Osteoarthritis: can anti-cytokine therapy play a role in treatment?

Interleukin-37 Inhibits Interleukin-1β-Induced Articular Chondrocyte Apoptosis by Suppressing Reactive Oxygen Species

Objective: Chondrocyte apoptosis has been considered a crucial mechanism that is responsible for cartilage destruction in osteoarthritis (OA). The mechanism of interleukin-37 (IL-37) on chondrocyte apoptosis has not been clearly determined in the pathogenesis of OA. Here, we explored the role of IL-37 in the regulation of cellular apoptosis in rat chondrocytes stimulated by IL-1β. Methods: Rat chondrocytes were used in in vitro study, and were stimulated with IL-1β (10 ng/mL) and/or recombinant IL-37 (rIL-37; 100 ng/mL) after cytotoxicity assessments using these cytokines were conducted. After rIL-37 treatment of chondrocytes stimulated with IL-1β, the cell proliferation assay, apoptosis assays, including expression of mitochondrial apoptosis-related markers, flow cytometry analysis of annexin V-FITC/propidium iodide (PI), cell cycle analysis, and Hoechst 33342 staining, and reactive oxygen species (ROS) measurement were used. Results: IL-1β induced expression of inflammatory cytokines and triggered degradation of the extracellular matrix of rat chondrocytes, but this effect was significantly attenuated by rIL-37 treatment. Enhanced ROS generation following IL-1β stimulation was reduced in a dose-dependent manner after stimulation with rIL-37. IL-1β induced pro-apoptotic markers and suppressed anti-apoptotic markers in rat chondrocytes. Flow cytometry using annexin V-FITC/PI revealed that IL-1β increased the apoptosis rate of rat chondrocytes, and that this effect was markedly reversed by treatment with rIL-37. Conclusions: IL-37 potently attenuated IL-1β-mediated apoptosis of rat chondrocytes by blocking ROS production. This study suggests that IL-37 can serve as a novel anti-cytokine therapy in OA by blocking chondrocyte apoptosis.

Elucidation of the key therapeutic targets and potential mechanisms of Andrographolide multi-targets against osteoarthritis via network pharmacological analysis and experimental validation

OBJECTIVE

Our purpose is to unveil Andrographolide's potential multi-target and multi-mechanism therapeutic effects in treating OA via systematic network pharmacological analysis and cell experimental validation.

MATERIALS AND METHODS

Initially, we gathered data from Andrographolide and OA-related databases to obtain information on Andrographolide's biological properties and the targets linked with OA. We developed a bioinformatic network about Andrographolide and OA, whereby we analyzed the network to identify potential therapeutic targets and mechanisms of action of Andrographolide. Subsequently, we used molecular docking to analyze the binding sites of Andrographolide to the target proteins. At the same time, SDF-1 was used to construct an OA cell model to verify the therapeutic effect of Andrographolide on OA and its effect on target proteins.

RESULTS

Our experimental results show that Andrographolide has excellent pharmaceutical properties, by Lipinski's rules for drugs, suggesting that this compound can be considered to have a high therapeutic potential in drug development. 233 targets were preliminarily investigated, the mechanisms through which Andrographolide targets OA primarily involve the TNF signaling pathway, PI3K-AKT signaling pathway, IL-17 signaling pathway, and TLR signaling pathway. These mechanisms target OA by influencing immune and inflammatory responses in the joints, regulating apoptosis to prevent chondrocyte death. Finally, TNF-α, STAT3, TP53, IL-6, JUN, IL-1β, HIF-1α, TGF-β1, and AKT1 were identified as 9 key targets of Andrographolide anti-OA. In addition, our molecular docking analyzes with cell experimental validation further confirm the network pharmacology results. According to our molecular docking results, Andrographolide can bind to all the hub target proteins and has a good binding ability (binding energy < -5 kcal/mol), with the strongest binding affinity to AKT1 of -9.2 kcal/ mol. The results of cell experiments showed that Andrographolide treatment significantly increased the cell viability and the expression of COL2A1 and ACAN proteins. Moreover, 30 μM Andrographolide significantly reversed SDF-1-induced increases in the protein expression of TNF-α, STAT3, TP53, IL-6, JUN, IL-1β, HIF-1α, and TGF-β1, and decreases in the protein expression of AKT1.

CONCLUSION

This study provides a comprehensive understanding of the potential therapeutic targets and mechanisms of action of Andrographolide in OA treatment. Our findings suggest that Andrographolide is a promising candidate for drug development in the management of OA.

Efficacy of Anti-Interleukin-1 Therapeutics in the Treatment of Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials from the Years 2000 to 2023

Objectives: This study aimed to evaluate the efficacy of anti-interleukin-1 therapeutics for treating knee osteoarthritis (KOA). Our research included interleukin-1 (IL-1) inhibitors, IL-1 antibodies and IL-1 receptor antagonists (IL-1 Ras). Methods: We systematically searched PubMed and Mendeley to find randomized control trials (RCTs) or clinical trials (CTs) of anti-interleukin-1 therapeutics in KOA from 2000 to 2023. The outcomes were changes in pain, function and stiffness scores. The research was conducted between November 2023 and January 2024. The risk of bias was assessed using Cochrane Risk of Bias tool RoB 2. Results: Analysis of the nine included studies showed a statistically significant difference in terms of the pain relief group (SMD = -0.20, 95% CI: -0.39 to -0.01, p = 0.0348), physical function improvement (SMD = -0.20, 95% CI: -0.39 to 0.00, p = 0.0479) and stiffness reduction (SMD = -0.22, 95% CI: -0.43 to 0.00, p = 0.0475) between anti-IL-1 therapeutics and placebo or nonsteroidal anti-inflammatory drugs (NSAIDs). However, when we separately analysed placebo and NSAIDs subgroups, the statistical significance was observed only in the placebo group. Our article was limited by the quality of the included RCTs. Two of the included trials were of poor methodological quality, and five showed selective reporting. Conclusions: The results of our study suggest that anti-IL-1 therapeutics might have better efficacy in KOA treatment than placebo or NSAIDs; yet, taking into account the limited availability of studies and data concerning anti-IL-1 in osteoarthritis treatment, we think that more high-quality RCTs on this subject are needed.

A cytokine-induced spheroid-based in vitro model for studying osteoarthritis pathogenesis

Given the lack of in vitro models faithfully reproducing the osteoarthritis (OA) disease on-set, this work aimed at manufacturing a reliable and predictive in vitro cytokine-based Articular Cartilage (AC) model to study OA progression. Cell spheroids of primary human fetal chondrocytes (FCs) and h-TERT mesenchymal stem cells differentiated chondrocytes (Y201-C) were analysed in terms of growth kinetics, cells proliferation and apoptosis over 10 days of culture, in healthy condition or in presence of cytokines (interleukin-1ß, -6 and TNF-α). Then, the spheroids were assembled into chondrospheres using a bottom-up strategy, to obtain an in vitro cytokines-induced OA model. The resulting chondrospheres were evaluated for gene expression and anabolic ECM proteins. Compared to the healthy environment, the simulated OA environment induced chondrocyte hyperproliferation and apoptotic pathway, decreased expression of anabolic ECM proteins, and diminished biosynthetic activity, resembling features of early-stage OA. These characteristics were observed for both Y201-C and HC at high and low concentrations of cytokines. Both HC and Y201-C demonstrated the suitability for the manufacturing of a scaffold-free in vitro OA model to facilitate studies into OA pathogenesis and therapeutic strategies. Our approach provides a faithful reproduction of early-stage osteoarthritis, demonstrating the ability of obtaining different disease severity by tuning the concentration of OA-related cytokines. Given the advantages in easy access and more reproducible performance, Y201-C may represent a more favourable source of chondrocytes for establishing more standardized protocols to obtain OA models.

Synovial fibroblasts assume distinct functional identities and secrete R-spondin 2 in osteoarthritis

OBJECTIVES

Synovium is acutely affected following joint trauma and contributes to post-traumatic osteoarthritis (PTOA) progression. Little is known about discrete cell types and molecular mechanisms in PTOA synovium. We aimed to describe synovial cell populations and their dynamics in PTOA, with a focus on fibroblasts. We also sought to define mechanisms of synovial Wnt/β-catenin signalling, given its emerging importance in arthritis.

METHODS

We subjected mice to non-invasive anterior cruciate ligament rupture as a model of human joint injury. We performed single-cell RNA-sequencing to assess synovial cell populations, subjected Wnt-GFP reporter mice to joint injury to study Wnt-active cells, and performed intra-articular injections of the Wnt agonist R-spondin 2 (Rspo2) to assess whether gain of function induced pathologies characteristic of PTOA. Lastly, we used cultured fibroblasts, macrophages and chondrocytes to study how Rspo2 orchestrates crosstalk between joint cell types.

RESULTS

We uncovered seven distinct functional subsets of synovial fibroblasts in healthy and injured synovium, and defined their temporal dynamics in early and established PTOA. Wnt/β-catenin signalling was overactive in PTOA synovium, and Rspo2 was strongly induced after injury and secreted exclusively by Prg4^hi lining fibroblasts. Trajectory analyses predicted that Prg4^hi lining fibroblasts arise from a pool of Dpp4+ mesenchymal progenitors in synovium, with SOX5 identified as a potential regulator of this emergence. We also showed that Rspo2 orchestrated pathological crosstalk between synovial fibroblasts, macrophages and chondrocytes.

CONCLUSIONS

Synovial fibroblasts assume distinct functional identities during PTOA in mice, and Prg4^hi lining fibroblasts secrete Rspo2 that may drive pathological joint crosstalk after injury.

