knee SUVmax scores (Spearman ρ=0.93, P=0.0003).

CONCLUSION

Assessment of global activity within the joint is a feasible and clinically useful technique for characterizing disease activity with a single value. Furthermore, a ratio based on systemic bone turnover in a nonarticulating, weight-bearing site adjusts for differences in bone formation related to bodyweight or metabolic bone diseases. We hypothesize that a global knee TBR score may be more sensitive at detecting changes in disease progression, as new spatially distinct lesions with a lower SUV that develop within an region of interest would not be detected by the SUVmax methodology. Longitudinal studies assessing sensitivity with larger patient cohorts are needed to further validate this methodology.

Baicalin Attenuates Joint Pain and Muscle Dysfunction by Inhibiting Muscular Oxidative Stress in an Experimental Osteoarthritis Rat Model

Osteoarthritis (OA) is the most common degenerative joint disease, and causes major pain and disability in adults. It has been reported that muscle weakness and inflammation contribute to osteoarthritis development and progression. Oxidative stress plays important roles in muscle dysfunction and inflammation in osteomyelitis. Baicalin, the major active constituent of the isolated root of Scutellarialateriflora Georgi, has been shown to have anti-oxidative and anti-inflammatory effects. In this study, we evaluated the potential effects of baicalin on osteoarthritis. We established experimental osteoarthritis rat model, applied baicalin to the rats, and then explored the potential protective effect of baicalin on osteoarthritis severity, muscle dysfunction, and oxidative stress. Baicalin alleviated severity of OA in rats. Baicalin application attenuated muscle dysfunction in OA rats by increasing citrate synthase activity, myosin heavy chain IIa expression, and decreasing interleukin 6 production. Baicalin decreased muscular reactive oxygen species generation in OA rats. Baicalin inhibited nuclear factor erythroid-derived 2-like 2 expression in OA rats. Baicalin attenuated osteoarthritis in rat by inhibiting oxidative stress.

Deletion of Axin1 in condylar chondrocytes leads to osteoarthritis-like phenotype in temporomandibular joint via activation of β-catenin and FGF signaling

Osteoarthritis (OA) in the temporomandibular joint (TMJ) is a degenerative disease in the adult, which is characterized by the pathological degeneration of condylar cartilage. Axin1 plays a critical role in the regulation of cartilage development and homeostasis. To determine the role of Axin1 in TMJ tissue at the adult stage, we generated Axin1^Agc1ER mice, in which Axin1 was deleted in aggrecan-expressing chondrocytes at 2 months of age. Histology, histomorphometry, and immunostaining analyses were performed using TMJ tissues harvested from 4- and 6-month-old mice after tamoxifen administration. Total RNA isolated from TMJ cartilage of 6-month-old mice was used for gene expression analysis. Progressive OA-like degeneration was observed in condylar cartilage in Axin1 knockout (KO) mice with loss of surface continuity and the formation of vertical fissures. In addition, reduced alcian blue staining in condylar cartilage was also found in Axin1 KO mice. Immunostaining and reverse transcription quantitative polymerase chain reaction (qRT-PCR) assays revealed disturbed homeostasis in condylar cartilage with increased expressions of MMP13 and Adamts5 and decreased lubricin expression in Axin1-deficient chondrocytes. Less proliferative cells with increased hypertrophic and apoptotic activities were presented in the condylar cartilage of Axin1^Agc1ER KO mice. As a scaffolding protein, the deletion of Axin1 stimulated not only the β-catenin but also the fibroblast growth factor (FGF) signaling via extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) activation. The qRT-PCR results showed an increased expression of Fgfr1 in Axin1 KO cartilage. Overall, the deletion of Axin1 in condylar chondrocytes altered the β-catenin and FGF/ERK1/2 signaling pathways, thus cooperatively contribute to the cartilage degeneration.

Human umbilical cord Wharton's jelly mesenchymal stem cells combined with an acellular cartilage extracellular matrix scaffold improve cartilage repair compared with microfracture in a caprine model

OBJECTIVE

As a novel and promising seed cell, human umbilical cord Wharton's jelly mesenchymal stem cells (hWJMSCs) are widely applied in tissue engineering. However, whether hWJMSCs can better repair and regenerate the articular cartilage in big animals than microfracture (MF, a predominant clinical treatment strategy for damaged cartilage) is unclear. Evaluation of the validity, and safety of hWJMSCs in a caprine model with a full-thickness femoral condyle articular cartilage defect, compared with MF is required.

METHODS

After cultivation and identification, hWJMSCs were seeded in an acellular cartilage extracellular matrix (ACECM)-oriented scaffold to construct cell-scaffold complex. Six goats with full-thickness femoral condyle articular cartilage defects were randomized to MF (microfracture group, MFG) and cell-scaffold complexes (experimental group, EG). At 2 and 4 weeks, joint fluid was used to assess immuno-inflammatory responses. At 6 and 9 months, all goats were euthanized for assessment of morphology, and magnetic resonance imaging (MRI), histology staining, and evaluation of the elasticity modulus and glycosaminoglycan (GAG) contents of the repaired regions.

