Canine serum keratan sulfate and hyaluronate concentrations. Relationship to age and osteoarthritis

Serum Collagen Type II Cleavage Epitope and Serum Hyaluronic Acid as Biomarkers for Treatment Monitoring of Dogs with Hip Osteoarthritis

The aim of this study was to evaluate the use of serum type II collagen cleavage epitope and serum hyaluronic acid as biomarkers for treatment monitoring in osteoarthritic dogs. For this purpose, a treatment model based on mesenchymal stem cells derived from adipose tissue combined with plasma rich in growth factors was used. This clinical study included 10 dogs with hip osteoarthritis. Both analytes were measured in serum at baseline, just before applying the treatment, and 1, 3, and 6 months after treatment. These results were compared with those obtained from force plate analysis using the same animals during the same study period. Levels of type II collagen cleavage epitope decreased and those of hyaluronic acid increased with clinical improvement objectively verified via force plate analysis, suggesting these two biomarkers could be effective as indicators of clinical development of joint disease in dogs.

Molecular mass dependence of hyaluronan detection by sandwich ELISA-like assay and membrane blotting using biotinylated hyaluronan binding protein

Hyaluronan (HA) is widely detected in biological samples and its concentration is most commonly determined by the use of a labeled specific HA binding protein (aggrecan G1-IGD-G2, HABP), employing membrane blotting and sandwich enzyme-linked immunosorbent assay (ELISA)-like methods. However, the detected signal intensity or the quantified value obtained by using these surface-based methods is related to the molecular mass (M) of HA, especially for HA in the low M range below ~150 kDa. At the same mass or mass concentration, higher M HA gives a higher signal than lower M HA. We have experimentally determined the quantitative relationship between the M of HA (in the range 20-150 kDa) and the relative signal intensity in comparison with a standard HA, in a sandwich ELISA-like assay. An M-dependent signal correction factor (SCF) was calculated and used to correct the signal intensity, so that the corrected concentration value would more accurately reflect the true HA concentration in solution. The SCF for polydisperse low M HA was also calculated and compared with experimental results. When the molecular mass distribution of an HA sample is determined by a method such as gel electrophoresis, then its appropriately averaged SCF can be calculated and used to correct the signal in sandwich ELISA to obtain a more accurate concentration estimation. The correction method works for HA with M between ~150 and 20 kDa, but lower M HA is too poorly detected for useful analysis. The physical basis of the M-dependent detection is proposed to be the increase in detector-accessible fraction of each surface-bound molecule as M increases.

Hyaluronic acid concentrations in synovial fluid of dogs with different stages of osteoarthritis

To compare hyaluronic acid (HA) concentrations measured in synovial fluid (SF) of joints with different stages of canine secondary osteoarthritis (OA), clinical-orthopedic, radiographic, macroscopic intra-operative and SF findings of 49 joints were assessed. The sum of single findings was correlated to HA concentrations measured by a commercially available ELISA. Joints were categorized into three OA-groups: non-osteoarthritic, mildly osteoarthritic, and severely osteoarthritic. A significant negative correlation was found between severity of OA and HA concentrations (r=-0.696; P<0.001). Median values of HA concentrations decreased with increasing severity of the disease. Statistically significant differences in HA concentrations were observed between the OA-groups (P<0.001). Due to overlapping values between groups, it was concluded that synovial HA concentrations may only indicate a trend of osteoarthritic disease activity, but is not suitable for staging the disease.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the dog

The dog is a common model for study of osteoarthritis (OA). Subjective histologic scoring systems have often served as the reference standard for presence and severity of OA. However, these scoring systems have perceived shortcomings. The system developed for this report attempts to address these shortcomings by providing a standardized methodology for global assessment of the joint, versatility and the potential for relative weighting of pathology, allowing for comparison among time points, studies, and centers, and critical analysis of the system's reliability. The proposed system for assessment of canine tissues appears to provide an effective method for global assessment of articular pathology in OA. The system is versatile, comprehensive, and reliable and appears to have advantages over conventional scoring systems.

