The association between changes in synovial fluid levels of ARGS-aggrecan fragments, progression of radiographic osteoarthritis and self-reported outcomes: a cohort study

Safety, Tolerability, and Pharmacodynamics of the ADAMTS-5 Nanobody M6495: Two Phase 1, Single-Center, Double-Blind, Randomized, Placebo-Controlled Studies in Healthy Subjects and Patients With Osteoarthritis

OBJECTIVE

To assess the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple injections of M6495, a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5)  nanobody, in healthy volunteers and patients with osteoarthritis.

METHODS

Two randomized, placebo-controlled, double-blind studies were performed. Study 1 enrolled 54 healthy male volunteers who received one subcutaneous (s.c.) injection of M6495 (1-300 mg) or placebo (ratio 2:1), evaluating safety, PK, and PD as changes in the serum aggrecan fragment alanine-arginine-glycine-serine (ARGS). Study 2 enrolled 32 patients with osteoarthritis with Kellgren-Lawrence grades 2 to 4 and pain greater than or equal to 40 on the Western Ontario and McMaster Universities Arthritis Index pain subscale at screening and evaluated the safety, PK, and PD of three doses every two weeks (75-300 mg per dose) or six once-weekly M6495 s.c. doses (300 mg) or placebo (ratio 3:1) over 106 days' follow-up.

RESULTS

M6495 in single and multiple doses of less than or equal to 300 mg s.c. weekly was well tolerated with no clinically significant changes in any safety parameter. Adverse events more frequently reported in the M6495 groups were mostly mild cases of injection site reactions, myalgia, and nausea, which resolved after treatment cessation. The elimination half-life of single s.c. doses of M6495 ranged from 79 to 267 hours. M6495 administration substantially reduced serum ARGS levels, indicative of target engagement and indicating disease-modifying potential of M6495.

CONCLUSION

Treatment with M6495 in single and multiple doses up to and including 300 mg s.c. was found to be well tolerated and adequately safe for further clinical evaluation of potential disease-modifying effects.

Synovial Fluid Cytokine Profile at the Time of Arthroscopy Explains Intermediate-Term Functional Outcomes

BACKGROUND

The intra-articular immune response after ligamentous, meniscal, or focal chondral knee injuries likely plays a role in intra-articular healing and the onset and progression of posttraumatic osteoarthritis.

PURPOSE

To evaluate the association of synovial fluid cytokine concentrations measured at the time of knee arthroscopy with intermediate-term functional outcomes after knee arthroscopy based on the Lysholm score.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

This was a prospective cohort study of patients undergoing arthroscopic knee surgery. Synovial fluid was aspirated from the injured knee immediately before surgical incision, and the concentrations of 10 cytokines were analyzed using immunoassay. Principal component regression was used to create a model to predict patient-reported Lysholm score at a minimum of 5 years postoperatively. Hierarchical clustering was performed to identify groups of patients with similar synovial fluid inflammatory phenotypes. Lysholm scores and cytokine concentrations were compared between clusters.

RESULTS

A total of 26 patients (mean age, 40.33 ± 16.40 years) were included in the analysis. The mean duration between surgery and follow-up was 6.69 ± 0.72 years. A model consisting of 2 principal components (PC1, PC2) explained 62.48% of the variance in the cytokine data and 52.03% of the variance in intermediate-term Lysholm score. Hierarchical clustering resulted in 3 patient clusters based on the principal components used in the regression model. Despite no baseline differences in Lysholm score, cluster 3 demonstrated significantly greater intermediate-term Lysholm score compared with cluster 2 (94.33 vs 76.09, respectively; 95% CI, 5.96-30.52; P = .006) and cluster 1 (94.33 vs 52.33, respectively; 95% CI, 24.09-59.91; P = .003). Cluster 3, when compared with the overall means, was characterized by greater PC1 value (1.01 vs 0.00, respectively; P = .030) and greater PC2 value (0.86 vs 0.00, respectively; P = .002).

CONCLUSION

The concentrations of select synovial fluid cytokines assessed at the time of knee arthroscopy can be used to explain more than half of the variance in intermediate-term functional outcomes.

Associations Between Physical Activity, Self-reported Joint Function, and Molecular Biomarkers in Working Age Individuals With Hip and/or Knee Osteoarthritis

Objective:

Previous research has suggested an association between physical activity (PA), joint function, and molecular biomarkers, but more studies are needed. The aim of this study was to explore the associations between PA or self-reported joint function and molecular biomarkers of cartilage and inflammation in individuals with hip and/or knee osteoarthritis (OA). Specific objectives were to explore the correlations between (1) the change over 3 months in self-reported PA/joint function and the change in molecular biomarkers (2) objectively measured PA and molecular biomarkers measured at 3-month follow-up.

Design:

Working age participants (n = 91) were recruited from a cluster randomized controlled trial. Self-reported PA, joint function, and serum samples were collected at baseline and after 3 months. Serum concentrations of the inflammatory marker C-reactive protein (CRP) and the cartilage markers Alanine-Arginine-Glycine-Serine (ARGS)-aggrecan, cartilage oligomeric matrix protein (COMP), and type II collagen C2C were analyzed by immunoassays. Objectively measured PA (steps/day) was collected during 12 weeks from activity trackers used by 53 participants. Associations were analyzed with Spearman’s rank correlation.