RESULTS

There were no significant differences between the two groups in immuno-inflammatory parameters. MRI demonstrated higher-quality cartilage and complete subchondral bone at defect sites in the EG at 9 months. Histological staining showed that extracellular cartilage, cartilage lacuna and collagen type II levels were higher in the EG compared to the MFG, while the EG exhibited a higher elasticity modulus.

CONCLUSIONS

The hWJMSCs-ACECM scaffold complex achieved better quality repair and regeneration of hyaline cartilage without cartilage-inducing factor, while retaining the structure and functional integrity of the subchondral bone, compared with MF.

Wnt/β-catenin Signaling in Osteoarthritis and in Other Forms of Arthritis

PURPOSE OF REVIEW

Arthritis defines a large group of diseases primarily affecting the joint. It is the leading cause of pain and disability in adults. Osteoarthritis (OA) affecting the knee or hip is the most common form among over 100 types of arthritis. Other types of arthritis include erosive hand OA, temporomandibular joint (TMJ) OA, facet joint OA, diffuse idiopathic skeletal hyperostosis (DISH), and spondyloarthritis (SpA). However, the specific molecular signals involved in the development and progression of OA and related forms of arthritis remain largely unknown. The canonical wingless/integrated (Wnt)/β-catenin signaling pathway could play a unique role in the pathogenesis of arthritis. In this review article, we will focus on the molecular mechanisms of Wnt/β-catenin signaling in the pathogenesis of OA and other types of arthritis.

RECENT FINDINGS

Emerging evidence demonstrates that Wnts and Wnt-related molecules are involved in arthritis development and progression in human genetic studies and in vitro studies. Also, mouse models have been generated to determine the role of Wnt/β-catenin signaling in the pathogenesis of arthritis. Wnt/β-catenin signaling represents a unique signaling pathway regulating arthritis development and progression, and the molecules in this particular pathway may serve as targets for the therapeutic intervention of arthritis. Mediators and downstream effectors of Wnt/β-catenin signaling are increased in OA as well other forms of arthritis, including DISH and SpA. Through extensive investigations, including pre-clinical studies in transgenic mice and translational and human studies, the Wnt/β-catenin signaling pathway has been proven to play roles in bone and joint pathology by directly affecting bone, cartilage, and synovial tissue; further, these pathologies can be reduced through targeting this pathway. Continued investigation into the distinct molecular signaling of the Wnt/β-catenin pathway will provide additional insights toward the therapeutic intervention in arthritis.

The Involvement of MicroRNAs in Osteoarthritis and Recent Developments: A Narrative Review

Background:

Osteoarthritis (OA) is the most common chronic joint disease and it may progressively cause disability and compromise quality of life. Lately, the role of miRNAs in the pathogenesis of OA has drawn a lot of attention. miRNAs are small, single-stranded, non-coding molecules of RNA which regulate gene expression at post-transcriptional level. The dysregulation of the expression of several miRNAs affects pathways involved in OA pathogenesis.

Objective:

The purpose of this article is to review the literature on the involvement of miRNAs in the pathogenesis of OA and the implications on its diagnosis and treatment.

Materials and Methods:

An extensive electronic literature search was conducted by two researchers from January 2008 to August 2017. Titles and abstracts of papers were screened by the authors for further inclusion in the present work. Finally, full texts of the selected articles were retrieved.

Results:

Abnormally expressed miRNAs enhance the production of cartilage degrading enzymes, inhibit the expression of cartilage matrix components, increase the production of proinflammatory cytokines, facilitate chondrocyte apoptosis, suppress autophagy in chondrocytes and are involved in pain-related pathways. miRNAs are also incorporated in extra-cellular membranous vesicles such as exosomes and participate in the intercellular communication in osteoarthritic joints.

Conclusion:

Ongoing research on miRNAs has potential implications in the diagnosis and treatment of OA. Their different levels in peripheral blood and synovial fluid between OA patients and healthy population makes them candidates for being used as biomarkers of the disease, while targeting miRNAs may be a novel therapeutic strategy in OA.

Hierarchically structured seamless silk scaffolds for osteochondral interface tissue engineering

The osteochondral healthcare market is driven by the increasing demand for affordable and biomimetic scaffolds. To meet this demand, silk fibroin (SF) from Bombyx mori and Antheraea assamensis is used to fabricate a biphasic scaffold, with fiber-free and fiber-reinforced phases, stimulating cartilage and bone revival. The fabrication is a facile reproducible process using single polymer (SF), for both phases, designed in a continuous and integrated manner. Physicochemical and mechanical scaffold characterization, display interconnected pores with differential swelling and tunable degradation. The compressive modulus values, extend to 40 kPa and 25%, for tensile strain, at elongation. The scaffold support, for growth and proliferation of chondrocytes and osteoblasts, for respective cartilage and bone regeneration, is verified from in vitro assessment. Up-regulation of alkaline phosphatase (ALP) activity, extracellular matrix secretion and gene expression are significant; with acceptable in vitro immune response. Upon implantation in rabbit osteochondral defects for 8 weeks, the histological and micro-CT examinations show biphasic scaffolds significantly enhance regeneration of cartilage and subchondral bone tissues, as compared to monophasic scaffolds. The regenerated bone mineral density (BMD) ranges from 600-700 mg hydroxyapatite (HA) per cm³. The results, therefore, showcase the critically positive characteristics of in vitro ECM deposition, and in vivo regeneration of osteochondral tissue by this hierarchically structured biphasic scaffold.

