Biomarkers in osteoarthritis

Comparison of high-resolution magnetic resonance imaging and micro-computed tomography arthrography for in-vivo assessment of cartilage in non-human primate models

Background

Non-human primate (NHP) could be an interesting model for osteoarthritis (OA) longitudinal studies but standard medical imaging protocols are not able to acquire sufficiently high-resolution images to depict the thinner cartilage (compared to human) in an in vivo context. The aim of this study was thus to develop and validate the acquisition protocols for knee joint examination of NHP using magnetic resonance imaging (MRI) at 1.5 T and X-ray micro-computed tomography arthrography (µCTA).

Methods

The first phase of the study focused on developing dedicated in vivo HR-MRI and µCTA protocols for simultaneous acquisitions of both knee joints on NHP. For MR, a dedicated two-channel receiver array coil and acquisition sequence were developed on a 1.5 T Siemens Sonata system and tuned to respect safety issues and reasonable examination time. For µCTA, an experimental setup was devised so as to fulfill similar requirements. The two imaging protocols were used during a longitudinal study so as to confirm that repeated injections of loxaglic acid (contrast agent used for µCTA) didn't induce any bias in cartilage assessment and to compare segmentation results from the two modalities. Lateral and medial cartilage tibial plateaus were assessed using a common image processing protocol leading to a 3D estimation of the cartilage thickness.

Results

From HR-MRI and µCTA images, thickness distributions were extracted allowing for proper evaluation of knee cartilage thickness of the primates. Results obtained in vivo indicated that the µCTA protocol did not induce any bias in the measured cartilage parameters and moreover, segmentation results obtained from the two imaging modalities were consistent.

Conclusions

MR and µCTA are valuable imaging tools for the morphological evaluation of cartilage in NHP models which in turn can be used for OA studies.

Use of magnetic capture to identify elevated levels of CCL2 following intra-articular injection of monoiodoacetate in rats

PURPOSE

Synovial fluid biomarkers help evaluate osteoarthritis (OA) development. Magnetic capture, our new magnetic nanoparticle-based technology, has proven to be effective for determining extracellular matrix fragment levels in two rat OA models. Here, the feasibility of magnetic capture for detecting monocyte chemoattractant protein-1 (MCP-1 or CCL2) is demonstrated after intra-articular injection of monoiodoacetate (MIA) in the rat knee.

METHODS

Forty-eight male Lewis rats received a right hind limb, intra-articular injection of MIA (1 mg in 25 µl of saline) or 25 µl of saline. Magnetic capture and lavage were performed at 7 days after injection (n = 6 per treatment per procedure), with magnetic capture additionally performed at 14 and 28 days post-injection (n = 6 per treatment per time point). CCL2 was also assessed in serum.

RESULTS

Serum CCL2 levels revealed no difference between MIA and saline animals (p = 0.0851). In contrast, magnetic capture and lavage detected a significant increase of CCL2 in the MIA-injected knee, with the MIA-injected knee having elevated CCL2 compared to contralateral and saline-injected knees (p = 0.00016 (contralateral) and p = 0.00016 (saline) for magnetic capture; p = 0.00023 (contralateral) and p = 0.00049 (saline) for lavage).

CONCLUSIONS

Magnetic capture of CCL2 was successfully developed and applied to determine levels of CCL2 in a rat knee. Magnetic capture detected a statistically significant increase of CCL2 in MIA-injected knees compared to controls, and CCL2 levels stayed relatively stable from week 1 through week 4 post-MIA injection.

Magnetic Capture of a Molecular Biomarker from Synovial Fluid in a Rat Model of Knee Osteoarthritis

Biomarker development for osteoarthritis (OA) often begins in rodent models, but can be limited by an inability to aspirate synovial fluid from a rodent stifle (similar to the human knee). To address this limitation, we have developed a magnetic nanoparticle-based technology to collect biomarkers from a rodent stifle, termed magnetic capture. Using a common OA biomarker--the c-terminus telopeptide of type II collagen (CTXII)--magnetic capture was optimized in vitro using bovine synovial fluid and then tested in a rat model of knee OA. Anti-CTXII antibodies were conjugated to the surface of superparamagnetic iron oxide-containing polymeric particles. Using these anti-CTXII particles, magnetic capture was able to estimate the level of CTXII in 25 μL aliquots of bovine synovial fluid; and under controlled conditions, this estimate was unaffected by synovial fluid viscosity. Following in vitro testing, anti-CTXII particles were tested in a rat monoiodoacetate model of knee OA. CTXII could be magnetically captured from a rodent stifle without the need to aspirate fluid and showed tenfold changes in CTXII levels from OA-affected joints relative to contralateral control joints. Combined, these data demonstrate the ability and sensitivity of magnetic capture for post-mortem analysis of OA biomarkers in the rat.

