Osteoarthritis, an inflammatory disease: potential implication for the selection of new therapeutic targets

Arthroscopic debridement for knee osteoarthritis

BACKGROUND

Knee osteoarthritis (OA) is a progressive disease that initially affects the articular cartilage. Observational studies have shown benefits for arthroscopic debridement (AD) on the osteoarthritic knee, but other recent studies have yielded conflicting results that suggest AD may not be effective.

OBJECTIVES

To identify the effectiveness of AD in knee OA on pain and function.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2006); MEDLINE (1966 to August, 2006); CINAHL (1982 to 2006); EMBASE (1988 to 2006) and Web of Science (1900 to 2006) and screened the bibliographies, reference lists and cited web sites of papers.

SELECTION CRITERIA

We included randomised controlled trials (RCT) or controlled clinical trials (CCT) assessing effectiveness of AD compared to another surgical procedure, including sham or placebo surgery and other non-surgical interventions, in patients with a diagnosis of primary or secondary OA of the knees, who did not have other joint involvement or conditions requiring long term use of non-steroidal anti-inflammatory drugs (NSAIDs). The main outcomes were pain relief and improved function of the knee.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, assessed trial quality and extracted the data. Results are presented using weighted mean difference (WMD) for continuous data and relative risk (RR) for dichotomous data, and the number needed to treat to benefit (NNTB) or harm (NNTH).

MAIN RESULTS

Three RCTs were included with a total of 271 patients. They had different comparison groups and a moderate risk of bias. One study compared AD with lavage and with sham surgery. Compared to lavage the study found no significant difference. Compared to sham surgery placebo, the study found worse outcomes for AD at two weeks (WMD for pain 8.7, 95% CI 1.7 to 15.8, and function 7.7, 95% CI 1.1 to 14.3; NNTH=5) and no significant difference at two years. The second trial, at higher risk of bias, compared AD and arthroscopic washout, and found that AD significantly reduced knee pain compared to washout at five years (RR 5.5, 95% CI 1.7 to 15.5; NNTB=3). The third trial, also at higher risk of bias, compared AD to closed-needle lavage, and found no significant difference.

AUTHORS' CONCLUSIONS

There is 'gold' level evidence that AD has no benefit for undiscriminated OA (mechanical or inflammatory causes).

Activity and potential role of licofelone in the management of osteoarthritis

Osteoarthritis is the most common form of arthritis. It is a progressive joint disease associated with aging. It may be found in the knees, hips, or other joints. It is estimated that costs associated with osteoarthritis exceed 2% of the gross national product in developed countries. Nonsteroidal anti-inflammatory drugs (NSAIDs) are a mainstay in the treatment of inflammatory disease and are among the most widely used drugs worldwide. The main limitation in using NSAIDs consists in their side-effects, including gastrointestinal ulcerogenic activity and bronchospasm. The mechanism of action of these drugs is attributed to the inhibition of cyclooxygenase (COX), and, consequently, the conversion of arachidonic acid into prostaglandins. It is hypothesized that the undesirable side-effects of NSAIDs are due to the inhibition of COX-1 (constitutive isoform), whereas the beneficial effects are related to the inhibition of COX-2 (inducible isoform). Arachidonic acid can also be converted to leukotrienes (LTs) by the action of 5-lipoxygenase (5-LOX). Licofelone, a LOX/COX competitive inhibitor, decreases the production of proinflammatory leukotrienes and prostaglandins (which are involved in the pathophysiology of osteoarthritis and in gastrointestinal (GI) damage induced by NSAIDs) and has the potential to combine good analgesic and anti-inflammatory effects with excellent GI tolerability. Preliminary data with this drug seem promising, but further well-designed clinical trials of this agent in the elderly will be necessary before a final evaluation is possible.

Development and characterization of a fusion protein between thermally responsive elastin-like polypeptide and interleukin-1 receptor antagonist: sustained release of a local antiinflammatory therapeutic

OBJECTIVE

Interleukin-1 receptor antagonist (IL-1Ra) has been evaluated for the intraarticular treatment of osteoarthritis. Such administration of proteins may have limited utility because of their rapid clearance and short half-life in the joint. The fusion of a drug to elastin-like polypeptides (ELPs) promotes the formation of aggregating particles that form a "drug depot" at physiologic temperatures, a phenomenon intended to prolong the presence of the drug. The purpose of this study was to develop an injectable drug depot composed of IL-1Ra and ELP domains and to evaluate the properties and bioactivity of the recombinant ELP-IL-1Ra fusion protein.

METHODS

Fusion proteins between IL-1Ra and 2 distinct sequences and molecular weights of ELP were overexpressed in Escherichia coli. Environmental sensitivity was demonstrated by turbidity and dynamic light scattering as a function of temperature. IL-1Ra domain activity was evaluated by surface plasmon resonance, and in vitro antagonism of IL-1-mediated lymphocyte and thymocyte proliferation, as well as IL-1-induced tumor necrosis factor alpha (TNFalpha) expression and matrix metalloproteinase 3 (MMP-3) and ADAMTS-4 messenger RNA expression in human intervertebral disc fibrochondrocytes. IL-1Ra immunoreactivity was assessed before and after proteolytic degradation of the ELP partner.

RESULTS

Both fusion proteins underwent supramolecular aggregation at subphysiologic temperatures and slowly resolubilized at 37 degrees C. Interaction with IL-1 receptor was slower in association but equivalent in dissociation as compared with the commercial antagonist. Anti-IL-1 activity was demonstrated by inhibition of lymphocyte and thymocyte proliferation and by decreased TNFalpha expression and ADAMTS-4 and MMP-3 transcription by fibrochondrocytes. ELP domain proteolysis liberated a peptide of comparable size and immunoreactivity as the commercial IL-1Ra. This peptide was more bioactive against lymphocyte proliferation, nearly equivalent to the commercial antagonist.

CONCLUSION

The ELP-IL-1Ra fusion protein proved to retain the characteristic ELP inverse phase-transitioning behavior as well as the bioactivity of the IL-1Ra domain. This technology represents a novel drug carrier designed to prolong the presence of bioactive peptides following intraarticular delivery.

Hyaluronan suppresses IL-1beta-induced metalloproteinase activity from synovial tissue

Intraarticular injection of hyaluronan (viscosupplementation) is commonly used to treat knee pain from osteoarthritis. The therapeutic benefit might derive from hyaluronan inhibition of the activity of the cytokine-regulated catabolic enzymes that attack joint cartilage (matrix metalloproteinases). We tested the hypothesis that hyaluronan inhibited interleukin-1beta-induced matrix metalloproteinase activity secreted by explants of synovial tissue from patients with osteoarthritis and investigated the mechanism of the effect. Hyaluronan with a molecular mass of 12.8 MDa (number average) antagonized induced metalloproteinase activity in proportion to hyaluronan concentration in the clinically relevant range of 2 to 8 mg/mL. The effect was not attributable solely to molecular mass because 1.2-MDa hyaluronan produced comparable inhibition. Based on measurements involving hyaluronans of different average molecular masses, polydispersity and viscosity were similarly ruled out as primary responsible factors. The effect of hyaluronan on induced metalloproteinase activity was mediated partially by CD44, the principal cell surface receptor for hyaluronan. Hyaluronan inhibited interleukin-1beta-induced metalloproteinase production from osteoarthritic synovial tissue by a process that was not solely dependent on hyaluronan molecular mass but that was partly mediated by hyaluronan binding to CD44. The efficacy of viscosupplementation could be explained if hyaluronan also blocked catabolic enzyme activity in the joint.