Evaluation of serum chondroitin sulfate and hyaluronan: biomarkers for osteoarthritis in canine hip dysplasia

Hip dysplasia (HD) is one of the most important bone and joint diseases in dogs. Making the radiographic diagnosis is sometime possible when the disease has markedly progressed. Chondroitin sulfate (CS) and hyaluronan (HA) are the most important cartilage biomolecules that are elevated in the serum taken from dogs with osteoarthritis. The serum CS and HA can be detected by an ELISA technique, with using monoclonal antibodies against CS epitope 3B3 and WF6 and the HA chain as the primary antibodies. The aim of this study was to compare the levels of serum CS (both epitopes) and HA in non-HD and HD dogs. All 123 dogs were categorized into 2 groups. The non-HD group was composed of 98 healthy dogs, while the HD group was comprised of 25 HD dogs. Blood samples were collected for analyzing the serum CS and HA levels with using the ELISA technique. The results showed that the average serum level of the CS epitope WF6 in the HD group (2,594 ± 3,036.10 ng/ml) was significantly higher than that in the non-HD group (465 ± 208.97 ng/ml) (p < 0.01) while the epitope 3B3 in the HD group (105 ± 100.05 ng/ml) was significantly lower than that in the non-HD group (136 ± 142.03 ng/ml) (p < 0.05). The amount of serum HA in the HD group (134.74 ± 59.71 ng/ml) was lower than that in the non HD group (245.45 ± 97.84 ng/ml) (p < 0.05). The results indicate that the serum CS and HA levels might be used as biomarkers for osteoarthritis in HD dogs.

Computed tomographic evaluation of growth-related changes in the hip joints of young dogs

OBJECTIVE

To evaluate changes in canine hip joint characteristics during growth via computed tomography (CT) and compare CT features of hip joints with and without laxity in young dogs placed in 2 imaging positions.

ANIMALS

21 dogs (42 hip joints).

PROCEDURES

From 2 to 12 months after birth, CT examinations of the acetabulum of each hip joint in simulated normal standing and simulated weight-bearing positions were performed monthly for all dogs. Acetabular angle, dorsal acetabular rim angle (DARA), and femoral head diameter (FHd) were analyzed as skeletal variables; the lateral center edge angle (LCEA), dorsolateral subluxation (DLS) score, and center distance (CD) index were analyzed as joint laxity variables. At 12 months, all dogs underwent the Ortolani test to as-sess hip joint laxity.

RESULTS

Hip joint laxity was detected in 5 dogs (10 joints) at 12 months of age; from 2 months, the acetabular angle and FHd increased and DARA decreased significantly until 5 months and the LCEA and DLS score increased significantly until 6 months. In nonlax hip joints in both positions, the CD index decreased significantly until 4 months of age and be-came stable thereafter. In lax hip joints, the CD index increased from 4 through 12 months; between 8 and 12 months, these changes were significantly greater in the weight-bearing position than in the standing position.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that CT-detected abnormalities in the DARA and CD index during body weight loading might be useful indicators of hip dysplasia in 2- to 6-month-old dogs.

Equine osteoarthritis: a brief review of the disease and its causes

Degenerative joint diseases, such as osteoarthritis, adversely impact the health of the equine athlete as well as the economics of the equine industry. Our understanding of the aetiology of osteoarthritis, although not nearly exhaustive, has increased substantially in recent years. Molecules, including cytokines, inflammatory mediators, and metalloproteinases, have been identified and associated with the progression of joint disease. Several factors, including trauma to the joint, immobilization, conformation, shoeing, and ageing, have been linked with osteoarthritis. Our continued efforts into elucidating critical biological mediators and risk factors, coupled with better chondroprotective therapies and diagnostic tools, should facilitate our ability to maintain the skeletal health of the equine athlete

