Human osteoarthritis synovial fluid and joint cartilage contain both aggrecanase- and matrix metalloproteinase-generated aggrecan fragments

Comparative study of 1H-NMR metabolomic profile of canine synovial fluid in patients affected by four progressive stages of spontaneous osteoarthritis

The study aimed to assess the metabolomic profile of the synovial fluid (SF) of dogs affected by spontaneous osteoarthritis (OA) and compare any differences based on disease progression. Sixty client-owned dogs affected by spontaneous OA underwent clinical, radiographic, and cytologic evaluations to confirm the diagnosis. The affected joints were divided into four study groups based on the Kallgreen-Lawrence classification: OA1 (mild), OA2 (moderate), OA3 (severe), and OA4 (extremely severe/deforming). The osteoarthritic joint's SF was subjected to cytologic examination and 1H-NMR analysis. The metabolomic profiles of the study groups' SF samples were statistically compared using one-way ANOVA. Sixty osteoarthritic joints (45 stifles, 10 shoulders and 5 elbows) were included in the study. Fourteen, 28, and 18 joints were included in the OA1, OA2, and OA3 groups, respectively (0 joints in the OA4 group). Metabolomic analysis identified 48 metabolites, five of which were significantly different between study groups: Mannose and betaine were elevated in the OA1 group compared with the OA2 group, and the 2-hydroxyisobutyrate concentration decreased with OA progression; in contrast, isoleucine was less concentrated in mild vs. moderate OA, and lactate increased in severe OA. This study identified different 1H-NMR metabolomic profiles of canine SF in patients with progressive degrees of spontaneous OA, suggesting 1H-NMR metabolomic analysis as a potential alternative method for monitoring OA progression. In addition, the results suggest the therapeutic potentials of the metabolomic pathways that involve mannose, betaine, 2-hydroxyisobutyrate, isoleucine, and lactate.

Anti-COVID-19, Anti-Inflammatory, and Anti-Osteoarthritis Activities of Sesamin from Sesamum indicum L

During the COVID-19 (coronavirus disease 2019) outbreak, many people were infected, and the symptoms may persist for several weeks or months for recovering patients. This is also known as "long COVID" and includes symptoms such as fatigue, joint pain, muscle pain, et cetera. The COVID-19 virus may trigger hyper-inflammation associated with cytokine levels in the body. COVID-19 can trigger inflammation in the joints, which can lead to osteoarthritis (OA), while long-term COVID-19 symptoms may lead to joint damage and other inflammation problems. According to several studies, sesame has potent anti-inflammatory properties due to its major constituent, sesamin. This study examined sesamin's anti-inflammatory, anti-osteoarthritis, and anti-COVID-19 effects. Moreover, in vivo and in vitro assays were used to determine sesamin's anti-inflammatory activity against the RAW264.7 and SW1353 cell lines. Sesamin had a dose-dependent effect (20 mg/kg) in a monoiodoacetic acid (MIA)-induced osteoarthritis rat model. Sesamin reduced paw swelling and joint discomfort. In addition, the findings indicated that sesamin suppressed the expression of iNOS (inducible nitric oxide synthase) and COX-2 (cyclooxygenase-2) in the RAW264.7 cell line within the concentration range of 6.25-50 μM. Furthermore, sesamin also had a suppressive effect on MMP (matrix metalloproteinase) expression in chondrocytes and the SW1353 cell line within the same concentration range of 6.25-50 μM. To examine the anti-viral activity, an in silico analysis was performed to evaluate sesamin's binding affinity with SARS-CoV-2 RdRp (severe acute respiratory syndrome coronavirus 2 RNA-dependent RNA polymerase) and human ACE2 (angiotensin-converting enzyme 2). Compared to the controls, sesamin exhibited strong binding affinities towards SARS-CoV-2 RdRp and human ACE2. Furthermore, sesamin had a higher binding affinity for the ACE2 target protein. This study suggests that sesamin shows potential anti-SARS-CoV-2 activity for drug development.

Quantification of chondroitin sulfate, hyaluronic acid and N-glycans in synovial fluid - A technical performance study

Objective

To validate a quantitative high performance liquid chromatography (HPLC) assay for chondroitin sulfate (CS) and hyaluronic acid (HA) in synovial fluid, and to analyze glycan-patterns in patient samples.

Design

Synovial fluid from osteoarthritis (OA, n ​= ​25) and knee-injury (n ​= ​13) patients, a synovial fluid pool (SF-control) and purified aggrecan, were chondroitinase digested and together with CS- and HA-standards fluorophore labelled prior to quantitative HPLC analysis. N-glycan profiles of synovial fluid and aggrecan were assessed by mass spectrometry.

Results

Unsaturated uronic acid and sulfated-N-acetylgalactosamine (ΔUA-GalNAc4S and ΔUA-GalNAc6S) contributed to 95% of the total CS-signal in the SF-control sample. For HA and the CS variants in SF-control the intra- and inter-experiment coefficient of variation was between 3-12% and 11-19%, respectively; tenfold dilution gave recoveries between 74 and 122%, and biofluid stability test (room temperature storage and freeze-thaw cycles) showed recoveries between 81 and 140%. Synovial fluid concentrations of the CS variants ΔUA-GalNAc6S and ΔUA2S-GalNAc6S were three times higher in the recent injury group compared to the OA group, while HA was four times lower. Sixty-one different N-glycans were detected in the synovial fluid samples, but there were no differences in levels of N-glycan classes between patient groups. The CS-profile (levels of ΔUA-GalNAc4S and ΔUA-GalNAc6S) in synovial fluid resembled that of purified aggrecan from corresponding samples; the contribution to the N-glycan profile in synovial fluid from aggrecan was low.

Conclusions

The HPLC-assay is suitable for analyzing CS variants and HA in synovial fluid samples, and the GAG-pattern differs between OA and recently knee injured subjects.

Sustained delivery of a heterodimer bone morphogenetic protein-2/7 via a collagen hydroxyapatite scaffold accelerates and improves critical femoral defect healing

Despite the glimmer of hope provided by the discovery and commercialization of bone morphogenetic protein-2 (BMP-2) as a bone graft substitute, side effects related to the use of supraphysiological doses have hindered its clinical usage. In this study, we compared the osteoinductive potential of BMP-2 homodimer with a heterodimer of BMP-2/7, both delivered via a collagen-hydroxyapatite (CHA) scaffold delivery system, with the aim to reduce the overall therapeutic BMP doses and the associated side-effects. We first show that the incorporation of hydroxyapatite in collagen-based BMP delivery systems is pivotal for achieving efficient BMP sequestration and controlled release. Using an ectopic implantation model, we then showed that the CHA+BMP-2/7 was more osteoinductive than CHA+BMP-2. Further evaluation of the molecular mechanisms responsible for this increased osteoinductivity at an early stage in the regeneration process indicated that the CHA+BMP-2/7 enhanced progenitor cell homing at the implantation site, upregulated the key transcriptomic determinants of bone formation, and increased the production of bone extracellular matrix components. Using fluorescently labelled BMP-2/7 and BMP-2, we demonstrated that the CHA scaffold provided a long-term delivery of both molecules for at least 20 days. Finally, using a rat femoral defect model, we showed that an ultra-low dose (0.5 µg) of BMP-2/7 accelerated fracture healing and performed at a level comparable to 20-times higher BMP-2 dose. Our results indicate that the sustained delivery of BMP-2/7 via a CHA scaffold could bring us a step closer in the quest for the use of physiological growth factor doses in fracture healing. STATEMENT OF SIGNIFICANCE: • Incorporation of hydroxyapatite (HA) in a collagen scaffold dramatically improves bone morphogenic protein (BMP) sequestration via biophysical interactions with BMP, thereby providing more controlled BMP release compared with pristine collagen. • We then investigate the molecular mechanisms responsible for increased osteoinductive potential of a heterodimer BMP-2/7 with is clinically used counterpart, the BMP-2 homodimer. • The superior osteoinductive properties of BMP-2/7 are a consequence of its direct positive effect on progenitor cell homing at the implantation site, which consequently leads to upregulation of cartilage and bone related genes and biochemical markers. • An ultra-low dose of BMP-2/7 delivered via a collagen-HA (CHA) scaffold leads to accelerated healing of a critical femoral defect in rats while a 20-times higher BMP-2 dose was required to achieve comparable results.

Biochanin A protects against iron overload associated knee osteoarthritis via regulating iron levels and NRF2/System xc-/GPX4 axis

BACKGROUND

Iron homeostasis plays a positive role in articular cartilage health. Excessive iron or iron overload can induce oxidative stress damage in chondrocytes and ferroptosis cell death, advancing knee osteoarthritis (KOA). However, up to date, few effective agents treat iron overload-induced KOA (IOKOA). Chinese herbal medicine (CHM) provides abundant resources for drug selection to manage bone metabolic conditions, including osteoporosis. Biochanin A (BCA) is a novel bioactive multifunctional natural compound isolated from Huangqi, which has protective effects on bone loss. Nevertheless, the function and mechanism of BCA in treating IOKOA are still elusive.

PURPOSE

This study seeks to uncover the potential therapeutic targets and mechanisms of BCA in the management of KOA with iron accumulation.

METHODS

Iron dextrin (500 mg/kg) was intraperitoneally injected into mice to establish the iron overloaded mice model. OA was induced through surgery, and the progression was evaluated eight weeks following surgery. OA severity was evaluated with micro-CT and Safranin-O/Fast green staining in vivo. Iron deposition in the knee joint and synovium was assessed using Perl's Prussian blue staining. Ferric ammonium citrate (FAC) was then administered to primary chondrocytes to evaluate iron regulators mediated iron homeostasis. Toluidine blue staining was utilized to identify chondrocytes in vitro. The vitality of the cells was assessed using the CCK-8 test. The apoptosis rate of cells was measured using Annexin V-FITC/PI assay. The intracellular iron level was detected utilizing the calcein-AM test. Reactive oxygen species (ROS), lipid-ROS, and mitochondrial membrane potentiality were reflected via fluorescence density. Utilizing RT-qPCR and western blotting, the expression level was determined.