Results:

There was a weak negative correlation between the change in self-reported PA and the change in COMP (r_s = −0.256, P = .040) but not for the other molecular biomarkers. There were no correlations between the change in self-reported joint function and the change in molecular biomarkers or between the average steps/day and the molecular biomarkers at follow-up (r_s ⩽ −0.206, P ⩾ .06).

Conclusion:

In general, no or only weak associations were found between PA/joint function and molecular biomarkers. Future research recommends including participants with lower PA, extend the follow-up, and use a design that allows comparisons.

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.

Correlation of serum and synovial leptin concentrations with body condition scores in healthy and osteoarthritic dogs

OBJECTIVE

To evaluate the relationship between serum and synovial fluid (SF) leptin concentrations and body condition score (BCS) in healthy and osteoarthritic dogs.

STUDY DESIGN

Controlled, prospective, clinical study.

ANIMALS

Nineteen healthy dogs and 29 dogs with osteoarthritis (OA) secondary to cranial cruciate ligament injury.

METHODS

Synovial fluid was obtained from the femorotibial joint under sedation (healthy dogs) or during surgery (OA dogs). Serum and SF leptin and interleukin (IL)-1β concentrations were measured via enzyme-linked immunosorbent assay. Dogs were classified as optimal weight (BCS 4-5/9) or overweight (BCS >5/9). Radiographs were scored for OA severity by a radiologist. Owners completed the Liverpool Osteoarthritis in Dogs (LOAD) questionnaire.

RESULTS

Mean (± SD) SF leptin (4.09 ± 4 ng/mL) was lower than serum leptin (6.88 ± 5.52 ng/mL, P < .0001). Synovial fluid leptin was higher in overweight (5.28 ± 4.21) than in optimal body weight dogs (1.54 ± 1.72 ng/mL, P < .0001). Serum (P < .001) and SF leptin (P = .004) concentrations were associated with BCS. Concentration of SF leptin did not differ between healthy (2.4 ± 2.04 ng/mL) and OA (4.9 ± 4.3 ng/mL, P = .25) dogs. Synovial fluid leptin and LOAD scores were weakly associated (P = .03). No association was detected between SF leptin and radiographic score or IL-1β (P = .73).

CONCLUSION

Serum and SF leptin correlated with BCS in this population. Synovial fluid leptin was weakly associated with LOAD scores but not with radiographic severity of OA or IL-1β.

CLINICAL SIGNIFICANCE

Serum and SF leptin concentrations do not predict radiographic severity of canine OA but contribute to joint pain and dysfunction.

MMP-3 in the peripheral serum as a biomarker of knee osteoarthritis, 40 years after open total knee meniscectomy

BACKGROUND

To explore potential biomarkers in a meniscectomy-induced knee osteoarthritis model, at forty years after meniscectomy.

METHODS

We carried out a forty-year study of 53 patients who, as adolescents, underwent open total meniscectomy and assessed two potential synovial and serum biomarkers, namely glycosaminoglycan (GAG) and matrix metalloproteinase-3 (MMP-3). Of the 30 patients available for review, 8 had contralateral knee operations and were excluded. Of the remaining 22 patients, 17 had successful operated knee synovial fluid aspirations and 8 also had successful contralateral control knee aspirations. GAG and MMP3 levels in the synovial fluid and peripheral serum was measured using Alcian blue precipitation and ELISA quantification, respectively. Patients also had their knee radiographs assessed and their radiographic osteoarthritis classified as per the Kellgren-Lawrence and Ahlbӓck systems.

RESULTS

At forty years after meniscectomy, synovial MMP-3 levels remain increased (p = 0.0132) while GAG levels were reduced (p = 0.0487) when compared to controls and these two levels correlate inversely. Furthermore, levels of synovial MMP-3 significantly correlated (p = 0.0032, r = 0.7734; p = 0.0256, r = 0.5552) and GAG levels significantly inversely correlated (p = 0.0308, r = - 0.6220; p = 0.0135, r = - 0.6024), respectively, with both radiological scoring systems. Interestingly, we found that the levels of serum MMP-3 correlated only with the synovial fluid levels of MMP-3 in the operated knee and not with the non-operated joint (p = 0.0252, r = 0.7706 vs. p = 0.0764, r = 0.6576). Multiple regression analysis for patient's quality of life based on these biomarkers revealed an almost perfect result with an R2 of 0.9998 and a p value = 0.0087.

CONCLUSION

Our results suggest that serum levels of MMP3 could be used as a potential biomarker for knee osteoarthritis, using a simple blood test. Larger cohorts are desirable in order to prove or disprove this finding.

Time between anterior cruciate ligament injury and reconstruction and cartilage metabolism six-months following reconstruction

BACKGROUND

To determine the association between time from injury to ACL reconstruction (Time^Injury-ACLR) and biochemical markers of cartilage metabolism and inflammation six months following ACL reconstruction (ACLR).

