Metalloprotease activity, phospholipase A2 activity and cytokine concentration in osteoarthritis synovial fluids

Recent Progress in Cartilage Lubrication

Healthy articular cartilage, covering the ends of bones in major joints such as hips and knees, presents the most efficiently-lubricated surface known in nature, with friction coefficients as low as 0.001 up to physiologically high pressures. Such low friction is indeed essential for its well-being. It minimizes wear-and-tear and hence the cartilage degradation associated with osteoarthritis, the most common joint disease, and, by reducing shear stress on the mechanotransductive, cartilage-embedded chondrocytes (the only cell type in the cartilage), it regulates their function to maintain homeostasis. Understanding the origins of such low friction of the articular cartilage, therefore, is of major importance in order to alleviate disease symptoms, and slow or even reverse its breakdown. This progress report considers the relation between frictional behavior and the cellular mechanical environment in the cartilage, then reviews the mechanism of lubrication in the joints, in particular focusing on boundary lubrication. Following recent advances based on hydration lubrication, a proposed synergy between different molecular components of the synovial joints, acting together in enabling the low friction, has been proposed. Additionally, recent development of natural and bio-inspired lubricants is reviewed.

Characterization of Early-Onset Finger Osteoarthritis-Like Condition Using Patient-Derived Induced Pluripotent Stem Cells

Early osteoarthritis (OA)-like symptoms are difficult to study owing to the lack of disease samples and animal models. In this study, we generated induced pluripotent stem cell (iPSC) lines from a patient with a radiographic early-onset finger osteoarthritis (efOA)-like condition in the distal interphalangeal joint and her healthy sibling. We differentiated those cells with similar genetic backgrounds into chondrogenic pellets (CPs) to confirm efOA. CPs generated from efOA-hiPSCs (efOA-CPs) showed lower levels of COL2A1, which is a key marker of hyaline cartilage after complete differentiation, for 21 days. Increase in pellet size and vacuole-like morphologies within the pellets were observed in the efOA-CPs. To analyze the changes occurred during the development of vacuole-like morphology and the increase in pellet size in efOA-CPs, we analyzed the expression of OA-related markers on day 7 of differentiation and showed an increase in the levels of COL1A1, RUNX2, VEGFA, and AQP1 in efOA-CPs. IL-6, MMP1, and MMP10 levels were also increased in the efOA-CPs. Taken together, we present proof-of-concept regarding disease modeling of a unique patient who showed OA-like symptoms.

Can low-dose methotrexate reduce effusion-synovitis and symptoms in patients with mid- to late-stage knee osteoarthritis? Study protocol for a randomised, double-blind, and placebo-controlled trial

BACKGROUND

Osteoarthritis (OA) is a common chronic disease in older adults. Currently, there are no effective therapies to reduce disease severity and progression of knee OA (KOA), particularly in mid- to late-stages. This study aims to examine the effect of methotrexate (MTX) on knee effusion-synovitis and pain in symptomatic patients with mid- to late-stage KOA.

METHODS/DESIGN

This protocol describes a multicentre randomised placebo-controlled clinical trial aiming to recruit 200 participants with mid- to late-stage symptomatic KOA and with effusion-synovitis grade of ≥ 2. Participants will be randomly allocated to the MTX group (start from 5 mg per week for the first 2 weeks and increase to 10 mg per week for the second 2 weeks and 15 mg per week for the remaining period if tolerated) or the placebo group. Primary outcomes are effusion-synovitis size measured by magnetic resonance imaging (MRI) and knee pain assessed by visual analogue scale (VAS). Secondary outcomes are signal intensity alteration within infrapatellar fat pad (IPFP) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score and subscores, and the Outcome Measures in Rheumatology Arthritis Clinical Trials-Osteoarthritis Research Society International (OMERACT-OARSI) responders. Both intention-to-treat and per-protocol analyses will be performed.

DISCUSSION

If MTX intervention can relieve symptoms and reduce inflammation in patients with mid- to late-stage KOA, it has the potential for significant clinical and public health impact as this low-cost and commonly used intervention would delay the time to knee replacement, leading to substantial cost savings and improve quality of life.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03815448 . Registered on 21 January 2019.

Lubrication of Articular Cartilage

The major synovial joints such as hips and knees are uniquely efficient tribological systems, able to articulate over a wide range of shear rates with a friction coefficient between the sliding cartilage surfaces as low as 0.001 up to pressures of more than 100 atm. No human-made material can match this. The means by which such surfaces maintain their very low friction has been intensively studied for decades and has been attributed to fluid-film and boundary lubrication. Here, we focus especially on the latter: the reduction of friction by molecular layers at the sliding cartilage surfaces. In particular, we discuss such lubrication in the light of very recent advances in our understanding of boundary effects in aqueous media based on the paradigms of hydration lubrication and of the synergism between different molecular components of the synovial joints (namely hyaluronan, lubricin, and phospholipids) in enabling this lubrication.

Lysophosphatidylcholines to phosphatidylcholines ratio predicts advanced knee osteoarthritis

OBJECTIVE

To identify novel biomarker(s) for predicting advanced knee OA.

METHODS

Study participants were derived from the Newfoundland Osteoarthritis Study and the Tasmania Older Adult Cohort Study. All knee OA cases were patients who underwent total knee replacement (TKR) due to primary OA. Metabolic profiling was performed on fasting plasma. Four thousand and eighteen plasma metabolite ratios that were highly correlated with that in SF in our previous study were generated as surrogates for joint metabolism.

