Serum levels of cartilage oligomeric matrix protein. A predicting factor and a valuable parameter for disease management in rheumatoid arthritis

Cartilage and bone loss in premenopausal women with rheumatoid arthritis: Radiological and laboratory assessments

INTRODUCTION

To investigate the radiological and laboratory features of bone and cartilage losses in premenopausal women with rheumatoid arthritis (RA).

METHODS

This case-control study is the continuation of a study that was conducted on 48 women with RA and 48 matched healthy volunteers. All RA patients were previously subjected to clinical examination, disease activity assessment using the 28-joint Disease Activity Score (DAS28) and Clinical Disease Activity Index (CDAI), serological tests, dual-energy X-ray absorptiometry measuring bone mineral density (BMD), and plain X-ray of both hands. Added to these, matrix metalloproteinase 3 (MMP-3) and cartilage oligomeric matrix protein (COMP) were measured by enzyme-linked immunosorbent assay.

RESULTS

There were statistically significant differences between patients and controls regarding COMP and MMP-3, being higher in patients (p < .001). COMP and MMP-3 have significant positive correlation with serum levels of anti-cyclic citrullinated peptide (anti-CCP) and anti-carbamylated protein (anti-CarP). The original Sharp erosion score was positively correlated with the serum level of the studied antibodies and disease duration, but no significant correlation was found with either COMP, MMP-3, or DAS-28. Spine BMD and Z score were negatively correlated with disease activity and anti-CarP. There were significant positive relationhsips between indices of local cartilage and bone loss and the indices of systemic bone loss. MMP-3 had no correlation with indices of local cartilage and bone loss and disease activity scores.

CONCLUSIONS

The pathogenic mechanism of hand joint damage involved the three studied autoantibodies namely, rheumatoid factor, anti-CCP and anti-CarP antibodies. Anti-CarP antibody was involved in the reduction of BMD of the spine. The association between systemic osteoporosis and hand joint damage pointed to a common pathogenic mechanism.

Predictors of radiographic erosion and joint space narrowing progression in patients with early rheumatoid arthritis: a cohort study

Background

Radiographic damage in rheumatoid arthritis (RA) includes erosions and joint space narrowing (JSN). Different mechanisms may underlie their development. The objective of this study was to evaluate predictors of these entities separately.

Methods

Consecutive early RA patients (symptom duration ≤12 months) from a defined area (Malmö, Sweden) recruited during 1995–2005 were investigated. Radiographs of hands and feet were scored by a trained reader according to the modified Sharp-van der Heijde score. Fat mass and lean mass distribution were measured at baseline using dual energy x-ray absorptiometry. Potential predictors of erosion and JSN progression from inclusion to the 5-year follow-up were evaluated.

Results

Two hundred and thirty-three patients were included. Radiographs at baseline and 5 years were available for 162 patients. The median (interquartile) progression of erosion and JSN scores were 4 (0–8) and 8 (1–16), respectively. Rheumatoid factor (RF) was a robust significant predictor of both erosion and JSN score progression. In adjusted analyses, anti-CCP antibodies predicted erosions while the erythrocyte sedimentation rate was predictive of both outcomes. Smoking and high baseline disease activity (DAS28 > 5.1) predicted progression of erosions. Baseline erosion score was associated with progression of both erosion and JSN progression, while baseline JSN score was predictive only of the progression of JSN. Overweight/obesity (BMI ≥ 25 kg/m²) was a significant negative predictor of JSN score progression (β = − 0.14, p = 0.018, adjusted for RF, age, baseline JSN score) also when additionally adjusting for ever smoking (p = 0.041). Among female patients, this effect was observed in those of estimated post-menopausal age (> 51 years), but not in younger women. The truncal to peripheral fat ratio was associated with less JSN score progression in women, but not in men.

Conclusions

Overweight RA patients had less JSN progression, independent of smoking status. This effect was seen in particular among older women (mainly post-menopausal), but not younger. Truncal fat was associated with less JSN progression in female patients. Smoking predicted erosion progression, and erosions may precede JSN. BMI and fat distribution may influence cartilage damage in early RA and might be related to hormonal factors.

Cartilage oligomeric matrix protein: COMPopathies and beyond

Cartilage oligomeric matrix protein (COMP) is a large pentameric glycoprotein that interacts with multiple extracellular matrix proteins in cartilage and other tissues. While, COMP is known to play a role in collagen secretion and fibrillogenesis, chondrocyte proliferation and mechanical strength of tendons, the complete range of COMP functions remains to be defined. COMPopathies describe pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED), two skeletal dysplasias caused by autosomal dominant COMP mutations. The majority of the mutations are in the calcium binding domains and compromise protein folding. COMPopathies are ER storage disorders in which the retention of COMP in the chondrocyte ER stimulates overwhelming cellular stress. The retention causes oxidative and inflammation processes leading to chondrocyte death and loss of long bone growth. In contrast, dysregulation of wild-type COMP expression is found in numerous diseases including: fibrosis, cardiomyopathy and breast and prostate cancers. The most exciting clinical application is the use of COMP as a biomarker for idiopathic pulmonary fibrosis and cartilage degeneration associated osteoarthritis and rheumatoid and, as a prognostic marker for joint injury. The ever expanding roles of COMP in single gene disorders and multifactorial diseases will lead to a better understanding of its functions in ECM and tissue homeostasis towards the goal of developing new therapeutic avenues.