Taurine protects against knee osteoarthritis development in experimental rat models

BACKGROUND

Osteoarthritis (OA) is one of the complex diseases that affect a large population of the world. The aim of the current study was to explore the roles of taurine in OA rat models, and discover the related mechanisms.

METHODS

OA rat models were established by anterior cruciate ligament transection (ACLT) plus medial meniscus resection (MMx) surgery on the right knees. Secondary mechanical allodynia, weight-bearing alterations and knee joint width were evaluated before surgery and every two weeks after surgery. At 14weeks, histopathological analysis was conducted on the knee joint cartilage. Protein amount of MMP-3 and CHOP was evaluated by western blot.

RESULTS

Taurine injection after surgery significantly relieved the symptoms of OA in rat models in a dose-dependent and time-dependent manner, as shown by alleviation of secondary mechanical allodynia, decrease in hind limb weight-bearing alterations, and inhibited knee swelling. Moreover, histopathological analysis showed that taurine inhibited matrix loss and cartilage degeneration in a dose-dependent manner. Taurine administration strikingly suppressed the expression of matrix metalloproteinase-3 (MMP-3) and CHOP.

CONCLUSION

These results indicated that taurine administration exhibited protective effects by inhibiting MMP-3 and CHOP expression, and subsequently alleviated the OA symptoms in experimental rat models.

Lenalidomide regulates osteocytes fate and related osteoclastogenesis via IL-1β/NF-κB/RANKL signaling

Osteolytic diseases are closely associated with osteocyte fate, indicating a more efficient and crucial role of osteocyte-targeting strategy in inhibiting osteoclastogenesis. Here, we investigated the effects of lenalidomide (Lena) on osteocyte fate in order to regulate osteoclastogenesis via effective cascade-controlling response. Our data revealed that lenalidomide treatment notably rescued IL-1β induced loss of osteocyte viability by inhibiting osteocyte apoptosis with decreased osteoclast-related factors, RANKL and Sclerostin, as demonstrated by the restricted osteoclast formation and reduced bone resorption. Additionally, iTRAQ assay revealed that IL-1β induced activation of NF-κB inhibitor α/β were remarkably downregulated by lenalidomide, showing that lenalidomide impaired NF-κB signaling in osteocytes for inhibiting the expression of osteoclast specific genes in osteoclasts, which was further confirmed by KEGG pathway analysis and Western blot. More interestingly, the in vivo analysis of osteocyte apoptosis and osteoclastogenesis in osteoarthritis mice model indicated a role of lenalidomide in the regulation of osteocyte fate and the consequent inhibition of RANKL-induced osteoclastogenesis. Together, these results suggest that lenalidomide regulates osteocyte fate by attenuating IL-1β/NF-κB signaling, thereby inhibiting RANKL expression for the attenuated osteoclastogenesis both in vitro and vivo, indicating a more efficient remedy among future anti-osteoclastogenesis approaches.

An Emerging Role for Circular RNAs in Osteoarthritis

Circular RNAs (circRNAs) are currently classed as non-coding RNAs that, unlike the better known canonical linear RNAs, form a covalently closed continuous loop without 5' or 3' polarities. With the development of high throughput sequencing technology, a large number of circRNAs have been discovered in many species. More importantly, growing evidence suggests that circRNAs are abundant, evolutionally conserved, and relatively stable in cells and tissues. Strikingly, recent studies have discovered that circRNAs can serve as microRNA sponges, interact with RNA-binding protein, and regulate gene transcription, as well as protein translation. Osteoarthritis (OA) is the most common chronic degenerative joint disease. CircRNAs are differentially expressed in OA cartilage. Moreover, some circRNAs are involved in multiple pathological processes during OA, mainly extracellular matrix degradation, inflammation, and apoptosis. In this review, we briefly delineate the biogenesis, characteristics, and biofunctions of circRNAs, and then, focus on the role of circRNAs in the occurrence and progression OA.

CCL17 blockade as a therapy for osteoarthritis pain and disease

Background

Granulocyte macrophage-colony stimulating factor (GM-CSF) has been implicated in the pathogenesis of a number of inflammatory diseases and in osteoarthritis (OA). We identified previously a new GM-CSF→Jmjd3→interferon regulatory factor 4 (IRF4)→chemokine (c-c motif) ligand 17 (CCL17) pathway, which is important for the development of inflammatory arthritis pain and disease. Tumour necrosis factor (TNF) can also be linked with this pathway. Here we investigated the involvement of the pathway in OA pain and disease development using the GM-CSF-dependent collagenase-induced OA (CiOA) model.

Methods

CiOA was induced in C57BL/6 wild-type (WT), Irf4^−/−, Ccl17^E/E, Ccr4^−/−, Tnf^−/− and GM-CSF^−/− mice. Additionally, therapeutic targeting of CCL17, Jmjd3 and cyclooxygenase 2 (COX-2) was evaluated. Development of pain (assessment of weight distribution) and OA disease (histologic scoring of synovitis, cartilage destruction and osteophyte size) were assessed. Synovial joint cells, including neutrophils, macrophages, fibroblasts and endothelial cells, were isolated (cell sorting) and gene expression analyzed (quantitative PCR).