RESULTS

Micro-CT and histological staining of knee joints showed greater cartilage degradation and higher iron buildup detected in iron-overloaded mice. BCA can reduce iron deposition and the severity of KOA. Toluidine blue staining and the CCK-8 assay indicated that BCA could rescue chondrocytes killed by iron. Cell apoptosis rates were increased due to iron overload but improved by BCA. Further, the intracellular content of iron, ROS, and lipid-ROS was increased with ferric ammonium citrate (FAC) treatment but restored after treatment with different concentrations of BCA. JC-1 staining revealed that BCA could reduce mitochondrial damage induced by iron overload.

CONCLUSION

Iron overload was shown to promote chondrocyte ferroptosis in vivo and in vitro. Moreover, iron overload suppressed the expression of collagen II and induced MMP expression by catalyzing ROS generation with mitochondrial dysfunction. Our results showed that BCA could directly reduce intracellular iron concentration by inhibiting TfR1 and promoting FPN but also target the Nrf2/system xc-/GPX4 signaling pathway to scavenge free radicals and prevent lipid peroxidation. The results of this research indicate that BCA regulates iron homeostasis during the progression of osteoarthritis, which can open a new field of treatment for KOA.

Characterization of Synovial Fluid Components: Albumin-Chondroitin Sulfate Interactions Seen through Molecular Dynamics

The friction coefficient of articular cartilage (AC) is very low. A method of producing tailor-made materials with even similar lubrication properties is still a challenge. The physicochemical reasons for such excellent lubrication properties of AC are still not fully explained; however, a crucial factor seems to be synergy between synovial fluid (SF) components. As a stepping stone to being able to produce innovative materials characterized by a very low friction coefficient, we studied the interactions between two important components of SF: human serum albumin (HSA) and chondroitin sulfate (CS). The molecular dynamics method, preceded by docking, is used in the study. Interactions of HSA with two types of CS (IV and VI), with the addition of three types of ions often found in physiological solutions: Ca2+, Na+, and Mg2+, are compared. It was found that there were differences in the energy of binding values and interaction maps between CS-4 and CS-6 complexes. HSA:CS-4 complexes were bound stronger than in the case of HSA:CS-6 because more interactions were formed across all types of interactions except one-the only difference was for ionic bridges, which were more often found in HSA:CS-6 complexes. RMSD and RMSF indicated that complexes HSA:CS-4 behave much more stably than HSA:CS-6. The type of ions added to the solution was also very important and changed the interaction map. However, the biggest difference was caused by the addition of Ca2+ ions which were prone to form ionic bridges.

Lipid Metabolism in Cartilage Development, Degeneration, and Regeneration

Lipids affect cartilage growth, injury, and regeneration in diverse ways. Diet and metabolism have become increasingly important as the prevalence of obesity has risen. Proper lipid supplementation in the diet contributes to the preservation of cartilage function, whereas excessive lipid buildup is detrimental to cartilage. Lipid metabolic pathways can generate proinflammatory substances that are crucial to the development and management of osteoarthritis (OA). Lipid metabolism is a complicated metabolic process involving several regulatory systems, and lipid metabolites influence different features of cartilage. In this review, we examine the current knowledge about cartilage growth, degeneration, and regeneration processes, as well as the most recent research on the significance of lipids and their metabolism in cartilage, including the extracellular matrix and chondrocytes. An in-depth examination of the involvement of lipid metabolism in cartilage metabolism will provide insight into cartilage metabolism and lead to the development of new treatment techniques for metabolic cartilage damage.

Pharmacological characterization of GLPG1972/S201086, a potent and selective small-molecule inhibitor of ADAMTS5

OBJECTIVE

A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) is a key enzyme in degradation of cartilage in osteoarthritis (OA). We report the pharmacological characterization of GLPG1972/S201086, a new, potent and selective small-molecule ADAMTS5 inhibitor.

METHODS

Potency and selectivity of GLPG1972/S201086 for ADAMTS5 were determined using fluorescently labeled peptide substrates. Inhibitory effects of GLPG1972/S201086 on interleukin-1α-stimulated glycosaminoglycan release in mouse femoral head cartilage explants and on interleukin-1β-stimulated release of an ADAMTS5-derived aggrecan neoepitope (quantified with ELISA) in human articular cartilage explants were determined. In the destabilization of the medial meniscus (DMM) mouse and menisectomized (MNX) rat models, effects of oral GLPG1972/S201086 on relevant OA histological and histomorphometric parameters were evaluated.

RESULTS

GLPG1972/S201086 inhibited human and rat ADAMTS5 (IC50 ± SD: 19 ± 2 nM and <23 ± 1 nM, respectively), with 8-fold selectivity over ADAMTS4, and 60->5,000-fold selectivity over other related proteases in humans. GLPG1972/S201086 dose-dependently inhibited cytokine-stimulated aggrenolysis in mouse and human cartilage explants (100% at 20 μM and 10 μM, respectively). In DMM mice, GLPG1972/S201086 (30-120 mg/kg b.i.d) vs vehicle reduced femorotibial cartilage proteoglycan loss (23-37%), cartilage structural damage (23-39%) and subchondral bone sclerosis (21-36%). In MNX rats, GLPG1972/S201086 (10-50 mg/kg b.i.d) vs vehicle reduced cartilage damage (OARSI score reduction, 6-23%), and decreased proteoglycan loss (∼27%) and subchondral bone sclerosis (77-110%).

CONCLUSIONS

GLPG1972/S201086 is a potent, selective and orally available ADAMTS5 inhibitor, demonstrating significant protective efficacy on both cartilage and subchondral bone in two relevant in vivo preclinical OA models.

Safety, Pharmacokinetics, and Pharmacodynamics of the ADAMTS-5 Inhibitor GLPG1972/S201086 in Healthy Volunteers and Participants With Osteoarthritis of the Knee or Hip

GLPG1972/S201086 is a disintegrin and metalloproteinase with thrombospondin motif‐5 (ADAMTS‐5) inhibitor in development as an osteoarthritis disease‐modifying therapy. We report the safety, tolerability, pharmacokinetics, and pharmacodynamics (turnover of plasma/serum ARGS‐aggrecan neoepitope fragments [ARGS]) of GLPG1972 in 3 randomized, double‐blind, placebo‐controlled phase 1 trials. Study A, a first‐in‐human trial of single (≤2100 mg [fasted] and 300 mg [fed]) and multiple (≤1050 mg once daily [fed]; 14 days) ascending oral (solution) doses, investigated GLPG1972 in healthy men (N = 41; NCT02612246). Study B investigated multiple ascending oral (tablet) doses of GLPG1972 (≤300 mg once daily [fed]; 4 weeks) in male and female participants with osteoarthritis (N = 30; NCT03311009). Study C investigated single (Japanese: ≤1500 mg; White: 300 mg [fasted]) and multiple (Japanese, ≤1050 mg once daily; White, 300 mg once daily [fed]; 14 days) ascending oral (tablet) doses of GLPG1972 in healthy Japanese and White men (N = 88). The pharmacokinetic profile of GLPG1972 was similar between healthy participants and participants with osteoarthritis, with low to moderate interindividual variability. GLPG1972 was rapidly absorbed (median time to maximum concentration, 4 hours), and eliminated with a mean apparent terminal elimination half‐life of ≈10 hours. Steady state was achieved within 2 days of dosing, with minimal accumulation. Steady‐state plasma exposure after 300 mg of GLPG1972 showed no or minor differences between populations. Area under the plasma concentration–time curve (56.8‐67.6 μg · h/mL) and time to maximum concentration (4 hours) were similar between studies. Urinary excretion of GLPG1972 (24 hours) was low (<11%). Multiple dosing significantly reduced ARGS levels vs baseline at all time points for all doses vs placebo. GLPG1972 was generally well tolerated at all doses.

NMR-Based Metabolomics Revealed the Underlying Inflammatory Pathology in Reactive Arthritis Synovial Joints

Reactive arthritis (ReA) is an aseptic synovitis condition that often develops 2-4 weeks after a distant (extra-articular) infection with Chlamydia, Salmonella, Shigella, Campylobacter, and Yersinia species. The metabolic changes in the synovial fluid (SF) may serve as indicative markers to both improve the diagnostic accuracy and understand the underlying inflammatory pathology of ReA. With this aim, the metabolic profiles of SF collected from ReA (n = 58) and non-ReA, i.e., rheumatoid arthritis (RA, n = 21) and osteoarthritis (OA, n = 20) patients, respectively, were measured using NMR spectroscopy and compared using orthogonal partial least-squares discriminant analysis (OPLS-DA). The discriminatory metabolic features were further evaluated for their diagnostic potential using the receiver operating characteristic (ROC) curve analysis. Compared to RA, two (alanine and carnitine), and compared to OA, six (NAG, glutamate, glycerol, isoleucine, alanine, and glucose) metabolic features were identified as diagnostic biomarkers. We further demonstrated the impact of ReA synovitis condition on the serum metabolic profiles through performing a correlation analysis. The Pearson rank coefficient (r) was estimated for 38 metabolites (profiled in both SF and serum samples obtained in pair from ReA patients) and was found significantly positive for 71% of the metabolites (r ranging from 0.17 to 0.87).

An Anterior Cruciate Ligament Rupture Increases Levels of Urine N-terminal Cross-linked Telopeptide of Type I Collagen, Urine C-terminal Cross-linked Telopeptide of Type II Collagen, Serum Aggrecan ARGS Neoepitope, and Serum Tumor Necrosis Factor-α

BACKGROUND

An anterior cruciate ligament (ACL) rupture results in an increased risk of developing knee osteoarthritis (OA) at an early age. Before clinical signs become apparent, the OA process has already been initiated. Therefore, it is important to look at the cascade of changes, such as the activity of cytokines and proteases, which might be associated with the later development of OA.