Peroxisome proliferator-activated receptor gamma1 expression is diminished in human osteoarthritic cartilage and is downregulated by interleukin-1beta in articular chondrocytes

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor involved in the regulation of many cellular processes. We and others have previously shown that PPARγ activators display anti-inflammatory and chondroprotective properties in vitro and improve the clinical course and histopathological features in an experimental animal model of osteoarthritis (OA). However, the expression and regulation of PPARγ expression in cartilage are poorly defined. This study was undertaken to investigate the quantitative expression and distribution of PPARγ in normal and OA cartilage and to evaluate the effect of IL-1β, a prominent cytokine in OA, on PPARγ expression in cultured chondrocytes. Immunohistochemical analysis revealed that the levels of PPARγ protein expression were significantly lower in OA cartilage than in normal cartilage. Using real-time RT-PCR, we demonstrated that PPARγ1 mRNA levels were about 10-fold higher than PPARγ2 mRNA levels, and that only PPARγ1 was differentially expressed: its levels in OA cartilage was 2.4-fold lower than in normal cartilage (p < 0.001). IL-1 treatment of OA chondrocytes downregulated PPARγ1 expression in a dose- and time-dependent manner. This effect probably occurred at the transcriptional level, because IL-1 decreases both PPARγ1 mRNA expression and PPARγ1 promoter activity. TNF-α, IL-17, and prostaglandin E₂ (PGE₂), which are involved in the pathogenesis of OA, also downregulated PPARγ1 expression. Specific inhibitors of the mitogen-activated protein kinases (MAPKs) p38 (SB203580) and c-Jun N-terminal kinase (SP600125), but not of extracellular signal-regulated kinase (PD98059), prevented IL-1-induced downregulation of PPARγ1 expression. Similarly, inhibitors of NF-κB signaling (pyrrolidine dithiocarbamate, MG-132, and SN-50) abolished the suppressive effect of IL-1. Thus, our study demonstrated that PPARγ1 is downregulated in OA cartilage. The pro-inflammatory cytokine IL-1 may be responsible for this downregulation via a mechanism involving activation of the MAPKs (p38 and JNK) and NF-κB signaling pathways. The IL-1-induced downregulation of PPARγ expression might be a new and additional important process by which IL-1 promotes articular inflammation and cartilage degradation.

Efficacy and safety of a novel synergistic drug candidate, CRx-102, in hand osteoarthritis

OBJECTIVE

The novel synergistic drug candidate CRx-102 comprises dipyridamole and low dose prednisolone and is in clinical development for the treatment of immunoinflammatory diseases. The purpose of this clinical study was to examine the efficacy and safety of CRx-102 in patients with hand osteoarthritis (HOA).

METHODS

The study was conducted as a blinded, randomised, placebo-controlled trial at four centres in Norway. Eligibility criteria included being of age 30-70 years, at least one swollen and tender joint, a Kellgren-Lawrence (K-L) score of 2 or higher on radiographs, and a score of at least 30 mm pain on the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) visual analogue pain scale (VAS). The primary endpoint was a reduction in pain from baseline to day 42 on the AUSCAN pain subscale. Two-sided p values for the differences in least squares (LS) means adjusted for baseline are presented.

RESULTS

The mean age of the 83 patients with HOA was 60 years and 93% were females. CRx-102 was statistically superior to placebo at 42 days for changes in AUSCAN pain (LS mean -14.2 vs -4.0) and for clinically relevant secondary endpoints (joint pain VAS (-18.6 vs -6.3), patient global VAS (-15.9 vs -4.2)) in the intention to treat population. The most frequently reported adverse event during the study was headache (52% in CRx-102 vs 15% in the placebo group).

CONCLUSIONS

The novel synergistic drug candidate CRx-102 demonstrated efficacy by statistically reducing pain compared to placebo in HOA and was generally well tolerated.

Managing osteoarthritis pain when your patient fails simple analgesics and NSAIDs and is not a candidate for surgery

With no disease-modifying osteoarthritis drugs on the immediate horizon, the goal of osteoarthritis therapy remains management of pain and maintenance of function. Evidence supports use of nonpharmacologic measures including patient education, judicious exercise and weight loss, and assistive devices when appropriate to reduce pain and further loss of function. First line pharmacotherapy is acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs). However, toxicities are associated with long-term use of these drugs. Evidence also supports the use of opioids in osteoarthritis pain management when other interventions are insufficient. NSAIDs and opioids are mutually dose sparing and combining relatively low doses of a drug from each class provides synergistic analgesia while limiting toxicity. Alternative therapies include tramadol and intra-articular injections of steroids and hyaluronic acid. There is evidence to support glucosamine as an adjunct in treating osteoarthritis. Evidence is lacking to support the use of chondroitin, S-adenosyl-methionine, or dimethyl sulfoxide in osteoarthritis pain management.

Potential influence of IL1B haplotype and IL1A-IL1B-IL1RN extended haplotype on hand osteoarthritis risk

OBJECTIVE

To assess osteoarthritis (OA) association with the human interleukin-1 (IL-1) region.

DESIGN

Sixty-four European-descent cases with radiographic hand OA and 48 European-descent controls were genotyped at nine single nucleotide polymorphism (SNP), one variable-number-of-tandem-repeat (VNTR), and one microsatellite marker extending across loci for IL-1alpha (IL1A), IL-1beta (IL1B), and IL-1 receptor antagonist (IL1RN). The genotype data were used to reconstruct individual locus haplotypes, and then locus haplotypes were used as superalleles for extended haplotype reconstruction.

RESULTS

Nine different extended IL1A-IL1B-IL1RN haplotypes occurred at a frequency 0.05 or greater in either cases or controls. Only two IL1A-IL1B-IL1RN extended haplotypes were consistent with previously described extended risk haplotypes and totaled n=9 in cases and n=3 in controls [odds ratio (OR) 2.1, Haldane's chi(2) 1.67, one-sided P 0.1]. Our prior report showed hand OA association with homozygous IL1B rs1143633 minor allele genotype. All except one extended risk haplotype copy also had the IL1B rs1143633 minor allele. The rs1143633 genotype association was explained by one common six-SNP IL1B haplotype bearing rs1143633 minor allele and also risk alleles at rs1143634, rs1143627, and rs16944, component markers of the previously described extended risk haplotypes. The IL1B haplotype bearing all three risk alleles was found in 16 haplotype-homozygous hand OA cases and in four haplotype-homozygous controls and conferred OR 3.4 among homozygotes (nominal P value 0.006).

CONCLUSION

Our evidence broadly supports the genetic association of OA phenotypes with an IL-1 region extended risk haplotype and specifically IL1B genotype. The extended risk haplotype previously associated with hip OA appears to be less frequent and has weaker genetic effect in hand OA. Hand OA risk is conferred by homozygous state for the IL1B haplotype characteristic of the extended risk haplotype.

Calcineurin modulates the catabolic and anabolic activity of chondrocytes and participates in the progression of experimental osteoarthritis

OBJECTIVE

To determine whether intracellular calcineurin (Cn), a calcium-activated phosphatase, regulates the anabolic and catabolic activities of chondrocytes, and is a potential target in the treatment of osteoarthritis (OA).

METHODS

CnA expression was examined in cartilage tissue samples and cultured chondrocytes from OA patients, using immunohistochemistry and Western blot analysis, respectively. Concentrations of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases 1 (TIMP-1) in the culture supernatants were determined using enzyme-linked immunosorbent assay. Levels of nitric oxide (NO) and type II collagen (CII) were measured using the Griess reaction and Western blot analysis, respectively. In addition, the pathologic role of Cn was examined in an in vivo model in which experimental OA was induced in mice by injecting type VII collagenase into the knee joints.

RESULTS

CnA was highly expressed in the chondrocytes of lesional OA cartilage. Cyclosporin A (CSA), a Cn inhibitor, inhibited spontaneous and interleukin-1beta-stimulated production of NO, MMP-1, and MMP-3 in chondrocytes. However, CSA increased the levels of production of CII, TIMP-1, and transforming growth factor beta. Similar changes in MMP-1, NO, and CII expression levels in chondrocytes were observed after the targeted inhibition of Cn by overexpression of calcineurin binding protein 1, a natural Cn antagonist. Moreover, in the mouse model, animals treated with CSA showed a significant decrease in both the extent and the severity of cartilage damage, which were assessed macroscopically and microscopically, compared with vehicle-treated animals.

CONCLUSION

These results suggest that CnA is critically involved in the catabolic and anabolic activities of chondrocytes as well as in the progression of experimental OA. Targeted inhibition of CnA may be an effective treatment strategy for OA.

Increased level of cytokines and matrix metalloproteinases in osteoarthritic subchondral bone

OBJECTIVE

The aim of this study was to investigate the expression of several cytokines, matrix metalloproteinases (MMPs), and tissue inhibitor of matrix metalloproteinases (TIMP)-1 in osteoarthritis (OA) and control sera and different joint tissues.

METHODS

Serum, synovial fluid, cartilage, synovial and subchondral bone tissues were examined in OA and control subjects. The protein level of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1alpha, IL-8, IL-10 and MMP-2, MMP-3, MMP-9, and TIMP-1 were measured by immunoanalysis.