The effects of growth and disease in serum keratan sulfate concentration in dogs

The purpose of this study is to investigate keratan sulfate (KS) concentration in the serum of puppies and the effects of age, body weight, breed and diseases. Serum samples from six neonatal dogs (4 Beagles, 2 Labrador Retrievers), and from 127 adult dogs with various diseases were collected at a Teaching Animal Hospital. Canine serum KS concentration was measured by inhibition enzyme-linked immunosorbent assay (ELISA). Samples from puppies were evaluated for growth-related changes, and samples from patients were evaluated for age, body weight, breed and disease-related changes. Serum KS concentration was high in puppies from birth to 4 months of age. KS values started to decrease from 4 months to 9 months of age, and then gradually reached to the plateau. Though in the small sample, mean KS concentration in a Labrador Retriever was higher than in Beagles during the first 10 months. The values of serum KS showed body weight-related increase within retrievers among teaching hospital population and there was significant increase in body weight-related change. Cartilage metabolism is high in canine immature joint and that activity continues for 5 months, and that higher in Labrador Retrievers rather than in Beagles. There was no effect from other factors, including age, body weight, breed and disease in all patients. Serum KS concentration of Retrievers is higher than Beagles, and that value increased with gain of body weight. We suggest that Retriever have higher cartilage metabolism with growth or ageing.

Serum and synovial fluid concentrations of keratan sulfate and hyaluronan in dogs with induced stifle joint osteoarthritis following cranial cruciate ligament transection

OBJECTIVE

To examine longitudinal changes in serum and synovial fluid concentrations of keratan sulfate (KS) and hyaluronan (HA) after cranial cruciate ligament (CCL) transection in dogs.

ANIMALS

12 clinically normal adult mixed-breed dogs.

PROCEDURE

Following CCL transection in the right stifle joint, KS and HA concentrations were determined in serum and neat (undiluted) synovial fluid prior to and 1, 2, 3, and 12 months after surgery. Postsurgical dilution of synovial fluid was corrected by use of urea as a passive marker.

RESULTS

Synovial fluid KS and HA concentrations decreased at 1, 2, and 3 months after surgery in operated stifle joints, compared with baseline values. Synovial fluid KS concentration decreased in unoperated stifle joints at 1 month. A decrease in synovial fluid KS concentration was found in operated stifle joints, compared with unoperated stifle joints, at 2 and 3 months, and a decrease in synovial fluid HA concentrations was also found in operated stifle joints, compared with unoperated stifle joints, at 1, 2, and 3 months. Serum KS concentrations increased from baseline values at 3 months after surgery. Hyaluronan concentrations in operated stifle joints were lower than baseline values at 1, 2, and 3 months. Urea-adjusted synovial fluid concentrations revealed that dilution did not account for the decline in biomarker concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

The initial decrease and subsequent increase in synovial fluid concentrations of HA and KS may be caused by an acute inflammatory response to surgical intervention that negatively affects cartilage metabolism or an increase in production of immature proteoglycans.

Chronic Intestinal Pseudo-Obstruction

Chronic intestinal pseudo-obstruction (CIP) is a gastrointestinal motility disorder characterized by chronic symptoms and signs of bowel obstruction in the absence of a fixed, lumen-occluding lesion. Radiographic findings consist of dilated bowel with air-fluid levels. Pseudo-obstruction is an uncommon condition and can result from primary or secondary causes. The management is primarily focused on symptom control and nutritional support to prevent weight loss and malnutrition. The principles of management of patients with CIP involve 1) establishing a correct clinical diagnosis and excluding mechanical obstruction; 2) differentiating between idiopathic and secondary forms; 3) performing a symptomatic and physiologic assessment of the parts of the gastrointestinal (GI) tract involved by manometric and whole gut transit scintigraphic studies; 4) careful assessment of nutritional status of the patient; and 5) developing a therapeutic plan addressing the patient's symptoms and nutritional status. Treatment of CIP includes frequent small meals with a low-fat, low-fiber diet, liquid nutritional supplements may be needed; prokinetic agents such as metoclopramide may help to reduce upper GI symptoms. Trials of drugs such as erythromycin, domperidone, cisapride, and tegaserod may be considered if there is no response. Subcutaneous octreotide may be helpful to improve small bowel dysmotility especially in patients with scleroderma. In patients with symptoms suggestive of bacterial overgrowth, courses of antibiotics such as metronidazole, ciprofloxacin, and doxycycline may be needed. Nutritional assessment and support is an important aspect of management. Enteral nutrition is usually preferred. In carefully selected patients, feeding jejunostomy with or without decompression gastrostomy may be tried. Long term parenteral nutrition should be reserved for patients who can not tolerate enteral nutrition. Complications associated with total parenteral nutrition include infections, sepsis, and cholestatic hepatic dysfunction.

