Cartilage degradation by neutral proteoglycanases in experimental osteoarthritis. Suppression by steroids

In vitro cytotoxic effects of benzalkonium chloride in corticosteroid injection suspension

BACKGROUND

Some deleterious effects on cartilage and even severe arthropathy have been reported after intra-articular corticosteroid injections. The objective of the present in vitro study was to determine if an injectable corticosteroid suspension is toxic to articular chondrocytes and synovial cells.

METHODS

Human and bovine articular chondrocytes, bovine synovial cells, mouse C3H10T1/2 cells, and human osteosarcoma MG-63 cells were treated for thirty minutes in monolayer or suspension culture with an injectable corticosteroid suspension or its chemical components, including betamethasone sodium phosphate, betamethasone acetate, and benzalkonium chloride (as preservative). Cell viability was determined by means of microscopy or flow cytometry analysis.

RESULTS

In monolayer culture, the betamethasone corticosteroids per se did not cause cell death, whereas benzalkonium chloride caused death of articular chondrocytes. In suspension culture, betamethasone sodium phosphate at dosages of as high as 6 mg/mL did not cause significant death of human or bovine articular chondrocytes (p > 0.05). In contrast, benzalkonium chloride caused a death rate of 10.6% in human articular chondrocytes at a dosage of 10 microg/mL (p < 0.01), 21.0% at a dosage of 13.3 microg/mL (p < 0.01), and 99.3% and 99.4% at dosages of 20 and 200 microg/mL, respectively (p < 0.001 for both). Similarly, benzalkonium chloride caused death of bovine articular chondrocytes, bovine synovial cells, C3H10T1/2 cells, and MG-63 cells in a dose-dependent manner. When treated with a combination of betamethasone sodium phosphate and 200 microg/mL benzalkonium chloride, >99% of human or bovine articular chondrocytes were dead (p < 0.001).

CONCLUSIONS

The injectable corticosteroid suspension caused death in in vitro culture of human and bovine articular chondrocytes as well as bovine synovial cells because of its preservative benzalkonium chloride. The betamethasone corticosteroids per se did not cause significant chondrocyte death under the conditions tested.

Chondroprotective drugs in degenerative joint diseases

Catabolic cytokine and anabolic growth factor pathways control destruction and repair in osteoarthritis (OA). A unidirectional TNF-alpha/IL-1-driven cytokine cascade disturbs the homeostasis of the extracellular matrix of articular cartilage in OA. Although chondrocytes in OA cartilage overexpress anabolic insulin-like growth factor (IGF) and its specific receptor (IGFRI) autocrine TNF-alpha released by apoptotic articular cartilage cells sets off an auto/paracrine IL-1-driven cascade that overrules the growth factor activities that sustain repair in degenerative joint disease. Chondroprotection with reappearance of a joint space that had disappeared has been documented unmistakably in peripheral joints of patients suffering from spondyloarthropathy when treated with TNF-alpha-blocking agents that repressed the unidirectional TNF-alpha/IL-1-driven cytokine cascade. A series of connective tissue structure-modifying agents (CTSMAs) that directly affect IL-1 synthesis and release in vitro and down-modulate downstream IL-1 features, e.g. collagenase, proteoglycanase and matrix metalloproteinase activities, the expression of inducible nitric oxide synthase, the increased release of nitric oxide, and the secretion of prostaglandin E(2), IL-6 and IL-8, have been shown to possess disease-modifying OA drug (DMOAD) activities in experimental models of OA and in human subjects with finger joint and knee OA. Examples are corticosteroids, some sulphated polysaccharides, chemically modified tetracyclines, diacetylrhein/rhein, glucosamine and avocado/soybean unsaponifiables.

Oral treatment with PD-0200347, an ?2? ligand, reduces the development of experimental osteoarthritis by inhibiting metalloproteinases and inducible nitric oxide synthase gene expression and synthesis in cartilage chondrocytes

OBJECTIVE

To examine the in vivo effects of PD-0200347, an alpha(2)delta ligand of voltage-activated Ca(2+) channels and a compound chemically related to pregabalin and gabapentin, on the development of cartilage structural changes in an experimental dog model of osteoarthritis (OA). The effects of PD-0200347 on the major pathways involved in OA cartilage degradation, including matrix metalloproteinases (MMPs) and the inducible form of nitric oxide synthase (iNOS), were also studied.

METHODS

OA was surgically induced in dogs by sectioning the anterior cruciate ligament. OA dogs were randomly distributed into 3 groups and treated orally with either 1) placebo, 2) 15 mg/kg/day of PD-0200347, or 3) 90 mg/kg/day of PD-0200347. Dogs were killed 12 weeks after surgery. The severity of the lesions was scored macroscopically and histologically. Cartilage specimens from the femoral condyles and tibial plateaus were processed for RNA extraction and quantitative reverse transcription-polymerase chain reaction (RT-PCR) or immunohistochemistry. Specific probes and antibodies were used to study the messenger RNA and protein levels of iNOS, MMP-1, MMP-3, and MMP-13.

RESULTS

No clinical signs of drug toxicity were noted in the treated animals. Treatment with PD-0200347 at both dosages tested (15 and 90 mg/kg/day) reduced the development of cartilage lesions. There was a reduction in the score of lesions, with a statistically significant (P = 0.01) difference when the highest dosage of the drug was administered. The reduction in the score was mainly related to a decrease in the surface size of the lesions. Quantitative RT-PCR showed that PD-0200347 significantly reduced the expression of MMP-13, a key mediator in OA. Immunohistochemical analyses showed that treatment with PD-0200347 significantly reduced the synthesis of all key OA mediators studied.

CONCLUSION

This study demonstrated the efficacy of PD-0200347 in reducing the progression of cartilage structural changes in a dog model of OA. It also showed that this effect is linked to the inhibition of the major pathophysiologic mediators responsible for cartilage degradation.

