Diurnal variation in serum levels of cartilage oligomeric matrix protein in patients with knee osteoarthritis or rheumatoid arthritis

Joint biomarker response to mechanical stimuli in osteoarthritis - A scoping review

Objective

Arthritic cartilage is primed for mechanical damage. Joint biochemical markers (JBM) could provide insight into the impact of mechanical stimulation on joint tissue turnover in osteoarthritis (OA) of potential use in clinical OA research and practice. However, existing studies of the acute impact of physical activities (PA) on JBM often contain risks of substantial bias. The purpose of this scoping review was to critically review and discuss existing reports of acute joint tissue turnover as reflected in JBM in relation to PA in OA and propose considerations for future research.

Design

We searched PubMed, Embase, and Scopus and reference lists for original reports on the acute impact of PA on JBM in human OA. Identified studies were reviewed by two reviewers forming the basis for the discussion of methodology.

Results

Search in databases resulted in nine eligible papers after full-text evaluation. Two additional papers were identified through reference lists, resulting in 11 papers included in this review. Ten investigated knee OA and one investigated hand OA. Biomarkers described were related to turnover of type II collagen, aggrecan, and cartilage oligomeric matrix protein.

Conclusions

The literature is dominated by small, simplistic studies, but suggests that mechanical stimulation can induce acute changes in joint biomarkers. In order to diminish the existing bias in future studies, it is important to recognize methodological considerations e.g. patient and biomarker selection as well as peri-interventional control. Common potential sources of bias include the acute shift in plasma volume due to cardiovascular stress and postural changes.

Delayed cartilage oligomeric matrix protein response to loading is associated with femoral cartilage composition post-ACLR

PURPOSE

To determine associations between immediate and delayed response of serum cartilage oligomeric matrix protein (sCOMP) to loading (i.e., 3000 walking steps) and femoral cartilage interlimb T1ρ relaxation times in individual's post-anterior cruciate ligament reconstruction (ACLR).

METHODS

This cross-sectional study included 20 individuals 6-12 months following primary ACLR (65% female, 20.5 ± 4.0 years old, 24.9 ± 3.0 kg/m2, 7.3 ± 1.5 months post-ACLR). Serum samples were collected prior to, immediately following, and 3.5 h following walking 3000 steps on a treadmill at habitual walking speed. sCOMP concentrations were processed using enzyme-linked immunosorbent assays. Immediate and delayed absolute sCOMP responses to loading were evaluated immediately and 3.5 h post-walking, respectively. Participants underwent bilateral magnetic resonance imaging with T1ρ sequences to calculate resting femoral cartilage interlimb T1ρ relaxation time ratios between limbs (i.e., ACLR/Uninjured limb). Linear regression models were fitted to determine associations between sCOMP response to loading and femoral cartilage T1ρ outcomes controlling for pre-loading sCOMP concentrations.

RESULTS

Greater increases in delayed sCOMP response to loading were associated with greater lateral (∆R2 = 0.29, p = 0.02) but not medial (∆R2 < 0.01, p = 0.99) femoral cartilage interlimb T1ρ ratios. Associations between immediate sCOMP response to loading with femoral cartilage interlimb T1ρ ratios were weak and non-significant (∆R2 range = 0.02-0.09, p range = 0.21-0.58).

CONCLUSION

Greater delayed sCOMP response to loading, a biomarker of cartilage breakdown, is associated with worse lateral femoral cartilage composition in the ACLR limb compared to the uninjured limb. Delayed sCOMP response to loading may be a more indicative metabolic indicator linked to deleterious changes in composition than immediate sCOMP response.

Cartilage-specific deficiency of clock gene Bmal1 accelerated articular cartilage degeneration in osteoarthritis by up-regulation of mTORC1 signaling

Although a growing body of studies recently demonstrated that circadian clock gene Bmal1 plays an important role in cartilage development and homeostasis, evidence regarding the contribution of Bmal1 in articular cartilage of OA progression is still unclear. In the present study, we investigated the direct role of Bmal1 in articular cartilage homeostasis during OA progression using tamoxifen-induced cartilage-specific knockout mice. We found that the expression of BMAL1 was decreased in OA-damaged and aging cartilage tissues. Cartilage-specific deletion of Bmal1 promoted cartilage degradation and chondrocyte apoptosis, and inhibited chondrocyte anabolism in OA mice, leading to acceleration of articular cartilage degeneration and osteophyte formation during OA progression. Mechanistic study indicated that loss of Bmal1 resulted in hyperactivation of mammalian target of rapamycin complex 1(mTORC1) signaling in OA cartilage, and pharmacological inhibition of mTORC1 signaling pathway by rapamycin alleviated partially Bmal1 ablation-induced cartilage degradation and chondrocyte apoptosis in ex vivo OA model. Therefore, our results provide the evidence of a vital role for Bmal1 in cartilage degradation in post-traumatic OA by partially regulating the mTORC1 signaling.

Fewer daily steps are associated with greater cartilage oligomeric matrix protein response to loading post-ACL reconstruction

Aberrant joint loading contributes to the development of posttraumatic knee osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR); yet little is known about the association between joint loading due to daily walking and cartilage health post-ACLR. Accelerometer-based measures of daily steps and cadence (i.e., rate of steps/min) provide information regarding daily walking in a real-world setting. The purpose of this study was to determine the association between changes in serum cartilage oligomeric matrix protein (COMP; %∆COMP), a mechanosensitive biomarker that is associated with osteoarthritis progression, following a standardized walking protocol and daily walking in individuals with ACLR and uninjured controls. Daily walking was assessed over 7 days using an accelerometer worn on the right hip in 31 individuals with ACLR and 21 controls and quantified as mean steps/day and time spent in ≥100 steps/min. Serum COMP was measured before and following a 3000-step walking protocol at a preferred speed. %∆COMP was calculated as a change in COMP relative to the prewalking value. Linear regressions were used to examine associations between daily walking and %∆COMP after adjusting for preferred speed. Fewer daily steps (ΔR²  = 0.18, p = 0.02) and fewer minutes spent in ≥100 steps/min (ΔR²  = 0.16, p = 0.03) were associated with greater %∆COMP following walking in individuals with ACLR; no statistically significant associations existed in controls (daily steps: ΔR²  = 0.03, p = 0.47; time ≥100 steps/min: ΔR²  < 0.01, p = 0.81). Clinical significance: Individuals with ACLR who engage in less daily walking undergo greater %ΔCOMP, which may represent greater cartilage degradation or turnover in response to walking.