Bibliometric and visualization analysis of macrophages associated with osteoarthritis from 1991 to 2021

Background

Macrophages significantly contributes to symptomology and structural progression of osteoarthritis (OA) and raise increasing attention in the relative research field. Recent studies have shown that tremendous progress has been made in the research of macrophages associated with osteoarthritis. However, a comprehensive bibliometric analysis is lacking in this research field. This study aimed to introduce the research status as well as hotspots and explore the field of macrophages research in OA from a bibliometric perspective.

Methods

This study collected 1481 records of macrophages associated with osteoarthritis from 1991 to 2021 in the web of science core collection (WoSCC) database. CiteSpace, VOSviewer, and R package “bibliometrix” software were used to analyze regions, institutions, journals, authors, and keywords to predict the latest trends in macrophages associated with osteoarthritis research.

Results

The number of publications related to macrophages associated with osteoarthritis is increasing annually. China and the USA, contributing more than 44% of publications, were the main drivers for research in this field. League of European Research Universities was the most active institution and contributed the most publications. Arthritis and Rheumatism is the most popular journal in this field with the largest publications, while Osteoarthritis and Cartilage is the most co-cited journal. Koch AE was the most prolific writer, while Bondeson J was the most commonly co-cited author. “Rheumatology”, “Orthopedics”, and “Immunology” were the most widely well-represented research areas of OA associated macrophages. “Rheumatoid arthritis research”, “clinical symptoms”, “regeneration research”, “mechanism research”, “pathological features”, and “surgery research” are the primary keywords clusters in this field.

Conclusion

This is the first bibliometric study comprehensively mapped out the knowledge structure and development trends in the research field of macrophages associated with osteoarthritis in recent 30 years. The results comprehensively summarize and identify the research frontiers which will provide a reference for scholars studying macrophages associated with osteoarthritis.

The influence of IL-1 and C-reactive protein levels in synovial fluid of companion dogs with bilateral hip osteoarthritis on various clinical disease parameters

OBJECTIVE

To evaluate IL-1 and C-reactive protein (CRP) levels in the synovial fluid in dogs with bilateral hip osteoarthritis and their relation to animals' clinical, radiographic, and thermographic disease signs.

SAMPLE

100 joints from police working dogs.

PROCEDURES

Synovial fluid, IL-1, and CRP levels, weight distribution, joint range of motion, thigh girth, digital thermography, and radiographic signs of the joints were recorded. Data from 4 clinical metrology instruments (CMIs) were collected. Results were compared by age, sex, and Orthopedic Foundation for Animals hip scores with the independent samples t test, ANOVA, and Pearson correlation coefficient (P < .05).

RESULTS

The sample included 100 pelvic limbs, equally distributed between left and right pelvic limbs 30 males and 20 females, with a mean age of 6.5 ± 2.4 years and body weight of 26.7 ± 5.2 kg. IL-1 levels, particularly above 200 pg/mL, may be related to the development of caudolateral curvilinear osteophyte, which then expresses a toll on the patient's levels of pain and activity. It was unclear if the CRP levels were a consequence of inflammatory activity within the joint or a reflection of a better prognosis. Increasing body weight was related to worse CMI scores.

CLINICAL RELEVANCE

We described the relation of IL-1 and CRP synovial concentration levels with several clinical signs, diagnostic imaging, laboratory findings, and CMI results of animals with osteoarthritis. Further studies are required to determine the interest of each parameter for the prognosis and treatment monitoring.

Long-term intake of Lilium lancifolium mitigated osteoarthritic effects by suppressing inflammatory cytokines in a dog model

Background and Aim: Osteoarthritis (OA) is a chronic, painful, degenerative inflammatory disease of the synovial joints. Regular use of nonsteroidal anti-inflammatory drugs to decrease OA pain can have severe side effects, such as gastric irritation, ulcers, and heart problems. Natural products are extensively used to minimize OA-associated pain and inflammatory reactions. Lilium lancifolium is commonly used to alleviate several diseases through its anti-inflammatory effects. This study examined the impact of L. lancifolium extract on alleviating pain and inflammation associated with articular cartilage damage. Materials and Methods: Hydro-ethanol extracts of the L. lancifolium bulb were used. The experimental animals (adult beagle dogs) were divided into four groups: sham, which received neither treatment nor surgery; placebo, which received an empty gelatin capsule; glucosamine, which received glutamine (60 mg/kg); and L. lancifolium, which received an L. lancifolium extract-filled (60 mg/kg) gelatin capsule for 8 weeks. OA was induced by an expert orthopedic surgeon in 2-year-old dogs through resection of cranial cruciate ligament and lateral collateral ligament. Inflammatory cytokines, enzymes, lameness score, radiology, and histological changes were assessed. Results: Our experiments showed that long-term oral therapy with L. lancifolium alleviated inflammation and increased histological damage. L. lancifolium treatment effectively reduced cytokines, such as interleukin-6, metalloproteinase-9, leukotriene-4, prostaglandin, and cyclo-oxygenase in dogs with OA, suggesting the potential to minimize inflammatory reactions in OA. L. lancifolium showed anti-inflammatory qualities in dogs with OA. This effect was comparable with that of glucosamine OA treatment. Conclusion: L. lancifolium supplementation represents a possible therapeutic and management option in this model of OA.

Therapeutic Effects of Live Lactobacillus plantarum GKD7 in a Rat Model of Knee Osteoarthritis

Osteoarthritis (OA) is a painful, progressive chronic inflammatory disease marked by cartilage destruction. Certain synovial inflammatory cytokines, such as IL-1β and TNF-α, promote OA inflammation and pain. Lactobacillus spp. is a well-known probiotic with anti-inflammatory, analgesic, antioxidant, and antiosteoporotic properties. This study evaluated the therapeutic effects of a live L. plantarum strain (GKD7) in the anterior cruciate ligament transection (ACLT)-induced OA rat model. The results show that oral administration of live L. plantarum GKD7 improved weight-bearing asymmetry after ACLT surgery. Moreover, micro-computed tomography images and histopathological analysis show that oral live L. plantarum GKD7 improved subchondral bone architecture, protected articular cartilage against ACLT-induced damage, and reduced synovial inflammation. L. plantarum GKD7 also reduced IL-1β and TNF-α production in OA cartilage and synovium. Thus, orally administered live L. plantarum GKD7 appears to effectively slow the progression of OA.

Use of allogeneic freeze-dried conditioned serum for the prevention of degradation in cartilage exposed to IL-1ß

Background

Autologous conditioned serum (ACS) has been extensively used in the field of veterinary orthopaedics and sports medicine. Due to the autologous and blood-derived nature of this product, issues such as individual variability, need for storage at low temperatures and non-availability for immediate are frequently encountered for ACS use in the field. To address those issues, we proposed the evaluation of an off-the-shelf allogeneic freeze-dried version of conditioned serum in an in vitro model of osteoarthritis. In this study, we evaluated if origin (autologous and allogeneic) and preparation (frozen and freeze-dried) of conditioned serum could influence in its effect in an in vitro model.

Results

IL-1β stimulation in cartilage led to a significant increase in media GAG and decreased levels of GAG in cartilage explants at the termination of the experiment. No significant differences were noted in outcomes measured in the cartilage explants with respect to the main effects of treatment (frozen versus freeze-dried serum), autologous versus allogeneic preparations or based on serum concentration.

Conclusions

The study did not observe any substantial differences in the response of cartilage to allogeneic freeze-dried CS when compared to other independent parameters (autologous and frozen preparations). Further investigation using in vivo systems appears warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03227-2.

Effect of Human Synovial Fluid From Osteoarthritis Patients and Healthy Individuals on Lymphatic Contractile Activity

The lymphatic system has been proposed to play a crucial role in preventing the development and progression of osteoarthritis (OA). As OA develops and progresses, inflammatory cytokines and degradation by-products of joint tissues build up in the synovial fluid (SF) providing a feedback system to exacerbate disease. The lymphatic system plays a critical role in resolving inflammation and maintaining overall joint homeostasis; however, there is some evidence that the lymphatics can become dysfunctional during OA. We hypothesized that the functional mechanics of lymphatic vessels (LVs) draining the joint could be directly compromised due to factors within SF derived from osteoarthritis patients (OASF). Here, we utilized OASF and SF derived from healthy (non-OA) individuals (healthy SF (HSF)) to investigate potential effects of SF entering the draining lymph on migration of lymphatic endothelial cells (LECs) in vitro, and lymphatic contractile activity of rat femoral LVs (RFLVs) ex vivo. Dilutions of both OASF and HSF containing serum resulted in a similar LEC migratory response to the physiologically endothelial basal medium-treated LECs (endothelial basal medium containing serum) in vitro. Ex vivo, OASF and HSF treatments were administered within the lumen of isolated LVs under controlled pressures. OASF treatment transiently enhanced the RFLVs tonic contractions while phasic contractions were significantly reduced after 1 h of treatment and complete ceased after overnight treatment. HSF treatment on the other hand displayed a gradual decrease in lymphatic contractile activity (both tonic and phasic contractions). The observed variations after SF treatments suggest that the pump function of lymphatic vessel draining the joint could be directly compromised in OA and thus might present a new therapeutic target.

Platelet Rich Plasma Versus Autologous Conditioned Serum in Osteoarthritis of the Knee: Clinical Results of a Five-Year Retrospective Study

Objectives: There is no consensus on the effectiveness of platelet-rich plasma (PRP) and autologous conditioned serum (ACS) in the treatment of knee osteoarthritis (OA). Also, the group of patients who will benefit most from this treatment is not clear. This study aims to understand the effects of two treatment modalities: ACS and PRP on pain and clinical scores in the treatment of OA. For this reason, we compared the long-term (five-year follow up) clinical results of the patients to whom these two treatment methods were applied.