Physiological levels of hydrocortisone maintain an optimal chondrocyte extracellular matrix metabolism

OBJECTIVE

To investigate the effects of physiological doses of hydrocortisone on synthesis and turnover of cell associated matrix (CAM) by human chondrocytes obtained from normal articular cartilage.

METHODS

Human articular cartilage cells were obtained from visually intact cartilage of the femoral condyles of five donors and maintained in culture for one week to reach equilibrium in accumulated CAM compounds. 0, 0.05, 0.20, and 1.0 micro g/ml hydrocortisone was added to the nutrient media during the entire culture period. Cells were liberated and levels of CAM aggrecan, type II collagen, and fibronectin, of intracellular IGF-1, IL1alpha and beta, and of their respective plasma membrane bound receptors IGFR1, IL1RI, and the decoy receptor IL1RII, were assayed by flow cytometry.

RESULTS

In comparison with controls, hydrocortisone treated chondrocytes, at all concentrations, expressed significantly higher plasma membrane bound IGFR1. Intracellular IGF-1 levels remained unchanged. Together with these changes, reflecting an increased ability to synthesise extracellular matrix (ECM) macromolecules, hydrocortisone treated cells expressed significantly higher amounts of the plasma membrane bound decoy IL1RII. Concurrently, intracellular IL1alpha and beta levels and membrane bound IL1RI were down regulated. Levels of CAM aggrecan, type II collagen, and fibronectin were significantly up regulated in the chondrocytes treated with hydrocortisone.

CONCLUSION

0.05 micro g/ml hydrocortisone treated chondrocytes had decreased catabolic signalling pathways and showed an enhanced ability to synthesise ECM macromolecules. Because IL1 activity was decreased and the expression of IL1RII decoy receptor enhanced, more of the ECM macromolecules produced remained accumulated in the CAM of the chondrocytes. The effects were obtained at doses comparable with physiological plasma levels of hydrocortisone in humans.

The Novartis-ILAR Rheumatology Prize 2001 Osteoarthritis: from molecule to man

During our careers, we have developed new and innovative concepts pertaining to the pathophysiology of osteoarthritis which have assisted in the development of new therapeutic approaches. Moreover, our laboratory has long sought to develop protective agents for osteoarthritic structural joint tissues. The most significant concepts that have originated from our lab are briefly outlined in this commentary.

A risk-benefit assessment of intra-articular corticosteroids in rheumatic disorders

The appeal of intra-articular corticosteroid therapy has increased with the growing emphasis on early disease control in rheumatoid disease. The impact on the patient's pain and stiffness is impressive and prompt. This may encourage patient compliance with longer term therapies given to slow the course of the disease. The release of corticosteroid into the circulation also provides some generalised improvement. This can prove helpful during the management of flares of inflammatory disease. There is less evidence to support the use of intra-articular corticosteroids in other inflammatory arthritides, but experience suggests that the benefits are similar. In osteoarthritis the benefits are less certain, but intra-articular therapy may prove important in patients who cannot undergo salvage operative procedures because of intercurrent illness. The benefits of intra-articular corticosteroids may be enhanced by rest after the injection, or by the additional administration of agents such as radio-colloids, rifampicin (rifampin), or osmic acid. Most controlled trial data have been published on knee injections, but other joints can be useful targets for local therapy. The risks are mainly related to the discomfort of the procedure, localised pain post-injection and flushing, but most feared is septic arthritis which probably occurs in about 1 in 10000 injections. Careful aseptic technique is the best protection. Tissue atrophy at the injection site, abnormal uterine bleeding, hypertension and hyperglycaemia rarely cause problems. Osteonecrosis might be as much a problem with uncontrolled painful arthritis as with a joint rendered less symptomatic by corticosteroid injections. Intra-articular corticosteroids form an important part of the management of inflammatory joint disease and might be considered where an inflammatory element occurs in osteoarthritis. They may be used at any stage in the arthritic process, but should be seen as an adjunct to other forms of symptom relief. In patients needing multiple joint injections, systemic therapy should be reviewed to see if better disease control could reduce the need for invasive therapy.

Mono-iodoacetate-induced experimental osteoarthritis: a dose-response study of loss of mobility, morphology, and biochemistry

OBJECTIVE

To characterize the dose-responsiveness of morphologic and biochemical chondral changes relative to mobility in mono-iodoacetate (MIA)-induced osteoarthritis (OA) in rats.

METHODS

Rat mobility was assessed by biotelemetry. Articular lesions were characterized by macroscopic and histologic examinations. Cartilage proteoglycan metabolism was evaluated by the 1,9-dimethylmethylene blue dye binding assay and by radiosulfate incorporation in patellar cartilage.

RESULTS

Spontaneous locomotor activity was rapidly, transiently, and dose-dependently decreased after MIA injection into rat knees (primary response). Thereafter, only high doses (0.3 mg and 3.0 mg) led to a secondary progressive long-term loss of spontaneous mobility on day 15, when subchondral bone was exposed. These 2 doses resulted in significant changes in cartilage proteoglycan concentration at day 15 and a strong inhibition of anabolism in the peripheral patellae by day 2, contrasting with the effects of lower doses (0.01, 0.03, and 0.1 mg).

CONCLUSION

When a sufficient dose of MIA is used, this model can easily and quickly reproduce OA-like lesions and functional impairment in rats, similar to that observed in human disease. These parameters, as well as proteoglycan metabolism, could serve as indicators for studying chondroprotective drugs, or for evaluating the ability of imaging techniques to detect and evaluate chondral lesions.