Relationship between cartilage oligomeric matrix protein (COMP) and rheumatoid arthritis severity

Background

Serum cartilage oligomeric matrix protein (COMP) is a non-collagen glycoprotein produced by the cartilage, synovium, tendon, and meniscus. Recent studies showed that COMP is a reliable factor for monitoring cartilage damage.

Objective

To determine the relationship between serum COMP concentration and the severity of rheumatoid arthritis (RA).

Methods

This cross-sectional study lasted from 2013 to 2015 at the Rheumatology Clinic of Ghaem Hospital, Mashhad, Iran. The study population consisted of eligible patients who presented to our clinic during the study period. Four groups (150 subjects) were included as early RA (50 patients), late RA (50 patients), grades II and III OA (osteoarthritis) (25 cases, 17 grade II and 8 grade III joint destruction), and healthy controls (25 individuals). These were included consecutively. Serum COMP level was assessed by sandwich ELISA technique. In addition, ESR, hs-CRP, serum RF, and anti-CCP were assayed. X-rays of the knees (in OA) and hands (in RA) were examined for the degree of joint damage/erosion using the Short Erosion Scale (SES) in RA and Kellgren-Lawrence grading in OA. Analysis of variance (ANOVA) to compare mean COMP level among the groups and ROC (Receiver Operating Characteristic) analysis to determine the diagnostic accuracy of COMP in diagnosis of late RA were used by SPSS software (ver. 20.0).

Results

Mean (±SD) serum COMP levels were 18 (±10.6) U/L in early RA, 19.3 (±9.6) U/L in late RA, 10.9 (±4.5) U/L in OA, and 4.2 (±3.8) in controls; p<0.001. Serum COMP level was higher in RA and OA groups when compared to control group. Mean (±SD) SES score was 13.5 (±7.5) in early RA and 16.4 (±9.7) in late RA (p=0.093). There was a significant positive correlation between COMP level and disease severity in early RA (r=0.677, p<0.001) as well as in late RA (r=0.753, p<0.001). Serum COMP level at a concentration of 15.25 U/L had a sensitivity of 68% and specificity of 70% to discriminate late RA from early RA (area under curve= 69% (95% CI: 58% to 79%; p=0.001).

Conclusion

COMP had positive significant correlation with early and late RA severity. This serum biomarker can be a useful and easy tool for monitoring of RA patients either at early or late stages of the disease.

Serum and synovial cartilage oligomeric matrix protein levels in early and established rheumatoid arthritis

OBJECTIVE

To assess cartilage oligomeric matrix protein (COMP) levels in serum and synovial fluid in patients with early and established rheumatoid arthritis (RA), and to correlate the levels with clinical, laboratory and radiological characteristics.

PATIENTS AND METHODS

The study included 24 female RA patients. Full medical history was taken, thorough clinical examination and laboratory investigations performed, and body mass index (BMI) recorded. Radiological damage was assessed according to the modified Larsen score. Disease activity score 28 (DAS28) was calculated. The control group comprised 30 age- and gender-matched healthy subjects. Serum and synovial COMP levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Mean patient age was 44.04 ± 10.5 years. Of the 24 patients, 12 had early RA and 12 had established disease with joint destruction; 5 of each group had knee effusion. Serum COMP was significantly higher in patients (19.54 ± 5.47 µg/ml) compared to controls (5.93 ± 1.95 µg/ml; p < 0.001) and was also significantly higher in patients with established disease (23.9 ± 3.1 µg/ml) compared to those in early stages (15.1 ± 3.2 µg/ml; p < 0.001). Synovial COMP was also significantly increased in established compared to early-stage RA (31.2 ± 9.8 µg/ml vs. 51.6 ± 10.4 µg/ml; p = 0.013). Serum and synovial COMP significantly correlated with age, disease duration, BMI, DAS28 and modified Larsen score. On performing regression analysis in RA patients, only BMI could predict the serum level of COMP (p = 0.02).

CONCLUSION

COMP is a promising biomarker for disease activity in RA, making it a potential therapeutic target. The obvious correlation with the BMI throws light on the importance of weight control not only in osteoarthritis (OA), but also in RA.

Beneficial effects of natural eggshell membrane (NEM) on multiple indices of arthritis in collagen-induced arthritic rats

OBJECTIVES

This study was performed to evaluate the potential efficacy of natural eggshell membrane (NEM) in collagen-induced arthritic rats, a well-established rodent model of inflammation and rheumatoid arthritis.

