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

Cartilage oligomeric matrix protein as a potential biomarker for knee osteoarthritis

Aims

This study aimed to determine the expression and clinical significance of a cartilage protein, cartilage oligomeric matrix protein (COMP), in knee osteoarthritis (OA) patients.

Methods

A total of 270 knee OA patients and 93 healthy controls were recruited. COMP messenger RNA (mRNA) and protein levels in serum, synovial fluid, synovial tissue, and fibroblast-like synoviocytes (FLSs) of knee OA patients were determined using enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and immunohistochemistry.

Results

COMP protein levels were significantly elevated in serum and synovial fluid of knee OA patients, especially those in the advanced stages of the disease. Serum COMP was significantly correlated with radiological severity as well as measures of body composition, physical performance, knee pain, and disability. Receiver operating characteristic curve analysis unveiled a diagnostic value of serum COMP as a biomarker of knee OA (41.64 ng/ml, area under the curve (AUC) = 1.00), with a sensitivity of 99.6% and a specificity of 100.0%. Further analysis uncovered that COMP mRNA expression was markedly upregulated in the inflamed synovium of knee OA, consistent with immunohistochemical staining revealing localization of COMP protein in the lining and sub-lining layers of knee OA inflamed synovium. Most notably, relative COMP mRNA expression in knee OA synovium was positively associated with its protein levels in serum and synovial fluid of knee OA patients. In human knee OA FLSs activated with tumour necrosis factor-alpha, COMP mRNA expression was considerably up-regulated in a time-dependent manner.

Conclusion

All results indicate that COMP might serve as a supportive diagnostic marker for knee OA in conjunction with the standard diagnostic methods.

Associations between serum biomarkers of cartilage metabolism and serum hyaluronic acid, with risk factors, pain categories, and disease severity in knee osteoarthritis: a pilot study

BACKGROUND

Specific serum biomarkers of cartilage metabolism such as cartilage oligomeric matrix protein (sCOMP) and procollagen type II C-terminal propeptide (sPIICP) as well as hyaluronan (sHA), a biomarker of synovitis, have been implicated in the pathophysiology of knee osteoarthritis (OA). However, the associations of these biomarkers with the severity of the disease and OA risk factors, including age and obesity remain inconclusive. This analysis examines the associations between these serum biomarkers and the radiographic severity of OA and knee pain, as wells as obesity, the age and gender of the participants, and other OA risk factors.

METHODS

From 44 patients with early knee OA and 130 patients with late knee OA we analyzed the radiographic severity of the disease using the Kellgren and Lawrence (KL) grading system. Moreover, 38 overweight healthy individuals were used as a control group. Specific information was collected from all participants during their recruitment. The levels of the three serum biomarkers were quantified using commercially available ELISA kits. Serum biomarkers were analyzed for associations with the average KL scores and pain in both knees, as well as with specific OA risk factors.

RESULTS

The levels of sCOMP were elevated in patients with severe late OA and knee pain and correlated weakly with OA severity. A weakly correlation of sHA levels and OA severity OA was observed. We demonstrated that only sPIICP levels were markedly decreased in patients with late knee OA suggesting the alterations of cartilage metabolism in this arthritic disease. Moreover, we found that sPIICP has the strongest correlation with obesity and the severity of OA, as well as with the knee pain at rest and during walking regardless of the severity of the disease. ROC analysis showed that the area under the ROC curve (AUC) was 0.980 (95% CI: 0.945-0.995; p < 0.0001), suggesting high diagnostic accuracy of sPIICP. Interestingly, gender and age had also an effect on the levels of sPIICP.

CONCLUSION

This study revealed the potential of serum PIICP to be used as a biomarker to monitor the progression of knee OA, however, further studies are warranted to elucidate its clinical implication.

The synovium of human osteoarthritic joints retains its chondrogenic potential irrespective of age

The autologous synovium is a potential tissue source for local induction of chondrogenesis by tissue engineering approaches to repair articular cartilage defects such as they occur in osteoarthritis. It was the aim of the present study to ascertain whether the aging of human osteoarthritic patients compromises the chondrogenic potential of their knee-joint synovium and the structural and metabolic stability of the transformed tissue. The patients were allocated to one of the following two age categories: 54 - 65 years and 66 - 86 years (n = 7-11 donors per time point and experimental group; total number of donors: 64). Synovial biopsies were induced in vitro to undergo chondrogenesis by exposure to either bone morphogenetic protein-2 (BMP-2) alone, transforming growth factor-ß1 (TGF-ß1) alone, or a combination of the two growth factors, for up to 6 weeks. The differentiated explants were evaluated morphologically and morphometrically for the volume fraction of metachromasia (sulfated proteoglycans), immunohistochemically for type-II collagen, and for the gene-expression levels of anabolic chondrogenic markers as well as catabolic factors by a real-time polymerase-chain-reaction (RT-PCR) analysis. Quantitative metachromasia revealed that chondrogenic differentiation of human synovial explants was induced to the greatest degree by either BMP-2 alone or the BMP-2/TGF-1 combination, i.e. to a comparable level with each of the two stimulation protocols and within both age categories. The BMP-2/TGF-1combination protocol resulted in chondrocytes of a physiological size for normal human articular cartilage, unlike the BMP-2 alone stimulation that resulted in cell sizes of terminal hypertrophy. The stable gene-expression levels of the anabolic chondrogenic markers confirmed the superiority of these two stimulation protocols and demonstrated the hyaline-like qualities of the generated cartilage matrix. The gene-expression levels of the catabolic markers remained extremely low. The data also confirmed the usefulness of experimental in vitro studies with bovine synovial tissue as a paradigm for human synovial investigations. Our data reveal the chondrogenic potential of the human knee-joint synovium of osteoarthritic patients to be uncompromised by ageing and catabolic processes. The potential of synovium-based clinical engineering (repair) of cartilage tissue using autologous synovium may thus not be reduced by the age of the human patient.