Effects of triamcinolone acetonide on an in vivo equine osteochondral fragment exercise model

The objective of this study was to determine the effects of intra-articularly administered triamcinolone acetonide (TA) in exercised equine athletes with carpal osteochondral fragmentation. Eighteen horses were randomly assigned to each of 3 groups. An osteochondral chip fragment was created in one randomly chosen intercarpal joint of each horse. Both intercarpal joints in the placebo control group (CNT) horses were injected with intra-articular administration (IA) of polyionic fluid. Both joints in the TA control group (TA CNT) horses were treated with 12 mg of TA in the intercarpal joint without an osteochondral fragment, and the opposite intercarpal joint was injected with a similar volume of polyionic fluid. The TA treated group (TA TX) horses were treated with 12 mg of TA in the joint that contained the osteochondral fragment and the opposite intercarpal joint was injected with a similar volume of polyionic fluid. All horses were treated IA on days 13 and 27 after surgery and exercised on a high speed treadmill for 6 weeks starting on Day 14. Horses in the TA TX group were significantly less lame than horses in the CNT and TA CNT groups. Horses in either TA CNT or TA TX groups had lower total protein, and higher hyaluronan, and glycosaminoglycan concentrations in synovial fluid than did those in the CNT group. Synovial membrane collected from subjects in TA CNT and TA TX groups had significantly less inflammatory cell infiltration, subintimal hyperplasia and subintimal fibrosis compared to the CNT group. Articular cartilage histomorphological parameters were significantly better from the TA CNT and TA TX groups compared to the CNT group. In conclusions, results from this study support favourable effects of TA on degree of clinically detectable lameness, and on synovial fluid, synovial membrane, and articular cartilage morphological parameters, both with direct intra-articular administration and remote site administration as compared to placebo treatment. The clinical use of IA administered TA in horses may be therapeutically beneficial in selected cases of osteochondral fragmentation and osteoarthritis.

Nonsteroidal anti-inflammatory drugs and corticosteroids for the management of canine osteoarthritis

Anti-inflammatory medications have long been prescribed for relief of the pain and discomfort associated with OA. This occurs despite the recognized side effects associated with use of NSAIDs and corticosteroids. Available evidence suggests that NSAIDs provide this relief through a combination of central and peripheral actions. Recent discovery of two isoforms of cyclooxygenase has increased our understanding of NSAID activity and may result in identification of drugs that potentially will have fewer side effects. A review of NSAIDs used in veterinary medicine indicates that relatively little is known regarding their role in treating OA, although controlled studies involving carprofen and etodolac have increased our knowledge of the efficacy of specific NSAIDs used for this purpose.

Intra-articular corticosteroids. Guide to selection and indications for use

Physicians have used intra- and periarticular corticosteroids for treating a variety of rheumatic diseases for nearly 50 years. Yet publications that have carefully examined the mechanisms of action, the pharmacokinetics and the comparative safety and efficacy of the available agents are sparse. This limits our ability to choose a drug scientifically. Similarly, we know little about the long term outcomes of joints infected with corticosteroids versus those not injected. Highly branched esters of methylprednisolone or triamcinolone are the preferred agents used by American rheumatologists. Pharmacokinetic studies reveal that triamcinolone hexacetonide, the least soluble of all the corticosteroid esters, is retained in the joint for 2 to 3 weeks. Intra-articular corticosteroids may implement their anti-inflammatory effect by down-regulating genetic expression of several pro-inflammatory proteins. A literature review suggests that judicious use of intra- and periarticular corticosteroids is very helpful in temporarily reducing pain and inflammation in musculoskeletal structures and may facilitate increased motion and function in selected cases. Their use in juvenile arthritis also appears to be safe and beneficial. Infection in or about the joint in the chief contraindication to use. Adverse effects are very few but the number of injections per joint should probably be limited to 4 or less per year.

Discoordinate gene expression of aggrecan and type II collagen in experimental osteoarthritis

OBJECTIVE

To quantify the gene expression of aggrecan core protein and type II collagen in an experimental animal model of osteoarthritis (OA).

METHODS

Total RNA was extracted from the articular cartilage of unoperated knee joints and from OA joints produced by anterior cruciate ligament transection. The relative amounts of type II collagen and aggrecan core protein messenger RNA (mRNA) were evaluated by Northern blot analysis.

RESULTS

Total RNA was elevated 2.5 times, aggrecan mRNA was elevated 2 times, and type II collagen mRNA was elevated 8 times, in OA knees compared to unoperated controls.

CONCLUSION

Chondrocytes are activated metabolically in response to joint injury. Discoordinate gene expression of aggrecan and type II collagen is characteristic of early experimental OA, and we speculate that it may contribute to its pathogenesis.

Fibroblast and neutrophil collagenases cleave at two sites in the cartilage aggrecan interglobular domain

The actions of recombinant human fibroblast collagenase (MMP1), purified polymorphonuclear leucocyte collagenase (MMP8) and their N-terminal catalytic domain fragments against cartilage aggrecan and an aggrecan G1-G2 fragment have been investigated in vitro. After activation with recombinant human stromelysin and typsin, both collagenases were able to degrade human and porcine aggrecans to a similar extent. An N-terminal G1-G2 fragment (150 kDa) was used to identify specific cleavage sites occurring within the proteinase-sensitive interglobular domain between G1 and G2. Two specific sites were found; one at an Asn341-Phe342 bond and another at Asp441-Leu442 (human sequence). This specificity of the collagenases for aggrecan G1-G2 was identical with that of the truncated metalloproteinase matrilysin (MMP7), but different from those of stromelysin (MMP3) and the gelatinases (MMP2 or gelatinase A; MMP9 or gelatinase B) which cleave at the Asn-Phe site, but not the Asp-Leu site. In addition, collagenase catalytic fragments lacking C-terminal hemopexin-like domains were tested and shown to exhibit the same specificities for the G1-G2 fragment as the full-length enzymes. Thus the specificity of the collagenases for cartilage aggrecan was not influenced by the presence or absence of the C-terminal domain. Together with our previous findings, the results show that stromelysin-1, matrilysin, gelatinases A and B and fibroblast and neutrophil collagenases cleave at a common, preferred site in the aggrecan interglobular domain, and additionally that both fibroblast and neutrophil collagenases cleave at a second site in the interglobular domain that is not available to stromelysin or gelatinases.