METHODS

Rats with developing type II collagen-induced arthritis (CIA) were treated once daily by oral gavage on study days -14 to 17 with vehicle or NEM (52 mg/kg body weight). Rats were euthanized on study day 17. Efficacy was assessed by daily ankle caliper measurements, ankle diameter expressed as area under the curve (AUC_d0-17), and histopathologic evaluation of ankles and knees. Serum biomarkers of cartilage function and inflammation [collagen type II C-telopeptide (CTXII), cartilage oligomeric matrix protein (COMP), and alpha-2-macroglobulin (A2M)] were measured by ELISA.

RESULTS

Treatment with NEM resulted in significant beneficial effects on the daily ankle diameter measurements and ankle diameter AUC. Ankle and knee histopathology scores were significantly reduced (36% and 43% reduction of summed individual histopathology scores for ankle and knee, respectively; p < 0.05) toward normal for rats given NEM compared to vehicle controls. The percent reduction of serum CTXII, COMP, and A2M in NEM-treated rats ranged from 30% to 72% (p < 0.05).

CONCLUSIONS

NEM significantly improved multiple aspects of inflammatory arthritis including inflammation, pannus, cartilage damage, bone resorption, and periosteal bone formation. This study provides further support for the use of CTXII, COMP, and A2M as relevant biomarkers that were responsive to NEM.

The relationship of antibodies to modified citrullinated vimentin and markers of bone and cartilage destruction in rheumatoid arthritis

Objective. To make individualised decisions regarding treatment is one of the most important challenges in clinical practise, and identification of sensitive and specific markers of prognosis is an important research question. The main objective of this study was to evaluate relationships between the level of autoantibodies, radiographic changes and laboratory markers of bone, and cartilage destruction. Methods. A total of 114 RA patients were examined. The serum concentration of IgM RF, antibodies to cyclic citrullinated peptide (anti-CCP), modified citrullinated vimentin (anti-MCV), matrix metalloproteinase 3 (MMP-3), and cartilage oligomeric matrix protein (COMP, ng/mL) were measured. The van der Heijde-modified Sharp Score was used to quantify the radiologic changes. Results. Among the patients who were high-positive for anti-MCV, the value of total modified Sharp score (mTSS) (96.5; 66-120) was higher as well as the joint space narrowing (82; 60.5-105.5), and a higher level of MMP-3 was recorded more frequently (56%) in comparison with negative/low-positive patients (57; 31-88, 50; 29-82, 31% resp., P < 0.05). The level of COMP was also higher among patients high-positive for anti-MCV (9.7; 8.1-13.1 and 6.8; 5.4-10.7, resp., P = 0.02). Conclusion. A high positive level of anti-MCV as contrasted with anti-CCP and IgM RF is associated with more pronounced destructive changes in the joints.

Effect of Ultra-marathon (308 km) Race on Bone Metabolism and Cartilage Damage Biomarkers

Objective

To evaluate the potential effects of a 308-km ultra-marathon on bone and cartilage biomarkers.

Method

Venous blood samples were collected at pre-race, 100 km, 200 km, and 308 km checkpoints. The following markers of cartilage damage and bone metabolism were studied: osteocalcin (OC), osteoprotegerin (OPG), and calcium, phosphorous, and cartilage oligomeric matrix protein (COMP).

Results

Blood samples were taken from 20 male runners at four different checkpoints. Serum COMP was increased by 194.1% (130.7% at 100 km and 160.4% at 200 km). Serum OPG was significantly increased by 158.57% at 100 km and 114.1% at 200 km compared to the pre-race measures. OC was transiently suppressed at 200 km. Serum calcium and phosphorous concentrations decreased compared to the pre-race measures.

Conclusion

This study showed that the 308-km ultra-marathon induced several changes, including transient uncoupling of bone metabolism, increased bone resorption, suppressed bone formation, and bone turnover and had a major impact on cartilage structure.

Cartilage Oligomeric Matrix Protein Associates Differentially with Erosions and Synovitis and Has a Different Temporal Course in Cyclic Citrullinated Peptide Antibody (Anti-CCP)-positive versus Anti-CCP-negative Early Rheumatoid Arthritis

Objective.

Cyclic citrullinated peptide antibody (anti-CCP)-positive and anti-CCP-negative rheumatoid arthritis (RA) have been suggested as 2 distinctive disease subsets with respect to disease activity and prognosis. Previously, we proposed that anti-CCP antibodies might have a chondrocyte-suppressive effect. We aimed to compare circulating cartilage oligomeric matrix protein (COMP), a marker of cartilage turnover, in untreated anti-CCP-positive and anti-CCP-negative RA, and to study the temporal pattern of COMP through 4 years of treatment, including the relationship to imaging and clinical findings.

Methods.

A total of 160 patients with newly diagnosed RA who were naive to disease-modifying antirheumatic drugs were included in the CIMESTRA trial. Ninety healthy blood donors served as controls. Demographic and disease measures including Disease Activity Score in 28 joints, IgM rheumatoid factor, anti-CCP, Health Assessment Questionnaire, visual analog scale scores for pain and global and physician assessment, and magnetic resonance imaging (MRI) of the nondominant hand were recorded at baseline. COMP in serum was measured by ELISA at inclusion and serially through 4 years.

