Metabolic changes in rabbit articular cartilage due to inflammation

A novel derivative pentacyclic triterpene and omega 3 fatty acid

Adjuvant induced arthritis (AIA) is accompanied by marked changes in the levels of lysosomal enzymes, glycoproteins and metabolic turnover of collagen. The role of a pentacyclic triterpene and eicosapentaenoic acid (EPA) derivative--Lupeol-EPA (50 mg/kg body weight--orally) was tested in vivo in rats. The increased activities of lysosomal enzymes and glycoproteins associated with decreased collagen in arthritic animals were significantly altered to nearly that of controls. Indomethacin (3 mg/kg body weight) was used as a reference compound. The therapeutic usefulness of Lupeol-EPA derivative in inflammatory conditions is attractive and deserves further work in this direction.

An N-terminal peptide from link protein can stimulate biosynthesis of collagen by human articular cartilage

Previous studies have shown that a peptide identical in sequence to the N-terminal of link protein can function as a growth factor and up-regulate proteoglycan synthesis by human articular cartilage in explant culture (L. A. McKenna et al., Arthritis Rheum. 41, 157-162, 1998). The present study has extended these investigations to determine the effects of this peptide on the synthesis of collagen, another essential component of normal cartilage matrix. Explants from normal adult knee cartilage were maintained for periods of up to 8 days in medium with or without serum. Peptides were added during each day of culture. Synthesis of collagen was determined by the incorporation of [3H]proline into hydroxyproline and proteoglycans by incorporation of [35S]sulfate. The type of newly synthesized collagen was measured by SDS-polyacrylamide gel electrophoresis, fluorography, and immunoblotting. The link protein peptide stimulated synthesis of type II collagen in cartilage from a number of different subjects. Maximum up-regulation of synthesis was attained at a concentration of 100 ng/ml, similar to that observed previously for up-regulation of proteoglycan. Synthesis was up-regulated in both the presence and the absence of serum, although the overall rate of synthesis was greater when serum was added. The findings that this link peptide growth factor stimulated synthesis of proteins, including collagen, in a manner analogous to that shown previously for proteoglycans support the hypothesis that this peptide may have an important role in the feedback control of cartilage matrix synthesis.

Perspectives: a biomechanical model of the pathogenesis of arthroses

This model views the common, initiating cause of arthroses as excessive articular cartilage microdamage. If so, understanding it would become a central problem for understanding the pathogenesis of arthroses. The model proposes the microdamage can stem from: (1) Excessive total loads on normal joints; (2) underadaptations in a joint's size or shape that leave its momentarily loaded area too small for normal loads; (3) impaired microdamage repair in subchondral bone or articular cartilage; (4) abnormal composition or structure that makes a tissue develop excessive microdamage under normal loads. (5) (2)-(4) above could stem from changed set points or "lead times" for a joint's adaptations and maintenance, which in turn could stem from (6) genetic influences, some drugs, toxins, diseases, and "X," and (7) from combinations of the above. In the pathogenesis of arthroses this model assigns special importance to the stiffness of joint tissues (as distinguished from their strength), to the typical largest unit loads they carry as a result of a subject's usual physical activities, and to microdamage in those tissues.

Animal models for osteoarthritis: processes, problems and prospects

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Studies on the metabolism of glycosaminoglycans under the influence of new herbal anti-inflammatory agents

The in vivo effect of an herbal based, non-steroidal anti-inflammatory product, salai guggal, prepared from the gum resin exudate of Boswellia serrata and its active principle "boswellic acids" on glycosaminoglycan metabolism has been studied in male albino rats. The biosynthesis of sulfated glycosaminoglycans, as evaluated by the uptake of [35S]sulfate, and the content of glycosaminoglycans were measured in specimens of skin, liver, kidney and spleen. Statistical analysis of the data obtained with respect to the boswellic acids and salai guggal were compared with those of ketoprofen. A significant reduction in glycosaminoglycan biosynthesis was observed in rats treated with all of the drugs. Glycosaminoglycan content was found to be decreased in the ketoprofen-treated group, whereas that of the boswellic acids or salai guggal treated groups remained unaltered. The catabolism of glycosaminoglycans was followed by estimating the activities of lysosomal glycohydrolases, namely beta-glucuronidase, beta-N-acetylglucosaminidase, cathepsin B1, cathepsin B2 and cathepsin D, in tissues and by estimating the urinary excretion and hexosamine and uronic acid. The degradation of glycosaminoglycans was found to be reduced markedly in all drug-treated animals as compared to controls. The potential significance of boswellic acids and salai guggal was discussed in the light of changes in the metabolism of glycosaminoglycans.