RESULTS

Serum levels of TNF-alpha, MMP-3 and -9 were significantly higher in OA patients than in controls. Conversely, serum IL-10 was decreased in OA patients. CRP was elevated when compared to healthy controls and decreased significantly 6 months after the surgery. In contrast to control samples, OA cartilage and synovium revealed significantly higher MMP-2, -3, -9 and IL-10. IL-1alpha was significantly higher in OA cartilage and IL-8 in OA synovium. Interestingly, MMP-3, -9, TIMP-1 and all tested cytokines were up-regulated in OA subchondral bone.

DISCUSSION

This study demonstrates pro-inflammatory condition of OA pathology and supports the idea that vascularized subchondral region may increase the synthesis of cytokines and MMPs leading to degradation of adjacent cartilage.

Physiopathologie de l'arthrose. Du cartilage normal au cartilage arthrosique: facteurs de prédisposition et mécanismes inflammatoires

INTRODUCTION

osteoarthritis is the most prevalent form of arthritis in the world. With the progressive ageing of the population, it becomes a major problem of public health. Osteoarthritis is a degenerative affection characterized by many disorders leading to a structural and functional defect of one or several joints.

CURRENT KNOWLEDGE AND KEY POINTS

In this review, we focus on the main inflammatory mechanisms occurring in cartilage during primary osteoarthritis. We also describe some well established risk factors involved in the pathogenesis of this disease such as age, overload and genetic factors. Indeed, osteoarthritis is the result of an imbalance between the processes of degradation and the attempts of repair by the chondrocyte which is the exclusive cell type in cartilage. Degradation is induced by several chemical substances such as proteolytic enzymes (metalloproteinases) and pro-inflammatory cytokines especially interleukin 1beta. To face these events, the chondrocyte starts attempts of repair by secreting growth factors (Transforming Growth Factor and Insulin Growth Factor) or anti-inflammatory cytokines (interleukins 4 and 10) unsuccessfully. All these events will lead to the structural modifications observed in the osteoarthritic cartilage.

PROSPECTS

A better comprehension of the physiopathology of osteoarthritis will allow an improvement of therapeutic strategies of this common and invalidating disease.

Effects of nimesulide on pain and on synovial fluid concentrations of substance P, interleukin-6 and interleukin-8 in patients with knee osteoarthritis: comparison with celecoxib

OBJECTIVE

This study was designed to investigate the analgesic effects of nimesulide and celecoxib in patients with knee osteoarthritis (OA). In patients with joint effusion, the effects of these non-steroidal anti-inflammatory drugs (NSAIDs) on synovial fluid concentrations of substance P (SP), interleukin (IL)-6 and IL-8 also were evaluated.

METHODS

Patients were randomly assigned either nimesulide (100 mg twice a day) or celecoxib (200 mg once a day) for 2 weeks. The intensity of joint pain was assessed with a 100-mm visual analogue scale (VAS). Furthermore, patients completed questions about analgesic efficacy and overall tolerability of the treatments on a five-point categorical scale. Synovial fluid samples were drawn at baseline, 30 min after the first drug intake (day 1), and 30 min after the last drug intake (day 14).

RESULTS

We enrolled 44 patients, 20 of whom had a joint effusion. In this group, the effects of nimesulide were more marked than for celecoxib, with evidence of a faster onset of the analgesic action. Both after a single or repeated administration, nimesulide significantly reduced the synovial fluid concentrations of SP and IL-6. Celecoxib, on the other hand, did not change the concentrations of SP and significantly reduced the levels of IL-6 only on day 14. None of the drugs affected IL-8. Both drugs were generally well tolerated.

CONCLUSIONS

These results provide evidence that nimesulide is an effective agent for the symptomatic treatment of OA. The effect on inflammatory pain mediators is consistent with the fast analgesic action of this NSAID.

MR imaging of erosions in interphalangeal joint osteoarthritis: is all osteoarthritis erosive?

OBJECTIVE

Erosive osteoarthritis is usually considered as an inflammatory subset of osteoarthritis (OA). However, an inflammatory component is now recognised in all subsets of OA, so this subgroup of erosive or inflammatory OA is more difficult to conceptualise. The aim of this study was to compare routine CR and MRI to investigate erosion numbers and morphology to determine whether hand OA in general is a more erosive disease than previously recognised.

DESIGN AND METHODS

Fifteen patients with clinical (OA) of the small joints of the hand underwent MRI of one of the affected proximal interphalangeal (PIP) or distal interphalangeal (DIP) joints. Conventional radiographs (CR) of the hand were also obtained. The MR images were reviewed by two observers for the presence of central and marginal erosions. The site and morphology of any erosions was recorded. CR images of the same hand joint were scored independently for central and marginal erosions by the same observers.

RESULTS

There was 100% agreement between the observers for scoring erosions on CR. Agreement for the MRI scores was also excellent (kappa = 0.84). MRI detected 37 erosions, of which only 9 were seen on CR. The increase in sensitivity using MRI was much greater for marginal erosions (1 detected on CR, 19 on MRI) than for central erosions (8 on CR, 18 on MRI). Using MRI 80% of joints examined showed 1 or more erosions compared with 40% using CR. If only marginal erosions were considered 80% of joints were still considered erosive by MRI criteria, but only 1 showed evidence of erosion on CR. Morphologically central erosions appeared to represent areas of subchondral collapse and pressure atrophy. In contrast, marginal erosions resembled those seen in inflammatory arthritides.

CONCLUSION

Erosions, and particularly marginal erosions typical of those seen in inflammatory arthritis, are a more common feature of small joint OA than conventional radiographs have previously indicated.

Nitric oxide synthases and osteoarthritis

The production of nitric oxide (NO) by chondrocytes is increased in human osteoarthritis. The excessive production of NO inhibits matrix synthesis and promotes its degradation. Furthermore, by reacting with oxidants such as superoxide anion, NO promotes cellular injury and renders the chondrocyte susceptible to cytokine-induced apoptosis. Thus, NO produced by activated chondrocytes in diseased cartilage may modulate disease progression in osteoarthritis and should therefore be considered a potential target for therapeutic intervention.

Stromal Cell-Derived Factor-1 Induces Matrix Metalloprotease-13 Expression in Human Chondrocytes

The production of chemokine stromal cell-derived factor (SDF)-1 is significantly higher in synovial fluid of patients with osteoarthritis and rheumatoid arthritis. Matrix metalloproteinase (MMP)-13 may contribute to the breakdown of articular cartilage during arthritis. Here, we found that SDF-1alpha increased the secretion of MMP-13 in cultured human chondrocytes, as shown by reverse transcriptase-polymerase chain reaction, Western blot, and zymographic analysis. SDF-1alpha also increased the surface expression of CXCR4 receptor in human chondrocytes. CXCR4-neutralizing antibody, CXCR4-specific inhibitor [1-[[4-(1,4,8,11-tetrazacyclotetradec-1-ylmethyl)phenyl]methyl]-1,4,8,11-tetrazacyclotetradecane (AMD3100)], or small interfering RNA against CXCR4 inhibited the SDF-1alpha-induced increase of MMP-13 expression. The transcriptional regulation of MMP-13 by SDF-1alpha was mediated by phosphorylation of extracellular signal-regulated kinases (ERK) and activation of the activator protein (AP)-1 components of c-Fos and c-Jun. The binding of c-Fos and c-Jun to the activator protein (AP-1) element on the MMP-13 promoter and the increase in luciferase activity was enhanced by SDF-1alpha. Cotransfection with dominant-negative mutant of ERK2 or c-Fos and c-Jun antisense oligonucleotide inhibited the potentiating action of SDF-1alpha on MMP-13 promoter activity. Taken together, our results provide evidence that SDF-1alpha acts through CXCR4 to activate ERK and the downstream transcription factors (c-Fos and c-Jun), resulting in the activation of AP-1 on the MMP-13 promoter and contributing cartilage destruction during arthritis.

Intra-articular injection of the cyclooxygenase-2 inhibitor parecoxib attenuates osteoarthritis progression in anterior cruciate ligament-transected knee in rats: role of excitatory amino acids

OBJECTIVE

Our present study examined the effect of intra-articular cyclooxygenase-2 (COX-2) inhibitor parecoxib on osteoarthritis (OA) progression and the concomitant changes in excitatory amino acids' (EAAs) levels of the anterior cruciate ligament-transected (ACLT) knee joint dialysates.

