Neutral proteinases from articular chondrocytes in culture. I. A latent collagenase that degrades human cartilage type II collagen

Serum-free culture of rabbit meniscal fibrochondrocytes: proliferative response

We have formulated a serum-free medium capable of supporting DNA synthesis in rabbit meniscal fibrochondrocytes at a level equivalent to 10% fetal bovine serum (FBS). The medium consists of a 1:1 mixture of Dulbecco's Modified Eagle's Medium and Ham's F-12 medium supplemented with transferrin (1 microgram/ml), selenium (1 pg/ml), trace metal mix (1:100), dexamethasone (100 ng/ml), insulin-like growth factors I and II (50 ng/ml each), pituitary fibroblast growth factor (100 ng/ml), and lactalbumin hydrolysate (2 micrograms/ml). Endothelial cell growth supplement could be substituted for lactalbumin hydrolysate to obtain similar results. Ventrex PC-1, a commercially available, low-protein, serum-free medium, was found to support proliferation of fibrochondrocytes but not as well as 10% FBS or our medium formulation. Lipid supplements, which are known to support the serum-free growth of hyaline chondrocytes, were found to be either of no value or antagonistic for the culture of fibrochondrocytes. Likewise, vitamin E alone, progesterone, putrescine, and hydrocortisone were also without benefit in our culture system. The cells had a more chondrocytic morphology when grown in defined medium as opposed to 10% FBS. The results of this study should now make it possible to identify and quantitate those factors necessary to affect meniscal repair by utilizing further techniques in vitro.

Damage of cultured chondrocytes by hydrogen peroxide derived from polymorphonuclear leukocytes: a possible mechanism of cartilage degradation

To study the mechanisms of chondrocyte damage, chondrocyte cytotoxicity as shown by chromium-51 release induced by polymorphonuclear leukocytes (PMNLs) was examined. PMNLs significantly enhanced chondrocyte cytotoxicity in the presence of phorbol dibutyrate. This chondrocyte damage was abolished by the addition of catalase, whereas superoxide dismutase and scavengers of hydroxyl radicals and protease inhibitors failed to reverse it. When cartilage matrix components such as hyaluronic acid and various proteoglycans were added to the PMNL-chondrocyte cultures, these components failed to affect the chromium-51 release. These results suggest that the increase in chondrocyte cytotoxicity is due to hydrogen peroxide generated by the PMNLs, and that cartilage matrix components do not prevent it. Hydrogen peroxide from PMNLs may therefore play an important role in cartilage degradation through direct damage of chondrocytes during inflammatory process.

Inverse correlation between tyrosine phosphorylation and collagenase production in chondrocytes

Collagenase production by chondrocytes appears to play a major role in the development of osteoarthritis. Although the mechanisms regulating collagenase production by chondrocytes are not known, incubation of bovine chondrocytes in serum markedly decreases collagenase production. Since serum has been demonstrated to increase levels of phosphotyrosine (P-Tyr) in several cell types, we determined the effect of altering intracellular levels of P-Tyr on collagenase production. Both orthovanadate, a potent inhibitor of tyrosine phosphatases, and serum caused a marked increase in tyrosine phosphorylation. The increase in P-Tyr was associated with a decrease in the production of collagenase, suggesting that two processes may be linked. Orthovanadate caused an increase in P-Tyr in the absence of serum, suggesting that P-Tyr levels in resting chondrocytes are regulated through activity of both tyrosine kinases and phosphatases. Orthovanadate and serum induced a synergistic increase in P-Tyr levels, suggesting that serum functions through increasing kinase activity rather than decreasing phosphatase activity. In the absence of serum, concentrations of orthovanadate which maximally inhibited collagenase production primarily increased phosphorylation of a 36 kDa protein, suggesting that the phosphorylation of this protein may play a major role in regulating collagenase production. Orthovanadate had limited effects on chondrocyte proteoglycan synthesis, morphology or viability in the presence or absence of serum, suggesting that the decrease in collagenase production was not due to non-specific inhibition of protein synthesis or cellular toxicity. Inhibition of tyrosine phosphatases by orthovanadate or activation of tyrosine kinases by addition of serum correlated with the inhibition of collagenase production.

Fetal bovine serum inhibits chondrocyte collagenase production: interleukin 1 reverses this effect

Bovine articular chondrocytes incubated in medium which was serum free or contained low levels of fetal bovine serum (less than 5%) constitutively produced collagenase. Increasing the concentration of serum in the culture medium inhibited the production of collagenase. Addition of interleukin 1 and lipopolysaccharide reversed the inhibitory effect of serum. Phorbol esters only stimulated collagenase production when the serum concentration was at least 10%. These data suggest that there is a factor(s) in fetal bovine serum that inhibits collagenase production by chondrocytes and this can be reversed by agents such as interleukin 1.