Biochemical markers of aging for longitudinal studies in humans

Much progress has been made in the past decades in unraveling the mechanisms that are responsible for aging. The discovery that particular gene mutations in experimental species such as yeast, flies, and nematodes are associated with longevity has led to many important insights into pathways that regulate aging processes. However, extrapolating laboratory findings in experimental species to knowledge that is valid for the complexity of human physiology remains a major challenge. Apart from the restricted experimental possibilities, studying aging in humans is further complicated by the development of various age-related diseases. The availability of a set of biomarkers that really reflect underlying aging processes would be of much value in disentangling age-associated pathology from specific aging mechanisms. In this review, we survey the literature to identify promising biochemical markers of aging, with a particular focus on using them in longitudinal studies of aging in humans that entail repeated measurements on easily obtainable material, such as blood samples. Our search strategy was a 2-pronged approach, one focused on general mechanisms of aging and one including studies on clinical biomarkers of age-related diseases.

Applications of proteomics to osteoarthritis, a musculoskeletal disease characterized by aging

The incidence of age-related musculoskeletal impairment is steadily rising throughout the world. Musculoskeletal conditions are closely linked with aging and inflammation. They are leading causes of morbidity and disability in man and beast. Aging is a major contributor to musculoskeletal degeneration and the development of osteoarthritis (OA). OA is a degenerative disease that involves structural changes to joint tissues including synovial inflammation, catabolic destruction of articular cartilage and alterations in subchondral bone. Cartilage degradation and structural changes in subchondral bone result in the production of fragments of extracellular matrix molecules. Some of these biochemical markers or "biomarkers" can be detected in blood, serum, synovial fluid, and urine and may be useful markers of disease progression. The ability to detect biomarkers of cartilage degradation in body fluids may enable clinicians to diagnose sub-clinical OA as well as determining the course of disease progression. New biomarkers that indicate early responses of the joint cartilage to degeneration will be useful in detecting early, pre-radiographic changes. Systems biology is increasingly applied in basic cartilage biology and OA research. Proteomic techniques have the potential to improve our understanding of OA physiopathology and its underlying mechanisms. Proteomics can also facilitate the discovery of disease-specific biomarkers and help identify new therapeutic targets. Proteomic studies of cartilage and other joint tissues may be particularly relevant in diagnostic orthopedics and therapeutic research. This perspective article discusses the relevance and potential of proteomics for studying age-related musculoskeletal diseases such as OA and reviews the contributions of key investigators in the field.

Effect of a glucosamine-based combination supplement containing chondroitin sulfate and antioxidant micronutrients in subjects with symptomatic knee osteoarthritis: A pilot study

In the present study, we aimed to investigate the potential effect of a glucosamine (1,200 mg/day)-based dietary supplement combined with chondroitin sulfate and three antioxidant micronutrients, namely methylsulfonylmethane, guava leaf extract, and vitamin D (test supplement) on osteoarthritis (OA) of the knee. A 16-week, randomized, double-blinded, placebo-controlled trial was conducted involving 32 subjects with symptomatic knee OA. Clinical outcomes were measured using the Japanese Knee Osteoarthritis Measure (JKOM) for symptoms and a study diary-based visual analog scale (diary VAS) for pain at baseline and at weeks 4, 8, 12 and 16 during the 16-week intervention period. Furthermore, biomarkers for cartilage type II collagen degradation (C2C) and synovitis hyaluronan (HA) were measured. As compared with the baseline, the JKOM pain subscale was significantly improved at all of the four assessment time points in the test group, but was not at any time point in the placebo group. On the other hand, all of the four symptom subscales and the aggregated total symptoms were significantly improved in the two groups at one or more time points. However, all of these clinical improvements were greater in extent in the test group than in the placebo group, and there were significant differences between groups in the magnitude of changes from baseline for one subscale 'general activities' and the aggregated total symptoms at week 8 (P<0.05). The results of efficacy assessments with the diary VAS showed that all of the three pain subscales were significantly improved only in the test group at almost all the time points. Moreover, serum levels of C2C and HA were decreased by 10 and 25%, respectively, at week 16 in the test group, albeit not statistically significant, without any detectable changes in the placebo group. In conclusion, although the results obtained in this study were not conclusive, the tested glucosamine-based combination supplement is likely to have a beneficial effect on pain and other symptoms associated with knee OA.

High throughput proteomic analysis of the secretome in an explant model of articular cartilage inflammation

This study employed a targeted high-throughput proteomic approach to identify the major proteins present in the secretome of articular cartilage. Explants from equine metacarpophalangeal joints were incubated alone or with interleukin-1beta (IL-1β, 10ng/ml), with or without carprofen, a non-steroidal anti-inflammatory drug, for six days. After tryptic digestion of culture medium supernatants, resulting peptides were separated by HPLC and detected in a Bruker amaZon ion trap instrument. The five most abundant peptides in each MS scan were fragmented and the fragmentation patterns compared to mammalian entries in the Swiss-Prot database, using the Mascot search engine. Tryptic peptides originating from aggrecan core protein, cartilage oligomeric matrix protein (COMP), fibronectin, fibromodulin, thrombospondin-1 (TSP-1), clusterin (CLU), cartilage intermediate layer protein-1 (CILP-1), chondroadherin (CHAD) and matrix metalloproteinases MMP-1 and MMP-3 were detected. Quantitative western blotting confirmed the presence of CILP-1, CLU, MMP-1, MMP-3 and TSP-1. Treatment with IL-1β increased MMP-1, MMP-3 and TSP-1 and decreased the CLU precursor but did not affect CILP-1 and CLU levels. Many of the proteins identified have well-established extracellular matrix functions and are involved in early repair/stress responses in cartilage. This high throughput approach may be used to study the changes that occur in the early stages of osteoarthritis.