METHODS

OA was induced in Wistar rats by anterior cruciate ligament transection of the knee of one hindlimb, the other was left unoperated and untreated. Rats were placed into four groups: Group ACLT/P received intra-articular parecoxib injection (100 microg) in the ACLT knee once a week for 5 consecutive weeks starting at 8 weeks after surgery. Group ACLT/S received the same procedure as group ACLT/P with saline injection instead. Naïve (Naïve/P) rats received only intra-articular parecoxib injection in one knee once a week for 5 consecutive weeks without surgery. The sham-operated rats underwent arthrotomy only without treatment. Twenty weeks after surgery, knee joint dialysates were collected and EAAs' concentration was assayed by high-performance liquid chromatography, and gross morphology and histopathology (Mankin and synovitis grading) were examined on the medial femoral condyles and synovia.

RESULTS

Parecoxib alone had no effect on cartilage and synovium of normal knees in Naïve/P rats. In ACLT/P rats, parecoxib treatment showed a significant inhibition of cartilage degeneration of the medial femoral condyle at both the macroscopic level (1.15+/-0.17 vs 2.55+/-0.12, P<0.05) and the Mankin scores (3.03+/-0.28 vs 8.82+/-0.43, P<0.05). Intra-articular parecoxib injection also suppressed the synovial inflammation of ACLT joint compared to the ACLT/S group (3.92+/-0.41 vs 9.25+/-0.32, P<0.05). Moreover, glutamate and aspartate levels were also significantly reduced in the ACLT/P group compared to the ACLT/S group by parecoxib treatment (91.2+/-9.4% vs 189.5+/-17.0%, P<0.05 and 98.2+/-11.6% vs 175.3+/-12.4%, P<0.05, respectively).

CONCLUSION

This study shows that intra-articular injection of COX-2 inhibitor parecoxib inhibits the ACLT-induced OA progression; it was accompanied by a reduction of glutamate and aspartate concentration in the ACLT joint dialysates. From our present results, we suggested that intra-articular parecoxib injection, in addition to the anti-inflammatory effect, inhibiting the EAAs' release, may also play a role in inhibiting the traumatic knee injury induced OA progression.

Positron emission tomography with 18F-FDG in osteoarthritic knee

OBJECTIVES

To evaluate osteoarthritis (OA) of the knee using positron emission tomography (PET) with 2-(18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG) as a tracer.

MATERIALS AND METHODS

Fifteen patients with medial-type knee OA and three healthy subjects were enrolled in the study. After clinical examination and conventional radiography, (18)F-FDG PET and magnetic resonance imaging (MRI) were performed. (18)F-FDG uptake was quantified as a standardized uptake value (SUV) and the localization of (18)F-FDG uptake was identified using fusion images created with MRI scans.

RESULTS

(18)F-FDG generally accumulated in periarticular lesions and was absent in the articular cartilage. SUVs of the whole knee were higher in OA than in controls, and those in the medial condyle were higher than in the lateral condyle in OA. Prominent (18)F-FDG uptake was found in the intercondylar notch in OA and extended along the posterior cruciate ligament (PCL) in some cases. Periosteophytic accumulation was found in one-half of cases with definite osteophytes. Accumulation was also found in subchondral lesions and bone marrow, which corresponded with bone edema diagnosed by MRI. No significant correlation was found between SUV and clinical manifestations.

CONCLUSIONS

(18)F-FDG uptake was upregulated in OA and generally accumulated in periarticular lesions. Increased uptake was found in the intercondylar notch extending along the PCL, periosteophytic lesions, and bone marrow. These results provide in vivo pathognomonic insights into OA.

Sphingosine-1-phosphate attenuates proteoglycan aggrecan expression via production of prostaglandin E2 from human articular chondrocytes

Background

Sphingosine-1-phosphate (S1P), a downstream metabolite of ceramide, induces various bioactivities via two distinct pathways: as an intracellular second messenger or through receptor activation. The receptor for S1P (S1PR) is the family of Endothelial differentiation, sphingolipid G-protein-coupled receptor (EDG). We have here attempted to reveal the expression of EDG/S1PR in human articular chondrocytes (HAC), exploring the implications of S1P in cartilage degradation.

Methods

Articular cartilage specimens were obtained from patients with rheumatoid arthritis (RA), osteoarthritis (OA) or traumatic fracture (representing normal chondrocytes) who underwent joint surgery. Isolated HAC were cultured in vitro by monolayer and stimulated with S1P in the presence or absence of inhibitors of signaling molecules. Stimulated cells and culture supernatants were collected and subjected to analyses using reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA).

Results

All of the tested HAC samples showed positive results in terms of EDG/S1PR expression in basal condition. When HAC was stimulated with S1P, a significant increase in prostaglandin (PG) E₂ production was observed together with enhanced expression of cyclooxygenase (COX)-2. S1P stimulated extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) in HAC, and the PGE₂ induction was abrogated by PD98059 and SB203580. Pertussis toxin inhibited the PGE₂ induction from HAC by S1P, suggesting an essential role for Gi protein. S1P also attenuated the expression of proteoglycan aggrecan, a component of cartilage matrix, in HAC at transcriptional level.

Conclusion

It was suggested that the S1P-induced PGE₂ was at least in part involved in the aggrecan-suppressing effect of S1P, seeing as COX inhibitors attenuated the effect. Accordingly, S1P might play an important role in cartilage degradation in arthritides.

Correlation between inflammatory cytokines released from the lumbar facet joint tissue and symptoms in degenerative lumbar spinal disorders

BACKGROUND

Lumbar facet joint tissue has inflammatory cytokines. However, no reports have shown whether inflammatory cytokines in the facet joint leads to pain. This study was designed to characterize the correlation between inflammatory cytokines released from facet joint tissue and symptoms in degenerative lumbar spinal disorders. The purpose of this study was to seek involvement of inflammatory facet joint for radiculopathy in lumbar spinal canal stenosis with clinical and anatomical studies.

METHODS

Lumbar facet joint cartilage and synovial tissues in 40 cases of posterior lumbar surgery were harvested to measure tumor necrotizing factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) during operation. The visual analogue scale (VAS) and Roland-Morris disability questionnaire (RDQ) were used to examine the correlation between cytokine concentration and symptoms. Coloring agent was injected into facet joints of fresh cadavers to find leakage of pigment from the facet joint into the spinal canal.

RESULTS

Inflammatory cytokines were detected in the joint tissues in the lumbar spinal canal stenosis (LSCS) and lumbar disc herniation (LDH) groups. A positive reaction rate of IL-1beta was significantly higher in the LSCS group than in the LDH group. IL-1beta-positive cases in the LSCS group showed higher VAS scores for leg pain and higher RDQ scores. Intraspinal canal tissues including lumbar nerve root were stained by injection of methylene blue into the facet joints.

CONCLUSIONS

IL-1beta in facet joint cartilage in LSCS was associated with leg pain and a decline of quality of life. Inflammatory cytokines produced in degenerated facet joint may leak into the intraspinal space through the lateral part of the ventral facet joint capsule. These results suggest the involvement of inflammatory cytokines in degenerated lumbar facet joints regarding the genesis of pain production.

The role of synovial macrophages and macrophage-produced cytokines in driving aggrecanases, matrix metalloproteinases, and other destructive and inflammatory responses in osteoarthritis

There is an increasing body of evidence that synovitis plays a role in the progression of osteoarthritis and that overproduction of cytokines and growth factors from the inflamed synovium can influence the production of degradative enzymes and the destruction of cartilage. In this study, we investigate the role of synovial macrophages and their main proinflammatory cytokines, interleukin (IL)-1 and tumour necrosis factor-alpha (TNF-α), in driving osteoarthritis synovitis and influencing the production of other pro- and anti-inflammatory cytokines, production of matrix metalloproteinases, and expression of aggrecanases in the osteoarthritis synovium. We established a model of cultures of synovial cells from digested osteoarthritis synovium derived from patients undergoing knee or hip arthroplasties. By means of anti-CD14-conjugated magnetic beads, specific depletion of osteoarthritis synovial macrophages from these cultures could be achieved. The CD14⁺-depleted cultures no longer produced significant amounts of macrophage-derived cytokines like IL-1 and TNF-α. Interestingly, there was also significant downregulation of several cytokines, such as IL-6 and IL-8 (p < 0.001) and matrix metalloproteinases 1 and 3 (p < 0.01), produced chiefly by synovial fibroblasts. To investigate the mechanisms involved, we went on to use specific downregulation of IL-1 and/or TNF-α in these osteoarthritis cultures of synovial cells. The results indicated that neutralisation of both IL-1 and TNF-α was needed to achieve a degree of cytokine (IL-6, IL-8, and monocyte chemoattractant protein-1) and matrix metalloproteinase (1, 3, 9, and 13) inhibition, as assessed by enzyme-linked immunosorbent assay and by reverse transcription-polymerase chain reaction (RT-PCR), similar to that observed in CD14⁺-depleted cultures. Another interesting observation was that in these osteoarthritis cultures of synovial cells, IL-1β production was independent of TNF-α, in contrast to the situation in rheumatoid arthritis. Using RT-PCR, we also demonstrated that whereas the ADAMTS4 (a disintegrin and metalloprotease with thrombospondin motifs 4) aggrecanase was driven mainly by TNF-α, ADAMTS5 was not affected by neutralisation of IL-1 and/or TNF-α. These results suggest that, in the osteoarthritis synovium, both inflammatory and destructive responses are dependent largely on macrophages and that these effects are cytokine-driven through a combination of IL-1 and TNF-α.