Results.

Median baseline COMP was higher in patients with RA [9.8 U/l (interquartile range 8.96, 10.5)] compared with controls [8.3 U/l (IQR 7.84, 8.9); p < 0.001] and remained elevated at 4 years [10.8 U/l (IQR 10.2, 11.7); p < 0.001]. At baseline, anti-CCP-positive patients had lower COMP than anti-CCP-negative patients (p = 0.048). In anti-CCP-positive patients, COMP exhibited a parabolic course over 4 years, while COMP in anti-CCP-negative patients had an almost linear course. In anti-CCP-positive patients, COMP was associated with MRI edema and erosion score, while COMP was correlated with synovitis score in anti-CCP-negative individuals.

Conclusion.

Our study provides additional evidence for the existence of different disease pathways in anti-CCP-positive and anti-CCP-negative subsets of RA, and evidence that anti-CCP antibodies may be implicated in the disease process by modifying cartilage metabolism.

Biochemical markers of ongoing joint damage in rheumatoid arthritis--current and future applications, limitations and opportunities

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease associated with potentially debilitating joint inflammation, as well as altered skeletal bone metabolism and co-morbid conditions. Early diagnosis and aggressive treatment to control disease activity offers the highest likelihood of preserving function and preventing disability. Joint inflammation is characterized by synovitis, osteitis, and/or peri-articular osteopenia, often accompanied by development of subchondral bone erosions, as well as progressive joint space narrowing. Biochemical markers of joint cartilage and bone degradation may enable timely detection and assessment of ongoing joint damage, and their use in facilitating treatment strategies is under investigation. Early detection of joint damage may be assisted by the characterization of biochemical markers that identify patients whose joint damage is progressing rapidly and who are thus most in need of aggressive treatment, and that, alone or in combination, identify those individuals who are likely to respond best to a potential treatment, both in terms of limiting joint damage and relieving symptoms. The aims of this review are to describe currently available biochemical markers of joint metabolism in relation to the pathobiology of joint damage and systemic bone loss in RA; to assess the limitations of, and need for additional, novel biochemical markers in RA and other rheumatic diseases, and the strategies used for assay development; and to examine the feasibility of advancement of personalized health care using biochemical markers to select therapeutic agents to which a patient is most likely to respond.

Cartilage and Bone Biomarkers in Rheumatoid Arthritis: Prediction of 10-year Radiographic Progression

Objective.

As current predictors of joint destruction have low specificity, serological biomarkers reflecting bone and cartilage destruction have been proposed as tools in assessing prognosis of rheumatoid arthritis (RA). We examined whether serum concentrations of a panel of biomarkers could predict radiographic progression in patients with RA.

Methods.

A cohort of 238 patients with RA was followed longitudinally for 10 years with collection of clinical data and serum samples. These analyses focus on the 136 patients with radiographs of the hands available at baseline and at 5 and/or 10 years. Radiographs were scored according to the van der Heijde-modified Sharp score (SHS). Baseline sera were analyzed for receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), human cartilage glycoprotein-39 (YKL-40), C2C, collagen cross-linked C-telopeptide (CTX-I), and cartilage oligomeric matrix protein (COMP). Multivariate linear and logistic regression analyses were used to identify predictors of radiographic progression.

Results.

Baseline CTX-I levels were higher in progressors [0.41 ng/ml (interquartile range 0.31–0.75)] than in nonprogressors [0.32 ng/ml (IQR 0.21–0.49)], and were independently associated with 10-year change in radiographic damage score [ß = 16.4 (IQR 5.7–27.1)]. We found no association between radiographic progression and baseline serum levels of RANKL, OPG, C2C, YKL-40, or COMP.

Conclusion.

This longterm followup study of patients with RA indicates a relationship between elevated CTX-I levels in serum and subsequent joint destruction. This association was, however, weak, and our study does not support that serum CTX-I or any of the other tested biomarkers will serve as more useful prognostic markers than current predictors such as anti-cyclic citrullinated peptide, radiographic damage early in the disease course, and signs of inflammation.

Application of biomarkers in the clinical development of new drugs for chondroprotection in destructive joint diseases: a review

Emerging evidence supports the concept that biochemical markers are clinically useful non-invasive diagnostic tools for the monitoring of changes in cartilage turnover in patients with destructive joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). Epidemiological studies demonstrated that measurements of different degradation products of proteins in the extracellular matrix of hyaline cartilage in urine or serum samples are (1) increased in OA or RA patients compared with healthy individuals, (2) correlate with disease activity, and (3) are predictive for the rate of changes in radiographic measures of cartilage loss. The present review provides an updated list of available biomarkers and summarize the research data arguing for their clinical utility. In addition, it addresses the question whether or not the monitoring of biomarkers during different treatment modalities could be a useful approach to characterize the chondro-protective effects of approved and candidate drugs. Finally, it briefly reviews the in vitro/ex vivo experimental settings - isolated chondrocyte cultures and articular cartilage explants - that can assist in the verification of novel markers, but also studies assessing direct effects of drug candidates on chondrocytes. Collectively, biomarkers may acquire a function as established efficacy parameters in the clinical development of novel chondro-protective agents.