Cartilage oligomeric matrix protein - inflammation biomarker in knee osteoarthritis

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

Association between synovial fluid levels of aggrecan ARGS fragments and radiographic progression in knee osteoarthritis

Introduction

Aggrecanase cleavage at the ³⁹²Glu-³⁹³Ala bond in the interglobular domain (IGD) of aggrecan, releasing N-terminal ³⁹³ARGS fragments, is an early key event in arthritis and joint injuries. We determined whether synovial fluid (SF) levels of ARGS-aggrecan distinguish subjects with progressive radiographic knee osteoarthritis (ROA) from those with stable or no ROA.

Methods

We studied 141 subjects who, at examination A, had been given meniscectomies an average of 18 years earlier (range, 15 to 22 years). Seventeen individuals without surgery, and without known injury to the menisci or cruciate ligaments, were used as references. At examinations A and B, with a mean follow-up time of 7.5 years, we obtained SF and standing tibiofemoral and skyline patellofemoral radiographs. SF ARGS-aggrecan was measured with an electrochemiluminescence immunoassay, and we graded radiographs according to the OARSI atlas. The association between SF ARGS levels at examination A and progression of radiographic features of knee OA between examinations A and B was assessed by using logistic regression adjusted for age, gender, body mass index, and time between examinations, and stratified by ROA status at examination A.

Results

We found a weak negative association between SF ARGS concentrations and loss of joint space: the likelihood of progression of radiographic joint space narrowing decreased 0.9 times per picomole per milliliter increase in ARGS (odds ratio (OR) 0.89; 95% confidence interval (CI), 0.79 to 0.996). In subjects with and without preexisting ROA at examination A, the association was OR, 0.96; 0.81 to 1.13; and 0.77; 0.62 to 0.95, respectively. Average levels of SF ARGS 18 years after meniscectomy were no different from those of reference subjects and were not correlated to radiographic status at examination A.

Conclusions

In subjects with previous knee meniscectomy but without ROA, levels of SF ARGS-aggrecan were weakly and inversely associated with increased loss of joint space over a period of 7.5 years.

Significance of the serum CTX-II level in an osteoarthritis animal model: a 5-month longitudinal study

OBJECTIVE

The aim of this study was to investigate the clinical value of serum measurement of C-telopeptide of type II collagen (CTX-II). In correlation with late stages of osteoarthritis (OA) evaluated with histological assessment, the evolution of serum CTX-II concentration was followed during a 20-week longitudinal study in rabbit anterior cruciate ligament transection (ACLT) OA model in adult and growing animals.

METHODS

OA was induced in five adult and nine growing rabbits. Four adult and four young rabbits were unoperated. Serum sampling was made at week 0, 1, 2, 3, 4, 6, 8, 10, 12, 14, 16 and 20 after the surgery in all rabbits. Animals were euthanized 20 weeks after the surgery. Serum CTX-II levels were analyzed with a recently available enzyme-linked immunosorbent assay (ELISA) kit, the protocol of which has been modified to increase the sensitivity of the test.

RESULTS

Significant differences for the CTX-II levels at W3, W6, W8, W10, W12, W14, W16 and W20 were observed between the adult ACLT and the control groups. A negative correlation between CTX-II levels and cartilage thickness of the medial compartment of the knee at W8, W10, W12 and a positive correlation between the CTX-II levels and the histomorphological score of the medial compartment of the knee at W3, W6, W8, W10, W12 were noted in adult animals. In young animals, operated or not, we observed high CTX-II levels at the beginning of the study, which decreased until the end.

CONCLUSION

Our results suggest the interest of the serum CTX-II monitoring for the OA progression and the relevance of the multiple time point analysis of this biomarker. Moreover, they address the question of the importance of correctly choosing the age of the animals used in the pre-clinical studies of OA.

[Detection of bone erosions in knee osteoarthrosis by serum biomarkers]

INTRODUCTION

Osteoarthrosis (OA) is a degenerative chronic disease characterized by destruction of joint articular cartilage and subchondral bone with formation of osteophytes and usuries on joint surface. Quantitative and dynamic changes in remodeling of joint tissue reflect matrix molecules that dismiss as fragments in joint liquid, blood and urine where they can be detected. Human cartilage glycoprotein (YKL-40) is synthesised by chondrocytes and synovial cells and plays a significant role in remodel tissue.

OBJECTIVE

The aim of the paper was the parallel analysis and determination of the degree of correlation between ultrasound indicators destruction of joints, bone erosion (usuries), and serum YKL-40 concentrations in patients with primary osteoarthrosis of the knee.