Synthetic gene circuits for preventing disruption of the circadian clock due to interleukin-1-induced inflammation

The circadian clock regulates tissue homeostasis through temporal control of tissue-specific clock-controlled genes. In articular cartilage, disruptions in the circadian clock are linked to a procatabolic state. In the presence of inflammation, the cartilage circadian clock is disrupted, which further contributes to the pathogenesis of diseases such as osteoarthritis. Using synthetic biology and tissue engineering, we developed and tested genetically engineered cartilage from murine induced pluripotent stem cells (miPSCs) capable of preserving the circadian clock in the presence of inflammation. We found that circadian rhythms arise following chondrogenic differentiation of miPSCs. Exposure of tissue-engineered cartilage to the inflammatory cytokine interleukin-1 (IL-1) disrupted circadian rhythms and degraded the cartilage matrix. All three inflammation-resistant approaches showed protection against IL-1-induced degradation and loss of circadian rhythms. These synthetic gene circuits reveal a unique approach to support daily rhythms in cartilage and provide a strategy for creating cell-based therapies to preserve the circadian clock.

Chronic Circadian Rhythm Disturbance Accelerates Knee Cartilage Degeneration in Rats Accompanied by the Activation of the Canonical Wnt/β-Catenin Signaling Pathway

With the gradual deepening of understanding of systemic health and quality of life, the factors affecting osteoarthritis (OA) are not limited to mechanical injury, metabolic abnormality, age and obesity, etc., but circadian rhythm, which plays a non-negligible role in human daily life. The purpose of this study was to explore the molecular mechanism of chronic circadian rhythm disturbance (CRD) inducing cartilage OA-like degeneration. Rats with the anterior cruciate ligament excision transection (ACLT) were used to establish the early-stage OA model (6-week). The light/dark (LD) cycle shifted 12 h per week for 22 weeks in order to establish a chronic CRD model. BMAL1 knockdown (KD) and Wnt/β-catenin pathway inhibition were performed in chondrocytes. The contents of proinflammatory factors and OA biomarkers in serum and chondrocyte secretions were detected by ELISA. Pathological and immunohistochemical staining of articular cartilage indicated the deterioration of cartilage. WB and qPCR were used to evaluate the relationship between matrix degradation and the activation of Wnt/β-catenin signaling pathway in chondrocytes. We found that chronic CRD could cause OA-like pathological changes in knee cartilage of rats, accelerating cartilage matrix degradation and synovial inflammation. The expression of MMP-3, MMP-13, ADAMTS-4, and β-catenin increased significantly; BMAL1, Aggrecan, and COL2A1 decreased significantly in either LD-shifted cartilage or BMAL1-KD chondrocytes. The expression of β-catenin and p-GSK-3β elevated, while p-β-catenin and GSK-3β diminished. The inhibitor XAV-939 was able to mitigated the increased inflammation produced by transfected siBMAL1. Our study demonstrates that chronic CRD disrupts the balance of matrix synthesis and catabolic metabolism in cartilage and chondrocytes, and it is related to the activation of the canonical Wnt/β-catenin signaling pathway.

Marathon Running Increases Synthesis and Decreases Catabolism of Joint Cartilage Type II Collagen Accompanied by High-Energy Demands and an Inflamatory Reaction

Objective: To determine the effect of marathon running on serum levels of inflammatory, high energy, and cartilage matrix biomarkers and to ascertain whether these biomarkers levels correlate.

Design: Blood samples from 17 Caucasian male recreational athletes at the Barcelona Marathon 2017 were collected at the baseline, immediately and 48 h post-race. Serum C reactive protein (CRP), creatin kinase (CK), and lactate dehydrogenase (LDH) were determined using an AU-5800 chemistry analyser. Serum levels of hyaluronan (HA), cartilage oligomeric matrix protein (COMP), aggrecan chondroitin sulphate 846 (CS846), glycoprotein YKL-40, human procollagen II N-terminal propeptide (PIINP), human type IIA collagen N-propeptide (PIIANP), and collagen type II cleavage (C2C) were measured by sandwich enzyme-linked immune-sorbent assay (ELISA).

Results: Medians CK and sLDH levels increased (three-fold, two-fold) post-race [429 (332) U/L, 323 (69) U/L] (p < 0.0001; p < 0.0001) and (six-fold, 1.2-fold) 48 h post-race [658 (1,073) U/L, 218 (45) U/L] (p < 0.0001; p < 0.0001). Medians CRP increased (ten-fold) after 48 h post-race [6.8 (4.1) mg/L] (p < 0.0001). Mean sHA levels increased (four-fold) post-race (89.54 ± 53.14 ng/ml) (p < 0.0001). Means PIINP (9.05 ± 2.15 ng/ml) levels increased post-race (10.82 ± 3.44 ng/ml) (p = 0.053) and 48 h post-race (11.00 ± 2.96 ng/ml) (p = 0.001). Mean sC2C levels (220.83 ± 39.50 ng/ml) decreased post-race (188.67 ± 38.52 ng/ml) (p = 0.002). In contrast, means COMP, sCS846, sPIIANP, and median sYKL-40 were relatively stable. We found a positive association between sCK levels with sLDH pre-race (r = 0.758, p < 0.0001), post-race (r = 0.623, p = 0.008) and 48-h post-race (r = 0.842, p < 0.0001); sHA with sCRP post-race vs. 48 h post-race (r = 0.563, p = 0.019) and sPIINP with sCK pre-race vs. 48-h post-race (r = 0.499, p = 0.044) and with sLDH 48-h pre-race vs. post-race (r = 0.610, p = 0.009) and a negative correlation of sPIIANP with sCRP 48-h post-race (r = −0.570, p = 0.017).

Conclusion: Marathon running is an exercise with high-energy demands (sCK and sLDH increase) that provokes a high and durable general inflammatory reaction (sCRP increase) and an immediately post-marathon mechanism to protect inflammation and cartilage (sHA increase). Accompanied by an increase in type II collagen cartilage fibrils synthesis (sPIINP increase) and a decrease in its catabolism (sC2C decrease), without changes in non-collagenous cartilage metabolism (sCOMP, sC846, and sYKL-40). Metabolic changes on sPIINP and sHA synthesis may be related to energy consumption (sCK, sLDH) and the inflammatory reaction (sCRP) produced.

The potential remedy of melatonin on osteoarthritis

Osteoarthritis (OA), the most common arthritis worldwide, is a degenerative joint disease characterized by progressive cartilage breakdown, subchondral remodeling, and synovial inflammation. Although conventional pharmaceutical therapies aimed to prevent further cartilage loss and joint dysfunction, there are no ideal strategies that target the pathogenesis of OA. Melatonin exhibits a variety of regulatory properties by binding to specific receptors and downstream molecules and exerts a myriad of receptor-independent actions via intracellular targets as a chondrocyte protector, an anti-inflammation modulator, and a free radical scavenger. Melatonin also modulates cartilage regeneration and degradation by directly/indirectly regulating the expression of main circadian clock genes, such as transcriptional activators [brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein (Bmal) and circadian locomotor output cycles kaput (Clock)], transcriptional repressors [period circadian regulator (Per)1/2, cryptochrome (Cry)1/2, and Dec2], and nuclear hormone receptors [Rev-Erbs and retinoid acid-related orphan receptors (Rors)]. Owing to its effects on cartilage homeostasis, we propose a potential role for melatonin in the prevention and therapy of OA via the modulation of circadian clock genes, mitigation of chondrocyte apoptosis, anti-inflammatory activity, and scavenging of free radicals.