METHODS

Individuals with a unilateral ACL injury were enrolled at initial presentation in the orthopedic clinic; blood was collected six months following ACLR. Enzyme-linked immunosorbent assays were used to analyze the ratio of serum concentrations of type-II collagen breakdown (C2C) to synthesis (CPII), plasma matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and serum aggrecan neoepitope (ARGS). We used separate linear regressions to assess associations between biochemical markers and Time^Injury-ACLR.

RESULTS

Twenty-two participants (50% females, mean [SD], age 21.9 [4.5] years old; BMI 23.8 [2.6] kg/m²) completed the study. Time^Injury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater Time^Injury-ACLR predicted greater serum C2C:CPII ratios six months following ACLR (C2C:CPII=0.15 [0.02], R²=0.213, P=0.030). Males (R²=0.733, P=0.001) but not females (R²=0.030, P=0.609) demonstrated a significant association between greater C2C:CPII and Time^Injury-ACLR at the six-month follow-up exam. Time^Injury-ACLR did not associate with IL-6, MMP-3, or ARGS at six months.

CONCLUSIONS

Greater time between injury and ACL reconstruction was associated with greater serum C2C:CPII six months following ACLR in males but not females, and IL-6, MMP-3, and ARGS levels were not associated with Time^Injury-ACLR in males or females. The time between ACL injury and ACLR may affect collagen metabolism in males and should be further investigated in a larger study along with other patient-relevant outcomes.

Aging and osteoarthritis: Central role of the extracellular matrix

Osteoarthritis (OA), is a major cause of severe joint pain, physical disability and quality of life impairment in the aging population across the developed and developing world. Increased catabolism in the extracellular matrix (ECM) of the articular cartilage is a key factor in the development and progression of OA. The molecular mechanisms leading to an impaired matrix turnover have not been fully clarified, however cellular senescence, increased expression of inflammatory mediators as well as oxidative stress in association with an inherently limited regenerative potential of the tissue, are all important contributors to OA development. All these factors are linked to and tend to be maximized by aging. Nonetheless the role of aging in compromising joint stability and function in OA has not been completely clarified yet. This review will systematically analyze cellular and structural changes taking place in the articular cartilage and bone in the pathogenesis of OA which are linked to aging. A particular emphasis will be placed on age-related changes in the phenotype of the articular chondrocytes.

Surgical reconstruction of ruptured anterior cruciate ligament prolongs trauma-induced increase of inflammatory cytokines in synovial fluid: an exploratory analysis in the KANON trial

OBJECTIVE

Prospectively monitor how treatment of acutely ruptured anterior cruciate ligament (ACL) affects biomarkers of inflammation and proteolytic degradation over 5 years.

DESIGN

We studied 119 subjects with acute ACL injury from the randomized controlled knee anterior cruciate ligament, non-surgical versus surgical treatment (KANON)-trial (Clinical trial ISRCTN 84752559) who had synovial fluid, serum and urine samples available from at least two out of six visits over 5 years after acute ACL rupture. All subjects followed a similar rehabilitation protocol where, according to randomization, 60 also had early ACL reconstruction and 59 had the option to undergo a delayed ACL reconstruction if needed. Interleukin (IL)-6, IL-8, IL-10, interferon-gamma (IFNγ), tumor necrosis factor (TNF), amino acids alanine, arginine, glycine, serine (ARGS)-aggrecan, C-terminal crosslinking telopeptide type II collagen (CTX-II) and N-terminal crosslinking telopeptide type I collagen (NTX-I) were quantified by enzyme-linked immunosorbent assays (ELISA).

RESULTS

Subjects randomized to early ACL reconstruction had higher cytokine concentrations in index knee synovial fluid at 4 months (IL-6, IL-8, IL-10, TNF), 8 months (IL-6 and TNF) and at 5 years (IFNγ) compared to those randomized to optional delayed reconstruction. Those that underwent delayed ACL reconstruction within 5 years (30 subjects), had higher synovial fluid concentrations of IL-6 at 5 years compared to those treated with rehabilitation alone. No differences between groups were noted for ARGS-aggrecan in synovial fluid and serum or CTX-II and NTX-I in urine over 5 years, neither as randomized nor as treated.

CONCLUSIONS

Surgical ACL reconstruction constitutes a second trauma to the acutely injured joint resulting in a prolonged elevation of already high synovial fluid levels of inflammatory cytokines.

Patellar position in weight-bearing radiographs compared with non-weight-bearing: significance for the detection of osteoarthritis

Background Diagnosis and treatment of patellofemoral disorders including osteoarthritis are currently often based on imaging and clinical assessment with patients in the supine position. Purpose To evaluate differences in patellar position in the trochlear groove and to assess the detection of medial and lateral patellofemoral (PF) osteoarthritis (OA) on axial radiographs in supine and standing positions, respectively. Material and Methods Thirty-five women and 23 men (mean age, 56 years; age range, 18-87 years) referred for routine radiographic examinations of the knees were included. Axial radiographs of the PF joint in both supine non-weight-bearing and standing weight-bearing position in 30° knee flexion were obtained of 111 knees. Measurements performed on the radiographs: patellar tilt, patellar displacement, joint space width, and grade of OA according to Ahlbäck. Results From supine to standing position the patella moved medially and medial joint space width and lateral patellar tilt angle decreased ( P < 0.0001 for the three measured parameters). In the standing position, medial PF OA was observed in 19 knees compared to three knees in the supine position. Fourteen knees had lateral PF OA with almost unchanged grade of OA irrespective of position. Conclusion In weight-bearing positions, the patella is positioned medially in the trochlear groove compared to supine non-weight-bearing positions. Therefore, this study suggests that the common occurrence of medial PF OA can generally not be detected on axial radiographs in supine non-weight-bearing positions and confirms the importance of imaging the PF joint in standing weight-bearing positions.