Production of collagens, collagenase and collagenase inhibitor during the dedifferentiation of articular chondrocytes by serial subcultures

Rabbit articular chondrocytes were cultured in monolayer and the progressive loss of their differentiated phenotype was monitored from passage to passage. The cell densities achieved in confluent cultures decreased abruptly between the primoculture and the second or third subculture, and more slowly thereafter, reflecting parallel morphological changes. The synthesis of collagen (but not that of other proteins) decreased sharply, and a smaller proportion of collagen was incorporated into the matrix. Cells in primoculture synthesized mainly the cartilage-specific collagens, types II and XI, which were mostly deposited in the matrix, but no type I nor III collagen. With increasing passages, the synthesis of type II collagen decreased progressively while that of types I and III collagens increased, the latter being almost completely released in the culture medium. Simultaneously, the production of type XI collagen was apparently switched to that of type V. Fully differentiated confluent chondrocytes in primoculture produced the collagenase inhibitor TIMP (tissue inhibitor of metalloproteinases) but no detectable procollagenase; their production of procollagenase was, however, induced by interleukin 1. The production of TIMP increased from passage to passage. A spontaneous production of procollagenase was only occasionally observed in confluent cultures of dedifferentiated chondrocytes. However, interleukin 1 induced an always higher production of procollagenase from dedifferentiated chondrocytes than from cells in primoculture.

A high molecular weight collagenase inhibitor made by rabbit chondrocytes in cell culture

A new, high molecular weight (66,000 daltons) inhibitor of collagenase (LCI) has been isolated and partially characterized. It accounted for 20% of the collagenase-inhibitory activity in the supernatants of rabbit chondrocytes cultured in 10% acid-treated fetal bovine serum (ATFBS). LCI was stable to 60 degrees C and sensitive to reduction and alkylation. Unlike a low molecular weight collagenase inhibitor, similar to Tissue Inhibitor of Metallo-Proteinases (TIMP), it did not bind to concanavalin A-Sepharose 4B.

Intact proteoglycan is a polyclonal activator of murine B-lymphocytes

Destruction of articular cartilage is the hallmark of both inflammatory and degenerative arthritides. Since degradation of cartilage results in the release of proteoglycan (PG) monomers and fragments into the synovial fluid, the present study was initiated to determine whether hyaline cartilage PG can induce a cellular immune response. Nonimmune spleen cells obtained from A/St and C57Bl/6 mice were cultured with a crude extract of bovine nasal cartilage, a PG aggregate fraction, PG monomer or degraded PG monomer for varying time periods. Only intact PG monomer induced a proliferative response which peaked at day 2. The responding cell was a B-lymphocyte which did not require T-helper cell activity. Our results suggest that intact PG monomer is a polyclonal activator of B-lymphocytes.

Interleukin-1 stimulates the secretion of proteoglycan- and collagen-degrading proteases by rabbit articular chondrocytes

Supernatants from the P388D1 murine macrophage cell line as well as commercially prepared human interleukin-1 (IL-1) stimulated primary rabbit articular chondrocytes to produce collagen- and proteoglycan-degrading proteases. The P388D1-derived factor had a molecular weight of 16,000-20,000 and a pI of 4.5-5.0, and was sensitive to phenylglyoxal treatment. Human IL-1 and the P388D1 supernatants enhanced glycosaminoglycan (GAG) release from bovine nasal cartilage explants. The proteoglycan- and collagen-degrading proteases required Ca2+ for activity. Latent proteoglycanase and collagenase had molecular weights of 44,000-56,500 and 34,000-44,000, respectively. The activated proteases had molecular weights of 30,000-40,000 and 22,000-36,000, respectively. Heparin-Sepharose affinity chromatography yielded two latent proteoglycanase-degrading protease activities and a collagen-degrading peak. The two proteoglycanase peaks also degraded fibronectin, laminin, gelatin, and azocoll but not type I collagen. The collagenase peak also degraded proteoglycan, gelatin, fibronectin, laminin, and azocoll. The activity of the proteoglycan- and collagen-degrading peaks was inhibited by phenanthroline and alpha 2-macroglobulin but not by phenylmethylsulfonylfluoride (PMSF), tosyllysylchloromethylketone (TLCK), pepstatin, or alpha 1-antitrypsin. The control of factors which augment protease production may offer a novel therapeutic approach to arthritis.