Biochemical change in joint fluid after isometric quadriceps exercise for patients with osteoarthritis of the knee

OBJECTIVE

The purpose of this study was to analyze the biochemical changes in the joint fluid, and pain relief resulting from isometric quadriceps exercise in patients with osteoarthritis of the knee.

DESIGN

Nineteen osteoarthritic knees in 17 patients with joint effusion were included. The patients performed isometric quadriceps exercise for 3 months. Isometric muscle torque at 30 and 60 degrees flexion, pain as measured using the visual analog scale and biochemical markers in joint fluid were evaluated before and after the exercise.

RESULTS

Pain score decreased from 3.9 to 2.3 after 12 weeks of exercise (P<0.001). Extension torque at 30 and 60 degrees knee flexion significantly increased from 4.7 to 6.9 kgm (47% increase, P<0.001) and from 10.8 to 12.6 kgm (17% increase, P<0.005) after 12 weeks of exercise. The molecular weight of hyaluronan increased from 2.11 to 2.40x10(6)(P<0.05) and the viscosity of joint fluid increased from 45.8 to 59.8 mPas after 12 weeks of exercise (P<0.05). Chondroitin 4-, 6-sulfate concentration in joint fluid decreased from 81.9 to 75.5 nmol/ml (P<0.05).

CONCLUSIONS

Isometric quadriceps exercise resulted in significant changes in joint fluid biochemical parameters, and these changes, at least in part, may explain the ameliorative effect of muscle exercise for osteoarthritis of the knee.

Biomarkers of joint tissue metabolism in canine osteoarthritic and arthritic joint disorders

OBJECTIVE

To explore the levels of matrix metalloprotease-3 (MMP-3), tissue inhibitor of metalloproteases-1 (TIMP-1), 5D4 keratan sulfate, and two 3B3 chondroitin-sulfate epitopes in several canine osteoarthritic and inflammatory arthropathies.

METHODS

Blood and synovial fluid were obtained from 103 dogs with rupture of the anterior cruciate ligament (ACLR), osteochondritis dissecans (OCD), fragmented coronoid process (FPC), patella luxation (PL), hip dysplasia (HD) or infectious arthritis. Dogs with non-musculosceletal disorders were used as controls. The biomarkers were measured by immunoassays.

RESULTS

Median levels of synovial MMP-3, TIMP-1 and molar ratios of MMP/TIMP-1 were significantly higher in the arthritis than in the control group. The release of 5D4 keratan sulfate epitope and serum 3B3 neoepitope was reduced in arthritis patients. Increases in synovial TIMP-1 in OA were less pronounced and the molar ratio of MMP-3/TIMP-1 remained far below 1.0, demonstrating a surplus of the protease inhibitor. In osteoarthritic patients median levels of synovial 5D4 keratan sulfate were up-regulated after ACLR and PL and were inversely correlated with increasing duration of lameness. Serum TIMP-1 levels were significantly reduced in the joint disorder group when compared with the control group.

CONCLUSION

Our observations present the TIMP-1 serum level as a potential marker for the detection of degenerative changes in cartilage and also indicate that in canine OA, the MMP-3 mediated matrix destruction is not of major importance. However MMP-3 seems to be a sensitive marker for the local inflammation in canine arthritis.

Serum level of cartilage oligomeric matrix protein (COMP) in equine osteoarthritis

This study was designed to assay and compare cartilage oligomeric matrix protein (COMP) in horse sera, in samples from normal and joint diseased horses, and to investigate the relationships between COMP in sera and synovial fluids (SF) with keratan sulphate (KS) data. Sera from 38 horses free of any joint pathology (controls) and from horses with aseptic joint disease (AJD horses, n = 40) were assayed for COMP and KS concentrations. Of the 78 horses in the study, 53 were also assayed for COMP and KS concentrations in SF. COMP and KS were measured by inhibition ELISA, using monoclonal antibodies 12C4 and 5D4, respectively. The COMP concentration in sera from AJD horses (mean +/- s.d. 10.7 +/- 7.4 microg/ml) was significantly (P<0.02) lower than in control sera (14.8 +/- 7.8 microg/ml). The joint disease sera also had significantly lower (P<0.01) KS levels (180.5 +/- 61.8 ng/ml) than controls (237.1 +/- 116.1 ng/ml). A significant correlation (r = 0.52, n = 53, P<0.001) was seen between serum and SF in COMP levels; no such relationship was seen in KS levels. It is possible that serum COMP concentration could be a more specific marker of equine joint disease than any other described to date.