A matter of time: Circadian clocks in osteoarthritis and the potential of chronotherapy

Osteoarthritis (OA) is a common and debilitating joint disease which develops and progresses with age. Despite extensive research into the disease, potent disease-modifying drugs remain elusive. Changes to the character and function of chondrocytes of the articular cartilage underly the pathogenesis of OA. A recently emerging facet of chondrocyte biology that has been implicated in OA pathogenesis is the role of circadian rhythms, and the cellular clock which governs rhythmic gene transcription. Here, we review the role of the chondrocyte's cellular clock in governing normal homeostasis, and explore the wide range of consequences that contribute to OA development when the clock is dysregulated by aging and other factors. Finally, we explore how harnessing this understanding of clock mechanics in aging and OA can be translated into novel treatment strategies, or 'chronotherapies', for patients.

Immediate Biochemical Changes After Gait Biofeedback in Individuals With Anterior Cruciate Ligament Reconstruction

CONTEXT

Gait biomechanics are linked to biochemical changes that contribute to the development of posttraumatic knee osteoarthritis in individuals with anterior cruciate ligament reconstruction (ACLR). It remains unknown if modifying peak loading during gait using real-time biofeedback will result in acute biochemical changes related to cartilage metabolism.

OBJECTIVE

To determine if acutely manipulating peak vertical ground reaction force (vGRF) during gait influences acute changes in serum cartilage oligomeric matrix protein concentration (sCOMP) among individuals with ACLR.

DESIGN

Crossover study.

PATIENTS OR OTHER PARTICIPANTS

Thirty individuals with unilateral ACLR participated (70% female, age = 20.43 ± 2.91 years old, body mass index = 24.42 ± 4.25, months post-ACLR = 47.83 ± 26.97). Additionally, we identified a subgroup of participants who demonstrated an increase in sCOMP after the control or natural loading condition (sCOMPCHANGE > 0 ng/mL, n = 22, 70% female, age = 20.32 ± 3.00 years old, body mass index = 24.73 ± 4.33, months post-ACLR = 47.27 ± 29.32).

MAIN OUTCOME MEASURE(S)

Serum was collected both prior to and immediately after each condition to determine sCOMPchange.

INTERVENTION(S)

All participants attended 4 sessions that involved 20 minutes of walking on a force-measuring treadmill consisting of a control condition (natural loading) followed by random ordering of 3 loading conditions with real-time biofeedback: (1) symmetric vGRF between limbs, (2) a 5% increase in vGRF (high loading) and (3) a 5% decrease in vGRF (low loading). A general linear mixed model was used to determine differences in sCOMPCHANGE between altered loading conditions and the control group in the entire cohort and the subgroup.

RESULTS

The sCOMPCHANGE was not different across loading conditions for the entire cohort (F3,29 = 1.34, P = .282). Within the subgroup, sCOMPCHANGE was less during high loading (1.95 ± 24.22 ng/mL, t21 = -3.53, P = .005) and symmetric loading (9.93 ± 21.45 ng/mL, t21 = -2.86, P = .025) compared with the control condition (25.79 ± 21.40 ng/mL).

CONCLUSIONS

Increasing peak vGRF during gait decreased sCOMP in individuals with ACLR who naturally demonstrated an increase in sCOMP after 20 minutes of walking.

TRIAL REGISTRY

ClinicalTrials.gov (NCT03035994).

Deletion of clock gene Bmal1 impaired the chondrocyte function due to disruption of the HIF1α-VEGF signaling pathway

Several studies have demonstrated the core circadian rhythm gene Bmal1 could regulate the clock control genes (CCGs) expression and maintain the integrity in cartilage tissue. In addition, its abnormal expression is connected with the occurrence and development of several diseases including osteoarthritis (OA). However, the relationship between Bmal1 and cartilage development still needs to be fully elucidated. Here, we bred tamoxifen-induced cartilage-specific knockout mice to learn the effects of Bmal1 on the cartilage development and its underlying mechanisms at specific time points. We observed that Bmal1 ablated mice showed growth retardation during puberty, and the length of whole growth plate and the proliferation zone were both shorter than those in the control group. Deletion of Bmal1 significantly inhibited the chondrocytes proliferation and activated cells apoptosis in the growth plate. Meanwhile, knockout of Bmal1 attenuated the expression of VEGF and HIF1α and enhanced the level of MMP13 and Runx2 in the growth plate chondrocytes. Consistent with these findings in vivo, ablation of Bmal1 could also lead to decrease chondrocytes proliferation, the expression of HIF1α and VEGF and elevate apoptosis in cultured chondrocytes. These findings suggest that Bmal1 plays a pivotal role in cartilage development by regulating the HIF1α-VEGF signaling pathway.

The early diagnostic value of serum neopterin and cartilage oligomeric matrix protein for osteoarticular changes among brucellosis patients at an early period

Background

Brucellosis is an important public health problem in China. Brucellosis can cause many osteoarticular changes, especially chronic brucellosis. Brucellosis presents various diagnostic difficulties because it mimics many other diseases. Because of the poor sensitivity and ability of X-ray image, it is necessary to find a good method of early diagnosis for osteoarticular changes among brucellosis patients at an early period.

The aim of this study was to find early changes biomarkers for osteoarticular changes among brucellosis patients at an early period and provide a better understanding of the osteoarticular changes in this disease at an early stage.

Methods

Sixty-one cases of brucellosis patients at an early period (within 6 months) and 67 cases of volunteers were selected and divided into brucellosis vs. control groups. Serum samples were detected with serological tests for brucellosis, including rose bengal plate test (RBPT), agglutination test (SAT), and IgG and IgM with ELISA. Meanwhile, cartilage oligomeric matrix protein (COMP) and neopterin (NPT) levels in all samples were measured simultaneously with ELISA. The data were analyzed using SPSS 17.0 software.

Results

Together with the clinical examination, epidemiological investigation, and serological tests of RBPT, SAT, and IgG and IgM with ELISA, the patients from brucellosis group all were diagnosed as brucellosis cases at an early period, while the results of RBPT, SAT, and IgG and IgM with ELISA from the healthy control group were negative. Comparing with the healthy control, the medians of serum NPT and COMP in the patients group were 9.26 ng/l, 1.70 ng, respectively, which were higher than that of the healthy control group with significant differences (Z = 5.512, 3.614, all p = 0.000).

Conclusion

The serum NPT and COMP levels of brucellosis patients at an early period were increased. The serum NPT and COMP levels might be the indicator biomarker for osteoarticular changes of human brucellosis at an early stage.