Relationship between synovial fluid biomarkers of articular cartilage metabolism and the patient's perspective of outcome depends on the severity of articular cartilage damage following ACL trauma

Anterior cruciate ligament (ACL) trauma often occurs in combination with injury to the articular cartilage of the knee, this can result in earlier radiographic evidence of post traumatic osteoarthritis (OA) of the knee compared to the contralateral, ACL intact knee; however, the biomechanical and biological mechanisms associated with the onset and progression of this disease are not understood. We sought to gain insight into the mechanisms by determining the relationship between articular cartilage injury associated with ACL trauma and the expression of synovial fluid biomarkers of articular cartilage metabolism, and to evaluate the relationship between these biomarkers and the patient's perspective of the outcomes. Synovial fluid samples were acquired from 39 ACL injured subjects at an average of 10 weeks after injury, and 32 control subjects with normal knees (documented with clinical exam and MRI assessment). Subjects in the ACL-injured group were classified as low-risk for future OA if they displayed an International Cartilage Repair Society (ICRS) Grade 2 articular cartilage lesion or less and high-risk for future OA if they had an ICRS Grade 3A articular cartilage lesion. The patient's perspective of the injury was evaluated with the Knee Injury and Osteoarthritis Outcomes Score (KOOS). There were no significant differences in mean concentrations of the markers of type II collagen metabolism (CPII, C2C, and C1,2C) or the aggrecan breakdown Alanine-Arginine-Glycine-Serine (ARGS) -fragment between control subjects and the subjects in the low- and high-risk groups (p-value range: 0.80-0.43). Associations between ARGS-aggrecan concentration and KOOS subscales of symptoms and pain were significantly different between the low- and high-risk groups (p = 0.03 and p = 0.01, respectively). Likewise, there was strong evidence in support of an association between the markers of type II collagen metabolism (C1,2C and CPII concentrations) and the KOOS subscale of pain between the low- and high-risk groups (p = 0.051 and 0.077, correspondingly). In ACL injured subjects with concomitant Grade 3A articular cartilage injuries, concentrations of synovial fluid ARGS-aggrecan were directly associated with improvements in KOOS symptoms and pain. These findings suggest the possible involvement of ARGS-aggrecan in a localized tissue repair response involving an increase in aggrecan turnover following severe knee trauma. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:820-827, 2016.

Aggrecan heterogeneity in articular cartilage from patients with osteoarthritis

Background

Aggrecan degradation is the hallmark of cartilage degeneration in osteoarthritis (OA), though it is unclear whether a common proteolytic process occurs in all individuals.

Methods

Aggrecan degradation in articular cartilage from the knees of 33 individuals with OA, who were undergoing joint replacement surgery, was studied by immunoblotting of tissue extracts.

Results

Matrix metalloproteinases (MMPs) and aggrecanases are the major proteases involved in aggrecan degradation within the cartilage, though the proportion of aggrecan cleavage attributable to MMPs or aggrecanases was variable between individuals. However, aggrecanases were more associated with the increase in aggrecan loss associated with OA than MMPs. While the extent of aggrecan cleavage was highly variable between individuals, it was greatest in areas of cartilage adjacent to sites of cartilage erosion compared to sites more remote within the same joint. Analysis of link protein shows that in some individuals additional proteolytic mechanisms must also be involved to some extent.

Conclusions

The present studies indicate that there is no one protease, or a fixed combination of proteases, responsible for cartilage degradation in OA. Thus, rather than targeting the individual proteases for OA therapy, directing research to techniques that control global protease generation may be more productive.

Relationship between synovial fluid ARGS-aggrecan fragments, cytokines, MMPs, and TIMPs following acute ACL injury: A cross-sectional study

Severe knee trauma, such as an ACL disruption, produces aggrecan degradation as evidenced by elevated synovial fluid (SF) N-terminal (393) Alanine-Arginine-Glycine-Serine (ARGS) neoepitope (or ARGS-aggrecan) and is associated with inflammatory activity soon after injury. However, it is not known if this process persists for a substantial time interval following the initial trauma. The purpose of this study was to evaluate relationships between SF ARGS concentrations and an array of cytokines, matrix metalloproteases (MMPs), and tissue inhibitor of metalloproteases (TIMPs) during the initial 6 months following ACL rupture. SF samples from 67 ACL-injured subjects (29 women) were analyzed within 6 months of injury (18-155 days), immediately prior to surgical ACL reconstruction. Relationships between ARGS and individual analyte concentrations, as well as MMP/TIMP ratios were evaluated. Statistically significant relationships were found between ARGS and basic fibroblast growth factor (FGF2) (p=0.03) and TIMP-3 (p=0.01). Our findings suggest that FGF2, considered to be primarily catabolic in articular cartilage, is not downregulated as ARGS concentration declines over time since injury. In addition, these results support the hypothesis that an upregulation of TIMP-3, the primary aggrecanase inhibitor, is elicited in response to increased aggrecan degradation, which may inhibit further cleavage.