Does moderate intensity impact exercise and non-impact exercise induce acute changes in collagen biochemical markers related to osteoarthritis? - An exploratory randomized cross-over trial

OBJECTIVE

To investigate acute changes in biochemical markers of cartilage turnover in response to moderate intensity exercise with and without joint impact in humans with knee osteoarthritis.

DESIGN

We conducted a randomized, cross-over, exploratory clinical study. Twenty subjects with knee osteoarthritis (OA) were randomized, of which twenty completed 30 min of cycling and 15 completed 30 min of running on days 1 week apart. Fasting blood samples were taken before, immediately after and 1, 2, 3, and 24 h after activity was initiated. Midstream spot urine was sampled before and after activity. Serum samples were analyzed for concentrations of fragment of type II collagen degradation, C2M, fragment of type VI collagen degradation, C6M, cartilage oligomeric matrix protein, COMP, marker of type II collagen formation, PRO-C2, and urine for marker of crosslinked type II collagen degradation, CTX-II. To establish a reference, all subjects had similar samples taken during rest on a separate day. Data was analyzed in a restricted maximum likelihood based random effects linear mixed model.

RESULTS

C2M trended to increase after cycling compared running (13.49%, 95%CI: -0.36-27.34%) and resting (12.88%, 95%CI: 0.2-25.6%) and the type II collagen formation/degradation ratio switched towards degradation after cycling, but not running. C6M trended to decrease after cycling (-8.1%, 95%CI: -14.8 to -1.4%) and running (-6.8%, 95%CI: -14.16-0.55%).

CONCLUSION

In persons with knee OA moderate intensity exercise without joint impact may induce acute changes in circulating levels of biochemical markers reflecting type II and VI collagen degradation.

Bone phenotypes in rheumatology - there is more to bone than just bone

Osteoarthritis, rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis, all have one clear common denominator; an altered turnover of bone. However, this may be more complex than a simple change in bone matrix and mineral turnover. While these diseases share a common tissue axis, their manifestations in the area of pathology are highly diverse, ranging from sclerosis to erosion of bone in different regions. The management of these diseases will benefit from a deeper understanding of the local versus systemic effects, the relation to the equilibrium of the bone balance (i.e., bone formation versus bone resorption), and the physiological and pathophysiological phenotypes of the cells involved (e.g., osteoblasts, osteoclasts, osteocytes and chondrocytes). For example, the process of endochondral bone formation in chondrocytes occurs exists during skeletal development and healthy conditions, but also in pathological conditions. This review focuses on the complex molecular and cellular taxonomy of bone in the context of rheumatological diseases that alter bone matrix composition and maintenance, giving rise to different bone turnover phenotypes, and how biomarkers (biochemical markers) can be applied to potentially describe specific bone phenotypic tissue profiles.

Identification of Diagnostic Biomarkers of Osteoarthritis Based on Multi-Chip Integrated Analysis and Machine Learning

The pathogenesis of osteoarthritis (OA) is still unclear. It is therefore important to identify relevant diagnostic marker genes for OA. We performed an integrated analysis with multiple microarray data cohorts to identify potential transcriptome markers of OA development. Further, to identify OA diagnostic markers, we established gene regulatory networks based on the protein-protein interaction network involved in these differentially expressed genes (DEGs). Using support vector machine (SVM) pattern recognition, a diagnostic model for OA prediction and prevention was established. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that 190 DEGs were mainly enriched in pathways like the tumor necrosis factor signaling pathway, interleukin-17 signaling pathway, mitogen-activated protein kinase signaling pathway, nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway, and osteoclast differentiation. Eight hub genes (POSTN, MMP2, CTSG, ELANE, COL3A1, MPO, COL1A1, and COL1A2) were considered potential diagnostic biomarkers for OA, the area under curve (AUC) was >0.95, which showed high accuracy. The sensitivity and specificity of the SVM model of OA based on these eight genes reached 100% in multiple external verification cohorts. Our research provides a theoretical basis for OA diagnosis for clinicians.

Serum Cartilage Oligomeric Matrix Protein in Late-Stage Osteoarthritis: Association with Clinical Features, Renal Function, and Cardiovascular Biomarkers

This study aimed to assess associations between serum cartilage oligomeric matrix protein (sCOMP) and phenotypic characteristics in late-stage hip and knee Osteoarthritis (OA) as well as its correlation with further serum markers of possible comorbidities in the Ulm Osteoarthritis Study. Moreover, the prognostic relevance of preoperative sCOMP concentrations for short-term functionality and pain outcomes after hip or knee joint replacement was explored. Preoperative serum samples and detailed information about the health status (i.e., WOMAC scores, Hannover Functionality Status (FFbH)) of 754 OA patients undergoing total joint replacement were included. Spearman rank-correlation coefficients and multiple linear regression models were used to evaluate the relationships between sCOMP, other serum markers, and health outcomes. There was a significant positive association between sCOMP and markers of renal (cystatin C, creatinine, and eGFR) and cardiac (e.g., NT-proBNP) impairment. Since renal failure might cause accumulation of sCOMP, additional adjustment with eGFR was performed. Preoperative sCOMP levels in knee OA but not hip OA patients were positively associated with FFbH, WOMAC function sub-scale and total WOMAC scale as well as the post-operative WOMAC stiffness sub-scale six months after surgery. Our data clearly demonstrate an association between sCOMP and renal function as well as other confounding factors, which should be considered in future biomarker studies.