METHODS

The analysis included 88 patients with the diagnosis of knee OA. Ultrasound review of knees was done by two rheumatologists. The analysis of serum samples determined the concentration of YKL40 by ELISA method.

RESULTS

The average age of patients was 69.97 +/- 9.37 years, duration of knee OA 6.46 +/- 6.73 years. The mean value of age in 59 patients with usuries was 72.05 +/- 7.74, at 29 without usuries 65.75 +/- 11.00 (p = 0.003). The average value (median) thickness cartilage in medial condyl femur (front access) in patients with usuries was 1.25 mm (1.12-1.36 mm), without usuries 1.35 mm (1.20-1.51 mm) (p = 0.016). The central YKL40 value of biomarkers in the patients without usuries was 81 ng/ml (46.5-120.5 ng/ml), with usuries the medial condyil 138 ng/ml (89.5-175.0 ng/ml), the lateral 106 ng/ml (63.0-201.5 ng/ml) and both condyl 86 ng/ ml (69.75-140.5 ng/ml) (p = 0.004). The central value YKL40 after 5 year-duration of disease was 83.68 +/- 33.65 ng/ml, after 10 years 138.22 +/- 48.88 ng/ml, after 15 years 209.30 +/- 79.36 ng/ml, and after 20 years 218.50 +/- 106.51 ng/ml (p = 0.000). The biomarker YKL 40 may be a marker for usuries (area 0.691, p = 0.004; confidence interval 0.574-0.808). If you took the optimal cut-off of 84.5 ng/ml, then YKL40 sensitivity to the usuries was 69.5%, and specificity 51.7%.

CONCLUSION

Increased concentrations of biomarkers YKL40 may be an indicator of the degree of destructive changes in the knee osteoarthrosis.

[Arthrosonography and biomarkers in the evaluation of destructive knee cartilage osteoarthrosis]

INTRODUCTION

Knee osteoarthrosis (OA) is a degenerative disease with progressive loss of cartilage of joints and bone destruction. During this process, the release of fragments of connective tissue matrix is detected in the biological fluids such as human cartilage glycoprotein (YKL-40), cartilage oligomeric matrix protein (COMP) and collagen type I C terminal telopeptid (CTX-I).

OBJECTIVE

The aim of the study was to determine the degree of connection cartilage thickness measured by ultrasound with serum concentrations of biomarkers YKL-40, COMP and CTX-I in patients with primary knee OA.

METHODS

The analysis included 88 patients with the diagnosis of knee OA. Ultrasound examination of knees were done by two rheumatologists. The analysis of serum samples determined the concentration of COMP, YKL-40 and CTX-I by the ELISA method.

RESULTS

The average age of patients was 69.97 +/- 9.37 years and the duration of knee OA 6.46 +/- 6.73 years. The average cartilage thickness of the femoral condyle was 1.33 +/- 0.20 mm; of the medial condyle (MC) (front access) 1.30 +/- 0.23 mm, (rear access) 1.30 +/- 0.29 mm and lateral condyli (LC) (front access) 1.39 +/- 0.27 mm. The average cartilage thickness of MC (front access) was 1.27 mm (0.98-1.42 mm), (rear access) 1.27 mm (0.84-1.46 mm) and LC (front access) 1.36 mm (1.01-1.57 mm) (p = 0.002). There was a significant connection in the negative direction between the patients' age and the cartilage thickness of MC (front and rear access) and LC (front access) (r = -0.253; p = 0.017). There was a significant negative direction of interrelationship between the cartilage thickness of MC (front access) (r = -0.259; p = 0.015) and LC (front access) and the disease duration (r = -0.259; p = 0.015). In patients with knee OA lasting for 5 years the measured cartilage thickness was 1.27 mm (1.16-1.49 mm), and 0.99 mm (0.94-1.23 mm) (p = 0.007) in those lasting for 20 years. There was a significant relationship in a negative direction between the concentration of YKL-40 and cartilage thickness of MC (front access) (r = -0.249; p = 0.019).

CONCLUSION

The progressive loss of cartilage during the long-term evolution of osteoarthrosis is most extensive in the femoral MC. The increased serum levels of YKL-40 can be a good indicator of joint cartilage destruction.

Decreased physical function and increased pain sensitivity in mice deficient for type IX collagen

OBJECTIVE

In mice with Col9a1 gene inactivation (Col9a1(-/-)), osteoarthritis (OA) and intervertebral disc degeneration develop prematurely. The aim of this study was to investigate Col9a1(-/-) mice for functional and symptomatic changes that may be associated with these pathologies.

METHODS

Col9a1(-/-) and wild-type mice were investigated for reflexes, functional impairment (beam walking, pole climbing, wire hang, grip strength), sensorimotor skills (rotarod), mechanical sensitivity (von Frey hair), and thermal sensitivity (hot plate/tail flick). Gait was also analyzed to determine velocity, stride frequency, symmetry, percentage stance time, stride length, and step width. Postmortem, sera obtained from the mice were analyzed for hyaluronan, and their knees and spines were graded histologically for degeneration.

