The metabolic responses of equine articular cartilage to incubation with bacterial lipopolysaccharide (LPS) were studied, using explant cultures of articular cartilage obtained from the metatarsophalangeal joints of 15 horses, age of which ranged from 3 months to 20 years. For comparison, explants were also established from the metatarsophalangeal joints of 3 calves. Explants were cultured for 3 days in medium containing various concentrations of LPS from 0 (control) to 100 microgram/ml. Glycosaminoglycan (GAG) released during the 3-day incubation was determined by a spectrophotometric assay, using the dye 1,9-dimethylmethylene blue. Newly synthesized GAG content was assayed by measuring [35S]sulfate incorporation during a 3-hour pulse labeling period. In addition, prostaglandin E2 (PGE2) synthesis was quantified, using a [3H]PGE2 radioimmunoassay kit and magnetic separation. Finally, explants from 3 animals were used to evaluate the effect of supplementing culture medium with 5% serum on the response of explants to LPS, and explants from 1 horse were used to compare responses to stimulation with LPS derived from 2 bacterial sources. Equine explants cultured with bacterial LPS had a dose-dependent decrease in synthesis and increase in release of GAG, and these responses were significantly (P < 0.0001) greater in explants from younger horses. In addition, equine explants had a significant (P = 0.0001) dose-dependent increase in concentration of PGE2 released into the culture medium in response to incubation with LPS. Comparison of data for GAG synthesis from equine and bovine explants revealed a significant (P = 0.025) difference in responsiveness to LPS between the 2 species. Equine explants tended to have a greater suppression of GAG synthesis in response to incubation with increasing concentrations of LPS than did age-corrected bovine samples.

Keratan sulfate (KS) is a glycosaminoglycan, distribution of which is confined mostly to hyaline cartilage. As such, it is a putative marker of hyaline cartilage catabolism. In experiment 1, a focal osteochondral defect was made arthroscopically in 1 radial carpal bone of 2 ponies, and in 2 other ponies, chymopapain was injected into the radiocarpal joint to induce cartilage catabolism. Sequential and concurrent plasma and synovial fluid concentrations of KS were measured, up to 13 months after induction of cartilage injury, to determine whether changes in KS concentrations reflected cartilage catabolism. In experiment 2, a large, bilateral osteochondral defect was made in the radial carpal bones of 18 ponies, which were subsequently given postoperative exercise and/or injected intra-articularly with 250 mg of polysulfated glycosaminoglycan (PSGAG). Medication was given at surgery, then weekly for 4 weeks. Blood samples were collected and synovial fluid was aspirated before surgery, when medication was given, and at postmortem examination (postoperative week 17). The KS concentration was measured in these fluids to determine whether changes in KS concentration indicated an effect of joint treatment. In experiment 1, the concentration of KS in synovial fluid was highest 1 day after joint injury, and the concentration in plasma peaked 2 days after joint injury. For ponies receiving chymopapain intra-articularly (generalized cartilage catabolism), a fivefold increase over baseline was observed in the concentration of KS in plasma (peak mean, 1.2 microgram/ml), and a tenfold increase over baseline in synovial fluid (peak mean, 2.0 mg/ml) was observed. On average, these maxima were threefold higher than values in fluids of ponies with osteochondral defects (focal cartilage disease). In experiment 2, nonexercised ponies had lower KS concentration (as a percentage of the preoperative concentration) in synovial fluid than did exercised ponies at all postoperative times, and.