Interleukin-6 and tumor necrosis factor alpha in synovial fluid are associated with progression of radiographic knee osteoarthritis in subjects with previous meniscectomy

OBJECTIVE

To explore potential associations between proinflammatory cytokines in synovial fluid and progression of osteoarthritis (OA) in meniscectomized subjects.

DESIGN

We studied 132 subjects on average 18 years after meniscectomy, with a second examination 4-10 years later. We measured concentrations of interleukin (IL)-6, -8 and tumor necrosis factor (TNF)-α by multiplex immunoassay, graded radiographic features of tibiofemoral and patellofemoral OA according to the Osteoarthritis Research Society International (OARSI) atlas, scored patient-reported outcomes using the Knee Injury and Osteoarthritis Outcome Score (KOOS), and used logistic regression (adjusted for age, gender, body mass index, and time between examinations) for assessment of associations.

RESULTS

Higher first examination concentrations of IL-6 and TNF-α were associated with increased risk for subsequent osteophyte progression (odds ratios (OR); 95% confidence intervals 1.05; 1.00-1.09 and 1.35; 1.03-1.75). Higher second examination concentrations of TNF-α were associated with having progressed in loss of joint space (OR 1.70; 1.15-2.52) or having worsened in the activity of daily living subscale of KOOS (OR 1.50; 1.07-2.09) in the preceding years. Subjects with increasing concentrations of IL-6 or TNF-α between examinations were five times more likely to have progressed in joint space narrowing between the same examinations, as compared to those with stable or decreasing concentrations (OR 5.17; 1.54-17.32 and 5.01; 1.32-18.92).

CONCLUSIONS

In subjects with previous meniscectomy, higher or over time increasing synovial fluid levels of IL-6 and TNF-α seems to be associated with increased risk for progression of radiographic OA.

KOOS pain as a marker for significant knee pain two and six years after primary ACL reconstruction: a Multicenter Orthopaedic Outcomes Network (MOON) prospective longitudinal cohort study

OBJECTIVE

The prevalence of radiographic osteoarthritis (OA) after anterior cruciate ligament reconstruction (ACLR) approaches 50%, yet the prevalence of significant knee pain is unknown. We applied three different models of Knee injury and Osteoarthritis Outcome Score (KOOS) thresholds for significant knee pain to an ACLR cohort to identify prevalence and risk factors.

DESIGN

Multicenter Orthopaedic Outcomes Network (MOON) prospective cohort patients with a unilateral primary ACLR and normal contralateral knee were assessed at 2 and 6 years. Independent variables included patient demographics, validated Patient Reported Outcomes (PRO; Marx activity score, KOOS), and surgical characteristics. Models included: (1) KOOS criteria for a painful knee = quality of life subscale <87.5 and ≥2 of: KOOSpain <86.1, KOOSsymptoms <85.7, KOOSADL <86.8, or KOOSsports/rec <85.0; (2) KOOSpain subscale score ≤72 (≥2 standard deviations below population mean); (3) 10-point KOOSpain drop from 2 to 6 years. Proportional odds models (alpha ≤ 0.05) were used.

RESULTS

1761 patients of median age 23 years, median body mass index (BMI) 24.8 kg/m(2) and 56% male met inclusion, with 87% (1530/1761) and 86% (1506/1761) follow-up at 2 and 6 years, respectively. At 6 years, n = 592 (39%), n = 131 (9%) and n = 169 (12%) met criteria for models #1 through #3, respectively. The most consistent and strongest independent risk factor at both time-points was subsequent ipsilateral knee surgery. Low 2-year Marx activity score increased the odds of a painful knee at 6 years.

CONCLUSIONS

Significant knee pain is prevalent after ACLR; with those who undergo subsequent ipsilateral surgery at greatest risk. The relationship between pain and structural OA warrants further study.

What Are the Prognostic Factors for Radiographic Progression of Knee Osteoarthritis? A Meta-analysis

BACKGROUND

A previous systematic review on prognostic factors for knee osteoarthritis (OA) progression showed associations for generalized OA and hyaluronic acid levels. Knee pain, radiographic severity, sex, quadriceps strength, knee injury, and regular sport activities were not associated. It has been a decade since the literature search of that review and many studies have been performed since then investigating prognostic factors for radiographic knee OA progression.

QUESTIONS/PURPOSES

The purpose of this study is to provide an updated systematic review of available evidence regarding prognostic factors for radiographic knee OA progression.

METHODS

We searched for observational studies in MEDLINE and EMBASE. Key words were: knee, osteoarthritis (or arthritis, or arthrosis, or degenerative joint disease), progression (or prognosis, or precipitate, or predictive), and case-control (or cohort, or longitudinal, or follow-up). Studies fulfilling the inclusion criteria were assessed for methodologic quality according to established criteria for reviews on prognostic factors in musculoskeletal disorders. Data were extracted and results were pooled if possible or summarized according to a best-evidence synthesis. A total of 1912 additional articles were identified; 43 met our inclusion criteria. The previous review contained 36 articles, thus providing a new total of 79 articles. Seventy-two of the included articles were scored high quality, the remaining seven were low quality.