Cartilage Oligomeric Matrix Protein Levels in Synovial Fluid in Patients With Primary Knee Osteoarthritis And Healthy Controls: A Preliminary Comparative Analysis With Serum Cartilage Oligomeric Matrix Protein

Objectives

This study aims (i) to compare synovial fluid and serum cartilage oligomeric matrix protein levels in patients with primary knee osteoarthritis and healthy controls, (ii) compare variations of synovial fluid and serum cartilage oligomeric matrix protein levels according to sex, Kellgren-Lawrence grades, and daytime sampling, and (iii) correlate the synovial fluid and serum cartilage oligomeric matrix protein levels with age, severity of disease, and daytime sampling.

Patients and methods

One hundred and twenty-four individuals (44 males, 80 females; median age 66 years; range 42 to 87 years) were diagnosed with primary knee osteoarthritis according to the American College of Rheumatology guidelines. Additionally, 105 healthy healthy individuals (49 males, 56 females; median age 50 years; range 30 to 75 years) were included as the control group. For both groups, a thorough clinical history and physical examination were performed. Moreover, weight-bearing anteroposterior and lateral bending 30 degrees knee X-rays were collected. Cartilage oligomeric matrix protein in serum and synovial fluid was measured by enzyme-linked immunosorbent assay.

Results

Total synovial fluid cartilage oligomeric matrix protein levels were considerably higher than total serum levels for both groups. Levels of cartilage oligomeric matrix protein in synovial fluid and serum were higher in patients than in controls for both sexes. However, only cartilage oligomeric matrix protein levels in synovial fluid were higher in female patients. The levels of synovial fluid cartilage oligomeric matrix protein were significantly higher when sampling after 12 pm. A positive correlation was found between synovial fluid and serum cartilage oligomeric matrix protein levels, age, and daytime sampling.

Conclusion

These findings may suggest a possible role for synovial fluid and serum cartilage oligomeric matrix protein as a measure for primary knee osteoarthritis. However, more studies need to be performed to address other factors that may influence the levels of cartilage oligomeric matrix protein in synovial fluid and serum.

A systemic review of existing serological possibilities to diagnose canine osteoarthritis with a particular focus on extracellular matrix proteoglycans and protein

Extra-cellular matrix (ECM) components are important and their stabilization is significant in maintaining normal healthy joint environment. In osteoarthritis (OA), ECM components are altered and indicate disease progression. The joint ECM is composed of proteoglycans (aggrecan, perlecan, inter α-trypsin inhibitor), glycoproteins (fibronectin, lubricin, COMP) and collagen types (most abundantly collagen type II) which represent structural and functional transformation during disease advancement. ECM investigation revealed significant biomarkers of OA that could be used as a diagnostic and therapeutic tool in different canine orthopedic diseases. This review deliberates our current findings of how the components of ECM change at the molecular level during disease progression in canine OA.

Circadian Clocks in Articular Cartilage and Bone

Temporally coordinated resorption and synthesis is the key to maintaining healthy bones. Articular cartilage is a highly specialized connective tissue within the joints that lines the surface of a long bone. Emerging evidence has suggested a critical role of the circadian system in controlling cartilage and bone biology. Articular cartilage is sparsely populated with chondrocytes, surrounded by abundant extracellular matrices that are synthesized and maintained solely by chondrocytes. Once damaged, the articular cartilage tissue has poor capacity for endogenous repair, leaving the joints prone to osteoarthritis, an age-related painful condition that affects millions of individuals worldwide. An important question is how articular cartilage has evolved its remarkable capacity to maintain homeostasis and withstand daily biomechanical challenges associated with resting/activity cycles. Equally important is how this avascular and aneural tissue senses time and uses this information to coordinate daily phases of metabolic activity and tissue remodeling/repair. Bone tissue derived from cartilage has similarly sparse populations of resident cells living in dense and largely mineralized matrices. We discuss recent progress on circadian clocks in these matrix-rich skeletal tissues and highlight avenues for future research.

Efficacy and tolerability of an undenatured type II collagen supplement in modulating knee osteoarthritis symptoms: a multicenter randomized, double-blind, placebo-controlled study

Background

Undenatured type II collagen (UC-II) is a nutritional supplement derived from chicken sternum cartilage. The purpose of this study was to evaluate the efficacy and tolerability of UC-II for knee osteoarthritis (OA) pain and associated symptoms compared to placebo and to glucosamine hydrochloride plus chondroitin sulfate (GC).

Methods

One hundred ninety one volunteers were randomized into three groups receiving a daily dose of UC-II (40 mg), GC (1500 mg G & 1200 mg C), or placebo for a 180-day period. The primary endpoint was the change in total Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) from baseline through day 180 for the UC-II group versus placebo and GC. Secondary endpoints included the Lequesne Functional Index (LFI), the Visual Analog Scale (VAS) for pain and the WOMAC subscales. Modified intent-to-treat analysis were performed for all endpoints using analysis of covariance and mixed model repeated measures, while incremental area under the curve was calculated by the intent-to-treat method.

Results

At day 180, the UC-II group demonstrated a significant reduction in overall WOMAC score compared to placebo (p = 0.002) and GC (p = 0.04). Supplementation with UC-II also resulted in significant changes for all three WOMAC subscales: pain (p = 0.0003 vs. placebo; p = 0.016 vs. GC); stiffness (p = 0.004 vs. placebo; p = 0.044 vs. GC); physical function (p = 0.007 vs. placebo). Safety outcomes did not differ among the groups.

Conclusion

UC-II improved knee joint symptoms in knee OA subjects and was well-tolerated. Additional studies that elucidate the mechanism for this supplement’s actions are warranted.

Trial registration

CTRI/2013/05/003663; CTRI/2013/02/003348.

Within-day variation and influence of physical exercise on circulating Galectin-3 in patients with rheumatoid arthritis and healthy individuals

Galectin-3 has been suggested as a pro-inflammatory mediator in rheumatoid arthritis (RA). Previous studies have reported overexpression of Galectin-3 in RA synovitis and increased levels in synovial fluid and serum in long-standing RA compared with osteoarthritis and healthy controls. Our objectives were to study whether serum Galectin-3 (1) exhibits circadian variation and/or (2) responds to exercise in RA and controls. The study on circadian patterns (1) comprised eleven patients with newly diagnosed RA, disease duration less than 6 months (ERA), 10 patients with long-standing RA [5-15 years (LRA)] and 16 self-reportedly healthy control subjects. During 24 h, 7 blood samples were drawn at 3-h intervals starting at 10 a.m. through 10 p.m. and at 7 and 10 a.m. on the following day. The study on the effect of physical activity (2) included 10 patients with ERA, 10 with LRA and 14 controls. The participants underwent a standardized exercise programme and four blood samples were drawn before, during and after exercise. Serum Galectin-3 was quantified by ELISA (R&D systems). (1) Galectin-3 was increased at baseline in both RA subsets (P = 0.08). There were no diurnal oscillations (P = 0.85). Day-to-day variation amounted to 3%. (2) Baseline Galectin-3 was increased in LRA versus controls and ERA (P < 0.01 and 0.05). Physical exercise induced 10-15% Galectin-3 increments in RA and controls (P < 0.001) peaking after 1-3 h. To conclude, Galectin-3 did not exhibit circadian variation. Day-to-day variation was 3%. Exercise elicited comparable increments in patients with RA of short and long duration and controls, approaching normal after 1-3 h.