RESULTS

Col9a1(-/-) mice had compensatory gait changes, increased mechanical sensitivity, and impaired physical ability. Col9a1(-/-) mice ambulated with gaits characterized by increased percentage stance times and shorter stride lengths. These mice also had heightened mechanical sensitivity and were deficient in contact righting, wire hang, rotarod, and pole climbing tasks. Male Col9a1(-/-) mice had the highest mean serum hyaluronan levels and strong histologic evidence of cartilage erosion. Intervertebral disc degeneration was also detected, with Col9a1(-/-) mice having an increased incidence of disc tears.

CONCLUSION

These data describe a Col9a1(-/-) behavioral phenotype characterized by altered gait, increased mechanical sensitivity, and impaired function. These gait and functional differences suggest that Col9a1(-/-) mice select locomotive behaviors that limit joint loads. The nature and magnitude of behavioral changes were largest in male mice, which also had the greatest evidence of knee degeneration. These findings suggest that Col9a1(-/-) mice present behavioral changes consistent with anatomic signs of OA and intervertebral disc degeneration.

Human cartilage glycoprotein 39--biomarker of joint damage in knee osteoarthritis

Human glycoprotein of cartilage (YKL-40) synthesizes chondrocytes and synovial cells in inflammatory conditions or remodels the outer cell matrix in osteoarthritis. The aim of this study was to conduct a parallel analysis between thickness of cartilage and length of osteophytes, ultrasound indicators of joint destruction, with levels of YKL-40 in serum in patients with primary osteoarthritis. Ultrasound findings and concentration of YKL-40(ng/ml) were examined in 88 patients. The average value cartilage thickness measured on medial condyles of the femur was 1.30 +/- 0.23 mm and on lateral was 1.39 +/- 0.27 mm. Median YKL-40 in patients with shorter osteophytes was 62.0 (44.5-90) ng/ml, and with longer osteophytes was 119 (range 80-171) ng/ml (p = 0.000). YKL-40 can be a marker for the appearance of longer osteophytes (sensitivity = 79.1%; specificity = 61.9%; cut off = 75.0 ng/ml). The duration of illness is very much connected to values of YKL-40 (r = 0.651, p = 0.000). After an illness duration of five years, the concentration of YKL-40 was 83.68 +/- 33.65 ng/ml, after ten years it was 138.22 +/- 48.88 ng/ml, and after 15 and 20 years it was 209.30 +/- 79.36 ng/ml and 218.50 +/- 106.51 ng/ml, respectively. Higher concentrations of YKL-40 indicate the level of cartilage destruction and can be used for assessment of destruction.

Serum protein signatures detect early radiographic osteoarthritis

OBJECTIVE

To test the hypothesis that early knee and hand osteoarthritis (OA) development is characterized by detectable changes in serum proteins relevant to inflammation, cell growth, activation, and metabolism several years before OA becomes radiographically evident.

METHODS

Using microarray platforms that simultaneously test 169 proteins relevant to inflammation, cell growth, activation and metabolism, we conducted a case-control study nested within the Baltimore Longitudinal Study of Aging (BLSA). Subjects included 22 incident cases of OA and 66 age-, sex- and body mass index (BMI)-matched controls. Serum samples tested were obtained at the time of radiographic classification as either case or control, and up to 10 years earlier at a time when all participants were free of radiographic OA. Proteins with mean signal intensities fourfold higher than background were compared between cases and controls using multivariate techniques.

RESULTS

Sixteen proteins were different between OA cases compared to controls. Four of these proteins [matrix metalloproteinase (MMP)-7, interleukin (IL)-15, plasminogen activator inhibitor (PAI)-1 and soluble vascular adhesion protein (sVAP)-1] were already different in samples obtained 10 years before radiographic classification and remained different at the time of diagnosis. Six additional proteins were only associated with subsequent OA development and not with established OA.

CONCLUSIONS

Changes in serum proteins implicated in matrix degradation, cell activation, inflammation and bone collagen degradation products accompany early OA development and can precede radiographic detection by several years.

Novel synovial fluid recovery method allows for quantification of a marker of arthritis in mice

OBJECTIVE

We evaluated three methodologies--a calcium sodium alginate compound (CSAC), polyacrylate beads (PABs), and Whatman paper recovery (WPR)--for the ability to recover synovial fluid (SF) from mouse knees in a manner that facilitated biochemical marker analysis.

METHODS

Pilot testing of each of these recovery vehicles was conducted using small volumes of waste human SF. CSAC emerged as the method of choice, and was used to recover and quantify SF from the knees of C57BL/6 mice (n=12), six of which were given left knee articular fractures. SF concentrations of cartilage oligomeric matrix protein (COMP) were measured by enzyme-linked immunosorbent assay.

RESULTS

The mean concentration ratio [(COMP(left knee))/(COMP(right knee))] was higher in the mice subjected to articular fracture when compared to the non-fracture mice (P=0.026). The mean total COMP ratio (taking into account the quantitative recovery of SF) best discriminated between fracture and non-fracture knees (P=0.004).