RESULTS

The pooled odds ratio (OR) of two determinants showed associations with knee OA progression: baseline knee pain (OR, 2.38 [95% CI, 1.74-3.27) and Heberden nodes (OR, 2.66 [95% CI, 1.46-8.84]). Our best-evidence synthesis showed strong evidence that varus alignment, serum hyaluronic acid, and tumor necrosis factor-α are associated with knee OA progression. There is strong evidence that sex, former knee injury, quadriceps strength, smoking, running, and regular performance of sports are not associated with knee OA progression. Evidence for the majority of determined associations, however, was limited, conflicting, or inconclusive.

CONCLUSIONS

Baseline knee pain, presence of Heberden nodes, varus alignment, and high levels of serum markers hyaluronic acid and tumor necrosis factor-α predict knee OA progression. Sex, knee injury, and quadriceps strength, among others, did not predict knee OA progression. Large variation remains in definitions of knee OA and knee OA progression. Clinical studies should use more consistent definitions of these factors to facilitate data pooling by future meta-analyses.

Prognostic factors for progression of clinical osteoarthritis of the knee: a systematic review of observational studies

INTRODUCTION

We performed a systematic review of prognostic factors for the progression of symptomatic knee osteoarthritis (OA), defined as increase in pain, decline in physical function or total joint replacement.

METHOD

We searched for available observational studies up to January 2015 in Medline and Embase according to a specified search strategy. Studies that fulfilled our initial inclusion criteria were assessed for methodological quality. Data were extracted and the results were pooled, or if necessary summarized according to a best evidence synthesis.

RESULTS

Of 1,392 articles identified, 30 met the inclusion criteria and 38 determinants were investigated. Pooling was not possible due to large heterogeneity between studies. The best evidence synthesis showed strong evidence that age, ethnicity, body mass index, co-morbidity count, magnetic resonance imaging (MRI)-detected infrapatellar synovitis, joint effusion and baseline OA severity (both radiographic and clinical) are associated with clinical knee OA progression. There was moderate evidence showing that education level, vitality, pain-coping subscale resting, MRI-detected medial femorotibial cartilage loss and general bone marrow lesions are associated with clinical knee OA progression. However, evidence for the majority of determinants was limited (including knee range of motion or markers) or conflicting (including age, gender and joint line tenderness).

CONCLUSION

Strong evidence was found for multiple prognostic factors for progression of clinical knee OA. A large variety in definitions of clinical knee OA (progression) remains, which makes it impossible to summarize the evidence through meta-analyses. More research on prognostic factors for knee OA is needed using symptom progression as an outcome measure. Remarkably, only few studies have been performed using pain progression as an outcome measure. The pathophysiology of radiographic factors and their relation with symptoms should be further explored.

Inflammatory cytokines and biomarkers of cartilage metabolism 8 years after anterior cruciate ligament reconstruction: results from operated and contralateral knees

BACKGROUND

Patients who sustain an acute anterior cruciate ligament (ACL) rupture are at increased risk to develop posttraumatic arthritis (PTA) in the injured knee whether the ACL is reconstructed or treated nonoperatively. Inflammatory cytokines and cartilage degradation biomarkers are elevated at the time of acute injury and postoperatively. This suggests that one mechanism for PTA may be an inflammatory degradative process initiated on the acute injury and sustained for some length of time independent of whether adequate joint stability is restored.

HYPOTHESIS

Inflammatory cytokines and biomarkers of cartilage degradation are elevated in the synovial fluid several years after reconstruction of the ACL, indicating an ongoing imbalance between extracellular matrix destruction and repair.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In 11 patients who had undergone ACL reconstruction 8 years earlier, knee synovial fluid was aspirated from the operated knee and the contralateral nonoperated knee. The synovial fluid was analyzed for interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, sulfated glycosaminoglycans (sGAG), aggrecan neoepitope fragment (ARGS-aggrecan), and cartilage oligomeric matrix protein (COMP). At follow-up, the patients underwent bilateral weightbearing radiographs and bilateral MRIs of their knees.

RESULTS

No significant differences between the operated and the contralateral knee were found for the synovial fluid concentrations of IL-1β, IL-6, TNF-α, sGAG, ARGS-aggrecan, or COMP. There were significantly more radiographically visible osteoarthritic changes in the operated knees compared with the contralateral knees. MRIs revealed that all grafts and all contralateral ACLs were intact and, furthermore, that there was significantly more meniscal and cartilage damage in the index knees than the contralateral knees.

CONCLUSION

Eight years after ACL reconstruction, there were no significant differences in inflammatory cytokines and biomarkers for cartilage degeneration between the nonoperated and the ACL-reconstructed knee, even though there were more osteoarthritic changes and meniscal and cartilage damage in the operated knee, as seen on weightbearing radiographs and MRI.