Results

Studies in the gene-deficient mice indicated that IRF4, CCL17 and the CCL17 receptor, CCR4, but not TNF, were required for CiOA pain and optimal cartilage destruction and osteophyte size. Therapeutic neutralization of CCL17 and Jmjd3 ameliorated both pain and disease, whereas the COX-2 inhibitor only ameliorated pain. In the synovium Ccl17 mRNA was expressed only in the macrophages in a GM-CSF-dependent and IRF4-dependent manner.

Conclusions

The GM-CSF→Jmjd3→IRF4→CCL17 pathway is important for the development of CiOA, with CCL17 thus being a potential therapeutic target for the treatment of both OA pain and disease.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1560-9) contains supplementary material, which is available to authorized users.

Osteoarthritis and Ageing

Ageing is a complex process of accumulation of molecular, cellular, and organ damage, leading to loss of function and increased vulnerability to disease and death, the rate and extent of which varies among individuals. Osteoarthritis (OA) is not only the most common joint disease, but is also one of the major causes of disability in people aged >65 years and is accompanied by comorbid conditions, increased mortality, and decreased quality of life. One of the major risk factors for OA is ageing. However, OA itself may be involved in the biological ageing process. This is likely to be in part a direct involvement, by contributing levels of systemic inflammation and sharing molecular pathways with biological ageing, such as mitochondrial damage leading to cell senescence. Although OA is not considered an inflammatory form of arthritis, there is evidence of subclinical low-grade inflammation in the whole joint and inflammatory processes play a key role in the disease pathogenesis. For instance, there is synovial inflammation (e.g., following injury), mechanically derived inflammation present due to biomechanical overloading of a joint, and systemic inflammation resulting from obesity. Systemic inflammation is often associated with frailty, and having a high concentration of inflammatory markers is predictive of incident frailty, some of which are known to increase with age and correlate with pain. In addition, OA may also contribute indirectly to biological ageing via the disability and pain resulting from it. Further research into the exact process linking OA and biological ageing, including frailty, is needed.

Polydatin inhibits the IL-1β-induced inflammatory response in human osteoarthritic chondrocytes by activating the Nrf2 signaling pathway and ameliorates murine osteoarthritis

Osteoarthritis (OA), which is characterized by progressive degradation of the articular cartilage, is the most prevalent form of human arthritis. Accumulating evidence has shown that polydatin (PD) exerts special biological functions in a variety of diseases. However, whether it protects against OA development has remained unknown. Here, we investigated the anti-inflammatory and chondroprotective effects of PD on interleukin (IL)-1β-induced human osteoarthritic chondrocytes and in the surgical destabilization of medial meniscus mouse (DMM) OA models. In vitro, PD treatment completely suppressed the over-production of pro-inflammatory mediators, including prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), nitric oxide (NO), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and IL-6 in IL-1β-induced human OA chondrocytes. Moreover, PD exerted a suppressive effect on the expression of matrix-degrading proteases, including matrix metalloproteinase 13 (MMP13) and thrombospondin motifs 5 (ADAMTS-5), which leads to the degradation of the extracellular matrix (ECM). Meanwhile, specific inhibition of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) level by short-interfering RNA (siRNA) strongly reversed the anti-inflammatory and chondroprotective effects of PD in human OA chondrocytes. The protective effects of PD were also observed in vivo. In conclusion, our studies demonstrate that PD holds novel therapeutic potential for the development of OA.

Isoliquiritigenin Inhibits IL-1β-Induced Production of Matrix Metalloproteinase in Articular Chondrocytes

Osteoarthritis (OA) is a major joint disease in which inflammatory cytokine interleukin-1β (IL-1β) and matrix metalloproteinases (MMPs) play a pivotal role. Isoliquiritigenin has been reported to have anti-inflammation activity. In this study, the effect of isoliquiritigenin on IL-1β-induced production of matrix metalloproteinase and nuclear factor κB (NF-κB) activation was analyzed. We treated primary cultured articular chondrocytes with isoliquiritigenin and the expressions of MMPs were analyzed on mRNA and protein level. The phosphorylation of IκBa and p65 was analyzed to detect NF-κB activation. We also used in vivo model by treating mice with isoliquiritigenin and detecting the level of MMPs. IL-1β induced NF-κB activation and MMP-1, MMP-3, MMP-9, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5 production on chondrocytes. A 10-μM isoliquiritigenin treatment significantly inhibited IL-1β-induced NF-κB activation and these MMPs production on chondrocytes. Injecting isoliquiritigenin into rat knee joint also inhibited IL-1β-induced NF-κB activation and MMPs production in articular cartilage. Isoliquiritigenin treatment inhibited IL-1β-induced MMPs production and NF-κB activation both in vitro and in vivo, suggesting a potential therapeutic role of isoliquiritigenin to treat osteoarthritis.