Materials and methods: Eighty-two knee osteoarthritis cases, selected from a database prospectively maintained in our tertiary university hospital after institutional ethics committee approval, examined between January 2013 and September 2020 and treated with ACS and PRP by the same orthobiological treatment team, were retrospectively analyzed. The clinical results of group A (n=40) treated with ACS and group B (n=42) treated with PRP were statistically analyzed. Clinical evaluations were made pre-injection and at one, six, 12, 24 and 60 months post-treatment, using the knee injury and osteoarthritis result score (KOOS) for the evaluation of function and a visual analog scale (VAS) for the evaluation of pain.

Results: Side effects were noted in two patients (5%) in group A and 16 patients (38.1%) in group B. More side effects were seen in group B compared to group A (p<0.001). The better VAS scores in both groups were detected in the sixth and 12th months. When VAS scores were examined, better results were obtained in group A in the 12th and 24th months (p<0.05). When KOOS scores were examined, the superiority of ACS to PRP at 12 and 24 months was shown in KOOS.S, KOOS.P and KOOS.ADL scores (p<0.05). There was no statistically significant difference between the two groups in terms of all scores and baseline scores at 60 months.

Conclusion: The effectiveness of ACS and PRP treatments can last up to two years. After two years, the effectiveness of both treatments decreases. Comparing the two treatments, ACS treatment showed better results on VAS and KOOS scores compared to PRP treatment.

The Added Value of the “Co” in Co-Culture Systems in Research on Osteoarthritis Pathology and Treatment Development

Osteoarthritis (OA) is a highly prevalent disease and a major health burden. Its development and progression are influenced by factors such as age, obesity or joint overuse. As a whole organ disease OA affects not only cartilage, bone and synovium but also ligaments, fatty or nervous tissue surrounding the joint. These joint tissues interact with each other and understanding this interaction is important in developing novel treatments. To incorporate and study these interactions in OA research, several co-culture models have evolved. They combine two or more cell types or tissues and investigate the influence of amongst others inflammatory or degenerative stimuli seen in OA. This review focuses on co-cultures and the differential processes occurring in a given tissue or cell as a consequence of being combined with another joint cell type or tissue, and/or the extent to which a co-culture mimics the in vivo processes. Most co-culture models depart from synovial lining and cartilage culture, but also fat pad and bone have been included. Not all of the models appear to reflect the postulated in vivo OA pathophysiology, although some of the discrepancies may indicate current assumptions on this process are not entirely valid. Systematic analysis of the mutual influence the separate compartments in a given model exert on each other and validation against in vivo or ex vivo observation is still largely lacking and would increase their added value as in vitro OA models.

The potential roles of JAK/STAT signaling in the progression of osteoarthritis

Osteoarthritis (OA) is an age-related chronic progressive degenerative disease that induces persistent pain and disabilities. The development of OA is a complex process, and the risk factors are various, including aging, genetics, trauma and altered biomechanics. Inflammation and immunity play an important role in the pathogenesis of OA. JAK/STAT pathway is one of the most prominent intracellular signaling pathways, regulating cell proliferation, differentiation, and apoptosis. Inflammatory factors can act as the initiators of JAK/STAT pathway, which is implicated in the pathophysiological activity of chondrocyte. In this article, we provide a review on the importance of JAK/STAT pathway in the pathological development of OA. Potentially, JAK/STAT pathway becomes a therapeutic target for managing OA.

Reprogrammed Synovial Fluid-Derived Mesenchymal Stem/Stromal Cells Acquire Enhanced Therapeutic Potential for Articular Cartilage Repair

OBJECTIVES

Functions of mesenchymal stem/stromal cells (MSCs) are affected by patient-dependent factors such as age and health condition. To tackle this problem, we used the cellular reprogramming technique to epigenetically alter human MSCs derived from the synovial fluid of joints with osteoarthritis (OA) to explore the potential of reprogrammed MSCs for repairing articular cartilage.

MATERIALS AND METHODS

MSCs isolated from the synovial fluid of three patients' OA knees (Pa-MSCs) were reprogrammed through overexpression of pluripotency factors and then induced for differentiation to establish reprogrammed MSC (Re-MSC) lines. We compared the in vitro growth characteristics, chondrogenesis for articular cartilage chondrocytes, and immunomodulatory capacity. We also evaluated the capability of Re-MSCs to repair articular cartilage damage in an animal model with spontaneous OA.

RESULTS

Our results showed that Re-MSCs increased the in vitro proliferative capacity and improved chondrogenic differentiation toward articular cartilage-like chondrocyte phenotypes with increased THBS4 and SIX1 and decreased ALPL and COL10A1, compared to Pa-MSCs. In addition, Re-MSC-derived chondrocytes expressing elevated COL2A and COL2B were more mature than parental cell-derived ones. The enhancement in chondrogenesis of Re-MSC involves the upregulation of sonic hedgehog signaling. Moreover, Re-MSCs improved the repair of articular cartilage in an animal model of spontaneous OA.

CONCLUSIONS

Epigenetic reprogramming promotes MSCs harvested from OA patients to increase phenotypic characteristics and gain robust functions. In addition, Re-MSCs acquire an enhanced potential for articular cartilage repair. Our study here demonstrates that the reprogramming strategy provides a potential solution to the challenge of variation in MSC quality.

Transient anabolic effects of synovium in early post-traumatic osteoarthritis: a novel ex vivo joint tissue co-culture system for investigating synovium-chondrocyte interactions

OBJECTIVE

Osteoarthritis (OA) is a serious joint disease with no disease-modifying medical treatment. To develop treatments targeting synovium, we must improve our understanding of the effects of OA-related changes in synovial physiology on joint tissue outcomes. The aim of this study was to investigate the effects of synovial pathology due to post-traumatic OA (PTOA) on articular chondrocyte physiology.

METHODS

We first developed and validated a novel joint tissue co-culture system to model the biological interactions between synovium and articular chondrocytes. Whole-joint synovial tissue from a surgical rat model of PTOA vs sham and surgical-naïve controls was placed into a co-culture system with adult primary articular chondrocytes (n = 4-5). The effects of PTOA synovium on chondrocyte anabolic, inflammatory, and catabolic gene expression and sulfated glycosaminoglycan (sGAG) secretion and aggrecan synthesis were tested, and results from early and later stages of PTOA development were compared.

RESULTS

Synovial injury by arthrotomy (sham surgery) alone decreased primary chondrocyte expression of genes including Col2a1 (0.36 ± 0.15-fold) and Acan (0.41 ± 0.28-fold). Early PTOA synovium rescued the suppression of Acan, induced increased sGAG secretion (3.94 ± 0.44 μg/mL vs surgery-naïve 2.41 ± 0.55 and sham 2.92 ± 0.73 μg/mL controls), and upregulated Mmp3 (3.73 ± 2.62-fold) and Prg4 (4.93 ± 4.29-fold). These effects were lost with later stage PTOA synovium.

CONCLUSIONS

Early PTOA synovium induces transient anabolic responses in articular chondrocytes rather than pro-inflammatory responses that would require inhibition. These results suggest that PTOA synovium plays at least a partially protective role and that loss of these protective effects may contribute to PTOA progression.

Characterizing correlations among disease severity measures in osteochondral tissues from osteoarthritic knees

Osteoarthritis (OA) is a complex disease with biologic, biomechanical, and clinical heterogeneity among patients. Relationships among OA tissue metabolism, histopathology, and extracellular matrix (ECM) composition have not been well characterized. It was hypothesized that moderate (r = .4-.69) to strong (r > .7) correlations exist among these different measures of disease severity in osteochondral tissues from OA knees. Joint surfaces were obtained from patients (n = 6) undergoing total knee arthroplasty. Osteochondral explants (n = 136) were created and cultured for 3 days. Culture media were collected for biomarker analyses, and tissue was assessed for viability, histological scoring, and ECM composition. Correlations among media biomarker concentrations, histological scoring, ECM composition, and viability were determined using a Spearman correlation. GRO-α, IL-6, IL-8, and MCP-1 showed strong positive correlations to each other, and moderate positive correlations to NO, PGE2, and MMP-2. Total MMP activity, MMP-9, and MMP-13 had strong positive correlations to each other, and moderate positive correlations to MMP-1. MMP-2 had a moderate to strong positive correlations to histological scores (total and cartilage structure) and collagen content. MMP-2, IL-6, IL-8, and MCP-1 had moderate negative correlations, and MMP-9 had a moderate positive correlation, to viability. GRO-α, IL-6, IL-8, and MCP-1 had moderate positive correlations to collagen content. MMP-9, MMP-13, and total MMP activity had moderate negative correlations to tissue GAG. The data suggest links among proinflammatory and degradative pathways are present in OA osteochondral tissues. Further characterization of these links have the potential to delineate mechanisms of disease and diagnostic and therapeutic targets for knee OA.

A Comparative Review of Autologous Conditioned Serum and Autologous Protein Solution for Treatment of Osteoarthritis in Horses

Many alternative treatments aimed at modulating osteoarthritis (OA) progression have been developed in the past decades, including the use of cytokine inhibitors. IL-1β is considered one of the most impactful cytokines in OA disease and therefore, its blockage offers a promising approach for the modulation of OA. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory protein belonging to the IL-1 family that competes with IL-1β for occupancy of its receptors, without triggering the same downstream inflammatory response. Because of its natural anti-inflammatory properties, different methods have been proposed to use IL-1Ra therapeutically in OA. Autologous conditioned serum (ACS) and autologous protein solution (APS) are blood-derived products produced with the use of specialized commercial kits. These processes result in hemoderivatives with high concentrations of IL-1Ra and other cytokines and growth factors with potential modulatory effects on OA progression. Several studies have demonstrated potential anti-inflammatory effect of these therapies with promising clinical results. However, as with any hemoderivatives, clinical outcomes may vary. For optimal therapeutic use, further research is warranted for a more comprehensive understanding of the product's composition and interaction of its components in joint inflammation. Additionally, differences between ACS and APS treatments may not be clear for many clients and clinicians. Thus, the objective of this narrative review is to guide the reader in important aspects of ACS and APS therapies, in vitro and in vivo applications and to compare the use of both treatments in OA.

