Association of plasma and synovial fluid interferon-γ inducible protein-10 with radiographic severity in knee osteoarthritis

A tool for evaluating novel osteoarthritis therapies using multivariate analyses of human cartilage-synovium explant co-culture

OBJECTIVE

There is a need to incorporate multiple tissues into in vitro OA models to evaluate novel therapeutics. This approach is limited by inherent donor variability. We present an optimized research tool: a human OA cartilage-synovium explant co-culture model (OA-EXM) that employs donor-matched lower and upper limit response controls combined with statistical approaches to address variability. Multiple rapid read-outs allow for evaluation of therapeutics while cataloguing cartilage-synovium interactions.

DESIGN

48-h human explant cultures were sourced from OA knee arthroplasties. An OA-like cartilage-synovium co-culture baseline was established relative to donor-matched upper limit supraphysiological pro-inflammatory cytokine and lower limit OA cartilage or synovium alone controls. 100 nM dexamethasone treatment validated possible "rescue effects" within the OA-EXM dual tissue environment. Gene expression, proteoglycan loss, MMP activity, and soluble protein concentrations were analyzed using blocking and clustering methods.

RESULTS

The OA-EXM demonstrates the value of the co-culture approach as the addition of OA synovium increases OA cartilage proteoglycan loss and expression of MMP1, MMP3, MMP13, CXCL8, CCL2, IL6, and PTGS2, but not to the extent of supraphysiological stimulation. Conversely, OA cartilage does not affect gene expression or MMP activity of OA synovium. Dexamethasone shows dual treatment effects on synovium (pro-resolving macrophage upregulation, protease downregulation) and cartilage (pro-inflammatory, catabolic, and anabolic downregulation), and decreases soluble CCL2 levels in co-culture, thereby validating OA-EXM utility.

CONCLUSIONS

The OA-EXM is representative of late-stage OA pathology, captures dual interactions between cartilage and synovium, and combined with statistical strategies provides a rapid, sensitive research tool for evaluating OA therapeutics.

Synovial Fluid Biomarkers in Knee Osteoarthritis: A Systematic Review and Quantitative Evaluation Using BIPEDs Criteria

OBJECTIVE

The aim of this systematic review was to analyze the evidence about the efficacy of the several synovial fluid (SF) biomarkers proposed for knee osteoarthritis (OA), categorizing them by both molecular characteristics and clinical use according to the BIPEDs criteria, to provide a comprehensive and structured overview of the current literature.

DESIGN

A systematic review was performed in May 2020 on PubMed, Cochrane Library, and Embase databases about SF biomarkers in patients with knee OA. The search was limited to articles in the last 20 years on human studies, involving patients with knee OA, reporting SF biomarkers. The evidence for each selected SF biomarker was quantified according to the 6 categories of BIPEDs classification.

RESULTS

A total of 159 articles were included in the qualitative data synthesis and 201 different SF biomarkers were identified. Among these, several were investigated multiple times in different articles, for a total of 373 analyses. The studies included 13,557 patients with knee OA. The most promising SF biomarkers were C4S, IL-6, IL-8, Leptin, MMP-1/3, TIMP-1, TNF-α, and VEGF. The "burden of disease" and "diagnostic" categories were the most represented with 132 and 106 different biomarkers, respectively.

CONCLUSIONS

The systematic review identified numerous SF biomarkers. However, despite the high number of studies on the plethora of identified molecules, the evidence about the efficacy of each biomarker is supported by limited and often conflicting findings. Further research efforts are needed to improve the understanding of SF biomarkers for a better management of patients with knee OA.