Inhibition of Wnt/β-catenin signaling ameliorates osteoarthritis in a murine model of experimental osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease involving both cartilage and synovium. The canonical Wnt/β-catenin pathway, which is activated in OA, is emerging as an important regulator of tissue repair and fibrosis. This study seeks to examine Wnt pathway effects on synovial fibroblasts and articular chondrocytes as well as the therapeutic effects of Wnt inhibition on OA disease severity. Mice underwent destabilization of the medial meniscus surgery and were treated by intra-articular injection with XAV-939, a small-molecule inhibitor of Wnt/β-catenin signaling. Wnt/β-catenin signaling was highly activated in murine synovial fibroblasts as well as in OA-derived human synovial fibroblasts. XAV-939 ameliorated OA severity associated with reduced cartilage degeneration and synovitis in vivo. Wnt inhibition using mechanistically distinct small-molecule inhibitors, XAV-939 and C113, attenuated the proliferation and type I collagen synthesis in synovial fibroblasts in vitro but did not affect human OA-derived chondrocyte proliferation. However, Wnt modulation increased COL2A1 and PRG4 transcripts, which are downregulated in chondrocytes in OA. In conclusion, therapeutic Wnt inhibition reduced disease severity in a model of traumatic OA via promoting anticatabolic effects on chondrocytes and antifibrotic effects on synovial fibroblasts and may be a promising class of drugs for the treatment of OA.

Cell type-specific effects of Notch signaling activation on intervertebral discs: Implications for intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is the major cause of back pain. Notch signaling is activated in annulus fibrosus (AF) and nucleus pulposus (NP) tissues of degenerated IVDs, and induced by IL1-β and TNF-α in NP cells. However, the role of Notch activatin in the pathogenesis of IVD degeneration is largely unknown. In this study, we overexpressed the Notch1 intracellular domain (NICD1) in AF, NP, and chondrogenic ATDC5 cells via adenoviruses. Overexpression of NICD1 activated transcription of Notch signaling target genes in AF, NP, and ATDC5 cells, and caused cell type-specific effects on expression of matrix anabolic and catabolic genes. Activation of Notch signaling promoted expression of matrix catabolic genes and inhibited expression of matrix anabolic genes in both AF and ATDC5 cells, whereas its activation suppressed expression of matrix catabolic genes (including Mmp3, Mmp13, Adamts4, and Adamts5) and attenuated TNF-α and inflammatory macrophage-induced Mmp13 expression in NP cells. Consistently, sustained activation of Notch1 signaling in postnatal IVDs in mice severely disrupted growth plate and endplate cartilage tissues, but did not overly affect NP tissues. Together, these data indicated that activation of Notch signaling exerted differential and cell type-specific effects in intervertebral discs, and specific Notch signaling regulation may be considered during the treatment of IVD degeneration.

Modified Sauve-Kapandji Procedure for Patients with Old Fractures of the Distal Radius

Objective

To evaluate the clinical and radiographic outcomes of a modified Sauve-Kapandji procedure for patients with old fractures in the distal radius.

Methods

Fifteen patients (10 male and 5 female patients with an average age of 40 years old) were treated by the modified Sauve-Kapandji procedure from January 2014 to April 2016. All patients had undergone at least one previous operation on the involved wrist, and they were still suffering from pain and functional limitations at the time of admission. The postoperative follow-up period was 12-26 months and the average was 20 months. Functional assessment was made at the last follow-up. All patients were evaluated according a Modified Mayo Wrist Score system.

Results

Of the fifteen patients with posttraumatic arthritis, thirteen had excellent results, two had good results, and one had fair results. There were no major complications.

Conclusions

The modified Sauve-Kapandji procedure is a safe and effective surgical alternative for intractable disorders of the distal radioulnar joint and can be recommended as a salvage procedure when previous treatments fail.

Calcium-phosphate complex increased during subchondral bone remodeling affects earlystage osteoarthritis

An activation of osteoclasts and subchondral bone remodeling is a major histologic feature of early-stage osteoarthritis (OA), which can be accompanied by an increase of calcium (Ca) and phosphate (Pi) level in the subchondral milieu. Considering articular cartilage gets most of nutrition from subchondral bone by diffusion, these micro-environmental changes in subchondral bone can affect the physiology of articular chondrocytes. Here, we have shown that Ca is increased and co-localized with Pi in articular cartilage of early-stage OA. The Ca-Pi complex increased the production of MMP-3 and MMP-13 in the hypertrophic chondrocytes, which was dependent on nuclear factor-kappa B (NF-kB), p38 and extracellular signal-regulated kinase (Erk) 1/2 mitogen-activated protein (MAP) kinase and Signal transducer and activator of transcription 3 (STAT3) signaling. The Ca-Pi complexes increased the expression of endocytosis markers, and the inhibition of the formation of the Ca-Pi complex ameliorated the Ca-Pi complex-mediated increases of MMPs expression in hypertrophic chondrocytes. Our data provide insight regarding the Ca-Pi complex as a potential catabolic mediator in the subchondral milieu and support the pathogenic role of subchondral bone in the early stages of cartilage degeneration.