Serum keratan sulphate as a cartilage metabolic marker in horses: the effect of exercise

Keratan sulphate (KS) concentration in sera from resting horses and horses training daily on a racetrack was measured by an inhibition enzyme-linked immunosorbent assay (ELISA) using anti-equine KS antibody 1/14/16H9. For the in-training horses, serum KS concentrations in 2-year-old-horses was significantly higher than 3- or 4-year-old-horses. A higher concentration of serum KS was found in the in-training group than in the long-term resting group in 2-year-old-horses. Serum KS concentration increased remarkably immediately after training in healthy horses, and at 1, 5, 9 and 24 h after training remained at similar levels to the pre-training concentration. The results suggest that serum KS concentration could represent the situation of joint loading, induced by daily racetrack training, affecting the metabolic activities in joint cartilage.

Evaluation of the role of keratan sulphate as a molecular marker to monitor cartilage metabolism in horses

The role of keratan sulphate (KS) as a metabolic marker of cartilage was evaluated using an in vitro model of equine articular cartilage. Articular cartilage was harvested from clinically healthy 6-month-old foals (n = 3). Chondrocytes were centrifuged and cultured as pellets. Chondrocyte pellets were stimulated by insulin-like growth factor-I alpha (IGF-I alpha) or interleukin-1 alpha (IL-1 alpha) for 2 weeks. The concentrations of sulphated glycosaminoglycans (GAG) and KS in the culture media were measured by a 1,9-dimethyl-methylene blue (DMMB) colorimetric assay and an inhibition enzyme-linked immunosorbent assay using a 1/20/5D4 antibody, respectively. The concentration of GAG was significantly increased both in the media of pellets stimulated by IGF-I alpha and in those stimulated by IL-1 alpha. KS concentration was significantly increased in those stimulated by IL-1 alpha, while no significant change was found in those stimulated by IGF-I alpha. A high correlation between GAG and KS concentrations was found in the media of pellets stimulated by IL-1 alpha (r = 0.84), but not in those stimulated by IGF-I alpha (r = 0.59). The results suggest that the concentration of KS reacting to 1/20/5D4 mirrors the GAG concentration during the stage of cartilage catabolism, but not during the cartilage anabolic stage. The KS concentration in biological fluids could therefore be a useful marker to understand further the cartilage catabolic process. It may also represent some aspects of the cartilage anabolic process.

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.

Consideration of the role of antigenic keratan sulphate reacting to a 1/14/16H9 antibody as a molecular marker to monitor cartilage metabolism in horses

The role of keratan sulphate (KS) as a marker of cartilage metabolism was evaluated by using an in vitro model of equine articular cartilage. Articular cartilage was harvested from clinically healthy 6-month-old foals (n=3). Chondrocytes were centrifuged and cultured as pellets. Chondrocyte pellets were stimulated by insulin-like growth factor (IGF)-Ialpha or interleukin (IL)-1alpha for 2 weeks. The sulfated glycosaminoglycans (GAG) and antigenic KS concentrations in the culture media were measured by a 1,9-dimethyl-methylene blue (DMMB) colorimetric assay and an inhibition ELISA using a 1/14/16H9 antibody, respectively. Concentration of GAG was significantly increased in the media of pellets stimulated by both IGF-Ialpha and IL-1alpha. Antigenic KS concentration was significantly increased in those stimulated by IL-1alpha, while no significant change was found in those stimulated by IGF-Ialpha. A high correlation between GAG and antigenic KS concentrations was found in the media of pellets stimulated by IL-1alpha (r=0.87), but not in those stimulated by IGF-Ialpha (r=0.43). The results suggest that the concentration of antigenic KS reacting to 1/14/16H9 mirrors the GAG concentration during the stage of cartilage catabolism, but not during the cartilage anabolic stage. The concentration of antigenic KS reacting to 1/14/16H9 antibody in biological fluids could therefore be a useful marker to further understand principally the catabolic and slightly the anabolic process of articular cartilage metabolism.