Cartilage oligomeric matrix protein: a new promising biomarker of liver fibrosis in chronic hepatitis C

Cartilage oligomeric matrix protein (COMP) is a biomarker of fibrosis in lung and skin. In this exploratory study we investigated the biomarker potential of COMP in chronic hepatitis C (CHC). We included consecutive patients with CHC admitted to the Department of Infectious Diseases, Lund University Hospital. COMP was analysed in serum using ELISA. The correlations between COMP and liver fibrosis, determined by transient elastography (TE) (n = 47) and liver biopsy (n = 28) were assessed. We also studied COMP prospectively in relation to antiviral treatment (n = 10). COMP correlated with the degree of liver fibrosis as assessed by TE (r = 0.71, p < 0.001) and liver biopsy (rs = 0.65, p < 0.001). After successful treatment of CHC, COMP decreased from 18 to 13 U/l (p = 0.011). We suggest that COMP is associated with the stage of liver fibrosis in CHC. The biomarker potential of COMP in CHC warrants further investigation.

The Effects of Aerobic and Resistance Exercise on Markers of Large Joint Health in Stable Rheumatoid Arthritis Patients: A Pilot Study

OBJECTIVE

Exercise is beneficial for people with rheumatoid arthritis (RA). However, patients and health professionals have expressed concern about the possible detrimental effects of exercise on joint health. The present study investigated the acute and chronic effects of high-intensity, low-impact aerobic and resistance exercise on markers of large joint health in RA.

METHODS

Eight RA patients and eight healthy, matched control (CTL) participants performed 30 minutes' high-intensity, low-impact aerobic and lower-body resistance exercise, one week apart. Primary outcome measures assessing joint health were serum cartilage oligomeric matrix protein (sCOMP) and knee joint synovial inflammation (Doppler ultrasound colour fraction; CF). These measures were taken at baseline, immediately after and 0.5, one, two, six and 24 hours post-exercise. In a separate study, nine RA patients completed eight weeks of progressive exercise training. The same outcome measures were reassessed at baseline, and at one hour post-exercise of training weeks 0, 1, 4 and 8.

RESULTS

RA patients showed higher overall sCOMP [RA: 1,347 ± 421, CTL: 1,189 ± 562 ng/mL; p < 0.05; effect size (ES) = 0.32] and CF when scanned longitudinally (RA: 0.489 ± 0.30 × 10(-3) , CTL: 0.101 ± 0.13 × 10(-3) ; p < 0.01; ES = 1.73) and transversely (RA: 0.938 ± 0.69 × 10(-3) , CTL: 0.199 ± 0.36 × 10(-3) ; p < 0.01; ES = 1.33) than CTL. However, no acute effects on joint health were observed post-exercise. Similarly, no chronic effects were observed over eight weeks of combined aerobic and resistance training in RA, with positive effects on physical fitness and function.

CONCLUSIONS

RA patients on stable treatment with low disease activity were able to perform an individually prescribed high-intensity, low-impact aerobic and resistance exercise without changes in markers of large joint health. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of a 16 weeks weight loss program on osteoarthritis biomarkers in obese patients with knee osteoarthritis: a prospective cohort study

OBJECTIVE

Changes in biomarkers for bone and cartilage in knee osteoarthritis (KOA) may reflect changes in tissue turnover induced by interventions. The aim of this study was to assess the effect on osteoarthritis biomarkers of an intensive weight loss intervention in obese KOA patients.

METHODS

192 obese KOA patients followed a 16 weeks weight loss intervention (ClinicalTrials.gov: NCT00655941). Serum Cartilage Oligomeric Matrix Protein (sCOMP), Urine C-terminal telopeptide of collagen type II (uCTX-II) and type I (uCTX-I) were determined by enzyme-linked immunoassay (ELISA) at baseline and after 16 weeks. Patient-reported symptoms were assessed by the Knee Injury and Osteoarthritis Outcome Score (KOOS) Questionnaire without the sports and recreation score (KOOS-4). Change from baseline was analyzed using Analysis of CoVariance (ANCOVA) adjusting for sex, age, and body mass index (BMI). Bivariate associations were analyzed using Spearman's test of rank correlation.

RESULTS

175 patients completed the treatment and lost mean 13.4 (95% CI: 12.5-14.4) kg. sCOMP concentration decreased on average 1.1 (95% CI: -1.5 to -0.8) U/L with a correlation to weight loss (r = -0.17, P = 0.028), but not to change in KOOS-4 (r = -0.13, P = 0.091). uCTX-II increased significantly, mean 69 (95% CI: 31-106) ng/mmol creatinine, with no relation to weight loss (P = 0.14). Change in uCTX-II was reversely related to change in KOOS-4 (r = -0.28, P = 0.0003). uCTX-I increased, mean 67 (95% CI: 47-87) μg/mmol creatinine, and correlated to weight loss (r = 0.22, P = 0.0007), while not to KOOS-4 (P = 0.93).

CONCLUSION

A rapid substantial weight loss in obese KOA patients was weakly, while significantly associated with a reduction in sCOMP, and increases in both uCTX-II and uCTX-I.

Running on time: the role of circadian clocks in the musculoskeletal system

The night and day cycle governs the circadian (24 hourly) rhythm of activity and rest in animals and humans. This is reflected in daily changes of the global gene expression pattern and metabolism, but also in the local physiology of various tissues. A central clock in the brain co-ordinates the rhythmic locomotion behaviour, as well as synchronizing various local oscillators, such as those found in the musculoskeletal system. It has become increasingly recognized that the internal molecular clocks in cells allow a tissue to anticipate the rhythmic changes in their local environment and the specific demands of that tissue. Consequently, the majority of the rhythmic clock controlled genes and pathways are tissue specific. The concept of the tissue-specific function of circadian clocks is further supported by the diverse musculoskeletal phenotypes in mice with deletions or mutations of various core clock components, ranging from increased bone mass, dwarfism, arthropathy, reduced muscle strength and tendon calcification. The present review summarizes the current understanding of the circadian clocks in muscle, bone, cartilage and tendon tissues, with particular focus on the evidence of circadian rhythms in tissue physiology, their entrainment mechanisms and disease links, and the tissue-specific clock target genes/pathways. Research in this area holds strong potential to advance our understanding of how circadian rhythms control the health and disease of the musculoskeletal tissues, which has major implications in diseases associated with advancing age. It could also have potential implications in sports performance and sports medicine.