Complement Expression and Activation in Osteoarthritis Joint Compartments

Objective

To investigate complement(C) factors(F) and their activation fragments expression in OA joint tissues.

Design

Immunohistochemistry and quantitative imaging were performed to analyze C3, C4, and CF (factor) B expression on osteochondral biopsies (43 patients) collected during arthroplasty. Isolated chondrocytes and synoviocytes, cartilage and synovial tissues obtained from surgical specimens of OA patients (15 patients) were cultured with or without IL-1β. Real time PCR for CFB, C3, and C4 was performed. Culture supernatants were analyzed for C3a, C5a, CFBa, and terminal complement complex (TCC) production.

Results

In osteochondral biopsies, C factor expression was located in bone marrow, in a few subchondral bone cells and chondrocytes. C3 was the most expressed while factor C4 was the least expressed factor. Gene expression showed that all C factors analyzed were expressed both in chondrocytes and synoviocytes. In chondrocyte cultures and cartilage explants, CFB expression was significantly higher than C3 and C4. Furthermore, CFB, but not C3 and C4 expression was significantly induced by IL-1β. As to C activation factors, C3a was the most produced and CFBa was induced by IL-1β in synovial tissue. TCC production was undetectable in isolated chondrocytes and synoviocytes cell culture supernatants, whereas it was significantly augmented in cartilage explants.

Conclusion

C factors were locally produced and activated in OA joint with the contribution of all tissues (cartilage, bone, and synovium). Our results support the involvement of innate immunity in OA and suggest an association between some C alternative pathway component and joint inflammation.

Blockade of IL-33 signalling attenuates osteoarthritis

Objectives

Osteoarthritis (OA) is the most common form of arthritis characterised by cartilage degradation, synovitis and pain. Disease modifying treatments for OA are not available. The critical unmet need is to find therapeutic targets to reduce both disease progression and pain. The cytokine IL‐33 and its receptor ST2 have been shown to play a role in immune and inflammatory diseases, but their role in osteoarthritis is unknown.

Methods

Non‐OA and OA human chondrocytes samples were examined for IL‐33 and ST2 expression. Novel inducible cartilage specific knockout mice (IL‐33^{Acan CreERT2}) and inducible fibroblast‐like synoviocyte knockout mice (IL‐33^{Col1a2 CreERT2}) were generated and subjected to an experimental OA model. In addition, wild‐type mice were intra‐articularly administered with either IL‐33‐ or ST2‐neutralising antibodies during experimental OA studies.

Results

IL‐33 and its receptor ST2 have increased expression in OA patients and a murine disease model. Administering recombinant IL‐33 increased OA and pain in vivo. Synovial fibroblast‐specific deletion of IL‐33 decreased synovitis but did not impact disease outcomes, whilst cartilage‐specific deletion of IL‐33 improved disease outcomes in vivo. Blocking IL‐33 signalling also reduced the release of cartilage‐degrading enzymes in human and mouse chondrocytes. Most importantly, we show the use of monoclonal antibodies against IL‐33 and ST2 attenuates both OA and pain in vivo.

Conclusion

Overall, our data reveal blockade of IL‐33 signalling as a viable therapeutic target for OA.

IL-17 and immunologically induced senescence regulate response to injury in osteoarthritis

Senescent cells (SnCs) are implicated in the pathogenesis of age-related diseases including osteoarthritis (OA), in part via expression of a senescence-associated secretory phenotype (SASP) that includes immunologically relevant factors and cytokines. In a model of posttraumatic OA (PTOA), anterior cruciate ligament transection (ACLT) induced a type 17 immune response in the articular compartment and draining inguinal lymph nodes (LNs) that paralleled expression of the senescence marker p16INK4a (Cdkn2a) and p21 (Cdkn1a). Innate lymphoid cells, γδ+ T cells, and CD4+ T cells contributed to IL-17 expression. Intra-articular injection of IL-17-neutralizing antibody reduced joint degeneration and decreased expression of the senescence marker Cdkn1a. Local and systemic senolysis was required to attenuate tissue damage in aged animals and was associated with decreased IL-17 and increased IL-4 expression in the articular joint and draining LNs. In vitro, we found that Th17 cells induced senescence in fibroblasts and that SnCs skewed naive T cells toward Th17 or Th1, depending on the presence of TGF-β. The SASP profile of the inflammation-induced SnCs included altered Wnt signaling, tissue remodeling, and cell-cycle pathways not previously implicated in senescence. These findings provide molecular targets and mechanisms for senescence induction and therapeutic strategies to support tissue healing in an aged environment.

The perspectives of intra-articular therapy in the management of osteoarthritis

Management of Osteoarthritis (OA) still is a challenge for clinicians. Taking into account a multidisciplinary approach including pharmacological and non-pharmacological treatments, intra-articular (IA) injection could be considered as an effective local therapy. Areas covered This review provides a new perspective of IA treatment going beyond current available IA agents. We describe novel biological targets for developing new IA agents and innovative modalities of delivery systems. Additional topics include predictors of response for a better choice of IA agents for each patient, diagnostic and prognostic role of biomarkers, accuracy of IA injection, and cost-effectiveness of IA injection. Expert opinion IA treatments seem to be very promising for the management of OA. Identifying clinical and biochemical predictive factors could drive clinician to the appropriate therapeutic approach. To date, there is a gap regarding the benefit of IA treatments in the 'real practice' once they have been adopted. However, considering these promising effects of IA approach, several open questions remain not clarified.

Spermidine activates RIP1 deubiquitination to inhibit TNF-α-induced NF-κB/p65 signaling pathway in osteoarthritis

Spermidine has been known to inhibit the production of pro-inflammatory cytokines. However, there are no reports about anti-inflammatory effects of spermidine on osteoarthritis (OA). Herein, we examined whether OA progression could be delayed by intraperitoneal injection (i.p.) of spermidine in the anterior cruciate ligament transection (ACLT) and TNF-α induced arthritis (TIA) mouse models. During the process, human FLS cells (H-FLS) were used to investigate the potential ubiquitination mechanism of spermidine-mediated RIP1 in TNF-α-induced NF-κB/p65 signaling. We found that spermidine attenuated synovitis, cartilage degeneration and osteophyte formation, resulting in substantially lower OARSI scores and TNF-α scores in spermidine-treated ACLT and TIA mice. In terms of the mechanism, 9 μM spermidine did not affect the viability, proliferation, cell cycle and apoptosis of H-FLS, and exerted inhibitory effects by activating CYLD-mediated RIP1 deubiquitination on TNF-α-induced NF-κB/p65 signaling in H-FLS. From these data, we can conclude that spermidine attenuates OA progression by the inhibition of TNF-α-induced NF-κB pathway via the deubiquitination of RIP1 in FLS. Therefore, intake of spermidine could be a potential therapy for preventing OA.

Mechanism of aspirin-induced inhibition on the secondary hyperalgesia in osteoarthritis model rats

Aims

The daily activity of osteoarthritis (OA) patients is limited by chronic pain and central sensitization. Although non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen are the first-line drugs for the treatment of OA-related pain, their efficacy on central sensitization remains unclear. In the present study, we evaluated the effect of acetylsalicylic acid (ASA, Aspirin) using an OA model induced by monosodium iodoacetate (MIA), which has a similar disease progression to human OA.

Main methods

Secondary hyperalgesia was assessed at the plantar surface of the hind paw by Von Frey test. We evaluated the expression of acid-sensing ion channel 3 (ASIC3) in dorsal root ganglia and that of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the spinal cord, which may cause secondary hyperalgesia in OA, by immunohistochemical analysis and real-time qPCR.

Key findings

The administration of ASA attenuated secondary hyperalgesia at 1–3 weeks after MIA, while celecoxib, a selective cyclooxygenase (COX)-2 inhibitor, failed to attenuate secondary hyperalgesia at week 2 after MIA injection, suggesting that ASA exerts its analgesic effect through a COX-2-independent pathway. Immunohistochemical analysis of the dorsal root ganglia indicated that ASA reduced the expression of ASIC3 during OA progression. Expression of TNF-α mRNA, but not IL-1β mRNA, in the spinal cord following MIA injection was suppressed by ASA administration.

Significance

These findings suggest that ASA may have the ability to attenuate secondary hyperalgesia through suppression of ASIC3 and/or TNF-α expression. ASA is therefore a clinically useful analgesic drug for treatment of secondary hyperalgesia in OA.

Autologous conditioned serum: clinical and functional results using a novel disease modifying agent for the management of knee osteoarthritis

Objective: The purpose of this study was to investigate the potential ability of autologous conditioned serum (ACS) to decrease pain and improve joint functionality in patients affected by knee osteoarthritis (OA). Methods: Fifteen patients with clinical and radiological signs of OA of the knee were recruited for this study. Each patient received 4 injections of ACS (Orthokine; orthogen, Dusseldorf, Germany) at the site of OA once per week for 4 weeks. Clinical and functional evaluation was performed using the VAS scale for pain, WOMAC scale and KSS functional and clinical scores before the first injection, at one week, at two weeks, at three weeks, at one month and at six months. Statistical analysis was done with the Wilcoxon Signed-Rank Test. Results: Our results show an improvement of all the evaluation scales at 6 months follow-up. Particularly, VAS scales among all patients decreased by 35.8% (p = .00148), KSS functional scores improved by 38.2% (p = .00148), KSS clinical scores improved by 28.9% (p = .00236) and WOMAC scores were reduced by 19.8% (p = .00188). Few adverse effects were observed in our sample. The most common complaint was pain and swelling in the subsequent days after performing the intra-articular injection. Only one patient reported rigidity following the injection of the ACS. Conclusion: Our results, in conjunction with preexisting studies in the medical literature regarding ACS, demonstrate the viability of this therapy for the treatment of knee OA, showing positive influence on pain and joint function without significant adverse effects.