Osteoarthritis: Trauma vs Disease

Osteoarthritis (OA) is the most prevalent joint disease characterized by pain and degenerative lesions of the cartilage, subchondral bone, and other joint tissues. The causes of OA remain incompletely understood. Over the years, it has become recognized that OA is a multifactorial disease. In particular, aging and trauma are the main risk factors identified for the development of OA; however, other factors such as genetic predisposition, obesity, inflammation, gender and hormones, or metabolic syndrome contribute to OA development and lead to a more severe outcome. While this disease mainly affects people older than 60 years, OA developed after joint trauma affects all range ages and has a particular impact on young individuals and people who have highest levels of physical activity such as athletes. Traumatic injury to the joint often results in joint instability or intra-articular fractures which lead to posttraumatic osteoarthritis (PTOA). In response to injury, several molecular mechanisms are activated, increasing the production and activation of different factors that contribute to the progression of OA.In this chapter, we have focused on the interactions and contribution of the multiple factors involved in joint destruction and progression of OA. In addition, we overview the main changes and molecular mechanisms related to OA pathogenesis.

Mesenchymal Stromal/stem Cell-derived Extracellular Vesicles Promote Human Cartilage Regeneration In Vitro

Osteoarthritis (OA) is a rheumatic disease leading to chronic pain and disability with no effective treatment available. Recently, allogeneic human mesenchymal stromal/stem cells (MSC) entered clinical trials as a novel therapy for OA. Increasing evidence suggests that therapeutic efficacy of MSC depends on paracrine signalling. Here we investigated the role of extracellular vesicles (EVs) secreted by human bone marrow derived MSC (BMMSC) in human OA cartilage repair.

Methods: To test the effect of BMMSC-EVs on OA cartilage inflammation, TNF-alpha-stimulated OA chondrocyte monolayer cultures were treated with BMMSC-EVs and pro-inflammatory gene expression was measured by qRT-PCR after 48 h. To assess the impact of BMMSC-EVs on cartilage regeneration, BMMSC-EVs were added to the regeneration cultures of human OA chondrocytes, which were analyzed after 4 weeks for glycosaminoglycan content by 1,9-dimethylmethylene blue (DMMB) assay. Furthermore, paraffin sections of the regenerated tissue were stained for proteoglycans (safranin-O) and type II collagen (immunostaining).

Results: We show that BMMSC-EVs inhibit the adverse effects of inflammatory mediators on cartilage homeostasis. When co-cultured with OA chondrocytes, BMMSC-EVs abrogated the TNF-alpha-mediated upregulation of COX2 and pro-inflammatory interleukins and inhibited TNF-alpha-induced collagenase activity. BMMSC-EVs also promoted cartilage regeneration in vitro. Addition of BMMSC-EVs to cultures of chondrocytes isolated from OA patients stimulated production of proteoglycans and type II collagen by these cells.

Conclusion: Our data demonstrate that BMMSC-EVs can be important mediators of cartilage repair and hold great promise as a novel therapeutic for cartilage regeneration and osteoarthritis.

Immune Contributions to Osteoarthritis

PURPOSE OF THE REVIEW

Mounting evidence supports a role of low-grade inflammation in the pathophysiology of osteoarthritis (OA). We review and discuss the role of synovitis, complement activation, cytokines, and immune cell population in OA.

RECENT FINDINGS

Using newer imaging modalities, synovitis is found in the majority of knees with OA. Complement activation and pro-inflammatory cytokines play a significant role in the development of cartilage destruction and synovitis. Immune cell infiltration of OA synovial tissue by sub-populations of T cells and activated macrophages correlates with OA disease progression and pain. The innate and acquired immune system plays a key role in the low-grade inflammation found associated with OA. Targets of these pathways my hold promise for future disease-modifying osteoarthritis drugs (DMOADs).

Role of CD44 in Regulating TLR2 Activation of Human Macrophages and Downstream Expression of Proinflammatory Cytokines

Osteoarthritis (OA) is a low-grade chronic inflammatory joint disease. Innate immunity contributes to OA progression, mediated by TLR2 and TLR4. We evaluated the role of cluster determinant 44 (CD44), a transmembrane glycoprotein, in regulating TLR2-linked macrophage activation and resultant proinflammatory responses. TLR2 stimulation was performed on differentiated THP-1 macrophages in the presence or absence of a CD44-specific Ab or hyaluronan (HA). NF-κB nuclear translocation, IL-1 β and TNF-α gene expression, and protein concentrations were determined. Anti-CD44 Ab and HA treatments reduced NF-κB translocation, IL-1β and TNF-α expression, and production (p < 0.001). Inhibition of proinflammatory response in macrophages by HA was mediated by CD44. Protein phosphatase 2A mediated the reduction in NF-κB translocation by HA. CD44 knockdown reduced NF-κB nuclear translocation and downstream IL-1β and TNF-α protein production following TLR2 receptor stimulation (p < 0.001). CD44^+/+ murine bone marrow-derived macrophages produced higher TNF-α compared with CD44^-/- macrophages following TLR2 stimulation (p < 0.01). HA dose-dependently inhibited TLR2-induced TNF-α production by murine bone marrow-derived macrophages (p < 0.001). OA synovial fluids (SF) stimulated TLR2 and TLR4 receptors and induced NF-κB translocation in THP-1 macrophages. Anti-CD44 Ab treatment significantly reduced macrophage activation by OA SF (p < 0.01). CD44 regulated TLR2 responses in human macrophages, whereby a reduction in CD44 levels or engagement of CD44 by its ligand (HA) or a CD44-specific Ab reduced NF-κB translocation and downstream proinflammatory cytokine production. A CD44-specific Ab reduced macrophage activation by OA SF, and CD44 is a potentially novel target in OA treatment.