Multifaceted Protective Role of Glucosamine against Osteoarthritis: Review of Its Molecular Mechanisms

Osteoarthritis (OA) is a joint disease resulting from cartilage degeneration and causing joint pain and stiffness. Glucosamine exerts chondroprotective effects and effectively reduces OA pain and stiffness. This review aims to summarise the mechanism of glucosamine in protecting joint health and preventing OA by conducting a literature search on original articles. Current evidence has revealed that glucosamine exhibits anti-inflammatory effects by reducing the levels of pro-inflammatory factors (such as tumour necrosis factor-alpha, interleukin-1, and interleukin-6) and enhancing the synthesis of proteoglycans that retard cartilage degradation and improve joint function. Additionally, glucosamine improves cellular redox status, reduces OA-mediated oxidative damages, scavenges free radicals, upregulates antioxidant proteins and enzyme levels, inhibits the production of reactive oxygen species, and induces autophagy to delay OA pathogenesis. In conclusion, glucosamine prevents OA and maintains joint health by reducing inflammation, improving the redox status, and inducing autophagy in joints. Further studies are warranted to determine the synergistic effect of glucosamine with other anti-inflammatory and/or antioxidative agents on joint health in humans.

Cartilage oligomeric matrix protein, C-terminal cross-linking telopeptide of type II collagen, and matrix metalloproteinase-3 as biomarkers for knee and hip osteoarthritis (OA) diagnosis: a systematic review and meta-analysis

OBJECTIVE

This study was design to examine the diagnostic performance of cartilage oligomeric matrix protein (COMP), C-terminal cross-linking telopeptide of type II collagen (CTX-II), and matrix metalloproteinase-3 (MMP-3) as biomarker for knee and hip OA.

METHODS

Systematic search on multiple databases was completed in January 2018 using certain keywords. COMP, CTX-II, MMP-3 levels in knee and hip OA patients and healthy individuals were collected and calculated. Differences between subgroups were expressed as standardized mean differences (SMD). Subgroup analyses were performed to compare COMP, CTX-II, and MMP-3 performance between measuring sources, genders, large and small sample size and diagnostic criteria for OA patients.

RESULTS

A moderate performance of COMP in distinguishing between knee (SMD: 0.68; 95% confidence intervals (CI): 0.43-0.93; P < 0.0001) or hip (SMD: 0.25; 95% CI, 0.10, 0.40; P = 0.0008) OA patients and controls were found. CTX-II showed a moderated standardised mean differences (SMD) of 0.48 (95% CI, 0.32, 0.64; P < 0.0001) in the detection of knee OA and a large SMD of 0.76 (95% CI, 0.09, 1.42; P = 0.03) in diagnosing hip OA. A small SMD of 0.32 (95% CI, -0.03, 0.67; P = 0.07) was found for MMP-3 performance and the results did not reach statistic significance. Progression study revealed potential effectiveness of serum COMP in predicting OA progression. Subgroup analysis showed that serum COMP and urinary CTX-II performed better in male than female. Study size and diagnostic criteria did not significantly influence the pooled SMD, but they might be the sources of heterogeneity among studies.

CONCLUSION

The overall results indicates that serum COMP and urinary CTX-II can distinguish between knee or hip OA patients and control subjects. Serum COMP is effective in predicting OA progression.Further researches with rigorous study design and a larger sample size are required to validate our findings.

Serum cartilage oligomeric matrix protein (COMP) expression in individuals who sustained a youth sport-related intra-articular knee injury 3-10 years previously and uninjured matched controls

OBJECTIVE

This study investigates the relationship between a youth sport-related intra-articular knee injury and cartilage oligomeric matrix protein (COMP), a biomarker of cartilage turnover.

DESIGN

Participants included a sub-sample (n = 170) of the Alberta Youth Prevention of Early Osteoarthritis (PrE-OA) study group. Specifically, 85 individuals with a 3-10 year history of sport-related intra-articular knee injury and 85 age, sex and sport-matched controls. COMP levels were investigated in serum. Between group differences in COMP levels, COMP fragmentation patterns and, the relationship between serum COMP and clinical outcomes (i.e., Magnetic Resonance Imaging (MRI) Osteoarthritis Knee Score; MOAKS, Knee Osteoarthritis Outcome Score; KOOS, Fat mass index; FMI) were examined.

RESULTS

Participant median age was 22.3 years (range 16-26) and 63% were female. Although there was no difference in COMP levels between previously injured and uninjured females, previously injured males demonstrated an ∼15% greater (171.5 ng/ml, 95% CI 11.0-428.0, P = 0.04) serum COMP level than uninjured males. However after controlling for FMI, this difference was absent. Within the injured participants, COMP levels were associated with MOAKS_SYNOVITIS and FMI. Furthermore, COMP fragmentation patterns were distinct between injured and uninjured individuals.

CONCLUSIONS

In this study group, serum COMP levels were greater in injured males, but not females, compared to matched controls. However, after controlling for FMI, no differences in COMP were observed. A unique COMP fragmentation pattern was observed in injured vs uninjured participants. These results further the hypothesis that COMP levels and/or degradation of the protein may be a marker of cartilage injury which could predispose to later OA.

Biochemical Markers for the Early Identification of Osteoarthritis: Systematic Review and Meta-Analysis

BACKGROUND

There is a desperate need for the reliable detection of osteoarthritis (OA) at the early stage when patients are likely to benefit most from disease interventions. A variety of biochemical markers have been proposed, but their reliability varies among studies.

OBJECTIVE

In this review, we aimed to answer the following questions: (1) are there biochemical markers that are differentially expressed in early OA versus healthy subjects, and (2) if so, what is the diagnostic value of these biomarkers for early OA?

METHODS

Embase, PubMed, and Web of Science were searched to obtain all relevant studies up to March 2018, and studies comparing the biochemical markers between early OA and healthy controls were selected. The Downs and Black checklist was used to assess the risk of bias. Biomarkers that were investigated in five or more different populations were pooled for meta-analysis. A meta-regression analysis was performed to explore possible explanations for the heterogeneity of studies.