Immunological analysis of proteoglycan structural changes in the early stage of experimental osteoarthritic canine cartilage lesions

Specific modifications of the proteoglycan (PG) structure of osteoarthritic (OA) dog cartilage in relation to endogenous metalloprotease activity were examined using murine anti-proteoglycan monoclonal antibodies (MoAbs). OA lesions were induced over a period of 8 weeks in crossbred dogs (Pond-Nuki model). The articular cartilage was removed and homogenized in a Tris buffer, pH 7.5, and then divided into four groups: direct PG extraction, no addition, presence of 1 mM p-aminophenyl mercuric acetate (APMA), and presence of 1 mM APMA and 10 mM o-phenanthroline, incubated for 42 h at 37 degrees C followed by PG extraction. MoAbs reactive with PG protein and carbohydrate epitopes included 1C6, 3B3, 5D4, D1B2, and m4D6. The results showed marked alterations induced by APMA activation of the endogenous metalloproteases. PG changes were apparent at at least three sites: one was either in the hyaluronic acid-binding region or between the hyaluronic-binding region and the G2 globular domain, another was between the keratan-sulfate-rich domain and the chondroitin sulfate-attachment domain, and a third was in the chondroitin sulfate-attachment domain. Constitutive metalloprotease activity resulted in less marked PG alterations with preservation of functional PG aggregation to hyaluronan.

Increased release of matrix components from articular cartilage in experimental canine osteoarthritis

The release rates of specific components of the proteoglycan aggregates (G1 domain, the chondroitin sulfate and keratan sulfate containing portion of the protein core, and link protein) of the articular cartilage of mature beagles were studied at early stages of canine experimental osteoarthritis (OA), generated by transection of the anterior cruciate ligament. Analysis of cartilage explants and synovial fluids indicates that at early stages of experimental OA, there is increased release of the proteoglycan aggregates of the articular cartilage. This involves a release from the tissue of the components of the proteoglycan that are specifically involved with aggregation together with the glycosaminoglycans of the proteoglycan. These components were detected at elevated levels in the media of explants of cartilage from the operated joint, and in the synovial fluids of the operated joints.

Effects of anti-inflammatory drugs and agents that modify intracellular transduction signals or metabolic activities in inflammatory cells on interleukin-1 induced cartilage proteoglycan resorption in vitro

The actions of (a) anti-inflammatory drugs possessing a wide range of chemical structures and pharmacological actions, and (b) agents which modify intracellular transduction signals or metabolic functions were investigated for their potential to modify in vitro the proteoglycan (PrGn) resorption in bovine nasal cartilage induced by interleukin-1 alpha (IL-1). It was found that: (a) none of the conventional anti-inflammatory agents exhibited any inhibitory effects on IL-1 induced resorption of PrGns with the exception of the weak effects observed with the iron chelator, desferrioxamine, a cryogenine derivative JB-1-0, and myalex; (b) the antitumour agent cisplatin was a potent inhibitor but the analogue, transplatin, which does not inhibit DNA synthesis was without effect; (c) suramin, an inhibitor of cartilage degrading enzymes from leucocytes, also inhibited IL-1 induced resorption, as did natural somatomedin C (insulin-like growth factor = IGF alpha) but not agents previously shown to inhibit the lymphocyte mitogenic responses to IL-1 (e.g. alpha-melanocyte stimulating hormone, phenylglyoxal); (d) while no effects were observed with drugs that alter the intracellular production of cyclic AMP, those which affect uptake of calcium ions did inhibit proteoglycan resorption by IL-1. The results suggest that IL-1 induced cartilage PrGn degradation can be regulated at the level of transcriptional production of intracellular PrGn degrading enzymes or their activity, regulating calcium uptake into chondrocytes or by overcoming the PrGn degradation from IL-1 by stimulating the synthesis of these macromolecules.

Detection of Stromelysin and Collagenase in Synovial Fluid From Patients with Rheumatoid Arthritis and Posttraumatic Knee Injury

OBJECTIVE

To quantify stromelysin and collagenase in synovial fluid (SF) from patients with rheumatoid arthritis (RA) or traumatic knee injury.

METHODS

Stromelysin and collagenase were measured in the SF of 33 patients with RA or posttraumatic knee injury, using specific double-antibody sandwich enzyme-linked immunosorbent assays. Stromelysin was fractionated from representative SF, and the molecular form was identified by immunoblot analysis.

RESULTS

The stromelysin concentration was approximately 20-fold higher than the collagenase concentration in the fluids from patients with RA and approximately 8-fold higher in the fluids from patients with traumatic injury. For both metalloproteinases, there was a higher enzyme concentration in RA SF than in the SF from patients with trauma (stromelysin 40.1 +/- 26 micrograms/ml [mean +/- SD] in RA SF, 8.5 +/- 15 micrograms/ml in trauma SF; collagenase 2.2 +/- 3.3 micrograms/ml in RA SF, 1.1 +/- 2.3 micrograms/ml in trauma SF). The majority of the stromelysin within the SF bound to reactive red-agarose and was identified as prostromelysin based on electrophoretic mobility and immunoblotting with monospecific antibodies.

CONCLUSION

The finding of high levels of stromelysin in SF from patients with RA supports the proposal that this enzyme may play a role in the connective tissue degradation observed in this disease.

Proteinase-mediated cartilage degradation in osteoarthritis

Osteoarthritis (OA) is a disease of complex etiology that results in articular cartilage breakdown. Current experimental evidence strongly suggests that proteinases may be involved in this loss of cartilage matrix. The present review summarizes the evidence for implicating proteinases in the etiopathogenesis of OA and suggests that blockade of proteinase activity may provide a rational basis for new therapeutic agents.