An improved method for the structural profiling of keratan sulfates: analysis of keratan sulfates from brain and ovarian tumors

A previously developed method for the structural fingerprinting of keratan sulfates (Brown et al., Glycobiology, 5, 311-317, 1995) has been adapted for use with oligosaccharides fluorescently labeled with 2-aminobenzoic acid following keratanase II digestion. The oligosaccharides are separated by high-pH anion-exchange chromatography on a Dionex AS4A-SC column. This methodology permits quantitative analysis of labeled oligosaccharides which can be detected at the sub-nanogram ( approximately 100 fmol) level. Satisfactory calibration of this method can be achieved using commercial keratan sulfate standards. Keratan sulfates from porcine brain phosphocan and human ovarian tumors have been examined using this methodology, and their structural features are discussed.

Human aggrecan keratan sulfate undergoes structural changes during adolescent development

Alkaline borohydride-reduced keratan sulfate chains were isolated from human articular cartilage aggrecan from individuals of various ages (0-85 years old). The chains were structurally characterized using 1H NMR spectroscopy, gel permeation chromatography, and oligosaccharide profiling (after digestion with the enzymes keratanase and keratanase II). The results show that from birth to early adolescence (0-9 years) the levels of alpha(1-3)-fucosylation, alpha(2-3)-sialylation, and galactose sulfation increase. Also, the weight-average molecular weight of the chains increases. During maturation (9-18 years) the levels of fucosylation and galactose sulfation continue to increase and alpha(2-6)-sialylation of the chains occurs. In adult life (18-85 years) there is little change in the weight-average molecular weight of the chains, and the levels of fucosylation, sialylation, and sulfation remain fairly constant.

Osteoarthritis. Joint anatomy, physiology, and pathobiology

Normal cartilage is a complex material consisting of a solid matrix composed primarily of collagen and proteoglycan, which is saturated with water. It is not a homogenous material. The interaction of the physical and biochemical structures of cartilage is necessary to allow the normal function of providing nearly frictionless motion, wear resistance, joint congruence, and transmission of load to subchondral bone. Chondrocytes are responsible for synthesizing and maintaining this material. Osteoarthritis occurs when there is disruption of normal cartilage structure and homeostasis. Osteoarthritis results from a complex interaction of biochemical and biomechanical factors that occur concurrently and serve to perpetuate degradative change. The progressive pathologic change that occurs in osteoarthritis has been characterized, not only for articular cartilage but also for periarticular tissues. The occurrence of mechanical and biochemical changes is well established, but the role of each in the etiopathogenesis of osteoarthritis is not rigidly defined. It is likely that there are multiple etiologies sharing common pathways of physical and chemical disruption. (see Fig. 1). The changes associated with osteoarthritis ultimately have an impact on the patient through decreased ability to use the joint or the production of pain, or both. Unfortunately, once these changes are severe enough to be recognized clinically, they are likely to be irreversible with current treatments. Nevertheless, understanding the basic mechanisms involved in the development and progression of osteoarthritis provides a basis for establishing a reasonable expectation for the patient and a rational plan for medical and surgical treatment of this condition.

Histochemical and immunohistochemical studies of the effects of experimental anterior disc displacement on sulfated glycosaminoglycans, hyaluronic acid, and link protein of the rabbit craniomandibular joint

PURPOSE

The purpose of this study was to determine the effects of surgically induced anterior disc displacement (ADD) on sulfated glycosaminoglycans (GAGs) such as keratan sulfate (KS), chondroitin-4-sulfate (C4S), and chondroitin-6-sulfate (C6S), hyaluronic acid (HA), and link protein (LP) of the rabbit craniomandibular joint (CMJ) using histochemical and immunohistochemical techniques.

MATERIALS AND METHODS

The right joint of 20 rabbits was exposed surgically, and all discal attachments were severed except for the posterior attachment. The disc was then repositioned anteriorly and sutured to the zygomatic arch. The left joint served as a sham-operated control. Ten additional joints were used as nonoperated controls. Deeply anesthetized rabbits were perfused with 2% buffered formalin 2 weeks (10 rabbits) or 6 weeks (10 rabbits) after surgery. Discs, bilaminar zones, condyles, and articular eminences were excised. Condyles and articular eminences were decalcified in ethylenediaminetetraacetic acid (EDTA). All tissues were sectioned at 10 microns in a cryostat. Sections were incubated with alcian blue and monoclonal antibodies directed against KS, C4S, C6S, HA, or LP. After incubation in the appropriate fluorescein isothiocyanate (FITC)-labeled secondary antibodies, tissue sections were studied under the fluorescence microscope.