RESULTS

The discovery cohort included 64 TKR cases and 45 controls and the replication cohorts included a cross-sectional cohort of 72 TKR cases and 76 controls and a longitudinal cohort of 158 subjects, of whom 36 underwent TKR during the 10-year follow-up period. We confirmed the previously reported association of the branched chain amino acids to histidine ratio with advanced knee OA (P = 9.3 × 10(-7)) and identified a novel metabolic marker-the lysophosphatidylcholines (lysoPCs) to phosphatidylcholines (PCs) ratio-that was associated with advanced knee OA (P = 1.5 × 10(-7)) after adjustment for age, sex and BMI. When the subjects of the longitudinal cohort were categorized into two groups based on the optimal cut-off of the ratio of 0.09, we found the subjects with the ratio ⩾0.09 were 2.3 times more likely to undergo TKR than those with the ratio <0.09 during the 10-year follow-up (95% CI: 1.2, 4.3, P = 0.02).

CONCLUSION

We identified the ratio of lysoPCs to PCs as a novel metabolic marker for predicting advanced knee OA. Further studies are required to examine whether this ratio can predict early OA change.

Expression of the calcium-sensing receptor in monocytes from synovial fluid is increased in osteoarthritis

OBJECTIVES

We assessed calcium-sensing receptor (CaSR) expression in monocytes isolated from synovial fluid of patients with different types of rheumatisms and explored whether CaSR expression was related to the inflammatory nature of synovial fluid.

METHODS

Forty-one patients were included: osteoarthritis (n=10), microcristallin rheumatisms (n=10), rheumatoid arthritis (n=12) and other inflammatory rheumatisms (n=9). Surface and total CaSR expressions in monocytes isolated from synovial fluid and blood were assessed by flow cytometry analysis. U937 cells were cultured during 24hours in presence of cell-free synovial fluids.

RESULTS

Every monocyte population tested express the CaSR intra- and extracellularly. Whereas similar pattern of CaSR expression exist in monocyte isolated from blood or synovial fluids, our results indicate that higher CaSR expression levels can be observed in monocytes from synovial fluids than in circulating monocytes. In both populations of monocytes, surface and total CaSR expressions were found to be significantly increased in patients with osteoarthritis compared to rheumatoid arthritis. Similar data were obtained when U937 cells were incubated with cell-free synovial fluids from osteoarthritis patients. Still present, this effect was significantly lowered when "inflammatory" synovial fluids were introduced in culture.

CONCLUSIONS

Our results indicate that CaSR expression in synovial derived monocytes is higher in osteoarthritis than in inflammatory rheumatisms and that CaSR expression is modulated by the nature of the synovial fluid. Given the role played by monocytes in the pathogenesis of chronic rheumatisms, monocytes could be interesting therapeutic targets via the CaSR.

Comparison of molecular mechanisms of rheumatoid arthritis and osteoarthritis using gene microarrays

The present study aimed to compare the molecular mechanisms of rheumatoid arthritis (RA) and osteoarthritis (OA). The microarray dataset no. GSE29746 was downloaded from Gene Expression Omnibus. After data pre‑processing, differential expression analysis between the RA group and the control, as well as between the OA group and the control was performed using the LIMMA package in R and differentially expressed transcripts (DETs) with |log2fold change (FC)|>1 and P<0.01 were identified. DETs screened from each disease group were then subjected to functional annotation using DAVID. Next, DETs from each group were used to construct individual interaction networks using the BIND database, followed by sub‑network mining using clusterONE. Significant functions of nodes in each sub‑network were also investigated. In total, 19 and 281 DETs were screened from the RA and OA groups, respectively, with only six common DETs. DETs from the RA and OA groups were enriched in 8 and 130 gene ontology (GO) terms, respectively, with four common GO terms, of which to were associated with phospholipase C (PLC) activity. In addition, DETs screened from the OA group were enriched in immune response‑associated GO terms, and those screened from the RA group were largely associated with biological processes linked with the cell cycle and chromosomes. Genes involved in PLC activity and its regulation were indicated to be altered in RA as well as in OA. Alterations in the expression of cell cycle‑associated genes were indicated to be linked with the occurrence of OA, while genes participating in the immune response were involved in the occurrence of RA.

Buprenorphine does not impact the inflammatory response in haemophilia A mice with experimentally-induced haemarthrosis

Haemarthrosis is the most common clinical manifestation of haemophilia and is responsible for significant morbidity in haemophilic patients. The murine experimentally-induced knee bleeding model is an important model in haemophilia research but it is currently unknown if the use of analgesia in this model might impact on the inflammatory response. The aim was to investigate the inflammatory response after a needle induced knee bleed in haemophilia A mice treated with buprenorphine or saline. One hundred and sixty mice were randomized into two groups to blindly receive buprenorphine or saline. All the mice were anaesthetized and knee injury was induced by inserting a 30 G needle into the right knee joint. At t = 6, 24, 48 and 72 h, 20 mice from each group were terminated and the following parameters were assessed: change in body weight and joint diameter, visual bleeding score (VBS), white blood counts, haematocrit, platelet concentrations, haemoglobin, plasma haptoglobin and plasma and synovial fluid levels of 23 cytokines. Twenty mice were terminated at t = 0 receiving no injury or treatment to provide baseline measures. Twenty-one cytokines in plasma and 22 cytokines in synovial fluid, joint diameter change, VBS and blood parameters were not significantly altered by the administration of buprenorphine. Slight alterations of plasma haptoglobin at t = 48 h, body weight, plasma and synovial eotaxin and plasma G-CSF were found in buprenorphine-treated mice. We demonstrated that buprenorphine does not overall impact on the inflammatory response, and the use of buprenorphine in the knee bleeding model in haemophilic mice should be continued.

The effects of nonsteroidal anti-inflammatory drugs on clinical outcomes, synovial fluid cytokine concentration and signal transduction pathways in knee osteoarthritis. A randomized open label trial

OBJECTIVE

We investigated the effects of celecoxib, diclofenac, and ibuprofen on the disease-specific quality of life, synovial fluid cytokines and signal transduction pathways in symptomatic knee osteoarthritis (OA).