Amelioration of lapine osteoarthritis by treatment with glycosaminoglycan-peptide association complex (Rumalon)

The chondroprotective potential of glycosaminoglycan-peptide association complex (GP-C) was examined in the medial meniscectomy model of lapine osteoarthritis (OA). Prophylactic treatment with increasing doses of intramuscular GP-C (0.05-0.5 ml/kg) caused a significant reduction in OA lesion area and histologic scores, and the effect on disease activity appeared to be dose related. The DNA and uronic acid contents of OA tissue were unaffected by prophylactic treatment with GP-C. However, levels of hydroxyproline in OA cartilage increased to near control levels with prophylactic treatment. Cartilage levels of active and total metalloproteinases that digest proteoglycans were elevated in rabbits with OA; prophylactic treatment with low-dose GP-C (0.05 ml/kg) produced a significant reduction in active, but not total, enzyme. Cartilage levels of tissue inhibitor of metalloproteinases in animals with OA were comparable with control levels, but rose with increasing doses of GP-C. We also investigated GP-C as a therapeutic treatment in animals that had already developed OA lesions. Carbon black retention and histologic score returned to near-normal after therapeutic treatment with GP-C. Uronic acid and hydroxyproline levels were decreased in OA cartilage. Therapeutic treatment with GP-C had no statistically significant effect on uronic acid levels, but was associated with increased hydroxyproline content in the cartilage. The changes in metalloproteinase and metalloproteinase inhibitor were similar to those found in the studies of prophylactic treatment. The findings in this animal model may help explain some of the beneficial effects of GP-C in human OA.

Glycosaminoglycans in horses with osteoarthritis

Horse articular cartilage glycosaminoglycans (GAGs) were measured in synovial fluids from 48 joints affected with osteoarthritis (OA), 22 normal joints, four joints with osteochondritis, three joints with traumatic arthritis and seven joints infected with bacteria. Serum and urine from individual horses were also examined for the presence of GAGs. High levels of GAGs were found in synovial fluids (SF) from horses with OA. In each case, the level was higher in the synovial fluid than in the serum or urine from the same horse. Horses with OA showed high GAG levels in SF, serum and urine compared to horses with normal and infected joints. High levels were also found in horses with osteochondritis and traumatic arthritis. Levels of synovial fluid GAG reflect cartilage destruction in arthritis and may be useful for monitoring disease progression in the equine species.

Type XI collagen-degrading activity in human osteoarthritic cartilage

Homogenates of 6 samples of human osteoarthritic cartilage were shown to degrade exogenous type XI collagen. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the cleavage products generated by each homogenate were similar, and they were identical to those obtained by cleavage of the substrate with purified gelatinase. Enzyme activity, which was inhibited by EDTA, was greater in extracts of fibrillated osteoarthritic cartilage than in extracts of grossly normal cartilage from the same joint or in extracts of cartilage from joints with osteonecrosis. Activation with APMA enhanced digestion, but breakdown was apparent in extracts of fibrillated osteoarthritic cartilage even without APMA. Enzymatic degradation of type XI collagen could play a significant role in the turnover of articular cartilage in health and disease states.

Imbalance between the mechanisms of activation and inhibition of metalloproteases in the early lesions of experimental osteoarthritis

Levels of tissue inhibitor of metalloproteases (TIMP) and plasminogen activator (PA)/plasmin were measured and the distribution of PA was studied by immunohistochemical techniques in cartilage and synovium samples from dogs subjected to sectioning of the anterior cruciate ligament of their right knees and sham operation of their left knees (controls). Twenty-three animals were divided into 3 groups and killed at 2, 4, or 8 weeks after surgery. The levels of PA and plasmin were found to be significantly elevated in the osteoarthritic (OA) knee cartilage and synovium at all times after surgery, except for levels of PA in the OA cartilage at 2 weeks. There was a positive correlation between the levels of PA and plasmin in the synovial membrane (r = 0.64, P less than 0.001). In OA knees, the presence of high levels of total and active collagenase was detected in cartilage and in synovium. The levels of these 2 forms of collagenase showed a positive correlation both in cartilage (r = 0.65, P less than 0.001) and in synovium (r = 0.77, P less than 0.001). The levels of TIMP in cartilage from OA and sham operated knees were similar. Although the TIMP level was increased in the OA synovium, it was found only in trace amounts in cartilage. Immunohistochemical studies revealed that both forms of PA, urokinase-type PA and tissue-type PA, and TIMP were present in OA tissues. In the synovium, they were found mainly in monocyte/macrophages, synovial lining cells, and blood vessel cells. In OA cartilage, PA was present only at the superficial level in chondrocytes and in cartilage matrix, whereas TIMP was present in chondrocyte lacunae throughout the full thickness of the cartilage. TIMP was also detected in the superficial level of cartilage from sham operated knees. The results of this study indicate that in OA tissues, there are conditions that favor the synthesis and activation of metalloproteases. PA and plasmin are likely to play an important role in the physiologic activation of metalloproteases, although they are probably not the only system involved in this process. The lack of increased TIMP levels in the OA cartilage, in the presence of increased metalloprotease activity, is also a possible contributing factor in the enzymatic degradation of this tissue.

Spontaneous osteo-arthritis of the knee-joint in C57BL mice receiving chronic oral treatment with NSAID's or prednisone

In a statistically planned study based on quantitative radiography, treatment for 25-26 weeks with the 2 NSAIDs, diclofenac sodium, or indomethacin (both 0.5 and 1.5 mg/kg p.o. daily), or prednisone (6 mg/kg p.o.) had no influence on the progression of spontaneous osteo-arthritis of the knee-joint of the C57BL mouse, by comparison with placebo-treated controls.