The future of blood-based biomarkers for Alzheimer's disease

Treatment of Alzheimer's disease (AD) is significantly hampered by the lack of easily accessible biomarkers that can detect disease presence and predict disease risk reliably. Fluid biomarkers of AD currently provide indications of disease stage; however, they are not robust predictors of disease progression or treatment response, and most are measured in cerebrospinal fluid, which limits their applicability. With these aspects in mind, the aim of this article is to underscore the concerted efforts of the Blood-Based Biomarker Interest Group, an international working group of experts in the field. The points addressed include: (1) the major challenges in the development of blood-based biomarkers of AD, including patient heterogeneity, inclusion of the "right" control population, and the blood-brain barrier; (2) the need for a clear definition of the purpose of the individual markers (e.g., prognostic, diagnostic, or monitoring therapeutic efficacy); (3) a critical evaluation of the ongoing biomarker approaches; and (4) highlighting the need for standardization of preanalytical variables and analytical methodologies used by the field.

Determination of the Interday and Intraday Reliability of Serum Cartilage Oligomeric Matrix Protein in a Physically Active Population

OBJECTIVE

To determine the intraday and interday reliability of serum cartilage oligomeric matrix protein (sCOMP) in a physically active population with no history of lower extremity surgery.

DESIGN

A repeated-measures reliability study was employed to determine the intraday and interday reliability of sCOMP in a physically active cohort. A total of 23 subjects were recruited to the laboratory on 3 separate occasions for nonfasting serum collection. Subjects had no history of lower extremity surgery and were free from acute injury within the last 3 months.

RESULTS

Our results indicate strong reliability for both intraday intraclass correlation coefficient (ICC) (0.76) and interday ICC (0.74) sCOMP values.

CONCLUSION

Our results demonstrate that following 30 minutes of inactivity, nonfasting serum samples remain stable over the course of 1 day and between 2 consecutive days in a healthy population with no history of lower extremity surgery. Future research studies are needed to further investigate the magnitude of change in this biomarker for patients with acute articular cartilage damage to determine its appropriateness for use in this population and for varying degrees of articular cartilage severity.

Osteoarthritis: an update with relevance for clinical practice

Osteoarthritis is thought to be the most prevalent chronic joint disease. The incidence of osteoarthritis is rising because of the ageing population and the epidemic of obesity. Pain and loss of function are the main clinical features that lead to treatment, including non-pharmacological, pharmacological, and surgical approaches. Clinicians recognise that the diagnosis of osteoarthritis is established late in the disease process, maybe too late to expect much help from disease-modifying drugs. Despite efforts over the past decades to develop markers of disease, still-imaging procedures and biochemical marker analyses need to be improved and possibly extended with more specific and sensitive methods to reliably describe disease processes, to diagnose the disease at an early stage, to classify patients according to their prognosis, and to follow the course of disease and treatment effectiveness. In the coming years, a better definition of osteoarthritis is expected by delineating different phenotypes of the disease. Treatment targeted more specifically at these phenotypes might lead to improved outcomes.

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 oligomeric matrix protein - inflammation biomarker in knee osteoarthritis

Chondrocytes and synovial cells synthesize Cartilage Oligomeric Matrix Protein (COMP) when activated by proinflammatory cytokines. The aim of this study was to analyze and compare ultrasound parameters of joint inflammation, effusion and synovitis with the levels of COMP in the serum of patients with primary osteoarthritis. Ultrasound was done and the concentration of COMP (ng/mL was examined in 88 patients. 75% of patients had effusion (size 10.13±4.35 mm), 62.5% had effusion in lateral recessus (LR), 28.4% (size 8.53±2.27 mm) in suprapatelar (SR), and 27.3% (size 11.38±4.44 mm) in medial (MR). 67% of patients had synovitis size 4.84±3.57 mm in SR, 3.15±1.86 mm in MR; and 6.09±2.80 mm in LR. 17.0% of patients had nodular type of synovitis, 30.7% had diffusive, and 19.3% nodular - diffusive. There was a significant link between the size of synovitis and effusion in SR (r = 0.966, p = 0.000), MR (r = 0.812, p = 0.009) and LR (r = 0.886, p = 0.003). The median of COMP concentration was 54 (44.5-58) ng/mL in patients without effusion. In those with effusion it was 57 (48.75-64.25) ng/mL (p = 0.030). Without synovitis it was 52 (45.5-58) ng/mL, with synovitis 58 (50-66) ng/mL, (p = 0.006), diffusion type synovitis 60 (50-67) ng/mL, nodular 57 (50-62) ng/mL, nodular-diffusion 54 (44.5-66.5) ng/mL (p = 0.014). With longer osteophytes the median of COMP was 56 (48-64) ng/mL, with shorter osteophytes 55 (46.5-59) ng/mL (p = 0.000). Cartilage oligomeric matrix protein has a moderate significance in the assessment of disturbance of the metabolism of synovial and cartilage tissue in patients with knee osteoarthritis (sensitivity = 59%; specificity = 50%; cut off = 53.5 ng/mL).

Exercise increases interleukin-10 levels both intraarticularly and peri-synovially in patients with knee osteoarthritis: a randomized controlled trial

Introduction

The microdialysis method was applied to the human knee joint with osteoarthritis (OA) in order to reveal changes in biochemical markers of cartilage and inflammation, intraarticularly and in the synovium, in response to a single bout of mechanical joint loading.

Methods

Thirty-one female subjects with OA of the knee were randomized to non-exercise (NEx) or exercise (Ex) groups. Following acute resistance exercise (25 sets of 10 repetitions at 60% of 1 Repetition Maximum) or none (NEx), peripheral nerve blocks just below the inguinal ligament were applied and two microdialysis catheters were positioned in two different compartments, intraarticularly and peri-synovially. The microdialysis catheters were perfused at a slow rate (2 μl/minute) with a solution of Ringer-acetate and radioactively labelled glucose allowing for determination of relative recovery (RR) and calculation of interstitial concentrations of inflammatory and cartilage biomarkers over a three-hour period.

Results

A significant increase of Interleukin (IL) -10 was discovered in both positions of the knee in the Ex group over the three hours post exercise, whereas IL-10 remained stationary over time in the NEx group. IL-6 and IL-8 displayed significant increases over time regardless of group and position of the catheter. Cartilage oligomeric matrix protein (COMP) decreased intraarticularly in the post exercise period in the Ex group compared to the NEx group.

Conclusions

Exercise caused an increase in both intraarticular and peri-synovial concentrations of IL-10 in a group of human females with knee OA. This suggests a positive effect of exercise on a chondroprotective anti-inflammatory cytokine response in patients with knee OA and might contribute to explaining the beneficial effect that exercise has on OA.

Trial registration

NCT01090375.

