IV. Joint erosion in rheumatoid arthritis

Ro 32-3555, an orally active collagenase inhibitor, prevents cartilage breakdown in vitro and in vivo

1. Ro 32-3555 (3(R)-(cyclopentylmethyl)-2(R)-[(3,4,4-trimethyl-2,5-dioxo-1- imidazolidinyl)methyl]-4-oxo-4-piperidinobutyrohydroxamic acid) is a potent, competitive inhibitor of human collagenases 1, 2 and 3 (Ki values of 3.0, 4.4 and 3.4 nM, respectively). The compound is a selective inhibitor of collagenases over the related human matrix metalloproteinases stromelysin 1, and gelatinases A and B (Ki values of 527, 154 and 59 nM, respectively). 2. Ro 32-3555 inhibited interleukin-1 alpha (IL-1 alpha)-induced cartilage collagen degradation in vitro in bovine nasal cartilage explants (IC50 = 60 nM). 3. Ro 32-3555 was well absorbed in rats when administered orally. Systemic exposure was dose related, with an oral bioavailability of 26% at a dose of 25 mg kg-1. 4. Ro 32-3555 prevented granuloma-induced degradation of bovine nasal cartilage cylinders implanted subcutaneously into rats (ED50 = 10 mg kg-1, twice daily, p.o.). 5. Ro 32-3555 dosed once daily for 14 days at 50 mg kg-1, p.o., inhibited degradation of articular cartilage in a rat monoarthritis model induced by an intra-articular injection of Propionibacterium acnes. 6. Ro 32-3555 is a potential therapy for the treatment of the chronic destruction of articulating cartilage in both rheumatoid and osteoarthritis.

Inhibition of bovine nasal cartilage degradation by selective matrix metalloproteinase inhibitors

N-terminal analysis of aggrecan fragments lost from bovine nasal cartilage cultured in the presence of recombinant human interleukin 1alpha revealed a predominant ARGSVIL sequence with an additional ADLEX sequence. Production of the ARGSVIL-containing fragments has been attributed to the action of a putative proteinase, aggrecanase. The minor sequence (ADLEX) corresponds to a new reported cleavage product; comparison of this sequence with the available partial sequence of bovine aggrecan indicates that this is the product of a cleavage occurring towards the C-terminus of the protein. Matrix metalloproteinase (MMP) inhibitors inhibited aggrecan loss from bovine nasal explants incubated in the presence of recombinant human interleukin 1alpha. A strong correlation between inhibition of aggrecan metabolism and inhibition of stromelysin 1 (MMP 3) (r=0.93) suggests a role for stromelysin or a stromelysin-like enzyme in cartilage aggrecan metabolism. However, the compounds were approx. 1/1000 as potent in inhibiting aggrecan loss from the cartilage explants as they were in inhibiting stromelysin. There was little or no correlation between inhibition of aggrecan metabolism and inhibition of gelatinase B (MMP 9) or inhibition of collagenase 1 (MMP 1). Studies with collagenase inhibitors with a range of potencies showed a correlation between inhibition of collagenase activity and inhibition of collagen degradation in the cartilage explant assay. This indicates that in interleukin 1alpha-driven bovine nasal cartilage destruction, stromelysin (or a closely related enzyme) is involved in aggrecan metabolism, whereas collagenase is principally responsible for collagen degradation.

A novel in vivo model for the study of cartilage degradation

Methods of quantifying cartilage destruction are described using a sponge/cartilage implant model in the rat. A cylinder of bovine nasal cartilage was positioned in the center of a sponge which had been pretreated with an irritant. The sponge/cartilages were then implanted subcutaneously into the backs of rats for periods of up to 16 days. The implanted sponges were rapidly surrounded by granulation tissue, maximal on day 2, and infiltrated by inflammatory cells which reached peak levels on day 9. Analysis of the cartilage shows an initial increase in wet weight and rapid loss of glycosaminoglycans. These changes were later followed by loss of cartilage wet weight and significant loss of hydroxyproline content. In a separate study, the effects of Mycobacterium tuberculosis (Mtb), kaolin, and zymosan were compared (1 mg/sponge) and the results showed that only Mtb induced pronounced inflammation and degradation of cartilage. The cartilage degradation directly correlated with the granulation tissue weight, but not with cellular infiltration. We believe that this simple, reproducible in vivo model could be used to elucidate the mechanisms involved in the destructive process and evaluate the efficacy of inhibitors of cartilage degradation.