Improvement of reduced serum cartilage oligomeric matrix protein levels in systemic juvenile idiopathic arthritis patients treated with the anti-interleukin-6 receptor monoclonal antibody tocilizumab

In this study, we determined serum cartilage oligomeric matrix protein (COMP) levels in systemic juvenile idiopathic arthritis (sJIA) patients during both the active and the remission phases to investigate how the growth cartilage turnover changed under tocilizumab treatment. Specimens were collected from 201 healthy children under 16 years of age with no growth impairment, and paired sera were collected from 11 sJIA patients treated with tocilizumab. Disease activity was assessed from white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and ferritin, and the COMP concentration was determined by sandwich enzyme-linked immunosorbent assay. Serum COMP concentrations were found independent of age, and the mean value in healthy children was 17.74+/-5.6 U/L. The mean serum COMP in sJIA patients during the active phase was 10.75+/-3.9 U/L, lower than that of healthy children. The mean serum COMP in the remission phase (14.89+/-3.9 U/L) was significantly higher than that in the active period (P<0.05). These results suggested that in sJIA patients, a reduced serum COMP concentration is a useful marker of active disease and growth impairment, and that the growth cartilage turnover suppressed during the active phase is improved in the remission phase under tocilizumab treatment.

Serum cartilage oligomeric matrix protein (COMP) levels in knee osteoarthritis in a Brazilian population: clinical and radiological correlation

OBJECTIVES

In this study we present data on serum cartilage oligomeric matrix protein (COMP) levels in a Brazilian population with isolated knee osteoarthritis (OA) compared to healthy controls. Clinical and radiological correlations with COMP levels were also evaluated.

METHODS

Two hundred and seventy-two patients seen at the Rheumatology Division of the Federal University of São Paulo (UNIFESP) with a symptom of 'pain in the knees' for at least 3 months were invited to participate in this study. History and clinical examination were performed in all patients. Eighty-six patients with clinical isolated knee OA according to the American College of Rheumatology (ACR) criteria and without other causes of pain in the knee were included. Fifty-eight healthy individuals were selected, matched for age and sex, and used as controls. OA evaluation included Lequesne and Western Ontario and MacMaster Universities osteoarthritis index (WOMAC) questionnaires, visual analogue scale (VAS) for pain and standard knee X-rays. Blood samples were taken from all participants and serum COMP levels were measured by enzyme-linked immunosorbent assay (ELISA). OA radiological analysis was performed using the Kellgren and Lawrence (K/L) grading scale.

RESULTS

Patients with symptomatic knee OA presented significantly higher serum COMP levels compared to healthy controls and to those with non-symptomatic narrowing of the articular space (p<0.001). Patients with clinical evidence of knee OA and without radiological abnormalities (K/L grade 0 or 1) had intermediate serum COMP levels, significantly higher than those observed in healthy controls (p<0.03).

CONCLUSIONS

We observed increased serum COMP levels in patients with symptomatic radiological knee OA. High serum COMP levels may also indicate cartilage damage in selected symptomatic patients without significant radiological abnormalities.

Predicting factors for severity of rheumatoid arthritis: a prospective multicenter cohort study of 172 patients over 3 years

Rheumatoid arthritis may take an unfavourable course leading to rapid functional decline in a certain percentage of patients. Early identification of these patients is desirable. The aim of this study was to evaluate clinical and laboratory parameters for their value in the prediction of bad outcome. A total of 172 patients with early arthritis were followed for 3 years. Higher initial values for erythrocyte sedimentation rate, IgG and IgM rheumatoid factor, serum concentration of cartilage oligomeric matrix protein, Health Assessment Questionnaire score, Larsen score of feet, disease activity score, and swollen and tender joint count predicted worse outcome. An association with the presence of IgA rheumatoid factor or anti-cyclic-citrullinated peptide could not be established. We conclude that prognosis in an individual with rheumatoid arthritis depends on many factors. The determination of independent prognostic factors for progression of rheumatoid arthritis is a valuable tool in early arthritis to select patients for more aggressive therapy.

[Evidence of cartilaginous benefit of treatment with infliximab in rheumatoid arthritis using measurement of serum COMP]

Recently, it has become possible to measure the concentration of serum cartilage oligomeric matrix protein (COMP) in various arthritis, and it is expected to be a novel biomarker indicative of cartilage destruction. In this study, we evaluated the diagnostic effectiveness of serum COMP in rheumatic diseases and analyzed the inhibition of cartilage destruction in patients with rheumatoid arthritis who were prescribed with infliximab (IFX) for one year. The changes in the concentration of serum COMP and the joint narrow space of Sharp score (Delta Sharp-JNS) were evaluated. The level of serum COMP decreased from 23.04+/-7.14 U/l to 8.69+/-2.89 U/l (p<0.005) and improved Delta Sharp-JNS (-0.50+/-6.38 points). We believed that these results were influenced by the effects of methotrexate (MTX) that was prescribed together with IFX, and we analyzed the group that was administered only MTX therapy as a reference. However, the serum COMP concentration and Sharp-JNS in the MTX group did not decrease. The serological and radiological results revealed that IFX inhibited cartilage destruction, and it is possible that serum COMP is one of the novel biomarkers in RA patients treated with anti-tumor necrosis factor-alpha antibody therapy.

