The role of synovitis in osteoarthritis

Unraveling the molecular landscape of osteoarthritis: A comprehensive review focused on the role of non-coding RNAs

Osteoarthritis (OA) poses a significant global health challenge, with its prevalence anticipated to increase in the coming years. This review delves into the emerging molecular biomarkers in OA pathology, focusing on the roles of various molecules such as metabolites, noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Advances in omics technologies have transformed biomarker identification, enabling comprehensive analyses of the complex pathways involved in OA pathogenesis. Notably, ncRNAs, especially miRNAs and lncRNAs, exhibit dysregulated expression patterns in OA, presenting promising opportunities for diagnosis and therapy. Additionally, the intricate interplay between epigenetic modifications and OA progression highlights the regulatory role of epigenetics in gene expression dynamics. Genome-wide association studies have pinpointed key genes undergoing epigenetic changes, providing insights into the inflammatory processes and chondrocyte hypertrophy typical of OA. Understanding the molecular landscape of OA, including biomarkers and epigenetic mechanisms, holds significant potential for developing innovative diagnostic tools and therapeutic strategies for OA management.

Role of crosstalk between synovial cells and chondrocytes in osteoarthritis (Review)

Osteoarthritis (OA) is a low-grade, nonspecific inflammatory disease that affects the entire joint. This condition is characterized by synovitis, cartilage erosion, subchondral bone defects, and subpatellar fat pad damage. There is mounting evidence demonstrating the significance of crosstalk between synovitis and cartilage destruction in the development of OA. To comprehensively explore the phenotypic alterations of synovitis and cartilage destruction, it is important to elucidate the crosstalk mechanisms between chondrocytes and synovial cells. Furthermore, the updated iteration of single-cell sequencing technology reveals the interaction between chondrocyte and synovial cells. In the present review, the histological and pathological alterations between cartilage and synovium during OA progression are described, and the mode of interaction and molecular mechanisms between synovial cells and chondrocytes in OA, both of which affect the OA process mainly by altering the inflammatory environment and cellular state, are elucidated. Finally, the current OA therapeutic approaches are summarized and emerging therapeutic targets are reviewed in an attempt to provide potential insights into OA treatment.

1,25(OH)2D3 and its analogue calcipotriol inhibit the migration of human synovial and mesenchymal stromal cells in a wound healing model - A comparison with glucocorticoids

Vitamin D analogue calcipotriol is currently used in the local treatment of psoriasis. However, it also has antiproliferative and anti-inflammatory effects in the cells of the joint - suggesting a possible benefit in local treatment of arthritis. In this study, calcipotriol was studied in different in vitro methods to find out its effect on synovial and mesenchymal stromal cells. Primary human cell lines of osteoarthritis or rheumatoid arthritis patients (five mesenchymal stromal cells, MSC, and four synovial stromal cells, SSC) were cultured to study migration and proliferation of the cells in a wound healing model. The media was supplemented with calcipotriol, 1,25(OH)2D3, dexamethasone, betamethasone, methylprednisolone or control solution in 1-100 nM concentrations. To see possible toxic effects of calcipotriol, concentrations up to 10 µM in SSCs and MSCs were studied in apoptosis and necrosis assays in four cell lines. Calcipotriol and 1,25(OH)2D3, as well as the three glucocorticoids, reduced the migration of both SSCs and MSCs. In SSCs, the effect of calcipotriol and 1,25(OH)2D3 was at least as effective as with glucocorticoids, while with MSCs, the glucocorticoids were stronger inhibitors of migration. The antimigratory of calcipotriol and 1,25(OH)2D3 was consistently maintained in 10 µM and 1 µM. Calcipotriol was not toxic to MSCs and SSCs up to concentrations of 10 µM. Calcipotriol, as well as 1,25(OH)2D3, exerts antimigratory and antiproliferative effects on human SSCs and MSCs of the joint. These effects are not caused by apoptosis or necrosis. Both calcipotriol and 1,25(OH)2D3 have similar effects as glucocorticoids without apparent toxicity, suggesting that calcipotriol might be an eligible candidate to the local treatment of arthritis with a broad therapeutic window.

Extracellular vesicles in the treatment and prevention of osteoarthritis: can horses help us translate this therapy to humans?

Osteoarthritis (OA) is a common joint disease affecting humans and horses, resulting in significant morbidity, financial expense, and loss of athletic use. While the pathogenesis is incompletely understood, inflammation is considered crucial in the development and progression of the disease. Mesenchymal stromal cells (MSCs) have received increasing scientific attention for their anti-inflammatory, immunomodulatory, and pro-regenerative effects. However, there are concerns about their ability to become a commercially available therapeutic. Extracellular vesicles (EVs) are now recognized to play a crucial role in the therapeutic efficacy observed with MSCs and offer a potentially novel cell-free therapeutic that may negate many of the concerns with MSCs. There is evidence that EVs have profound anti-inflammatory, immunomodulatory, and pro-regenerative effects equal to or greater than the MSCs they are derived from in the treatment of OA. Most of these studies are in small animal models, limiting the translation of these results to humans. However, highly translational animal models are crucial for further understanding the efficacy of potential therapeutics and for close comparisons with humans. For this reason, the horse, which experiences the same gravitational impacts on joints similar to people, is a highly relevant large animal species for testing. The equine species has well-designed and validated OA models, and additionally, therapies can be further tested in naturally occurring OA to validate preclinical model testing. Therefore, the horse is a highly suitable model to increase our knowledge of the therapeutic potential of EVs.

Expression pattern analysis of m6A regulators reveals IGF2BP3 as a key modulator in osteoarthritis synovial macrophages

BACKGROUND

Disruption of N6 methyl adenosine (m6A) modulation hampers gene expression and cellular functions, leading to various illnesses. However, the role of m6A modification in osteoarthritis (OA) synovitis remains unclear. This study aimed to explore the expression patterns of m6A regulators in OA synovial cell clusters and identify key m6A regulators that mediate synovial macrophage phenotypes.

METHODS

The expression patterns of m6A regulators in the OA synovium were illustrated by analyzing bulk RNA-seq data. Next, we built an OA LASSO-Cox regression prediction model to identify the core m6A regulators. Potential target genes of these m6A regulators were identified by analyzing data from the RM2target database. A molecular functional network based on core m6A regulators and their target genes was constructed using the STRING database. Single-cell RNA-seq data were collected to verify the effects of m6A regulators on synovial cell clusters. Conjoint analyses of bulk and single-cell RNA-seq data were performed to validate the correlation between m6A regulators, synovial clusters, and disease conditions. After IGF2BP3 was screened as a potential modulator in OA macrophages, the IGF2BP3 expression level was tested in OA synovium and macrophages, and its functions were further tested by overexpression and knockdown in vitro.

RESULTS

OA synovium showed aberrant expression patterns of m6A regulators. Based on these regulators, we constructed a well-fitting OA prediction model comprising six factors (FTO, YTHDC1, METTL5, IGF2BP3, ZC3H13, and HNRNPC). The functional network indicated that these factors were closely associated with OA synovial phenotypic alterations. Among these regulators, the m6A reader IGF2BP3 was identified as a potential macrophage mediator. Finally, IGF2BP3 upregulation was verified in the OA synovium, which promoted macrophage M1 polarization and inflammation.

CONCLUSIONS

Our findings revealed the functions of m6A regulators in OA synovium and highlighted the association between IGF2BP3 and enhanced M1 polarization and inflammation in OA macrophages, providing novel molecular targets for OA diagnosis and treatment.

Comparative effectiveness of early initiation of oral nonsteroidal anti-inflammatory drug and oral acetaminophen therapies on the time to knee replacement in patients with knee osteoarthritis in Japan

BACKGROUND

Although disease-modifying properties of nonsteroidal anti-inflammatory drugs (NSAIDs) for osteoarthritis (OA) have been reported, the effects of NSAIDs on OA progression remain controversial. The purpose of this study was to investigate the effect of early initiation of oral NSAID therapy on the progression of knee OA.

METHODS

In this retrospective cohort study, we extracted data of patients newly diagnosed with knee OA between November 2007 and October 2018 from a Japanese claims database. The primary outcome was the time to knee replacement (KR), and the secondary outcome was the time to composite event including joint lavage and debridement, osteotomy, or arthrodesis in addition to KR. Weighted Cox regression analysis with standardized mortality/morbidity ratio (SMR) weight was performed to compare the outcomes between patients prescribed oral NSAID (NSAID group) and those prescribed oral acetaminophen (APAP) (APAP group) early after a diagnosis of knee OA. Propensity scores were calculated using logistic regression conditioned on potential confounding factors, and SMR weights were calculated using the propensity scores.

RESULTS

The study population comprised 14,261 patients, who were divided into two groups as follows: 13,994 in the NSAID group and 267 in the APAP group. The mean ages of patients in the NSAID and APAP groups were 56.9 and 56.1 years, respectively. Furthermore, 62.01% and 68.16% patients in the NSAID and APAP groups, respectively, were female. The NSAID group had a reduced risk of KR compared with the APAP group in the analysis using SMR weighting (SMR-weighted hazard ratio, 0.19; 95% confidence interval, 0.05-0.78). While no statistically significant difference was found for the risk of composite event between the two groups (SMR-weighted hazard ratio, 0.56; 95% confidence interval, 0.16-1.91).