Monoclonal antibodies against synovial collagenase: use for immunopurification and characterization of the latent and active enzyme

Monoclonal antibodies have been produced against porcine synovial collagenase which recognize both the active enzyme and its inactive precursor. These antibodies inhibited the collagenolytic activity of collagenase, but not its activity with a synthetic peptide substrate. The antibodies were also able to recognize human synovial, human skin fibroblast and human chondrocyte collagenase but not the enzyme from human granulocytes. One of the monoclonal antibodies was successfully used for the immunopurification of the porcine enzyme and these experiments led to the demonstration of an endogenous activator of procollagenase in the synovial cell culture medium.

Effect of Withania somnifera on glycosaminoglycan synthesis in carrageenin-induced air pouch granuloma

The effect of W. somnifera on glycosaminoglycan synthesis in the granulation tissue of carrageenin-induced air pouch granuloma was studied. W. somnifera was shown to exert significant inhibitory effect on incorporation of 35S into the granulation tissue. The uncoupling effect on oxidative phosphorylation (ADP/O ratio reduction) was also observed in the mitochondria of granulation tissue. Further, Mg2+ dependent ATPase activity was found to be influenced by W. somnifera. W. somnifera also reduced the succinate dehydrogenase enzyme activity in the mitochondria of granulation tissue.

Collagenase production by human mononuclear cells in culture: inhibition by gold containing compounds and other antirheumatic agents

Human peripheral blood mononuclear cells in adherent cultures have been shown to synthesise and secrete collagenase. In the present study we have examined the modulation of collagenase production in these cultures by several antirheumatic agents. Incubation of monocytes in serum free medium with sodium aurothiomalate in concentrations varying from 7.7 X 10(-7) to 7.7 X 10(-3) mol/l resulted in marked dose dependent inhibition of the collagenase production. This inhibition was apparently selective in that total protein synthesis or the viability of the cells were not affected. Similar inhibition of the collagenase production was also noted with auranofin, aurothioglucose, and chloroauric acid. The inhibition with auranofin was achieved with a concentration as low as 7.4 X 10(-8) mol/l. To examine the mechanisms of the inhibition of the collagenase activity induced by sodium aurothiomalate the production of prostaglandin E2 was also measured in the same cell cultures. Sodium aurothiomalate in concentrations greater than 7.7 X 10(-4) mol/l significantly inhibited the prostaglandin E2 production; the prostaglandin E2 production was not inhibited, however, in 7.7 X 10(-5) mol/l concentration, while the collagenase production was reduced by 51.0%. Also, exogenous prostaglandin E2 added to the cultures only slightly reversed the inhibition of the collagenase production by sodium aurothiomalate. Thus the inhibition of collagenase production by sodium aurothiomalate in human adherent mononuclear cell cultures appears to be independent of the inhibition of prostaglandin E2 production. The inhibition of collagenase produced by monocyte-macrophages, as shown here in vitro, may contribute to the clinical efficacy of the compounds tested in the treatment of rheumatoid arthritis.

Degradation of cartilage by macrophages in culture: evidence for the involvement of an enzyme which is associated with the cell surface

A cell culture system is described in which purified mononuclear phagocytes may be cultured with a cartilage substrate which is radiolabelled in its proteoglycan. Resident mouse peritoneal macrophages degraded this substrate, and did so more avidly if cultured in direct contact with it. There was no evidence for complete intralysosomal degradation of the proteoglycan of the cartilage. Lysates were found to contain considerable activity at pH 7, which was inhibited by the presence of 10% serum, or by boiling the lysate. Proximity of macrophages to the substrate did not induce selective release of the lysosomal marker enzyme hexosaminidase, and concentrated enzymes secreted from the macrophages after treatment with the lysosomotropic agent ammonium chloride were ineffective in degrading cartilage at neutral pH. The active enzyme in macrophage lysates at neutral pH was found to be sedimentable by 100,000 X g centrifugation for 1 hour, in absence of lysosomal protective agents. There is evidence for a cell membrane-associated process in the degradation of cartilage by these cells, which may be a proteolytic, endoglycosidic or free radical-mediated event.