Soluble biological markers in osteoarthritis

In recent years, markers research has focused on the structural components of cartilage matrix. Specifically, a second generation of degradation markers has been developed against type II collagen neoepitopes generated by specific enzymes. A particular effort has been made to measure the degradation of minor collagens III and X of the cartilage matrix. However, because clinical data, including longitudinal controlled studies, are very scarce, it remains unclear whether they will be useful as an alternative to or in combination with current more established collagen biological markers to assess patients with osteoarthritis (OA). In addition, new approaches using high-throughput technologies allowed to detect new types of markers and improve the knowledge about the metabolic changes linked to OA. The relative advances coming from phenotype research are a first attempt to classify the heterogeneity of OA, and several markers could improve the phenotype characterization. These phenotypes could improve the selection of patients in clinical trials limiting the size of the studies by selecting patients with OA characteristics corresponding to the metabolic pathway targeted by the molecules evaluated. In addition, the inclusion of rapid progressors only in clinical trials would facilitate the demonstration of efficacy of the investigative drug to reduce joint degradation. The combination of selective biochemical markers appears as a promising and cost-effective approach to fulfill this unmet clinical need. Among the various potential roles of biomarkers in OA, their ability to monitor drug efficacy is probably one of the most important, in association with clinical and imaging parameters. Biochemical markers have the unique property to detect changes in joint tissue metabolism within a few weeks.

Correlation between serum pro inflammatory cytokines and clinical scores of knee osteoarthritic patients using resveratrol as a supplementary therapy with meloxicam

OBJECTIVE:

The objective of this study was to analyze the associations between the pro-inflammatory markers with the clinical outcomes of knee osteoarthritis (OA) in patients using resveratrol as an add-on treatment with meloxicam.

MATERIALS AND METHODS:

This was a double-blind controlled clinical investigation, with 110 eligible patients with OA assigned randomly to receive 15 mg a day meloxicam with either resveratrol 500 mg a day or placebo for 90 days. The standard tools for assessment of pain severity and physical functions were utilized. The tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 in the blood were evaluated. Spearman's correlation coefficient test was used to determine the significance of correlations.

RESULTS:

The regression analysis to determine the correlation between reductions of the inflammatory biomarkers with the amelioration of the clinical scores showed a nonsignificant weak correlation between these variables. Total clinical scores of each assessment tool that was used “Knee Injury and OA Outcome Score (KOOS) and WOMAC” displayed a weak and nonsignificant correlation with TNF-α, IL-1β blood level. The Spearman's correlation shows a relatively nonsignificant association between IL-6 levels and KOOS, WOMAC, and Visual Analog Scale scores after incorporating resveratrol as an adjuvant with meloxicam for 90 days.

CONCLUSION:

A weak and nonsignificant correlation between serum biomarkers and the clinical outcomes has been suggested in patients with painful knee OA treated with meloxicam and resveratrol.

Serum Inflammatory Markers in Patients With Knee Osteoarthritis: A Proteomic Approach

OBJECTIVES

Osteoarthritis (OA) is known to be a slowly progressive disease that alters all tissue compartments of the joint involved with a characteristic degradation of the cartilage, bone remodeling, and inflammation. One of the prominent symptoms in OA patients is pain, but a few radiologic, inflammatory, or structurally related biomarkers have shown few if any associations with pain. This study aimed to assess serum levels of 92 markers involved in inflammatory pathways in patients with knee osteoarthritis (KOA) and evaluate their possible associations with the clinical pain intensity.

MATERIALS AND METHODS

Serum samples were collected from 127 KOA patients and 39 healthy participants with no knee pain. Each serum sample was analyzed for 92 inflammatory markers using the Proximity Extension Array (PEA) technology. Clinical pain intensity was assessed using a Visual Analog Scale, and patients completed the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire.

RESULTS

Fifteen markers were significantly different when comparing KOA patients and healthy participants. Two markers, fibroblast growth factor-21 and Eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), correlated positively with pain intensity (R=0.235, P=0.008; R=0.233, P=0.008). Moreover, a linear regression model showed interleukin-6, macrophage colony-stimulating factor 1, fibroblast growth factor-21, and tumor necrosis factor superfamily member 12 (TWEAK) as significant independent parameters for pain intensity.

DISCUSSION

The associations between specific cytokines and KOA pain intensities provide new insights into the understanding of the underlying factors driving the pain in OA.