RESULT

In total, 26 articles met the criteria for the qualitative synthesis and 17 articles for the final quantitative synthesis. N-terminal crosslinked telopeptide of type I collagen (NTX-I) was the only biomarker found to be differently expressed in patients with early OA versus controls, without significant heterogeneity among studies (I2 = 0%, [Formula: see text] = 1.695, p = 0.792). The meta-regression analysis identified that sample size and affected joint possibly explained the heterogeneity among studies.

CONCLUSION

Although a wide range of biomarkers has been previously investigated in early OA, the diagnostic value of these biomarkers could not be determined because due to a low number of studies regarding any given biomarker. Large prospective and adequately powered studies are therefore required to validate these (and other) biomarkers for identifying early OA.

Correlation of serum cartilage oligomeric matrix protein with knee osteoarthritis diagnosis: a meta-analysis

BACKGROUND

The measurement of cartilage oligomeric matrix protein (COMP) has become a novel way for the diagnosis of knee osteoarthritis (OA). However, no conclusive correlation has been drawn between COMP and knee OA. The purpose of this study was to examine the utility of serum COMP as biomarker for knee OA and its relation with disease severity.

METHODS

A systematic search on PubMed, ScienceDirect, and EMBASE was conducted in January 2018 using certain keywords. Initial search yielded a total of 285 publications, and 35 articles were reviewed in full-text. Eventually, nine studies were included in the analysis. All the retrieved studies used Kellgren-Lawrence (K-L) classification for knee OA and provided available data of serum COMP in OA patients and healthy controls. Sensitivity analysis was performed by removing one study result at a time to detect the impact of each study have on the overall effect and to test the stability of the cumulative result. Subgroup study based on K-L grade system was also conducted to disclose the correlation between serum COMP and knee OA disease severity.

RESULTS

Pooled analysis of nine studies demonstrated a significant elevation of serum COMP in knee OA patients (SMD 0.81, [95% CI, 0.36, 1.25], P = 0.0004) compared with controls. In comparisons between K-L 1-4 and controls, significantly higher serum COMP was detected in all three subgroups except K-L grade 1 versus control. Comparisons among K-L grades 1-4 revealed significantly higher serum COMP levels in patients with more serious than less serious disease stage. However, the elevation in patients with K-L grade 3 did not reach statistical significance when compared with K-L grade 1 patients.

CONCLUSION

The overall analysis showed significantly higher serum COMP in knee OA patients compared to controls which indicate the potential ability of serum COMP in differentiating knee OA patients from healthy subjects. Pooled statistic of our meta-analysis showed that serum COMP levels were effective in distinguishing patients with K-L ≥ 2.

Combined detection of COMP and CS846 biomarkers in experimental rat osteoarthritis: a potential approach for assessment and diagnosis of osteoarthritis

Background

To comprehensively evaluate the diagnostic value of serum cartilage oligomeric matrix protein (COMP) and chondroitin sulfate 846 epitope (CS846) biomarkers in osteoarthritis (OA), longitudinal and combined measurement of serum COMP and CS846 were performed at different stages in the pathological process of OA in a rat model of anterior cruciate ligament transection (ACLT).

Methods

Sixty male Sprague-Dawley rats were randomly divided into two groups, including a model group (n = 30) and a control group (n = 30). Rat models were established by ACLT surgery, and sham operations were performed on rats in the control group. Prior to surgery and at 2, 4, 6, 8, and 10 weeks after ACLT surgery, serum levels of COMP and CS846 biomarkers were determined using an enzyme-linked immunosorbent assay approach. Five rats per group were euthanized at 2, 4, 6, 8, and 10 weeks after surgery, after which tibial plateau specimens were collected. Macroscopic observation and histological examination were employed for rat tibial plateau. Histological changes in articular cartilage were evaluated according to Osteoarthritis Research Society International (OARSI) scoring criteria. The area under the curve (AUC) of COMP, CS846, and combined biomarkers was compared using receiver operating characteristic (ROC) curve.

Results

Within 10 weeks after surgery, serum levels of COMP and CS846 in the model group were significantly higher when compared to those in the control group. Moreover, a significant correlation was observed between changes in COMP and CS846 levels. At each time point, macroscopic observations and OARSI scores were significantly increased in the development of OA. The AUC of combined biomarkers was higher compared to that of COMP and CS846 alone. Finally, a positive relationship was found between levels of COMP and CS846 and the OARSI score.

Conclusions

In this study, we found that combined detection of serum CS846 and COMP levels can be used for diagnosis and monitoring of OA progression.

Meta-analysis of serum C-reactive protein and cartilage oligomeric matrix protein levels as biomarkers for clinical knee osteoarthritis

Background

The roles of C-reactive protein (CRP) and cartilage oligomeric matrix protein (COMP) in knee osteoarthritis (KOA) remain controversial, thus the present study is aimed to explore the relationships between CRP, COMP, and the incidence/progression of KOA.

Methods

A systematic search was conducted on PubMed and Embase until September, 2016 for all the relevant studies. The pooled mean difference (MD) with its 95% confidence interval (95% CI) based on fixed effects model or random effects model was calculated to assess the potential role of CRP and COMP in the incidence or progression of KOA. Heterogeneity was evaluated by Cochran’s Q and I² tests. When P < 0.05 or I² > 50%, a random effects model was chosen, otherwise, a fixed effects model was used. Moreover, the role of CRP in different degrees of pain was also analyzed. Sensitivity analysis was performed to evaluate the strength of the meta-analysis.

Results

Fourteen studies were enrolled in the meta-analysis. No difference was found between baseline CRP and CRP levels in the last follow-up period of KOA (MD = − 0.09, 95% CI: -0.30, 0.13). Pooled data showed higher CRP concentration in patients with incident KOA when compared with controls (MD = 0.33, 95% CI: 0.04, 0.63). Moreover, higher serum COMP levels were found in patients with incident KOA (MD = 1.69, 95% CI: 0.61, 2.76) Additionally, significant higher CRP concentration was observed in KOA patients with highest degree of pain (MD = 1.60, 95% CI: 0.52, 2.67).