Biochemistry and antigenicity of osteoarthritic and rheumatoid cartilage

The purpose of this study was to test whether cartilage serves as the source or repository of antigenic components active in the stimulation of inflammation in rheumatoid arthritis through an analysis of peripheral blood lymphocyte proliferation. Articular cartilage samples were obtained from patients with osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis undergoing joint replacement surgery. Each sample was homogenized and characterized biochemically with respect to the content of proteoglycan, collagen, and immunoglobulin. Proteoglycan content of rheumatoid cartilage was reduced by 71% when compared to osteoarthritic cartilage; the proteoglycan content of ankylosing spondylitis cartilage was reduced by 40% when compared to osteoarthritic cartilage. Immunoglobulins were detectable in all cartilage samples when analyzed by ELISA or end-plate titration. Lymphocyte proliferation, quantified by uptake of 3H-thymidine, was unaltered by addition of cartilage fragments, low (saline) and high salt extracts (2.0 M CaCl2), or cartilage residues. Both autologous and heterologous lymphocytes were tested against the cartilage samples with no difference in reactivity. Purified bovine articular proteoglycans and Type II collagen were also inactive. Although tetanus toxoid and phytohemagglutinin were effective stimulants of proliferation, lymphocytes from arthritis patients were suppressed relative to those of normal individuals. Analysis of arthritic articular cartilage by these techniques failed to demonstrate the presence of antigen(s) stimulating proliferation of peripheral blood lymphocytes.

Assessment of radiologic progression in rheumatoid arthritis. A randomized, controlled trial

Radiologic assessment of progressive joint destruction in rheumatoid arthritis is generally considered to be the ultimate standard for evaluation of treatment. We compared alternative radiologic techniques by performing a randomized, controlled trial in which hand films of rheumatoid arthritis patients were read by several skilled observes. The number of joints evaluated (34 versus 18) was found to make relatively little difference, but the number of readers and their experience level was critical. Films should be read in pairs. Joint space narrowing and erosion scores were shown to contribute independent information. Use of recommended techniques can reduce the number of patients required and, thus, can reduce the cost of a clinical trial by more than half and can substantially increase the sensitivity and efficiency of a trial. Therefore, critical selection of the method of assessing study endpoint is of great importance.

Ascorbic acid stimulates the resorption of canine articular cartilage induced by a factor derived from activated rabbit macrophages

Articular cartilage explants from the knees of mongrel dogs release 5-10% of their proteoglycan content spontaneously when cultured for 4 days in serum-free modified Bigger's medium. A factor synthesized and secreted by lipopolysaccharide-stimulated rabbit macrophages can stimulate this release of proteoglycan by 2 to 3-fold. The release of proteoglycan in response to macrophage factor is maximal in the presence of 1.5-50 micrograms/ml L-ascorbic acid. In the absence of ascorbate, or with high levels of ascorbate (150 micrograms/ml), the effect of the factor is diminished by 50%. D-isoascorbate, reduced glutathione, or dithiothreitol cannot substitute for L-ascorbate in producing this effect, while dehydroascorbate can.

Human mononuclear cell factors mediate cartilage matrix degradation through chondrocyte activation

Human blood mononuclear cells (BMC) in short-term culture secrete one or more factors that induce degradation of matrix proteoglycan and collagen in cartilage explants in organ culture. Induction of matrix degradation took place both in nasal septum and articular cartilage explants in the presence of the mononuclear cell supernates. Cartilage degradation in this system was absolutely dependent on the presence of live chondrocytes. Matrix depletion did not occur in dead cartilage explants cultured with active supernates. Supernates obtained from unstimulated BMC showed variable cartilage matrix degrading activity (MDA). BMC stimulated with phytohemagglutinin (PHA) showed increased MDA, which in one dilution experiment was found to be five times higher than that in the unstimulated control supernate. Concanavalin A and pokeweed mitogen were also shown to stimulate release of MDA. Time experiments showed that most of the degrading activity was released by the mononuclear cells during the first day of culture. The cellular origin of MDA was investigated with the aid of partially purified BMC subpopulations. Removal of adherent cells resulted in a decrease of MDA release. Purified T lymphocytes failed to show enhanced MDA release in spite of their ability to mount a virtually intact proliferative response to PHA. Purified adherent cells also failed to show enhanced PHA-dependent MDA release. Nevertheless, restoration of PHA-dependent MDA release took place in reconstituted cell populations containing both T lymphocytes and monocytes. These experiments suggest that MDA may be released by adherent mononuclear cells, presumably monocytes, and that the PHA-dependent increase in MDA release may be mediated by T lymphocytes. Partial characterization of MDA by gel chromatography showed one active fraction corresponding to an apparent molecular weight ranging from 12,000 to 20,000. The fraction was also shown to degrade cartilage matrix only in the presence of live chondrocytes. These results demonstrate that factors released by human BMC mediate degradation of matrix proteoglycan and collagen in intact cartilage explants through chondrocyte activation. This pathogenic mechanism may play a role in in vivo cartilage destruction in chronic inflammatory joint diseases.