Middle carpal cartilage explants from 4 horses with mild osteoarthritis involving that joint were maintained in tissue culture to test the effects of a polysulfated glycosaminoglycan (PSGAG) on proteoglycan synthesis and degradation. Cultures were exposed to 0.025 or 25 mg of PSGAG/ml for 48 hours, after which the medium was replaced with medium containing similar doses of PSGAG and 35S. Subsequently, the sulfated proteoglycan content of the medium and extracts of the explants was measured. Gel filtration chromatography was used to estimate the size and to purify the principal, large proteoglycan monomer, which was further characterized by digestion, using glycosidic enzymes. In a second experiment, explants were incubated with 35S for 48 hours, and were subsequently exposed to the same concentrations of the PSGAG for an additional 48 hours. The amount of remaining labeled proteoglycan was determined for culture medium and cartilage extracts. Gel filtration chromatography was used to assess the hydrodynamic size of the large proteoglycan monomer. Aliquots of proteoglycans from the second experiment were incubated in high-molecular weight hyaluronate and chromatographed to assess reaggregation. Polysulfated glycosaminoglycan caused a significant (P < 0.04) decrease in sulfated proteoglycan synthesis by cartilage explants. Radioactive proteoglycan content in explants labeled prior to exposure to PSGAG were similar. Large proteoglycan monomer size was similar in both experiments (median partition coefficient [K(AV)] = 0.40), and was not influenced by PSGAG treatment. Prelabeled explants exposed to hyaluronate and chromatographed under associative conditions had similar proportions of the radiolabel eluting as proteoglycan aggregate. Enzymatic digestion of newly synthesized large monomer revealed a mild dose-dependent increase in the proportion of keratan sulfate substitution on core protein. It was concluded that PSGAG in vitro, at the dosages evaluated, caused a decre.

OBJECTIVE To characterize delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) features of healthy hyaline cartilage of the distal interphalangeal joint (DIPJ) of horses, to determine whether dGEMRIC can be used to differentiate various stages of naturally occurring osteoarthritis of the DIPJ, and to correlate relaxation times determined by dGEMRIC with the glycosaminoglycan concentration, water content, and macroscopic and histologic findings of hyaline cartilage of DIPJs with and without osteoarthritis. SAMPLE 1 cadaveric forelimb DIPJ from each of 12 adult warmblood horses. PROCEDURES T1-weighted cartilage relaxation times were obtained for predetermined sites of the DIPJ before (T1preGd) and after (T1postGd) intra-articular gadolinium administration. Corresponding cartilage sites underwent macroscopic, histologic, and immunohistochemical evaluation, and cartilage glycosaminoglycan concentration and water content were determined. Median T1preGd and T1postGd were correlated with macroscopic, histologic, and biochemical data. Mixed generalized linear models were created to evaluate the effects of cartilage site, articular surface, and macroscopic and histologic scores on relaxation times. RESULTS 122 cartilage specimens were analyzed. Median T1postGd was lower than the median T1preGd for normal and diseased cartilage. Both T1preGd and T1postGd were correlated with macroscopic and histologic scores, whereby T1preGd increased and T1postGd decreased as osteoarthritis progressed. There was topographic variation of T1preGd and T1postGd within the DIPJ. Cartilage glycosaminoglycan concentration and water content were significantly correlated with T1preGd and macroscopic and histologic scores but were not correlated with T1postGd. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that dGEMRIC relaxation times varied for DIPJs with various degrees of osteoarthritis. These findings may help facilitate early detection of osteoarthritis.

Objective: To evaluate urine concentrations of glycosaminoglycans, Tamm-Horsfall glycoprotein, and nephrocalcin in cats fed a diet formulated to prevent calcium oxalate uroliths. Animals: 10 cats with calcium oxalate urolithiasis. Procedures: In a previous study conducted in accordance with a balanced crossover design, cats were sequentially fed 2 diets (the diet each cat was consuming prior to urolith detection and a diet formulated to prevent calcium oxalate uroliths). Each diet was fed for 8 weeks. At the end of each 8-week period, a 72-hour urine sample was collected. Concentrations of glycosaminoglycans, Tamm-Horsfall glycoprotein, and the 4 isoforms of nephrocalcin in urine samples collected during that previous study were measured in the study reported here. Results: Diet had no effect on the quantity of Tamm-Horsfall glycoprotein and nephrocalcin in urine. However, the urine concentration of glycosaminoglycans was significantly higher during consumption of the urolith prevention diet. Conclusions and Clinical Relevance: Feeding a urolith prevention diet increased the urine concentration of glycosaminoglycans, which are glycoprotein inhibitors of growth and aggregation of calcium oxalate crystals.