Overexpression of TIMP3 inhibits discogenic pain by suppressing angiogenesis and the expression of substance P in nucleus pulposus

Approximately 50% of the cases of low back pain (LBP) are attributed to discogenic origin. The causes of discogenic pain are complicated and consist of a complex biochemical cascade. Neovascularization of intervertebral discs (IVDs) is believed to be associated with discogenic pain. The anti‑angiogenesis ability of tissue inhibitor of metalloproteinase‑3 (TIMP3) has been reported in many tumors, yet whether TIMP3 is associated with neovascularization of IVDs remains unknown. In the present study, both in vitro and in vivo models were used to investigate the association between discogenic pain and TIMP3 expression in nucleus pulposus (NP). PCR results demonstrated that inflammation induced downregulation of TIMP3 expression in NP cells. By using an adenovirus system to upregulate TIMP3 expression, the effect of TIMP3 on angiogenesis was measured by endothelial cell migration and tube formation assays. The results demonstrated that overexpression of TIMP3 suppressed angiogenesis in NP without the regulation of vascular endothelial growth factor (VEGF) expression. TNF‑α converting enzyme (TACE) expression was downregulated by TIMP3, thus inhibiting the TACE‑induced activation of TNF‑α in NP cells. Immunohistochemical staining of IVDs also confirmed that TIMP3 inhibited the expression of substance P in NP. Taken together, the present results indicated the expression of TIMP3 in NP may have a key role in the development of discogenic pain.

Acid-activatable polymeric curcumin nanoparticles as therapeutic agents for osteoarthritis

Curcumin, a primary active element of turmeric, has potent antioxidant and anti-inflammatory activity, but its low bioavailability is a major hurdle in its pharmaceutical applications. To enhance the therapeutic efficacy of curcumin, we exploited polymeric prodrug strategy. Here, we report rationally designed acid-activatable curcumin polymer (ACP), as a therapeutic prodrug of curcumin, in which curcumin was covalently incorporated in the backbone of amphiphilic polymer. ACP could self-assemble to form micelles that rapidly release curcumin under the acidic condition. The potential of ACP micelles as therapeutics for osteoarthritis was evaluated using a mouse model of monoidoacetic acid (MIA)-induced knee osteoarthritis. ACP micelles drastically protected the articular structures from arthritis through the suppression of tumor necrosis factor-alpha (TNF-α) and interleukin 1β (IL-1β). Given their pathological stimulus-responsiveness and potent antioxidant and anti-inflammatory activities, ACP micelles hold remarkable potential as a therapeutic agent for not only osteoarthritis but also various inflammatory diseases.

A placebo-controlled study comparing the efficacy of intra-articular injections of hyaluronic acid and a novel hyaluronic acid-platelet-rich plasma conjugate in a canine model of osteoarthritis

Background

The objective of this study was to assess the efficacy of intra-articular injections of hyaluronic acid (HA) and a novel, on-site conjugate of HA with autologous fibrinogen in platelet-rich plasma (HA-PRP) in a canine model of osteoarthritis (OA)

Methods

Twelve beagle dogs underwent a unilateral resection of the cranial cruciate ligament (CrCL) of the stifle joint. Clinical and radiographic signs of OA were confirmed in all dogs 8 weeks following CrCL resection and prior to treatment. The dogs were randomized into three groups: saline (n = 4), HA (n = 4), and HA-PRP (n = 4). Each dog received intra-articular injections of the respective substance into the affected joint at pre-determined time points. The dogs were assessed for adverse effects for 3 days after each injection and for lameness, pain, range of motion, kinetics, and radiographic OA severity prior to treatment and 3 months after injection. OA severity as determined by radiographic examination was not significantly different among the groups at any time point. The dogs were then humanely euthanatized and the stifle joint assessed by gross and histological examinations.

Results

Dogs treated with four weekly injections of HA or two biweekly injections of HA-PRP were significantly (p < 0.05) better than dogs treated with four weekly injections of saline at 2-, 4-, and 12-week time points based on a comfortable range of motion (CROM) and clinical lameness score. Gait analysis measuring symmetry and weight distribution on pressure sensor walkway showed significantly (p < 0.05) improved limb function for dogs treated with HA and HA-PRP compared with dogs treated with saline yet with better clinical outcome for the HA-PRP-treated group at 12 and 20 weeks follow-up. Gross and histological analysis of synovium and articular cartilage demonstrated significant (p < 0.05) improvement by both treatments groups compared to controls. There was however significantly (p < 0.05) less damage to the cartilage in the HA-PRP group compared to the HA-treated group.

Conclusions

These data suggest that while injection of HA and HA-PRP may be sufficient for short-term amelioration of the symptoms associated with OA, treatment with HA-PRP conjugates may be superior, providing significantly better long-term cartilage preservation.

Long Non-coding RNA HOTTIP Promotes CCL3 Expression and Induces Cartilage Degradation by Sponging miR-455-3p

Long non-coding RNAs (lncRNAs) play pivotal roles in diseases such as osteoarthritis (OA). However, knowledge of the biological roles of lncRNAs is limited in OA. We aimed to explore the biological function and molecular mechanism of HOTTIP in chondrogenesis and cartilage degradation. We used the human mesenchymal stem cell (hMSC) model of chondrogenesis, in parallel with, tissue biopsies from normal and OA cartilage to detect HOTTIP, CCL3, and miR-455-3p expression in vitro. Biological interactions between HOTTIP and miR-455-3p were determined by RNA silencing and overexpression in vitro. We evaluated the effect of HOTTIP on chondrogenesis and degeneration, and its regulation of miR-455-3p via competing endogenous RNA (ceRNA). Our in vitro ceRNA findings were further confirmed within animal models in vivo. Mechanisms of ceRNAs were determined by bioinformatic analysis, a luciferase reporter system, RNA pull-down, and RNA immunoprecipitation (RIP) assays. We found reduced miR-455-3p expression and significantly upregulated lncRNA HOTTIP and CCL3 expression in OA cartilage tissues and chondrocytes. The expression of HOTTIP and CCL3 was increased in chondrocytes treated with interleukin-1β (IL-1β) in vitro. Knockdown of HOTTIP promoted cartilage-specific gene expression and suppressed CCL3. Conversely, HOTTIP overexpression reduced cartilage-specific genes and increased CCL3. Notably, HOTTIP negatively regulated miR-455-3p and increased CCL3 levels in human primary chondrocytes. Mechanistic investigations indicated that HOTTIP functioned as ceRNA for miR-455-3p enhanced CCL3 expression. Taken together, the ceRNA regulatory network of HOTTIP/miR-455-3p/CCL3 plays a critical role in OA pathogenesis and suggests HOTTIP is a potential target in OA therapy.

Injectable biomaterials for delivery of interleukin-1 receptor antagonist: Toward improving its therapeutic effect

Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory cytokine that inhibits IL-1 activity and has been proposed to treat a wide variety of systemic and local inflammatory pathologies for multiple decades. However, the short half-life and high concentration required to inhibit IL-1 activity has limited its use in clinical applications. Many strategies have been developed with the goal of improving the therapeutic efficacy of IL-1Ra for a variety of pathologies, including fusing IL-1Ra to protein/peptide/polymer partners, releasing IL-1Ra from injectable polymer or mineral particles, and release of IL-1Ra from injectable coacervates and gels. This literature review examines injectable biomaterials engineered to improve IL-1Ra delivery, both locally and systemically, to increase its efficacy and ease of use in clinic. STATEMENT OF SIGNIFICANCE: Interleukin-1 receptor antagonist (IL-1Ra) is a therapeutic protein with the potential to treat numerous inflammatory conditions and diseases. However, its short biological half-life and high therapeutic concentration may limit its utility in all but a few clinical scenarios. In this review, we present the biomaterial based delivery strategies which have been explored to deliver IL-1Ra to improve its efficacy and applicability to treat inflammation.

Interleukin-1 receptor antagonist protein (IL-1Ra) and miR-140 overexpression via pNNS-conjugated chitosan-mediated gene transfer enhances the repair of full-thickness cartilage defects in a rabbit model

Objectives

Previously, we reported the improved transfection efficiency of a plasmid DNA-chitosan (pDNA-CS) complex using a phosphorylatable nuclear localization signal-linked nucleic kinase substrate short peptide (pNNS) conjugated to chitosan (pNNS-CS). This study investigated the effects of pNNS-CS-mediated miR-140 and interleukin-1 receptor antagonist protein (IL-1Ra) gene transfection both in rabbit chondrocytes and a cartilage defect model.

Methods

The pBudCE4.1-miR-140, pBudCE4.1-IL-1Ra, and negative control pBudCE4.1 plasmids were constructed and combined with pNNS-CS to form pDNA/pNNS-CS complexes. These complexes were transfected into chondrocytes or injected into the knee joint cavity.