Synthesis of a collagenase inhibitor by gingival fibroblasts in culture

Human collagenase was inhibited by test solutions of human gingival fibroblast culture media. The fibroblast-derived collagenase inhibitor was only slightly affected by 10 micrograms trypsin but was inactivated with 100 micrograms trypsin. The chaotropic agent KSCN (3 M) completely inactivated the inhibitor, whereas the thiol-blocking reagent, p-aminophenylmercuric acetate, partially inactivated the inhibitor. Inhibitory activity was retained at 60 degrees C but was abolished at 100 degrees C. Following ammonium sulfate fractionation, the fibroblast inhibitor was recovered in the supernatant at concentrations of at least 70% saturation. It is suggested that collagenase latency in soft connective tissues may derive from a collagenase-inhibitor complex formed by interaction of collagenase and a fibroblast-derived inhibitor.

The prostaglandins of articular cartilage. I. Correlates of prostaglandin activity in a chondrocyte culture system

Suspensions of aggregated chondrocytes display active prostaglandin (PG) production. Radioimmunoassay of culture media and thin layer chromatographic analysis suggests that PGE2 is the primary PG synthesized. In order of decreasing concentration, the following PG were tentatively identified; PGE greater than PGI greater than PGA + PGB greater than or equal to PGF1+2 greater than TxB. An inverse logarithmic relationship was identified between PG synthesis and cells cultured at densities of 1.5 to 7.5 x 10(6) cells/ml. Little or no change in the PG distribution profile was seen at these high cell densities. Maximum PG synthesis was attained after 36 hours of incubation with persistence of high synthetic levels up to 48 hours. PGE2 production measured at various post-isolation intervals indicated an initial high rate of synthesis during the first 4 hours which decreased with time up to 24 hours. Cartilage explant organ cultures demonstrated a similar level of PG synthesis suggesting minimal effect of matrix on cellular PG production. Indomethacin (5 microgram/ml) inhibited PG synthesis by 70% within 4 hours and 85% after 24 hours of exposure. Arachidonic acid supplementation (10 microM) stimulated PG synthesis by 300%.

A light and electron microscopic study of the region of cartilage resorption in the embryonic chick femur

It has long been known that uncalcified cartilage of embryonic chick long bones is removed to make way for invading marrow. However, no one has clearly established which cells are responsible for this erosion. Using the light and electron microscopes, we have studied the cartilage-marrow interface, which we presume to be the region of resorption. Here, we found two types of mononuclear cells in intimate contact with cartilage matrix. 1. The predominate cell type had a euchromatic nucleus with a nucleolus and a cytoplasm containing extensive profiles of rough endoplasmic reticulum; also, processes extended from these cells into the adjoining cartilage matrix. 2. Macrophages containing many lysosomal vesicles, which often became swollen, were found on or near the surface of cartilage. In addition, a few cells with an intermediate appearance were present. A decrease in the amount of sulfated material in a 25-30 micrometer zone of cartilage in advance of the interface and an alteration in the orientation, and in some cases the integrity, of collagenous fibers were associated with the presence of the above mentioned cells. These alterations in cartilage were not due to the synthesis of sulfated or of collagenous material. The above evidence, although not conclusive, suggests that these mononuclear cells are responsible for cartilage resorption. In this respect, the removal of avian uncalcified cartilage is similar to the resorption of uncalcified articular cartilage which occurs in rheumatoid arthritis.

Degradation of cartilage proteoglycans by a neutral proteinase secreted by rabbit bone-marrow macrophages in culture

When cultivated together with pieces of cartilage biosynthetically labelled with 35S in their proteoglycans, rabbit macrophages, differentiated in vitro from bone-marrow cells, cause the release of soluble 35S-labelled material into the culture medium. This process is inhibited by killing the macrophages or by cycloheximide treatment, and is due to the secretion by the cells of a metal-dependent neutral proteinase capable of degrading cartilage proteoglycan subunits into fragments of high molecular weight. Enzyme activity is optimum at about pH7, and is inhibited by EDTA, o-phenanthroline, cysteine or serum, but not by di-isopropyl phosphorofluoridate nor by 4-hydroxymercuribenzoate. The effect of EDTA is partially reversed by Co2+ or Zn2+ ions. The enzyme is eluted from Sephadex G-150 columns as a single peak of material (apparent mol.wt. 17000) that contains also most of the proteolytic activity exerted by culture media on Azocoll (denatured collagen) or on casein. The possible role of this metalloproteinase in chronic inflammatory processes is discussed, particularly in connection with joint erosions in rheumatoid arthritis.

