Collagenase production by rheumatoid synovial cells: stimulation by a human lymphocyte factor

Interleukin 1: the first interleukin

The name 'interleukin' and the designation of interleukin 1 (IL-1) derived from the Second International Lymphokine Workshop held in Switzerland in 1979. Since then interest in the original interleukin (IL-1) has increased exponentially as measured by the numbers of publications and meetings. The main reasons for this can be seen in the accompanying centrefold. The perception of IL-1 as a biological mediator in every organ system has attracted scientists from widely different backgrounds into this area and a steady succession of important and often surprising insights into IL-1 biology has ensured that interest has been sustained at a high level. This overview of the biology of IL-1 on the tenth anniversary of its turbulent life has been compiled by Franco di Giovine and Gordon Duff. It is of necessity selective and biased towards human IL-1 and begins with some general points (mainly cautionary) as a backdrop to the centrefold.

Crystallization and preliminary X-ray analysis of porcine synovial collagenase

Crystals of porcine synovial collagenase suitable for an X-ray structure analysis have been obtained. The crystals belong to space group I4, with unit cell dimensions a = b = 160.0 A, c = 53.1 A, with one molecule in the asymmetric unit. Diffraction extends beyond 3 A perpendicular to the c axis but along the 4-fold axis, the intensities are measurable only to 4 A.

Clonal interactions in fibroblast proliferation: recognition of self vs. non-self

The proliferation and aging of fibroblast populations has been postulated to include a process of clonal selection. Using carbocyanine dyes to label clonal fibroblast populations, we were able to follow their growth in mixed cultures. Individual fibroblast clones seeded as the minority population (20%) with either another clone or the parent line (differentially labeled) always demonstrated increase relative growth so that, by the end of 4 weeks, approximately equal numbers of both populations were present. Labeled cells of the same clone mixed as the minority population with differentially labeled cells of the same clone maintained their minority status. The results indicate that clonal populations of fibroblasts are able to recognize "self" as different from "non-self" and that this recognition leads to alterations in cellular proliferation.

Cytokine-mediated proteolysis in tissue remodelling

Proteolytic enzymes play a key role in a variety of physiological processes in which the degradation of macromolecules is essential: angiogenesis, embryogenesis, bone and tissue remodelling, blood hemostasis and cell migration. The action of these enzymes is also crucial in the development of many pathological conditions such as wound healing, neoplasia, inflammation and arthritic disorders. The activity of proteases is negatively affected by specific protease-inhibitors. Various growth factors and other cytokines modulate the synthesis and secretion of both proteases and protease-inhibitors. The study of this regulation results in a better insight into (patho)physiology at the molecular level and promises to result in alternative treatment strategies.

Cellular interactions determining the production of collagenase by a rat mammary carcinoma cell line

The cellular interactions regulating the production of collagenase by a cell line derived from a spontaneously arising rat mammary carcinoma have been studied. The cell line, BC1, was grown permanently under defined serum-free conditions, so that the poorly characterized and variable effects of serum on collagenase expression were avoided. Two stable subpopulations of cells present in BC1 cultures were defined as epithelioid cells ("E-cells") and myoepithelioid cells ("M-cells"). These subpopulations differed in their morphology, pattern of growth and susceptibility to detachment from culture vessels by trypsin. Seven clones of M-cells and 7 clones of E-cells, obtained by the limiting dilution technique, were used to determine the cellular source of collagenase and the interactions which led to its expression. M-cells displayed an absolute dependence on a soluble factor produced by E-cells for their survival in vitro. The presence of both cellular types in culture was necessary for collagenase secretion to occur, E-cells being the major source of enzyme in mixed cultures. A soluble factor produced by M-cells was largely, if not completely, responsible for the induction of collagenase secretion by E-cells. Clones representative of both subpopulations were tumorigenic in syngeneic host animals. These results suggest that the phenotypic diversity which occurs within populations of neoplastic cells may give rise to subpopulations of cells which display a more aggressive phenotype in coexistence than in isolation.