DESIGN

Ninety patients scheduled for a total knee arthroplasty (TKA) were randomized to six groups that were treated with low and high dosages of celecoxib, diclofenac or ibuprofen. At the time of the first admission (T0) and at surgery (T1 = 14 days after beginning of the nonsteroidal anti-inflammatory drugs (NSAIDs)), samples of knee synovial fluid were obtained from each patient for analysis. During the surgery the synovial tissue was harvested from the knee of patients. The Western Ontario and McMaster universities (WOMAC) score was used to evaluate the patient disease-specific quality of life at T0 and T1. Microarray tests performed at T0 and T1 were used to evaluate the effects of NSAIDs on Tumor necrosis factor (TNF)-alpha, Interleukin-6 (IL-6), IL8 and Vascular endothelial growth factor (VEGF) concentration in the synovial fluid. Western blot assays evaluated the effects of NSAIDs on MAP kinase (MAPK) signal transduction pathway in the synovial membrane.

RESULTS

NSAID treatment induced a statistically significant improvement in the WOMAC score and a statistically significant decrease in the IL-6, VEGF and TNF-alpha concentration in the synovial fluid. Higher dosages of NSAIDs provided a greater improvement in the disease-specific quality of life of patients and lower concentrations of pro-inflammatory cytokines in the synovial fluid. Inhibition of MAPKs was noted after NSAID treatment.

CONCLUSION

Short-term NSAID treatment improves the patient disease-specific quality of life with a parallel decrease in pro-inflammatory synovial fluid cytokine levels in knee OA. Signal transduction pathways may be involved in regulating the anti-inflammatory effects of NSAIDs. ClinicalTrial.gov: NCT01860833.

Biomimetic aggrecan reduces cartilage extracellular matrix from degradation and lowers catabolic activity in ex vivo and in vivo models

Aggrecan, a major macromolecule in cartilage, protects the extracellular matrix (ECM) from degradation during the progression of osteoarthritis (OA). However, aggrecan itself is also susceptible to proteolytic cleavage. Here, the use of a biomimetic proteoglycan (mAGC) is presented, which functionally mimics aggrecan but lacks the known cleavage sites, protecting the molecule from proteolytic degradation. The objective of this study is to test the efficacy of this molecule in ex vivo (human OA synovial fluid) and in vivo (Sprague-Dawley rats) osteoarthritic models. These results indicate that mAGC's may protect articular cartilage against the loss of key ECM components, and lower catabolic protein and gene expression in both models. This suppression of matrix degradation has the potential to provide a healthy environment for tissue repair.

Phospholipases of mineralization competent cells and matrix vesicles: roles in physiological and pathological mineralizations

The present review aims to systematically and critically analyze the current knowledge on phospholipases and their role in physiological and pathological mineralization undertaken by mineralization competent cells. Cellular lipid metabolism plays an important role in biological mineralization. The physiological mechanisms of mineralization are likely to take place in tissues other than in bones and teeth under specific pathological conditions. For instance, vascular calcification in arteries of patients with renal failure, diabetes mellitus or atherosclerosis recapitulates the mechanisms of bone formation. Osteoporosis—a bone resorbing disease—and rheumatoid arthritis originating from the inflammation in the synovium are also affected by cellular lipid metabolism. The focus is on the lipid metabolism due to the effects of dietary lipids on bone health. These and other phenomena indicate that phospholipases may participate in bone remodelling as evidenced by their expression in smooth muscle cells, in bone forming osteoblasts, chondrocytes and in bone resorbing osteoclasts. Among various enzymes involved, phospholipases A₁ or A₂, phospholipase C, phospholipase D, autotaxin and sphingomyelinase are engaged in membrane lipid remodelling during early stages of mineralization and cell maturation in mineralization-competent cells. Numerous experimental evidences suggested that phospholipases exert their action at various stages of mineralization by affecting intracellular signaling and cell differentiation. The lipid metabolites—such as arachidonic acid, lysophospholipids, and sphingosine-1-phosphate are involved in cell signaling and inflammation reactions. Phospholipases are also important members of the cellular machinery engaged in matrix vesicle (MV) biogenesis and exocytosis. They may favour mineral formation inside MVs, may catalyse MV membrane breakdown necessary for the release of mineral deposits into extracellular matrix (ECM), or participate in hydrolysis of ECM. The biological functions of phospholipases are discussed from the perspective of animal and cellular knockout models, as well as disease implications, development of potent inhibitors and therapeutic interventions.

Circulating levels of IL-6 and TNF-α are associated with knee radiographic osteoarthritis and knee cartilage loss in older adults

OBJECTIVE

The role of inflammation in osteoarthritis (OA) pathogenesis is unclear, and the associations between inflammatory cytokines and cartilage loss have not been reported. We determined the associations between serum levels of interleukin (IL)-6 and tumor necrosis factor-α (TNF-α), knee radiographic OA (ROA) and cartilage loss over 2.9 years in older adults.

METHODS

A total of 172 randomly selected subjects (mean 63 years, range 52-78, 47% female) were studied at baseline and approximately 3 (range 2.6-3.3) years later. IL-6 and TNF-α were assessed by radioimmunoassay. T1-weighted fat-suppressed magnetic resonance imaging of the right knee was performed at baseline and follow-up to determine knee cartilage volume. Knee ROA of both knees was assessed at baseline.