Pathogenesis of osteoarthritis

This article reviews the etiology and pathogenesis of osteoarthritis, particularly one of several current concepts concerning the possible central mechanisms regulating degradation of cartilage. According to this theory, degradation involves diffuse or focal exposure of the extracellular matrix to active neutral metalloproteinases, which then results in injury as well as initiation of repair processes. Diffuse matrix exposure is probably not a physiologic aberrancy but rather a pathologic result of either physical injury to local chondrocytes or inflammatory mediators.

Degradation of bovine articular cartilage proteoglycans in vitro. The effect of Bacteroides gingivalis

The black-pigmented Bacteroides gingivalis has previously been isolated from periodontal pockets and been shown capable of inflicting advanced tissue damage. Its effect on the degradation of articular cartilage proteoglycans has not previously been known. In these experiments it was demonstrated that under aerobic conditions the anaerobic microbe B. gingivalis is very potent in degrading the proteoglycans of fresh articular cartilage. It is even more potent in the presence of fetal calf serum (FCS) than in its absence. When the cartilage has been frozen/thawed there is still a slight enhancement of the degradation by B. gingivalis, but when the cartilage has been devitalized and de-enzymed by heat, the cartilage-degrading capacity of B. gingivalis is totally abolished. However, addition to the cartilage cultures of filtered conditioned medium from B. gingivalis inhibits in some degree the degradation of articular cartilage proteoglycans. It is therefore suggested that the great cartilage-degrading ability of Bacteroides gingivalis shown in this culture system could be due to its ability to degrade proteinase inhibitors.

Increased collagenase activity in human rheumatoid meniscus

Collagenase activity of the knee joint menisci of patients suffering from rheumatoid arthritis was approximately 3-fold higher than that found in menisci of control patients. The mean collagenase activity in the macroscopically more diseased parts of the rheumatoid menisci was significantly higher than that in the less damaged areas. The specific degradation products resulting from the cleavage of human meniscoid type II collagen by rheumatoid meniscoid collagenase were demonstrated by SDS-polyacrylamide gel electrophoresis. Addition of N-ethylmaleimide, which activates latent mammalian collagenases, did not further increase collagenase activity in rheumatoid menisci. Thus in rheumatoid meniscus, collagenase may be synthesized and then activated, probably by proteolytic enzymes involved in the inflammatory reaction.

Human rheumatoid arthritic cartilage and its neutral proteoglycan-degrading proteases. The effects of antirheumatic drugs

Measurements were made of the neutral proteoglycan-digesting protease activity in the cartilage matrix breakdown observed in the rheumatoid arthritic process. Normal knee (tibial plateau) cartilage specimens were obtained from 7 fresh cadavers and 29 cartilage specimens were obtained from 23 patients diagnosed as having rheumatoid arthritis (RA). The total neutral metalloproteoglycan-degrading enzyme (NMPE) activity in RA cartilages exhibited roughly an eightfold elevation over that of control subjects. The active form of the NMPE for diseased cartilage was higher than that observed for normal cartilage, but was not statistically different. A very low level of activity was detected for serine proteases and no variation was observed between normal and diseased cartilages. Data obtained from RA cartilages were also analyzed with respect to the relationship between enzyme activities and the patients' medications. Four groups of patients were then selected according to their drug treatments: S + G patients received steroid and gold therapy; S patients received steroids only; NS + NG patients did not receive steroid or gold therapy; G patients received gold therapy alone. The total NMPE activity for each of these groups remained at a very high level. The active enzyme activity measured in S + G and S patients was decreased to a level not different from that of normal controls. Specimens from NS + NG patients presented a significantly higher level of the active form of the enzyme (P less than 0.05) when compared with either normal controls, S + G, or S patients. No significant difference was noted in the level of serine protease activity between the RA cartilage and normal cartilage.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonsteroidal anti-inflammatory drugs and modulation of cartilaginous changes in osteoarthritis and rheumatoid arthritis. Clinical implications

Nonsteroidal anti-inflammatory drugs have a potential for modifying the complex pathophysiologic events leading to cartilage destruction in various forms of arthritis. Following an evaluation of basic mechanisms in the pathogenesis of cartilaginous destructive lesions, the effects of nonsteroidal anti-inflammatory drugs on normal chondrocyte metabolism are discussed. Their capacity to modulate cartilage and bone lesions in experimental forms of arthritis is addressed, as is the manner in which they may modify the pathophysiology of cartilage destruction in human forms of arthritis. Different classes of nonsteroidal anti-inflammatory drugs produce different effects in certain in vivo or in vitro settings.