Stimulation of the hyaluronic acid levels of human synovial fibroblasts by recombinant human tumor necrosis factor alpha, tumor necrosis factor beta (lymphotoxin), interleukin-1 alpha, and interleukin-1 beta

Monocyte/macrophage polypeptides (monokines) alter the properties of synovial cells. This interaction could explain some of the properties of the inflamed synovium in rheumatic disease. Only recently has it been possible to test the action of purified monokines on the target synovial cells. We report here that recombinant human tumor necrosis factor alpha, tumor necrosis factor beta (lymphotoxin), interleukin-1 alpha, and interleukin-1 beta stimulate the hyaluronic acid (HA) levels of human synovial fibroblast-like cells. The effect of monokines was generally inhibited by indomethacin, suggesting the involvement of an endogenous cyclooxygenase product in the stimulation, and by the glucocorticoid, dexamethasone. In contrast, all-trans-retinoic acid stimulated synovial cell plasminogen activator activity but did not increase the HA levels. These findings could help to explain the raised HA levels found in the joint fluids and in the circulation of patients with rheumatic disease.

The effect of calcium channel blockers and calmodulin inhibitors on the macrophage factor-stimulated synthesis of collagenase by rabbit chondrocytes

Macrophages and monocytes secrete a factor(s) which can stimulate the synthesis of collagenase in synovial cells and in chondrocytes. Incubation of rabbit chondrocytes with macrophage conditioned medium (MCM) and with the calcium channel blockers, nifedipine, verapamil or diltiazem (up to 200 microM) had no effect on collagenase synthesis. However, TMB-8 (8-[N,N-diethylamino]-octyl 3,4,5-trimethoxybenzoate hydrochloride), an inhibitor of internal calcium movement, did inhibit the process with an IC50 of approximately 130 microM. The calmodulin antagonists, trifluoperazine, chlorpromazine and calmidazolium (R-24571) were effective inhibitors of the process with IC50's of 40 microM, 18 microM and 3.5 microM, respectively. Collagenase activity itself was not affected by these agents. The data suggests that calmodulin and/or internal calcium movement may play a role in the macrophage factor-stimulated synthesis of collagenase in rabbit chondrocytes.

Response of epidermolysis bullosa fibroblasts to factors derived from macrophages and polymorphonuclear leukocytes in terms of collagenase production

In order to investigate the role of inflammatory cells in altering the collagenase production by epidermolysis bullosa (EB) fibroblasts, macrophage and polymorphonuclear leukocyte (PMN) factors obtained from mouse peritoneal fluids were added to the fibroblast culture system, and collagenase activity was assayed after a 48-h incubation. Data obtained here revealed that the response of collagenase production by fibroblasts was quite different, depending on the type of EB. Namely, EB dystrophica recessiva (EBDR) (n = 2) fibroblasts produced significant amounts of collagenase in the range of 5.07 (U/ml) to 6.04 in response to macrophage-conditioned medium, macrophage lysate, and PMN lysate, compared with 0.13 in the absence of these. On the other hand, EB dystrophica dominans (EBDD) (n = 1) fibroblasts showed little or no overt increase in enzyme production in the presence of macrophage lysate and PMN lysate, which resulted in a moderate increase to 3.82 in response to macrophage-conditioned medium. Furthermore, EB simplex (EBS) (n = 1) fibroblasts produced collagenase up to 3.84 in response to these three factors. These factors can be inactivated by treating with trypsin, pronase, and phenylglyoxal. Our data clearly indicated that, in the comparisons of EBDD and EBS fibroblasts, EBDR fibroblasts showed quite high response to factors derived from macrophages and PMNs in terms of collagenase production. This fact may raise a clue that accounts for the high levels of tissue collagenase activity, which plays a potentially major role in blister formation in EBDR.