A Pilot Clinical Study of Hyperacute Serum Treatment in Osteoarthritic Knee Joint: Cytokine Changes and Clinical Effects

The serum fraction of platelet-rich fibrin (hyperacute serum) has been shown to improve cartilage cell proliferation in in vitro osteoarthritic knee joint models. We hypothesize that hyperacute serum may be a potential regenerative therapeutic for osteoarthritic knees. In this study, the cytokine milieu at the synovial fluid of osteoarthritic knee joints exposed to hyperacute serum intraarticular injections was investigated. Patients with knee osteoarthritis received three injections of autologous hyperacute serum; synovial fluid was harvested before each injection and clinical monitoring was followed-up for 6 months. Forty osteoarthritic-related cytokines, growth factors and structural proteins from synovial fluid were quantified and analysed by Multivariate Factor Analysis. Hyperacute serum provided symptomatic relief regarding pain and joint stability for OA patients. Both patients "with" and "without effusion knees" had improved VAS, KOOS and Lysholm-Tegner scores 6 months after of hyperacute serum treatment. Synovial fluid analysis revealed two main clusters of proteins reacting together as a group, showing strong and significant correlations with their fluctuation patterns after hyperacute serum treatment. In conclusion, hyperacute serum has a positive effect in alleviating symptoms of osteoarthritic knees. Moreover, identified protein clusters may allow the prediction of protein expression, reducing the number of investigated proteins in future studies.

Deciphering the Association of Cytokines, Chemokines, and Growth Factors in Chondrogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells Using an ex vivo Osteochondral Culture System

Osteoarthritis (OA) is a chronic degenerative joint disorder associated with degradation and decreased production of the extracellular matrix, eventually leading to cartilage destruction. Limited chondrocyte turnover, structural damage, and prevailing inflammatory milieu prevent efficient cartilage repair and restoration of joint function. In the present study, we evaluated the role of secreted cytokines, chemokines, and growth factors present in the culture supernatant obtained from an ex vivo osteochondral model of cartilage differentiation using cartilage pellets (CP), bone marrow stem cells (BM-MSCs), and/or BM-MSCs + CP. Multiplex cytokine analysis showed differential secretion of growth factors (G-CSF, GM-CSF, HGF, EGF, VEGF); chemokines (MCP-1, MIP1α, MIP1β, RANTES, Eotaxin, IP-10), pro-inflammatory cytokines (IL-1β, IL-2, IL-5, IL-6, IL-8, TNFα, IL-12, IL-15, IL-17) and anti-inflammatory cytokines (IL-4, IL-10, and IL-13) in the experimental groups compared to the control. In silico analyses of the role of stem cells and CP in relation to the expression of various molecules, canonical pathways and hierarchical cluster patterns were deduced using the Ingenuity Pathway Analysis (IPA) software (Qiagen, United States). The interactions of the cytokines, chemokines, and growth factors that are involved in the cartilage differentiation showed that stem cells, when used together with CP, bring about a favorable cell signaling that supports cartilage differentiation and additionally helps to attenuate inflammatory cytokines and further downstream disease-associated pro-inflammatory pathways. Hence, the autologous or allogeneic stem cells and local cartilage tissues may be used for efficient cartilage differentiation and the management of OA.

Osteoarthritis-related biomarkers profile in chronic anterior cruciate ligament injured knee

OBJECTIVE

Increasing evidence has shown the involvement of the innate immune system and inflammatory response in osteoarthritis (OA) pathogenesis; however, anterior cruciate ligament (ACL) tears are recognized risk factors for development of post-traumatic OA. We investigated (1) whether inflammatory mediators involved in OA pathogenesis are also present at significant concentrations in the knee joint sometime after ACL complete tear and may be considered as prognostic biomarkers of progression to secondary OA; and (2) whether quantification in serum may surrogate synovial fluid (SF) measurements in both cases.

METHODS

Thirty-seven end-stage OA patients and 33 patients with ACL complete tear that were included on the waiting list for knee surgery were consecutively recruited. Serum and SF samples were taken before surgery, and tumor necrosis factor-alpha, (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), matrix metalloproteinase-1 (MMP1), matrix metalloproteinase-3 (MMP3), tissue inhibitor of metalloproteinase-1 (TIMP1), bone morphogenetic protein-7 (BMP7), regulated upon activation normal t-cell expressed and secreted (RANTES), cytokine interferon-γ-induced protein 10 (IP-10) and heat shock protein family A (Hsp70) member 1A (HSPA1A) were quantified by enzyme-linked immunosorbent assay (ELISA.) Normally distributed data were compared using a one-way analysis of variance (ANOVA) test. Data not normally distributed were analyzed using a nonparametric Mann-Whitney rank sum test. Differences in means were compared using a Student's t-test. Correlations were analyzed using Pearson's coefficient of variation.