Collagen types in neocartilage tissue resulting from rib perichondrial graft in an articular defect--a rapid semi-quantitative methodology

A method for estimating type II to type I collagen ratios in small tissue samples has been developed. The cyanogen bromide peptides of the tissue collagens were analyzed by SDS-gel electrophoresis. Marker peptides representative of each collagen type were established and their relative amounts determined by integration of the stained peptide bands following gel scans. Marker peptide ratios were then computed for each of several standard type II/type I mixtures and these peptide ratios were mathematically correlated with the corresponding type II/type I collagen ratios. A linear relationship between marker peptide ratio and collagen type ratio was established. This relationship was applied to the analyses of type II/type I ratios in samples of rib perichondrium and neocartilage derived from perichondrial graft repairs of full thickness femoral condyle defects. The results indicated that perichondrial grafts synthesize both types II and I collagens and that the proportion of type II increases with increasing post-transplant time.

Inhibition of neutrophil activation by nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs are thought to prevent inflammation in rheumatoid arthritis by inhibiting prostaglandin synthesis. This observation does not explain, however, why nonsteroidal anti-inflammatory drugs are able to control inflammation caused by other mediators. To determine whether nonsteroidal anti-inflammatory drugs also exert an effect on neutrophil activation, in vitro and in vivo studies were undertaken. Aggregation, superoxide anion generation, and lysosomal enzyme release were assessed. The nonsteroidal anti-inflammatory drugs were found to inhibit these neutrophil responses, but the patterns of inhibition varied from drug to drug. These findings suggest that nonsteroidal anti-inflammatory drugs may have direct effects on neutrophil activation that are independent of their shared inhibition of prostaglandin synthesis.

The inactivation of the polymorphonuclear leukocyte by non-steroidal anti-inflammatory drugs

When human neutrophils (PMNs) are activated by appropriate stimuli, they aggregate, generate superoxide anion (O2-) and secrete lysosomal enzymes. Pre-incubation of PMNs in vitro with the cyclo-oxygenase (COx) inhibitor piroxicam (50 microM) before stimulation with the chemotactic peptide f-met-leu-phe (FMLP, 10(-7)M) inhibited all of these responses. The COx inhibitor ibuprofen inhibited FMLP-induced aggregation and lysozyme secretion, leaving O2- generation unaffected. Binding of 3H-FMLP was inhibited by piroxicam. When the plant lectin concanavalin A (Con-A, 30 micrograms/ml) or the tumor promoter phorbol myristate acetate (PMA, 50 micrograms/ml) was used as a stimulus, ibuprofen had no effect on PMN response, while piroxicam inhibited only O2- generation. To determine whether such inhibition might also occur in vivo, we tested neutrophil aggregation and O2- generation in response to FMLP in 26 normal subjects. These subjects were then administered therapeutic doses of piroxicam (20 mg/day), ibuprofen (2400 mg/day) or indomethacin (100 mg/day), and neutrophil functions were retested after 3 days. Piroxicam inhibited FMLP-induced aggregation by 31% (5.2 cm2/min versus 3.6 cm2/min, P less than 0.004) and O2- generation by 35% (15.8 nmol cytochrome c reduced versus 10.2 nmol, P less than 0.002). Ibuprofen inhibited FMLP-induced aggregation by 44% (5.2 versus 3.0, P less than 0.03) but had no effect on O2- production. Indomethacin inhibited FMLP-induced aggregation (6.4 versus 2.9, P less than 0.01) but had no effect on O2- generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase in the activity of lysosomal acid hydrolases in the chondrocytes of arthritic joints of rabbits with experimental allergic arthritis

Undecalcified cryostat sections of the cartilage-covered ends of the femurs have been prepared from the control and inflamed knees of rabbits with experimental allergic arthritis. The activities of two lysosomal hydrolases, naphthylamidase and beta-glucuronidase, were assayed in the chondrocytes of the articular cartilage in such sections by scanning and integrating microdensitometry. The activities of both enzymes were found to increase significantly in the chondrocytes of the inflamed joints.

Hypothesis: joints can heal

Although cartilage has a limited capacity for intrinsic repair, cells extrinsic to the cartilage can provide a mechanism for repair if the proper conditions exist. The new chondroid material produced, although not histologically or biochemically identical to mature hyaline articular cartilage, can nevertheless in many circumstances permit normal joint function and prevent further joint deterioration. The evidence suggests that joint healing results from establishing a source of cells, normalizing joint pressures, and encouraging joint motion. Much of the controversy surrounding the question of whether joints can heal results from a failure to view joint function, rather than cartilage appearance, as the most important component of the healing process, and to appreciate the significant role played by mechanical factors in promoting this response.