Serum and urinary biochemical markers for knee and hip-osteoarthritis: a systematic review applying the consensus BIPED criteria

CONTEXT

Molecules that are released into biological fluids during matrix metabolism of articular cartilage, subchondral bone, and synovial tissue could serve as biochemical markers of the process of osteoarthritis (OA). Unfortunately, actual breakthroughs in the biochemical OA marker field are limited so far.

OBJECTIVE

By reviewing the status of commercially available biochemical OA markers according to the "Burden of disease, Investigative, Prognostic, Efficacy of intervention, and Diagnostic" ("BIPED") classification, future use of this "BIPED" classification is encouraged and more efficient biochemical OA marker research stimulated.

DATA SOURCES

Three electronic databases [PubMed, Scopus, EMBASE (1997-May 2009)] were searched for publications on blood and urinary biochemical markers in human primary knee and hip-OA.

STUDY SELECTION

Stepwise selection of original English publications describing human studies on blood or urinary biochemical markers in primary knee or hip-OA was performed. Selected articles were fully read to determine whether biochemical markers were investigated on performance within any of the "BIPED" categories. Eighty-four relevant publications were identified.

DATA EXTRACTION

Data from relevant publications were tabulated according to the "BIPED" classification. Individual analyses within a publication were summarized in general "BIPED" scores.

DATA SYNTHESIS

An uneven distribution of scores on biochemical marker performance and heterogeneity among the publications complicated direct comparison of individual biochemical markers. Comparison of categories of biochemical markers was therefore performed instead. In general, biochemical markers of cartilage degradation were investigated most extensively and performed well in comparison with other categories of biochemical markers. Biochemical markers of bone metabolism performed less adequately. Biochemical markers of synovial tissue metabolism were not investigated extensively, but performed quite well.

CONCLUSIONS

Specific biochemical markers and categories of biochemical markers as well as their nature, origin and metabolism, need further investigation. International standardization of future investigations should be pursued to obtain more high-quality, homogenous data on the full spectrum of biochemical OA markers.

Circadian pattern and the effect of standardized physical exercise on procollagen IIA N-peptide (PIIANP) in rheumatoid arthritis at different stages and in healthy individuals

BACKGROUND

Variant collagen IIA is re-expressed in diseased cartilage. Low procollagen IIA N-peptide (PIIANP) levels in serum have recently been reported in rheumatoid arthritis (RA). We investigated circadian rhythmicity and effect of physical activity on PIIANP in early and longstanding RA and in healthy subjects.

METHODS

Patients with early and longstanding RA and controls were included. Fasting and serial blood samples were collected during 24 h. PIIANP response to physical activity was studied before and serially after standardized exercise.

RESULTS AND CONCLUSION

In RA at different stages and healthy individuals, PIIANP exhibited no circadian rhythmicity, and PIIANP in serum was not influenced by physical activity.

Glucosamine but not ibuprofen alters cartilage turnover in osteoarthritis patients in response to physical training

OBJECTIVE

To investigate changes in levels of serum cartilage oligomeric matrix protein (COMP) and urine c-telopeptide of type-2 collagen (CTX-II) as markers for cartilage turnover in patients with osteoarthritis (OA) of the knee, in response to muscle strength training in combination with treatment with glucosamine, ibuprofen or placebo.

DESIGN

A 12-week double blind, placebo controlled, randomized study.

METHOD

Thirty-six elderly patients with bilateral tibiofemoral knee OA determined by radiography were randomly assigned to treatment with glucosamine (n=12), ibuprofen (n=12) or placebo (n=12) during 12 weeks of strength training of both legs with focus on the quadriceps muscle. Strength tests (5 repetition maximum), blood and urine sampling were performed before and after the training period. Serum COMP and urinary CTX-II were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

All three groups increased their muscle strength following 12 weeks of strength training (P<0.001). Serum COMP levels were reduced in the glucosamine-treated group after the training period (P=0.012), whereas they did not change in the two other groups. Glucosamine reduced COMP statistically significant compared to both placebo and ibuprofen; the mean reduction with glucosamine was 13% vs placebo (P=0.0378) and 17% vs ibuprofen (P=0.0122). Urinary CTX-II levels did not change significantly in any of the three experimental groups.

CONCLUSION

Serum COMP decreased significantly over the 12-week training period when treatment with glucosamine was added to the training regimen. This suggests an effect by glucosamine on the response of the OA cartilage to a period of joint loading in humans with knee OA.

Change in serum COMP concentration due to ambulatory load is not related to knee OA status

The aim of this study was to test the hypothesis that a change in serum cartilage oligomeric matrix protein (COMP) concentration is related to joint load during a 30-min walking exercise in patients with medial compartment knee osteoarthritis (OA) and in age-matched control subjects. Blood samples were drawn from 42 patients with medial compartment knee OA and from 41 healthy age-matched control subjects immediately before, immediately after, and 0.5, 1.5, 3.5, and 5.5 h after a 30-min walking exercise on a level outdoor walking track at self-selected normal speed. Serum COMP concentrations were determined using a commercial ELISA. Basic time-distance gait variables were recorded using an activity monitor. Joint loads were measured using gait analysis. Serum COMP concentrations increased immediately after the walking exercise (+6.3% and +5.6%; p < 0.001) and decreased over 5.5 h after the exercise (-11.1% and -14.6%; p < 0.040 and p = 0.001) in patients and control subjects, respectively. The magnitude of increase in COMP concentration did not differ between groups (p = 0.902) and did not correlate with any variables describing ambulatory loads at the joints of the lower extremity. These results, taken together with a previous study of a younger healthy population, suggest the possibility that the influence of ambulatory loads on cartilage turnover is dependent on age.

The combination of the biomarkers urinary C-terminal telopeptide of type II collagen, serum cartilage oligomeric matrix protein, and serum chondroitin sulfate 846 reflects cartilage damage in hemophilic arthropathy

OBJECTIVE

Hemophilic arthropathy, with characteristics of inflammatory (rheumatoid arthritis) and degenerative (osteoarthritis) joint damage, occurs at an early age, is associated with minor comorbidity, and is restricted to 3 pairs of large joints. The aim of this study was to determine whether commonly used serum and/or urinary biomarkers of cartilage and bone turnover for which assay kits are commercially available are associated with the severity of joint damage in patients with various degrees of hemophilic arthropathy and, thus, whether this disease could be useful in the identification and evaluation of such biomarkers.

METHODS

Blood and urine samples were collected from 36 patients with various degrees of hemophilic arthropathy. Commercially available assays for the most frequently investigated serum and urine biomarkers were performed: urinary C-terminal telopeptide of type I collagen (CTX-I), urinary CTX-II, serum CTX-I, serum CTX-II, serum cartilage oligomeric matrix protein (COMP), serum cartilage cleavage products C1,2C and C2C, and serum chondroitin sulfate 846 (CS-846). Radiographs of the ankles, knees, and elbows in all patients were evaluated for the degree of joint damage according to the Pettersson score, which is based on cartilage and periarticular bone changes and is specific for hemophilic arthropathy.