CONCLUSIONS

Our results provide the first direct evidence of accelerated joint tissue turnover in a mouse model responding to acute joint injury. These data strongly suggest that mouse SF recovery is feasible and that biomarker analysis of collected SF samples can augment traditional histological analyses in mouse models of arthritis.

Degeneration, inflammation, regeneration, and pain/disability in dogs following destabilization or articular cartilage grooving of the stifle joint

OBJECTIVE

The most used model for joint instability is the canine anterior cruciate ligament transection (ACLT)-model. The ACLT-model can be extended with a medial meniscectomy (MX) (i.e., ACLT-MX-model) to avoid unintentional, and with that variable, meniscal damage. The present study compares the ACLT-MX-model with the more recently introduced Groove-model on longitudinal measurements of osteophyte formation and gait as a surrogate marker of pain and disability, in addition to structural endpoint parameters.

METHODS

Degenerative joint damage was induced Labrador dogs according to the ACLT-MX-model (n=7) or Groove-model (n=7). Every 4 weeks radiographs were taken to analyze osteophyte formation. Every 2 weeks gait was recorded using force-plate analysis. Joints were analyzed for features of degeneration 12 weeks after surgery.

RESULTS

Both models showed similar osteophyte formation and gait changes for both experimental and contra-lateral control joints, although more pronounced for the ACLT-MX-model. This was supported by the structural endpoint measurements. Cartilage integrity, chondrocyte activity and synovial inflammation revealed similar characteristics of degenerative joint disease in both groups, again more pronounced in the ACLT-MX-model.

CONCLUSIONS

The ACLT-MX-model demonstrates characteristics of joint degeneration that are related to moderate to severe osteoarthritis with clear synovial inflammatory activity. The Groove-model is a less painful and a significantly milder model of joint degeneration. The latter model might be more suitable to study subtle changes as a result of intervention than the more robust ACLT-MX-model.

The type II collagen fragments Helix-II and CTX-II reveal different enzymatic pathways of human cartilage collagen degradation

OBJECTIVE

Cartilage degradation in osteoarthritis (OA) generates the type II collagen fragments, Helix-II and CTX-II that can be used as clinical biological markers. Helix-II and C-telopeptide of type II collagen (CTX-II) levels are associated independently with progression of OA suggesting that they may be generated through different collagenolytic pathways. In this study we analyzed the release of Helix-II and CTX-II from human cartilage collagen by the proteinases reported to play a role in cartilage degradation.

METHODS

In vitro, human articular cartilage extract was incubated with activated human recombinant cathepsins (Cats) and matrix-metalloproteases (MMPs). Next, we analyzed the spontaneous release of Helix-II and CTX-II from cartilage sections of patients with knee OA who were immediately deep frozen after joint replacement to preserve endogenous enzyme activity until assay. Cartilage sections were then incubated for up to 84 h in the presence or absence of E-64 and GM6001, inhibitors of cysteine proteases and MMPs, respectively.

RESULTS

In vitro, Cats K, L and S generated large amount of Helix-II, but not CTX-II. Cat B generated CTX-II fragment, but destroyed Helix-II immunoreactivity. Cat D was unable to digest intact cartilage. MMPs-1, -3, -7, -9, and -13 efficiently released CTX-II, but only small amount of Helix-II. Neither CTX-II nor Helix-II alone was able to reflect accurately the collagenolytic activity of Cats and MMPs as reflected by the release of hydroxyproline. In OA cartilage explants, E-64 blunted the release of Helix-II whereas the release of CTX-II could be completely abrogated by GM6001 and only partly by E-64.

CONCLUSION

These in vitro and ex vivo experiments of human cartilage suggest that Helix-II and CTX-II could be released in part by different enzymatic pathways. Helix-II and CTX-II alone reflect only partially overall cartilage collagen degradation. These findings may explain why these two biological markers could provide complementary information on disease progression in OA.

An update on osteoarthritis therapeutics

PURPOSE OF REVIEW

This review addresses recent major developments in symptomatic therapy and the principles of disease modification in osteoarthritis. It emphasizes issues that are of importance to the practicing clinician at a time when researchers in the field are trying to improve ways not only to provide symptomatic relief but also to slow disease progression.

RECENT FINDINGS

The past year has led to a reassessment of the role of cyclo-oxygenase-2 inhibitors in osteoarthritis therapy and has yielded new information on nutriceuticals such as glucosamine. The relative efficacy of intra-articular injections of agents such as corticosteroid and hyaluronic acid preparations has been assessed. In addition, reports on trials of potentially disease-modifying agents for osteoarthritis have been published.

SUMMARY

Because the therapeutic options have been reduced over the past year and the role of nutritional supplements remains unclear, the clinician is faced with a need to reassess osteoarthritis therapy. Although no practical disease-modifying agent for osteoarthritis has been identified, reports such as the recent doxycycline trial reviewed herein provide hope that continued research will soon yield a therapeutic model similar to that used in rheumatoid arthritis, for which some therapeutic agents achieve disease modification and other agents can be added as needed for symptomatic relief.