The reverse glucosamine sulfate pathway: application in knee osteoarthritis

Glucosamine is a natural amino sugar and a normal constituent of glycosaminoglycans in the cartilage matrix and synovial fluid of joints. Crystalline glucosamine sulfate salt has been approved as a medicinal product for the treatment of osteoarthritis in several European countries. Nevertheless, although it has been prescribed for more than 10 years, it is only due to the research in the last 5 years that the scientific basis underlying its beneficial effects are starting to be clarified. In randomised, double-blind, placebo-controlled trials, this compound clinically controls pain and produces beneficial effects in patients with knee osteoarthritis, possibly delaying the appearance of long-term structural changes in the joint (i.e., it has a structure-modifying effect). Furthermore, it has an excellent toxicity profile. Despite the different lines of investigation that have been followed, the mechanism of action of glucosamine sulfate still remains to be clearly defined. However, the activity of glucosamine sulfate has recently been related to its capacity to downregulate the catabolic effects of pro-inflammatory molecules, such as IL-1, which are present in osteoarthritic cartilage.

Does facet joint inflammation induce radiculopathy?: an investigation using a rat model of lumbar facet joint inflammation

STUDY DESIGN

The association between lumbar facet joint inflammation and radiculopathy was investigated using behavioral, histologic, and immunohistochemical testing in rats.

OBJECTIVES

To develop a rat model of lumbar facet joint inflammation and ascertain whether facet joint inflammation induces radiculopathy using this model.

SUMMARY OF BACKGROUND DATA

Both mechanical and chemical factors have been identified as important for inducing radiculopathy. In lumbar spondylosis, facet joint osteophytes may contribute to nerve root compression, which may induce radiculopathy. Furthermore, inflammation may occur in the facet joint, as in other synovial joints. Inflamed synovium may thus release inflammatory cytokines and induce nerve root injury with subsequent radiculopathy.

METHODS

A piece of gelatin sponge containing complete adjuvant was inserted into the L5-L6 facet joint in rats (arthritis group). Saline was used in the control group. Mechanical allodynia was determined using the von Frey test. Inflammatory cells infiltrating the epidural space were counted, and changes in cartilage were assessed histologically. Tumor necrosis factor (TNF)-alpha-immunoreactive cells in the L5 dorsal root ganglion were counted.

RESULTS

Mechanical allodynia was observed in the arthritis group from day 3, gradually recovering during the observation period. Significantly larger numbers of inflammatory cells had infiltrated the epidural space by days 3 and 7 in the arthritis group than in controls. Numbers of TNF-alpha-immunoreactive cells were significantly increased at days 1 and 3 in the arthritis group compared with controls. Predominantly small nociceptive neurons were stained.

CONCLUSIONS

When inflammation was induced in a facet joint, inflammatory reactions spread to nerve roots, and leg symptoms were induced by chemical factors. These results support the possibility that facet joint inflammation induces radiculopathy.

Enumeration and phenotypical analysis of distinct dendritic cell subsets in psoriatic arthritis and rheumatoid arthritis

Dendritic cells (DCs) comprise heterogeneous subsets of professional antigen-presenting cells, linking innate and adaptive immunity. Analysis of DC subsets has been hampered by a lack of specific DC markers and reliable quantitation assays. We characterised the immunophenotype and functional characteristics of psoriatic arthritis (PsA)-derived and rheumatoid arthritis (RA)-derived myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) to evaluate their potential role in arthritis. Circulating peripheral blood (PB) pDC numbers were significantly reduced in PsA patients (P = 0.0098) and RA patients (P = 0.0194), and mDCs were significantly reduced in RA patients (P = 0.0086) compared with healthy controls. The number of circulating mDCs in RA PB was significantly inversely correlated to C-reactive protein (P = 0.021). The phenotype of both DC subsets in PsA PB and RA PB was immature as compared with healthy controls. Moreover, CD62L expression was significantly decreased on both mDCs (PsA, P = 0.0122; RA, P = 0.0371) and pDCs (PsA, P = 0.0373; RA, P = 0.0367) in PB. Both mDCs and pDCs were present in PsA synovial fluid (SF) and RA SF, with the mDC:pDC ratio significantly exceeding that in matched PB (PsA SF, P = 0.0453; RA SF, P = 0.0082). pDCs isolated from RA SF and PsA SF displayed an immature phenotype comparable with PB pDCs. RA and PsA SF mDCs, however, displayed a more mature phenotype (increased expression of CD80, CD83 and CD86) compared with PB mDCs. Functional analysis revealed that both SF DC subsets matured following toll-like receptor stimulation. pDCs from PB and SF produced interferon alpha and tumour necrosis factor alpha on TLR9 stimulation, but only SF pDCs produced IL-10. Similarly, mDCs from PB and SF produced similar tumour necrosis factor alpha levels to TLR2 agonism, whereas SF mDCs produced more IL-10 than PB controls. Circulating DC subset numbers are reduced in RA PB and PsA PB with reduced CD62L expression. Maturation is incomplete in the inflamed synovial compartment. Immature DCs in SF may contribute to the perpetuation of inflammation via sampling of the inflamed synovial environment, and in situ presentation of arthritogenic antigen.

Human articular cartilage proteoglycans are not undersulfated in osteoarthritis

Chondroitin sulfate is the major constituent of cartilage. Inadequate sulfate availability results in the production of undersulfated proteoglycans. In osteoarthritis, there is a net loss of articular cartilage proteoglycans. Theoretically, it is possible that during the progress of disease undersulfated glycosaminoglycans are synthesized producing proteoglycans with poorer biological properties. In this study, we tested whether in early human osteoarthritic articular cartilage (Mankin's score of 2 and 3) or more advanced disease (Mankin's score over 3), there are proteoglycans that contain a higher relative amount of nonsulfated chondroitin disaccharide isomer in their chondroitin sulfate chains by analyzing the molar ratios of chondroitin sulfate disaccharide isoforms with fluorophore-assisted carbohydrate electrophoresis. Our results indicated that the nonsulfated disaccharide of chondroitin sulfate formed in average only 1-2% of the total chondroitin sulfate. More important, the molar ratio of nonsulfated disaccharide did not appear to be increased in the osteoarthritic articular cartilage. We conclude that undersulfation of articular cartilage proteoglycans is not present in the human osteoarthritic joint.

Is osteoarthritis an infection-associated disease and a target for chemotherapy?

The treatment of osteoarthritis (OA) continues to be a challenge, and current treatment modalities are disappointing. New approaches in therapy may be developed as a result of evidence of the involvement of inflammatory cytokines in the progression of OA. Cotrimoxazole (sulfamethoxazole/trimethoprim) was noted to have anti-inflammatory properties and has been used in the therapy of several autoimmune diseases. Analyzing our own and world experience, we propose that OA and degenerative joint and spine disease might be infection-associated diseases and a target for sulfamethoxazole/trimethoprim therapy.