Low serum level of COMP, a cartilage turnover marker, predicts rapid and high ACR70 response to adalimumab therapy in rheumatoid arthritis

The aim of this study was to evaluate serum biomarkers, used in clinical routine, to predict the American College of Rheumatology (ACR) response to long-term anti-TNF alpha treatment (adalimumab). Sera from 29 consecutive rheumatoid arthritis patients were analysed for anti-cyclic citrullinated peptide (anti-CCP), cartilage oligomeric matrix protein (COMP) and IgM and IgA RFs (class-specific rheumatoid factors) at the start of treatment with adalimumab and after 3, 6 and 12 months. The response to the therapy was evaluated by ACR 20, 50, 70 and by DAS 28 scores. The mean serum COMP level of the population did not change after treatment. However, patients with low serum COMP levels (<10 U/l) at baseline showed a significant (p<0.02) higher ACR70 response (>50%) within 3 months, and also at 6 months, than patients with higher COMP values (ACR70<20%). This was also reflected by significantly higher decrease in DAS score at 3 (p<0.02) and 6 months (p<0.01) treatments. The IgM RF titre decreased significantly (p=0.02) after the therapy, but the percentage of serum positivity for anti-CCP and IgA/IgM RF did not change. No significant correlation was shown between serum COMP levels and C-reactive protein/erythrocyte sedimentation rate during the follow-up. Neither were any correlations shown between ACR/DAS 28 scores and anti-CCP, Ig M/IgA RFs. Our data indicate that low (<10 U/l) serum COMP before starting anti-TNF alpha treatment predicts a rapid (within 3 months) and high ACR70 response compared to RA patients with higher COMP values. This might reflect different mechanisms in the cartilage process in the RA disease at that time of treatment with different therapeutic sensitivity to anti-TNF alpha treatment.

Biomarkers predict radiographic progression in early rheumatoid arthritis and perform well compared with traditional markers

OBJECTIVE

To evaluate the performance of biochemical and traditional markers in predicting radiographic progression in rheumatoid arthritis (RA).

METHODS

One hundred thirty-two patients with early RA were treated with nonbiologic therapies for 2 years and studied longitudinally. Genomic DNA was analyzed for presence of the shared epitope. Levels of matrix metalloproteinases (matrix metalloproteinase 1 [MMP-1], MMP-13, and MMP-3), tissue inhibitor of metalloproteinases 1 (TIMP-1), and cartilage oligomeric matrix protein (COMP) were assessed in serially obtained serum samples. The presence of pyridinoline (Pyr), deoxypyridinoline, glycosylated Pyr (Glc-Gal-Pyr), and C-telopeptide of type II collagen (CTX-II) was assessed in urine samples. Radiographs obtained at entry and at 2 years were evaluated using the modified Larsen score.

RESULTS

Baseline and 2-year radiographs were available from 118 patients. Larsen scores worsened during the 2 years in 50 patients, while 68 patients had no radiographic progression. Levels of a variety of biochemical markers, i.e., MMP-3, CTX-II, COMP, TIMP-1, Pyr, and Glc-Gal-Pyr, correlated significantly with radiographic progression at entry and longitudinally as assessed by area under the curve (AUC). By multivariate analysis, a model including MMP-3 and CTX-II was identified as providing the best prediction of radiographic progression at entry (predictive accuracy by receiver operating characteristic [ROC] AUC = 0.76 [95% confidence interval 0.66-0.85]), while a combination of MMP-3, CTX-II, and swollen joint count formed the best longitudinal AUC model (predictive accuracy by ROC AUC = 0.81 [95% confidence interval 0.73-0.89]). Patient-reported measures (Health Assessment Questionnaire, pain scores) were of limited use. In a subset of 50 patients who were treated with methotrexate (MTX) during the followup period, median serum MMP-3 levels decreased after the initiation of MTX therapy (P = 0.0003).

CONCLUSION

These results indicate that biochemical markers are useful predictors of radiographic progression in RA and that serum MMP-3 levels decrease significantly with MTX therapy. Multivariate models that include MMP-3 and CTX-II perform better than existing traditional markers in predicting radiographic outcome in RA.

Urine cartilage oligomeric matrix protein (COMP) measurement is useful in discriminating the osteoarthritic Thoroughbreds

OBJECTIVE

To quantify the urinary concentration of cartilage oligomeric matrix protein (COMP), and to evaluate the relationship between urinary COMP concentration and the catabolic activity of synovial fluid (SF) in diseased horses.