RESULTS

At baseline, quartiles of IL-6 and TNF-α were associated with increased prevalence of medial tibiofemoral joint space narrowing (OARSI grade ≥ 1) in multivariate analyses [odds ratio (OR): 1.42 and 1.47 per quartile, respectively, both P<0.05]. Longitudinally, baseline IL-6 predicted loss of both medial and lateral tibial cartilage volume (β: -1.19% and -1.35% per annum per quartile, P<0.05 and P<0.01, respectively), independently of TNF-α. Change in IL-6 was associated with increased loss of medial and lateral tibial cartilage volume (β: -1.18% and -1.06% per annum per quartile, both P<0.05) and change in TNF-α was also negatively associated with change in medial cartilage volume (β: -1.27% per annum per quartile, P<0.05).

CONCLUSIONS

Serum levels of IL-6 and TNF-α are associated with knee cartilage loss in older people suggesting low level inflammation plays a role in the pathogenesis of knee OA.

Cytokine profile of autologous conditioned serum for treatment of osteoarthritis, in vitro effects on cartilage metabolism and intra-articular levels after injection

INTRODUCTION

Intraarticular administration of autologous conditioned serum (ACS) recently demonstrated some clinical effectiveness in treatment of osteoarthritis (OA). The current study aims to evaluate the in vitro effects of ACS on cartilage proteoglycan (PG) metabolism, its composition and the effects on synovial fluid (SF) cytokine levels following intraarticular ACS administration.

METHODS

The effect of conditioned serum on PG metabolism of cultured OA cartilage explants was compared to unconditioned serum. The effect of serum conditioning on levels of interleukin-1beta (IL-1beta), IL-4, IL-6, IL-10, IL-13, interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), osteoprotegerin (OPG), oncostatin M (OSM), interleukin-1 receptor (IL-1ra) and transforming growth factor beta (TGF-beta) were measured by multiplex ELISA. As TNF-alpha levels were found to be increased in conditioned serum, the effect of TNF-alpha inhibition by etanercept on PG metabolism was studied in cartilage explants cultured in the presence of conditioned serum. Furthermore, cytokine levels in SF were measured three days after intraarticular ACS injection in OA patients to verify their retention time in the joint space.

RESULTS

PG metabolism was not different in the presence of conditioned serum compared to unconditioned serum. Levels of the anti-inflammatory cytokines IL-1ra, TGF-beta, IL-10 as well as of pro-inflammatory cytokines IL-1beta, IL-6, TNF-alpha and OSM were increased. IL-4, IL-13 and IFN-gamma levels remained similar, while OPG levels decreased. TNF-alpha inhibition did not influence PG metabolism in cartilage explant culture in the presence of conditioned serum. Although OPG levels were higher and TGF-beta levels were clearly lower in ACS than in SF, intraarticular ACS injection in OA patients did not result in significant changes in these cytokine levels.

CONCLUSIONS

ACS for treatment of osteoarthritis contains increased levels of anti-inflammatory as well as pro-inflammatory cytokines, in particular TNF-alpha, but conditioned serum does not seem to have a net direct effect on cartilage metabolism, even upon inhibition of TNF-alpha. The fast intraarticular clearance of cytokines in the injected ACS may explain the limited effects found previously in vivo.

The association between leptin, interleukin-6, and hip radiographic osteoarthritis in older people: a cross-sectional study

Introduction

The associations between leptin, interleukin (IL)-6, and hip radiographic osteoarthritis (OA) have not been reported, and their roles in obesity-related hip OA are unclear. The aim of this study was to describe the associations between leptin, IL-6, and hip radiographic osteoarthritis (ROA) in older adults.

Methods

A cross-sectional sample of 193 randomly selected subjects (mean age, 63 years; range, 52 to 78 years; 48% female subjects) were studied. Hip ROA, including joint-space narrowing (JSN) and osteophytes, was determined by anteroposterior radiograph. Serum levels of leptin and interleukin (IL)-6 were measured with radioimmunoassay. Fat mass was measured with dual-energy x-ray absorptiometry (DXA). Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated.

Results

In multivariable analysis, hip JSN was associated with serum levels of leptin in the whole sample (β = 0.046 per μg/L, P = 0.024 for superior; β = 0.068 per μg/L, P = 0.004 for axial compartment) and IL-6 only in females (β = 0.241 per pg/ml, P = 0.002 for superior; β = 0.239 per pg/ml, P = 0.001 for axial compartment). The positive associations between body-composition measures (BMI, WHR, percentage total fat mass, and percentage trunk fat mass) and hip JSN in women became nonsignificant after adjustment for leptin but not for IL-6. No significant associations were found between leptin, IL-6, and the presence or severity of osteophytes.

Conclusions

This study suggests that metabolic and inflammatory mechanisms may play a role in the etiology of hip OA and that the associations between body composition and hip JSN are mediated by leptin, particularly in women.

Tumor necrosis factor alpha and interleukin-1beta modulate calcium and nitric oxide signaling in mechanically stimulated osteocytes

OBJECTIVE

Inflammatory diseases often coincide with reduced bone mass. Mechanoresponsive osteocytes regulate bone mass by maintaining the balance between bone formation and resorption. Despite its biologic significance, the effect of inflammation on osteocyte mechanoresponsiveness is not understood. To fill this gap, we investigated whether the inflammatory cytokines tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta) modulate the osteocyte response to mechanical loading.

METHODS

MLO-Y4 osteocytes were incubated with TNFalpha (0.5-30 ng/ml) or IL-1beta (0.1-10 ng/ml) for 30 minutes or 24 hours, or with calcium inhibitors for 30 minutes. Cells were subjected to mechanical loading by pulsatile fluid flow (mean +/- amplitude 0.7 +/- 0.3 Pa, 5 Hz), and the response was quantified by measuring nitric oxide (NO) production using Griess reagent and by measuring intracellular calcium concentration ([Ca(2+)](i)) using Fluo-4/AM. Focal adhesions and filamentous actin (F-actin) were visualized by immunostaining, and apoptosis was quantified by measuring caspase 3/7 activity. Cell-generated tractions were quantified using traction force microscopy, and cytoskeletal stiffness was quantified using optical magnetic twisting cytometry.