Effects of hyaluronan on nitric oxide levels and superoxide dismutase activities in synovial fluid in knee osteoarthritis

The aim of the present study was to evaluate the effects of hyaluronan (HA) on nitric oxide (NO) levels and superoxide dismutase (SOD) enzyme activities in synovial fluid (SF) in the treatment of patients with knee osteoarthritis (OA). SF samples were aspirated from OA patients before the commencement of the treatment (n=23) and 6 weeks after they were treated with HA products. NO levels and SOD activities were compared between the pre- and post-treatment of OA patients and of the control group (n=10). SF NO levels were significantly higher in patients with OA before the commencement of the treatment compared with the post-treatment (p<0.001) and the control groups. The SF SOD activity of patients before the commencement of the treatment was lower than the values in the controls and post-treatment (p<0.001). There is no significant correlation between SF NO and SOD levels and the radiographic changes of the OA knee according to Kellgren-Lawrence grading (p>0.05). Also, the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) pain scores and physical function scores were gradually improved. These findings made us think that SF NO was a potent mediator in cartilage damage in OA, whereas SOD was an antioxidant mediator in the same process. Exogenous HA injections might reduce the NO levels and increase SOD activities in synovial fluid. These effects also do not seem to be dependent on the radiographic grading of the OA knee. More comprehensive studies are needed to clarify a possible clinical significance of this topic, and we suggest that this is an important area for further research into new treatment options.

High molecular weight hyaluronic acid down-regulates the gene expression of osteoarthritis-associated cytokines and enzymes in fibroblast-like synoviocytes from patients with early osteoarthritis

OBJECTIVE

Activated synoviocytes play important roles in the progression of human osteoarthritis (OA). Intra-articular injection of high molecular weight hyaluronic acid (HMW-HA) has been used as viscosupplementation for knee OA but its effect on synoviocytes remains undisclosed. This study aims to investigate the effects of HMW-HA on the gene expression of 16 OA-associated cytokines and enzymes, including interleukin (IL)-1beta, IL-6, IL-8, leukemia inhibitory factor (LIF), tumor necrosis factor (TNF)-alpha, TNF-alpha converting enzyme (TACE), matrix metalloproteinase (MMP)-1, MMP-2, MMP-3, MMP-9, MMP-13, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, aggrecanase-1, aggrecanase-2, and inducible nitric oxide synthase (iNOS), in fibroblast-like synoviocytes (FLS) from patients with early stage OA.

METHOD

Synovial fluid-derived FLS were obtained from the knees of 15 patients with early stage OA. IL-1-stimulated or unstimulated FLS were cultured with or without the treatment of 600-800kDa HMW-HA. Moreover, blocking experiments with anti-CD44 monoclonal antibodies (mAb) were used to examine the involvement of CD44 in HMW-HA effects. We designed and validated the real-time quantitative polymerase chain reaction (Q-PCR) assays with SYBR Green dyes for simultaneous quantification of the expression of the 16 genes.

RESULTS

HMW-HA down-regulated IL-8 and iNOS gene expression in unstimulated FLS and down-regulated aggrecanase-2 and TNF-alpha gene expression in IL-1-stimulated FLS. CD44 blocking inhibited the down-regulatory effects of HMW-HA on gene expression.

CONCLUSION

HMW-HA may have a structure-modifying effect for OA by down-regulation of aggrecanase-2 in FLS. HMW-HA also has an anti-inflammatory effect by down-regulation of TNF-alpha, IL-8, and iNOS in FLS. These effects may be mediated through the interaction of CD44 and HMW-HA.

Increase in production of matrix metalloproteinase 13 by human articular chondrocytes due to stimulation with S100A4: Role of the receptor for advanced glycation end products

OBJECTIVE

S100 proteins have been implicated in various inflammatory conditions, including arthritis. The aims of this study were to determine whether chondrocytes produce S100A4 and whether S100A4 can stimulate the production of matrix metalloproteinase 13 (MMP-13) by articular chondrocytes via receptor for advanced glycation end products (RAGE)-mediated signaling.

METHODS

The expression of chondrocyte S100A4 was analyzed by immunohistochemistry using normal and osteoarthritic (OA) cartilage and by immunoblotting of chondrocyte cell lysates. RAGE signaling was examined by stimulating chondrocytes with S100A4 and monitoring for the activation of MAP kinases and NF-kappaB. Production of MMP-13 was determined in the conditioned medium. A pulldown assay using biotin-labeled S100A4 was used to demonstrate binding to RAGE.

RESULTS

S100A4 expression was detected in human articular chondrocytes by immunoblotting and appeared to increase in the cell lysates from OA tissue. Marked positive immunostaining for S100A4 was also noted in sections of human cartilage with changes due to OA. Stimulation of chondrocytes with S100A4 increased the phosphorylation of Pyk-2, MAP kinases, and activated NF-kappaB, followed by increased production of MMP-13 in the conditioned medium. This signaling was inhibited in cells pretreated with soluble RAGE, advanced glycation end product-bovine serum albumin, or the antioxidant Mn(III)tetrakis (4-benzoic acid) porphyrin, or by overexpression of a dominant-negative RAGE construct. A pulldown assay showed that S100A4 binds to RAGE in chondrocytes.

CONCLUSION

This is the first study to demonstrate that S100A4 binds to RAGE and stimulates a RAGE-mediated signaling cascade, leading to increased production of MMP-13. Since both S100A4 and RAGE are up-regulated in OA cartilage, this signaling pathway could contribute to cartilage degradation in OA.

Endothelial dysfunction and decreased vascular responsiveness in the anterior cruciate ligament-deficient model of osteoarthritis

Chronic inflammation associated with osteoarthritis (OA) may alter normal vascular responses and contribute to joint degradation. Vascular responses to vasoactive mediators were evaluated in the medial collateral ligament (MCL) of the anterior cruciate ligament (ACL)-deficient knee. Chronic joint instability and progressive OA were induced in rabbit knees by surgical transection of the ACL. Under halothane anesthesia, laser speckle perfusion imaging (LSPI) was used to measure MCL blood flow in unoperated control (n = 12) and 6-wk ACL-transected knees (n = 12). ACh, bradykinin, histamine, substance P (SP), and prostaglandin E(2) (PGE(2)) were applied to the MCL vasculature in topical boluses of 100 microl (dose range 10(-14) to 10(-8) mol). In normal joints, ACh, bradykinin, histamine, and PGE(2) evoked a dilatory response. Substance P caused a biphasic response that was dilatory from 10(-14) to 10(-11) mol and constricting at higher doses. In ACL-deficient knees, ACh, bradykinin, histamine, and SP decreased perfusion, whereas PGE(2) had a biphasic response that decreased perfusion at 10(-14) to 10(-11) mol and was dilatory at higher concentrations. Sodium nitroprusside increased perfusion in resting and phenylephrine-precontracted vessels with no significant differences between ACL-transected and control knees. Femoral artery occlusion and release increased perfusion by 74.3 +/- 11.1% in control knees but only by 25.8 +/- 4.4% in ACL-deficient knees. The altered responsiveness of the MCL vasculature to these inflammatory mediators may indicate endothelial dysfunction in the MCL, which may contribute to the progression and severity of OA and to the adaptation of the joint in an altered mechanical environment.

Effects of chronic osteoarthritis pain on neuroendocrine function in men

CONTEXT

Chronic pain has been associated with elevated cortisol, reduced LH and testosterone (T), and/or augmented circulating or excreted catecholamines. Most endocrine studies have been conducted in patients in whom the potentially confounding effects of depression, inflammatory disease, or coexistent medication use have not been controlled.

OBJECTIVE

The objective of the study was to test the hypothesis that chronic pain activates ACTH-cortisol and suppresses LH-T.

DESIGN AND SETTING

This was a case control study conducted at a clinical research center.

PARTICIPANTS

Participants included 16 opioid-naive men with chronic osteoarthritis pain, aged 35-65 yr with body mass index 20-30 kg/m2, and 12 healthy, opioid- and pain-free men of similar ages and body mass indexes.

METHODS

We compared circulating concentrations of ACTH, cortisol, LH, and T derived from every 20-min blood sampling (2000-0800 h), and 24-h urinary excretion of cortisol, epinephrine, norepinephrine, and dopamine.

RESULTS

There were no significant differences in mean or integrated concentrations of ACTH, cortisol, LH, or T, or in the corresponding approximate entropy scores in osteoarthritis patients, compared with control subjects. The 0800-h serum LH concentrations were elevated in patients vs. controls (6.42 +/- 1.65 vs. 3.99 +/- 1.54 IU/liter, mean +/- sd, P = 0.02), whereas there were no significant group differences in total or free T, SHBG, cortisol binding globulin, dehydroepiandrosterone sulfate, or urinary cortisol and catecholamines.