METHODS

COMP in horse urine was detected by immunoblotting with a monoclonal antibody (mAb; 14G4) raised against equine COMP from articular cartilage. Urine and serum samples were obtained from 83 Thoroughbred horses with aseptic joint diseases (AJD, 79 horses) or septic joint diseases (SJD, four horses) at the time of anesthesia induction, and samples of SF were obtained during surgery. Control samples of urine (n=111) were collected from normal horses free of any orthopedic diseases after they had been racing. COMP concentration was determined in all samples using inhibition enzyme-linked immunosorbent assay (ELISA) with mAb 14G4. SF samples were also used for the quantification of gelatinase activity.

RESULTS

Positive bands of COMP fragments were determined on the immunoblots with mAb 14G4. The urinary COMP concentrations in AJD and SJD horses (1.02+/-0.75 and 1.55+/-1.17 microg/100mg creatinine, respectively) were significantly higher than normal (0.57+/-0.29 microg/100mg creatinine). In 55 horses with fractures in the AJD group there was a logarithmic relationship (r=-0.45, P<0.001) between the urinary and SF COMP measurements, while the urinary COMP level was positively correlated with matrix metalloproteinase (MMP)-2 and -9 activities (r=0.30, P<0.05 and r=0.51, P<0.001, respectively) in SF.

CONCLUSIONS

The urinary COMP assay with mAb 14G4 is useful for discriminating horses with osteoarthritis. The higher COMP levels in urine from such horses would be indicative of enhanced proteolytic activity, in addition to the increased COMP levels in the diseased joints.

Biomarkers for diagnosing and monitoring autoimmune diseases

The goal of studies of autoimmune disease biomarkers is to identity markers that fluctuate with disease development and severity, but then normalize following successful therapy. The perfect marker could thus serve as a diagnostic tool, as well as a monitoring device for therapeutic drug efficacy. Current biomarker discovery efforts are focused on three groups of proteins reflective of the autoimmune disease process: (1) degradation products arising from destruction of affected tissues, (2) enzymes that play a role in tissue degradation and (3) cytokines and other proteins associated with immune activation. Potential biomarkers for two autoimmune diseases, rheumatoid arthritis and multiple sclerosis, have been described in recent publications. For rheumatoid arthritis, these markers (by group) include (1) aggrecan fragments, C-propeptide of type II collagen and cartilage oligomeric matrix protein, (2) matrix metalloprotease (MMP)-1, MMP-3 and MMP-1/inhibitor complexes and (3) thioredoxin, IL-16 and tumour necrosis factor (TNF)-alpha. For multiple sclerosis, they include (1) neurofilament light protein and glial fibrillary acidic protein, (2) MMP-2 and MMP-9 and (3) TNF-alpha and soluble vascular adhesion molecule-1. The utility of most of these markers is limited by their restriction to relatively inaccessible anatomic sites (synovial or cerebrospinal fluid). Thus, from a practical standpoint, the most useful autoimmune biomarkers will be those measurable in serum or plasma.

Serum levels of cartilage oligomeric matrix protein (COMP): a rapid decrease in patients with active rheumatoid arthritis undergoing intravenous steroid treatment

To examine the influence of intravenous steroid-treatment (IST) on serum levels of Cartilage oligomeric matrix protein (COMP) in patients with active rheumatoid arthritis (RA). Serum levels of COMP and C-reactive protein (CRP) were measured in 12 patients with highly active RA (Steinbrocker stages II-IV) and in 5 patients with highly active reactive arthritis (ReA) (positive testing for HLA-B27) before starting daily IST. Patients received a total steroid dosage between 100 and 500 mg of prednisolone. COMP was measured by a commercially available sandwich-type ELISA-kit developed by AnaMar Medical AB, Sweden. Statistical evaluation was calculated by paired t test. In the RA group, COMP levels ranged from 6.3 to 19.4 U/l (mean 12.9 U/l), CRP from 5 to 195 mg/l (mean 77.8 mg/l), the COMP levels of the ReA group ranged from 5.1 to 7.4 U/l (mean 7.9 U/l), the CRP levels from 13 to 126 mg/l (mean 49 mg/l). We found a significant difference between the initial COMP levels in RA+ and ReA patients (P<0.005). In contrast to the ReA group, serum-COMP levels of RA+ patients (P<0.004) and the VAS (P<0.0001) decreased significantly within 2-10 days after the first treatment with steroids. The CRP levels remained unchanged in both groups. Our results indicate that the intravenous treatment with steroids in patients with highly active RA leads to a significant decrease of cartilage degradation. COMP seems to be a valuable parameter not even as a prognostic factor, but as a marker for monitoring the therapy response in patients with RA.

In Vitro, Ex Vivo, andIn VivoMethodological Approaches for Studying Therapeutic Targets of Osteoporosis and Degenerative Joint Diseases: How Biomarkers Can Assist?