CONCLUSIONS

The risk of KR in the NSAID group was significantly lower than that in the APAP group after accounting for residual confounding using SMR weighting. This finding suggests that oral NSAID therapy early after the initial diagnosis is associated with a reduced risk of KR in patients with symptomatic knee OA.

Sustained release resolvin D1 liposomes are effective in the treatment of osteoarthritis in obese mice

Osteoarthritis (OA) is the most common joint disorder and currently affects >500 million patients worldwide, with ~60% of them also suffering from obesity. There is no drug approved for human use that changes the course of OA progression. OA is one of the most common comorbidities of obesity, and obesity-related OA (ObOA) is a serious health concern because it shows heightened severity of tissue damage and also predominantly affects the working population. Unresolved inflammation is a major driver of ObOA, thus, resolving disease-associated inflammation is a viable strategy to treat ObOA. Resolvins are highly potent molecules that play a role in the resolution of inflammation and promote tissue healing. However, small molecules (like Resolvin D1; RvD1) have to be administered frequently or prior to injury because they lose their in vivo activity rapidly either by lymphatic clearance, or oxidation-mediated deactivation. In this study, we have encapsulated RvD1 in liposomes and established its efficacy in the mouse model of ObOA at much lower dosages than freely administered RvD1. Liposomal RvD1 (lipo-RvD1) acted as a source of the RvD1 molecules for ~11 days in vitro in synovial fluid derived from patients. When administered prophylactically or therapeutically, lipo-RvD1 suppressed cartilage damage in male C57BL/6 mice compared to untreated and free RvD1 treatments. This efficacy was achieved by increasing the proportion of the proresolution M2 macrophages over proinflammatory M1 macrophages in the synovial membrane. These results show the potential of lipo-RvD1 as an anti-OA agent.

Impact of Sustained Synovitis on Knee Joint Structural Degeneration: 4-Year MRI Data from the Osteoarthritis Initiative

BACKGROUND

Synovial inflammation is a risk factor for osteoarthritis (OA). But to date, there is limited information on how inflammation impacts progression of knee OA.

PURPOSE

To investigate how sustained synovitis, assessed with semi-quantitative magnetic resonance imaging (MRI) scores, impacts progression of knee degenerative changes over 4 years.

STUDY TYPE

Retrospective cohort study.

SUBJECTS

In 249 participants (N = 132 women [53%]), from the Osteoarthritis Initiative (OAI) two definitions for synovitis were used resulting in two groups of participants with sustained synovitis at baseline, 2-year, and 4-year follow-up (N = 80 and N = 132), and two groups without synovitis at all three time points (N = 81 and N = 47).

FIELD STRENGTH/SEQUENCE

3 T intermediate-weighted (IW) turbo spin-echo (TSE) sequence and three-dimensional (3D) dual-echo steady-state (DESS) sequence.

ASSESSMENT

Synovitis was scored semi-quantitatively using the Anterior Cruciate Ligament Osteoarthritis Score (ACLOAS), MRI Osteoarthritis Knee Score (MOAKS), and synovial proliferation score (SPS). Two MRI-based definitions of synovitis were used: (i) score ≥2 based on cumulative score of MOAKS and ACLOAS, and (ii) score ≥3 based on the cumulative score of ACLOAS, MOAKS, and SPS. Changes in structural abnormalities from baseline to year 4 measured using the whole-organ MRI score (WORMS) were defined as outcomes.

STATISTICAL TESTS

Linear regression models were used to compare the differences in longitudinal changes in WORMS scores between participants with and without sustained synovitis for each definition of sustained synovitis. A P-value of <0.05 was considered statistically significant.

RESULTS

Significantly higher rates of progression were found in participants with synovitis for patellar (Beta coeff. = 0.29) and medial tibial cartilage abnormalities (Beta coeff. = 0.29) for definition (i). For definition (ii), patellar (Beta coeff. = 0.36) and medial femoral cartilage (Beta coeff. = 0.30) abnormalities demonstrated significant differences.

DATA CONCLUSION

Greater progression of structural degenerative disease was observed in individuals with sustained synovitis compared to those without sustained synovitis, suggesting that sustained synovitis is associated with progressive OA.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

The Diagnostic and Prognostic Value of Synovial Fluid Analysis in Joint Diseases

Liquid biopsy is an emergent test method for the diagnosis and prognosis in the clinic. Joint fluid, also known as synovial fluid, contains a variety of bioactive constituents that can be selectively detected and further evaluated in a convenient fashion. Therefore, synovial fluid analysis functions as a specific form of liquid biopsy and plays a vital role in numerous joint diseases. In spite of the component analysis of aspirated synovial fluid beingconsidered as the gold standard for diagnosis of joint infections, biopsy of joint fluid benefits the initial diagnosis and long-term prognosis of degenerative, inflammatory, autoimmune, traumatic, congenital, and even neoplastic joint diseases. The convenience and accuracy for disease evaluation are significantly elevated as a result of the combination of synovial fluid analysis and other novel clinical technologies. In this review, we shed light on the latent role of synovial fluid in the diagnosis and prognosis of articular diseases and proposed future prospects for relevant research in this field.

Projected numbers of knee and hip arthroplasties up to the year 2030 in Japan

BACKGROUND

The aging population is a risk factor for an increase in osteoarthritis, leading to a potential increase in the number of arthroplasties worldwide. This study aimed to calculate the projected numbers of knee and hip arthroplasties in Japan until 2030 using national health insurance claim data.

METHODS

Data on the numbers of knee and hip arthroplasties performed in Japan between 2014 and 2018 were obtained from the National Database of Health Insurance Claims and Specific Health Checkups of Open Data Japan. Demographic data were obtained from the National Institute of Population and Social Security Research. Collected data were categorized into three age subgroups (40-64, 65-74, and ≥75 years) for each sex. Projections were based on the Poisson regression model.

RESULTS

The number of knee arthroplasties in Japan in 2030 was projected to be 4052 for men aged 40-64 years, 6942 for men aged 65-74 years, 14,986 for men aged ≥75 years, 7092 for women aged 40-64 years, 22,957 for women aged 65-74 years, and 58,340 for women aged ≥75 years. The number of hip arthroplasties in Japan in 2030 was predicted to be 8936 for men aged 40-64 years, 9005 for men aged 65-74 years, 5972 for men aged ≥75 years, 27,327 for women aged 40-64 years, 36,416 for women aged 65-74 years, and 37,011 for women aged ≥75 years.

CONCLUSION

The numbers of knee and hip arthroplasties are expected to continue to increase over the next 10 years in Japan in most age groups. These findings are useful for future healthcare resource planning to meet the demand for knee and hip arthroplasties.

Diffusion Tensor and Dynamic Contrast-Enhanced Magnetic Resonance Imaging Correlate with Molecular Markers of Inflammation in the Synovium

Objectives: It is difficult to capture the severity of synovial inflammation on imaging. Herein we hypothesize that diffusion tensor imaging (DTI) derived metrics may delineate the aggregation of the inflammatory cells and expression of inflammatory cytokines and dynamic contrast-enhanced (DCE) imaging may provide information regarding vascularity in the inflamed synovium. Patients and methods: Patients with knee arthritis (>3-months duration) underwent conventional (T2-weighted fast spin echo and spin echo T1-weighted images) as well as DTI and DCE MRI and thereafter arthroscopic guided synovial biopsy. DCE and DTI metrics were extracted from the masks of the segments of the inflamed synovium which enhanced on post-contrast T1-weighted MRI. These metrics were correlated with immunohistochemistry (IHC) parameters of inflammation on synovium. Statistical analysis: Pearson’s correlation was performed to study the relationship between DTI- and DCE-derived metrics, IHC parameters, and post-contrast signal intensity. Linear regression model was used to predict the values of IHC parameters using various DTI and DCE derived metrics as predictors. Results: There were 80 patients (52 male) with mean age 39.78 years and mean disease duration 19.82 months. Nineteen patients had tuberculosis and the rest had chronic undifferentiated monoarthritis (n = 31), undifferentiated spondyloarthropathy (n = 14), rheumatoid arthritis (n = 6), osteoarthritis (n = 4), reactive arthritis (n = 3), ankylosing spondylitis (n = 2), and juvenile idiopathic arthritis (n = 1). Fractional anisotropy (FA), a metric of DTI, had significant correlation with number of immune cells (r = 0.87, p < 0.01) infiltrating into the synovium and cytokines (IL-1β, r = 0.55, p < 0.01; TNF-α, r = 0.42, p < 0.01) in all patients and also in each group of patients and adhesion molecule expressed on these cells in all patients (CD54, r = 0.51, p < 0.01). DCE parameters significantly correlated with CD34 (blood flow, r = 0.78, p < 0.01; blood volume, r = 0.76, p < 0.01) in each group of patients, a marker of neo-angiogenesis. FA was the best predictor of infiltrating inflammatory cells, adhesion molecule and proinflammatory cytokines. Amongst the DCE parameters, blood volume, was best predictor of CD34. Conclusion: DTI and DCE metrics capture cellular and molecular markers of synovial inflammation in patients with chronic inflammatory arthritis.