Increased collagen metabolism in granulomata induced in rats deficient in endogenous prostaglandin precursors

Collagen metabolism was measured (in terms of various hydroxyproline (HP), DNA and protein ratios) in granulomata obtained after s.c. implantation of carrageenan-impregnated and untreated polyether sponges into normal and essential fatty acid deficient (EFAD) rats for 8 and 15 days. Collagen synthesis (HP/protein) in day 8 and 15 untreated granulomata was the same for both normal and EFAD rats, though collagen breakdown (total HP) appeared to be greater in EFAD granulomata on day 15. With carrageenan-impregnated sponges, collagen synthesis in EFAD granulomata was much greater than in normal granulomata on both day 8 and day 15. Ratios of protein and/or HP to DNA (probably indicative of cellular infiltration) were increased in EFAD rats with both sponge types, though this increase was less pronounced with carrageenan-impregnated sponges. It is suggested that endogenous prostaglandin (PG) production (marledly reduced during EFA deficiency) may exert a negative feedback effect on collagen metabolism during proliferative inflammation.

Collagenase at sites of cartilage erosion in the rheumatoid joint

Immunolocalization studies of rheumatoid tissues employing specific synovial collagenase antibody have demonstrated immunoreactive enzyme at the cartilage/pannus junction. Collagenase was not detected in chondrocytes or the cartilage matrix remote from the resorbing front, and relatively little enzyme was observed in the hypertrophied synovial membrane itself. These observations directly support the idea that synovial collagenase participates in cartilage erosion in rheumatoid arthritis.

Surface ultrastructure of rheumatoid articular cartilage

Six rheumatoid articular cartilage specimens, which appeared grossly normal and were shown to be free of pannus when examined under the light microscope, were examined electron microscopically. For comparison, normal-appearing cartilage specimens from 2 patients with meniscus injury and 2 with degenerative joint disease (DJD) were also examined. In all cases the normal-appearing joint surface of rheumatoid cartilage was abnormal. Amorphous-appearing material was present to a depth varying between 6 and 25 micron. Some of this material had the appearance of fibrin deposited at the cartilage surface, but much appeared to represent breakdown products of the cartilage matrix, i.e. degraded collagen and proteoglycan. DJD cartilage did not show similar changes. The findings suggest that the surface of rheumatoid articular cartilage, even when grossly normal in appearance, is degraded by enzymes either present in the synovial fluid or released by polymorphonuclear cells in close contact with the cartilage surface.

A pathogenetic model for erosive synovitis: lessons from animal arthritides

Adjuvant arthritis, streptococcal cell wall-induced arthritis, and Erysipelothrix insidiosa arthritis are laboratory models of relapsing, erosive synovitis. A review of the experimental literature suggests that their pathogenesis is similar. The persistence in macrophages in the pannus of nonbiodegradable microbial cell wall components containing the peptidoglycan moeity is the central event. Based on this experimental literature, a model for the pathogenesis of these arthritides is developed. This model is testable and relevant to erosive synovitis in man.

Type III collagen: A major constituent of rheumatoid and normal human synovial membrane

The findings establish that type III collagen is a major constituent of grossly proliferated rheumatoid and normal synovium. Unlike the collagen of normal synovium most of that in rheumatoid tissue could be solubilised by pepsin at 4 degrees C. Moore than half the pepsin-solubilised collage was identified as type III, the remainder being type I, by CM-cellulose chromatography; SDS-polyacrylamide electrophoresis with and without reduction of disulphide bonds; and amino acid analysis. Moreover, at least half the total collagen in several samples of normal as well as rheumatoid tissue was clearly type III when cyanogen bromide-derived peptides were run on SDS-polyacrylamide electrophoresis and compared with peptides prepared from purified types I and III collagens. This conclusion was supported by the isolation on phosphocellulose and quantitation by amino acid analysis of the collagen peptides alpha(1)CB2 and alpha(III)CB2 from a cyanogen bromide digest of rheumatoid synovium.