Osteoarthritis research: animal models

Although limited in scope and detail, the current review has sought to highlight the contribution of animal models in the study of OA. Further use of these and other models should provide information that may lead to methods for the early detection and successful treatment of human OA.

Therapeutic treatment of canine osteoarthritis with glycosaminoglycan polysulfuric acid ester

The therapeutic effect of glycosaminoglycan polysulfuric acid ester (GAGPS) was studied using the Pond-Nuki model of canine osteoarthritis. The clinical setting was simulated by permitting 4 weeks ambulation without treatment, following anterior cruciate transection. Animals were then injected with GAGPS, 4 mg/kg intramuscularly, twice weekly during weeks 4-8. Control animals received intramuscular saline. The study was terminated 4 weeks after completion of the GAGPS or saline regimen (i.e., 12 weeks postoperatively). Cartilage from the medial femoral condyle was analyzed for collagen integrity (swelling properties), hydroxyproline, uronic acid, active and total proteoglycan (PG)-degrading metalloproteinase, PG-degrading serine proteinase, and histopathology (Mankin score). Condylar cartilage from animals treated with GAGPS demonstrated less cartilage swelling, less total and active metalloproteinase, and lower histopathologic scores than were found in cartilage from saline-treated animals. GAGPS was able to suppress PG-degrading enzyme activity and maintain a more normal-appearing cartilage. It is proposed that GAGPS suppressed PG breakdown by decreasing synthesis of metalloproteinase or by directly inhibiting metalloproteinase in cartilage, rather than by increasing synthesis of PG by chondrocytes.

Evidence for metalloproteinase and metalloproteinase inhibitor imbalance in human osteoarthritic cartilage

Cartilage specimens from tibial plateaus, obtained from 13 osteoarthritic (OA) patients and seven controls, were selected from three regions: zone A, center of fibrillated area; zone B, area adjacent to fibrillation, and zone C, remote region of plateau. Acid and neutral metalloproteinases and tissue inhibitor of metalloproteinase (TIMP) were extracted with 2 M guanidine. Methods were developed to selectively destroy either proteinases or TIMP to prevent cross-reaction during assay. Acid and neutral proteinases were elevated approximately 150% in OA; TIMP was elevated approximately 50%. A positive correlation (r = 0.50) was found between acid and neutral proteinase activities in OA, but not in controls. Both proteinases were elevated two-to threefold in zones A, B, and C. However, the self-active form of the acid metalloproteinase was elevated only in zones A and B (200%); it correlated well with the Mankin scores, whereas the total activities did not. TIMP was elevated (50%) only in zones A and B. Both the proteinase levels and the Mankin score were elevated to a greater extent in the medial, than in the lateral, compartment. Titration of TIMP against the two metalloproteinases indicates that there is a small excess of inhibitor over enzymes in normal cartilage. In OA, TIMP does not increase to the same extent as the proteinases; the resultant excess of proteinases over TIMP may contribute to cartilage breakdown.

Prophylactic treatment of canine osteoarthritis with glycosaminoglycan polysulfuric acid ester

The prophylactic effect of glycosaminoglycan polysulfuric acid ester (GAGPS) on cartilage lesions was studied using the Pond-Nuki model of canine osteoarthritis. Starting 2 days after anterior cruciate transection, GAGPS or saline was administered intraarticularly twice weekly for 4 weeks. After 4 weeks, gross and histologic medial femoral condylar lesions had developed to a lesser degree in GAGPS-treated dogs than in saline-treated dogs. The uronic acid and hydroxyproline levels in cartilage were significantly higher in the GAGPS-treated dogs than in the saline-treated dogs. Levels of active and latent collagenase in the cartilage of GAGPS-treated dogs were lower than in the cartilage of saline-treated dogs. With GAGPS treatment, swelling of the cartilage, an indicator of collagen network integrity, remained near control levels. Although increased synthesis of proteoglycan and collagen may account for some of these results, we propose that one mechanism of action of GAGPS is its ability to decrease collagen degradation, either by decreasing the synthesis of collagenase or by directly inhibiting the production of collagenase in cartilage.

Protective effects of corticosteroids on cartilage lesions and osteophyte formation in the Pond-Nuki dog model of osteoarthritis

The in vivo effects of corticosteroids on osteoarthritic (OA) lesions were examined in 12 dogs in which the anterior cruciate ligament had been sectioned. Six were treated with oral prednisone and 6 were treated with intraarticular (IA) injections of triamcinolone hexacetonide (TH), at surgery and 4 weeks later. Twelve other operated dogs received no treatment. All dogs were killed 8 weeks postsurgery. Four of 15 normal control dogs received IA TH injections. Operated untreated dogs developed significant cartilage lesions on the femoral condyles and tibial plateaus with prominent osteophytes. Operated dogs treated orally or with IA injections had a significant reduction in osteophyte size. Cartilage erosions on femoral condyles were observed in 25% of the untreated dogs, 8% of the dogs receiving oral prednisone, and none of the dogs receiving IA TH. In both groups of treated dogs, the size of the tibial plateau lesions was significantly reduced compared with the operated untreated dogs. Histologically, corticosteroids significantly reduced the severity of OA structural changes of the cartilage on both medial and lateral femoral condyles and tibial plateaus in operated animals, with the exception of the lateral plateaus of those treated orally. In electron microscopy studies, we found no evidence of increased cell degeneration or death associated with steroids. IA corticosteroids had no deleterious effects on normal articular cartilage. These results indicate that glucocorticoids administered orally or intraarticularly are effective against the development of OA lesions in this model.