Conclusion

CRP and COMP serum levels were both associated with the incidence of KOA. Patients with a higher CRP and COMP concentration might have an increased probability of developing KOA. However, higher CRP serum levels was not related with KOA progression. Furthermore, KOA patients with more pain had higher CRP concentrations.

Review of Prospects of Biological Fluid Biomarkers in Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of the joints and is one of the leading causes of disability in adults. However, there are no key therapeutics for OA and medical treatment is based on managing the symptoms and slowing down progression of the disease. Diagnostics based on clinical examination and radiography have provided little information about metabolic changes in joint tissues, disease onset and progression. Due to lack of effective methods for early detection and evaluation of treatment outcome, the measurement of biochemical markers (biomarkers) shows promise as a prospective method aiding in disease monitoring. OA biomarkers that are present in biological fluids such as blood, urine and synovial fluid, sources that are easily isolated from body, are of particular interest. Moreover, there are increasingly more studies identifying and developing new biomarkers for OA. In this review, efforts have been made to summarize the biomarkers that have been reported in recent studies on patients. We also tried to classify biomarkers according to tissue metabolism (bone, cartilage and synovial metabolism markers), pathological pathways (inflammatory and genetic markers) and biological function (chemokines, growth factors, acute phase proteins, etc.).

Combined detection of serum CTX-II and COMP concentrations in osteoarthritis model rabbits: an effective technique for early diagnosis and estimation of disease severity

Background

Early diagnosis of osteoarthritis (OA) is difficult. Cartilage oligomeric matrix protein (COMP) and crosslinked C-telopeptides of type II collagen (CTX-II) are two markers which can potentially predict the destruction of articular cartilage of early OA. To comprehensively evaluate the diagnosis value of serum COMP and CTX-II markers in OA, the longitudinal and combined measurement of serum COMP and CTX-II were performed at different stages of pathological process of OA in adult rabbits with OA, compared with the sham-operated rabbits.

Methods

Thirty-six adult white rabbits were randomly divided into two groups, the OA group and the control group (n = 18 per group). OA models were established by anterior cruciate ligament transection. Sham operations were performed in the control group. Before the surgery and at weeks 2, 4, 6, 8, 10, and 12 after surgery, serum CTX-II and COMP concentrations were detected using sandwich-ELISA in all rabbits. Three rabbits in each group were killed at weeks 2, 4, 6, 8, 10, and 12 after surgery, and femoral condyle specimens were collected. Histological changes in articular cartilage were evaluated according to the Mankin scoring criteria.

Results

At each time point, the Mankin scores and serum concentrations of CTX-II and COMP were significantly higher in the OA group than in the control group. In addition, in the OA group, there was a significant relationship between the CTX-II and COMP concentrations and the Mankin score.

Conclusions

Early dynamic combined detection of serum CTX-II and COMP concentrations is effective for early OA diagnosis and evaluation of OA severity.

Serum cartilage oligomeric matrix protein and development of radiographic and painful knee osteoarthritis. A community-based cohort of middle-aged women

CONTEXT AND OBJECTIVE

We evaluated the predictive value of serum cartilage oligomeric matrix protein (sCOMP) levels over 20 years on the development of radiographic (RKOA) and painful knee osteoarthritis (KOA) in a longitudinal cohort of middle-aged women.

MATERIALS AND METHODS

Five hundred and ninety-three women with no baseline KOA underwent 5-year knee radiographs over 20-years and were asked about knee pain a month before each assessment. A repeated measures logistic regression model was used where the outcomes were recorded at 5, 10, 15 and 20-years follow-up.

RESULTS

The highest quartile of sCOMP was associated with increased risk of RKOA with overall OR of 1.97 (95% CI: 1.33-2.91) over 20 years when compared with the lowest sCOMP quartile. The association with painful KOA was similar and also independent, but only when the fourth and third sCOMP quartiles were compared.

DISCUSSION AND CONCLUSION

This study demonstrates that sCOMP levels are predictive of subsequent structural changes and incidence of painful KOA, independently of age and BMI.

Inflammatory biomarkers in osteoarthritis

Osteoarthritis (OA) is highly prevalent and a leading cause of disability worldwide. Despite the global burden of OA, diagnostic tests and treatments for the molecular or early subclinical stages are still not available for clinical use. In recent years, there has been a large shift in the understanding of OA as a "wear and tear" disease to an inflammatory disease. This has been demonstrated through various studies using MRI, ultrasound, histochemistry, and biomarkers. It would of great value to be able to readily identify subclinical and/or sub-acute inflammation, particularly in such a way as to be appropriate for a clinical setting. Here we review several types of biomarkers associated with OA in human studies that point to a role of inflammation in OA.

Mechanotransduction pathways in bone pathobiology

The skeleton is subject to dynamic changes throughout life and bone remodeling is essential for maintenance of bone functionality. The cell populations which predominantly participate in bone and cartilage remodeling, namely osteocytes, osteoblasts, osteoclasts and chondrocytes sense and respond to external mechanical signals and via a series of molecular cascades control bone metabolism and turnover rate. The aforementioned process, known as mechanotransduction, is the underlying mechanism that controls bone homeostasis and function. A wide array of cross-talking signaling pathways has been found to play an important role in the preservation of bone and cartilage tissue health. Moreover, alterations in bone mechanotransduction pathways, due to genetic, hormonal and biomechanical factors, are considered responsible for the pathogenesis of bone and cartilage diseases. Extensive research has been conducted and demonstrated that aberrations in mechanotransduction pathways result in disease-like effects, however only few signaling pathways have actually been engaged in the development of bone disease. The aim of the present review is to present these signaling molecules and cascades that have been found to be mechano-responsive and implicated in bone disease development, as revealed by research in the last five years. In addition, the role of these molecules as prognostic or diagnostic disease markers and their potential as therapeutic targets are also discussed.