PURPOSE

To compare biomarker levels in patients with a recent ACL rupture with those in controls with a healthy knee and to monitor biomarker levels over 2 years after an ACL rupture.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Patients were enrolled after an ACL tear was identified. Serum and urine samples were collected at the time of enrollment in the study (3-25 weeks after the injury) and then at 14 and 27 months after the injury between January 2009 and November 2010. Reference samples were obtained from participants with healthy knees. The following biomarkers were measured with immunological assays: aggrecan ARGS neoepitope (ARGS-aggrecan), tumor necrosis factor-α (TNF-α), interferon-γ, interleukin (IL)-8, IL-10, IL-13, N-terminal cross-linked telopeptide of type I collagen (NTX-I), and C-terminal cross-linked telopeptide of type II collagen (CTX-II).

RESULTS

Samples were collected from 152 patients with an acute ACL rupture, who had a median age of 25 years (interquartile range [IQR], 21-32 years). There were 62 urine reference samples (median age, 25 years [IQR, 22-36 years]) and 26 serum reference samples (median age, 35 years [IQR, 24-39 years]). At a median of 11 weeks (IQR, 7-17 weeks) after trauma, serum levels of both ARGS-aggrecan and TNF-α were elevated 1.5-fold (P < .001) compared with reference samples and showed a time-dependent decrease during follow-up. Urine NTX-I and CTX-II concentrations were elevated in an early phase after trauma (1.3-fold [P < .001] and 3.7-fold [P < .001], respectively) compared with reference samples, and CTX-II levels remained elevated compared with reference samples at 2-year follow-up. Strong correlations were found between serum ARGS-aggrecan, urinary NTX-I, and urinary CTX-II (r_s = 0.57-0.68).

CONCLUSION

In the first few months after an ACL injury, there was a measurable increase in serum levels of ARGS-aggrecan and TNF-α as well as urine levels of NTX-I and CTX-II. These markers remained high compared with those of controls with healthy knees at 2-year follow-up.

Targeting Dysregulation of Metalloproteinase Activity in Osteoarthritis

Metalloproteinases were first identified as collagen cleaving enzymes and are now appreciated to play important roles in a wide variety of biological processes. The aberrant activity and dysregulation of the metalloproteinase family are linked to numerous diseases including cardiovascular and pulmonary diseases, chronic wounds, cancer, fibrosis and arthritis. Osteoarthritis (OA) is the most prevalent age-related joint disorder that causes pain and disability, but there are no disease-modifying drugs available. The hallmark of OA is loss of articular cartilage and elevated activities of matrix-degrading metalloproteinases are responsible. These enzymes do not exist in isolation and their activity is tightly regulated by a number of processes, such as transcription, proteolytic activation, interaction with their inhibitors, cell surface and extracellular matrix molecules, and endocytic clearance from the extracellular milieu. Here, we describe the functions and roles of metalloproteinase family in OA pathogenesis. We highlight recent studies that have illustrated novel mechanisms regulating their extracellular activity and impairment of such regulations that lead to the development of OA. We also discuss how to stop or slow down the degenerative processes by targeting aberrant metalloproteinase activity, which may in future become therapeutic interventions for the disease.

A Pilot Clinical Study of Hyperacute Serum Treatment in Osteoarthritic Knee Joint: Cytokine Changes and Clinical Effects

The serum fraction of platelet-rich fibrin (hyperacute serum) has been shown to improve cartilage cell proliferation in in vitro osteoarthritic knee joint models. We hypothesize that hyperacute serum may be a potential regenerative therapeutic for osteoarthritic knees. In this study, the cytokine milieu at the synovial fluid of osteoarthritic knee joints exposed to hyperacute serum intraarticular injections was investigated. Patients with knee osteoarthritis received three injections of autologous hyperacute serum; synovial fluid was harvested before each injection and clinical monitoring was followed-up for 6 months. Forty osteoarthritic-related cytokines, growth factors and structural proteins from synovial fluid were quantified and analysed by Multivariate Factor Analysis. Hyperacute serum provided symptomatic relief regarding pain and joint stability for OA patients. Both patients "with" and "without effusion knees" had improved VAS, KOOS and Lysholm-Tegner scores 6 months after of hyperacute serum treatment. Synovial fluid analysis revealed two main clusters of proteins reacting together as a group, showing strong and significant correlations with their fluctuation patterns after hyperacute serum treatment. In conclusion, hyperacute serum has a positive effect in alleviating symptoms of osteoarthritic knees. Moreover, identified protein clusters may allow the prediction of protein expression, reducing the number of investigated proteins in future studies.

Therapeutic Potential of Bioactive Compounds in Honey for Treating Osteoarthritis

Dysregulation of joint tissue homeostasis induces articular degenerative changes and musculoskeletal diseases such as osteoarthritis. This pathology represents the first cause of motor disability in individuals over 60 years of age, impacting their quality of life and the costs of health systems. Nowadays, pharmacological treatments for cartilage disease have failed to achieve full tissue regeneration, resulting in a functional loss of the joint; therefore, joint arthroplasty is the gold standard procedure to cure this pathology in severe cases of Osteoarthritis. A different treatment is the use of anti-inflammatory drugs which mitigate pain and inflammation in some degree, but without significant inhibition of disease progression. In this sense, new therapeutic alternatives based on natural compounds have been proposed to delay osteoarthritis progression, particularly those agents that regulate articular homeostasis. Preclinical studies have shown a therapeutic application of honey and its bioactive compounds, ranging from treating wounds, coughs, skin infections, and are also used as a biological stimulant by exerting antioxidant and anti-inflammatory properties. In this article, we reviewed the current medicinal applications of honey with particular emphasis on its use regulating articular homeostasis by inhibiting inflammation and oxidative stress.

Higher aggrecan 1-F21 epitope concentration in synovial fluid early after anterior cruciate ligament injury is associated with worse knee cartilage quality assessed by gadolinium enhanced magnetic resonance imaging 20 years later

Background

To investigate if cartilage related biomarkers in synovial fluid are associated with knee cartilage status 20 years after an anterior cruciate ligament (ACL) injury.

Methods

We studied 25 patients with a complete ACL rupture without subsequent ACL reconstruction or radiographic knee OA. All had a delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) 20 years after the ACL injury, using the T1 transverse relaxation time in the presence of gadolinium (T1Gd) which estimates the concentration of glycosaminoglycans in hyaline cartilage. Synovial fluid samples were aspirated acutely (between 0 and 18 days) and during 1 to 5 follow up visits between 0.5 and 7.5 years after injury. We quantified synovial fluid concentrations of aggrecan (epitopes 1-F21 and ARGS), cartilage oligomeric matrix protein, matrix metalloproteinase-3 and tissue inhibitor of metalloproteinase-1 by immunoassays, and sulfated glycosaminoglycans by Alcian blue precipitation. Western blot was used for qualitative analyses of aggrecan fragments in synovial fluid and cartilage samples.

Results

Western blot indicated that the 1-F21 epitope was located within the chondroitin sulfate 2 region of aggrecan. Linear regression analyses (adjusted for age, sex, body mass index and time between injury and sampling) showed that acute higher synovial fluid 1-F21-aggrecan concentrations were associated with shorter T1Gd values 20 years after injury, i.e. inferior cartilage quality (standardized effects between − 0.67 and − 1.0). No other statistically significant association was found between molecular biomarkers and T1Gd values.

Conclusion

Higher acute synovial fluid 1-F21-aggrecan concentrations in ACL injured patients, who managed to cope without ACL reconstruction and were without radiographic knee OA, were associated with inferior knee cartilage quality assessed by dGEMRIC 20 years after injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03819-9.

Reconsideration of the Semaphorin-3A Binding Motif Found in Chondroitin Sulfate Using Galnac4s-6st-Knockout Mice

The chondroitin sulfate (CS)-rich dense extracellular matrix surrounding neuron cell bodies and proximal dendrites in a mesh-like structure is called a perineuronal net (PNN). CS chains in PNNs control neuronal plasticity by binding to PNN effectors, semaphorin-3A (Sema3A) and orthodenticle homeobox 2. Sema3A recognizes CS-containing type-E disaccharide units (sulfated at O-4 and O-6 of N-acetylgalactosamine). Type-E disaccharide units are synthesized by N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST). In this study, we demonstrated that Sema3A accumulates in the PNNs surrounding parvalbumin cells, even in mice deficient in GalNAc4S-6ST. In addition, there were no differences in the number and structure of PNNs visualized by Cat316 antibody and Wisteria floribunda lectin, which recognize CS chains, between wild type and GalNAc4S-6ST knockout mice. Therefore, we re-examined the Sema3A binding motif found in CS chains using chemically synthesized CS tetrasaccharides. As a result, we found that non-sulfated GalNAc residues at the non-reducing termini of CS chains are required for the binding of Sema3A.

Proteomic analysis reveals dexamethasone rescues matrix breakdown but not anabolic dysregulation in a cartilage injury model

Objectives

In this exploratory study, we used discovery proteomics to follow the release of proteins from bovine knee articular cartilage in response to mechanical injury and cytokine treatment. We also studied the effect of the glucocorticoid Dexamethasone (Dex) on these responses.

Design

Bovine cartilage explants were treated with either cytokines alone (10 ng/ml TNFα, 20 ng/ml IL-6, 100 ng/ml sIL-6R), a single compressive mechanical injury, cytokines and injury, or no treatment, and cultured in serum-free DMEM supplemented with 1% ITS for 22 days. All samples were incubated with or without addition of 100 nM Dex. Mass spectrometry and western blot analyses were performed on medium samples for the identification and quantification of released proteins.