RESULTS

Pulsatile fluid flow increased [Ca(2+)](i) within seconds (in 13% of cells) and NO production within 5 minutes (4.7-fold). TNFalpha and IL-1beta inhibited these responses. Calcium inhibitors decreased pulsatile fluid flow-induced NO production. TNFalpha and IL-1beta affected cytoskeletal stiffness, likely because 24 hours of incubation with TNFalpha and IL-1beta decreased the amount of F-actin. Incubation with IL-1beta for 24 hours stimulated osteocyte apoptosis.

CONCLUSION

Our results suggest that TNFalpha and IL-1beta inhibit mechanical loading-induced NO production by osteocytes via abrogation of pulsatile fluid flow-stimulated [Ca(2+)](i), and that IL-1beta stimulates osteocyte apoptosis. Since both NO and osteocyte apoptosis affect osteoclasts, these findings provide a mechanism by which inflammatory cytokines might contribute to bone loss and consequently affect bone mass in rheumatoid arthritis.

Intraarticular injection of anakinra in osteoarthritis of the knee: a multicenter, randomized, double-blind, placebo-controlled study

OBJECTIVE

To evaluate the clinical response, safety, and tolerability of a single intraarticular injection of anakinra in patients with symptomatic osteoarthritis (OA) of the knee.

METHODS

Patients with OA of the knee were enrolled in a multicenter, double-blind, placebo-controlled study and randomized 2:1:2 to receive a single intraarticular injection of placebo, anakinra 50 mg, or anakinra 150 mg in their symptomatic knee. Patients were evaluated for 12 weeks postinjection. The primary end point was the change in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score from baseline to week 4. Safety assessments included the evaluation of adverse events (AEs), laboratory tests, and vital signs. Pharmacokinetic parameters were assessed in a subset of patients.

RESULTS

Of 170 patients who enrolled, 160 (94%) completed the study. The mean improvements from baseline to week 4 in the WOMAC score were not statistically different between the placebo group and the patients who received 50 mg of anakinra (P = 0.67) or 150 mg of anakinra (P = 0.77). Anakinra was well tolerated. No withdrawals due to AEs or serious AEs, and no serious infections or deaths were reported. No clinically significant trends were noted in laboratory values or vital signs. Pharmacokinetic parameters demonstrated that the mean terminal half-life of anakinra in serum after intraarticular injection was approximately 4 hours.

CONCLUSION

Anakinra was well tolerated as a single 50-mg or 150-mg intraarticular injection in patients with OA of the knee. However, anakinra was not associated with improvements in OA symptoms compared with placebo.

Joint injury and osteoarthritis: soluble mediators in the course and treatment of cartilage pathology

Osteoarthritis is a disabling disease of the aging generation, which results in loss of quality of life and increased healthcare costs. Cytokines appear to play an important role in the cartilaginous degeneration characterizing the pathological process. Increasing experience is being gained with cytokine-modulating therapies aimed at interfering with effects of chondrodegradative cytokines in the synovial fluid. Although in vitro and in vivo effectiveness of several of these therapies has been demonstrated, clinical effectiveness remains disputable, which may be related to the low levels of inflammatory cytokines found in osteoarthritic joints. By contrast, directly after joint trauma, which has been shown to predipose to early osteoarthritis, synovial fluid cytokine levels are strongly increased. Cytokine-modulating therapies, however, have hardly been considered for this indication. Increased knowledge of intra-articular soluble mediators correlating with cartilage pathology will lead to further development of cytokine-modulating products and, eventually, to effective inhibition of cartilage degeneration, in both the osteoarthritic as well as injured joints.

Oral and Maxillofacial Pathology: Interleukin-1 β, interleukin-6, and tissue inhibitor of metalloproteinase-1 in the synovial fluid of the temporomandibular joint with respect to cartilage destruction

OBJECTIVE

The distribution and biological roles of interleukin (IL)-1 beta, IL-6, and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the synovial fluid of patients with non-inflammatory chronic temporomandibular joint (TMJ) disorders were evaluated in relation to pain upon joint movements and X-ray and magnetic resonance imaging (MRI) findings.

MATERIALS AND METHODS

TMJ aspirates were obtained from 48 patients (48 joints) with chronic TMJ disorders and from 18 controls (18 joints). The IL-1 beta and IL-6 levels in the aspirates were determined by using an enzyme-linked immunosorbent assay and the TIMP-1 level was measured by an enzyme immunoassay. Following examinations for pain upon joint movements and X-ray and MRI observations, the IL-1 beta, IL-6, and TIMP-1 levels and frequencies of their detection were compared.

RESULTS

The IL-1 beta level and frequency of detection showed no correlation with pain upon joint movements or with the X-ray and MRI findings. In the frequency of detection of IL-6, there were significant differences between control (no detection) and all chronic TMJ disorder groups that were classified by imaging diagnosis (P < 0.001). A correlation was also noted between the presence of IL-6 and pain upon joint movements. The IL-6 level was correlated with the TIMP-1 level and with pain upon joint movements. TIMP-1 level was correlated with pain upon joint movements. The TIMP-1 was present in higher level from patients with chronic TMJ disorders who exhibited osseous changes on the X-ray images.

CONCLUSION

The results indicated that the IL-6 and TIMP-1 levels in the TMJ aspirates of patients with chronic TMJ disorders have been raised. The former was not detected in the TMJ aspirates of the control. These findings suggest that IL-6 and TIMP-1 might play a role in the etiology of chronic TMJ disorders, but further studies are needed to validate this.