The chemical biomarkers C2C, Coll2-1, and Coll2-1NO2 provide complementary information on type II collagen catabolism in healthy and osteoarthritic mice

OBJECTIVE

Compared with wild-type (WT) mice, biglycan/fibromodulin double-deficient mice develop severe knee osteoarthritis. We undertook this study to compare type II collagen catabolism in the 2 genotypes and to compare the usefulness of 3 biomarkers of collagen degradation (C2C [also known as Col2-3/4C(long mono)] as well as the peptide Coll2-1 and its nitrated form, Coll2-1NO2) for evaluating collagen catabolism in vivo.

METHODS

In 15 WT mice and 15 biglycan/fibromodulin double-deficient mice, we determined serum levels of C2C at ages 66 and 141 days, and we determined serum levels of Coll2-1 and Coll2-1NO2 at ages 49, 81, 95, and 141 days. Expression of the biomarkers in knee sections was examined using immunohistochemistry.

RESULTS

The mean concentrations of C2C and Coll2-1 were higher in biglycan/fibromodulin double-deficient mice at all time points. For C2C and Coll2-1, the ratio of the serum concentration in biglycan/fibromodulin double-deficient mice to that in WT mice (the double-deficient:WT ratio) was constant over time and was approximately 1.63 and approximately 1.15, respectively. In contrast, the double-deficient:WT ratio for Coll2-1NO2 varied and, depending on age, was >1 or <1. No significant correlation was found between the expression of the different biomarkers, except for a weak, negative correlation between Coll2-1NO2 and C2C. In both genotypes, antibodies to each biomarker labeled some fibroblasts in the tendons and menisci as well as chondrocytes above the tidemark in articular cartilage. Growth plates were unstained. For each biomarker, extracellular staining was limited to fibrocartilage areas in the tendons and menisci in all mice and was limited to some focal lesions of the cartilage in biglycan/fibromodulin double-deficient mice.

CONCLUSION

The different double-deficient:WT ratios observed with C2C, Coll2-1, and Coll2-1NO2 in the absence of any correlation between the expression of the 3 biomarkers indicate that these biomarkers give complementary, rather than redundant, information about in vivo type II collagen catabolism.

Effect of chondroitin sulphate in symptomatic knee osteoarthritis: a multicentre, randomised, double-blind, placebo-controlled study

OBJECTIVE

To evaluate the efficacy and tolerability of chondroitin sulphate (chondroitin sulphate) in knee osteoarthritis.

PATIENTS AND METHODS

A 24-week, randomised placebo-controlled trial of chondroitin sulphate (1 g/day) in patients with symptomatic knee osteoarthritis as measured on a visual analogue scale. Pain on daily activities and Lequesne's Index were the primary efficacy criteria. Secondary outcomes included the rate of responders according to the outcome measures in rheumatoid arthritis clinical trials of the Osteoarthritis Research Society International (OMERACT-OARSI) criteria, quality of life, patient's/physician's global assessments and carry-over effect after treatment. Biochemical markers of bone (CTX-I), cartilage (CTX-II) and synovium (hyaluronic acid) metabolism were also measured. Safety was assessed by recording adverse events (AEs). Statistical analysis was performed on the inter-group differences in the intention-to-treat population.

RESULTS

307 patients were included in the study. 28 (9%) patients discontinued the study because of lack of efficacy or AEs. At the end of treatment, the decrease in pain was -26.2 (24.9) and -19.9 (23.5) mm and improved function was -2.4 (3.4) (-25%) and -1.7 (3.3) (-17%) in the chondroitin sulphate and placebo groups, respectively (p = 0.029 and 0.109). The OMERACT-OARSI responder rate was 68% in the chondroitin sulphate and 56% in the placebo group (p = 0.03). The investigator's assessments and short form 12 (SF-12) physical component reported improvement more frequently in the chondroitin sulphate than in the placebo group (p = 0.044 and 0.021, respectively). No significant difference was observed between treatment groups for changes in biomarkers over 24 weeks. However, there was a significant difference between non-responders and responders according to the OARSI criteria for 24-week changes of CTX-I (p = 0.018) and CTX-II (p = 0.014). Tolerance was considered to be satisfactory.

CONCLUSION

This study failed to show an efficacy of chondroitin sulphate on the two primary criteria considered together, although chondroitin sulphate was slightly more effective than placebo on pain, OMERACT-OARSI response rate, investigator's assessment and quality of life.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Increased urinary type II collagen helical and C telopeptide levels are independently associated with a rapidly destructive hip osteoarthritis

OBJECTIVES

Biochemical markers reflecting the degradation of the type II collagen helical (Helix-II) and type II collagen C telopeptides (CTX-II) have been developed.

AIM

To investigate the association of rapidly destructive hip osteoarthritis with urinary Helix-II and urinary CTX-II.