Results

We identified 500 unique proteins present in all three biological replicates. Many proteins involved in the catabolic response of cartilage degradation had increased release after inflammatory stress. Dex rescued many of these catabolic effects. The release of some proteins involved in anabolic and chondroprotective processes was inconsistent, indicating differential effects on processes that may protect cartilage from injury. Dex restored only a small fraction of these to the control state, while others had their effects exacerbated by Dex exposure.

Conclusions

We identified proteins that were released upon cytokine treatment which could be potential biomarkers of the inflammatory contribution to cartilage degradation. We also demonstrated the imperfect rescue of Dex on the effects of cartilage degradation, with many catabolic factors being reduced, while other anabolic or chondroprotective processes were not.

Ex Vivo Equine Cartilage Explant Osteoarthritis Model: A Metabolomics and Proteomics Study

Osteoarthritis is an age-related degenerative musculoskeletal disease characterized by loss of articular cartilage, synovitis, and subchondral bone sclerosis. Osteoarthritis pathogenesis is yet to be fully elucidated with no osteoarthritis-specific biomarkers in clinical use. Ex vivo equine cartilage explants (n = 5) were incubated in tumor necrosis factor-α (TNF-α)/interleukin-1β (IL-1β)-supplemented culture media for 8 days, with the media removed and replaced at 2, 5, and 8 days. Acetonitrile metabolite extractions of 8 day cartilage explants and media samples at all time points underwent one-dimensional (1D) ¹H nuclear magnetic resonance metabolomic analysis, with media samples also undergoing mass spectrometry proteomic analysis. Within the cartilage, glucose and lysine were elevated following TNF-α/IL-1β treatment, while adenosine, alanine, betaine, creatine, myo-inositol, and uridine decreased. Within the culture media, 4, 4, and 6 differentially abundant metabolites and 154, 138, and 72 differentially abundant proteins were identified at 1–2, 3–5, and 6–8 days, respectively, including reduced alanine and increased isoleucine, enolase 1, vimentin, and lamin A/C following treatment. Nine potential novel osteoarthritis neopeptides were elevated in the treated media. Implicated pathways were dominated by those involved in cellular movement. Our innovative study has provided insightful information on early osteoarthritis pathogenesis, enabling potential translation for clinical markers and possible new therapeutic targets.

IL-15 and IL15RA in Osteoarthritis: Association With Symptoms and Protease Production, but Not Structural Severity

Objective: Interleukin-15 (IL-15) is a pro-inflammatory cytokine that is increased in joint fluids of early-stage osteoarthritis (OA) patients, and has been associated with expression of proteases that can damage cartilage, and the development of neuropathic pain-like symptoms (NP) after nerve injury. The objective of this study was to further explore the role of IL-15 in the pathogenesis of OA cartilage degeneration and test genetic variation in the IL-15 receptor α gene (IL15RA) for an association with OA with radiographic severity and symptoms. Methods: Cartilage samples from donors (n = 10) were analyzed for expression of the IL15 receptor α-chain using immunohistochemistry, and for responses to IL-15 in vitro using explant cultures. Data from two independent Nottinghamshire-based studies (n = 795 and n = 613) were used to test genetic variants in the IL15RA gene (rs2228059 and rs7097780) for an association with radiographic severity, symptomatic vs. asymptomatic OA and NP. Results: IL-15Rα was expressed in chondrocytes from cartilage obtained from normal and degenerative knees. IL-15 significantly increased the release of matrix metalloproteinase-1 and -3 (MMP-1 and -3), but did not affect loss of proteoglycan from the articular matrix. Genetic variants in the IL15RA gene are associated with risk of symptomatic vs. asymptomatic OA (rs7097780 OR = 1.48 95% 1.10-1.98 p < 0.01) and with the risk of NP post-total joint replacement (rs2228059 OR = 0.76 95% 0.63-0.92 p < 0.01) but not with radiographic severity. Conclusions: In two different cohorts of patients, we show an association between genetic variation at the IL15 receptor and pain. Although ex vivo cartilage explants could respond to IL-15 with increased protease production, we found no effect of IL-15 on cartilage matrix loss and no association between IL15RA variants and radiographic severity. Together, these results suggest that IL-15 signaling may be a target for pain, but may not impact structural progression, in OA.

Analysis of Aggrecanase Activity Using Neoepitope Antibodies

Aggrecan is a major matrix component of articular cartilage, and its dysregulated proteolysis is a crucial event in the pathogenesis of arthritis. Aggrecanases, members of ADAMTS family, play a pivotal role in aggrecan degradation with ADAMTS-4 and ADAMTS-5 being key enzymes. Cleavage events mediated by ADAMTSs are highly specific and very well characterized; therefore, it is possible to investigate aggrecanolysis by using antibodies reacting with the new N- and C-termini of the cleavage products (neoepitope antibodies). Here, we present a method for analyzing dynamic aggrecanolysis by Western blotting using neoepitope antibodies in combination with antibodies against total aggrecan fragments. The protocol is robust and has a broad application for investigation of aggrecanase activity in vitro and ex vivo.

Anti-Inflammatory and Anticancer Properties of Bioactive Compounds from Sesamum indicum L.-A Review

The use of foodstuff as natural medicines has already been established through studies demonstrating the pharmacological activities that they exhibit. Knowing the nutritional and pharmacological significance of foods enables the understanding of their role against several diseases. Among the foods that can potentially be considered as medicine, is sesame or Sesamum indicum L., which is part of the Pedaliaceae family and is composed of its lignans such as sesamin, sesamol, sesaminol and sesamolin. Its lignans have been widely studied and are known to possess antiaging, anticancer, antidiabetes, anti-inflammatory and antioxidant properties. Modern chronic diseases, which can transform into clinical diseases, are potential targets of these lignans. The prime example of chronic diseases is rheumatic inflammatory diseases, which affect the support structures and the organs of the body and can also develop into malignancies. In line with this, studies emphasizing the anti-inflammatory and anticancer activities of sesame have been discussed in this review.

Synovial fluid proteome changes in ACL injury-induced posttraumatic osteoarthritis: Proteomics analysis of porcine knee synovial fluid

Surgical transection of the anterior cruciate ligament (ACL) in the porcine model leads to posttraumatic osteoarthritis if left untreated. However, a recently developed surgical treatment, bridge-enhanced ACL repair, prevents further cartilage damage. Since the synovial fluid bathes all the intrinsic structures of knee, we reasoned that a comparative analysis of synovial fluid protein contents could help to better understand the observed chondroprotective effects of the bridge-enhanced ACL repair. We hypothesized that post-surgical changes in the synovial fluid proteome would be different in the untreated and repaired knees, and those changes would correlate with the degree of cartilage damage. Thirty adolescent Yucatan mini-pigs underwent unilateral ACL transection and were randomly assigned to either no further treatment (ACLT, n = 14) or bridge-enhanced ACL repair (BEAR, n = 16). We used an isotopically labeled high resolution LC MS/MS-based proteomics approach to analyze the protein profile of synovial fluid at 6 and 12 months after ACL transection in untreated and repaired porcine knees. A linear mixed effect model was used to compare the normalized protein abundance levels between the groups at each time point. Bivariate linear regression analyses were used to assess the correlations between the macroscopic cartilage damage (total lesion area) and normalized abundance levels of each of the identified secreted proteins. There were no significant differences in cartilage lesion area or quantitative abundance levels of the secreted proteins between the ACLT and BEAR groups at 6 months. However, by 12 months, greater cartilage damage was seen in the ACLT group compared to the BEAR group (p = 0.005). This damage was accompanied by differences in the abundance levels of secreted proteins, with higher levels of Vitamin K-dependent protein C (p = 0.001), and lower levels of Apolipoprotein A4 (p = 0.021) and Cartilage intermediate layer protein 1 (p = 0.049) in the ACLT group compared to the BEAR group. There were also group differences in the secreted proteins that significantly changed in abundance between 6 and 12 months in ACLT and BEAR knees. Increased concentration of Ig lambda-1 chain C regions and decreased concentration of Hemopexin, Clusterin, Coagulation factor 12 and Cartilage intermediate layer protein 1 were associated with greater cartilage lesion area. In general, ACLT knees had higher concentrations of pro-inflammatory proteins and lower concentrations of anti-inflammatory proteins than BEAR group. In addition, the ACLT group had a lower and declining synovial concentrations of CILP, in contrast to a consistently high abundance of CILP in repaired knees. These differences suggest that the knees treated with bridge-enhanced ACL repair may be maintaining an environment that is more protective of the extracellular matrix, a function which is not seen in the ACLT knees.

Proteomic analysis of synovial fluid: current and potential uses to improve clinical outcomes

INTRODUCTION

Synovial fluid (SF) is in close proximity to tissues which are primarily altered during articular disease and has significant potential to better understand the underlying disease pathogeneses of articular pathologies and biomarker discovery. Although development of mass spectrometry-based methods has allowed faster and higher sensitivity techniques, interrogation of the SF proteome has been hindered by its large protein concentration dynamic range, impeding quantification of lower abundant proteins. Areas covered: Recent advances have developed methodologies to reduce the large protein concentration dynamic range of SF and subsequently allow deeper exploration of the SF proteome. This review concentrates on methods to overcome biofluid complexity, mass spectrometry proteomics methodologies, extracellular vesicles proteomics and the application of advances within the field in clinical disease, including osteoarthritis, rheumatoid arthritis, spondyloarthritis and juvenile arthritis. A narrative review was conducted with articles searched using PubMed, 1991-2018. Expert opinion: The SF proteomics field faces various challenges, including the requirement for rigorous and standardised methods of sample collection/storage, the sensitivity and specificity of proteomic assays, techniques to combat the large protein concentration dynamic range and comprehensive data analysis to reduce falsely identified markers. Additionally, there are challenges in developing multi 'omic' integration techniques, with computational integration enhancing analysis.