CONCLUSIONS

These data suggest that neuroendocrine function is not significantly altered in otherwise healthy men with chronic musculoskeletal pain and that prior reports of such hormonal abnormalities may have resulted from the confounding effects of coexistent illness or medication use.

Expression of proteinase-activated receptors (PAR)-2 in articular chondrocytes is modulated by IL-1beta, TNF-alpha and TGF-beta

OBJECTIVE

To investigate the modulation of expression of proteinase-activated receptor-2 (PAR-2) in articular chondrocytes by inflammatory cytokines.

DESIGN

Articular synovium and cartilage tissues were collected from eight patients with osteoarthritis (OA), and three patients without arthropathy ("normal"). Chondrocytes were stimulated with interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha or transforming growth factor (TGF)-beta1. The expression of PAR-2 was detected using reverse transcriptase-polymerase chain reaction (PCR), Western blotting and immunofluorescence. Quantitative PCR was performed to assess the expression levels of PAR-2 messenger RNA (mRNA).

RESULTS

The expression of PAR-2 mRNA was demonstrated in both OA and normal chondrocytes as well as in synovial fibroblasts. However, the level of PAR-2 in OA chondrocytes was much higher than in normal chondrocytes. Long-term culture revealed that PAR-2 mRNA expression was maintained up to three passages in OA but not in normal chondrocytes. IL-1beta and TNF-alpha both upregulated PAR-2 expression in normal and OA chondrocytes. In contrast, TGF-beta1 significantly decreased expression of PAR-2 in OA chondrocytes but increased PAR-2 in normal chondrocytes.

CONCLUSIONS

Overexpression of PAR-2 in OA chondrocytes is upregulated by proinflammatory cytokines IL-1beta and TNF-alpha, and down-regulated by regulatory cytokine TGF-beta1. PAR-2 may be involved in the pathogenesis of OA.

A thermally responsive biopolymer for intra-articular drug delivery

Intra-articular drug delivery is the preferred standard for targeting pharmacologic treatment directly to joints to reduce undesirable side effects associated with systemic drug delivery. In this study, a biologically based drug delivery vehicle was designed for intra-articular drug delivery using elastin-like polypeptides (ELPs), a biopolymer composed of repeating pentapeptides that undergo a phase transition to form aggregates above their transition temperature. The ELP drug delivery vehicle was designed to aggregate upon intra-articular injection at 37 degrees C, and form a drug 'depot' that could slowly disaggregate and be cleared from the joint space over time. We evaluated the in vivo biodistribution and joint half-life of radiolabeled ELPs, with and without the ability to aggregate, at physiological temperatures encountered after intra-articular injection in a rat knee. Biodistribution studies revealed that the aggregating ELP had a 25-fold longer half-life in the injected joint than a similar molecular weight protein that remained soluble and did not aggregate. These results suggest that the intra-articular joint delivery of ELP-based fusion proteins may be a viable strategy for the prolonged release of disease-modifying protein drugs for osteoarthritis and other arthritides.

NF-kappaB as a potential therapeutic target in osteoarthritis and rheumatoid arthritis

The family of nuclear factor-kappaB (NF-kappaB) transcription factors is intimately involved in the regulation of expression of numerous genes in the setting of the inflammatory response. Since inflammatory processes play a fundamental role in the damage of articular tissues, many in vitro and in vivo studies have examined the contribution of components of the NF-kappaB signaling pathways to the pathogenesis of various rheumatic diseases, in particular, of osteoarthritis (OA) and rheumatoid arthritis (RA). Inflammation, cartilage degradation, cell proliferation, angiogenesis and pannus formation are processes in which the role of NF-kappaB is prominent. Consequently, large efforts have been devoted to the study of the pharmacologic modulation of the NF-kappaB pathways. These studies have employed currently available therapeutic agents including non-steroidal anti-inflammatory drugs, corticosteroids, nutraceuticals and disease-modifying anti-rheumatic drugs, as well as novel small molecule inhibitors targeted to specific proteins of the NF-kappaB pathways. In addition, promising strategies such as improved antisense DNA therapy and RNA interference have been examined with encouraging results. However, since NF-kappaB also plays a crucial beneficial role in normal physiology and technical problems for effective gene therapy still remain, further research will be needed before NF-kappaB-aimed strategies become an effective therapy for joint diseases, such as OA and RA.

Gross, histologic, and gene expression characteristics of osteoarthritic articular cartilage of the metacarpal condyle of horses

OBJECTIVE

To identify patterns and correlations of gross, histologic, and gene expression characteristics of articular cartilage from horses with osteoarthritis.

ANIMALS

10 clinically normal horses and 11 horses with osteoarthritis of the metacarpal condyles.

PROCEDURES

Metacarpophalangeal joints were opened and digitally photographed, and gross lesions were scored and quantified. Representative cartilage specimens were stained for histologic scoring. Total RNA from dorsal and palmar articular surfaces was processed on an equine gene expression microarray.

RESULTS

Histologic scores were greater in both regions of osteoarthritic joints, compared with corresponding regions in control joints. Cartilage from the palmar aspect of diseased joints had the highest histologic scores of osteoarthritic sites or of either region in control joints. A different set of genes for dorsal and palmar osteoarthritis was identified for high and low gene expression. Articular cartilage from the dorsal region had surface fraying and greater expression of genes coding for collagen matrix components and proteins with anti-apoptotic function, compared with control specimens. Articular cartilage from the palmar region had greater fraying, deep fissures, and less expression of genes coding for glycosaminoglycan matrix formation and proteins with anti-apoptotic function, compared with cartilage from disease-free joints and the dorsal aspect of affected joints.

CONCLUSIONS AND CLINICAL RELEVANCE

Metacarpal condyles of horses with naturally occurring osteoarthritis had an identifiable and regional gene expression signature with typical morphologic features.

Prospects for disease modification in osteoarthritis

Osteoarthritis (OA) can be a progressive, disabling disease, leading to diminished quality of life, and, for over 500,000 individuals annually in the US, total joint replacement. The etiology of OA will vary among individuals, with potential roles for systemic factors (such as genetics and obesity) as well as for local biomechanical factors (such as muscle weakness, joint laxity and traumatic injury). Joint deterioration occurs over extended periods of time, and the diverse molecular mechanisms that mediate pathogenic events of early, mid and late disease are not yet fully understood. The success of biologic therapies in the treatment of rheumatoid arthritis has demonstrated that the blockade of a single dominant cytokine or regulatory molecule can prevent cartilage destruction in a complex disease, and has raised expectations that mechanism-based treatments could also be developed for patients with OA. In this review, we will address the biological mechanisms that mediate structural damage in OA and examine current targets that are candidates for disease modification. The challenges to drug development and the obstacles to disease modification strategies will also be addressed.

MRI and non-cartilaginous structures in knee osteoarthritis

Magnetic resonance imaging (MRI) provides a sensitive tool for examining all the structures involved in the osteoarthritis (OA) process. While much of the MRI literature previously focussed on cartilage, there is increasing research on whole-organ evaluation and including features such as synovitis, bone marrow edema, and meniscal and ligamentous pathology. The aim of this session at the Outcome Measures in Rheumatology Clinical Trials (OMERACT)-Osteoarthritis Research Society International (OARSI) Workshop for Consensus in Osteoarthritis Imaging was to describe the current MRI methods for identifying and quantifying non-cartilaginous structures and review their associations with both OA symptoms and structural progression. Although there is much experience in measuring synovitis (derived from the rheumatoid arthritis literature), only one study has reported an association of MRI-detected synovitis and effusions with OA pain. Bone marrow edema lesions, which may represent areas of trabecular remodelling, have been associated with pain and compartment-specific structural deterioration. MRI studies have confirmed the frequency and importance of meniscal damage in progressive cartilage loss, but not related such damage to symptoms. Osteophytes have been associated with cartilage loss and malalignment to the side of the osteophyte. Ligament damage, including anterior cruciate ligament tears, has been found more commonly than expected in painful OA knees. Improvements in quantitative and semi-quantitative assessments of non-cartilage features will greatly assist understanding of the OA process and its response to therapy.