PATIENTS AND METHODS

12 patients (mean age 70 years) meeting the criteria for rapidly destructive hip osteoarthritis and 28 patients with slowly progressive hip osteoarthritis (mean age 63 years) defined as <0.20 mm joint space loss/year were included in a case-control study. In each patient, urinary Helix-II and CTX-II were measured at the end of the follow-up period, with retrospective evaluation of x rays.

RESULTS

Helix-II levels were 41% (p = 0.002) higher in the 40 patients with hip osteoarthritis than in 75 healthy controls. Increased Helix-II levels were associated with decreased minimum joint space width of the hip (r = -0.57, p = 0.001). Mean urinary Helix-II levels were 71% higher in rapidly destructive than in slowly progressive disease (mean (standard deviation (SD)) ng/mmol Cr: 396 (160) v 232 (118) ng/mmol; p = 0.002). When levels of Helix-II and CTX-II in the highest tertile were both included in a multivariate logistic regression model, high Helix-II level (OR; (95% CI) 5.73 (1.01 to 32.8)) after adjustment for age and body mass index and high CTX-II level (6.67 (1.14 to 39.0)) were, independently of each other, associated with a rapidly destructive disease.

CONCLUSION

Increased urinary Helix-II levels are associated with rapidly destructive hip osteoarthritis, independently of urinary CTX-II. Measurement of Helix-II, alone or in combination with CTX-II, could be useful for the clinical investigation of patients with hip osteoarthritis.

Chondrocyte genomics: implications for disease modification in osteoarthritis

Advances in genomic technologies have made genome-wide-association and gene-expression studies a reality. Despite technical and analytical challenges, the application of genomic technologies to osteoarthritis research will lead to a better understanding of the disease at the molecular level. Functional genomics will identify genes involved in the chondrocyte response to cartilage injury and cartilage repair, and will help clarify the role of chondrocytes in arthritis onset, progression and outcome. Systems biology will enable researchers to develop a full portrait of osteoarthritis, a complex and multifactorial disease that involves not only articular cartilage but also synovium, synovial fluid, subchondral bone and peripheral blood. Ultimately such an approach will result in novel diagnostic and therapeutic targets and better disease management.

New biochemical markers of osteoarthritis

Osteoarthritis is characterized by the progressive destruction of articular cartilage and subchondral bone and synovial reaction. Radiological findings that form the basis of the diagnosis of osteoarthritis are poorly sensitive for detecting early disease and monitoring progression of joint damage. New specific and sensitive biochemical markers of cartilage and synovial tissue turnover, including assays for Type II collagen synthesis and degradation, have been developed. Recent prospective studies indicate that blood and urine levels of these new markers are associated with the progression of joint damage. Biological markers respond rapidly to treatment, and thus will certainly play an important role in the development and monitoring of disease-modifying therapies. As osteoarthritis involves different tissues and complex biological processes, a combination of different biochemical markers appears to be the most promising diagnostic strategy.

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

OBJECTIVE

To monitor changes in serum concentrations of cartilage oligomeric matrix protein (COMP) during a 24-h period to determine any diurnal variation, and to estimate the half life of COMP in the circulation in patients with symptomatic knee osteoarthritis and in those with rheumatoid arthritis.

METHODS

Serum samples were drawn every 4 h (7 samples/patient over 24 h) in 10 patients with knee osteoarthritis and 14 patients with rheumatoid arthritis. Osteoarthritis was defined radiographically and clinically (American College of Rheumatology (ACR) criteria) and rheumatoid arthritis according to the 1987 ACR criteria. Serum COMP was measured by sandwich ELISA. A statistical model for the diurnal variation in the COMP levels was developed using the computer program NONMEM.

RESULTS

No considerable changes in COMP levels were observed during the day between 08:00 and 21:00 in either group. A significant decrease in serum COMP was apparent during bed rest at night, reaching the lowest levels between 04:00 and 05:00 (p<0.03 or better v all other time points) in patients with osteoarthritis and in those with rheumatoid arthritis. From the rate of decreasing serum COMP levels, a putative half life of COMP in the circulation was estimated to be 7.4 h.

CONCLUSION

During normal daytime activities, serum COMP levels are constant. The decrease during the night indicates a rapid elimination of COMP once it has reached the circulation. The stable COMP levels during the day suggest that it is not necessary to further standardise the time of serum sampling in clinical practice.

Usurped SLRPs: novel arthritis biomarkers exposed by catabolism of small leucine-rich proteoglycans?

Proteolytic degradation of articular cartilage macromolecules, including the large aggregating cartilage proteoglycan (aggrecan) and small leucine-rich proteoglycans (SLRPs), is a prominent pathophysiological feature of arthritic diseases such as osteoarthritis (OA). Molecular profiling and monitoring of soluble/circulating proteoglycan catabolites that may be released from the cartilage matrix therefore represents an attractive strategy for evaluating OA disease progression and intervention. The recent identification of discrete metalloproteinase-sensitive SLRP cleavage sites, and complementary neoepitope-bearing SLRP catabolites, extends decisive insight into the functional regulation of extracellular matrix integrity, and proffers poignant leads to assist in disclosing and appraising applicable biomarkers of cartilage degeneration during arthritis.