Proteoglycans isolated from the bramble shark cartilage show potential anti-osteoarthritic properties

Osteoarthritis (OA) causes articular cartilage destruction, initiating pain and inflammation in the joints, resulting in joint disability. Medications are available to manage these symptoms; however, their effects on the disease progression are limited. Loss of proteoglycans (PGs) was reported to contribute articular cartilage destruction in OA. Therapeutics approaches were previously studied in the animal models of OA. In the present study, we investigated the oral efficacy of four dosages of PGs (25 mg/kg, 50 mg/kg, 100 mg/kg and 200 mg/kg), isolated from the bramble shark cartilage, in an animal model of OA. Indomethacin was used as a bioequivalent formulation. Primarily, the mass spectrum analysis of the purified PGs obtained from bramble shark cartilage revealed the presence of two unique peptides including AGWLSDGSVR and LDGNPINLSK, that showed sequence similarity with aggrecan core-protein and epiphycan, respectively. The levels of C-reactive protein and uric acid in the OA rats were reduced when treated with PGs. Histopathology analysis displayed less cartilage erosion and neovascularization in OA rats treated with PGs. The X-ray imaging presented higher bone density with 200 mg/kg dosage of PG treatment in OA rats. The expressions of the inflammatory modulators including TNF-α, IL-1β, MMP13, NOS2, IL-10 and COX-2 were found to be moderated with PG treatment. In addition, PG treatment maintained the activities of antioxidant enzymes, including SOD and catalase in the joint tissues with a higher GSH content, in a dose-dependent manner. Taken together, our preliminary findings report the anti-osteoarthritic properties of PGs and recommend to evaluate its efficacy and safety in randomized trials.

1H NMR Metabolomics Identifies Underlying Inflammatory Pathology in Osteoarthritis and Rheumatoid Arthritis Synovial Joints

Despite osteoarthritis (OA) and rheumatoid arthritis (RA) being typically age-related, their underlying etiologies are markedly different. We used ¹H nuclear magnetic resonance (NMR) spectroscopy to identify differences in metabolite profiles in low volumes of OA and RA synovial fluid (SF). SF was aspirated from knee joints of 10 OA and 14 RA patients. 100 μL SF was analyzed using a 700 MHz Avance IIIHD Bruker NMR spectrometer with a TCI cryoprobe. Spectra were analyzed by Chenomx, Bruker TopSpin and AMIX software. Statistical analysis was undertaken using Metaboanalyst. 50 metabolites were annotated, including amino acids, saccharides, nucleotides and soluble lipids. Discriminant analysis identified group separation between OA and RA cohorts, with 32 metabolites significantly different between OA and RA SF (false discovery rate (FDR) < 0.05). Metabolites of glycolysis and the tricarboxylic acid cycle were lower in RA compared to OA; these results concur with higher levels of inflammation, synovial proliferation and hypoxia found in RA compared to OA. Elevated taurine in OA may indicate increased subchondral bone sclerosis. We demonstrate that quantifiable differences in metabolite abundance can be measured in low volumes of SF by ¹H NMR spectroscopy, which may be clinically useful to aid diagnosis and improve understanding of disease pathogenesis.

The Zonal Architecture of the Mandibular Condyle Requires ADAMTS5

Temporomandibular joint (TMJ) osteoarthritis (TMJOA) disrupts extracellular matrix (ECM) homeostasis, leading to cartilage degradation. Upregulated a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5 leads to cleavage of its substrate aggrecan (Acan) and is considered a hallmark of TMJOA. However, most research on ADAMTS5-Acan turnover has focused on hyaline cartilage, not fibrocartilage, which comprises the TMJ. The mandibular condylar cartilage (MCC) of the TMJ is organized in zones, and chondrocytes are arranged in axial rows, yet the molecular mechanisms required to generate the MCC zonal architecture have not been elucidated. Here, we test the hypothesis that ADAMTS5 is required for development of the TMJ MCC. Adamts5^+/+ and Adamts5^-/- murine TMJs were harvested at postnatal day 7 (P7), P21, 2 mo, and 6 mo of age; histomorphometrics indicated increased ECM. Immunohistochemistry and Western blots demonstrated the expanded ECM correlated with increased Acan localization in Adamts5^-/- compared to Adamts5^+/+. Cell volume was also decreased in the MCC of Adamts5^-/- due to both a reduction in cell size and less mature hypertrophic chondrocytes. Analysis of chondrogenic maturation markers by quantitative real-time polymerase chain reaction indicated Col2a1, Col10a1, and Sox9 were significantly reduced in Adamts5^-/- MCC compared to that of Adamts5^+/+. The older (6 mo) Adamts5^-/- MCC exhibited changes in chondrogenic cell arrangements, including clustering and chondrogenic atrophy, that correlated with early stages of TMJOA using modified Mankin scoring. These data indicate a potentially novel and critical role of ADAMTS5 for maturation of hypertrophic chondrocytes and establishment of the zonal architecture that, when disrupted, may lead to early onset of TMJOA.

Keratan sulfate, a complex glycosaminoglycan with unique functional capability

From an evolutionary perspective keratan sulfate (KS) is the newest glycosaminoglycan (GAG) but the least understood. KS is a sophisticated molecule with a diverse structure, and unique functional roles continue to be uncovered for this GAG. The cornea is the richest tissue source of KS in the human body but the central and peripheral nervous systems also contain significant levels of KS and a diverse range of KS-proteoglycans with essential functional roles. KS also displays important cell regulatory properties in epithelial and mesenchymal tissues and in bone and in tumor development of diagnostic and prognostic utility. Corneal KS-I displays variable degrees of sulfation along the KS chain ranging from non-sulfated polylactosamine, mono-sulfated and disulfated disaccharide regions. Skeletal KS-II is almost completely sulfated consisting of disulfated disaccharides interrupted by occasional mono-sulfated N-acetyllactosamine residues. KS-III also contains highly sulfated KS disaccharides but differs from KS-I and KS-II through 2-O-mannose linkage to serine or threonine core protein residues on proteoglycans such as phosphacan and abakan in brain tissue. Historically, the major emphasis on the biology of KS has focused on its sulfated regions for good reason. The sulfation motifs on KS convey important molecular recognition information and direct cell behavior through a number of interactive proteins. Emerging evidence also suggest functional roles for the poly-N-acetyllactosamine regions of KS requiring further investigation. Thus further research is warranted to better understand the complexities of KS.

Protective effect of adenovirus-mediated erythropoietin expression on the spiral ganglion neurons in the rat inner ear

The aim of the present study was to evaluate the expression of erythropoietin (Epo) and the Epo receptor (Epo-R) in the spiral ganglion neurons (SGNs) of the rat inner ear, and to assess the effect of Epo adenovirus vector (Ad-Epo) on the spontaneous apoptosis of SGNs. A total of 60 ears from 30 healthy neonatal (2-3 days postnatal) Sprague-Dawley rats were used to examine the expression of Epo in the SGNs. The rats were divided into three groups: The negative control group, the vector control group [infected with a green fluorescent protein expression vector (Ad-GFP)] and the Ad-Epo group (infected with Ad-Epo). The expression of Epo and Epo-R was detected by immunohistochemistry and dual immunofluorescence staining using polyclonal antibodies directed against Epo and Epo-R, followed by confocal laser-scanning microscopy. An adenovirus vector was constructed and used to transfect the cultured SGNs. Following adenovirus infection, apoptosis of the SGNs was evaluated and Epo protein expression was assessed. Epo and Epo-R were widely expressed in the plasma membrane and the cytoplasm of the SGNs, as well as in the organ of Corti and the stria vascularis within the inner ear. Epo protein expression was upregulated in the Ad-Epo group compared with that in the other two groups (P<0.05). Apoptotic cells were seldom observed at day 4 of SGN culture in the negative control group. At day 7, marked apoptotic cells were detected in the negative control group and the vector control group. The apoptosis level in the Ad-Epo group was significantly decreased compared with that in the negative control group or the vector control group at day 7 (P<0.05). In conclusion, Epo and Epo-R are expressed in the SGNs of the inner ear of the rat, and Ad-Epo can decrease the spontaneous apoptosis of SGNs, which may provide a basis for the prevention or alleviation of sensorineural hearing loss.

The pericellular hyaluronan of articular chondrocytes

The story of hyaluronan in articular cartilage, pericellular hyaluronan in particular, essentially is also the story of aggrecan. Without properly tethered aggrecan, the load bearing function of cartilage is compromised. The anchorage of aggrecan to the cell surface only occurs due to the binding of aggrecan to hyaluronan-with hyaluronan tethered either to a hyaluronan synthase or by multivalent binding to CD44. In this review, details of hyaluronan synthesis are discussed including how HAS2 production of hyaluronan is necessary for normal chondrocyte development and matrix assembly, how an abundance or deficit of pericellular hyaluronan alters chondrocyte metabolism, and whether hyaluronan size matters or changes with aging or disease. The biomechanical role and matrix assembly function of hyaluronan in addition to the functions of hyaluronidases are discussed. The turnover of hyaluronan is considered including mechanisms by which its turnover, at least in part, is mediated by endocytosis by chondrocytes and regulated by aggrecan degradation. Differences between turnover and clearance of newly synthesized hyaluronan and aggrecan versus the half-life of hyaluronan remaining within the inter-territorial matrix of cartilage are discussed. The release of neutral pH-acting hyaluronidase activity remains one unanswered question concerning the loss of cartilage hyaluronan in osteoarthritis. Signaling events driven by changes in hyaluronan-chondrocyte interactions may involve a chaperone function of CD44 with other receptors/cofactors as well as the changes in hyaluronan production functioning as a metabolic rheostat.