RESULTS

Eighty-seven percent of patients with OA and 86% of those with ACL tear had quantifiable levels of biomarkers in SF. SF levels of IL-6, IL-8, MMP1, MMP3, RANTES, IP-10, BMP7 and HSPA1A were significantly lower in ACL injury knees compared with those with OA, but much higher than those reported in control subjects. Serum levels of IL-6, IP-10, and MMP1 were also lower in patients with ACL tears, who had, however, significantly higher TNF-α, HSPA1A, and TIMP1 levels when compared with OA patients. Levels of biomarkers tested in serum and SF samples were significantly different.

CONCLUSIONS

Our data propose that cytokines IL-6 and IL-8 and the chemokines RANTES, IP-10, MMP1, MMP3, and HSPA1A may be involved in the inflammatory process leading to synovitis, the central lesion in OA onset and development; persistent high levels of these substances sometime after ACL injury suggest that they could play an etiopathogenic role in the maintenance of the inflammatory environment leading to post-traumatic OA. Serum biomarker levels do not appear to faithfully reflect what occurs inside the joint. Thus, most biomarkers cannot yet be considered as useful inflammatory biomarkers of knee joint diseases.

Association of CCL13 levels in serum and synovial fluid with the radiographic severity of knee osteoarthritis

OBJECTIVE

CCL13, a recently identified CC chemokine, plays an important role in the process of joint destruction, which is considered a common cause for osteoarthritis (OA). This study aims to examine the relation of CCL13 levels in serum and synovial fluid (SF) with the radiographic severity of OA.

METHODS

CCL13 levels in serum and SF were evaluated using enzyme-linked immunosorbent assay method in 240 patients with knee OA and 134 control subjects. The progression of OA was classified using the Kellgren-Lawrence (KL) system by evaluating x-ray changes observed in anteroposterior knee radiography.

RESULTS

Knee OA patients had higher levels of serum CCL13 compared with control subjects. Knee OA patients with KL grade 4 showed significantly elevated CCL13 levels in serum and SF compared with those with KL grades 2 and 3. Knee OA patients with KL grade 3 had significantly higher SF levels of CCL13 compared with those with KL grade 2. CCL13 levels in serum and SF of knee OA patients were significantly correlated with disease severity evaluated by KL grading criteria.

CONCLUSIONS

CCL13 levels in serum and SF were correlated with the radiographic severity of OA. CCL13 levels in serum and SF may serve as a biomarker for the progression of OA.

Plasma and Synovial Fluid CXCL12 Levels Are Correlated With Disease Severity in Patients With Knee Osteoarthritis

BACKGROUND

The aim is to determine whether CXC chemokine ligand-12 (CXCL12) levels in plasma and synovial fluid (SF) of patients with knee osteoarthritis (OA) are correlated with the disease severity. In addition, we set out to investigate whether a peripheral blood test can avoid aspirating patients to determine CXCL12 levels.

METHODS

This study consisted of 244 patients with knee OA and 244 age- and gender-matched healthy controls. Osteoarthritis progression was classified based on Kellgren-Lawrence (KL) by evaluating radiographic changes observed in anteroposterior knee radiography. The CXCL12 levels in the plasma and SF were measured by a quantitative sandwich enzyme-linked immunosorbent assay.

RESULTS

Plasma CXCL12 levels were higher in OA patients as compared with controls (P < .0001). There was a positive correlation between levels of CXCL12 and grade (P < .0001). Base on the receiver operating characteristic curve, the optimal cutoff value of plasma CXCL12 levels as an indicator for screening of OA was estimated to be 5.5 ng/mL, which yielded a sensitivity of 78.4% and a specificity of 80.2%, with the area under the curve at 0.850 (95% confidence interval [CI], 0.816-0.889; P < .0001). In multivariate analysis, there was an increased risk of active OA associated with plasma CXCL12 levels ≥10.5 ng/mL (odds ratio, 6.76; 95% CI, 3.88-12.53; P < .0001) after adjusting for possible confounders. Similarly, there was an increased risk of active OA associated with SF CXCL12 levels ≥15.0 ng/mL (odds ratio, 8.45; 95% CI, 3.23-18.22; P < .0001) after adjusting for possible confounders.

