Serum keratan sulfate levels in rabbits with experimentally induced osteoarthritis

Use of synovial fluid markers of cartilage synthesis and turnover to study effects of repeated intra-articular administration of methylprednisolone acetate on articular cartilage in vivo

In vivo the effects of intra-articular (IA) corticosteroids on articular cartilage remain controversial. This study was designed to examine this issue using synovial fluid (SF) markers of cartilage metabolism. Paired radiocarpal joints, without clinical or radiographic signs of joint disease, were studied in 10 adult horses. Aseptic arthrocentesis was performed weekly for 13 weeks. IA injections of methylprednisolone acetate (MPA) into the treatment joint and the vehicle into the control joint were performed at weeks 3, 5 and 7. We used radioimmunoassays on SF samples which measure a keratan sulfate epitope (KS) and the 846 epitope on cartilage aggrecan (PG) and the C-propeptide (CPII) of cartilage type II procollagen which is released following synthesis of this molecule. Gel chromatography was performed on selected SF samples to evaluate the sizes of SF PG molecules. The total joint KS and the 846 epitopes were both present on a heterogeneous population of mainly molecules which, from chromotographic analysis, appeared to be mainly fragments of the articular cartilage aggrecan. They were significantly elevated in MPA joints whereas CPII was significantly reduced compared to the control during the treatment period. These results indicate that the repeated use of IA MPA leads to a potentially harmful inhibition of procollagen II synthesis and an increased release of degradation products of the PG aggrecan from articular cartilage.

Longitudinal characterization of synovial fluid biomarkers in the canine meniscectomy model of osteoarthritis

Damage to the meniscus can lead to posttraumatic osteoarthritis. Early markers of joint injury and tissue disease may be useful in developing and administering clinical treatment. We investigated the effects of total medial meniscectomy on biomarkers measured serially in synovial lavage fluid each month for 3 months. Following meniscectomy in dogs, four biomarkers were evaluated: cartilage oligomeric matrix protein, keratan sulfate epitope (5D4), the 3B3(-) neoepitope of chondroitin-6-sulfate, and the 3B3(+) chondroitinase-generated epitope of chondroitin-6-sulfate. Meniscectomy led to statistically significant elevations of all four biomarkers, with levels peaking at 4 weeks. By 12 weeks, the level of the 5D4 epitope returned to the preoperative baseline level whereas that of cartilage oligomeric matrix protein, 3B3(-), and 3B3(+) remained above the baseline. Concentrations of these biomarkers in the knees not operated on did not change significantly from the baseline. The levels of cartilage oligomeric matrix protein and 3B3(-) relative to 3B3(+) remained constant in all knees. In contrast, the level of 5D4 relative to 3B3(+) declined over time in the knee operated on but remained constant in the knee not operated on. These results demonstrate a quantitative change in the molecular components of synovial fluid after meniscectomy, as well as a qualitative change evinced by an alteration in the relative proportions of these epitopes. Extensive analyses showed a strong correlation between serum levels of 3B3(-) from the femoral and cephalic veins; however, serum 3B3(-) was not correlated with synovial fluid 3B3(-). These findings support the hypothesis that the concentrations of select cartilage biomarkers in synovial fluid are altered following meniscectomy and are promising tools for objectively monitoring the induction of osteoarthritis in this model system.

Biochemical markers in synovial fluid identify early osteoarthritis of the glenohumeral joint

The objective of this study on the glenohumeral joint was to assess the (1) accuracy of clinical diagnosis of osteoarthritis compared with arthroscopic diagnosis, and (2) the ability of biochemical markers in synovial fluid to detect osteoarthritis. Patients (96) were examined clinically and the preoperative diagnosis of osteoarthritis was recorded. At surgery (arthroscopy or arthroplasty), the glenohumeral joint was inspected for signs of osteoarthritis, and the joint osteoarthritis grade (I-IV) was recorded. At surgery, synovial fluid lavage was obtained from the joint, and later analyzed to determine levels of aggrecan components: total sulfated glycosaminoglycan and keratan sulfate epitope, link protein and the chondroitin sulfate epitope recognized by antibody 3B3 (3B3(-)). Compared with arthroscopic diagnosis of osteoarthritis, the results showed that the clinical diagnosis did not wrongly identify joints without osteoarthritis, and was always able to identify joints with advanced (Grade IV) osteoarthritis. Grade II osteoarthritis was rarely identified (10% of the time), and Grade III osteoarthritis was identified 50% of the time. Biochemical assessment of the synovial fluid showed that the catabolic markers (sulfated glycosaminoglycan, keratan sulfate and link protein) were elevated in fluids from joints with moderate (Grade III) and advanced osteoarthritis (Grade IV), and the 3B3(-) epitope was elevated in Grades II, III, and IV. These results show that arthroscopic diagnosis for osteoarthritis, of the glenohumeral joint is particularly useful for early and moderate osteoarthritis, where clinical (nonarthroscopic) diagnosis is poor, and that biochemical analysis of the synovial fluids corresponds well to arthroscopic diagnosis of shoulder osteoarthritis.