Analysis on the serum levels of the biomarker CTX-II in professional indoor soccer players over the course of one season

Objective

The aim of this study was to analyze the blood serum levels of CTX-II in professional indoor soccer players, at three different times during one season: at the start of the pre-season, four months later (a time that marks the middle of the season) and at the end of the season.

Methods

Fourteen male soccer players of mean age 19 years were included. Blood samples of 3 mL were collected from each individual. The samples were analyzed by means of Elisa tests.

Results

There was a significant increase in the serum level of CTX-II in the indoor soccer players, from the beginning to the end of the season (p < 0.01).

Conclusion

These data suggest that joint degradation had occurred in these soccer players, by the end of this period. It is evident that further studies are needed, with methodological rigor, so as to make an effective contribution toward precise elucidation of the etiology of this osteoarthritis and its relationship with the biomarkers, as a tool for early diagnosis.

Serum Cartilage Oligomeric Matrix Protein Levels in Collegiate Soccer Athletes over the Duration of an Athletic Season: A Pilot Study

OBJECTIVE

The primary objective of this study was to measure serum cartilage oligomeric matrix protein (sCOMP) levels weekly in a group of collegiate soccer athletes over the duration of a spring soccer season and 2 weeks following the conclusion of the season while documenting minutes of exercise participation as a measure of exercise intensity.

DESIGN

A repeated-measures study design was employed. A volunteer sample of 6 female soccer athletes participated in this study. Serum samples were collected on 10 separate occasions, 1 week prior to the start of the season (baseline), once a week during the 8-week season (PX1-PX8), and once a week for 2 weeks following the conclusion of the season (postseason; PS1 and PS2). Minutes of participation were documented following all spring soccer activities for each week. Once all samples were collected, sCOMP concentrations were determined using a commercially available enzyme-linked immunosorbent assay.

RESULTS

The results of Friedman test revealed a significant effect for time (P = 0.003). Post hoc analysis revealed no significant differences between baseline and practice or postseason levels. A qualitative analysis of the sCOMP levels and minutes indicated higher sCOMP levels occurred when the athletes' participation in soccer-related activities was higher.

CONCLUSIONS

Qualitatively, our findings suggest that as minutes of participation increased, sCOMP levels increased. However, no statistically significant differences were identified. We speculate these increases were an increase in cartilage turnover and an interesting observation related to increases in physical activity. However, the implications are unclear as there was a return to near baseline levels.

Biomarkers of cartilage and surrounding joint tissue

The identification and clinical demonstration of efficacy and safety of osteo- and chondro-protective drugs are met with certain difficulties. During the last few decades, the pharmaceutical industry has, in the field of rheumatology, experienced disappointments associated with the development of disease modification. Today, the vast amount of patients suffering from serious, chronic joint diseases can only be offered treatments aimed at improving symptoms, such as pain and acute inflammation, and are not aimed at protecting the joint tissue. This huge, unmet medical need has been the driver behind the development of improved analytical techniques allowing better and more efficient clinical trial design, implementation and analysis. With this review, we aim to provide a brief and general overview of biochemical markers of joint tissue, with special focus on neoepitopes. Furthermore, we highlight recent studies applying biochemical markers in joint degenerative diseases. These disorders, including osteoarthritis, rheumatoid arthritis and spondyloarthropathies, are the most predominant disorders in Europe and the USA, and have enormous socioeconomical impact.

Longitudinal documentation of serum cartilage oligomeric matrix protein and patient-reported outcomes in collegiate soccer athletes over the course of an athletic season

BACKGROUND

Serum cartilage oligomeric matrix protein (sCOMP) is a biomarker for cartilage degradation. Patient-reported outcomes (PRO) are used to document postinjury recovery and may be used to prospectively identify changes in the course of a season. It is unknown what effect intense, continuous physical activity has on sCOMP levels and PRO values in athletes over the duration of a soccer season. Hypothesis/

PURPOSE

The purpose of this study was to longitudinally document sCOMP levels and to determine whether changes in PROs occur in collegiate soccer athletes during a season. The hypotheses tested were that sCOMP levels and PRO scores would remain stable over the duration of the spring soccer season.

STUDY DESIGN

Case series; level of evidence, 4.

METHODS

Twenty-nine National Collegiate Athletic Association Division-I soccer athletes (18 men, 11 women; age, 19.6 ± 1.2 years; height, 177.8 ± 7.4 cm; mass, 73.8 ± 10.2 kg) participated in 3 (pre-[T(1)], mid-[T(2)], and postseason [T(3)]) data collection sessions. Subjects were included if they were participants in the spring soccer season and were free of severe knee injury at the time of data collection. At each session, subjects completed PROs (Lysholm, International Knee Documentation Committee scores) before serum collection.

RESULTS

For sCOMP (ng/mL), there was a significant effect for time, with significant increases at T(2) (1723.5 ± 257.9, P < .001) and T(3) (1624.7 ± 231.6, P = .002) when compared with T(1)(1482.9 ± 217.9). For each of the PROs, there was a significant effect for time from T(1)-T(3), and at T(2)-T(3) for the IKDC.

CONCLUSION

These data indicate sCOMP levels increased as athletes reported an increased level of function over time. However, the differences in sCOMP levels did not reach the calculated minimal detectable change (MDC) value and the differences in PRO scores did not reach previously calculated MDC values. It is unclear whether these increases in sCOMP levels were caused by an increase in cartilage matrix breakdown or turnover. Even though these elevations may not be clinically meaningful, this biomarker may have the potential to be used for future research studies investigating the effects of exercise on overall joint health in longitudinal studies. In addition, these results indicate fluctuations in sCOMP occur during a competitive season and must be taken into consideration for future biomarker studies.