New biochemical insights into the pathogenesis of osteoarthritis and the role of laboratory investigations in clinical assessment

Osteoarthritis (OA) is among the most frequent diseases in the population and a common cause of pain and disability in adults. The principal disease hallmarks for assessment of OA are still clinical observation and radiographic aspects. However, the efficacy of therapeutic interventions is complicated by the time required to observe radiographic signs, useful for both diagnosis and assessment. Thus, laboratory markers have received growing attention in recent years, in an attempt to improve diagnosis, assessment of disease activity and severity, and evaluation of therapeutic effects. Many biomarkers have been proposed, in particular those reflecting cartilage and bone turnover and synovitis. Among these, COMP, antigenic keratan sulphate, hyaluronan, YKL-40, type III collagen N-propeptide, and urinary glucosyl-galactosyl pyridinoline appear to be the most promising. However, serum or urinary determinations of these molecules are difficult to interpret adequately due to their complex metabolism. New ultrasensitive methods for C-reactive protein have improved the usefulness of this marker, especially in the assessment of disease activity. Routine examination of synovial fluid is still essential for diagnosis and includes leukocyte count and crystal detection; specialized testing includes the evaluation of the levels of markers of local inflammation such as metalloproteinases and cytokines, which appear to be crucial to the pathogenesis of OA.

Autologous chondrocyte implantation (ACI) for aged patients: development of the proper cell expansion conditions for possible therapeutic applications

OBJECTIVE

Proliferation and chondrogenic commitment of cultured articular chondrocytes are impaired when cells derive from aged donors. In those subjects the feasibility of cell-based therapies for articular surface repair is reduced. Moreover, the use of serum as medium supplement elicits non-physiological responses in cultured chondrocytes. This study was therefore undertaken to identify the expansion culture conditions needed to sustain growth and chondrogenic commitment of chondrocytes harvested from aged human subjects.

DESIGN

Articular cartilage was obtained from aged (69-75 years) and from young adult subjects (27-35 years). Chondrocytes were isolated and cultured in serum-free (SF) or in serum-supplemented [fetal calf serum (FCS)] conditions. Chondrocytes were expanded in monolayer for five duplications and processed for RNA extraction and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. The differentiation potential was assessed by micromass pellet cultures before and after expansion in either culture medium, or after a prolonged exposure to serum followed by a period in SF condition.

RESULTS

Only SF-cultured chondrocytes reached five duplications within 25-35 days, maintaining the expression of some chondrogenic markers and without altering the levels of active matrix metalloproteinase 3 (MMP-3). Only the pellets derived from SF-expanded cultures positively stained for cartilage matrix deposition. On the contrary, exposure to serum diminished the proliferation capacities, abolished the differentiation potential in the same cells and elicited transcription of the MMP-3 gene. Shifting culture conditions from FCS to SF resumed growth rates but proper extracellular matrix deposition was only partially restored.

CONCLUSIONS

The SF conditions have proven valuable to prime cell proliferation and to sustain proper commitment in chondrocytes from aged patients. This culturing approach may represent a therapeutic chance extendable to a range of patients normally excluded from clinical protocols based on autologous chondrocyte implantation (ACI).

Tenascin and aggrecan expression by articular chondrocytes is influenced by interleukin 1beta: a possible explanation for the changes in matrix synthesis during osteoarthritis

OBJECTIVE

To analyse the distribution patterns of tenascin and proteoglycans in normal and osteoarthritic cartilage, and to determine the effect of interleukin 1beta (IL1beta) on aggrecan and tenascin expression by human articular chondrocytes in vitro.

METHODS

Normal and osteoarthritic cartilage and bone samples were obtained during total knee replacements or necropsies. After fixation and decalcification, paraffin embedded specimens were sectioned perpendicular to the surface. Specimens were graded according to Mankin and subdivided into those with normal, and mild, moderate, and severe osteoarthritic lesions. Serial sections were immunostained for tenascin. Tenascin expression by healthy and osteoarthritic chondrocytes was quantified by real time polymerase chain reaction (PCR). Furthermore, in cell culture experiments, human articular chondrocytes were treated with 0.1 or 10 ng/ml IL1beta. Real time PCR analyses of aggrecan and tenascin transcripts (normalised 18S rRNA) were conducted to determine the effect of IL1beta on later mRNA levels.

RESULTS

Tenascin was immunodetected in normal and osteoarthritic cartilage. In osteoarthritic cartilage increased tenascin staining was found. Tenascin was found specifically in upper OA cartilage showing a strong reduction of proteoglycans. Greatly increased tenascin transcript levels were detected in osteoarthritic cartilage compared with healthy articular cartilage. IL1beta treatment of articular chondrocytes in vitro significantly increased tenascin transcripts (approximately 200% of control) and strongly reduced aggrecan mRNA levels (approximately 42% of control).

CONCLUSIONS

During progression of osteoarthritis the switch in matrix synthesis occurs mainly in upper osteoarthritic cartilage. Furthermore, changes in synthesis patterns of osteoarthritic chondrocytes may be significantly influenced by IL1beta, probably diffusing from the joint cavity within the upper osteoarthritic cartilage.

Laboratory investigations in osteoarthritis

Progress in the knowledge of pathogenic mechanisms and a better definition of the disease, together with the availability of new technologies, have recently improved the value of laboratory investigations in osteoarthritis (OA). The main objectives of these findings are early diagnosis, assessment of disease activity and severity, and evaluation of therapeutic effects. In this context, biochemical markers are potentially useful, as they are non-invasive and non-expansive. However, among the numerous substances increasingly proposed for these purposes, very few may be considered as true disease markers in OA; COMP, antigenic keratan sulphate, hyaluronic acid, YKL-40, type III collagen N-propeptide and urinary glucosyl-galactosyl pyridinoline seem to be the most promising. However, serum or urinary determinations of these molecules are difficult to interpret adequately, due to their complex metabolism. Careful analysis of synovial fluid, mainly directed to leukocyte count and crystal detection, is still essential for diagnosis, but also for the evaluation of the levels of important markers of local inflammation, such as metalloproteinases and cytokines, which seem to be crucial in the pathogenesis of OA.