Associations between metabolic factors and radiographic knee osteoarthritis in early disease - a cross-sectional study of individuals with knee pain

Objective

Metabolic factors have been shown to be associated to severe radiographic knee osteoarthritis (RKOA). However, more knowledge is needed in early clinical knee osteoarthritis (KOA). The aim was to study associations between metabolic factors and radiographic knee osteoarthritis (OA) in individuals with knee pain. A second aim was to study associations between metabolic factors and RKOA in those with normal BMI and in those overweight/obese, respectively.

Method

This cross-sectional study included 282 individuals with knee pain (without cruciate ligament injury) and aged 30–67 years, and 70% women. Waist circumference, body mass index (BMI), proportion of fat and visceral fat area (VFA) were assessed. RKOA was defined as Ahlbäck grade 1 in at least one knee. Fasting blood samples were taken and triglycerides, cholesterol (total, low density lipoprotein (LDL) and high density lipoprotein (HDL)), C-reactive protein (CRP), glucose, HbA1C were analysed. Metabolic syndrome was defined in accordance with the International Diabetes Federation (IDF). Associations were analysed by logistic regression.

Results

Individuals with RKOA were older, had higher BMI, higher VFA, larger waist circumference and had increased total cholesterol, triglycerides and LDL-cholesterol, but not fasting glucose. There was no difference between the group with RKOA vs. non-radiographic group regarding the presence of metabolic syndrome. In a subgroup analysis of individuals with normal BMI (n = 126), those with RKOA had higher VFA, more central obesity, higher levels of CRP and total cholesterol, compared with individuals without RKOA. In individuals with obesity, age was the only outcome associated to RKOA.

Conclusion

There were clear associations between metabolic factors and RKOA in individuals with knee pain, also in those with normal BMI. In individuals with obesity age was the only variable associated to RKOA.

Trial registration:

clinicalTrials.gov Identifier: NCT04928170.

Emerging role of lncRNAs in osteoarthritis: An updated review

Osteoarthritis (OA) is a prevalent joint disease, which is associated with progressive articular cartilage loss, synovial inflammation, subchondral sclerosis and meniscus injury. The molecular mechanism underlying OA pathogenesis is multifactorial. Long non-coding RNAs (lncRNAs) are non-protein coding RNAs with length more than 200 nucleotides. They have various functions such as modulating transcription and protein activity, as well as forming endogenous small interfering RNAs (siRNAs) and microRNA (miRNA) sponges. Emerging evidence suggests that lncRNAs might be involved in the pathogenesis of OA which opens up a new avenue for the development of new biomarkers and therapeutic strategies. The purpose of this review is to summarize the current clinical and basic experiments related to lncRNAs and OA with a focus on the extensively studied H19, GAS5, MALAT1, XIST and HOTAIR. The potential translational value of these lncRNAs as therapeutic targets for OA is also discussed.

Chondroitin sulfate microspheres anchored with drug-loaded liposomes play a dual antioxidant role in the treatment of osteoarthritis

Reactive oxygen species (ROS) play a critical role in the pathogenesis of osteoarthritis. The injection of a single antioxidant drug is characterized by low drug utilization and short residence time in the articular cavity, limiting the therapeutic effect of antioxidant drugs on osteoarthritis. Currently, the drug circulation half-life can be extended using delivery vehicles such as liposomes and microspheres, which are widely used to treat diseases. In addition, the composite carriers of liposomes and hydrogel microspheres can combine the advantages of different material forms and show stronger plasticity and flexibility than traditional single carriers, which are expected to become new local drug delivery systems. Chondroitin sulfate, a sulfated glycosaminoglycan commonly found in native cartilage, has good antioxidant properties and degradability and is used to develop an injectable chondroitin sulfate hydrogel by covalent modification with photo-cross-linkable methacryloyl groups (ChsMA). Herein, ChsMA microgels anchored with liquiritin (LQ)-loaded liposomes (ChsMA@Lipo) were developed to delay the progression of osteoarthritis by dual antioxidation. On the one hand, the antioxidant drug LQ wrapped in ChsMA@Lipo microgels exhibits significant sustained-release kinetics due to the double obstruction of the lipid membrane and the hydrogel matrix network. On the other hand, ChsMA can eliminate ROS through degradation into chondroitin sulfate monomers by enzymes in vivo. Therefore, ChsMA@Lipo, as a degradable and dual antioxidant drug delivery platform, is a promising option for osteoarthritis treatment. STATEMENT OF SIGNIFICANCE: Compared with the traditional single carrier, the composite carriers of hydrogel microspheres and liposome can complement the advantages of different materials, which shows stronger plasticity and flexibility, and is expected to become a new and efficient drug delivery system. ChsMA@Lipo not only attenuates IL-1β-induced ECM degradation in chondrocytes but also inhibits the M1 macrophages polarization and the inflammasome activation. The obtained ChsMA@Lipo alleviates the progression of osteoarthritis in vivo, which is promising for osteoarthritis treatment.

Phenotype Diversity of Macrophages in Osteoarthritis: Implications for Development of Macrophage Modulating Therapies

Chronic inflammation is implicated in numerous human pathologies. In particular, low-grade inflammation is currently recognized as an important mechanism of osteoarthritis (OA), at least in some patients. Among the signs of the inflammatory process are elevated macrophage numbers detected in the OA synovium compared to healthy controls. High macrophage counts also correlate with clinical symptoms of the disease. Macrophages are central players in the development of chronic inflammation, pain, cartilage destruction, and bone remodeling. However, macrophages are also involved in tissue repair and remodeling, including cartilage. Therefore, reduction of macrophage content in the joints correlates with deleterious effects in OA models. Macrophage population is heterogeneous and dynamic, with phenotype transitions being induced by a variety of stimuli. In order to effectively use the macrophage inflammatory circuit for treatment of OA, it is important to understand macrophage heterogeneity and interactions with surrounding cells and tissues in the joint. In this review, we discuss functional phenotypes of macrophages and specific targeting approaches relevant for OA treatment development.

Superoxide dismutase-loaded porous polymersomes as highly efficient antioxidant nanoparticles targeting synovium for osteoarthritis therapy

Oxidative stress and the reactive oxygen species (ROS) have important roles in osteoarthritis (OA) development and progression. Scavenging ROS by exogenous antioxidant enzymes could be a promising approach for OA treatment. However, the direct use of antioxidant enzymes, such as superoxide dismutase (SOD), is challenging due to a lack of effective drug delivery system to knee joints. This study utilized a highly efficient antioxidative nanoparticle based on SOD-loaded porous polymersome nanoparticles (SOD-NPs) for delivery of SOD to mouse knee joints. The resultant SOD-NPs had prolonged mouse joint retention time with predominant accumulation in synovium but not in articular cartilage. Examining human synovial explants revealed that SOD-NPs minimize oxidative damages induced by OA-like insults. Intra-articular injections of SOD-NPs in mice receiving OA surgery were effective in attenuating OA initiation and preventing its further progression. Mechanistically, SOD-NPs reduced ROS production and the synthesis of catabolic proteases in both articular cartilage and synovium. Hence, our work demonstrates the therapeutic potential of SOD-NPs and indicate that targeting synovium holds a great promise for OA therapy.

Pathological, Morphometric and Correlation Analysis of the Modified Mankin Score, Tidemark Roughness and Calcified Cartilage Thickness in Rat Knee Osteoarthritis after Extracorporeal Shockwave Therapy

The paper displayed the pathological changes and relationships of the modified Mankin score, tidemark roughness and calcified cartilage (CC) thickness by extracorporeal shockwave therapy (ESWT) (0.25 mJ/ mm2 with 800 impulses) on different positions of the medial and lateral rat knee OA joint. After the experiments, the articular cartilage was assessed using histomorphometry, image analysis and statistical method. In the micro-CT analysis, ESWT on medial groups were better than lateral groups in the trabecular volume and trabecular number. The data showed a strong negative correlation between the modified Mankin score and tidemark roughness (r = -0.941; P < 0.001). In terms of the relationship of tidemark roughness with CC thickness, the medial and Sham groups showed a significant negative correlation (r = -0.788, P = 0.022). Additionally, the Euclidean distance derived from 3D scatter plot analysis was an indicator of chondropathic conditions, exhibiting a strong correlation with OA stage in the articular cartilage of the femur (r = 0.911, P < 0.001) and tibia (r = 0.890, P < 0.001) after ESWT. Principle component analysis (PCA) further demonstrated that ESWT applied to medial locations had a better outcome than treatment at lateral locations for knee OA by comparing with Sham and OA groups, and CC thickness was the most important factor affecting hyaline cartilage repair after ESWT.

The histopathological synovitis score is influenced by biopsy location in patients with knee osteoarthritis

INTRODUCTION

Osteoarthritis (OA) and rheumatoid arthritis (RA) represent the most common forms of arthritis, which are mainly caused by mechanical and inflammatory components, respectively. Determination of synovial inflammation in synovial biopsies via the histopathological Krenn score may be crucial for correct diagnosis and treatment. Specifically, it remains unclear whether synovitis scores differ among multiple biopsy locations within a single joint.

MATERIALS AND METHODS

Eighty synovial samples were taken from four standardized regions of the knee in 20 patients (ten primary OA, ten secondary OA) undergoing total knee arthroplasty (TKA) or total synovectomy. The Krenn synovitis score (grade 0-9) was determined in a blinded manner by two expert pathologists in all biopsies. Next to the inter-rater reliability, we evaluated the agreement of the determined scores among the four biopsy locations within each knee.