CONCLUSION

The CXCL12 levels in the plasma and SF may serve as effective biomarkers for the severity of OA.

Possible role of granulysin in pathogenesis of osteoarthritis

Increased presence of immune mediator and cytotoxic/apoptotic molecule granulysin was noticed in different tissues during pathological processes with the domination of Th1 over Th2 mediated immunity. Beside granulysin expression in T and NKT cells, activated NK cells are thought to be the major source of chemotactic 15 kDa and cytotoxic 9 kDa granulysin in vivo. As NK cells are the principal joint's tissue-infiltrating lymphocyte subset, we hypothesized that granulysin mediated human cell death (apoptosis) could be responsible for the relatively silent damage of the joint's tissue without clinically notable signs of systemic inflammation in the patients with osteoarthritis (OA). The analyzes of the presence and frequency of granulysin expressing lymphocytes at protein and gene levels in peripheral blood and synovial samples and/or the samples of joint's tissue after the joint replacement therapy in patients with OA could give the initial insight to evaluate our hypothesis. It would be of the particular interest to differentiate the expression of 9 kDa and 15 kDa granulysin forms in the effector cells, since only the shorter form exhibits cytotoxic properties. The measurement of granulysin mediated early apoptosis in human NK sensitive K562 cells could be suitable in vitro model for evaluating granulysin activity. Furthermore, disturbed balance of pro-inflammatory and anti-inflammatory cytokines in OA patients, could influence the level of the granulysin expression. Having in mind that the granulysin and its regulation is still unknown in the pathogenesis of OA, it could be worth to explore this important pro-inflammatory, cytotoxic/apoptotic mediator.

Serum and synovial fluid levels of CCL18 are correlated with radiographic grading of knee osteoarthritis

Background

Chemokines are involved in the pathogenesis of osteoarthritis (OA). CCL18, a member of the chemokines family, is observed in synovial fluid (SF) of OA patients. The aim of this study was to determine the association between CCL18 levels in serum and SF with radiographic knee OA.

Material/Methods

This study was conducted in a population of 308 patients with knee OA. The radiological knee OA was graded by the Kellgren-Lawrence grading system.

Results

Serum levels of CCL18 in knee OA patients were markedly higher than those in healthy controls. Serum and SF levels of CCL18 increased with the severity of KL grades and were correlated with disease severity.

Conclusions

The CCL18 levels in serum and SF are correlated with the severity of OA.

Serum levels of proinflammatory cytokines in painful knee osteoarthritis and sensitization

Osteoarthritis (OA) is the most common joint disorder in the world. Among the mechanisms involved in osteoarthritis, biomarkers (cytokines profile) may be related to pain and pain intensity, functional capacity, and pressure pain thresholds (PPT). Thus, the study of these relationships may offer useful information about pathophysiology and associated mechanisms involved in osteoarthritis. Therefore, the objective of this study was to investigate the seric concentration of pro (IL-6, IL-8, and TNF-α) and anti-inflammatory (IL-10) cytokines in patients with painful knee osteoarthritis and to correlate the levels of these biomarkers with the patients' functional capacity and pressure pain threshold (PPT) values.

Cytokines as biochemical markers for knee osteoarthritis

Osteoarthritis (OA) is a debilitating degenerative joint disease particularly affecting weightbearing joints within the body, principally the hips and knees. Current radiographic techniques are insufficient to show biochemical changes within joint tissue which can occur many years before symptoms become apparent. The need for better diagnostic and prognostic tools is heightened with the prevalence of OA set to increase in aging and obese populations. As inflammation is increasingly being considered an important part of OAs pathophysiology, cytokines are being assessed as possible candidates for biochemical markers. Cytokines, both pro- and anti-inflammatory, as well as angiogenic and chemotactic, have in recent years been studied for relevant characteristics. Biochemical markers show promise in determination of the severity of disease in addition to monitoring of the efficacy and safety of disease-modifying OA drugs, with the potential to act as diagnostic and prognostic tools. Currently, the diagnostic power of interleukin (IL)-6 and the relationship to disease burden of IL-1β, IL-15, tumor necrosis factor-α, and vascular endothelial growth factor make these the best candidates for assessment. Grouping appropriate cytokine markers together and assessing them collectively alongside other bone and cartilage degradation products will yield a more statistically powerful tool in research and clinical applications, and additionally aid in distinguishing between OA and a number of other diseases in which cytokines are known to have an involvement. Further large scale studies are needed to assess the validity and efficacy of current biomarkers, and to discover other potential biomarker candidates.