Changes in glycosaminoglycan epitope levels in knee joint fluid following injury

OBJECTIVE

To measure the levels of epitope on the chondroitin sulfate (CS) and keratan sulfate (KS) chains of proteoglycan fragments in synovial fluids from injured and contralateral uninjured knees of patients with traumatic cruciate ligament and/or meniscus damage.

METHODS

Enzyme-linked immunosorbent assays were used to determine the levels of monoclonal antibody epitopes 3-B-3 and 7-D-4 (CS), and 5-D-4 (KS), in paired joint fluids from the injured and uninjured knees of trauma patients.

RESULTS

Levels of the CS epitopes were increased in the trauma joint fluids from most patients, with higher levels of 3-B-3 epitope in 12 of the 16 patients, but the difference did not achieve significance; however, 7-D-4 levels were higher in 15 patients, and the difference was highly significant (P = 0.0005). In contrast, the KS epitope detected by 5-D-4 was decreased in 13 of 15 patients, and the difference was significant (P = 0.0074).

CONCLUSION

The increased level of 7-D-4 epitope on proteoglycans in joint fluid from injured knees may reflect the response of the articular cartilage to acute trauma resulting in altered expression of specific CS epitopes on cartilage proteoglycans. The fall in KS epitope levels may reflect the synthesis of proteoglycans that have lower KS content.

Measurement of glycosaminoglycans and keratan sulphate in canine arthropathies

Glycosaminoglycans (GAG) and keratan sulphate (KS) were measured in sera and synovial fluids from dogs with either osteoarthritis (OA) or rupture of the cranial cruciate ligament (CCL) and normal dogs. The dogs with OA had higher synovial fluid GAG levels (P < 0.002) and serum KS (P < 0.03) compared to the normal dogs. No significant differences in serum GAG were found in either group. In both OA and rupture of the CCL, GAG levels were increased in the synovial fluid from the affected joint compared with the clinically normal (inactive) contralateral joint. Neither GAG nor KS measurements correlated with serum and synovial fluid antibodies to collagen type II, synovial fluid white cell count or age of dog. It is unlikely that the measurement of these cartilage breakdown products is of value for diagnostic or prognostic use in canine arthropathies.

Levels of circulating tumor necrosis factor alpha and interleukin-6 in patients with rheumatoid arthritis. Relationship to serum levels of hyaluronan and antigenic keratan sulfate

OBJECTIVE

To measure serum levels of tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL-6) in patients with rheumatoid arthritis (RA) and age-matched control subjects and to study how these correlate with serum levels of hyaluronan (HA) and antigenic keratan sulfate (KS) and other biochemical as well as clinical indicators of disease activity.

METHODS

Immunoassays were used to measure levels of TNF alpha, IL-6, HA, and antigenic KS in the serum of 35 patients with RA and a group of age- and sex-matched control subjects. Clinical disease activity in the RA group was assessed using the Lansbury index. Drug intake was recorded and the erythrocyte sedimentation rate, and levels of fibrinogen, creatinine, bilirubin, alkaline phosphatase, lactate dehydrogenase, and aminotransferase were measured.

RESULTS

Serum levels of TNF alpha, IL-6, and HA were significantly higher in the RA population than in the control group. In patients with RA, serum levels of HA correlated positively with serum levels of TNF alpha and with clinical joint scores, but only weakly with other laboratory parameters of inflammation. Serum levels of antigenic KS correlated negatively with levels of circulating TNF alpha, but much more weakly with other clinical and biochemical parameters of disease activity.

CONCLUSION

These in vivo data support in vitro studies which have shown that TNF alpha is a potent stimulator of HA synthesis by synovial lining cells. The results strengthen the contention that serum HA may be a unique marker of synovial involvement and inflammation, rather than of only inflammation, in RA.