RESULTS

The inter-rater reliability between the two pathologists was very high (Cohen's kappa = 0.712; r = 0.946; ICC = 0.972). The mean synovitis score was significantly higher in knees with secondary than in primary OA (p = 0.026). Importantly, we found clear differences between the scores of the four different biopsy locations within the individual knee joints, with an average deviation of 10.6%. These deviations were comparable in knees with primary and secondary OA (p = 0.64).

CONCLUSIONS

While we confirmed the synovitis score as a reliable and reproducible parameter to assess the histopathological synovitis grade in the knee, the considerable variability within the joint indicates that multiple synovial biopsies from different regions should be obtained to enable reliable results of the synovitis score.

Safety and Clinical Response Following a Repeat Intraarticular Injection of Tin-117m (117mSn) Colloid in Dogs with Elbow Osteoarthritis

Objective

To determine if a repeat intraarticular (IA) injection of a tin-117m colloid radiosynoviorthesis (RSO) agent can be safely given in the same joint 12 months after an initial injection for treatment of canine elbow osteoarthritis (OA), and to evaluate the pain reduction effect of the repeat injection.

Methods and Materials

Nine client owned dogs with grade 1 or 2 elbow OA were given an IA injection of tin-117m colloid in both elbows, one of which had been treated ≤12 months earlier with the same RSO device. Treatment safety was evaluated by joint fluid analysis at baseline (BL) and at 180 days after treatment, and by urinalysis, CBC, and serum chemistry analysis of diagnostic samples obtained at BL and 180 days. Radiographs, computed tomography, and MRI scans were obtained at BL and 180 days to determine if disease progression differed in elbows given one versus two injections. Clinical response to treatment was assessed subjectively by dog owner responses to the Canine Brief Pain Inventory (CBPI) survey at BL, 90 and 180 days, and objectively by investigator-conducted force plate (FP) analysis of dogs at BL, 90, and 180 days.

Results

All post-treatment urinalysis, CBC and clinical chemistry results were within normal ranges. Joint fluid analysis showed a significant (P=0.0411) reduction in the percentage of monocytes at 180 days, consistent with the tin-117m colloid mode of action of apoptosis of pro-inflammatory macrophages at the injection site. There was no significant difference in OA progression in elbows given one or two injections. The treatment success rate was 55.5% (5/9) on day 90 as determined either by CBPI responses or FP analysis, and 66.6% (6/9) on day 180 as determined by FP analysis.

Conclusion

The tin-117m colloid can be safely given as a repeat injection 12 months after an initial injection, and can potentially provide a durable therapeutic response in dogs with elbow OA.

A dysfunctional TRPV4-GSK3β pathway prevents osteoarthritic chondrocytes from sensing changes in extracellular matrix viscoelasticity

Changes in the composition and viscoelasticity of the extracellular matrix in load-bearing cartilage influence the proliferation and phenotypes of chondrocytes, and are associated with osteoarthritis. However, the underlying molecular mechanism is unknown. Here we show that the viscoelasticity of alginate hydrogels regulates cellular volume in healthy human chondrocytes (with faster stress relaxation allowing cell expansion and slower stress relaxation restricting it) but not in osteoarthritic chondrocytes. Cellular volume regulation in healthy chondrocytes was associated with changes in anabolic gene expression, in the secretion of multiple pro-inflammatory cytokines, and in the modulation of intracellular calcium regulated by the ion-channel protein transient receptor potential cation channel subfamily V member 4 (TRPV4), which controls the phosphorylation of glycogen synthase kinase 3β (GSK3β), an enzyme with pleiotropic effects in osteoarthritis. A dysfunctional TRPV4-GSK3β pathway in osteoarthritic chondrocytes rendered the cells unable to respond to environmental changes in viscoelasticity. Our findings suggest strategies for restoring chondrocyte homeostasis in osteoarthritis.

High-Molecular-Weight Hyaluronic Acid Inhibits IL-1β-Induced Synovial Inflammation and Macrophage Polarization through the GRP78-NF-κB Signaling Pathway

Recent evidence has suggested that synovial inflammation and macrophage polarization were involved in the pathogenesis of osteoarthritis (OA). Additionally, high-molecular-weight hyaluronic acid (HMW-HA) was often used clinically to treat OA. GRP78, an endoplasmic reticulum (ER) stress chaperone, was suggested to contribute to the hyperplasia of synovial cells in OA. However, it was still unclear whether HMW-HA affected macrophage polarization through GRP78. Therefore, we aimed to identify the effect of HMW-HA in primary synovial cells and macrophage polarization and to investigate the role of GRP78 signaling. We used IL-1β to treat primary synoviocytes to mimic OA, and then treated them with HMW-HA. We also collected conditioned medium (CM) to culture THP-1 macrophages and examine the changes in the phenotype. IL-1β increased the expression of GRP78, NF-κB (p65 phosphorylation), IL-6, and PGE2 in primary synoviocytes, accompanied by an increased macrophage M1/M2 polarization. GRP78 knockdown significantly reversed the expression of IL-1β-induced GRP78-related downstream molecules and macrophage polarization. HMW-HA with GRP78 knockdown had additive effects in an IL-1β culture. Finally, the synovial fluid from OA patients revealed significantly decreased IL-6 and PGE2 levels after the HMW-HA treatment. Our study elucidated a new form of signal transduction for HMW-HA-mediated protection against synovial inflammation and macrophage polarization and highlighted the involvement of the GRP78-NF-κB signaling pathway.

Immunoengineering the next generation of arthritis therapies

Immunoengineering continues to revolutionize healthcare, generating new approaches for treating previously intractable diseases, particularly in regard to cancer immunotherapy. In joint diseases, such as osteoarthritis (OA) and rheumatoid arthritis (RA), biomaterials and anti-cytokine treatments have previously been at that forefront of therapeutic innovation. However, while many of the existing anti-cytokine treatments are successful for a subset of patients, these treatments can also pose severe risks, adverse events and off-target effects due to continuous delivery at high dosages or a lack of disease-specific targets. The inadequacy of these current treatments has motivated the development of new immunoengineering strategies that offer safer and more efficacious alternative therapies through the precise and controlled targeting of specific upstream immune responses, including direct and mechanistically-driven immunoengineering approaches. Advances in the understanding of the immunomodulatory pathways involved in musculoskeletal disease, in combination with the growing emphasis on personalized medicine, stress the need for carefully considering the delivery strategies and therapeutic targets when designing therapeutics to better treat RA and OA. Here, we focus on recent advances in biomaterial and cell-based immunomodulation, in combination with genetic engineering, for therapeutic applications in joint diseases. The application of immunoengineering principles to the study of joint disease will not only help to elucidate the mechanisms of disease pathogenesis but will also generate novel disease-specific therapeutics by harnessing cellular and biomaterial responses. STATEMENT OF SIGNIFICANCE: It is now apparent that joint diseases such as osteoarthritis and rheumatoid arthritis involve the immune system at both local (i.e., within the joint) and systemic levels. In this regard, targeting the immune system using both biomaterial-based or cellular approaches may generate new joint-specific treatment strategies that are well-controlled, safe, and efficacious. In this review, we focus on recent advances in immunoengineering that leverage biomaterials and/or genetically engineered cells for therapeutic applications in joint diseases. The application of such approaches, especially synergistic strategies that target multiple immunoregulatory pathways, has the potential to revolutionize our understanding, treatment, and prevention of joint diseases.

Dynamics of Quality of Life Indicators in Patients with Chronic Synovitis of the Knee Joint after Arthroscopic Laser Double-mode Synovectomy

Background: The treatment of patients with chronic synovitis of the knee joint is a challenge faced by many doctors all around the world. Treatment of this pathology is often a difficult task. Aim. The aim of the study was improving the results of treatment of patients with chronic synovitis of the knee joint by applying two wavelengths of radiation. Material and methods. The treatment results of 50 patients with chronic synovitis of the knee joint aged 23 to 67 years with stage II-IV osteoarthritis according to the Kellgren-Lawrence classification were analyzed. All patients underwent arthroscopic sanation, partial laser synovectomy using LSP-IRE-Polus apparatus, wavelength 0,97 microns in pulse-periodic mode (pulse 100 ms, pause 50 ms) with power 5 W and wavelength 1,56 microns in continuous mode with power 5 W. Morphological examination of the synovial membrane and capsule was performed. Preoperative, 3, 6 and 12 month postoperative questionnaires were administered using the following scales and questionnaires: VAS, Leken index, WOMAC and KOOS. Results. Mean age (M) was 45.32±131, BMI 28.63±4.72kg/m2, duration of synovitis 2.26±1.91 years. A statistically significant improvement on the VAS, WOMAC, Leken, KOOS scales was noted by the 3rd month of postoperative follow-up. By the 6th month postoperatively, the results had further improved. The achieved results were preserved up to 12 months after surgery (P <0.05). Conclusion. The results suggest that the proposed technique may be introduced into clinical practice.