Interleukin 1 modulates collagen accumulation by rat granulation tissue cells both in vivo and in vitro

In in vivo studies 0.5 U human interleukin 1 (IL-1) was inoculated daily into a subcutaneously implanted viscose cellulose sponge. IL-1 significantly decreased the dry weight (7.8%) and the hydroxyproline content (24.2%) of granulomas. When the cultured rat granulation tissue cells were exposed to IL-1 (0.5-2.0 U/ml) their collagen production decreased to 80% of that in controls. No effect on cell proliferation was detected.

The effect of interleukin 1 beta on proteoglycans synthesized by human gingival fibroblasts in vitro

The effect of recombinant interleukin-1 beta (IL-1 beta) on proteoglycan synthesis by human gingival fibroblasts was investigated. IL-1 beta stimulated the gingival fibroblasts to proliferate. When compared to human foreskin fibroblasts, the gingival fibroblasts demonstrated a greater proliferative response at higher concentrations of IL-1 beta. The midpoint of the proliferation response for both cell types was in the 10(-11) M IL-1 beta range. The rate of [35S]-sulfate incorporation into proteoglycans by human gingival fibroblasts was enhanced by 40% at 10(-9) M IL-1 beta. This stimulatory effect appeared to be independent of cell proliferation and prostaglandin synthesis since blocking of these functions with hydroxyurea and indomethacin respectively, resulted in similar dose responses to IL-1 beta. Pulse chase experiments indicated the kinetics of degradation in the presence or absence of IL-1 beta were essentially identical. Therefore, the turnover rate of proteoglycans was not altered by IL-1 beta, no significant differences between molecular species, size or glycosaminoglycan composition of the proteoglycans synthesized in the presence or absence of IL-1 beta was noted. Thus, IL-1 beta can modulate extracellular matrix synthesis by human gingival fibroblasts and may therefore be partially responsible for the early events of healing following inflammatory episodes.

Plasminogen activators and tiaprofenic acid in inflammation. A preliminary study

Treatment with tiaprofenic acid appreciably reduced the level of plasminogen activators in the medium of 3T3-Balb mouse fibroblasts, as revealed by both a fibrin plate assay and amidolytic determination with chromogenic substrates. At the same time, tiaprofenic acid was able to inhibit the production of plasminogen activators induced by phorbol myristate acetate, a powerful inflammation and tumour promoter, added to the cell monolayers. By isolating the inhibitors of plasminogen activators it was possible to show that the decrease of fibrinolytic activity produced by tiaprofenic acid is not related to an increase of inhibitors. Rather, a decrease of activators seems to take place. Synovial fluid samples from 4 patients before and after treatment with tiaprofenic acid were also assayed for plasminogen activator activity by the fibrin lysis method. In 3 of the 4 cases a marked decrease after treatment was evident. The one unresponsive patient suffered from a para-neoplastic arthritis.

Degradative pathways in cultured synovial fibroblasts: selective effects of pulsed electromagnetic fields

A cell culture model for studying the cytokine-mediated degradation of connective tissue was exposed to clinically applied, low-frequency pulsed electromagnetic fields (PEMF), and levels of collagenolytic activity, two lysosomal hydrolases, and prostaglandin E2 were measured. PEMFs reduced the release of two lysosomal enzymes by cultured rabbit synovial fibroblasts but did not affect their response to mononuclear-cell-conditioned medium. PEMF did not alter levels of cytokine activity produced by a mixed mononuclear cell population, nor did they affect the cytokine-mediated release of collagenase or prostaglandin E2 by synovial fibroblasts. The relevance of these findings to the clinical application of PEMF to soft- and hard-tissue injuries is discussed.

A review of the histopathological evidence on the pathogenesis of cartilage destruction in rheumatoid arthritis

These are three ways of cartilage destruction as summarized in Fig. 1. The relative significance of the contribution among them to the pathogenesis of cartilage destruction varies individually. It appears important here to note that chondrocytes themselves are not actively involved in the pannus formation. Chondrocytes only provide a basis for extension of the pannus by proteolytic digestion of cartilage matrix. It is however possible in some individuals that the digestion of cartilage by chondrocytes plays the predominant role in their cartilage destruction. Besides the autonomous proliferative potential of pannus tissue, it seems evident that active synovitis is the main cause of cartilage loss. This is quite important from the therapeutic view point, because we can expect to halt the disease process causing joint deformities by controlling the active synovitis.