Changes in the sedimentation profile of proteoglycan aggregates in early experimental canine osteoarthritis

Osteoarthritis was induced in 12 normal dogs by severing of the anterior cruciate ligament of the right knees, the left knees serving as sham operated controls. The animals were killed at 7 and 14 weeks postsurgery. The total hexuronate, and thus proteoglycan, content of the articular cartilage of operated knees remained unaltered during the period of study. After pretreatment with a highly purified collagenase and in the presence of selected protease inhibitors, a higher proportion of the tissue hexuronate could be extracted from the different topographical areas of osteoarthritic joints under non dissociative conditions (70-75% versus 55-65% for control knees). The nondissociatively recovered osteoarthritic proteoglycans (a-A1 preparations) displayed progressive and consistent changes in their sedimentation profile. First, the size of the fast sedimenting or more saturated aggregates appeared to be reduced in the different regions of osteoarthritic joints at 7 weeks postoperatively. The disappearance of the faster sedimenting mode as well as a dramatic increase in the proportion of monomers were only detected in the topographical zones exhibiting the most severe surface damage and histologic abnormalities at 14 weeks postsurgery. The proteoglycan molecules present as "free" or "nonaggregated" monomers in a-A1 preparations recovered from normal and osteoarthritic cartilage at different time periods after surgery were separated from their corresponding aggregates by rate zonal centrifugation in isokinetic cesium sulfate gradient. Although they were severely depleted in keratan sulfate, the purified "free" and "aggregated" osteoarthritic monomers appeared to be normal in terms of aggregating capacity and size distribution, and were therefore not degraded. This progressive changes in size distribution of proteoglycan aggregates in the early stages of experimental canine osteoarthritis could contribute significantly to the biochemical and biomechanical alterations of osteoarthritic cartilage.

Anti-rheumatic drugs and cartilage

In this chapter an attempt has been made to draw together the known biology of cartilage and some of the mechanisms thought to be responsible for its failure in arthritis. The picture is far from complete but we are now in a good position to use this information to help appraise the pros and cons of the wide range of drugs now available to treat articular disorders. For convenience, these drugs were classified as NSAIDs, corticosteroids and chondroprotective agents. The influence of each of these classes on the metabolism of cartilage was examined in the light of published laboratory and clinical studies. It has been clearly shown that not all NSAIDs are the same. While many of the older drugs provided no benefit to cartilage metabolism, and in some instances suppressed it, the more recently discovered molecules appear to be free of these undesirable effects. Tiaprofenic acid, diclofenac and piroxicam emerged as drugs with little or no harmful effects on cartilage metabolism when used at concentrations within the human therapeutic range. For all NSAIDs, their potential effects on cartilage must be weighed against their respective anti-inflammatory potency, half-life, and effects on the gastric mucosa and other tissues. Other chapters in this book have addressed these important problems. The long-acting corticosteroids, betamethasone and triamcinolone hexacetonide, also appear to offer some benefit in the management of OA; however, as in RA, their use should be restricted to short-term applications. In terms of cartilage metabolism the chondroprotective agents pentosan polysulphate, Arteparon and Rumalon have been the most extensively studied class of drugs. While the laboratory studies have provided convincing evidence of their chondroprotective efficacy, it has been difficult to prove this clinically. This dichotomy of opinion (laboratory versus clinical) stems largely from the inadequacy of the methodologies currently available for the objective clinical assessment of patient response to anti-rheumatic drug therapy. With the advent of nuclear magnetic resonance imaging techniques and monoclonal antibodies to detect specific proteoglycan breakdown fragments in synovial fluid and plasma, the prospects for a unified research approach for the evaluation of these agents may now be possible.

Progressive depletion of hyaluronic acid in early experimental osteoarthritis in dogs

The hyaluronic acid (HA) content of articular cartilage was studied in early experimental osteoarthritis (OA) in 16 normal dogs. The anterior cruciate ligament in the right knees of the dogs was transected; their left knees served as sham operated controls. The animals were killed at 7 and 14 weeks postsurgery. Although their total hexuronate, and thus proteoglycan, content remained unaltered during the period of study, the different weight-bearing areas of the OA knees displayed a progressive and significant decrease in HA content. We found no differences in the molecular weight and in vitro aggregating capacity of the HA molecules from OA cartilage versus those from control cartilage. This early relative depletion of HA could contribute significantly to the biochemical alterations of OA cartilage. Furthermore, it appears to be a good parameter for the differentiation of changes related to OA and changes related to aging.

Degradation of rat chondrosarcoma proteoglycans by a neutral metalloprotease from rabbit chondrocytes

Rat chondrosarcoma proteoglycan aggregate with radiolabeled core protein was digested with a chondrocyte metalloprotease (CMP) or clostripain (CP) at neutral pH. The rates of product formation and the sizes and antigenicities of the products were studied using column chromatography and monoclonal antibodies. Sixteen percent of [35S]methionine label and 17-18% of [3H]serine label in core protein were freed from glycosaminoglycan bound peptides by 50 U/ml (760 micrograms/ml) of CP or 10 micrograms/ml (estimated) of CMP in 180 min. The CP reaction was almost complete at 5 minutes while the CMP reaction proceeded slowly from 5 to 180 min. The chondroitin-sulfate rich fragments were smaller after CP than CMP treatment. The 180 min CMP digest contained protein that migrated in 2 peaks on Sepharose CL6B. These two peaks corresponded to the peaks where hyaluronic acid binding region produced by CP and link protein migrate. Metalloenzyme inhibitors inhibited CMP with IC50s of 5 x 10(-5)M, 1 x 10(-3)M, and 80 micrograms/ml for phenanthroline, EDTA, and alpha 2-macroglobulin, respectively.