A relationship between mechanically-induced changes in serum cartilage oligomeric matrix protein (COMP) and changes in cartilage thickness after 5 years

OBJECTIVE

To evaluate the hypothesis that a mechanical stimulus (30-min walk) will produce a change in serum concentrations of cartilage oligomeric matrix protein (COMP) that is associated with cartilage thickness changes on magnetic resonance imaging (MRI).

METHODS

Serum COMP concentrations were measured by enzyme-linked immunosorbent assay in 17 patients (11 females, age: 59.0±9.2 years) with medial compartment knee osteoarthritis (OA) at study entry immediately before, immediately after, 3.5 h, and 5.5 h after a 30-min walking activity. Cartilage thickness changes in the medial femur and medial tibia were determined from MR images taken at study entry and at 5-year follow-up. Relationships between changes in cartilage thickness and COMP levels, with post-activity concentrations expressed as a percentage of pre-activity levels, were assessed by the calculation of Pearson correlation coefficients and by multiple linear regression analysis, with adjustments for age, sex, and body mass index (BMI).

RESULTS

Changes in COMP levels 3.5 h and 5.5 h post-activity were correlated with changes in cartilage thickness in the medial femur and tibia at the 5-year follow-up. The results were strengthened after analyses were adjusted for age, sex, and BMI. Neither baseline pre-activity COMP levels nor changes in COMP levels immediately post-activity were correlated with cartilage thickness changes.

CONCLUSIONS

The results of this study support the hypothesis that a change in COMP concentration induced by a mechanical stimulus is associated with cartilage thinning at 5 years. Mechanically-induced changes in mechano-sensitive biomarkers should be further explored in the context of stimulus-response models to improve the ability to assess OA progression.

Serum cartilage oligomeric matrix protein (sCOMP) is elevated in patients with knee osteoarthritis: a systematic review and meta-analysis

OBJECTIVE

To be used in diagnostic studies, it must be demonstrated that biomarkers can differentiate between diseased and non-diseased patients. Therefore, the purpose of this study was to answer the following questions: (1) Is serum cartilage oligomeric matrix protein (sCOMP) elevated in patients with radiographically diagnosed knee osteoarthritis (OA) compared to controls? (2) Are there differences in sCOMP levels when comparing differing radiographic OA severities to controls?

METHODS

Systematic review and meta-analysis.

DATA SOURCES

A systematic search of CINAHL, PEDro, Medline, and SportsDiscus was completed in March 2010.

KEYWORDS

knee, osteoarthritis, sCOMP, radiography. Study inclusion criteria: Studies were written in English, compared healthy adults with knee OA patients, used the Kellgren Lawrence (K/L) classification, measured sCOMP, and reported means and standard deviations for sCOMP.

RESULTS

For question 1, seven studies were included resulting in seven comparisons. A moderate overall effect size (ES) indicated sCOMP was consistently elevated in those with radiographically diagnosed knee OA when compared to controls (ES = 0.60, P < 0.001). For question 2, four studies were included resulting in 13 comparisons between radiographic OA severity levels and controls. Strong ESs were calculated for K/L-1 (ES = 1.43, P = 0.28), K/L-3 (ES = 1.05, P = 0.04), and K/L-4 (ES = 1.40, P = 0.003). A moderate ES was calculated for K/L-2 (ES = 0.60, P = 0.01).

CONCLUSIONS

These results indicate sCOMP is elevated in patients with knee OA and is sensitive to OA disease progression. Future research studies with a higher level of evidence should be conducted to investigate the use of this biomarker as an indicator for OA development and progression.

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.

Pain perception in knees with circumscribed cartilage lesions is associated with intra-articular IGF-1 expression

BACKGROUND

Circumscribed cartilage defects are considered as prearthritic lesions and lead to differential intra-articular cytokine expression. Mechanisms of associated pain development and influence of smoking behavior are not yet fully understood in humans.

PURPOSE

This study aimed to reveal relations between synovial cytokine levels in knees with circumscribed cartilage defects and pain sensation.

STUDY DESIGN

Descriptive laboratory study.

METHODS

In a clinical trial, knee lavage fluids of 42 patients with circumscribed cartilage lesions treated by either microfracturing (n = 19) or by autologous chondrocyte implantation (n = 23) and fluids of 5 healthy control individuals were prospectively collected. Preoperative knee pain was evaluated according to frequency and strength; subjective knee function was assessed using a visual analog scale and the International Knee Documentation Committee (IKDC) score. Synovial concentrations of aggrecan, insulin-like growth factor (IGF)-I, basic fibroblast growth factor (bFGF), interleukin (IL)-1β, bone morphogenetic protein (BMP)-2, and BMP-7 were determined by enzyme-linked immunosorbent assay.

RESULTS

Pain strength showed a highly significant association with intra-articular IGF-1 levels (ρ = .48, P < .01), but no correlation with synovial concentrations of aggrecan, bFGF, IL-1β, BMP-2, and BMP-7. Although pain strength and frequency demonstrated a statistically significant relationship, no substantial association between pain frequency and any of the examined cytokine levels was found. Intra-articular IGF-1 concentrations significantly correlated with the area of cartilage damage (ρ = .35, P < .02); the other investigated cytokines failed to show this association. Neither of the determined intra-articular mediators demonstrated statistically significant correlations with subjective knee function or IKDC score. Only intra-articular concentrations of IGF-1 and BMP-2 statistically significantly correlated with age; total protein content was negatively associated with body mass index (P < .05). In smokers, synovial expression of total protein content, IGF-1, and bFGF was significantly diminished compared to nonsmokers (P < .05).