Susceptibility to physiological concentrations of IL-1beta varies in cartilage at different anatomical locations on human osteoarthritic knee joints

OBJECTIVES

To determine whether cartilage biopsies from specific regions of osteoarthritic knee joints differ in susceptibility to the degradative effects of the amounts of interleukin-1 beta (IL-1 beta; 1-10 pg/ml) found in osteoarthritic joints. To establish whether biopsies are sensitive to the effects of either IL-1 beta or TNFalpha or both catabolic cytokines.

METHODS

Cartilage from specified regions of 22 osteoarthritic knee joints was examined. Biopsies were incubated for 14 days without or with IL-1 beta or TNFalpha at physiological concentrations and GAG release into supernatants assessed.

RESULTS

Variation was observed in susceptibility to the effects of 1-10 pg/ml IL-1 beta in biopsies from different sites within the same joints and the same site in different joints. The number of regions responding to the cytokine increased significantly (P< 0.0063, Chi square test) with concentration: only 10% (2/21) of all regions tested were susceptible to the effects of 1 pg/ml IL-1 beta, whereas 45% (9/20) were susceptible to the effects of 5 pg/ml and 56% (10/18) to the effects of 10 pg/ml IL-1 beta. Significantly fewer regions (4%, 2/47) responded to both IL-1 beta and TNFalpha (P< 0.047, Chi square test); biopsies from some patients responded to neither cytokine.

CONCLUSIONS

IL-1 beta, at the low concentrations detected in joints, can degrade cartilage from susceptible locations. Susceptibility of some cartilage biopsies to the effects of either IL-1 beta and TNFalpha, but not both, suggests the signalling receptors for the two major catabolic cytokines are not usually expressed concurrently. The fact that some biopsies respond to neither cytokine suggests that in some patients the local concentration of inhibitors may be high or that other catabolic stimuli predominate. These results could have important implications for pharmacological intervention strategies.

Intercellular signaling as a cause of cell death in cyclically impacted cartilage explants

Recently, in vitro cartilage studies have shown that impact loading can produce structural damage and osteoarthritis-like changes, including tissue swelling, collagen denaturation, and cell death.

OBJECTIVE

This study was to determine whether a signal for cell death moves through the cartilage matrix, resulting in the spread of cell death over time from impacted to unimpacted regions.

DESIGN

Cyclic impacts were applied to the 2 mm core of 4 mm cartilage discs. Post-impact culturing extended for 3, 6 or 21 days and occurred in one of two ways. In one, discs were cultured intact. In the second, cores were removed immediately after cessation of impact and cores and rings cultured separately. Cells in apoptosis and later stage necrosis were monitored using the TUNEL assay.

RESULTS

The extent of cell death in impacted samples increased with increased duration of post-impact culturing. At the early time, the majority of cell death was located in the regions of direct impact whereas after extended culture, the extent of cell death was similar in the surrounding unimpacted regions and in the impacted core region. However, the physical separation of the impacted core from the surrounding, non-impacted ring regions immediately after impact, and prior to independent culture, kept the level of cell death in the surrounding ring close to control levels, even after 21 days of incubation.

DISCUSSION

These findings indicate that soluble intercellular signalling is involved in the spreading of cell death through the cartilage matrix, and that its effects can be prevented by physical isolation of the surrounding ring from the impacted core.

Interleukin-1beta-converting enzyme/caspase-1 in human osteoarthritic tissues: localization and role in the maturation of interleukin-1beta and interleukin-18

OBJECTIVE

To study the expression and production of interleukin-1beta-converting enzyme (ICE) in human normal and osteoarthritic (OA) cartilage and synovium, quantitate the level of ICE in OA chondrocytes, and examine the relationship between the topographic distribution of ICE, interleukin-1beta (IL-1beta), and IL-18, as well as apoptosis of chondrocytes.

METHODS

The expression and synthesis of ICE were investigated in human normal and OA cartilage and synovial membrane using in situ hybridization and immunohistochemical methods. The intracellular level of ICE in OA chondrocytes was also measured by enzyme-linked immunosorbent assay (ELISA). Furthermore, the topographic relationship between the presence of ICE and mature IL-1beta and IL-18 was examined by immunohistochemistry, and apoptotic chondrocytes by the TUNEL technique.

RESULTS

ICE was expressed and synthesized in both human synovial membrane and cartilage, with a significantly greater number of cells staining positive in OA tissue than in normal tissue. ICE production was preferentially located in the superficial and upper intermediate layers of articular cartilage. With a specific ELISA, a level of 230.2+/-22.5 pg/5 x 10(5) cells (mean +/- SEM) of ICE was found in OA chondrocytes. In cartilage, IL-1beta and IL-18 stained positive at a topographic location similar to that of ICE. The production of mature IL-1beta in OA cartilage explants and chondrocytes was completely blocked by treatment with a specific ICE inhibitor, which also markedly diminished the number of IL-18-positive cells. The data show that there was no close relationship between the presence of ICE and the presence of apoptotic chondrocytes in OA cartilage.

CONCLUSION

This study shows, for the first time, the presence of active ICE in human articular cartilage, with a markedly increased cellular level in OA tissue. The relationship between active IL-1beta and ICE suggests that ICE may promote OA progression by activating this proinflammatory cytokine. The role of IL-18 in pathologic cartilage is discussed.