Plasma and synovial fluid sclerostin are inversely associated with radiographic severity of knee osteoarthritis

OBJECTIVE

The purpose of this study was to analyze sclerostin in plasma and synovial fluid of knee osteoarthritis (OA) patients and to investigate the association between sclerostin levels and radiographic severity.

DESIGN AND METHODS

A total of 190 subjects (95 knee OA patients and 95 healthy controls) were recruited in the present study. Sclerostin levels in plasma and synovial fluid were assessed using an enzyme-linked immunosorbent assay. OA grading was performed using the Kellgren-Lawrence classification.

RESULTS

Plasma sclerostin levels were significantly lower in OA patients than in healthy controls (P=0.004). Additionally, sclerostin levels in plasma were significantly higher with respect to paired synovial fluid (P<0.001). Moreover, sclerostin levels in plasma and synovial fluid demonstrated a significant inverse correlation with the radiographic severity of knee OA (r=-0.464, P<0.001 and r=-0.592, P<0.001, respectively). Subsequent analysis revealed that there was a positive correlation between plasma and synovial sclerostin levels (r=0.657, P<0.001).

CONCLUSIONS

Sclerostin was significantly lower in OA plasma samples when compared with healthy controls. Plasma and synovial fluid sclerostin levels were inversely associated with the radiographic severity of knee OA. Therefore, sclerostin may be utilized as a biochemical marker for reflecting disease severity in primary knee OA.

Intraarticular and Systemic Inflammatory Profiles May Identify Patients with Osteoarthritis

Objective.

To determine whether cytokine/chemokine profiles from synovial fluid and sera discriminate mild/moderate osteoarthritis (OA) from normal and severe OA cohorts.

Methods.

Multiplex technology was used to quantify expression levels for 42 cytokines in the synovial fluid of patients diagnosed with severe OA (n = 20) and mild/moderate OA (n = 12), as well as normal controls (n = 34). The same 42 cytokines were examined in serum samples of patients with severe OA (n = 26) and mild/moderate OA (n = 74) and normal individuals (n = 100). Treatment group comparisons followed by principal component analysis (PCA) and K-means clustering of the significantly different cytokines/chemokines revealed groupings of patients by physician diagnosis.

Results.

Differences in cytokine/chemokine levels were found between control, mild/moderate OA, and severe OA synovial fluid samples, as well as between normal and mild/moderate OA serum samples, and between control and severe OA serum samples. No differences were observed between mild/moderate and severe OA serum samples. Visual groupings based on PCA were validated by K-means analysis, with the best results obtained from the comparison of normal and mild/moderate OA serum samples with 96% of normal and 93% of mild/moderate OA samples accurately identified.

Conclusion.

Our study suggests that comparing the expression levels of cytokines/chemokines in synovial fluid and/or serum of patients with OA may have promise as a diagnostic platform to identify patients early in their disease course. This high-throughput low-cost assay may be able to provide clinicians with a diagnostic test to complement existing clinical and imaging modalities currently used to diagnose OA.

Osteoarthritis year 2012 in review: biomarkers

PURPOSE

Biomarkers provide useful diagnostic information by detecting cartilage degradation in osteoarthritis (OA), reflecting disease-relevant biological activity and predicting the course of disease progression. They also serve as surrogate endpoints in the drug discovery process. The aim of this narrative review was to focus on OA biomarker-related papers published between the osteoarthritis research society international (OARSI) 2011 meeting in San Diego and the OARSI 2012 meeting in Barcelona.

METHODS

The PubMed/MEDLINE and SciVerse Scopus bibliographic databases were searched using the keywords: 'biomarker' and 'osteoarthritis' and/or 'biomarker' and 'proteomics'.