Results

High IL-1Ra and miR-140 expression levels were detected both in vitro and in vivo. In vitro, compared with the pBudCE4.1 group, the transgenic group presented with significantly increased chondrocyte proliferation and glycosaminoglycan (GAG) synthesis, as well as increased collagen type II alpha 1 chain (COL2A1), aggrecan (ACAN), and TIMP metallopeptidase inhibitor 1 (TIMP-1) levels. Nitric oxide (NO) synthesis was reduced, as were a disintegrin and metalloproteinase with thrombospondin type 1 motif 5 (ADAMTS-5) and matrix metalloproteinase (MMP)-13 levels. In vivo, the exogenous genes reduced the synovial fluid GAG and NO concentrations and the ADAMTS-5 and MMP-13 levels in cartilage. In contrast, COL2A1, ACAN, and TIMP-1 levels were increased, and the cartilage Mankin score was decreased in the transgenic group compared with the pBudCE4.1 group. Double gene combination produced greater efficacies than each single gene, both in vitro and in vivo.

Conclusion

This study suggests that pNNS-CS is a good candidate for treating cartilage defects via gene therapy, and that IL-1Ra in combination with miR-140 produces promising biological effects on cartilage defects.

Cite this article: R. Zhao, S. Wang, L. Jia, Q. Li, J. Qiao, X. Peng. Interleukin-1 receptor antagonist protein (IL-1Ra) and miR-140 overexpression via pNNS-conjugated chitosan-mediated gene transfer enhances the repair of full-thickness cartilage defects in a rabbit model. Bone Joint Res 2019;8:165–178. DOI: 10.1302/2046-3758.83.BJR-2018-0222.R1.

Ageing and Osteoarthritis

The increase in global lifespan has in turn increased the prevalence of osteoarthritis which is now the most common type of arthritis. Cartilage tissue located on articular joints erodes during osteoarthritis which causes pain and may lead to a crippling loss of function in patients. The pathophysiology of osteoarthritis has been understudied and currently no disease modifying treatments exist. The only current end-point treatment remains joint replacement surgery. The primary risk factor for osteoarthritis is age. Clinical and basic research is now focused on understanding the ageing process of cartilage and its role in osteoarthritis. This chapter will outline the physiology of cartilage tissue, the clinical presentation and treatment options for the disease and the cellular ageing processes which are involved in the pathophysiology of the disease.

Effects of Anti-Inflammatory Agents on Expression of Early Responsive Inflammatory and Catabolic Genes in Ex Vivo Porcine Model of Acute Knee Cartilage Injury

Objective Early intervention therapies targeting inflammation and cell death during the acute phase of cartilage injury have the potential to prevent posttraumatic osteoarthritis. The objective of this study was to investigate the effects of interleukin receptor antagonist protein (IRAP), hyaluronan (HA), dexamethasone (DEX), and mesenchymal stem cell (MSC) treatment on the expression of established genetic markers for matrix degradation, apoptosis, and inflammation in articular cartilage during the acute phase of injury. Design A custom impact device was used to create replicable injury ex vivo to intact porcine knee joint. One hour after impact, IRAP, HA, DEX, or MSCs was intra-articularly injected. At 8 hours postinjury, cartilage and meniscus samples were harvested for genetic expression analysis. Expression of miR-27b, miR-140, miR-125b, miR-16, miR-34a, miR-146a, miR-22, ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α was analyzed by real-time polymerase chain reaction. Results At 8 hours postinjury, expression of ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α in cartilage was significantly decreased in IRAP- and DEX-treated joints as compared to nontreated injured joints, whereas only IRAP upregulated expression of miR-140, miR-125b, miR-27b, miR-146a, and miR-22 in cartilage. HA and MSC treatments had no significant effects on catabolic and inflammatory gene expression in cartilage. However, HA treatment significantly upregulated expression of all miRNAs except miR-16. In addition, the treatments tested also exhibited significant influences on meniscus. Conclusions This study provides a valuable starting point for further research into potential targets for and efficacy of various early intervention strategies that may delay or prevent the progression of posttraumatic osteoarthritis after acute cartilage injury.

Cytokine-induced interleukin-1 receptor antagonist protein expression in genetically engineered equine mesenchymal stem cells for osteoarthritis treatment

BACKGROUND

A combination of tissue engineering methods employing mesenchymal stem cells (MSCs) together with gene transfer takes advantage of innovative strategies and highlights a new approach for targeting osteoarthritis (OA) and other cartilage defects. Furthermore, the development of systems allowing tunable transgene expression as regulated by natural disease-induced substances is highly desirable.

METHODS

Bone marrow-derived equine MSCs were transduced with a lentiviral vector expressing interleukin-1 receptor antagonist (IL-1Ra) gene under the control of an inducible nuclear factor-kappa B-responsive promoter and IL-1Ra production upon pro-inflammatory cytokine stimulation [tumor necrosis factor (TNF)α, interleukin (IL)-1β] was analysed. To assess the biological activity of the IL-1Ra protein that was produced and the therapeutic effect of IL-1Ra-expressing MSCs (MSC/IL-1Ra), cytokine-based two- and three-dimensional in vitro models of osteoarthritis using equine chondrocytes were established and quantitative real-time polymerase chain reaction (PCR) analysis was used to measure the gene expression of aggrecan, collagen IIA1, interleukin-1β, interleukin-6, interleukin-8, matrix metalloproteinase-1 and matrix metalloproteinase-13.

RESULTS

A dose-dependent increase in IL-1Ra expression was found in MSC/IL-1Ra cells upon TNFα administration, whereas stimulation using IL-1β did not lead to IL-1Ra production above the basal level observed in nonstimulated cells as a result of the existing feedback loop. Repeated cycles of induction allowed on/off modulation of transgene expression. In vitro analyses revealed that IL-1Ra protein present in the conditioned medium from MSC/IL-1Ra cells blocks OA onset in cytokine-treated equine chondrocytes and co-cultivation of MSC/IL-1Ra cells with osteoarthritic spheroids alleviates the severity of the osteoarthritic changes.

CONCLUSIONS

Thus, pro-inflammatory cytokine induced IL-1Ra protein expression from genetically modified MSCs might represent a promising strategy for osteoarthritis treatment.

Cdc42 Is Essential for Both Articular Cartilage Degeneration and Subchondral Bone Deterioration in Experimental Osteoarthritis

Cdc42, a member of Rho family small guanosine triphosphatases (GTPases), is critical for cartilage development. We investigated the roles of Cdc42 in osteoarthritis and explored the potential mechanism underlying Cdc42-mediated articular cartilage degeneration and subchondral bone deterioration. Cdc42 is highly expressed in both articular cartilage and subchondral bone in a mouse osteoarthritis model with surgical destabilization of the medial meniscus (DMM) in the knee joints. Specifically, genetic disruption of Cdc42, knockdown of Cdc42 expression, or inhibition of Cdc42 activity robustly attenuates the DMM-induced destruction, hypertrophy, high expression of matrix metallopeptidase-13 and collagen X, and activation of Stat3 in articular cartilages. Notably, genetic disruption of Cdc42, knockdown of Cdc42 expression or inhibition of Cdc42 activity significantly restored the increased numbers of mesenchymal stem cells, osteoprogenitors, osteoblasts, osteoclasts, and neovascularized vessels, the increased bone mass, and the activated Erk1/2, Smad1/5 and Smad2 in subchondral bone of DMM-operated mice. Mechanistically, Cdc42 mediates interleukin-1β-induced interleukin-6 production and subsequent Jak/Stat3 activation to regulate chondrocytic inflammation, and also lies upstream of Erk/Smads to regulate subchondral bone remodeling during transform growth factor-β1 signaling. Cdc42 is apparently required for both articular cartilage degeneration and subchondral bone deterioration of osteoarthritis, thus, interventions targeting Cdc42 have potential in osteoarthritic therapy. © 2018 American Society for Bone and Mineral Research.

MicroRNA-193b-3p regulates chondrogenesis and chondrocyte metabolism by targeting HDAC3

Histone deacetylase 3 (HDAC3) plays a pivotal role in the repression of cartilage-specific gene expression in human chondrocytes. The aim of this study was to determine whether microRNA-193b-3p (miR-193b-3p) regulates the expression of HDAC3 during chondrogenesis and chondrocyte metabolism. Methods: miR-193b-3p expression was assessed in a human mesenchymal stem cell (hMSC) model of chondrogenesis, in interleukin-1β (IL-1β)-treated primary human chondrocytes (PHCs), and in non-degraded and degraded cartilage. hMSCs and PHCs were transfected with miR-193b-3p or its antisense inhibitor. A direct interaction between miR-193b-3p and its putative binding site in the 3'-untranslated region (3'-UTR) of HDAC3 mRNA was confirmed by performing luciferase reporter assays. Chondrocytes were transfected with miR-193b-3p before performing a chromatin immunoprecipitation assay with an anti-acetylated histone H3 antibody. To investigate miR-193b-3p-transfected PHCs in vivo, they were seeded in tricalcium phosphate-collagen-hyaluronate (TCP-COL-HA) scaffolds, which were then implanted in nude mice. In addition, plasma exosomal miR-193b-3p in samples from normal controls and patients with osteoarthritis (OA) were measured. Results: miR-193b-3p expression was elevated in chondrogenic and hypertrophic hMSCs, while expression was significantly reduced in degraded cartilage compared to non-degraded cartilage. In addition, miR-193b-3p suppressed the activity of reporter constructs containing the 3'-UTR of HDAC3, inhibited HDAC3 expression, and promoted histone H3 acetylation in the COL2A1, AGGRECAN, COMP, and SOX9 promoters. Treatment with the HDAC inhibitor trichostatin A (TSA) increased cartilage-specific gene expression and enhanced hMSCs chondrogenesis. TSA also increased AGGRECAN expression and decreased MMP13 expression in IL-1β-treated PHCs. Further, 8 weeks after implanting PHC-seeded TCP-COL-HA scaffolds subcutaneously in nude mice, we found that miR-193b overexpression strongly enhanced in vivo cartilage formation compared to that found under control conditions. We also found that patients with OA had lower plasma exosomal miR-193b levels than control subjects. Conclusions: These findings indicate that miR-193b-3p directly targets HDAC3, promotes H3 acetylation, and regulates hMSC chondrogenesis and metabolism in PHCs.