Cell Interplay in Osteoarthritis

Osteoarthritis (OA) is a common chronic disease and a significant health concern that needs to be urgently solved. OA affects the cartilage and entire joint tissues, including the subchondral bone, synovium, and infrapatellar fat pads. The physiological and pathological changes in these tissues affect the occurrence and development of OA. Understanding complex crosstalk among different joint tissues and their roles in OA initiation and progression is critical in elucidating the pathogenic mechanism of OA. In this review, we begin with an overview of the role of chondrocytes, synovial cells (synovial fibroblasts and macrophages), mast cells, osteoblasts, osteoclasts, various stem cells, and engineered cells (induced pluripotent stem cells) in OA pathogenesis. Then, we discuss the various mechanisms by which these cells communicate, including paracrine signaling, local microenvironment, co-culture, extracellular vesicles (exosomes), and cell tissue engineering. We particularly focus on the therapeutic potential and clinical applications of stem cell-derived extracellular vesicles, which serve as modulators of cell-to-cell communication, in the field of regenerative medicine, such as cartilage repair. Finally, the challenges and limitations related to exosome-based treatment for OA are discussed. This article provides a comprehensive summary of key cells that might be targets of future therapies for OA.

Treatment response in dogs with naturally occurring grade 3 elbow osteoarthritis following intra-articular injection of 117mSn (tin) colloid

The radionuclide ^117mSn (tin-117m) embedded in a homogeneous colloid is a novel radiosynoviorthesis (RSO) device for intra-articular (IA) administration to treat synovial inflammation and mitigate osteoarthritis (OA) in dogs. A study to evaluate tin-117m colloid treatment response in dogs with OA was conducted at two centers, the School of Veterinary Medicine at Louisiana State University, and at a referral practice in Houston, Texas. The tin-117m colloid was administered per-protocol to 14 client-owned dogs with radiographically confirmed, grade 3 OA in one or both elbow joints. Dog owners and attending clinicians assessed the level of pain at baseline (BL) and the post-treatment pain response at 90-day intervals for one year. Owners assessed treatment response according to a pain severity score (PSS) and a pain interference score (PIS) as defined by the Canine Brief Pain Inventory. Clinicians reported a lameness score using a 0–5 scale, from no lameness to continuous non-weight bearing lameness, when observing dogs at a walk and a trot. The rate of treatment success as determined by improved mean PSS and PIS scores reported by dog owners was >70% at all time points. Clinicians reported an improved mean pain score from BL at post-treatment Days 90 (p<0.05), 180, and 270. The dog owner and clinician assessments of treatment success were significantly correlated (p>0.05) at Day 90 and Day 180 time points. Results indicated that a single IA dose of tin-117m colloid provided a significant reduction in pain and lameness and improved functionality for up to a full year, with no adverse treatment related effects, in a high percentage of dogs with advanced, clinical OA of the elbow joint.

Synovitis and bone marrow lesions associate with symptoms and radiographic progression in hand osteoarthritis: a systematic review and meta-analysis of observational studies

AIMS

To systematically review observational studies for the association between features detected on ultrasound (US) and magnetic resonance imaging (MRI) and, symptoms, signs and radiographic progression of hand osteoarthritis (OA).

METHODS

Medline, Web of Science, EMBASE, CINAHL and AMED were searched from inception to 14^th January 2020 to identify relevant studies. Quality of studies was assessed using the Newcastle-Ottawa scales and data were extracted. Odds ratios (OR) and linear regression coefficients and 95% confidence intervals (CI) were pooled using the random-effects model (METAN package, Stata v16.1). Heterogeneity and publication bias were assessed.

RESULTS

Thirty-two studies using US and MRI comprising 1,350 and 638 participants respectively were included. While only grey-scale synovitis (GSS) associated with AUSCAN-pain (pooled Regression coefficient (95% CI): 0.46 (0.13-0.79); 0-20 scale for AUSCAN-pain), US-detected osteophytes, GSS and power Doppler (PD) [pooled ORs (95% CI): 2.68(2.16-3.33), 2.38(1.74-3.26) and 2.04 (1.45-2.88)] as well as MRI-detected bone marrow lesions (BMLs), synovitis, osteophytes, and central bone erosions (CBEs) associated with joint tenderness [pooled ORs (95% CI): 2.59(2.12-3.18), 2.17(1.85-2.54), 2.15(1.55-2.99), and 2.41 (1.45-4.02)] respectively. US-detected GSS and PD associated with radiographic progression of CBEs [pooled ORs 5.37, 5.08], osteophytes [pooled ORs 5.17, 6.45], and joint space narrowing (pooled ORs 4.28, 4.36) whilst MRI-detected synovitis and BMLs associated with increasing KL grades with pooled ORs 2.92, 2.54 respectively.

CONCLUSIONS

US and MRI-detected structural and inflammatory changes associate with tenderness, whilst articular inflammation and subchondral bone damage associate with radiographic hand OA progression. There was inconsistent relationship between these changes and pain.

Text Mining-Based Drug Discovery in Osteoarthritis

Background

Osteoarthritis (OA) is a chronic and degenerative joint disease, which causes stiffness, pain, and decreased function. At the early stage of OA, nonsteroidal anti-inflammatory drugs (NSAIDs) are considered the first-line treatment. However, the efficacy and utility of available drug therapies are limited. We aim to use bioinformatics to identify potential genes and drugs associated with OA.

Methods

The genes related to OA and NSAIDs therapy were determined by text mining. Then, the common genes were performed for GO, KEGG pathway analysis, and protein-protein interaction (PPI) network analysis. Using the MCODE plugin-obtained hub genes, the expression levels of hub genes were verified using quantitative real-time polymerase chain reaction (qRT-PCR). The confirmed genes were queried in the Drug Gene Interaction Database to determine potential genes and drugs.

Results

The qRT-PCR result showed that the expression level of 15 genes was significantly increased in OA samples. Finally, eight potential genes were targetable to a total of 53 drugs, twenty-one of which have been employed to treat OA and 32 drugs have not yet been used in OA.

Conclusions

The 15 genes (including PTGS2, NLRP3, MMP9, IL1RN, CCL2, TNF, IL10, CD40, IL6, NGF, TP53, RELA, BCL2L1, VEGFA, and NOTCH1) and 32 drugs, which have not been used in OA but approved by the FDA for other diseases, could be potential genes and drugs, respectively, to improve OA treatment. Additionally, those methods provided tremendous opportunities to facilitate drug repositioning efforts and study novel target pharmacology in the pharmaceutical industry.

Circ_0116061 regulated the proliferation, apoptosis, and inflammation of osteoarthritis chondrocytes through regulating the miR-200b-3p/SMURF2 axis

Background

Circular RNA (circRNA) has been shown to be associated with osteoarthritis (OA) progression. Circ_0116061 has been found to be highly expressed in OA cartilage tissues, but its role and mechanism in OA progression remain unclear.

Methods

Expression levels of circ_0116061, microRNA (miR)-200b-5p, and Smad ubiquitin regulatory factor 2 (SMURF2) were detected using quantitative real-time PCR. The proliferation and apoptosis of cells were measured using cell counting kit 8 (CCK8) assay, colony formation assay, and flow cytometry. Furthermore, the protein levels of proliferation-related marker, apoptosis-related markers, inflammatory factors, and SMURF2 were tested using western blot (WB) analysis. In addition, the interaction between miR-200b-3p and circ_0116061 or SMURF2 was examined using dual-luciferase reporter assay and biotin-labeled RNA pull-down assay.

Results

Circ_0116061 and SMURF2 were highly expressed, and miR-200b-3p was lowly expressed in OA cartilage tissues. Knockdown of circ_0116061 could promote the proliferation and inhibit the apoptosis and inflammation of OA chondrocytes. MiR-200b-3p could be sponged by circ_0116061, and its inhibitor could reverse the regulation of circ_0116061 silencing on the biological functions of OA chondrocytes. SMURF2 was a target of miR-200b-3p, and its expression was positively regulated by circ_0116061. Silencing of SMURF2 also could enhance the proliferation and suppress the apoptosis and inflammation of OA chondrocytes. Furthermore, the regulation of circ_0116061 silencing on the biological functions of OA chondrocytes also could be reversed by SMURF2 overexpression.

Conclusion

Our data showed that circ_0116061 might regulate the miR-200b-3p/SMURF2 axis to promote the progression of OA.

Phenotypic alteration of macrophages during osteoarthritis: a systematic review

OBJECTIVE

Osteoarthritis (OA) has long been regarded as a disease of cartilage degeneration, whereas mounting evidence implies that low-grade inflammation contributes to OA. Among inflammatory cells involved, macrophages play a crucial role and are mediated by the local microenvironment to exhibit different phenotypes and polarization states. Therefore, we conducted a systematic review to uncover the phenotypic alterations of macrophages during OA and summarized the potential therapeutic interventions via modulating macrophages.

METHODS

A systematic review of multiple databases (PubMed, Web of Science, ScienceDirect, Medline) was performed up to February 29, 2020. Included articles were discussed and evaluated by two independent reviewers. Relevant information was analyzed with a standardized and well-designed template.

RESULTS

A total of 28 studies were included. Results were subcategorized into two sections depending on sources from human tissue/cell-based studies (12 studies) and animal experiments (16 studies). The overall observation indicated that M1 macrophages elevated in both synovium and circulation during OA development, along with lower numbers of M2 macrophages. The detailed alterations of macrophages in both synovium and circulation were listed and analyzed. Furthermore, interventions against OA via regulating macrophages in animal models were highlighted.