Type II collagen-induced arthritis. A morphologic and biochemical study of articular cartilage

Articular cartilage was obtained from type II collagen-induced arthritic rat joints. Transmission electron microscopy showed a gradual degeneration of chondrocytes, disorganization of the collagenous extracellular matrix, and formation of microscars. Biochemical analyses indicated that type II collagen was the only collagen present and that it was normal in regard to hydroxylation of lysine and glycosylation of hydroxylysine. Analyses of the proteoglycan in the extracellular matrix revealed a 50% loss of chondroitin sulfate and keratan sulfate.

The neutrophil in rheumatoid arthritis: its role and the inhibition of its activation by nonsteroidal antiinflammatory drugs

The activation of the polymorphonuclear leukocyte (PMN) in rheumatoid arthritis produces toxic products that include lysosomal enzymes, stable prostaglandins, and leukotrienes and causes the release of superoxide anion. These products produce the inflammatory response, damage cell membranes, and degrade hyaluronic acid. The inhibition of prostaglandin synthetase by NSAIDs does not, by itself, account for their effectiveness in preventing inflammation in rheumatoid arthritis. In vivo and in vitro experiments were conducted to determine if NSAIDs also exert an effect on neutrophil activation. The NSAIDs tested inhibited discrete PMN functions dependent upon the stimulus tested. The antiinflammatory effects of NSAIDs cannot be entirely explained by their inhibition of prostaglandin synthetase and may, in part, be due to other direct effects upon inflammatory cell activation.

Collagenase and collagenolytic activity in human osteoarthritic cartilage

Forty-nine specimens of human cartilage were taken from 3 sites on the tibial plateau (center of osteoarthritic lesion, edge of lesion, and remote site) and graded histologically by the scale of Mankin. The tissue was homogenized and centrifuged to obtain an insoluble pellet. This was resuspended in buffer and incubated at 37 degrees C, pH 7.5. Collagen digestion was quantitated by the release of hydroxyproline-containing peptides. The highest collagenolytic activity (4.6%) was found in the center of lesions, declining in remote sites to 2.4% and in controls to 1.1%. Moderately severe disease of grade 6--9 had the highest collagenolytic activity. Approximately 55% of the metal-dependent collagenolytic activity was in a latent form, activatable by amino-phenylmercuric acetate; the remainder was self-active. A method was developed for the extraction of collagenase from cartilage; the extracted enzyme produced the typical 75:25 cleavage products of type I collagen.

Wolcott-Rallison syndrome: diabetes mellitus and spondyloepiphyseal dysplasia

In 1972, Wolcott and Rallison described three siblings with a combination of infancy-onset diabetes mellitus and multiple epiphyseal dysplasia. We have observed a brother and sister with the same disorder. The chondro-osseous lesions are those of a spondylo-epiphyseal dysplasia. The diabetes mellitus is relatively mild. Histologic and electron microscopic studies of chondro-osseous tissue show findings similar to those in other epiphyseal and spondylo-epiphyseal dysplasias. In addition, however, atypical collagen-like fibres are found inside and outside chondrocytes. Collagen production seems to be normal in cultured fibroblasts. From the available data it appears that the association of characteristic chondro-osseous and endocrine abnormalities is non-random and that the lesions are independent manifestations of a pleiotropic gene. We propose to call this disorder the Wolcott-Rallison Syndrome.

Biochemical changes of intervertebral discs in patients with spondylolisthesis or with tears of the posterior annulus fibrosus

Surgically removed discs from patients with either spondylolisthesis or tears of the posterior annulus fibrosus were analysed for water, proteoglycan, and collagen content and compared with post-mortem control material. Discs from patients with spondylolisthesis had a reduced proteoglycan content in all section sampled and less collagen in the outer annular layers. In contrast discs containing tears in the posterior annulus were unaltered biochemically, although extended studies on 2 patients indicated that there may be localised biochemical changes in the region of the tear itself. Collagen types I, II, and III and proteoglycan distributions were studies qualitatively by immunofluorescence. Collagen types I and III appeared to be reduced in discs from patients with spondylolisthesis, but again little change was found in patients with tears in the posterior annulus fibrosus.

Effect of indomethacin and naproxen on the metabolism of glycosaminoglycans

Indomethacin and naproxen were examined regarding their effects on glycosaminoglycan metabolism in normal albino rats. The biosynthesis of sulphated glycosaminoglycans as evaluated by the uptake of [35S-]sulphate and the content of glycosaminoglycans were measured in specimens of skin, liver and kidney. The results indicated that the biosynthesis of sulphated glycosaminoglycans was significantly inhibited by both these drugs, thus reflecting their anti-inflammatory properties. The catabolism of glycosaminoglycans was followed by estimating the activities of lysosomal glycohydrolases, viz., beta-glucuronidase, beta-N-acetyl glucosaminidase and cathepsin D in liver, kidney and spleen and urinary excretion of hexosamine and uronic acid. The results, considered collectively, indicated that both indomethacin and naproxen depressed the metabolism of glycosaminoglycans.