Gastrodin reduces IL-1β-induced apoptosis, inflammation, and matrix catabolism in osteoarthritis chondrocytes and attenuates rat cartilage degeneration in vivo

Therapeutics for osteoarthritis (OA) are intended to restore chondrocyte function and inhibit cell apoptosis. Previous studies have shown that gastrodin had anti-apoptotic and anti- inflammatory effects. However, little is known about whether gastrodin has protective effects against the processes of OA. We studied the potential effects of gastrodin on chondrocytes and the underlying mechanisms. Our results showed that gastrodin could prevent chondrocyte apoptosis induced by IL-1β. Additionally, gastrodin suppressed the nuclear factor kappa B (NF-κB) pathway, decreased the release of inflammatory mediators (IL-6, TNF-α), and reduced matrix catabolism in IL-1β-treated chondrocytes. Furthermore, gastrodin ameliorated rat cartilage degeneration in an OA model of knee joints in vivo, suggesting its potential as a candidate therapeutic for OA.

Inter-individual gene variants associated with trabecular bone plasticity: A step forward in the personal genomics of degenerative bone disease

Continuing tissue destruction in osteoarthrosis is maintained by molecular pathways related to an unbalanced chondrocyte metabolism, the loss of reactive oxygen species (ROS) homeostasis, increase catabolism in a degraded matrix and the limited response to growth factors due to cell aging. Rare deleterious gene variants driving relevant molecular pathways may play a key role in the pathogenesis and genetic control of common diseases and may also influence the common gene variants observed in GWAS. We use molecular profiling technologies based on massive sequencing of genes to interrogate clinical samples for a variety of molecules involved in the pathogenesis pathways of OA and also to derive new insights for drug targeting discovery at an early stage of the disease. By whole-exome sequencing performed in OA patients with extreme phenotypes and in non-related individuals without clinical evidence of OA, the most predominant of the rare gene variants found were non-synonymous single-nucleotide variants (SNV) from exonic DNA regions and with missense functional effects predicting a moderate impact on protein function. A total of 629, 577, and 639 gene variants for the TPF, COA, and ANHNF patients, respectively, were found not to be shared with the 20 non-disease-related individuals. After subtraction of the 306 variants shared among the OA patients, we obtained the individual profiles of 323, 271, and 333 gene variants, for the TPF, COA, and ANHNF patients, respectively. After filtering by the bioinformatics, genetic, and biological criteria established to assess the clinical consequences, comparative analysis of trio sequences using integrative genome visualization tool clearly demonstrate the differences between patients. Analysis of the collagen gene variants identified 78, 20, and 43 genetic collagen variants for the three extreme phenotypes. Rare gene variants encoding for proteins that are less abundant in the trabecular bone matrix, together with those responsible for the control and regulation of bone turnover and plasticity of subchondral trabecular bone, play important roles in OA and help to define the clinical phenotype.

Mesenchymal Stem Cells for Cartilage Regeneration of TMJ Osteoarthritis

Temporomandibular joint osteoarthritis (TMJ OA) is a degenerative disease, characterized by progressive cartilage degradation, subchondral bone remodeling, synovitis, and chronic pain. Due to the limited self-healing capacity in condylar cartilage, traditional clinical treatments have limited symptom-modifying and structure-modifying effects to restore impaired cartilage as well as other TMJ tissues. In recent years, stem cell-based therapy has raised much attention as an alternative approach towards tissue repair and regeneration. Mesenchymal stem cells (MSCs), derived from the bone marrow, synovium, and even umbilical cord, play a role as seed cells for the cartilage regeneration of TMJ OA. MSCs possess multilineage differentiation potential, including chondrogenic differentiation as well as osteogenic differentiation. In addition, the trophic modulations of MSCs exert anti-inflammatory and immunomodulatory effects under aberrant conditions. Furthermore, MSCs combined with appropriate scaffolds can form cartilaginous or even osseous compartments to repair damaged tissue and impaired function of TMJ. In this review, we will briefly discuss the pathogenesis of cartilage degeneration in TMJ OA and emphasize the potential sources of MSCs and novel approaches for the cartilage regeneration of TMJ OA, particularly focusing on the MSC-based therapy and tissue engineering.