Effects of a phosphocitrate analogue on osteophyte, subchondral bone advance, and bone marrow lesions in Hartley guinea pigs

Objectives

The objectives of this study were: 1) to examine osteophyte formation, subchondral bone advance, and bone marrow lesions (BMLs) in osteoarthritis (OA)-prone Hartley guinea pigs; and 2) to assess the disease-modifying activity of an orally administered phosphocitrate ‘analogue’, Carolinas Molecule-01 (CM-01).

Methods

Young Hartley guinea pigs were divided into two groups. The first group (n = 12) had drinking water and the second group (n = 9) had drinking water containing CM-01. Three guinea pigs in each group were euthanized at age six, 12, and 18 months, respectively. Three guinea pigs in the first group were euthanized aged three months as baseline control. Radiological, histological, and immunochemical examinations were performed to assess cartilage degeneration, osteophyte formation, subchondral bone advance, BMLs, and the levels of matrix metalloproteinse-13 (MMP13) protein expression in the knee joints of hind limbs.

Results

In addition to cartilage degeneration, osteophytes, subchondral bone advance, and BMLs increased with age. Subchondral bone advance was observed as early as six months, whereas BMLs and osteophytes were both observed mainly at 12 and 18 months. Fibrotic BMLs were found mostly underneath the degenerated cartilage on the medial side. In contrast, necrotic BMLs were found almost exclusively in the interspinous region. Orally administered CM-01 decreased all of these pathological changes and reduced the levels of MMP13 expression.

Conclusion

Subchondral bone may play a role in cartilage degeneration. Subchondral bone changes are early events; formation of osteophytes and BMLs are later events in the OA disease process. Carolinas Molecule-01 is a promising small molecule candidate to be tested as an oral disease-modifying drug for human OA therapy.

Cite this article: Y. Sun, A. J. Kiraly, A. R. Sun, M. Cox, D. R. Mauerhan, E. N. Hanley Jr. Effects of a phosphocitrate analogue on osteophyte, subchondral bone advance, and bone marrow lesions in Hartley guinea pigs. Bone Joint Res 2018;7:157–165. DOI:10.1302/2046-3758.72.BJR-2017-0253.

Therapeutics in Osteoarthritis Based on an Understanding of Its Molecular Pathogenesis

Osteoarthritis (OA) is the most prevalent joint disease in older people and is characterized by the progressive destruction of articular cartilage, synovial inflammation, changes in subchondral bone and peri-articular muscle, and pain. Because our understanding of the aetiopathogenesis of OA remains incomplete, we haven’t discovered a cure for OA yet. This review appraises novel therapeutics based on recent progress in our understanding of the molecular pathogenesis of OA, including pro-inflammatory and pro-catabolic mediators and the relevant signalling mechanisms. The changes in subchondral bone and peri-articular muscle accompanying cartilage damage are also reviewed.

A small-molecule inhibitor of the Wnt pathway (SM04690) as a potential disease modifying agent for the treatment of osteoarthritis of the knee

OBJECTIVES

Osteoarthritis (OA) is a degenerative disease characterized by loss of cartilage and increased subchondral bone within synovial joints. Wnt signaling affects the pathogenesis of OA as this pathway modulates both the differentiation of osteoblasts and chondrocytes, and production of catabolic proteases. A novel small-molecule Wnt pathway inhibitor, SM04690, was evaluated in a series of in vitro and in vivo animal studies to determine its effects on chondrogenesis, cartilage protection and synovial-lined joint pathology.

DESIGN

A high-throughput screen was performed using a cell-based reporter assay for Wnt pathway activity to develop a small molecule designated SM04690. Its properties were evaluated in bone-marrow-derived human mesenchymal stem cells (hMSCs) to assess chondrocyte differentiation and effects on cartilage catabolism by immunocytochemistry and gene expression, and glycosaminoglycan breakdown. In vivo effects of SM04690 on Wnt signaling, cartilage regeneration and protection were measured using biochemical and histopathological techniques in a rodent acute cruciate ligament tear and partial medial meniscectomy (ACLT + pMMx) OA model.

RESULTS

SM04690 induced hMSC differentiation into mature, functional chondrocytes and decreased cartilage catabolic marker levels compared to vehicle. A single SM04690 intra-articular (IA) injection was efficacious in a rodent OA model, with increased cartilage thickness, evidence for cartilage regeneration, and protection from cartilage catabolism observed, resulting in significantly improved Osteoarthritis Research Society International (OARSI) histology scores and biomarkers, compared to vehicle.

CONCLUSIONS

SM04690 induced chondrogenesis and appeared to inhibit joint destruction in a rat OA model, and is a candidate for a potential disease modifying therapy for OA.

Topical Effects of Artemisia Absinthium Ointment and Liniment in Comparison with Piroxicam Gel in Patients with Knee Joint Osteoarthritis: A Randomized Double-Blind Controlled Trial

BACKGROUND

Pain alleviation and improvement of functional status are the main objectives in the treatment of osteoarthritis. Artemisia absinthium (AA) was used traditionally in reducing pain and inflammation. The aim of the present study was to compare the effects of topical formulations of AA and piroxicam gel (PG) among patients with knee osteoarthritis.

METHODS

In total, 90 outpatients aged 30-70 years with the diagnosis of primary osteoarthritis in at least one knee were enrolled in a randomized double-blind clinical trial. The patients referred to the Rheumatology Clinic at Shahid Beheshti Hospital in Hamadan province during 2012-2013. The patients were randomly assigned into three groups, 30 patients per group, and respectively received AA ointment (AAO) 3%, AA liniment (AAL) 3%, and PG; three times daily (TID) for 4 weeks. The patients were visited at baseline, week 4, and week 6. The effectiveness criteria were pain severity which was assessed with a 10-point visual analog scale (VAS), the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) for total pain score (WTPS), total physical function score (WTPFS), and total stiffness score (WTSS). Repeated measure ANOVA, paired t test and post hoc were used to compare variables. Statistical analysis was performed using the SPSS software, version 13.0 (SPSS Inc., Chicago, Illinois).

RESULTS

All groups had similar patient demographics. The administration of PG significantly improved all tested criteria with no recurrence after discontinuing the treatment protocol. AAO alleviated all tested factors except for WTSS. Alleviation was comparable to PG. AAL only reduced pain factors (VAS, WTPS) in week 4 with recurrence in week 6.

CONCLUSION

Administration of Artemisia ointment may have beneficial effects in the treatment of osteoarthritis. Trial Registration Number: IRCT201202123109N3.

Identification of key mRNAs and microRNAs in the pathogenesis and progression of osteoarthritis using microarray analysis

Osteoarthritis (OA) is a common type of disease affecting the joints that results from the breakdown of joint cartilage and the underlying bone; currently, its pathogenesis is still unclear. The aim of the present study was to identify key mRNAs and miRNAs involved in the pathogenesis and progression of OA using microarray analysis. The gene expression profile of GSE27492 was downloaded from the Gene Expressed Omnibus database, and included 49 arthritic mouse ankle samples collected at 6 time points (0, 1, 3, 7, 12 and 18 days) following the induction of arthritis via serum transfer. Differentially expressed genes (DEGs) were identified in ankle samples taken on days 1, 3, 7, 12 and 18 following serum transfer compared with day 0 samples, and overlapping DEGs in day 3, 7, 12 and 18 samples were identified. The Database for Annotation, Visualization and Integrated Discovery online tool was used to perform functional and pathway enrichment analyses of the overlapping DEGs. The miRWalk database was used to identify potential micro (mi) RNAs regulating the selected overlapping DEGs, and regulatory miRNA‑target mRNA pairs were obtained. The Cytoscape platform was used to establish and visualize the miRNA‑mRNA regulatory network. The present results revealed that 35, 103, 62 and 75 DEGs were identified in day 3, 7, 12 and 18 samples, respectively. A total of 17 overlapping DEGs were identified among the 4 sample sets, and revealed to be enriched in 14 gene ontology terms and 3 Kyoto Encyclopedia of Genes and Genomes pathways. miRWalk analysis identified 242 potential miRNA‑mRNA regulatory pairs and 211 nodes were revealed to be involved in the miRNA‑mRNA regulatory network. The present study identified potential genes, including C‑type lectin domain family 4 member D, chemokine (C‑X‑C motif) ligand 1 and C‑C motif chemokine ligand, and pathways, including chemokine signaling pathways, cytokine‑cytokine receptor interactions and nucleotide‑binding oligomerization domain‑like receptor signaling pathways, which may be involved in the pathogenesis and progression of OA. These findings may help elucidate the molecular mechanisms underlying OA pathophysiology, and may be useful for the development of novel therapeutic targets for the treatment of patients with OA.

Anabolic role of lysyl oxidase like-2 in cartilage of knee and temporomandibular joints with osteoarthritis

Background

Lysyl oxidase like-2 (LOXL2) is a copper-dependent amine oxidase. Our previous studies showed that LOXL2 is elevated during mouse fracture healing. The goal of this study was to evaluate the potential of LOXL2 to act as an anabolic agent in cartilage affected by osteoarthritis (OA).