CONCLUSION

This study emphasized the importance of the phenotypic alterations of macrophages in OA development. The classical phenotypic subcategory of M1 and M2 macrophages was questionable due to controversial and conflicting results. Therefore, further efforts are needed to categorize macrophages in an exhaustive manner and to use advanced technologies to identify the individual roles of each subtype of macrophages in OA.

Phospholipase A2 inhibitor-loaded micellar nanoparticles attenuate inflammation and mitigate osteoarthritis progression

Treating osteoarthritis (OA) remains a major clinical challenge. Despite recent advances in drug discovery and development, no disease-modifying drug for knee OA has emerged with any notable clinical success, in part, due to the lack of valid and responsive therapeutic targets and poor drug delivery within knee joints. In this work, we show that the amount of secretory phospholipase A₂ (sPLA₂) enzyme increases in the articular cartilage in human and mouse OA cartilage tissues. We hypothesize that the inhibition of sPLA₂ activity may be an effective treatment strategy for OA. To develop an sPLA₂-responsive and nanoparticle (NP)-based interventional platform for OA management, we incorporated an sPLA₂ inhibitor (sPLA₂i) into the phospholipid membrane of micelles. The engineered sPLA₂i-loaded micellar NPs (sPLA₂i-NPs) were able to penetrate deep into the cartilage matrix, prolong retention in the joint space, and mitigate OA progression. These findings suggest that sPLA₂i-NPs can be promising therapeutic agents for OA treatment.

PTH1-34 inhibited TNF-α expression and antagonized TNF-α-induced MMP13 expression in MIO mice

This study aims to investigate the effects and mechanisms of parathyroid hormone [1-34] (PTH1-34) on TNF-α-stimulated mice chondrocytes, as well as cartilage from a meniscus injury induced osteoarthritis (MIO) mice model. The C57BL/6J mice received medial meniscectomy, and then administrated with PTH1-34. The results showed that PTH1-34 administration decreased secondary allodynia and the pain-related transcripts. The IHC, ELISA, Micro-CT imaging and histopathology analysis revealed the significantly improved subchondral plate thickness and bone porosity, the reduced pro-inflammatory cytokines in serum and joint fluid. In vitro, mice chondrocyte was treated with TNF-α or co-cultured with synovial cells. The results showed that TNF-α markedly upregulated the MMP13 expression, and the ERK1/2, NF-κB or PI3K signaling pathway inhibitors could reverse the induction effect of TNF-α on expression of MMP13 in chondrocytes. PTH1-34 alone has no effect on the expression of MMP13 and NF-κB signaling pathways, but the PTH1-34 could reverse the induction effect of TNF-α on MMP13 expression and NF-κB signaling pathway activation in chondrocytes. In addition, PTH1-34 administration inhibited the expression of TNF-α and MMP13, and chondrocyte viability, while the PKA repressor reversed the effect of PTH1-34 in chondrocytes co-cultured with synovial cells. In conclusion, PTH1-34 has an obvious analgesic and anti-inflammatory effect, inhibits the matrix synthesis and alleviates the progression of osteoarthritis. In vitro, PTH1-34 inhibited TNF-α expression and antagonized TNF-α-induced MMP13 expression via the PKA pathway and the NF-κB signaling pathways, respectively.

The Role of Fibrosis in Osteoarthritis Progression

Osteoarthritis (OA) is a chronic degenerative joint disease where the main characteristics include cartilage degeneration and synovial membrane inflammation. These changes in the knee joint eventually dampen the function of the joint and restrict joint movement, which eventually leads to a stage where total joint replacement is the only treatment option. While much is still unknown about the pathogenesis and progression mechanism of OA, joint fibrosis can be a critical issue for better understanding this disease. Synovial fibrosis and the generation of fibrocartilage are the two main fibrosis-related characteristics that can be found in OA. However, these two processes remain mostly misunderstood. In this review, we focus on the fibrosis process in OA, especially in the cartilage and the synovium tissue, which are the main tissues involved in OA.

Formulation of Topical Dosage Forms Containing Synthetic and Natural Anti-Inflammatory Agents for the Treatment of Rheumatoid Arthritis

Topical anti-inflammatory and analgesic effect for the treatment of rheumatoid arthritis is of major interest because of their fewer side effects compared to oral therapy. The purpose of this study was to prepare different types of topical formulations (ointments and gels) containing synthetic and natural anti-inflammatory agents with different excipients (e.g.,: surfactants, gel-forming) for the treatment of rheumatoid arthritis. The combination of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), diclofenac sodium, a topical analgesic agent methyl salicylate, and a lyophilized extract of Calendula officinalis with antioxidant effect were used in our formulations. The aim was to select the appropriate excipients and dosage form for the formulation in order to enhance the diffusion of active substances and to certify the antioxidant, analgesic, and anti-inflammatory effects of these formulations. To characterize the physicochemical properties of the formulations, rheological studies, and texture profile analysis were carried out. Membrane diffusion and permeability studies were performed with Franz-diffusion method. The therapeutic properties of the formulations have been proven by an antioxidant assay and a randomized prospective study that was carried out on 115 patients with rheumatoid arthritis. The results showed that the treatment with the gel containing diclofenac sodium, methyl salicylate, and lyophilized Calendula officinalis as active ingredients, 2-propenoic acid homopolymer (Synthalen K) as gel-forming excipient, distilled water, triethanolamine, and glycerol had a beneficial analgesic and local anti-inflammatory effect.

TWIST1-MicroRNA-10a-MAP3K7 Axis Ameliorates Synovitis of Osteoarthritis in Fibroblast-like Synoviocytes

Synovitis refers to the inflammation of the synovial membrane and is commonly detected in patients with osteoarthritis (OA). Recent reports have suggested that microRNAs (miRNAs) could be a promising target for diagnosis and prognosis in OA. This study examines the effect of microRNA-10a (miR-10a) in fibroblast-like synoviocyte (FLS)-mediated synovitis obtained from patients with OA. Expression of miR-10a is negatively associated with the severity of synovitis. miR-10a inhibited proliferation, migration, and secretion of pro-inflammatory cytokines of OA-FLS that were obtained from OA patients in vitro. By using a patient-derived xenograft (PDX) model, miR-10a repressed proliferation of OA-FLSs and production of OA synovium-derived pro-inflammatory cytokines in vivo. Twist Family BHLH Transcription Factor 1 (TWIST1) and mitogen-activated protein kinase kinase kinase 7 (MAP3K7) were identified as an upstream regulator and direct target of miR-10a in OA-FLSs, respectively. Nuclear factor κB (NF-κB) signaling pathway, a downstream pathway of MAP3K7, was also repressed by miR-10a in OA-FLSs. To summarize, the TWIST1-miR-10a-MAP3K7-NF-κB pathway mediates the development of synovitis in OA. miR-10a functions as an anti-inflammatory mediator in OA-FLS.

Identification of Novel Targets of Knee Osteoarthritis Shared by Cartilage and Synovial Tissue

Arthritis is the leading cause of disability among adults, while osteoarthritis (OA) is the most common form of arthritis that results in cartilage loss. However, accumulating evidence suggests that the protective hyaline cartilage should not be the sole focus of OA treatment. Particularly, synovium also plays essential roles in OA’s initiation and progression and warrants serious consideration when battling against OA. Thus, biomarkers with similar OA-responsive expressions in cartilage and synovium should be the potential targets for OA treatment. On the other hand, molecules with a distinguished response during OA in cartilage and synovium should be ruled out as OA therapeutic(s) to avoid controversial effects in different tissues. Here, to pave the path for developing a new generation of OA therapeutics, two published transcriptome datasets of knee articular cartilage and synovium were analyzed in-depth. Genes with statistically significantly different expression in OA and healthy cartilage were compared with those in the synovium. Thirty-five genes with similar OA-responsive expression in both tissues were identified while recognizing three genes with opposite OA-responsive alteration trends in cartilage and synovium. These genes were clustered based on the currently available knowledge, and the potential impacts of these clusters in OA were explored.

Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations

Being the most common musculoskeletal progressive condition, osteoarthritis is an interesting target for research. It is estimated that the prevalence of knee osteoarthritis (OA) among adults 60 years of age or older is approximately 10% in men and 13% in women, making knee OA one of the leading causes of disability in elderly population. Today, we know that osteoarthritis is not a disease characterized by loss of cartilage due to mechanical loading only, but a condition that affects all of the tissues in the joint, causing detectable changes in tissue architecture, its metabolism and function. All of these changes are mediated by a complex and not yet fully researched interplay of proinflammatory and anti-inflammatory cytokines, chemokines, growth factors and adipokines, all of which can be measured in the serum, synovium and histological samples, potentially serving as biomarkers of disease stage and progression. Another key aspect of disease progression is the epigenome that regulates all the genetic expression through DNA methylation, histone modifications, and mRNA interference. A lot of work has been put into developing non-surgical treatment options to slow down the natural course of osteoarthritis to postpone, or maybe even replace extensive surgeries such as total knee arthroplasty. At the moment, biological treatments such as platelet-rich plasma, bone marrow mesenchymal stem cells and autologous microfragmented adipose tissue containing stromal vascular fraction are ordinarily used. Furthermore, the latter two mentioned cell-based treatment options seem to be the only methods so far that increase the quality of cartilage in osteoarthritis patients. Yet, in the future, gene therapy could potentially become an option for orthopedic patients. In the following review, we summarized all of the latest and most important research in basic sciences, pathogenesis, and non-operative treatment.

Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations

Being the most common musculoskeletal progressive condition, osteoarthritis is an interesting target for research. It is estimated that the prevalence of knee osteoarthritis (OA) among adults 60 years of age or older is approximately 10% in men and 13% in women, making knee OA one of the leading causes of disability in elderly population. Today, we know that osteoarthritis is not a disease characterized by loss of cartilage due to mechanical loading only, but a condition that affects all of the tissues in the joint, causing detectable changes in tissue architecture, its metabolism and function. All of these changes are mediated by a complex and not yet fully researched interplay of proinflammatory and anti-inflammatory cytokines, chemokines, growth factors and adipokines, all of which can be measured in the serum, synovium and histological samples, potentially serving as biomarkers of disease stage and progression. Another key aspect of disease progression is the epigenome that regulates all the genetic expression through DNA methylation, histone modifications, and mRNA interference. A lot of work has been put into developing non-surgical treatment options to slow down the natural course of osteoarthritis to postpone, or maybe even replace extensive surgeries such as total knee arthroplasty. At the moment, biological treatments such as platelet-rich plasma, bone marrow mesenchymal stem cells and autologous microfragmented adipose tissue containing stromal vascular fraction are ordinarily used. Furthermore, the latter two mentioned cell-based treatment options seem to be the only methods so far that increase the quality of cartilage in osteoarthritis patients. Yet, in the future, gene therapy could potentially become an option for orthopedic patients. In the following review, we summarized all of the latest and most important research in basic sciences, pathogenesis, and non-operative treatment.

Proteoglycan-4 regulates fibroblast to myofibroblast transition and expression of fibrotic genes in the synovium

Background

Synovial tissue fibrosis is common in advanced OA with features including the presence of stress fiber-positive myofibroblasts and deposition of cross-linked collagen type-I. Proteoglycan-4 (PRG4) is a mucinous glycoprotein secreted by synovial fibroblasts and is a major component of synovial fluid. PRG4 is a ligand of the CD44 receptor. Our objective was to examine the role of PRG4-CD44 interaction in regulating synovial tissue fibrosis in vitro and in vivo.

Methods

OA synoviocytes were treated with TGF-β ± PRG4 for 24 h and α-SMA content was determined using immunofluorescence. Rhodamine-labeled rhPRG4 was incubated with OA synoviocytes ± anti-CD44 or isotype control antibodies and cellular uptake of rhPRG4 was determined following a 30-min incubation and α-SMA expression following a 24-h incubation. HEK-TGF-β cells were treated with TGF-β ± rhPRG4 and Smad3 phosphorylation was determined using immunofluorescence and TGF-β/Smad pathway activation was determined colorimetrically. We probed for stress fibers and focal adhesions (FAs) in TGF-β-treated murine fibroblasts and fibroblast migration was quantified ± rhPRG4. Synovial expression of fibrotic markers: α-SMA, collagen type-I, and PLOD2 in Prg4 gene-trap (Prg4^GT) and recombined Prg4^GTR animals were studied at 2 and 9 months of age. Synovial expression of α-SMA and PLOD2 was determined in 2-month-old Prg4^GT/GT&Cd44^−/− and Prg4^GTR/GTR&Cd44^−/− animals.

Results

PRG4 reduced α-SMA content in OA synoviocytes (p < 0.001). rhPRG4 was internalized by OA synoviocytes via CD44 and CD44 neutralization attenuated rhPRG4’s antifibrotic effect (p < 0.05). rhPRG4 reduced pSmad3 signal in HEK-TGF-β cells (p < 0.001) and TGF-β/Smad pathway activation (p < 0.001). rhPRG4 reduced the number of stress fiber-positive myofibroblasts, FAs mean size, and cell migration in TGF-β-treated NIH3T3 fibroblasts (p < 0.05). rhPRG4 inhibited fibroblast migration in a macrophage and fibroblast co-culture model without altering active or total TGF-β levels. Synovial tissues of 9-month-old Prg4^GT/GT animals had higher α-SMA, collagen type-I, and PLOD2 (p < 0.001) content and Prg4 re-expression reduced these markers (p < 0.01). Prg4 re-expression also reduced α-SMA and PLOD2 staining in CD44-deficient mice.

Conclusion

PRG4 is an endogenous antifibrotic modulator in the joint and its effect on myofibroblast formation is partially mediated by CD44, but CD44 is not required to demonstrate an antifibrotic effect in vivo.

Transcriptional profiling of murine macrophages stimulated with cartilage fragments revealed a strategy for treatment of progressive osteoarthritis

Accumulating evidence suggests that synovitis is associated with osteoarthritic process. Macrophages play principal role in development of synovitis. Our earlier study suggests that interaction between cartilage fragments and macrophages exacerbates osteoarthritic process. However, molecular mechanisms by which cartilage fragments trigger cellular responses remain to be investigated. Therefore, the current study aims at analyzing molecular response of macrophages to cartilage fragments. To this end, we analyzed the transcriptional profiling of murine macrophages exposed to cartilage fragments by RNA sequencing. A total 153 genes were differentially upregulated, and 105 genes were down-regulated in response to cartilage fragments. Bioinformatic analysis revealed that the most significantly enriched terms of the upregulated genes included scavenger receptor activity, integrin binding activity, TNF signaling, and toll-like receptor signaling. To further confirm our results, immunohistochemical staining was performed to detected regulated molecules in synovial tissues of OA patients. In consistence with RNA-seq results, MARCO, TLR2 and ITGα5 were mainly detected in the intima lining layer of synovial tissues. Moreover, blockade of TLR2 or ITGα5 but not Marco using specific antibody significantly reduced production of TNF-α in stimulated macrophages by cartilage fragments. Our data suggested that blocking TLR2 or ITGα5 might be promising therapeutic strategy for treating progressive osteoarthritis.

Functional analysis of synovial fluid from osteoarthritic knee and carpometacarpal joints unravels different molecular profiles

OBJECTIVE

In this work, we aimed to elucidate the molecular mechanisms driving primary OA. By studying the dynamics of protein expression in two different types of OA joints we searched for similarities and disparities to identify key molecular mechanisms driving OA.

METHODS

For this purpose, human SF samples were obtained from CMC-I OA and knee joint of OA patients. SF samples were analysed by label-free quantitative liquid chromatography mass spectrometry. Disease-relevant proteins identified in proteomics studies, such as clusterin, paraoxonase/arylesterase 1 (PON1) and transthyretin were validated by enzyme-linked immunosorbent assays, and on the mRNA level by droplet digital PCR. Functional studies were performed in vitro using primary chondrocytes.

RESULTS

Differential proteomic changes were observed in the concentration of 40 proteins including clusterin, PON1 and transthyretin. Immunoassay analyses of clusterin, PON1, transthyretin and other inflammatory cytokines confirmed significant differences in protein concentration in SF of CMC-I and knee OA patients, with primarily lower protein expression levels in CMC-I. Functional studies on chondrocytes unequivocally demonstrated that stimulation with SF obtained from knee OA, in contrast to CMC-I OA joint, caused a significant upregulation in pro-inflammatory response, cell death and hypertrophy.

CONCLUSION

This study demonstrates that differential expression of molecular players in SF from different OA joints evokes diverse effects on primary chondrocytes. The pathomolecular mechanisms of OA may significantly differ in various joints, a finding that brings a new dimension into the pathogenesis of primary OA.

Cartilage Wear Particles Induce an Inflammatory Response Similar to Cytokines in Human Fibroblast-Like Synoviocytes

The synovium plays a key role in the development of osteoarthritis, as evidenced by pathological changes to the tissue observed in both early and late stages of the disease. One such change is the attachment of cartilage wear particles to the synovial intima. While this phenomenon has been well observed clinically, little is known of the biological effects that such particles have on resident cells in the synovium. The present work investigates the hypothesis that cartilage wear particles elicit a pro-inflammatory response in diseased and healthy human fibroblast-like synoviocytes, like that induced by key cytokines in osteoarthritis. Fibroblast-like synoviocytes from 15 osteoarthritic human donors and a subset of three non-osteoarthritic donors were exposed to cartilage wear particles, interleukin-1α or tumor necrosis factor-α for 6 days and analyzed for proliferation, matrix production, and release of pro-inflammatory mediators and degradative enzymes. Wear particles significantly increased proliferation and release of nitric oxide, interleukin-6 and -8, and matrix metalloproteinase-9, -10, and -13 in osteoarthritic synoviocytes, mirroring the effects of both cytokines, with similar trends in non-osteoarthritic cells. These results suggest that cartilage wear particles are a relevant physical factor in the osteoarthritic environment, perpetuating the pro-inflammatory and pro-degradative cascade by modulating synoviocyte behavior at early and late stages of the disease. Future work points to therapeutic strategies for slowing disease progression that target cell-particle interactions. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1979-1987, 2019.