Interleukin-1 beta and interleukin-1 alpha stimulate the N-acetyl-beta-glucosaminidase activity of human synovial cells

The properties of synovial cells are altered in vitro by monocyte-macrophage polypeptides (monokines), and these changes could explain some of the properties of the inflamed synovium in rheumatoid disease. Purified monokines have become available only recently for testing on the target synovial cells. We report here that purified human interleukin (IL)-1 beta and recombinant human IL-1 alpha stimulate the extracellular activity of the lysosomal hydrolase, N-acetyl-beta-glucosaminidase (NAG), of human synovial fibroblast-like cells. In contrast, another monokine, synovial activator, does not increase the NAG activity. Thus NAG is another cellular activity which can be modulated by interleukin-1.

Human skin fibroblast stromelysin: structure, glycosylation, substrate specificity, and differential expression in normal and tumorigenic cells

We have purified and determined the complete primary structure of human stromelysin, a secreted metalloprotease with a wide range of substrate specificities. Human stromelysin is synthesized in a preproenzyme form with a calculated size of 53,977 Da and a 17-amino acid long signal peptide. Prostromelysin is secreted in two forms, with apparent molecular masses on NaDodSO4/PAGE of 60 and 57 kDa. The minor 60-kDa polypeptide is a glycosylated form of the major 57-kDa protein containing N-linked complex oligosaccharides. Zymogen activation by trypsin results in the removal of 84 amino acids from the amino terminus of the enzyme generating a 45-kDa active enzyme species. Human stromelysin is capable of degrading proteoglycan, fibronectin, laminin, and type IV collagen but not interstitial type I collagen. The enzyme is not capable of activating purified human fibroblast procollagenase. Analysis of its primary structure shows that stromelysin is in all likelihood the human analog of rat transin, which is an oncogene transformation-induced protease. The pattern of enzyme expression in normal and tumorigenic cells revealed that human skin fibroblasts in vitro secrete stromelysin constitutively (1-2 micrograms per 10(6) cells per 24 hr). Human fetal lung fibroblasts transformed with simian virus 40, human bronchial epithelial cells transformed with the ras oncogene, fibrosarcoma cells (HT-1080), and a melanoma cell strain (A 2058), do not express this protease nor can the enzyme be induced in these cells by treatment with phorbol 12-myristate 13-acetate. Our data indicate that the expression and the possible involvement of secreted metalloproteases in tumorigenesis result from a specific interaction between the transforming factor and the target cell, which may vary in different species.

Histopathology of arthritis induced in rats by active immunization to mycobacterial antigens or by systemic transfer of T lymphocyte lines. A light and electron microscopic study of the articular surface using cationized ferritin

We analyzed the histopathologic findings of arthritis in 3 rat models: adjuvant arthritis induced by active immunization to Mycobacterium tuberculosis (MT) antigens, arthritis produced by passive transfer of an intrinsically arthritogenic line of anti-MT T lymphocytes, and bystander arthritis produced by intraarticular injection of a foreign antigen, ovalbumin, into rats with T lymphocyte line cells specific for the ovalbumin antigen. The histopathology of the tibiotarsal and knee joints was studied by light microscopy and the articular surface of the cartilage by electron microscopy after labeling with cationized ferritin. The lesions in the 3 models of arthritis were compared. In active adjuvant arthritis, inflammatory lesions and cartilage destruction were found as early as 9 days after immunization, and persisted for as long as 11 months. Similar, but somewhat milder, lesions were found in arthritis produced by transfer of anti-MT T lymphocytes. Inflammatory signs were present at 4 days, when there was no evidence of joint edema. Severe inflammatory lesions were found in arthritis induced by transfer of anti-ovalbumin T lymphocytes that was followed by ovalbumin injection into the knee. Pathologic changes were found to be similar in all 3 models. Thus, the changes could be attributed to the action of T lymphocytes, irrespective of whether the target antigen was intrinsic to the joint.