Quantifying peri-meniscal synovitis and its relationship to meniscal pathology in osteoarthritis of the knee

The objectives of this study were to validate a semiquantitative scoring system for estimating perimeniscal synovitis in osteoarthritic (OA) knees and to examine the relationship between the extent of synovitis and the degree of meniscal pathology using gadolinium-enhanced magnetic resonance imaging (MRI). Forty-three subjects with clinically diagnosed OA knee were assessed for peri-meniscal synovitis using gadolinium-enhanced MRI. Quantitative measurements of synovitis were made by summing areas in consecutive slices within generated regions of interest, and the synovitis was also scored semi-quantitatively using a 0-3 scale. Meniscal pathology (extrusion, degeneration and tearing) was also scored semiquantitatively. Establishment of a correlative relationship was undertaken using Spearman's rho (rho). A total of 86 sites were assessed. The semi-quantitative synovitis score correlated well with the quantitative synovitis score (rho>0.9). A moderate association between medial meniscal extrusion and synovitis was demonstrated (rho=0.762, P<0.000), although this association was not as strong in the lateral compartment (rho=0.524, P<0..000). The results suggest the semiquantitative scoring system is valid for assessing perimeniscal synovitis. The relationship between meniscal pathology and adjacent synovitis requires further study.

Hyaluronic acid attenuates osteoarthritis development in the anterior cruciate ligament-transected knee: Association with excitatory amino acid release in the joint dialysate

We previously reported increased release of the excitatory amino acid (EAA) neurotransmitters, glutamate and aspartate, during the early stage of experimental osteoarthritis (OA). Our present objective was to study the effect of intraarticular injection of hyaluronic acid (HA) on OA development, and to analyze concomitant changes in EAA levels in dialysates of anterior cruciate ligament-transected (ACLT) knee joints. OA was induced in Wistar rats by ACLT of one hindlimb; the knee of the other hindlimb was used as the sham-operated control. HA group (n = 12) were injected intraarticularly in the ACLT knee with 1 mg of HA once a week for 5 consecutive weeks, starting at 8 weeks after surgery. Saline group (n = 12) were injected as above with normal saline. The sham-operated group, underwent arthrotomy, but not ACLT, and received no treatment (n = 14). Twenty weeks after surgery, knee joint dialysates were collected by microdialysis and EAA levels assayed by high-performance liquid chromatography, and gross morphological examination and histopathological evaluation were performed on the medial femoral condyles and synovia. Rats receiving intraarticular HA injections showed a significantly lower degree of cartilage degeneration on the medial femoral condyle at both the macroscopic level and on the Mankin grading scale than rats receiving saline injections. Intraarticular HA treatment also suppressed synovitis. Moreover, glutamate and aspartate levels were significantly reduced in the HA group compared to the saline group. Intraarticular injection of HA limits articular cartilage and synovium damage and OA formation, and, in parallel, reduces EAA levels in ACLT joint dialysates. This study suggests that the underlying mechanism of the anti-inflammatory effect of HA is to inhibit glutamate and aspartate release in ACLT knee joints, which attenuates the early development of OA.

Interleukin-17, a regulator of angiogenic factor release by synovial fibroblasts

OBJECTIVE

Angiogenesis is a process stimulated in inflamed synovium of patients with osteoarthritis (OA), and contributes to the progression of the disease. Synovial fibroblasts secrete angiogenic factors, such as vascular endothelial growth factor (VEGF), an up-regulator of angiogenesis, and this ability is increased by interleukin (IL)-1beta. The purpose of this study was to verify whether IL-17 contributes and/or synergizes with IL-1beta and tumor necrosis factor (TNF)-alpha in vessel development in articular tissues by stimulating the secretion of proangiogenic factors by synovial fibroblasts.

DESIGN

We stimulated in vitro synovial fibroblasts isolated from OA, rheumatoid arthritis (RA) and fractured patients (FP) with IL-17 and IL-1beta and from OA patients with IL-17, IL-1beta and TNF-alpha. In the supernatants from the cultures, we assayed the amount of VEGF by immunoassay and other angiogenic factors (keratinocyte growth factor, KGF; hepatocyte growth factor, HGF; heparin-binding endothelial growth factor, HB-EGF; angiopoietin-2, Ang-2; platelet-derived growth factor B, PDGF-BB; thrombopoietin, TPO) by chemiluminescence; semiquantitative RT-PCR was used to state mRNA expression of nonreleased angiogenic factors (Ang-2 and PDGF-BB) and tissue inhibitors of metalloproteinase (TIMP)-1.

RESULTS

IL-17, TNF-alpha and IL-1beta increased VEGF secretion by synovial fibroblasts from OA patients. IL-17 and IL-1beta also increased VEGF secretion in RA and FP. Besides, IL-17 increased KGF and HGF secretions in OA, RA and FP; in OA and RA, IL-17 also increased the HB-EGF secretion and the expression of TIMP-1 as protein and mRNA. In OA patients IL-17 had an additive effect on TNF-alpha-stimulated VEGF secretion.

CONCLUSIONS

These results suggest that IL-17 is an in vitro stimulator of angiogenic factor release, both by its own action and by cooperating with TNF-alpha.

Inflammation-induced chondrocyte hypertrophy is driven by receptor for advanced glycation end products

The multiligand receptor for advanced glycation end products (RAGE) mediates certain chronic vascular and neurologic degenerative diseases accompanied by low-grade inflammation. RAGE ligands include S100/calgranulins, a class of low-molecular-mass, calcium-binding polypeptides, several of which are chondrocyte expressed. Here, we tested the hypothesis that S100A11 and RAGE signaling modulate osteoarthritis (OA) pathogenesis by regulating a shift in chondrocyte differentiation to hypertrophy. We analyzed human cartilages and cultured human articular chondrocytes, and used recombinant human S100A11, soluble RAGE, and previously characterized RAGE-specific blocking Abs. Normal human knee cartilages demonstrated constitutive RAGE and S100A11 expression, and RAGE and S100A11 expression were up-regulated in OA cartilages studied by immunohistochemistry. CXCL8 and TNF-alpha induced S100A11 expression and release in cultured chondrocytes. Moreover, S100A11 induced cell size increase and expression of type X collagen consistent with chondrocyte hypertrophy in vitro. CXCL8-induced, IL-8-induced, and TNF-alpha-induced but not retinoic acid-induced chondrocyte hypertrophy were suppressed by treatment with soluble RAGE or RAGE-specific blocking Abs. Last, via transfection of dominant-negative RAGE and dominant-negative MAPK kinase 3, we demonstrated that S100A11-induced chondrocyte type X collagen expression was dependent on RAGE-mediated p38 MAPK pathway activation. We conclude that up-regulated chondrocyte expression of the RAGE ligand S100A11 in OA cartilage, and RAGE signaling through the p38 MAPK pathway, promote inflammation-associated chondrocyte hypertrophy. RAGE signaling thereby has the potential to contribute to the progression of OA.

Long term NSAID treatment inhibits COX-2 synthesis in the knee synovial membrane of patients with osteoarthritis: differential proinflammatory cytokine profile between celecoxib and aceclofenac

OBJECTIVE

To compare the effect of celecoxib with that of a classic non-steroidal anti-inflammatory drug (NSAID) on synovial inflammation and on the synovial expression of proinflammatory genes in patients with knee osteoarthritis (OA).

METHODS

30 patients with severe knee OA scheduled for total knee replacement surgery were included in a 3 month clinical trial. They were randomised to two groups: patients treated with celecoxib (CBX) (200 mg/24 h) and patients treated with aceclofenac (ACF) (100 mg/12 h). Those patients with OA who did not want to be treated with NSAIDs served as a control group. During knee surgery, synovial fluid (SF) and synovial membrane (SM) were collected. A SM specimen was fixed and embedded in paraffin and another part was frozen for molecular biology studies.

RESULTS

At the end of study both CBX and ACF treated patients showed a significant improvement in pain and knee function compared with controls. Both drugs significantly reduced prostaglandin E(2) (PGE(2)) SF concentration and down regulated COX-2 mRNA and protein expression at the SM. However, synovial macrophage infiltration (CD68 antigen staining) and expression of proinflammatory mediators, such as interleukin 1beta and tumour necrosis factor alpha, were decreased only by CBX treatment.

CONCLUSION

Both drugs improved joint pain and function, inhibited SF PGE(2) concentration, and induced a decrease in synovial COX-2 expression and synthesis not related to the tissue inflammatory status. These data suggest that PGE(2) blocking agents may decrease PGE(2) production not only by direct COX-2 inhibition but also by down regulating COX-2 expression and synthesis. However, CBX and ACF appear to have different anti-inflammatory profiles in controlling OA synovial macrophage infiltration and proinflammatory expression.