Cytokine modulation of chondrocyte proteinase release

Nonenzymatic, trypsin sensitive cytokines derived from lectin stimulated normal human mononuclear cells have been shown to induce release of proteoglycan and collagen degrading proteinase activity from chondrocytes in cartilage organ and isolated suspension culture systems. Active chondrocyte protein and RNA synthesis were required to induce activity. Cytokines responsible were of both monocyte and T cell origin. Direct monokine catabolic induction and monokine/lectin-triggered lymphokine inducing activity could be demonstrated. Cyclooxygenase inhibitors and direct or indirect modulation of mononuclear cell or chondrocyte cAMP levels had no effect on factor synthesis or activity. Hydrocortisone abrogated the effect. Cytokines responsible were heat labile, unaffected by reduction/alkylation or neuraminidase exposure, and stable over a pH range of 3-10.

Characterization of latent and active forms of cartilage proteinases produced by normal immature rabbit articular cartilage in tissue culture

Cultured tissue slices from normal immature rabbit articular cartilage released latent neutral metalloproteinases into serum-free medium. On activation with 4-aminophenylmercuric acetate, these metalloproteinases could degrade collagen, proteoglycan, and gelatin. Also produced were an acid proteinase with the properties of cathepsin D and an inhibitor of the neutral metalloproteinases. The appearance of both the proteinases and the inhibitor in the culture medium could be prevented by incubation of cultures with cycloheximide. The active and latent forms of the proteinases were characterized using Ultrogel AcA 54 chromatography.

'Gelatinase-like' activity from articular chondrocytes in monolayer culture

In addition to releasing collagenase and proteoglycanase activity, rabbit articular chondrocytes in monolayer culture released into the culture medium, latent, neutral enzyme activity which when activated by p-aminophenylmercuric acetate degraded fluorescein-labeled polymeric rat tail tendon Type I collagen and the tropocollagen TCA and TCB fragments of human Type II collagen into smaller peptides at 37 degrees C. Enzyme activity was abolished if p-aminophenylmercuric acetate-activated culture medium was preincubated with 1.10-phenanthroline, a metal chelator. Thus, articular chondrocytes in monolayer culture are capable of producing neutral proteinases which acting together can result in complete degradation of tendon and cartilage collagen to small peptides.

Correlation of the biosynthesis of prostaglandin and cyclic AMP in monolayer cultures of rabbit articular chondrocytes

We have utilized ionophores to test whether stimulation of chondrocyte prostaglandin biosynthesis is accompanied by an increase in cyclic nucleotide levels in these cells. Radioimmunoassay of prostaglandin E2, 6-oxo-prostaglandin F1 alpha (the stable metabolite of prostaglandin I2) and prostaglandin F2 alpha showed that synthesis of each was stimulated by the divalent-cation ionophore, A23187 after short-term incubation (1-7 min) in serum-free medium. No stimulation of thromboxane B2 was detected. Two monovalent ionophores, lasalocid and monensin failed to stimulate prostaglandin biosynthesis after short-term incubation. Ionophore A23187-stimulated prostaglandin biosynthesis was variably and partially inhibited by sodium meclofenamate, indomethacin and aspirin, but not by sodium salicylate. Ionophore A23187-stimulated prostaglandin biosynthesis was accompanied by a 7.5-fold increase in cyclic AMP levels after 15 min. Sodium meclofenamate, indomethacin and aspirin which inhibited prostaglandin E2 biosynthesis also reduced cyclic AMP levels. Exogenous prostaglandin E2 (1 microgram/ml) stimulated cyclic AMP biosynthesis, which was not inhibited by aspirin. These results indicated that prostaglandins can be considered as one of the local effectors controlling cyclic AMP production in articular cartilage.

Neutral proteinases from articular chondrocytes in culture. 2. Metal-dependent latent neutral proteoglycanase, and inhibitory activity

Monolayer and spinner cultured rabbit articular chondrocytes released into the medium latent metal-dependent enzyme with activity against bovine proteoglycan. Pretreatment of medium with p-aminophenylmercuric acetate or trypsin followed by soybean trypsin inhibitor significantly increased enzyme activity. The monolayer-cultured chondrocytes released more of this activity than spinner cultures. The neutral proteoglycanase activity increased with medium concentration and incubation time. Like the human cartilage proteoglycanase, its pH optimum on proteoglycan subunit was 7.25. Gel filtration on BioGel P-30 indicated that the proteoglycanase occurred in two molecular weight forms: 20 000--30 000 and 13 000. The latent enzyme was about 30 000--40 000. The metal-chelators, o-phenanthroline (5 mM) and EDTA (10 mM) inhibited the activated proteoglycanase almost completely, but trypsin and chymotrypsin inhibitors had little effect. The cultured chondrocytes also released into the media a heat-labile inhibitor against the proteoglycanase. The inhibitory activity was present in the nonactivated media and eluted on Sephadex G-100 chiefly at a position corresponding to molecular weights of 10 000--13 000.