Comparative studies of adherent rheumatoid synovial cells in primary culture: characterisation of the dendritic (stellate) cell

Primary cultures of adherent rheumatoid synovial cells contain variable proportions of fibroblasts, macrophages, and dendritic cells, as judged by morphological appearance. Comparative studies using various enzymic and histochemical staining procedures showed the dendritic cells to lack many of the characteristic features of macrophages, e.g. the failure to express HLA-DR (Ia) antigen. The dendritic cells and fibroblasts had several similarities, but differed to some extent in their nonspecific esterase activity, phagocytic and proliferative potential. As the proportions of dendritic cells and fibroblasts varied in relation to specific culture conditions, we examined the possibility that these morphologies might represent different functional states rather than distinct cellular origins. Using subcultured synovial fibroblasts with a uniform bipolar appearance, we have shown that exposure to interleukin-1 or mast cell products resulted in a transformation to dendritic morphology. This change in cell shape was prevented by the presence of indomethacin, but was subsequently achieved by the addition of exogenous PGE2. Thus it appears that the latter is the factor that modulates the morphological change of fibroblastic to dendritic cells. This study has also demonstrated the complete and reversible interchange of fibroblast/dendritic morphology, thereby confirming that these different shapes are manifest by the same cell. The changes in phenotypic expression associated with the dendritic appearance include increased production of collagenase, prostaglandin E, and nonspecific esterase, as well as an apparent inability to exhibit phagocytosis and to proliferate in culture. We conclude from our in vitro studies that the phenotypic behaviour of the synovial fibroblast (or synoviocyte) is very variable and dependent to a large extent upon local stimuli, but the identity and hierarchy of such stimulating and suppressive factors in relation to cellular interactions requires further study.

Biochemical analysis of synoviocytes from normal and arthritic rats. Evidence for an activated state associated with adjuvant polyarthritis

Adjuvant-induced polyarthritis in rats is a common model system used for the study of the synovitis that occurs in rheumatoid arthritis. Synoviocytes A, the major cell type covering the internal surface of the joint, could be involved in the pathogenesis of rheumatoid arthritis because of their increased proliferation and the intraarticular manifestations of the disease. So far only a few molecular studies have been reported on synoviocytes upon arthritis induction. We report here changes in polypeptides, between control and arthritic synoviocytes, by using two different radiolabeling methods and two-dimensional gel electrophoresis analysis. Major differences were found using metabolic labeling on regions of tropomyosins, cyclin, tubulins and vimentin. In addition, external surface labeling of the cells with lactoperoxidase showed clear differences between control and arthritic synoviocytes in the region of 77-100-kDa proteins. Some of these differences can be reproduced by certain macrophage activators such as phorbol myristate acetate and lipopolysaccharide acting on synoviocytes in vitro and in vivo respectively. These results exclude the possibility that the changes observed were due to a possible infiltration of other cell types in the arthritic synovia and strongly support the existence of an activated state of synoviocytes associated with arthritis induction.

"Matrigenin" activity from bovine bone--II. Effects on the glycosaminoglycans of bovine articular cartilage in culture

1. Bovine articular cartilage slices were studied in long term culture by periodically pulse-labelling the cultures with radiolabelled precursors of glycosaminoglycans and isolating the glycosaminoglycans from cartilage. 2. Pretreatment of the cartilage slices with bacterial collagenase resulted in stimulation of the incorporation of radioactivity into the glycosaminoglycans. 3. The addition of a fraction from bovine bone, enriched in "matrigenin" activity, to cultures of cartilage pretreated with collagenase resulted in an additional increase in the stimulation of incorporation of radioactivity.