RESULTS

Urinary CTX-II, serum C1,2C, and serum CS-846 levels correlated with the overall Pettersson score and with the joint space narrowing component. Regression analysis showed that combined indexes of different markers increased the degree of correlation for the combination of urinary CTX-II, serum COMP, and serum CS-846. Bone-specific markers (urinary/serum CTX-I and serum C1,2C) did not correlate with specific bone-related items of the Pettersson score (osteoporosis and erosions).

CONCLUSION

These results support the idea that a combination of biomarkers relates significantly better to the severity of joint damage than do individual biomarkers. The combination of urinary CTX-II, serum COMP, and serum CS-846 correlated best with the degree of arthropathy. Because of its specific characteristics and restricted involvement, hemophilic arthropathy may prove useful in the screening of newly developed biomarkers of joint damage.

Cartilage Oligomeric Matrix Protein (COMP): A Biomarker of Arthritis

Arthritis is a chronic disease with a significant impact on the population. It damages the cartilage, synovium, and bone of the joints causing pain, impairment, and disability in patients. Current methods for diagnosis of and monitoring the disease are only able to detect clinical manifestations of arthritis late in the process. However, with the recent onset of successful treatments for rheumatoid arthritis and osteoarthritis, it becomes important to identify prognostic factors that can predict the evolution of arthritis. This is especially critical in the early phases of disease so that these treatments can be started as soon as possible to slow down progression of the disease. A valuable approach to monitor arthritis would be by measuring biological markers of cartilage degradation and repair to reflect variations in joint remodeling. One such potential biological marker of arthritis is cartilage oligomeric matrix protein (COMP). In various studies, COMP has shown promise as a diagnostic and prognostic indicator and as a marker of the disease severity and the effect of treatment. This review highlights the progress in the utilization of COMP as a biomarker of arthritis.

The need for prognosticators in rheumatoid arthritis. Biological and clinical markers: where are we now?

Rheumatoid arthritis is a heterogeneous disease with respect to clinical manifestations, serologic abnormalities, joint damage and functional impairment. Predicting outcome in a reliable way to allow for strategic therapeutic decision-making as well as for prediction of the response to the various therapeutic modalities available today, especially biological agents, would provide means for optimization of care. In the present article, the current information on biological and clinical markers related to disease activity and joint damage as well as for predictive purposes is reviewed. It will be shown that the relationship of many biomarkers with disease characteristics is confounded by factors unrelated to the disease, and that only few biomarkers exist with some predictive value. Moreover, clinical markers appear of equal value as biomarkers for this purpose, although they likewise have limited capacity in these regards. The analysis suggests the search for better markers to predict outcomes and therapeutic responsiveness in rheumatoid arthritis needs to be intensified.

Giant-cell tumour of the knee: the condition of the cartilage after treatment by curettage and cementing

We reviewed nine patients at a mean period of 11 years (6 to 16) after curettage and cementing of a giant-cell tumour around the knee to determine if there were any long-term adverse effects on the cartilage. Plain radiography, MRI, delayed gadolinium-enhanced MRI of the cartilage and measurement of the serum level of cartilage oligomeric matrix protein were carried out. The functional outcome was evaluated using the Lysholm knee score. Each patient was physically active and had returned to their previous occupation. Most participated in recreational sports or exercise. The mean Lysholm knee score was 92 (83 to 100). Only one patient was found to have cartilage damage adjacent to the cement. This patient had a history of intra-articular fracture and local recurrence, leading to degenerative changes. Interpretation of the data obtained from delayed gadolinium-enhanced MRI of the cartilage was difficult, with variation in the T1 values which did not correlate with the clinical or radiological findings. We did not find it helpful in the early diagnosis of degeneration of cartilage. We also found no obvious correlation between the serum cartilage oligomeric matrix protein level and the radiological and MR findings, function, time after surgery and the age of the patient. In summary, we found no evidence that the long-term presence of cement close to the knee joint was associated with the development of degenerative osteoarthritis.

Cartilage Oligomeric Matrix Protein Level in Rheumatic Diseases: Potential Use as a Marker for Measuring Articular Cartilage Damage and/or the Therapeutic Efficacy of Treatments

Cartilage oligomeric matrix protein (COMP) is a tissue-specific noncollagenous protein that was first detected in the serum and the synovial fluid of patients suffering from rheumatic disorders, such as rheumatoid arthritis, reactive arthritis, juvenile chronic arthritis, and osteoarthritis. In this review, the authors consider serum COMP levels in different diseases and discuss their study of patients with rheumatoid arthritis treated with anti-TNF-alpha, to evaluate whether COMP is able to predict a rapid and sustained clinical response to these drugs. They observe that patients with high COMP levels have a lower ACR 70 response independently of the state of systemic inflammation, and conclude that COMP seems to have a pathogenetic role that is independent of the mechanisms regulating inflammatory processes.

Serum levels of cartilage oligomeric matrix protein (COMP) increase temporarily after physical exercise in patients with knee osteoarthritis

BACKGROUND

COMP (Cartilage oligomeric matrix protein) is a matrix protein, which is currently studied as a potential serum marker for cartilage processes in osteoarthritis (OA). The influence of physical exercise on serum COMP is not fully elucidated. The objective of the present study was to monitor serum levels of COMP during a randomised controlled trial of physical exercise vs. standardised rest in individuals with symptomatic and radiographic knee OA.

METHODS

Blood samples were collected from 58 individuals at predefined time points before and after exercise or rest, one training group and one control group. The physical exercise consisted of a one-hour supervised session twice a week and daily home exercises. In a second supplementary study 7 individuals were subjected to the same exercise program and sampling of blood was performed at fixed intervals before, immediately after, 30 and 60 minutes after the exercise session and then with 60 minutes interval for another five hours after exercise to monitor the short-term changes of serum COMP. COMP was quantified with a sandwich-ELISA (AnaMar Medical, Lund, Sweden).

RESULTS

Before exercise or rest no significant differences in COMP levels were seen between the groups. After 60 minutes exercise serum COMP levels increased (p < 0.001). After 60 minutes of rest the serum levels decreased (p = 0.003). Median serum COMP values in samples obtained prior to exercise or rest at baseline and after 24 weeks did not change between start and end of the study. In the second study serum COMP was increased immediately after exercise (p = 0.018) and had decreased to baseline levels after 30 minutes.

CONCLUSION

Serum COMP levels increased during exercise in individuals with knee OA, whereas levels decreased during rest. The increased serum COMP levels were normalized 30 minutes after exercise session, therefore we suggest that samples of blood for analysis of serum COMP should be drawn after at least 30 minutes rest in a seated position. No increase was seen after a six-week exercise program indicating that any effect of individualized supervised exercise on cartilage turnover is transient.