Biomarkers of (osteo)arthritis

Arthritic diseases are a major cause of disability and morbidity, and cause an enormous burden for health and social care systems globally. Osteoarthritis (OA) is the most common form of arthritis. The key risk factors for the development of OA are age, obesity, joint trauma or instability. Metabolic and endocrine diseases can also contribute to the pathogenesis of OA. There is accumulating evidence to suggest that OA is a whole-organ disease that is influenced by systemic mediators, inflammaging, innate immunity and the low-grade inflammation induced by metabolic syndrome. Although all joint tissues are implicated in disease progression in OA, articular cartilage has received the most attention in the context of aging, injury and disease. There is increasing emphasis on the early detection of OA as it has the capacity to target and treat the disease more effectively. Indeed it has been suggested that this is the era of "personalized prevention" for OA. However, the development of strategies for the prevention of OA require new and sensitive biomarker tools that can detect the disease in its molecular and pre-radiographic stage, before structural and functional alterations in cartilage integrity have occurred. There is also evidence to support a role for biomarkers in OA drug discovery, specifically the development of disease modifying osteoarthritis drugs. This Special Issue of Biomarkers is dedicated to recent progress in the field of OA biomarkers. The papers in this Special Issue review the current state-of-the-art and discuss the utility of OA biomarkers as diagnostic and prognostic tools.

Republished: Value of biomarkers in osteoarthritis: current status and perspectives

Osteoarthritis affects the whole joint structure with progressive changes in cartilage, menisci, ligaments and subchondral bone, and synovial inflammation. Biomarkers are being developed to quantify joint remodelling and disease progression. This article was prepared following a working meeting of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis convened to discuss the value of biochemical markers of matrix metabolism in drug development in osteoarthritis. The best candidates are generally molecules or molecular fragments present in cartilage, bone or synovium and may be specific to one type of joint tissue or common to them all. Many currently investigated biomarkers are associated with collagen metabolism in cartilage or bone, or aggrecan metabolism in cartilage. Other biomarkers are related to non-collagenous proteins, inflammation and/or fibrosis. Biomarkers in osteoarthritis can be categorised using the burden of disease, investigative, prognostic, efficacy of intervention, diagnostic and safety classification. There are a number of promising candidates, notably urinary C-terminal telopeptide of collagen type II and serum cartilage oligomeric protein, although none is sufficiently discriminating to differentiate between individual patients and controls (diagnostic) or between patients with different disease severities (burden of disease), predict prognosis in individuals with or without osteoarthritis (prognostic) or perform so consistently that it could function as a surrogate outcome in clinical trials (efficacy of intervention). Future avenues for research include exploration of underlying mechanisms of disease and development of new biomarkers; technological development; the ‘omics’ (genomics, metabolomics, proteomics and lipidomics); design of aggregate scores combining a panel of biomarkers and/or imaging markers into single diagnostic algorithms; and investigation into the relationship between biomarkers and prognosis.

An ARGS-aggrecan assay for analysis in blood and synovial fluid

OBJECTIVE

To validate a modified ligand-binding assay for the detection of aggrecanase generated aggrecan fragments with the ARGS neoepitope in synovial fluid (SF) and blood, and to verify the identity of aggrecan fragments found in blood.

DESIGN

An enzyme-linked immunosorbent assay (ELISA) on the Meso Scale Discovery (MSD) platform for detection of ARGS-aggrecan was validated, using a standard made from recombinant human aggrecan. Matched samples of SF, serum, plasma, and urine were obtained from 36 subjects at different time points after knee injury, and analysed for ARGS-aggrecan content. Aggrecan was purified from serum and plasma pools and analysed by Western blot.

RESULTS

The limits of quantification for the ARGS-aggrecan assay was between 0.2 and 0.025 pmol ARGS/ml, and the sensitivity of the assay was improved two-fold compared to when using a standard purified from human donors. The ARGS concentrations were highest in SF (mean, range; 3.02, 0.36-30.22 pmol/ml), 20 times lower in the blood samples (0.14, 0.055-0.28 pmol/ml serum and 0.13, 0.053-0.28 pmol/ml plasma), and 80 times lower in urine (0.036, below detection - 0.087 pmol/ml). Serum-ARGS and plasma-ARGS concentrations were similar, and correlated (r(S) = 0.773, P < 0.001). SF concentration correlated with serum concentrations (r(S) = 0.420, P = 0.011). In blood, we identified 129-138 kDa aggrecan fragments containing the ARGS neoepitope.

CONCLUSIONS

This novel ARGS-aggrecan assay is highly sensitive and suited for analysis of SF and blood samples. Both SF and blood contains ARGS-aggrecan, and ARGS concentrations in SF and serum are correlated.

Delineating the synovial fluid proteome: recent advancements and ongoing challenges in biomarker research

There is an urgent need for identifying novel serum biomarkers that can be used to improve diagnosis, predict disease progression or response to therapy, or serve as therapeutic targets for rheumatic diseases. Synovial fluid (SF) is secreted by and remains in direct contact with the synovial membrane, and can reflect the biochemical state of the joint under different physiological and pathological conditions. Therefore, SF is regarded as an excellent source for identifying biomarkers of rheumatologic diseases. The use of high-throughput and/or quantitative proteomics and sophisticated computational software applied to analyze the protein content of SF has been well-adopted as an approach to finding novel arthritis biomarkers. This review will focus on some of the potential pitfalls of biomarker studies using SF, summarize the status of the field of SF proteomics in general, as well as discuss some of the most promising biomarker study approaches using proteomics. A brief status of the biomarker discovery efforts in rheumatoid arthritis, osteoarthritis and juvenile idiopathic arthritis is also provided.