Methods

LOXL2 was visualized in tissues from human knee and hip joints and temporomandibular joints (TMJ) by immunofluorescence. The activity of LOXL2 in human articular and TMJ chondrocytes was assessed by cell-based assays, microarray analysis, and RT-qPCR, and LOXL2-mediated activation of NF-κB and extracellular signal-related kinase (ERK) signaling pathways was measured by western blotting. To examine LOXL2-induced effect in vivo, we implanted Matrigel-imbedded human chondrocytes into nude mice and exposed them to exogenous LOXL2 for 6 weeks. Finally, LOXL2-induced effects on collagen type 2 α1 (COL2A1) and phospho-SMAD2/3 were evaluated by immunofluorescence analysis.

Results

LOXL2 staining was detected in damaged regions of human TMJ, hip and knee joints affected by OA. Stimulation with transforming growth factor (TGF)-β1 upregulated LOXL2 expression, while pro-inflammatory cytokines IL-1β and TNF-α downregulated LOXL2, in human chondrocytes. Viral transduction of LOXL2 in OA chondrocytes increased the mRNA levels of chondroitin sulfate proteoglycan (CSPG4), aggrecan (ACAN), sex determining region Y-box containing gene 9 (SOX9), and COL2A1 but reduced the levels of extracellular matrix (ECM)-degrading enzymes matrix metalloproteinase (MMP)1, MMP3, and MMP13. Further, forced expression of LOXL2 promoted chondrogenic lineage-specific gene expression, increased the expression of COL2A1 in the presence of TNF-α, and inhibited chondrocyte apoptosis. LOXL2 expression also inhibited IL-1β-induced phospho-NF-κB/p65 and TGF-β1-induced ERK1/2 phosphorylation. Matrigel constructs of human chondrocytes from the knee joint and TMJ implanted in nude mice showed anabolic responses after LOXL2 transduction, including increased expression of SOX9, ACAN, and COL2A1. Finally, immunofluorescence staining revealed co-localization of LOXL2 with SOX9 in the nuclei of cells in the implants, decreased phospho-SMAD2/3, and increased COL2A1 staining.

Conclusion

Our results suggest that although LOXL2 is upregulated in cartilage affected by OA, this may be a protective response that promotes anabolism while inhibiting specific catabolic responses in the pathophysiology of OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1388-8) contains supplementary material, which is available to authorized users.

Rapamycin Maintains the Chondrocytic Phenotype and Interferes with Inflammatory Cytokine Induced Processes

Osteoarthritis (OA) is hallmarked by a progressive degradation of articular cartilage. Besides risk factors including trauma, obesity or genetic predisposition, inflammation has a major impact on the development of this chronic disease. During the course of inflammation, cytokines such as tumor necrosis factor-alpha(TNF-α) and interleukin (IL)-1β are secreted by activated chondrocytes as well as synovial cells and stimulate the production of other inflammatory cytokines and matrix degrading enzymes. The mTORC1 inhibitor rapamycin is a clinical approved immunosuppressant and several studies also verified its chondroprotective effects in OA. However, the effect of blocking the mechanistic target of rapamycin complex (mTORC)1 on the inflammatory status within OA is not well studied. Therefore, we aimed to investigate if inhibition of mTORC1 by rapamycin can preserve and sustain chondrocytes in an inflammatory environment. Patient-derived chondrocytes were cultured in media supplemented with or without the mTORC1 inhibitor rapamycin. To establish an inflammatory environment, either TNF-α or IL-1β was added to the media (=OA-model). The chondroprotective and anti-inflammatory effects of rapamycin were evaluated using sulfated glycosaminoglycan (sGAG) release assay, Caspase 3/7 activity assay, lactate dehydrogenase (LDH) assay and quantitative real time polymerase chain reaction (PCR). Blocking mTORC1 by rapamycin reduced the release and therefore degradation of sGAGs, which are components of the extracellular matrix secreted by chondrocytes. Furthermore, blocking mTORC1 in OA chondrocytes resulted in an enhanced expression of the main chondrogenic markers. Rapamycin was able to protect chondrocytes from cell death in an OA-model shown by reduced Caspase 3/7 activity and diminished LDH release. Furthermore, inhibition of mTORC1 preserved the chondrogenic phenotype of OA chondrocytes, but also reduced inflammatory processes within the OA-model. This study highlights that blocking mTORC1 is a new and promising approach for treating OA. Low side effects make rapamycin an attractive implementation to existing therapeutic strategies. We showed that rapamycin's chondroprotective property might be due to an interference with IL-1β triggered inflammatory processes.

Biological Effects of Phosphocitrate on Osteoarthritic Articular Chondrocytes

BACKGROUND

Phosphocitrate (PC) inhibits osteoarthritis (OA) in Hartley guinea pigs. However, the underlying molecular mechanisms remain poorly understood.

OBJECTIVE

This study sought to examine the biological effect of PC on OA chondrocytes and test the hypothesis that PC may exert its OA disease modifying effect, in part, by inhibiting the expression of genes implicated in OA disease process and stimulating the production of extracellular matrices.

METHOD

OA chondrocytes were cultured in the absence or presence of PC. Total RNA was extracted and subjected to microarray analyses. The effect of PC on proliferation and chondrocyte-mediated calcification were examined in monolayer culture. The effect of PC on the production of extracellular matrices was examined in micromass culture.

RESULTS

PC downregulated the expression of numerous genes classified in proliferation and apoptosis while upregulating the expression of many genes classified in transforming growth factor-β (TGF-β) receptor signaling pathway and ossification. PC also downregulated the expressions of many genes classified in inflammatory response and Wnt receptor signaling pathways. Consistent with its effect on the expression of genes classified in proliferation, ossification, and skeletal development, PC inhibited the proliferation of OA chondrocytes and chondrocyte-mediated calcification while stimulating the production of extracellular matrices.

CONCLUSION

PC may exert its OA disease modifying effect, in part, through a crystal-independent mechanism or by inhibiting the expressions of many genes implicated in OA disease process, and at the same time, stimulating the expression of genes implicated in chondroprotection and production of extracellular matrices.

Interleukin-1 is not involved in synovial inflammation and cartilage destruction in collagenase-induced osteoarthritis

OBJECTIVE

Interleukin-1 (IL-1) is an alleged important cytokine in osteoarthritis (OA), although the exact contribution of IL-1 to joint destruction remains unclear. Here we investigated the involvement of IL-1α and IL-1β in joint pathology during collagenase-induced OA (CiOA).

METHODS

CiOA was induced in wild type (WT) and IL-1αβ^-/- mice. Additionally, IL-1 signaling was inhibited in WT mice with CiOA using osmotic pumps containing IL-1RA. Joint pathology was assessed using histology. Activity of cartilage-degrading enzymes was determined using antibodies against aggrecan neo-epitopes VDIPEN and NITEGE. Synovial gene expression was analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). Serum protein levels were measured with Luminex or enzyme-linked immunosorbent assay (ELISA).

RESULTS

Synovial IL-1β expression was strongly elevated 7 days after induction of CiOA in WT mice but decreased afterwards, whereas S100A8/A9, previously described to aggravate OA, remained elevated for 21 days. Remarkably, synovial inflammation was comparable between WT and IL-1αβ^-/- mice on day 7 of CiOA. In line, synovial mRNA expression of genes involved in IL-1 signaling and inflammatory mediators was comparable between WT and IL-1αβ^-/- mice, and serum levels for Keratinocyte Chemoattractant (KC)/IL-6/S100A8/S100A9/IL-10 were equal. Synovial matrix metalloproteinase (MMP)/aggrecanase expression and activity in cartilage was not different in WT and IL-1αβ^-/- mice on day 7 of CiOA. Cartilage destruction on day 42 was not different between WT and IL-1αβ^-/- mice, which was supported by our finding that IL-1RA treatment in WT mice with CiOA did not alter joint destruction.

CONCLUSIONS

IL-1α and IL-1β are not involved in synovial inflammation and cartilage destruction during CiOA, implicating that other mediators are responsible for the joint damage.

Negative Regulators of JAK/STAT Signaling in Rheumatoid Arthritis and Osteoarthritis

Elevated levels of pro-inflammatory cytokines are generally thought to be responsible for driving the progression of synovial joint inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA). These cytokines activate several signal transduction pathways, including the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Stress-Activated/Mitogen-Activated Protein Kinase (SAPK/MAPK) and phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin (PI3K/Akt/mTOR) pathways which regulate numerous cellular responses. However, cytokine gene expression, matrix metalloproteinase gene expression and aberrant immune cell and synoviocyte survival via reduced apoptosis are most critical in the context of inflammation characteristic of RA and OA. Negative regulation of JAK/STAT signaling is controlled by Suppressor of Cytokine Signaling (SOCS) proteins. SOCS is produced at lower levels in RA and OA. In addition, gaining further insight into the role played in RA and OA pathology by the inhibitors of the apoptosis protein family, cellular inhibitor of apoptosis protein-1, -2 (c-IAP1, c-IAP2), X (cross)-linked inhibitor of apoptosis protein (XIAP), protein inhibitor of activated STAT (PIAS), and survivin (human) as well as SOCS appears to be a worthy endeavor going forward.

Anti-Inflammatory Activity in the Low Molecular Weight Fraction of Commercial Human Serum Albumin (LMWF5A)

The innate immune system is increasingly being recognized as a critical component in osteoarthritis (OA) pathophysiology. An ex vivo immunoassay utilizing human peripheral blood mononuclear cells (PBMC) was developed in order to assess the OA anti-inflammatory properties of the low molecular weight fraction (<5 kDa) of commercial human serum albumin (LMWF5A). PBMC from various donors were pre-incubated with LMWF5A before LPS stimulation. TNFα release was measured by ELISA in supernatants after an overnight incubation. A ≥ 30% decrease in TNFα release was observed. This anti-inflammatory effect is potentially useful in assessing potency of LMWF5A for the treatment of OA.