RESULTS

Ninety-eight papers were found with the keywords 'biomarker' and 'osteoarthritis'. Fifteen papers were found with the keywords 'biomarker' and 'proteomics'. Review articles were also included. The most relevant published studies focused on extracellular matrix (ECM) molecules in body fluids. Enrichment of the deamidated epitope of cartilage oligomeric matrix protein (D-COMP) suggests that OA disease progression is associated with post-translational modifications that may show specificity for particular joint sites. Fibulin-3 peptides (Fib3-1 and Fib3-2) have been proposed as potential biomarkers of OA along with follistatin-like protein 1 (FSTL1), a new serum biomarker with the capacity to reflect the severity of joint damage. The 'membrane attack complex' (MAC) component of complement has also been implicated in OA.

CONCLUSION

Novel OA biomarkers are needed for sub-clinical disease diagnosis. Proteomic techniques are beginning to yield useful data and deliver new OA biomarkers in serum and urine. Combining biochemical markers with tissue and cell imaging techniques and bioinformatics (i.e., machine learning, clustering, data visualization) may facilitate the development of biomarker combinations enabling earlier detection of OA.

Effect of aerobic training on plasma cytokines and soluble receptors in elderly women with knee osteoarthritis, in response to acute exercise

The aim of this study was to evaluate levels of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and soluble forms of the TNF-α receptor (sTNFR1 and sTNFR2) from plasma taken from the peripheral blood of elderly individuals presenting with osteoarthritis (OA) of the knee. These patients underwent aerobic treatment through the use of physical exercises. The study consisted of a longitudinal analysis of older individuals presenting clinical and radiographic diagnosis of knee OA that were submitted to 12 weeks of aerobic treatment. The individuals were evaluated during acute exercise or after chronic exercise. During acute exercise (walking slowly on the mat), blood samples of the patients were collected before, immediately after, and 30 min following the end of training. After chronic exercise (aerobic walking training, three times/week for 12 weeks), patient blood samples were obtained for comparison. Additionally, clinical and functional assessments (WOMAC test and 6-min walk) were performed at the end of all physical exercises. Plasma concentrations of cytokines and soluble receptors were measured by ELISA. Aerobic training increased the plasma concentration of sTNR1; however, it decreased the plasma concentration of sTNFR2, when compared with levels of resting patients. Acute exercise differentially affects the levels of sTNFR1 dependent on when the samples were taken, before and after aerobic training. However, the levels of sTNFR2 were not affected by training. For the population studied, we observed differences in the levels of sTNFR1 and sTNFR2 following acute and chronic exercise. Other additional factors, like the level of inactivity of the individual and the type of physical exercise that patients are exposed to, need to be considered as well. The variation in the levels of soluble receptors correlated with functional improvement; however, the inflammatory osteoarthritis markers (IL-6 and TNF-α) were unaffected by the walking exercises.

Correlation between plasma and synovial fluid basic fibroblast growth factor with radiographic severity in primary knee osteoarthritis

PURPOSE

The aim of this study was to investigate plasma and synovial fluid basic fibroblast growth factor (bFGF) levels in patients with primary knee osteoarthritis (OA) and to evaluate the correlation between bFGF levels and disease severity.

METHODS

Thirty-five patients with knee OA and 15 healthy individuals were recruited into this study. Knee OA grading was performed according to the Kellgren-Lawrence classification. bFGF concentrations in both plasma and synovial fluid were determined using enzyme-linked immunosorbent assay.

RESULTS

Plasma and synovial fluid bFGF levels in knee OA patients were significantly higher than in controls (P < 0.001). Moreover, plasma and synovial fluid bFGF concentrations were positively correlated with radiographic severity (r = 0.535, P < 0.001 and r = 0.570, P < 0.001, respectively). Further analysis revealed that there was a positive correlation between plasma and synovial fluid bFGF levels (r = 0.674, P < 0.001).

CONCLUSIONS

Plasma and synovial fluid bFGF levels were significantly increased in OA patients, and these elevated levels were positively correlated with radiographic severity. These findings indicate that bFGF levels may be a monitor of disease severity and could play an essential part in the pathophysiology of degenerative process in OA.