Age-related changes in glycosaminoglycan distribution in different anatomical sites on the surface of knee-joint articular cartilage in young rabbits

In spite of the fact that the various anatomical regions of a given articular cartilage surface are subjected to different degrees of stress, the present observations strongly suggest that there exists a topographical homogeneity in the distribution of glycosaminoglycans in the same articular cartilage. In contrast to this age-related changes in the proportion of the different types of glycosaminoglycan species in articular cartilage are remarkable. Non-sulphated chondroitin could only be detected in very young articular cartilage. Dermatan sulphate, which has already been detected in young adult rabbits, was followed by the appearance of keratan sulphate in older rabbits. Chondroitin 4-6-sulphates were detected in all articular cartilages studied, the proportion of the 6-sulphated variably increasing with age. The present report suggests that the distribution of glycosaminoglycans in articular cartilage varies with species and age, and the data can further vary, depending on the methods used. It is therefore concluded that generalizations against the results reported in the literature should be considered skeptically.

Antigenic properties of keratan sulfate: influence of antigen structure, monoclonal antibodies, and antibody valency

The influence of (a) antigen structure, (b) type of monoclonal antibody, and (c) antibody bivalency on the immunochemical detection and quantification of keratan sulfate (KS) from aggrecan has been studied. Apparent KS epitope levels were determined by immunoglobulin G (IgG)-enzyme-linked immunosorbent assay (ELISA) in preparations of human aggrecan and in a defined series of lower molecular weight proteoglycan preparations generated by proteolytic and alkali treatment of aggrecan. Gel filtration chromatography showed KS epitope to be preferentially detected in the higher molecular weight fragments of the preparations. In single KS chains the epitope was detected in the chains of higher M(r). The ability of the proteoglycan to inhibit in the IgG-ELISA decreased with a reduction in proteoglycan fragment size, ranging between 6- and 260-fold, depending on the antibody used. This was considered to be a cooperative binding effect. With most antibodies, the sensitivity of the IgG-ELISA (represented by the steepness of the inhibition slope) was also reduced with smaller inhibitor sizes. The lowest limit of detectability (the amount of KS required to generate 20% inhibition) varied by up to 60-fold depending on the antibody used. The use of monovalent Fab fragments instead of the whole IgG anti-KS antibody in the ELISA showed that the bivalency of the antibody also affected the quantitation of the assay. In the Fab-ELISA the assay was found to have an increased detectability (by 9.5-fold with aggrecan as the inhibitor), and the proteoglycan fragments and aggrecan all generated parallel inhibition curves. Although the Fab-ELISA was somewhat influenced by the structural presentation of the KS, this was not apparent for small fragments and single chains. Thus the effects of cooperative binding and antibody valency could be overcome and quantitative data could be obtained for all samples, using papain-digested samples and the Fab-ELISA. Application of this assay to analysis of body fluids showed the KS-containing fragments in synovial fluid, serum, and urine were of different sizes and could be quantified.

Serum keratan sulfate. Quantitative and qualitative comparisons in inflammatory versus noninflammatory arthritides

The concentration of keratan sulfate (KS) epitope was measured in the serum of patients with osteoarthritis (OA) or rheumatoid arthritis (RA) by enzyme-linked immunosorbent assay and compared with that in the serum of patients with primary fibromyalgia syndrome (PFS) and of controls who had no joint disease. By Student's tau-test, the mean serum KS concentrations in OA and RA patients measured with monoclonal antibodies (MAb) 5-D-4 and 2-D-3 were significantly increased over those in the PFS and normal groups; similar findings were observed using a nonparametric test, except that levels in RA patients showed no difference from those in PFS patients and normal subjects. There was no significant correlation between joint scores or disease duration and KS levels in OA or RA patients. Gel filtration of sera revealed mainly large, polydisperse KS-bearing fragments which eluted in a broad profile. KS purified from sera by immunoaffinity chromatography consisted mainly of high-density proteoglycans. Electrophoresis of pooled high-density KS fractions in polyacrylamide-agarose gels followed by Western blotting with MAb 5-D-4 showed diffuse bands with relative mobilities corresponding to large proteoglycans. These findings are consistent with attachment of KS to protein core fragments of various sizes; KS in patient sera is comparable in size with that in normal sera. Elevations of serum KS levels occur in the presence of cartilage degradation, but do not quantitatively define the extent or duration of articular involvement.

Glycosaminoglycan concentrations in horse plasma and serum. Differences with other animal species and identification of affecting factors

1. The measured values of acid glycosaminoglycan (GAG) concentration in plasma or in serum show significant differences between trained and untrained horses and among sedentary horses and other animal species (cattle, rabbit, sheep). 2. Diurnal variations in serum GAG levels are reported (cattle), and changes in plasma GAG concentrations after road transport (horses) and in late pregnancy (mares, cows), while sex, age and breed do not affect them.