Immunoregulatory mediators in the pathogenesis of rheumatoid arthritis

There is strong evidence for the participation of T cells, B cells and monocytes-macrophages in the local constitution of RA lesions. Such cells may create synovial damage either directly or indirectly through the secretion of mediators able to amplify immune responses and damage neighboring cells. Interleukin 1 (IL 1) can be found in RA lesions together with inhibitors of its action. Tumor necrosis factor (TNF) is another monokine able alone and in conjunction with IL 1 to stimulate bone resorption and inhibit proteoglycan synthesis. Interferon (IFN) is able to enhance the synthesis of both IL 1 and TNF in monocytes-macrophages and, in the case of IFN gamma, to induce the expression of HLA class II antigens in synovial cells. Interleukin 2 produced by activated T lymphocytes is able to induce lymphocyte proliferation and IFN gamma production. Prostaglandins produced by activated monocytes can block IL 2 and IFN gamma secretion. The exact role of this complex network of immunoregulatory mediators in the pathogenesis of RA deserves to be better elucidated.

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.

Hyaluronic acid is an endogenous inducer of interleukin-1 production by human monocytes and rabbit macrophages

When human peripheral monocytes and rabbit peritoneal macrophages were incubated with hyaluronic acid, the media were found to contain interleukin-1 (IL-1) activity and to stimulate collagenase production by rabbit fibroblasts. A digestion of hyaluronic acid by testicular hyaluronidase decreased the IL-1 inducing activity. Polymixin B, an inhibitor of endotoxin, did not exert any effect towards the action of hyaluronic acid. Hyaluronic acid also stimulated human polymorphonuclear leucocytes to produce IL-1 like activity. These results indicate that hyaluronic acid is an endogenous IL-1 inducer and may play important roles in the pathological and/or physiological changes of connective tissues.

The action of human articular-cartilage metalloproteinase on proteoglycan and link protein. Similarities between products of degradation in situ and in vitro

Interleukin 1 stimulation of human articular cartilage in organ culture produced the concomitant release of proteoglycan fragments and latent metalloproteinase. The released fragments ranged in size from that of almost intact proteoglycan subunits to the product of limiting digestion generated by the activated metalloproteinase. None of the fragments possessed the ability to interact with hyaluronic acid. Analysis of proteoglycan aggregate digested with the activated metalloproteinase showed that isolated hyaluronic acid-binding regions were produced from the proteoglycan subunits, and that the two higher-Mr link-protein components (Mr 48,000 and 44,000) were converted into the lowest-Mr component (Mr 41,000). Link protein extracted from cartilage under stimulation with interleukin 1 showed a similar conversion. These results suggest that interleukin 1 stimulates the release of latent metalloproteinase from chondrocytes and that a proportion of the enzyme is activated in situ in the cartilage matrix. The mode of action of the activated enzyme is compatible with a role in the changes in proteoglycan structure seen in aging.

Advances in understanding cell interactions in tissue resorption. Relevance to the pathogenesis of periodontal diseases and a new hypothesis

Much of the connective tissue degradation that takes place in periodontal diseases is mediated by proteolytic enzymes. Previous studies have focused on the action of proteinases released by invading polymorphonuclear neutrophils and macrophages, and bacterial enzymes. In view of recent work establishing that resident connective tissue cells can be induced by cytokines to bring about the destruction of their own matrix, we propose a new hypothesis. In this we envisage that a critical step is the interaction of bacterial antigens with inflammatory cells, resulting in the production of a cytokine, interleukin-1. Our interpretation of in vitro evidence is that the loss of connective tissue attachment and bone matrix resorption in periodontal diseases is mediated by metalloproteinases such as collagenase and stromelysin released by cells of the periodontium. Such proteolytic destruction can be induced by interleukin-1, whose production may not be dependent on a specific microbial flora but may be triggered by a number of organisms. It is now clear that interleukin-1 has multiple actions on both immune and non-immune cells; these include the induction of lymphocyte differentiation and proliferation and the stimulation of bone and cartilage resorption, and prostaglandin and metalloproteinase synthesis by connective tissues. It seems likely that further knowledge about the production and function of this cytokine will have an increasing impact in many diseases that involve resorption, particularly since interleukin-1-like molecules can be produced by cell types other than monocytes/macrophages, including keratinocytes and fibroblasts.