Although our approach to the clinical management of osteoporosis (OP) and degenerative joint diseases (DJD)-major causes of disability and morbidity in the elderly-has greatly advanced in the past decades, curative treatments that could bring ultimate solutions have yet to be found or developed. Effective and timely development of candidate drugs is a critical function of the availability of sensitive and accurate methodological arsenal enabling the recognition and quantification of pharmacodynamic effects. The established concept that both OP and DJD arise from an imbalance in processes of tissue formation and degradation draws attention to need of establishing in vitro, ex vivo, and in vivo experimental settings, which allow obtaining insights into the mechanisms driving increased bone and cartilage degradation at cellular, organ, and organism levels. When addressing changes in bone or cartilage turnover at the organ or organism level, monitoring tools adequately reflecting the outcome of tissue homeostasis become particularly critical. In this context, bioassays targeting the quantification of various degradation and formation products of bone and cartilage matrix elements represent a useful approach. In this review, a comprehensive overview of widely used and recently established in vitro, ex vivo, and in vivo set-ups is provided, which in many cases effectively take advantage of the potentials of biomarkers. In addition to describing and discussing the advantages and limitations of each assay and their methods of evaluation, we added experimental and clinical data illustrating the utility of biomarkers for these methodological approaches.

A study of the relationship between molecular biomarkers of joint degeneration and the magnetic resonance-measured characteristics of cartilage in 16 symptomatic knees

We used quantitative magnetic resonance (MR) imaging to determine if relationships exist between proposed molecular biomarkers for degenerative joint disease (DJD) and structural characteristics of articular cartilage. Subjects were eight male and eight female volunteers diagnosed with osteoarthritis. Magnetic resonance images of the symptomatic knee were taken and blood samples were drawn. Concentrations of serum cartilage oligomeric matrix protein (COMP) and cleaved collagen neoepitope were compared to cartilage volume and cartilage T2, respectively, in four compartments of the tibiofemoral joint. A significant, negative correlation was found between serum COMP and medial tibia volume in the male subject group (rho=-.738, P=.037). A significant, positive correlation (rho=.881, P=.0039) was found between serum COMP and lateral femur volume in the female subject group. In both groups, positive correlations were found between serum C2C and cartilage T2, which were significant in two compartments of the male group (rho=.714, P=.047; rho=.738, P=.037) and similarly strong, but not statistically significant (rho=.750, P=.052), in one compartment of the female group. We identify strong and biologically relevant correlations between two proposed molecular biomarkers for DJD and MR measures of symptomatic knees of a small number of arthritic patients. Our findings support the hypothesis that cartilage molecular biomarkers reflect the molecular processes of cartilage degeneration and loss.

Serum concentration of cartilage oligomeric matrix protein (COMP) is sensitive to physiological cyclic loading in healthy adults

OBJECTIVE

To test the hypothesis that physiological cyclic loading during a 30-min walking exercise causes an increase in serum cartilage oligomeric matrix protein (COMP) concentration in a healthy population.

METHODS

Blood samples (5 ml) were drawn from 10 physically active adults immediately before and after, and 0.5h, 1.5h, 3.5h and 5.5h after a 30-min walking exercise on a level outdoor walking track at self-selected normal speed. On a separate day, blood samples were drawn from the same 10 subjects during 6h while they were resting in a chair. Serum COMP concentrations were determined using a commercial enzyme-linked immunosorbent assay (COMP ELISA). An activity monitor was used to record basic time-distance measurements of gait. Serum COMP concentrations within the exercise protocol and within the resting protocol were compared using separate repeated measures analyses of variance (alpha=0.05).

RESULTS

In the exercise protocol, a first increase (9.7%; P=0.003) occurred immediately after the walking exercise. A second increase in serum COMP concentration (7.0%; P=0.024) occurred 5.5h after the walking exercise. In the resting protocol, the concentration at baseline was significantly higher than at all subsequent time points (8.2%; P<0.050). Serum COMP concentration decreased from the 3.5-h to the 5.5-h sample (-4.8%; P=0.012).

CONCLUSIONS

Even a moderate walking activity can significantly influence serum COMP concentration. The immediate response points to a diffusion time of COMP fragments from cartilage to the blood of 30 min or less. The response at 5.5h indicates a metabolic delay for COMP in the range of 5h to 6h.

Serum cathepsin K levels of patients with longstanding rheumatoid arthritis: correlation with radiological destruction

Cathepsin K is a cysteine protease that plays an essential role in osteoclast function and in the degradation of protein components of the bone matrix by cleaving proteins such as collagen type I, collagen type II and osteonectin. Cathepsin K therefore plays a role in bone remodelling and resorption in diseases such as osteoporosis, osteolytic bone metastasis and rheumatoid arthritis. We examined cathepsin K in the serum of 100 patients with active longstanding rheumatoid arthritis. We found increased levels of cathepsin K compared with a healthy control group and found a significant correlation with radiological destruction, measured by the Larsen score. Inhibition of cathepsin K may therefore be a new target for preventing bone erosion and joint destruction in rheumatoid arthritis. However, further studies have to be performed to prove that cathepsin K is a valuable parameter for bone metabolism in patients with early rheumatoid arthritis.