Cartilage resurfacing by chondrocyte transplantation, using porous collagen matrices as a vehicle to secure the cells in cartilage defects, has been used experimentally in animals, This in vitro study evaluated the temporal morphologic features and proteoglycan synthesis of chondrocyte-laden collagen matrices. Forty-two porous collagen disks were implanted with a minimum of 6 X 10(6) viable chondrocytes, covered by a polymerized collagen gel layer, and 6 disks were harvested after 0, 3, 7, 10, 14, 18, or 22 days of incubation in supplemented Ham's F12 medium at 37 degrees C and 5% CO2. Histologic and histochemical evaluation of formalin-fixed segments of the cultured disks indicated that the chondrocytes proliferated in the implant, producing small groups and linear segments of cells by day 14. The collagen framework remained intact over the course of the study with thick areas attributable to depositions of matrix material after day 10. Alcian blue-stained matrix was evident in the pericellular region of chondrocytes in sections of disks harvested on days 14, 18, and 22. Glycosaminoglycan (GAG) assay by dimethylmethylene blue dye binding after papain digestion of the disk segments revealed negligible amounts of GAG at day 0. Significant (P < 0.0001) increase in total GAG content was observed by day 3 (0.329 micrograms/mg of disk) and further increases were observed until a plateau in GAG quantity was seen on day 14. Mean peak GAG content was 0.553 +/- 0.062 micrograms/mg. Secondary treatment of the papain-digested implants with keratanase and chondroitinase ABC yielded similar trends in chondroitin sulfate (CS) and keratan sulfate (KS) concentrations. The CS content significantly (P = 0.0002) increased for the first 14 days of incubation, then a plateau was observed for the remainder of the study. Peak CS content was 0.354 +/- 0.037 micrograms/mg. Concentration of KS reached a plateau earlier than did CS content, with peak amount of 0.193 +/- 0.027 micrograms/mg on day 10. Fluctuations in KS content were not significant until an increase on day 22. Chondrocytes actively populated the collagen implants, increasing in number and synthesizing matrix GAG epitopes over the 22 days of incubation. These results indicate that chondrocyte-laden porous collagen matrices may be suitable cartilage analogue materials and the optimal metabolic time for transfer to cartilage defects is 10 to 14 days.

Keratan sulfate (KS) is a glycosaminoglycan, distribution of which is confined mostly to hyaline cartilage. As such, it is a putative marker of hyaline cartilage catabolism. In experiment 1, a focal osteochondral defect was made arthroscopically in 1 radial carpal bone of 2 ponies, and in 2 other ponies, chymopapain was injected into the radiocarpal joint to induce cartilage catabolism. Sequential and concurrent plasma and synovial fluid concentrations of KS were measured, up to 13 months after induction of cartilage injury, to determine whether changes in KS concentrations reflected cartilage catabolism. In experiment 2, a large, bilateral osteochondral defect was made in the radial carpal bones of 18 ponies, which were subsequently given postoperative exercise and/or injected intra-articularly with 250 mg of polysulfated glycosaminoglycan (PSGAG). Medication was given at surgery, then weekly for 4 weeks. Blood samples were collected and synovial fluid was aspirated before surgery, when medication was given, and at postmortem examination (postoperative week 17). The KS concentration was measured in these fluids to determine whether changes in KS concentration indicated an effect of joint treatment. In experiment 1, the concentration of KS in synovial fluid was highest 1 day after joint injury, and the concentration in plasma peaked 2 days after joint injury. For ponies receiving chymopapain intra-articularly (generalized cartilage catabolism), a fivefold increase over baseline was observed in the concentration of KS in plasma (peak mean, 1.2 microgram/ml), and a tenfold increase over baseline in synovial fluid (peak mean, 2.0 mg/ml) was observed. On average, these maxima were threefold higher than values in fluids of ponies with osteochondral defects (focal cartilage disease). In experiment 2, nonexercised ponies had lower KS concentration (as a percentage of the preoperative concentration) in synovial fluid than did exercised ponies at all postoperative times, and at postoperative week 17, this effect was significant (P < 0.05). This may be related to decreased turnover of KS in articular cartilage attributable to stall confinement and late increase in turnover related to exercise. Seventeen weeks after surgery, synovial fluid from exercised, medicated ponies had significantly (P < 0.05) higher KS content than did fluid from exercised, nonmedicated ponies. This indicated that exercise, when combined with medication, may increase KS release from articular cartilage. Synovial fluid from medicated joints of nonexercised ponies had significantly (P < 0.05) lower KS concentration than did synovial fluid from nonmedicated joints of nonexercised ponies. This indicated that, in nonexercised joints, medication with PSGAG may have decreased either release of KS from the articular cartilage into the synovial fluid or inhibited synthesis of KS. Concentration of KS in synovial fluid was not related clearly to the development of osteoarthritis in these ponies. Exercise or medication did not affect plasma KS concentration, and synovial fluid and plasma KS concentrations were not correlated. Data indicated that KS concentration in plasma and synovial fluid may be increased in acute, marked, generalized articular cartilage catabolism and that KS turnover in cartilage of joints with large osteochondral defects was affected by intra-articular PSGAG and postoperative exercise.