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.

Rheumatoid arthritis: clinical features and pathogenetic mechanisms

Rheumatoid arthritis is a disorder characterized by chronic inflammation affecting predominantly articular tissues, leading in some instances to disruption of the normal structure and function of the joint. In some patients extra-articular manifestations are also present. In the joints, the pathologic lesion consists of synovial cell proliferation with infiltration by inflammatory cells. The complex interaction among these cells is likely responsible for the connective tissue abnormalities that characterize the rheumatoid lesion. The factors responsible for inducing the inflammatory process are unknown.

Effect of a interleukin-1 like factor (mononuclear cell factor) on proteoglycan synthesis in cultured human articular chondrocytes

A partially purified monocyte factor, with Interleukin-1 properties (MCF/IL-1), enhances the proteoglycan synthesis of human neonatal articular chondrocytes in culture, and changes the repartition of these macromolecules between medium and cell layer. The size of the proteoglycan monomers, the length of the glycosaminoglycan chains and the respective levels of chondroitin-6-sulfate, chondroitin-4-sulfate and non sulfated chondroitin remain unchanged under MCF/IL-1 exposures. The addition of indomethacin reduces the stimulation effect by 60-70% only, suggesting that the MCF/IL-1 action is partially dependent on prostaglandins but seems also related to mechanisms distinct from the cyclooxygenase pathway.

Alterations in macrophage collagenase secretion induced by gold sodium thiomalate

The effects of gold sodium thiomalate (GST) on the production of specific collagenase by thioglycolate-elicited macrophages was investigated. Our studies demonstrated that GST administration can significantly decrease collagenase production in a dose-dependent manner. These effects were observed with levels of GST attainable in serum or synovial tissue during routine chrysotherapy. In addition, GST altered lysozyme secretion by activated macrophages in a pattern distinct from that of collagenase alteration. These effects of enzyme secretion were not secondary effects of GST on viability, general protein secretion, or the specific assay procedures utilized, and were not attributable to the thiomalate moiety. Thus, GST may exert its therapeutic effect in rheumatoid arthritis through interference with the production of degradative proteolytic enzymes, which are important effector molecules mediating tissue destruction.

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.

Synthesis of PGE2, collagenase and tissue factor by fibroblast substrains: substrains are differentially activated for different metabolic products

Metabolic heterogeneity has previously been demonstrated for cloned fibroblast populations. It is unclear whether a "high producer" or "activated" phenotype for one cell product reflects general metabolic activation or whether activated phenotypes for different metabolic markers segregate independently among cloned populations. We examined human foreskin fibroblast substrains, isolated by limiting dilution cloning, for heterogeneity in biosynthesis of PGE2 and collagenase (stimulated by Interleukin 1-containing mononclear cell supernates), and tissue factor. Synthesis of these products varied 5- to 10-fold among 16 substrains isolated from two parent lines (AT and WB). Metabolic phenotypes (high versus low levels of synthesis) were stable for the substrains over multiple weeks of culture. In neither group of substrains was there a correlation between levels of stimulated PGE synthesis and stimulated collagenase synthesis (r = -0.24 and 0.29 for AT and WB substrains, respectively). Similarly, tissue factor generation did not correlate with either PGE production (r = 0.12 and -0.38 for AT and WB substrains, respectively) or collagenase synthesis (r = 0.17 and 0.21 for AT and WB substrains, respectively). The discordance between high producer phenotypes for the different products was observed even when all three products were measured in the same culture. Activated phenotypes for different metabolic markers thus appear to segregate among cells independently. The process of connective tissue activation by immune cell-derived mediators may depend on the constituent makeup of the responding connective tissue cell population.