Depletion of aquaporin 1 decreased ADAMTS‑4 expression in human chondrocytes

Inflammation serves an important role in the progression of osteoarthritis (OA), and IL-1β may act as a catabolic factor on cartilage, reducing the synthesis of primary cartilage components type II collagen and aggrecan. Aquaporin 1 (AQP1) is a 28-kDa water channel formed of six transmembrane domains on the cell membrane. AQP1 is highly expressed in the anus, gallbladder and liver, and is moderately expressed in the hippocampus, ependymal cells of the central nervous system and articular cartilage. It was hypothesized that AQP1 may be highly expressed in OA cartilage and that it may increase the expression of catabolic factors during inflammatory OA progression. Therefore, the present study evaluated AQP1 functions in human OA articular chondrocytes. Primary chondrocytes were isolated from human hip and knee cartilage tissues, cultured and transfected with AQP1-specific small interfering RNA with or without subsequent IL-1β treatment. In vitro explant culture from hip cartilages were also prepared. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to assess the expression of AQP genes in human articular cartilage, AQP1 immunohistochemistry of the cartilages and explant culture, as well as RT-quantitative PCR, western blotting and immunocytochemistry/immunofluorescence of OA chondrocytes to evaluate the expression of AQP1, and catabolic and anabolic factors. RT-PCR results demonstrated that AQP0, 1, 3, 7, 9, and 11 were expressed in OA chondrocytes. Immunohistochemistry revealed that AQP1 was highly expressed in the superficial to middle zones of OA articular cartilages. Additionally, AQP1 mRNA was significantly higher in OA cartilage and IL-1β treatment significantly increased AQP1 expression in hip explant cartilage. Furthermore, AQP1 downregulation decreased a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS)-4 expression in OA chondrocytes, though it did not affect other associated genes. Immunofluorescence showed that AQP1 and ADAMTS-4 were co-localized. These findings indicated that AQP1 depletion may decrease ADAMTS-4 expression in human OA chondrocytes. Therefore, regulating AQP1 expression may be a strategy to suppress catabolic factors during OA progression.

Hemoglobin stimulates the expression of ADAMTS-5 and ADAMTS-9 by synovial cells: a possible cause of articular cartilage damage after intra-articular hemorrhage

Background

ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs) proteins play an important pathological role in matrix degeneration. Aggrecan degradation is a significant and critical event in early-stage osteoarthritis. To determine the effect of hemoglobin (Hb) on the ability of synovial tissues to produce ADAMTS family members, we examined the influence of Hb by synovial cells in an in vitro experimental system.

Methods

Synovial tissues were obtained from five young patients with meniscal injury under arthroscopic surgery. Primary cultures of human knee synovial cells were treated with different doses of human Hb (0, 25, 50, 100 μg/ml). The culture media were collected 24 h after Hb-treatment. In the time-course studies, cells were treated with and without 100 μg/ml Hb, and culture media were taken at 6, 12, and 24 h. To identify the proteins responsible for aggrecanase activity, Western blot analysis using antibodies against human ADAMTS-5, −8, −9, and −10; enzyme-linked immunosorbent assay (ELISA); and gene expression for ADAMTS-5 and -9 were examined. Statistical comparisons between each group were performed using paired t-tests.

Results

Western blot analysis revealed that Hb-treatment resulted in the expression of ADAMTS-5 and -9. Neither control group nor Hb-treated medium showed immunoreactivity against ADAMTS-8 or −10. In a dose-dependency study, the Hb-treated group showed significantly higher levels of ADAMTS-5 and -9 compared with the control (p < 0.05). There was no significant difference between 25, 50, and 100 μg/ml Hb-treated groups. In a time-course study, the ADAMTS-5 and -9 levels in the conditioned medium had significantly increased expression at 6, 12, and 24 h in the Hb-treated group (p < 0.05). Hb evoked significant expression of ADAMTS-9 mRNA at 12 and 24 h (p < 0.05).

Conclusions

These findings indicate that Hb induces the expression of ADAMTS-5 and -9 by synovial cells at low doses, even at an acute phase, and suggests a possible role for Hb in cartilage damage after intra-articular hemorrhage. The results also suggest a new potential therapeutic target by inhibiting the activities of ADAMTS-5 and -9 to prevent cartilage damage after intra-articular hemorrhage.

Therapeutic Effects of Olive and Its Derivatives on Osteoarthritis: From Bench to Bedside

Osteoarthritis is a major cause of morbidity among the elderly worldwide. It is a disease characterized by localized inflammation of the joint and destruction of cartilage, leading to loss of function. Impaired chondrocyte repair mechanisms, due to inflammation, oxidative stress and autophagy, play important roles in the pathogenesis of osteoarthritis. Olive and its derivatives, which possess anti-inflammatory, antioxidant and autophagy-enhancing activities, are suitable candidates for therapeutic interventions for osteoarthritis. This review aimed to summarize the current evidence on the effects of olive and its derivatives, on osteoarthritis and chondrocytes. The literature on animal and human studies has demonstrated a beneficial effect of olive and its derivatives on the progression of osteoarthritis. In vitro studies have suggested that the augmentation of autophagy (though sirtuin-1) and suppression of inflammation by olive polyphenols could contribute to the chondroprotective effects of olive polyphenols. More research and well-planned clinical trials are required to justify the use of olive-based treatment in osteoarthritis.

Chondrocyte secretome: a source of novel insights and exploratory biomarkers of osteoarthritis

The extracellular matrix (ECM) of articular cartilage is comprised of complex networks of proteins and glycoproteins, all of which are expressed by its resident cell, the chondrocyte. Cartilage is a unique tissue given its complexity and ability to resist repeated load and deformation. The mechanisms by which articular cartilage maintains its integrity throughout our lifetime is not fully understood, however there are numerous regulatory pathways known to govern ECM turnover in response to mechanical stimuli. To further our understanding of this field, we envision that proteomic analysis of the secretome will provide information on how the chondrocyte remodels the surrounding ECM in response to load, in addition to providing information on the metabolic state of the cell. In this review, we attempt to summarize the recent mass spectrometry-based proteomic discoveries in healthy and diseased cartilage and chondrocytes, to facilitate the discovery of novel biomarkers linked to degenerative pathologies, such as osteoarthritis (OA).

Coculture of bovine cartilage with synovium and fibrous joint capsule increases aggrecanase and matrix metalloproteinase activity

Background

A hallmark of osteoarthritis is increased proteolytic cleavage of aggrecan. Cross talk between cartilage and the synovium + joint capsule (SJC) can drive cartilage degradation by activating proteases in both tissues. We investigated aggrecan proteolysis patterns in cartilage explants using a physiologically relevant explant model of joint injury combining cartilage mechanical compression and coincubation with SJC.

Methods

Bovine cartilage explants were untreated; coincubated with SJC; or subjected to mechanical injury and coincubated with SJC, mechanical injury alone, or mechanical injury and incubated with tumor necrosis factor-α (TNF-α). To compare the patterns of aggrecan proteolysis between 6 h and 16 days, release of sulfated glycosaminoglycans and specific proteolytic aggrecan fragments into medium or remaining in cartilage explants was measured by dimethylmethylene blue and Western blot analysis.

Results

Aggrecanase activity toward aggrecan was observed in all conditions, but it was directed toward the TEGE↓ARGS interglobular domain (IGD) site only when cartilage was coincubated with SJC or TNF-α. Matrix metalloproteinase (MMP) activity at the aggrecan IGD site (IPES↓FFGV) was not detected when cartilage was exposed to TNF-α (up to 6 days), but it was in all other conditions. Compared with when bovine cartilage was left untreated or subjected to mechanical injury alone, additional aggrecan fragment types were released into medium and proteolysis of aggrecan started at an earlier time when SJC was present.

Conclusions

Indicative of different proteolytic pathways for aggrecan degradation, the SJC increases both aggrecanase and MMP activity toward aggrecan, whereas TNF-α inhibits MMP activity against the IGD of aggrecan.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1318-9) contains supplementary material, which is available to authorized users.

Matrix Metalloproteinases and Synovial Joint Pathology

Matrix metalloproteinases (MMPs) are zinc-dependent enzymes. These enzymes play a critical role in the destruction of articular cartilage in rheumatoid arthritis (RA), osteoarthritis (OA), psoriatic arthritis (PsA), and the spondyloarthropathies. MMP gene expression is upregulated in these synovial joint pathologies in response to elevated levels of proinflammatory cytokines and soluble mediators such as tumor necrosis factor-α, interleukin-1 (IL-1), IL-6, IL-17, and interferon-γ. These molecules are capable of activating the mitogen-activated protein kinase and Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways by binding the cytokine to their respective receptors on immune cells, macrophages, chondrocytes, synoviocytes, and osteocytes leading to increased synthesis of MMPs. Biologic drugs and/or small-molecule inhibitors designed to block cytokine to cytokine receptor interactions or to selectively inhibit JAKs have clinical efficacy in RA, PsA, and ankylosing spondylitis which correlated with a reduction in MMPs. Although there are currently no OA-selective drugs, it is likely that such a drug would have to reduce MMP gene expression to have clinical efficacy.

Effect of Choline on the Composition and Degradation Enzyme of Extracellular Matrix of Mice Chondrocytes Exposed to Fluoride

Choline has been shown to mediate damage of the chondrocyte matrix and degradation enzymes of mice exposed to fluoride (F). To test the action of choline, pregnant mice were treated with differing amounts of F and choline. Newborn mice were weaned at 21 days after birth and treated with the same doses of F and choline as they mothers for 12 weeks. Using hematoxylin-eosin (HE) staining, real-time PCR (RT-PCR), and western blotting, changes in the structure of the cartilage, the expression of mRNA and protein related to proteoglycans (PG), and degradation enzymes were detected. The RT-PCR results show that the expression of the Aggrecan (Acan), transforming growth factor beta (TGF-β1), and Aggrecanases-1 gene were abnormal in the high fluoride (HiF) group, and treatments with choline reversed this phenomenon. The western blotting results show that the protein expression of Aggrecanases-1 was significantly increased in the HiF group (p < 0.01). These findings suggest that F can change the morphology of cartilage tissue, the gene expression of the Acan, TGF-β1, Aggrecanases-1, and the protein expression of the Acan, and that choline can attenuate the effect of F. This may provide the basis for the treatment and prevention of fluorosis.