Lubricin binds cartilage proteins, cartilage oligomeric matrix protein, fibronectin and collagen II at the cartilage surface

Lubricin, a heavily O-glycosylated protein, is essential for boundary lubrication of articular cartilage. Strong surface adherence of lubricin is required given the extreme force it must withstand. Disulfide bound complexes of lubricin and cartilage oligomeric matrix protein (COMP) have recently been identified in arthritic synovial fluid suggesting they may be lost from the cartilage surface in osteoarthritis and inflammatory arthritis. This investigation was undertaken to localise COMP-lubricin complexes within cartilage and investigate if other cartilage proteins are involved in anchoring lubricin to the joint. Immunohistochemical analysis of human cartilage biopsies showed lubricin and COMP co-localise to the cartilage surface. COMP knockout mice, however, presented with a lubricin layer on the articular cartilage leading to the further investigation of additional lubricin binding mechanisms. Proximity ligation assays (PLA) on human cartilage biopsies was used to localise additional lubricin binding partners and demonstrated that lubricin bound COMP, but also fibronectin and collagen II on the cartilage surface. Fibronectin and collagen II binding to lubricin was confirmed and characterised by solid phase binding assays with recombinant lubricin fragments. Overall, COMP, fibronectin and collagen II bind lubricin, exposed on the articular cartilage surface suggesting they may be involved in maintaining essential boundary lubrication.

Yougui Pills Attenuate Cartilage Degeneration via Activation of TGF-β/Smad Signaling in Chondrocyte of Osteoarthritic Mouse Model

Yougui pills (YGPs) have been used for centuries in the treatment of Chinese patients with Kidney-Yang Deficiency Syndrome. Despite the fact that the efficiency of YGPs on treating osteoarthritis has been verified in clinic, the underlying mechanisms are not totally understood. The present study observes the therapeutic role of YGPs and mechanisms underlying its chondroprotective action in osteoarthritic cartilage. To evaluate the chondroprotective effects of YGPs, we examined the impact of orally administered YGPs in a model of destabilization of the medial meniscus (DMM). Male C57BL/6J mice were provided a daily treatment of YGPs and a DMM surgery was performed on the right knee. At 12 weeks post-surgery, the joints were harvested for tissue analyses, including histomorphometry, OARSI scoring, micro-CT and immunohistochemistry for COL-2, MMP-13 and pSMAD-2. We also performed the relative experiments mentioned above in mice with Tgfbr2 conditional knockout (TGF-βRII^Col2ER mice) in articular cartilage. To evaluate the safety of YGPs, hematology was determined in each group. Amelioration of cartilage degradation was observed in the YGPs group, with increases in cartilage area and thickness, proteoglycan matrix, and decreases in OARSI score at 12 weeks post surgery. In addition, reduced BV/TV and Tb. Th, and elevated Tb. Sp were observed in DMM-induced mice followed by YGPs treatment. Moreover, the preservation of cartilage correlated with reduced MMP-13, and elevated COL-2 and pSMAD-2 protein expressional levels were also revealed in DMM-induced mice treated with YGPs. Similarly, TGF-βRII^Col2ER mice exhibited significant OA-like phenotype. However, no significant difference in cartilage structure was observed in TGF-βRII^Col2ER mice after YGPs treatment. Interestingly, no obvious adverse effects were observed in mice from each group based on the hematologic analyses. These findings suggested that YGPs could inhibit cartilage degradation through enhancing TGF-β/Smad signaling activation, and be considered a good option for the treatment of osteoarthritis.

MicroRNA Profiling in Cartilage Ageing

Osteoarthritis (OA) is the most common age-related joint disorder in man. MicroRNAs (miRNA), a class of small noncoding RNAs, are potential therapeutic targets for regulating molecular mechanisms in both disease and ageing. Whilst there is an increasing amount of research on the roles of miRNAs in ageing, there has been scant research on age-related changes in miRNA in a cartilage. We undertook a microarray study on young and old human cartilages. Findings were validated in an independent cohort. Contrasts between these samples identified twenty differentially expressed miRNAs in a cartilage from old donors, derived from an OA environment which clustered based on OA severity. We identified a number of recognised and novel miRNAs changing in cartilage ageing and OA including miR-126: a potential new candidate with a role in OA pathogenesis. These analyses represent important candidates that have the potential as cartilage ageing and OA biomarkers and therapeutic targets.

An overview of the role of lipid peroxidation-derived 4-hydroxynonenal in osteoarthritis

BACKGROUND

Over the years, many theories have been proposed and examined to better explain the etiology and development of osteoarthritis (OA). The characteristics of joint destruction are one of the most important aspects in disease progression. Therefore, investigating different factors and signaling pathways involved in the alteration of extracellular matrix (ECM) turnover, and the subsequent catabolic damage to cartilage holds chief importance in understanding OA development. Among these factors, reactive oxygen species (ROS) have been at the forefront of the physiological and pathophysiological OA investigation.

FINDINGS

In the last decades, research studies provided an enormous volume of data supporting the involvement of ROS in OA. Most interestingly, published data regarding the effect of exogenous antioxidant therapy in OA lack conclusive results from clinical trials to back up in vitro data. Accordingly, it is rational to suggest that there are other reactive species in OA that are not taken into account. Thus, our present review is focused on our current understanding of the involvement of lipid peroxidation-derived 4-hydroxynonenal (HNE) in OA.

CONCLUSION

Our findings, like those in the literature, illustrate the central role played by HNE in the regulation of a number of factors involved in joint homeostasis. HNE could thus be considered as an attractive therapeutic target in OA.