Biosynthesis of collagen and other matrix proteins by articular cartilage in experimental osteoarthrosis

Osteoarthrosis was induced in one knee joint of dogs by an established surgical procedure. Changes in the articular cartilage in the biosynthesis of collagen and other proteins were sought by radiochemical labelling in vivo, with the following findings. (1) Collagen synthesis was stimulated in all cartilage surfaces of the experimental joints at 2, 8 and 24 weeks after surgery. Systemic labelling with [3H]proline showed that over 10 times more collagen was being deposited per dry weight of experimental cartilage compared with control cartilage in the unoperated knee. (2) Type-II collagen was the radiolabelled product in all samples of experimental cartilage ranging in quality from undamaged to overtly fibrillated, and was the only collagen detected chemically in the matrix of osteoarthrotic cartilage from either dog or human joints. (3) Hydroxylysine glycosylation was examined in the newly synthesized cartilage collagen by labelling dog joints in vivo with [3H]lysine. In experimental knees the new collagen was less glycosylated than in controls. However, no difference in glycosylation of the total collagen in the tissues was observed by chemical analysis. (4) Over half the protein-bound tritium was extracted by 4 M-guanidinium chloride from control cartilage labelled with [3H]proline, compared with one-quarter or less from experimental cartilage. Two-thirds of the extracted tritium separated in the upper fraction on density-gradient centrifugation in CsCl under associative conditions. Much of this ran with a single protein band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis under reducing conditions. The identity of this protein was unknown, although it resembled serum albumin in mobility afte disulphide-bond cleavage.

Monitoring of experimental arthritis in rabbits

The effect of ambient temperature and air flow on the radiometric measurement of experimental arthritis in rabbit knee joints has been studied. Temperature changes due to inflammation in such joints could be detected up to 70 days after induction of the arthritis by the use of radiometry. The method has been used to quantitate the anti-inflammatory activity of intra-articularly injected cortisol acetate and orally administered aspirin. It is suggested that this method of noninvasive monitoring has a number of advantages over other procedures.

Involvement of prostaglandins from rheumatoid synovium in inhibition of articular cartilage metabolism

Short term incubations of articular cartilage in media from cultures of rheumatoid synovial tissue result in marked inhibition of 3H-glycine and Na235SO4 incorporation into trichloroacetic acid (TCA) insoluble macromolecules by the cartilage segments with little effect on degradation of prelabeled cartilage matrix. This inhibition is time dependent and not observed in cartilage segments incubated in media derived from rheumatoid synovia cultured in the presence of indomethacin (a specific inhibitor of prostaglandin synthesis). In addition, no indomethacin-sensitive cartilage inhibitory activity was detectable in media from cultures of normal synovia. The ether solubility of the majority of the inhibitory activity and the indomethacin sensitivity suggest that the inhibitor(s) are prostaglandins.

The proliferation of chondrocytes and pannus in adjuvant arthritis

Cell proliferation in the pannus formation of adjuvant arthritis was studied by autoradiography. It was found that after day 9 an increased cell proliferation starts in the joint capsule recessus and synovial villi on the injected side. From these proliferating cells a pannus, which during the first phase frequently consists only of few cell layers, extends over the cartilage surface. With advancing disease the thickness of the pannus increases and further centripetal growth may cause the entire cartilage surface to be covered. This proliferating pannus tissue may invade the cartilage and destroy it. Since in this area of destruction labelled cells are frequently present, it may be assumed that proliferating cells with a high enzyme content are particularly responsible for the immediate degradation of cartilage. No involvement of chondrocytes in pannus formation was confirmed by the methods employed. There was neither increased proliferation of surface chondrocytes nor increased proliferation of chondrocytes in the depth of cartilage.

Characterization of collagen and its precursors synthesized by rabbit-articular-cartilage cells in various culture systems

Rabbit articular cartilage synthesizes type II collagen, comprised of alpha1(II) chains, in vivo or in vitro. Chondrocytes from the same tissue have the ability to produce type I chollagen with the chain composition 2alpha(I)-alpha2 or type II collagen, depending upon the culture systems in which they are maintained. Type I collagen and its precursors have been identified in the medium of monolayer cultures. Upon transfer from monolayer to suspension cultures, the cells synthesize type II collagen in the medium devoid of CaCl2 and type I collagen and its precursors in the complete medium.