A Role for Soluble IL-6 Receptor in Osteoarthritis

Interleukin-6 (IL-6) is one of several pro-inflammatory cytokines present at elevated levels in the synovial fluid of individuals with confirmed clinical diagnosis of rheumatoid arthritis (RA) and osteoarthritis (OA). The mechanism of action of IL-6 was shown to involve its capacity to interact with a membrane-bound IL-6 receptor (mIL-6Rα), also known as the "classical" IL-6 pathway, or through its interaction with a soluble IL-6 receptor (sIL-6R) termed the "trans-signaling" pathway. Activation of downstream signaling is transduced via these IL-6 receptors and principally involves the Janus Kinase/Signal Transduction and Activators of Transcription (JAK/STAT) signaling pathway that is further regulated by glycoprotein-130 (gp130) interacting with the IL-6/mIL-6R complex. Phosphorylation of STAT proteins via JAK activation facilitates STAT proteins to act as transcription factors in inflammation. However, the biological function(s) of the sIL-6R in human chondrocytes requires further elucidation, although we previously showed that exogenous sIL-6R significantly suppressed the synthesis of neutrophil gelatinase-associated lipocalin (NGAL) in the immortalized line of human chondrocytes, C28/I2. NGAL was shown to regulate the activity of matrix metalloproteinase-9 (MMP-9), whose activity is crucial in OA for the destruction of articular cartilage. The "shedding" of sIL-6R from the plasma membrane is carried out by a family of enzymes known as A Distintegrin and Metalloproteinase (ADAM), which are also elevated in OA. In this paper, we have systematically reviewed the role played by IL-6 in OA. We have proposed that sIL-6R may be an important target for future drug development in OA by ameliorating cartilage extracellular protein degradation.

DNA Methylation in Osteoarthritis

Osteoarthritis (OA) is a prevalent disease of articular joints and primarily characterized by degradation and calcification of articular cartilage. Presently, no effective treatment other than pain relief exists and patients ultimately need to undergo replacement surgery of the affected joint. During disease progression articular chondrocytes, the single cell type present in articular cartilage, show altered transcriptional profiles and undergo phenotypic changes that resemble the terminal differentiation route apparent in growth plate chondrocytes. Hence, given its prominent function in both regulating gene expression and maintaining cellular phenotypes, DNA methylation of CpG dinucleotides is intensively studied in the context of OA. An increasing number of studies have been published that employed a targeted approach on genes known to play a role in OA pathophysiology. As of such, it has become clear that OA responsive DNA methylation changes seem to mediate disease associated aberrant gene expression. Furthermore, established OA susceptibility alleles such as GDF5 and DIO2 appear to confer OA risk via DNA methylation and respective pathophysiological expression changes. In more recent years, genome wide profiling of DNA methylation in OA affected articular cartilage has emerged as a powerful tool to address the epigenetic changes in their entirety, which has resulted in the identification of putative patient subgroups as well as generic OA associated pathways.

Biomimetic molecules lower catabolic expression and prevent chondroitin sulfate degradation in an osteoarthritic ex vivo model

Aggrecan, the major proteoglycan in cartilage, serves to protect cartilage tissue from damage and degradation during the progression of osteoarthritis (OA). In cartilage extracellular matrix (ECM) aggrecan exists in an aggregate composed of several aggrecan molecules that bind to a single filament of hyaluronan. Each molecule of aggrecan is composed of a protein core and glycosaminoglycan sides chains, the latter of which provides cartilage with the ability to retain water and resist compressive loads. During the progression of OA, loss of aggrecan is considered to occur first, after which other cartilage matrix components become extremely susceptible to degradation. Proteolytic cleavage of the protein core of aggrecan by enzymes such as aggrecanases, prevent its binding to HA and lower cartilage mechanical strength. Here we present the use of HA-binding or collagen type II-binding molecules that functionally mimic aggrecan but lack known cleavage sites, protecting the molecule from proteolytic degradation. These molecules synthesized with chondroitin sulfate backbones conjugated to hyaluronan- or collagen type II- binding peptides, are capable of diffusing through a cartilage explant and adhering to the ECM of this tissue. The objective of this study was to test the functional efficacy of these molecules in an ex vivo osteoarthritic model to discern the optimal molecule for further studies. Different variations of chondroitin sulfate conjugated to the binding peptides were diffused through aggrecan depleted explants and assessed for their ability to enhance compressive stiffness, prevent CS degradation, and modulate catabolic (MMP-13 and ADAMTS-5) and anabolic (aggrecan and collagen type II) gene expression. A pilot in vivo study assessed the ability to retain the molecule within the joint space of an osteoarthritic guinea pig model. The results indicate chondroitin sulfate conjugated to hyaluronan-binding peptides is able to significantly restore equilibrium modulus and prevent CS degradation. All molecules demonstrated the ability to lower catabolic gene expression in aggrecan depleted explants. In order to enhance biosynthesis and regeneration, the molecules need to be coupled with an external stimulant such as a growth factor. The chondroitin sulfate molecule synthesized with HA-binding peptides demonstrated adherence to cartilage tissue and retention up to 6 hours in an ambulatory joint. Further studies will monitor the in vivo residence time and ability of the molecules to act as a disease-modifying agent.

A Disintegrin and Metalloproteinase with Thrombospondin Motifs-5 (ADAMTS-5) Forms Catalytically Active Oligomers

The metalloproteinase ADAMTS-5 (A disintegrin and metalloproteinase with thrombospondin motifs) degrades aggrecan, a proteoglycan essential for cartilage structure and function. ADAMTS-5 is the major aggrecanase in mouse cartilage, and is also likely to be the major aggrecanase in humans. ADAMTS-5 is a multidomain enzyme, but the function of the C-terminal ancillary domains is poorly understood. We show that mutant ADAMTS-5 lacking the catalytic domain, but with a full suite of ancillary domains inhibits wild type ADAMTS activity, in vitro and in vivo, in a dominant-negative manner. The data suggest that mutant ADAMTS-5 binds to wild type ADAMTS-5; thus we tested the hypothesis that ADAMTS-5 associates to form oligomers. Co-elution, competition, and in situ PLA experiments using full-length and truncated recombinant ADAMTS-5 confirmed that ADAMTS-5 molecules interact, and showed that the catalytic and disintegrin-like domains support these intermolecular interactions. Cross-linking experiments revealed that recombinant ADAMTS-5 formed large, reduction-sensitive oligomers with a nominal molecular mass of ∼ 400 kDa. The oligomers were unimolecular and proteolytically active. ADAMTS-5 truncates comprising the disintegrin and/or catalytic domains were able to competitively block full-length ADAMTS-5-mediated aggrecan cleavage, measured by production of the G1-EGE(373) neoepitope. These results show that ADAMTS-5 oligomerization is required for full aggrecanase activity, and they provide evidence that blocking oligomerization inhibits ADAMTS-5 activity. The data identify the surface provided by the catalytic and disintegrin-like domains of ADAMTS-5 as a legitimate target for the design of aggrecanase inhibitors.

Relationship between synovial fluid ARGS-aggrecan fragments, cytokines, MMPs, and TIMPs following acute ACL injury: A cross-sectional study

Severe knee trauma, such as an ACL disruption, produces aggrecan degradation as evidenced by elevated synovial fluid (SF) N-terminal (393) Alanine-Arginine-Glycine-Serine (ARGS) neoepitope (or ARGS-aggrecan) and is associated with inflammatory activity soon after injury. However, it is not known if this process persists for a substantial time interval following the initial trauma. The purpose of this study was to evaluate relationships between SF ARGS concentrations and an array of cytokines, matrix metalloproteases (MMPs), and tissue inhibitor of metalloproteases (TIMPs) during the initial 6 months following ACL rupture. SF samples from 67 ACL-injured subjects (29 women) were analyzed within 6 months of injury (18-155 days), immediately prior to surgical ACL reconstruction. Relationships between ARGS and individual analyte concentrations, as well as MMP/TIMP ratios were evaluated. Statistically significant relationships were found between ARGS and basic fibroblast growth factor (FGF2) (p=0.03) and TIMP-3 (p=0.01). Our findings suggest that FGF2, considered to be primarily catabolic in articular cartilage, is not downregulated as ARGS concentration declines over time since injury. In addition, these results support the hypothesis that an upregulation of TIMP-3, the primary aggrecanase inhibitor, is elicited in response to increased aggrecan degradation, which may inhibit further cleavage.

Multiscale Biofabrication of Articular Cartilage: Bioinspired and Biomimetic Approaches

Articular cartilage is the load-bearing tissue found inside all articulating joints of the body. It vastly reduces friction and allows for smooth gliding between contacting surfaces. The structure of articular cartilage matrix and cellular composition is zonal and is important for its mechanical properties. When cartilage becomes injured through trauma or disease, it has poor intrinsic healing capabilities. The spectrum of cartilage injury ranges from isolated areas of the joint to diffuse breakdown and the clinical appearance of osteoarthritis. Current clinical treatment options remain limited in their ability to restore cartilage to its normal functional state. This review focuses on the evolution of biomaterial scaffolds that have been used for functional cartilage tissue engineering. In particular, we highlight recent developments in multiscale biofabrication approaches attempting to recapitulate the complex 3D matrix of native articular cartilage tissue. Additionally, we focus on the application of these methods to engineering each zone of cartilage and engineering full-thickness osteochondral tissues for improved clinical implantation. These methods have shown the potential to control individual cell-to-scaffold interactions and drive progenitor cell differentiation into a chondrocyte lineage. The use of these bioinspired nanoengineered scaffolds hold promise for recreation of structure and function on the whole tissue level and may represent exciting new developments for future clinical applications for cartilage injury and restoration.

Investigational drugs for the treatment of osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a common joint disease with multiple pathophysiological processes, affecting the whole joint. Current therapeutic options such as NSAIDs can provide a palliative effect on symptoms but have limited effect on disease progression. New drugs targeting OA structures may retard disease progression at an earlier stage and delay the need for joint replacement.