CONCLUSION

Insulin-like growth factor-I is present in knees with circumscribed cartilage lesions in a size-dependent manner. IGF-1 levels correlated with indicators of pain perception; smoking negatively influenced synovial cytokine expression related to cartilage metabolism, but pain perception was not altered.

Longitudinal changes of serum COMP and urinary CTX-II predict X-ray defined knee osteoarthritis severity and stiffness in women

OBJECTIVE

To ascertain the predictive role of longitudinally acquired biochemical measures of cartilage turnover in relation to X-ray defined knee osteoarthritis (OAK), knee pain and functioning.

METHODS

This is a feasibility study based on 72 enrollees of the Michigan site of Study of Women's Health Across the Nation (SWAN), a longitudinal, population-based cohort study with 11 annual visits to characterize health at the mid-life. At visits in 1996, 1998 and 2007, radiographs were evaluated for the presence of OAK [>or=2 on the Kellgren and Lawrence (K-L) scale]. Knee pain and stiffness were assessed by interview. Functioning was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Cartilage oligomeric matrix protein (COMP) and Type II collagen telopeptides (CTX-II) were assayed in serum and urine samples collected on alternate years from 1997 to 2006. We related trajectories of the cartilage biochemical markers from these five time points to OAK severity (no OAK, K-L score<2; mild OAK, K-L score=2; moderate/severe OAK, K-L score=3 or 4), pain, stiffness, or functioning, using longitudinal non-linear mixed modeling.

RESULTS

The 2007 prevalence of X-ray defined OAK was 50% in these 72 women. Upward trajectories of COMP (P=0.02) and CTX-II (P=0.006) were associated with increased OAK severity and body size. COMP trajectories were associated with pain and stiffness, but not functioning. CTX-II trajectories were associated with stiffness scores, but not knee pain or functioning scores.

CONCLUSION

Multiple, biennial measures of COMP or CTX-II taken over a 10-year period were predictive of subsequent OAK and knee stiffness.

Rhein, the metabolite of diacerhein, reduces the proliferation of osteoarthritic chondrocytes and synoviocytes without inducing apoptosis

OBJECTIVE

The aim of this study was to determine the effects of pharmacologically relevant concentrations of rhein (1,8-dihydroxy-3-carboxyanthraquinone) on the cell proliferation rate of human chondrocytes and synoviocytes.

METHODS

Cultures of human osteoarthritic synoviocytes and chondrocytes were incubated with 10(-6), 10(-5), and 10(-4) M rhein. [3H]thymidine incorporation was used to determine rhein proliferative effects after incubation periods of 24 h, 48 h, and 1 week. The cytotoxicity of the drug was assayed with a nonradioactive assay kit. Nuclear extracts were used to detect variations in cell-cycle proteins (p21, p27, and cyclin D1) by Western blotting. The effect of rhein on apoptosis was investigated by measurement of caspase-3/7 activity and DNA fragmentation.

RESULTS

Rhein was found to downregulate the proliferation rate of both chondrocytes and synoviocytes, two-fold for 10(-5) M rhein and five- to six-fold for 10(-4) M rhein. No cytotoxicity of the drug was observed. Rhein (10(-4) M) decreased caspase-3/7 activity and did not induce DNA fragmentation. Western blots showed that 10(-4) M rhein increased the expression of p21 and/or p27, but not that of cyclin D1.

CONCLUSIONS

Rhein has previously been shown to reduce the interleukin (IL)-1beta deleterious effects on osteoarthritis (OA) cartilage through inhibition of the expression of degrading enzymes. Here, rhein was also found to inhibit proliferation of both synoviocytes and chondrocytes, suggesting that the drug may decrease the development of the inflammatory synovial tissue that accompanies joint pathologies. Both its anti-catabolic and anti-proliferative effects may explain its beneficial effect in the treatment of joint diseases.

Biomarkers in the development of novel disease-modifying therapies for osteoarthritis

Identification and utilization of biomarkers is vitally important for the successful development of disease-modifying osteoarthritis drugs. Biochemical and imaging platforms hold great promise to deliver such biomarkers. Studies indicate a marked increase in biochemical products arising from the breakdown and biosynthesis of collagen, extracellular matrix and bone in osteoarthritis. These molecules have been associated with disease severity and may also have prognostic value as indicators of disease progression. However, issues including biological variability and lack of tissue specificity currently hinder the utility of these molecular markers in drug development. Imaging technologies hold great potential for sensitive and accurate measurement of disease-related structural damage. Drawbacks, including expense, need for validation and limited accessibility also limit the utility of these technologies. In this article, the potential value and challenges in developing and utilizing biomarkers in disease-modifying osteoarthritis drug development will be discussed.

Mechanical and biochemical characterization of cartilage explants in serum-free culture

Allografts of articular cartilage are both used clinically for tissue-transplantation procedures and experimentally as model systems to study the physiological behavior of chondrocytes in their native extracellular matrix. Long-term maintenance of allograft tissue is challenging. Chemical mediators in poorly defined culture media can stimulate cells to quickly degrade their surrounding extracellular matrix. This is particularly true of juvenile cartilage which is generally more responsive to chemical stimuli than mature tissue. By carefully modulating the culture media, however, it may be possible to preserve allograft tissue over the long-term while maintaining its original mechanical and biochemical properties. In this study juvenile bovine cartilage explants (both chondral and osteochondral) were cultured in both chemically defined medium and serum-supplemented medium for up to 6 weeks. The mechanical properties and biochemical content of explants cultured in chemically defined medium were enhanced after 2 weeks in culture and thereafter remained stable with no loss of cell viability. In contrast, the mechanical properties of explants in serum-supplemented medium were degraded by ( approximately 70%) along with a concurrent loss of biochemical content (30-40% GAG). These results suggest that long-term maintenance of allografts can be extended significantly by the use of a chemically defined medium.