Value of biomarkers in osteoarthritis: current status and perspectives

Osteoarthritis affects the whole joint structure with progressive changes in cartilage, menisci, ligaments and subchondral bone, and synovial inflammation. Biomarkers are being developed to quantify joint remodelling and disease progression. This article was prepared following a working meeting of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis convened to discuss the value of biochemical markers of matrix metabolism in drug development in osteoarthritis. The best candidates are generally molecules or molecular fragments present in cartilage, bone or synovium and may be specific to one type of joint tissue or common to them all. Many currently investigated biomarkers are associated with collagen metabolism in cartilage or bone, or aggrecan metabolism in cartilage. Other biomarkers are related to non-collagenous proteins, inflammation and/or fibrosis. Biomarkers in osteoarthritis can be categorised using the burden of disease, investigative, prognostic, efficacy of intervention, diagnostic and safety classification. There are a number of promising candidates, notably urinary C-terminal telopeptide of collagen type II and serum cartilage oligomeric protein, although none is sufficiently discriminating to differentiate between individual patients and controls (diagnostic) or between patients with different disease severities (burden of disease), predict prognosis in individuals with or without osteoarthritis (prognostic) or perform so consistently that it could function as a surrogate outcome in clinical trials (efficacy of intervention). Future avenues for research include exploration of underlying mechanisms of disease and development of new biomarkers; technological development; the ‘omics’ (genomics, metabolomics, proteomics and lipidomics); design of aggregate scores combining a panel of biomarkers and/or imaging markers into single diagnostic algorithms; and investigation into the relationship between biomarkers and prognosis.

Detection of ADAMTS-4 activity using a fluorogenic peptide-conjugated Au nanoparticle probe in human knee synovial fluid

A disintegrin and metalloproteinase with thrombospondin motif-4 (ADAMTS-4) plays a pivotal role in degrading aggrecan, which is an early event in cartilage degrading joint diseases such as osteoarthritis (OA). Detection of ADAMTS-4 activity could provide useful clinical information for early diagnosis of such diseases and disease-modifying therapy. Therefore, we developed a ADAMTS-4 detective fluorescent turn-on AuNP probe (ADAMTS-4-D-Au probe) by conjugating gold nanoparticles with a FITC-modified ADAMTS-4-specific peptide (DVQEFRGVTAVIR). When the ADAMTS-4-D-Au probe was incubated with ADAMTS-4, the fluorescence recovered and fluorescence intensity markedly increased in proportion to concentrations of ADAMTS-4 and the probe. A nearly 3-fold increase in fluorescent intensity in response to only 3.9 pM of ADAMTS-4 was detected, whereas almost no fluorescence recovery was observed when the probe was incubated with matrix metalloproteinase (MMP)-1, -3, and -13. These results indicate a relative high sensitivity and specificity of the probe. Moreover, ADAMTS-4-D-Au probe was used to detect ADAMTS-4 activity in synovial fluid from 11 knee surgery patients. A substantial increase in fluorescent intensity was observed in the acute joint injury group as compared to the chronic joint injury and end-stage OA groups, indicating that this simple and low-cost sensing system might serve as a new detection method for ADAMTS-4 activity in biological samples and in screens for inhibitors for ADAMTS-4-related joint diseases. Additionally, this probe could be a potential biomarker for early diagnosis of cartilage-degrading joint diseases.

Association between cartilage and bone biomarkers and incidence of radiographic knee osteoarthritis (RKOA) in UK females: a prospective study

OBJECTIVE

There is a need to find biochemical markers that would identify people with increased risk of developing radiographic knee osteoarthritis (RKOA). The aim of this study was to evaluate the ability of cartilage and bone biomarkers (cartilage oligomeric matrix protein (COMP), aggrecan, cellular inhibitor of apoptosis protein (cIAP), N-telopeptide-to-helix (NTx)) to predict RKOA incidence in a 10-year follow-up of UK females from the Chingford community study.

METHOD

Joint space narrowing (JSN), osteophytes (OSP) and Kellgren-Lawrence (K/L) grades were scored from radiographs of both knees at study baseline and 10 years later in 1,003 women aged 45-64. Circulating levels of biomarkers and demographic variables were measured at baseline. Statistical association analysis was conducted between the potential predictor factors measured at baseline and documentation of RKOA at 10-year follow-up.

RESULTS

Age and body mass index (BMI), were significant predictors of incidence of RKOA as assessed by K/L and OSP. Considering biomarkers, independent significant association was found between COMP circulating levels and K/L scores (Odd Ratio (OR) = 2.87, 95% Confidence Interval (CI) = 1.19-6.89, P = 0.018). Significant negative association was detected between aggrecan plasma concentrations and JSN, with OR = 0.37 (95% CI 0.15-0.89), P = 0.026.

CONCLUSIONS

Aggrecan and COMP circulating levels contribute to identification of phenotype-specific RKOA incidence. These data suggest potentially protective role of aggrecan in cartilage loss, as measured by JSN. High COMP levels are risk factors for development of RKOA, as assessed by K/L scores.