Protease inhibitors decrease rabbit cartilage degradation after meniscectomy

In vitro proteoglycan (PG) synthesis and release were measured on cartilage removed from rabbit knees within 1 week of meniscectomy. Three days following partial lateral meniscectomy, 72% of the femurs and 82% of the tibias had visible ulcers. Cartilage from the weight-bearing areas incorporated 2.0-2.9 times more 35S-sulfate in vitro than cartilage from the opposite, unoperated knees. 3H-thymidine incorporation was 2.5-3.4 times higher for surgical than control groups. 35S-sulfate incorporation by the surgical group was inhibited by 22% in the presence of 10(-4) M U24522, an inhibitor of rabbit chondrocyte metalloprotease (CMP). 3H-thymidine incorporation by the surgical group was inhibited by 28% by 10(-4) M U24522. In vitro PG release from cartilage removed 2 days after surgery was 1.6-3.7 times higher for the surgical than the control group. PG release by the surgical group after 22 h of incubation was reduced to the control level by three CMP inhibitors, U24278, U24279, and U24522. PG release by cartilage from the nonsurgical group was also reduced by these compounds at 22 h. These results suggest that both the anabolic and catabolic processes that are stimulated by surgery can be isolated in vitro and that CMP may be involved in the catabolic process.

Cartilage degradation by neutral metalloproteases in experimental collagen-like syndrome

In this study, we sought to determine the role of neutral proteases in cartilage matrix proteoglycan degradation, which occurs during the experimental hydralazine-induced collagen-like syndrome (c-l-s) in rats. The digestion of endogenous proteoglycans by neutral proteases in homogenates of cartilage from rats with c-l-s has been measured and compared with that of normal age-matched controls. Cartilage specimens from the tibial plateau were analysed for DNA and proteoglycan content, and neutral proteoglycan-degrading activity, No significant difference in cartilage DNA concentration was observed among the rats with c-l-s and the controls. Total neutral proteoglycan-degrading metallo-enzyme activity, determined by direct tissue assay, was significantly higher in c-l-s cartilage than that in control cartilage. Serine protease activity on proteoglycans was much lower than that of metalloprotease. The results of this study are consistent with the hypothesis that the neutral metalloproteases of cartilage are involved in the degradation of proteoglycans in c-l-s.

Canine osteoarthritis: effects of endogenous neutral metalloproteoglycanases on articular cartilage proteoglycans

The aim of this study was to analyze the mechanisms by which neutral metalloproteoglycanases (NMPE) degrade proteoglycans (PGs) in the cartilage of an experimental model of osteoarthritis (OA). We demonstrated that chondrocytes in osteoarthritic cartilage synthesize PGs with the same functional characteristics as those found in normal cartilage. Osteoarthritic cartilage contains NMPE in both active and latent forms. Both forms can degrade newly synthesized and endogenous PG macromolecules, as indicated by the reduced hydrodynamic size found in the two PG populations of osteoarthritic cartilage. PG monomers, derived from the included fraction of Sepharose CL2B chromatography, were unable to form aggregates with hyaluronic acid. Reduction and alkylation showed that PG monomers from osteoarthritic cartilage had a small hydrodynamic size, especially after activation with amino-phenylmercuric acetate. No significant differences were observed in the size of the chondroitin sulfate chain when normal cartilage was compared with its osteoarthritic equivalent. These results suggest that the proteolytic degradation of cartilage matrix PGs by NMPE occurs at both the hyaluronate-binding region and at the chondroitin sulfate-rich region of the core protein.

Neutral metalloproteases and age related changes in human articular cartilage

A decrease in proteoglycan (Pg) content and disturbances in the collagen network have been reported in aging cartilage. This study aims to determine whether these changes are associated with proteolytic enzymes such as neutral metalloproteases. Eighty lateral tibial plateaus were collected from subjects after death. The age, topographical area, and lesion severity (macroscopic grading) of each specimen were noted and the effects of neutral metallo-Pg-degrading and collagenolytic enzymes on these specimens were compared. The specimens were divided into two age groups: 20-50 years (group 1) and greater than 50 years (group 2). They were selected from both weight bearing and non-weight bearing areas. In some cartilage tissues the superficial layer was separated from the deep zone. Our data for the two neutral metalloenzymes examined showed: no correlation between enzyme activity and age when the specimens were of the same grade and a statistically significant rise in the enzyme levels of the older specimens, which increased as the lesions progressed. Neutral metallo-Pg-degrading enzyme activity was higher in non-weight bearing areas than in weight bearing areas, and this reached a statistical difference in the older cartilage with advanced lesions. The Pg-degrading enzyme activity was raised in the superficial layers of damaged cartilage tissue. Our data suggest that neutral metalloproteases are closely associated with the appearance and progression of the changes seen in aging cartilage.

Proteoglycan-degrading acid metalloprotease activity in human osteoarthritic cartilage, and the effect of intraarticular steroid injections

Cartilage samples from both the immediate and remote lesion areas were obtained from the tibial plateaus of 21 patients with osteoarthritis, and were subjected to histologic and enzymatic study. There was a frequent loss of pericellular metachromatic staining in the OA cartilage. Seven patients had received intraarticular injections of steroids, and in 21% of those cartilage samples, a pericellular halo was seen. This halo was seen in 71% of patients who had not received steroid injections. The total acid metalloprotease activity was increased more than twofold in specimens from OA lesions and in those samples graded moderate, as compared with age-matched control cartilages. These differences were greater when the specimens from patients who had received steroid therapy were excluded from the data. The cartilage specimens from steroid-treated patients were not significantly different from those of controls with respect to the enzyme activity in the lesions or in cartilage with moderate disease. The active form of the protease was suppressed by steroids. In samples from patients who did not receive steroid injections and who had a moderate grade of OA, a significantly elevated level of the active protease was present, as compared with control samples. Those samples graded moderate which came from patients who received steroid treatments showed no difference in the active protease level versus that of controls. Our results are consistent with the hypothesis that acid metalloprotease activity is involved in the degradation of the cartilage matrix in OA. Since the protease retains a significant fraction (40%) of its activity at neutral pH, its physiologic role might occur either at acid pH or at neutral pH.(ABSTRACT TRUNCATED AT 250 WORDS)