RESULTS

The results showed a reduction in alcian blue staining and KS, C4S, C6S, HA, and LP immunostaining in the disc and articular surfaces at 2 weeks after induction of ADD. This reduction was followed by an increase in their immunostaining at 6 weeks. Also, there was a progressive increase in alcian blue staining, and KS, C4S, C6S, and HA immunostaining in the bilaminar zone at 2 and 6 weeks.

CONCLUSION

It was concluded that surgical induction of ADD in the rabbit CMJ leads to alterations in KS, C4S, C6S, HA, and LP content, consistent with similar changes accompanying osteoarthritis of other synovial joints.

A new pressure chamber to study the biosynthetic response of articular cartilage to mechanical loading

A prototype chamber was used to apply a precise cyclic or static load on articular cartilage explants under sterile conditions. A variable pressure, pneumatic controller was constructed to power the chamber's air cylinder, capable of applying, with a porous load platen, loads of up to 10 MPa at cycles ranging from 0 to 10 Hz. Pig articular cartilage explants were maintained successfully in this chamber for 2 days under cyclic mechanical loading of 0.5 Hz, 0.5 MPa. Explants remained sterile, viable and metabolically active. Cartilage responded to this load with a decreased synthesis of fibronectin and a small but statistically significant elevation in proteoglycan content. Similar but less extensive effects on fibronectin synthesis were observed with the small static load (0.016 MPa) inherent in the design of the chamber.

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.

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.

Fibronectin and keratan sulfate synthesis by canine articular chondrocytes in culture is modulated by dibutyryl cyclic adenosine monophosphate

The ability of cyclic adenosine monophosphate (cAMP) to maintain differentiated properties of canine articular chondrocytes in culture is reported. Treatment with 0.5 mM dibutyryl cAMP (DBcAMP) caused the cells to adopt a more rounded morphology. This change in morphology seems to have no effect on the overall biosynthetic rates of the cells. After a pulse with 35S-methionine, there was no difference in the concentration of labeled proteins between cultures treated with DBcAMP and control cultures. After 6 days, the amount of fibronectin (FN) in the media of DBcAMP-treated cultures detected by an enzyme-linked immunosorbent assay was specifically reduced by 30%. The amount of 35S-FN purified by gelatin-affinity chromatography decreased 33%. Moreover, the percentage of FN containing the extra domain A sequence was reduced from 19.4 +/- 8.7% in control cultures to 9.6 +/- 4.2%. Concomitant with the decrease in FN, there was an increase in the concentration of keratan sulfate in the media of DBcAMP-treated cultures. After 6 days, treated cultures had 47% more keratan sulfate than controls did. These changes appear not to be the result of a change in the deposition of FN or keratan sulfate, because the amount of these molecules that could be extracted from the cell layer was typically below the limit of detection of the assays. Instead, it seems there is a phenotypic change in the chondrocytes pertaining to the production of FN and keratan sulfate.

Elevated plasma levels of hyaluronate in patients with osteoarthritis and rheumatoid arthritis

Plasma levels of hyaluronate (HA) in patients with rheumatoid arthritis (RA) and patients with osteoarthritis (OA), measured by enzyme-linked immunosorbent assay, were compared with levels in a healthy, age-matched non-arthritic control group, in a retrospective study. Compared with the controls, the mean level of plasma HA was sevenfold higher in the RA group and twofold higher in the OA group. There was no statistically significant correlation between HA levels and 7 other clinical and biochemical parameters in patients with RA. In the OA group, however, plasma HA levels were found to correlate with an objective functional capacity score and with an articular index based on the total amount of cartilage in involved joints. In a retrospective longitudinal study of 6 patients with RA, plasma levels of HA did not show a significant correlation with plasma levels of elastase or with the erythrocyte sedimentation rate. These data support in part the contention that plasma HA may be unique as a marker, in that it may be a reflection of synovial involvement and inflammation, rather than only of inflammation, in arthritis.