Local intra-articular injection of rapamycin inhibits NLRP3 activity and prevents osteoarthritis in mouse DMM models

This study investigated the influence of autophagy on the expression of Collagen type II and light chain 3 (LC-3) in the articular cartilage of osteoarthritis (OA) models. The expression of OA associated biomarkers namely Matrix metalloproteinase (MMP-13), NOD-, LRR- and pyrin domain-containing 3 (NLRP3) induced by destabilizing the medial meniscus operation (DMM) were also investigated. A total of 60 C57BL/6 mice were divided into (1) control; (2) DMM2; (3) DMM8; (4) rapamycin 2 weeks; and (5) rapamycin 8 weeks groups. Saffranin O-Fast green staining, histomorphometry and immunohistochemical methods were used for analysis. In the DMM group, the expression of the OA biomarkers MMP-13, NLRP3 significantly increased, whilst Collagen II and LC-3B levels were significantly lower than other experimental groups. We hypothesized that NLRP3 inhibits autophagy activation and delays disease progression.

Beyond Cartilage Repair: The Role of the Osteochondral Unit in Joint Health and Disease

Once believed to be limited to articular cartilage, osteoarthritis is now considered to be an organ disease of the “whole joint.” Damage to the articular surface can lead to, be caused by, or occur in parallel with, damage to other tissues in the joint. The relationship between cartilage and the underlying subchondral bone has particular importance when assessing joint health and determining treatment strategies. The articular cartilage is anchored to the subchondral bone through an interface of calcified cartilage, which as a whole makes up the osteochondral unit. This unit functions primarily by transferring load-bearing weight over the joint to allow for normal joint articulation and movement. Unfortunately, irreversible damage and degeneration of the osteochondral unit can severely limit joint function. Our understanding of joint pain, the primary complaint of patients, is poorly understood and past efforts toward structural cartilage restoration have often not been associated with a reduction in pain. Continued research focusing on the contribution of subchondral bone and restoration of the entire osteochondral unit are therefore needed, with the hope that this will lead to curative, and not merely palliative, treatment options. The purpose of this narrative review is to investigate the role of the osteochondral unit in joint health and disease. Topics of discussion include the crosstalk between cartilage and bone, the efficacy of diagnostic procedures, the origins of joint pain, current and emerging treatment paradigms, and suitable preclinical animal models for safety and efficacy assessment of novel osteochondral therapies. The goal of the review is to facilitate an appreciation of the important role played by the subchondral bone in joint pain and why the osteochondral unit as a whole should be considered in many cases of joint restoration strategies.

Intraarticular injection of a Tin-117 m radiosynoviorthesis agent in normal canine elbows causes no adverse effects

This longitudinal prospective exploratory study used serial measurements in five dogs to evaluate safety and retention of a tin-117 m (^117m Sn) colloid after intra-articular injection in normal elbow joints. Each dog was deemed healthy based on physical examination, laboratory results, and radiographic evaluation of both elbows. While anesthetized, each received an MRI of both elbows, followed by fluorine-18 fluorodeoxyglucose positron emission tomography scans of both elbow joints and associated lymph nodes. Joint fluid (0.5-1.0 mL) was withdrawn aseptically from the left elbow joint, followed by intra-articular injection of ^117m Sn colloid (92.5 MBq; 1-1.5 ml). Post-injection assessments included blood counts, serum chemistry panels, urinalyses, radiographs, joint fluid analyses, MRI/positron emission tomography scans, scintigraphy, and biodistribution scans. On day 45-47, each dog was euthanized and a complete postmortem examination was performed. Tissue samples were submitted for histopathology and radioisotope retention studies. Left elbow joints were decalcified and sectioned for future autoradiography. Scintigraphy, 1 day after injection, indicated slight radioisotope escape from the joint to regional lymph nodes. Serial blood, urine, feces, and organ counts indicated >99.1% of the ^117m Sn activity was retained in the joint for 45-47 days. Radiation output levels were below patient release levels the day following injection. Maximum standard uptake value for the injected joint decreased. Joint fluid cytology was unchanged. No dog exhibited lameness during the study. Absence of joint damage and lack of systemic effects after injection of the ^117m Sn colloid in normal canine elbow joints indicate that this agent may be safely used for radiosynoviorthesis in dogs with osteoarthritis.

Vascular Pathology and Osteoarthritis: A Systematic Review

OBJECTIVE

Vascular pathology (changes in blood vessels) and osteoarthritis (OA) are both common chronic conditions associated with aging and obesity, but whether vascular pathology is a risk factor for OA is unclear. The aim of this study was to systematically review the evidence for an association between vascular pathology and risk of joint-specific OA.

METHODS

Scopus, Ovid Medline, and EMBASE were searched from inception to February 2019. MeSH terms and keywords were used to identify studies examining the association between vascular pathology and OA. Two reviewers independently extracted the data and assessed the methodological quality. Qualitative evidence synthesis was performed.

RESULTS

Fifteen studies with high (n = 3), fair (n = 3), or low (n = 9) quality were included. Features of vascular pathology included atherosclerosis, vascular stiffness, and endothelial dysfunction in different vascular beds. There was evidence for an association between vascular pathology and risk of hand OA in women but not men, and between vascular pathology and risk of knee OA in both men and women. Only 2 studies examined hip OA showing no association between vascular pathology and risk of hip OA.

CONCLUSION

There is evidence suggesting an association between vascular pathology and risk of hand and knee OA, with a potential causal relationship for knee OA. Based on the limited evidence, it is hard to conclude an association for hip OA. Further stronger evidence is needed to determine whether there is a causal relationship.

Interleukin-34 as a promising clinical biomarker and therapeutic target for inflammatory arthritis

Interleukin-34 (IL-34), recently identified as a novel inflammatory cytokine and the second ligand for colony-stimulating factor-1 receptor, is known to play regulatory roles in the development, maintenance, and function of mononuclear phagocyte lineage cells - especially osteoclasts. Regarding its primary effect on osteoclasts, IL-34 has been shown to stimulate formation and activation of osteoclasts, which in turn magnifies osteoclasts-resorbing activity. In addition to its role in osteoclastogenesis, IL-34 has been implicated in inflammation of synovium via augmenting production of inflammatory mediators, in which altered IL-34 expression is regulated by pro-inflammatory cytokines responsible for cartilage degradation. Indeed, IL-34 has been documented to be highly expressed in inflamed synovium of rheumatoid arthritis (RA) and knee osteoarthritis (OA) patients, which are recognized as inflammatory arthritis. Furthermore, a number of clinical studies demonstrated that IL-34 levels were significantly increased in the circulation and synovial fluid of patients with RA and knee OA. Its levels were also found to be positively associated with disease severity - especially radiographic severity of both RA and knee OA patients. Interestingly, emerging evidence has accumulated that functional blockage of IL-34 with specific antibody can alleviate the severity of inflammatory arthritis. It is therefore reasonable to speculate that IL-34 may be developed as a potential biomarker and a new therapeutic candidate for inflammatory arthritis. To date, there are numerous studies showing IL-34 involvement and association with many aspects of inflammatory arthritis. Herein, this review aimed to summarize the recent findings regarding regulatory role of IL-34 in synovial inflammation-mediated cartilage destruction and update the current comprehensive knowledge on usefulness of IL-34-based treatment in inflammatory arthritis - particularly RA and knee OA.

Pharmacokinetic Profile of Intra-articular Fluticasone Propionate Microparticles in Beagle Dog Knees

OBJECTIVE

The objective of this pilot study was to determine time point(s) at which maximum concentration of fluticasone propionate (Cmax) occurs in synovial fluid and plasma in Beagle dog knees after intra-articular injection of EP-104IAR.

DESIGN

EP-104IAR is composed of fluticasone propionate drug crystals coated with heat-treated polyvinyl alcohol (PVA) to result in extended release properties. Thirty-two Beagle dogs had an injection of EP-104IAR into the knee joint at 2 different dose levels (0.6 mg and 12 mg). Outcome measures included plasma, synovial fluid, and articular cartilage fluticasone propionate concentrations as well as histological analysis of cartilage and synovium at a variety of time points up to 58 days postdosing.

RESULTS

Intra-articular administration of 0.6 and 12 mg EP-104IAR was well tolerated. Early minor abnormalities found on microscopy resolved by the end of the study. There were no quantifiable concentrations of fluticasone propionate in plasma of animals administered 0.6 mg at any of the sampling time points. Highest concentrations in plasma following 12 mg administration occurred 1 day postdose and declined with a half-life of approximately 45 days. Highest concentrations of fluticasone propionate in synovial fluid and cartilage generally occurred 5 days postdose in both dose groups and declined with a half-life of approximately 11 to 14 days.

CONCLUSIONS

EP-104IAR is capable of providing a safe and prolonged local exposure to a corticosteroid in the synovial joint while minimizing systemic exposure, with peak exposures occurring within a matter of days after dosing before declining in all tissues in a predictable manner.

A Functional Tissue-Engineered Synovium Model to Study Osteoarthritis Progression and Treatment

IMPACT STATEMENT

The synovium envelops the diarthrodial joint and plays a key regulatory role in defining the composition of the synovial fluid through filtration and biosynthesis of critical boundary lubricants. Synovium changes often precede cartilage damage in osteoarthritis. We describe a novel in vitro tissue engineered model, validated against native synovium explants, to investigate the structure-function of synovium through quantitative solute transport measures. Synovium was evaluated in the presence of a proinflammatory cytokine, interleukin-1, or the clinically relevant corticosteroid, dexamethasone. We anticipate that a better understanding of synovium transport would support efforts to develop more effective strategies aimed at restoring joint health.