Pharmacological influence of antirheumatic drugs on proteoglycans from interleukin-1 treated articular cartilage

The purpose of this study was to examine whether drugs used in the treatment of arthritic disorders possess any inhibitory potential on the proteoglycanolytic activities of matrix metalloproteinases (MMPs), and to determine whether drugs which inhibit these enzymes also modulate the biosynthesis and release of proteoglycans (PGs) from interleukin-1-(IL-1) treated articular cartilage explants. The cartilage-bone marrow extract and the glycosaminoglycan-peptide complex (DAK-16) dose-dependently inhibited MMP proteoglycanases in vitro when tested at concentrations ranging from 0.5 to 55 mg/mL, displaying an IC50 value of 31.78 mg/mL and 10.64 mg/mL (1.9 x 10[-4] M) respectively. (R,S)-N-[2-[2-(hydroxyamino)-2-oxoethyl]-4-methyl-1-oxopentyl++ +]-L-leucyl-L-phenylalaninamide (U-24522) proved to be a potent inhibitor of MMP proteoglycanases (IC50 value 1.8 x 10[-9] M). None of the other tested drugs, such as possible chondroprotective drugs, nonsteroidal anti-inflammatory drugs (NSAIDs), disease modifying antirheumatic drugs (DMARDs), glucocorticoids and angiotensin-converting enzyme inhibitors tested at a concentration of 10(-4) M displayed any significant inhibition. Only U-24522, tested at a concentration ranging from 10(-4) to 10(-6) M, significantly inhibited the IL-1-induced augmentation of PG loss from cartilage explants into the nutrient media, whereas DAK-16 and the cartilage-bone marrow extract were ineffective. DAK-16 and the cartilage-bone marrow extract did not modulate the IL-1-mediated reduced biosynthesis and aggregability of PGs by the cartilage explants. The addition of 10(-5) M U-24522, however, partially maintained the aggregability of PGs ex vivo. In our experiments, both possible chondroprotective drugs as well as U-24522 demonstrated no cytotoxic effects on chondrocytes.

Calcitonin inhibits phospholipase A2 and collagenase activity of human osteoarthritic chondrocytes

Calcitonin (CT) is a known potent inhibitor of bone resorption but its effect on cartilage enzymatic degradation has been incompletely studied. Salmon CT, at a concentration of 0, 0.1, 0.25, 0.5, 2.5 and 50 ng/ml, was added at 24 or 72 h to the culture medium of chondrocytes from human osteoarthritic hips and knees. The spontaneous collagenolytic activity, measured using a radiolabeled type II collagen, was inhibited by CT in a dose-dependent manner. However, CT had no effect on the total collagenolytic activity assayed after APMA activation. Stromelysin and plasmin activity, measured by degradation of casein and a synthetic substrate, were also unaffected by CT. Chondrocyte phospholipase A2 activity, assayed using a labeled specific substrate, was decreased by CT. Chondrocyte pre-incubation with CT significantly decreased the cell binding of labeled TNF alpha, but did not affect IL-1 beta cell binding. Attachment of chondrocytes on fibronectin was markedly stimulated by CT, while attachment to type II collagen was not. Significant effects were obtained using at least 2 or 5 ng/ml of CT. CT appears to decrease collagenolytic activity by decreasing its activation and/or increasing its inhibition by tissue inhibitors of metalloproteinases (TIMP). CT might act on osteoarthritic chondrocyte activation via mechanisms such as phospholipase A2 activity, human necrosis factor-alpha or fibronectin receptor expression.

Effects of misoprostol and prostaglandin E2 on proteoglycan biosynthesis and loss in unloaded and loaded articular cartilage explants

The effects of misoprostol, a prostaglandin E1 analog, and prostaglandin E2 on proteoglycan biosynthesis and loss were studied in unloaded and mechanically loaded mature bovine articular cartilage explants. The prostaglandins were administered daily at dosages of 0, 10, 100 and 1000 eta g/ml for up to seven days, and proteoglycan biosynthesis determined by measurement of radiolabelled sulfate incorporation. The presence of misoprostol lead to a significant (p < 0.001) dose-dependent inhibition (30%-50%) in proteoglycan biosynthesis which was also dependent on exposure time (p < 0.05). A significant decrease in biosynthesis (34%) was also found for prostaglandin E2, but only at the highest dose (1000 eta g/ml). Proteoglycan catabolism rates were not affected by either substance as assessed by loss of newly synthesized proteoglycan. The application of a continuous cyclic mechanical compressive load (stress of 1.0 MPa at 1 hertz for 24 hours) resulted in a significant inhibition of proteoglycan biosynthesis (up to 50%) as compared to unloaded explants. However, there was no additive effect when mechanical load and misoprostol or prostaglandin E2 were combined. These results suggest that prostaglandins may have a role in the degenerative and repair process in various forms of arthritis where elevated intra-articular levels of prostaglandin E2 are present.

Role of inflammatory mediators and adhesion molecules in the pathogenesis of aseptic loosening in total hip arthroplasties

Concentrations of prostaglandin E2, interleukin-6, and interleukin-8 were determined in the hip joint synovial fluid of 20 patients undergoing primary (n = 12) and revision (n = 8) total hip arthroplasties. Levels of soluble adhesion molecules were also investigated in these patients. There was a significant and marked increase in levels of prostaglandin E2 (P < .001), interleukin-6 (P < .011), interleukin-8 (P < .0002), soluble intercellular adhesion molecule 1 (P < .07), soluble vascular adhesion molecule 1 (P < .0006), and soluble endothelial leukocyte adhesion molecule 1 (P < .0003) in joint fluid of patients undergoing revision. On the basis of these observations, it is suggested that synovial fluid and its inflammatory contents could play a significant role in the pathogenesis of aseptic loosening in total hip arthroplasties.