AREAS COVERED

Some drugs have entered into clinical trials and a few, such as strontium ranelate, do have improvements in both pain and structure changes. However, most of them have failed in clinical trials largely due to increased side effects or the failure to identify the right OA phenotype for the right drug in clinical design. This review describes various investigational drugs developed for the treatment of OA covering those at stages from preclinical experiments to early phase clinical trials. They include drugs for slowing cartilage degradation, regulating cartilage metabolism, targeting subchondral bone, controlling inflammation and relieving pain.

EXPERT OPINION

Treatment options for OA remain limited. However, with the emergence of sensitive tools to detect early disease progression and identification of different OA phenotypes, disease-modifying anti-OA drugs with increased benefit and reduced risks will become available for OA treatment in the near future.

Intraarticular Matrix Metalloproteinases and Aggrecan Degradation Are Elevated After Articular Fracture

BACKGROUND

Posttraumatic osteoarthritis (OA) is a variant of OA that can develop after articular injury. Although the mechanism(s) of posttraumatic OA are uncertain, the presence and impact of postinjury proteolytic enzymes on articular cartilage remain unknown. To our knowledge, there are no studies that evaluate the presence of matrix metalloproteinases (MMPs) or aggrecan degradation after articular fracture.

QUESTIONS/PURPOSES

(1) Are MMP concentrations and aggrecan degradation elevated after intraarticular fracture? (2) Are MMP concentrations and aggrecan degradation greater in high-energy injuries compared with low-energy injuries? (3) Do the concentrations of these biomarkers remain elevated at a secondary aspiration?

METHODS

Between December 2011 and June 2013, we prospectively enrolled patients older than 18 years of age with acute tibial plateau fracture. Exclusion criteria included age older than 60 years, preexisting knee OA, injury greater than 24 hours before evaluation, contralateral knee injury, history of autoimmune disease, open fracture, and non-English-speaking patients. During the enrollment period, we enrolled 45 of the 91 (49%) tibial plateau fractures treated at our facility. Knee synovial fluid aspirations were obtained from both the injured and uninjured knees; two patients received aspirations in the emergency department and the remaining patients received aspirations in the operating room. Twenty patients who underwent spanning external fixator followed by definitive fixation were aspirated during both surgical procedures. MMP-1, -2, -3, -7, -9, -10, -12, and -13 concentrations were quantified using multiplex assays. Aggrecan degradation was quantified using sandwich enzyme-linked immunosorbent assay.

RESULTS

There were higher concentrations of MMP-1 (3.89 ng/mL [95% confidence interval {CI}, 2.37-6.37] versus 0.37 ng/mL [95% CI, 0.23-0.61], p < 0.001), MMP-3 (457.35 ng/mL [95% CI, 274.5-762.01] versus 129.17 ng/mL [95% CI, 77.01-216.66], p < 0.001), MMP-9 (6.52 ng/mL [95% CI, 3.86-11.03] versus 0.96 ng/mL [95% CI, 0.56-1.64], p < 0.001), MMP-10 (0.52 ng/mL [95% CI, 0.40-0.69] versus 0.23 ng/mL [95% CI, 0.17-0.30], p < 0.001), and MMP-12 (0.18 ng/mL [95% CI, 0.14-0.23] versus 0.10 ng/mL [95% CI, 0.0.081-0.14], p = 0.005) in injured knees compared with uninjured knees. There was not a detectable difference in MMP concentrations or aggrecan degradation between high- and low-energy injuries. MMP-1 (53.25 versus 3.89 ng/mL, p < 0.001), MMP-2 (76.04 versus 0.37 ng/mL, p < 0.001), MMP-3 (1250.62 versus 457.35 ng/mL, p = 0.002), MMP-12 (1.37 versus 0.18, p < 0.001), MMP-13 (0.98 versus 0.032 ng/mL, p < 0.001), and aggrecan degradation (0.58 versus 0.053, p < 0.001) were increased at the second procedure (mean, 9.5 days; range, 3-21 days) as compared with the initial procedure.

CONCLUSIONS

Because MMPs and aggrecan degradation are elevated after articular fracture, future studies are necessary to evaluate the impact of elevated MMPs and aggrecan degradation on human articular cartilage.

CLINICAL RELEVANCE

If further clinical followup can demonstrate a relationship between posttraumatic OA and elevated MMPs and aggrecan degradation, they may provide potential for therapeutic targets to prevent or delay the destruction of the joint. Additionally, these markers may offer prognostic information for patients.

Translational development of an ADAMTS-5 antibody for osteoarthritis disease modification

OBJECTIVE/METHOD

Aggrecanase activity, most notably ADAMTS-5, is implicated in pathogenic cartilage degradation. Selective monoclonal antibodies (mAbs) to both ADAMTS-5 and ADAMTS-4 were generated and in vitro, ex vivo and in vivo systems were utilized to assess target engagement, aggrecanase inhibition and modulation of disease-related endpoints with the intent of selecting a candidate for clinical development in osteoarthritis (OA).

RESULTS

Structural mapping predicts the most potent mAbs employ a unique mode of inhibition by cross-linking the catalytic and disintegrin domains. In a surgical mouse model of OA, both ADAMTS-5 and ADAMTS-4-specific mAbs penetrate cartilage following systemic administration, demonstrating access to the anticipated site of action. Structural disease modification and associated alleviation of pain-related behavior were observed with ADAMTS-5 mAb treatment. Treatment of human OA cartilage demonstrated a preferential role for ADAMTS-5 inhibition over ADAMTS-4, as measured by ARGS neoepitope release in explant cultures. ADAMTS-5 mAb activity was most evident in a subset of patient-derived tissues and suppression of ARGS neoepitope release was sustained for weeks after a single treatment in human explants and in cynomolgus monkeys, consistent with high affinity target engagement and slow ADAMTS-5 turnover.

CONCLUSION

This data supports a hypothesis set forth from knockout mouse studies that ADAMTS-5 is the major aggrecanase involved in cartilage degradation and provides a link between a biological pathway and pharmacology which translates to human tissues, non-human primate models and points to a target OA patient population. Therefore, a humanized ADAMTS-5-selective monoclonal antibody (GSK2394002) was progressed as a potential OA disease modifying therapeutic.

Inflammatory cytokines and biomarkers of cartilage metabolism 8 years after anterior cruciate ligament reconstruction: results from operated and contralateral knees

BACKGROUND

Patients who sustain an acute anterior cruciate ligament (ACL) rupture are at increased risk to develop posttraumatic arthritis (PTA) in the injured knee whether the ACL is reconstructed or treated nonoperatively. Inflammatory cytokines and cartilage degradation biomarkers are elevated at the time of acute injury and postoperatively. This suggests that one mechanism for PTA may be an inflammatory degradative process initiated on the acute injury and sustained for some length of time independent of whether adequate joint stability is restored.

HYPOTHESIS

Inflammatory cytokines and biomarkers of cartilage degradation are elevated in the synovial fluid several years after reconstruction of the ACL, indicating an ongoing imbalance between extracellular matrix destruction and repair.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In 11 patients who had undergone ACL reconstruction 8 years earlier, knee synovial fluid was aspirated from the operated knee and the contralateral nonoperated knee. The synovial fluid was analyzed for interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, sulfated glycosaminoglycans (sGAG), aggrecan neoepitope fragment (ARGS-aggrecan), and cartilage oligomeric matrix protein (COMP). At follow-up, the patients underwent bilateral weightbearing radiographs and bilateral MRIs of their knees.

RESULTS

No significant differences between the operated and the contralateral knee were found for the synovial fluid concentrations of IL-1β, IL-6, TNF-α, sGAG, ARGS-aggrecan, or COMP. There were significantly more radiographically visible osteoarthritic changes in the operated knees compared with the contralateral knees. MRIs revealed that all grafts and all contralateral ACLs were intact and, furthermore, that there was significantly more meniscal and cartilage damage in the index knees than the contralateral knees.

CONCLUSION

Eight years after ACL reconstruction, there were no significant differences in inflammatory cytokines and biomarkers for cartilage degeneration between the nonoperated and the ACL-reconstructed knee, even though there were more osteoarthritic changes and meniscal and cartilage damage in the operated knee, as seen on weightbearing radiographs and MRI.

Effects of low molecular weight hyaluronan combined with carprofen on canine osteoarthritis articular chondrocytes and cartilage explants in vitro

Intra-articular injection with non-steroidal anti-inflammatory drugs (NSAIDs) is used to treat inflammatory joint disease, but the side effects of NSAIDs include chondrotoxicity. Hyaluronan has shown positive effects on chondrocytes by reducing apoptosis and increasing proteoglycan synthesis. The purposes of this study were to evaluate the effects of low molecular weight hyaluronan (low MW HA), carprofen 25 mg/ml, carprofen 12.5 mg/ml, and a combination of HA and carprofen on canine osteoarthritis (OA) articular chondrocytes and a cartilage explant model in terms of cell viability, extracellular matrix remaining, and gene expression after exposure. In chondrocyte culture, MTT assay was used to evaluate the chondrotoxicity of IC50 and IC80 of carprofen with HA. In cartilage explant culture, two kinds of extracellular matrix (uronic acid and collagen) remaining in cartilage were used to evaluate cartilage damage for 14 d after treatment. Expression of COL2A1, AGG, and MMP3 was used to evaluate the synthesis and degradation of the matrix for 7 d after treatment. In chondrocyte culture, low MW HA could preserve OA chondrocyte viability but could not reduce the chondrotoxicity level of carprofen (P < 0.05). In explant culture, low MW HA combined with 12.5 mg/ml carprofen caused less destruction of uronic acid and collagen structure when compared with the control (P < 0.05). Low MW HA caused high expression levels of COL2A1 and AGG in OA cartilage (P < 0.05); HA combined with carprofen resulted in higher COL2A1 and AGG expression levels than carprofen alone.