The anterior chambers in 16 dogs with normotensive eyes and 3 Beagles with glaucomatous eyes were treated with 0, 25, 50, or 100 IU of bovine testicular hyaluronidase. Aqueous outflow resistance was then determined by constant-pressure perfusion of 0.9% NaCl solution for 30 or 60 minutes. In normotensive eyes, 25, 50, or 100 IU of hyaluronidase significantly (P < 0.02) increased the rate of constant-pressure perfusion compared with that of untreated eyes during 30- or 60-minute perfusions. Treatment of glaucomatous eyes with 25, 50, or 100 IU of hyaluronidase did not significantly increase the rate of constant-pressure perfusion over controls during a 30-minute perfusion. Bovine testicular hyaluronidase at all doses removed the staining of colloidal iron from the trabecular meshwork in normotensive eyes. In Beagles with glaucoma, the trabecular meshworks remained stained with colloidal iron when treated with the hyaluronidase, which suggested that some glycosaminoglycans were resistant to this enzyme's action.

The ability of polysulfated glycosaminoglycans (PSGAG) to inhibit the complement cascade was evaluated. The role of complement in inflammation and infection has been well documented. Inhibition of the complement cascade by PSGAG could explain why intra-articularly administered PSGAG diminish diarthrodial joint inflammation and potentiate septic arthritis in horses. Hemolytic complement testing was performed to evaluate the effect of PSGAG on the equine classical and alternate pathways of complement, using rabbit erythrocytes as the target cells. Concentration of PSGAG between 0.2 mg/ml and 0.6 mg/ml significantly (P < 0.05) inhibited equine complement in dose-related fashion. Further increase in complement inhibition was not observed at PSGAG concentration > 0.6 mg/ml. Difference was not apparent in the extent of inhibition of complement from each of the 4 horses tested. Polysulfated glycosaminoglycans appeared to inhibit the classical and alternate complement pathways equally, indicating possible effect on complement components common to both pathways. Heat inactivation of complement function completely inhibited (P < 0.01) the hemolytic activity of the serum from all horses.

Using arthroscopic technique, identical diameter defects were created in the proximal articular surface of both intermediate carpal bones of 6 horses. One of each pair of defects was deepened to penetrate the subchondral plate. Removed cartilage was assayed for [35S] sulfate incorporation, total hexosamine content, and DNA content. Six weeks later, cartilage was harvested and similarly analyzed from the distolateral portion of the radius directly opposite the created lesions and the distomedial portion of the radius distant from the lesion. The repair tissue filling the full-thickness defect and the cartilage at the periphery of the partial-thickness lesion also were analyzed. There was a marked increase in synthetic activity (35S sulfate incorporation) opposite the full-thickness defect, compared with the cartilage opposite the partial-thickness defect. A marked decrease in glycosaminoglycan content in the cartilage opposite the full-thickness defect was found as compared with that opposite the partial-thickness defect. The repair tissue filling the full-thickness defect was highly cellular, high in synthetic activity, but low in glycosaminoglycan content. Insignificant changes occurred in the cartilage adjacent to the partial-thickness defect. On the basis of these results, we suggest that full-thickness defects at 6 weeks result in more detrimental change to the cartilage opposite it than do partial-thickness lesions of the same diameter.