Stimulation of procollagenase synthesis in human rheumatoid synovial fibroblasts by mononuclear cell factor/interleukin 1

In order to define mechanisms regulating the synthesis of procollagenase in human rheumatoid synovial fibroblasts, the proteins synthesized by cultured cells were labeled with [35S]methionine. Labeled medium proteins were analyzed by SDS-PAGE directly and after immunocomplexing with a specific antibody to human fibroblast collagenase. Labeling of both the predominant form of the enzyme (Mr approximately 55 000) as well as a minor species (Mr approximately 61 000) was increased following incubation with the monokine, mononuclear cell factor/interleukin 1. The approximately 61 kDa form of the procollagenase appears to be a glycosylated form of the approximately 55 kDa precursor based on binding to Con A-Sepharose and decrease in the approximately 61 kDa form after culture in the presence of tunicamycin. Thus, mononuclear cell factor, homologous with interleukin 1, partially purified from monocyte conditioned medium increased incorporation of [35S]methionine into several medium proteins, including those complexed by the anticollagenase antibody. In the presence of mononuclear cell factor/interleukin 1, labeling of the procollagenase was increased 12-14-fold over control cultures incubated with medium alone. Therefore, one of the mechanisms involved in increase of collagenase activity in the medium of cultured synovial fibroblasts in the presence of mononuclear cell factor/interleukin 1 is a stimulation of enzyme protein synthesis.

Mononuclear cell-mediated modulation of synovial cell metabolism. II. Increased hyaluronic acid synthesis by a monocyte cell factor (MCF)

Treatment of cultured human synovial cells with a mononuclear cell factor (MCF) enhanced their ability to synthesize glycosaminoglycans (GAG), but GAG repartition between extracellular, pericellular and intracellular compartments was found to be the same as in control. Hyaluronic acid (HA) production, which represents 80-90% of all secreted GAG, was stimulated 2 1/2-3-fold, but the HA molecular weight was not modified. The MCF increased the hyaluronate synthetase activity of synovial cells in similar proportions. Actinomycin D inhibited the increase in hyaluronate synthetase activity produced by MCF, indicating that this increase involves new synthesis of mRNA. Stimulation of both HA synthesis and hyaluronate synthetase activity by MCF was suppressed by 10(-4)-10(-5) M indomethacin (an inhibitor of cyclo-oxygenase), suggesting that MCF effect is prostaglandin-dependent.

Different populations of rheumatoid adherent cells mediate activation versus suppression of T lymphocyte proliferation

Adherent cells from synovial tissue of rheumatoid arthritis patients were fractionated on Percoll density gradients and analyzed to determine phenotypes, effects on allogeneic T lymphocyte proliferation, and production of prostaglandin E2 (PGE2). Cells expressing HLA-DR predominated in all fractions, and esterase-positive cells were enriched in light fractions. Heavy cells were potent stimulators in the mixed lymphocyte reaction and produced little PGE2, whereas light cells suppressed the mixed lymphocyte reaction and produced a large quantity of PGE2. These results suggest that macrophage-like synovial cells that suppress T helper lymphocyte activity are generated secondary to synovial lymphocyte activation in rheumatoid arthritis.

Enhanced prostanoid release from monocytes of patients with rheumatoid arthritis and active systemic lupus erythematosus

In patients with rheumatoid arthritis high levels of prostaglandin E1 have been found in the joint fluid, and its increased production by adherent synovial cells and macrophages clearly supports the notion that this arachidonic acid metabolite is involved in the pathology of the disease. Besides its known inflammatory qualities and the suppressive effects on various lymphocyte functions prostaglandin E2 has proved to be an essential cofactor in the secretion of the lymphokine osteoclast activating factor. In this study we have discovered an enhanced release of prostaglandin E1 and thromboxane B2 from a subpopulation of blood monocytes from patients with rheumatoid arthritis and active systemic lupus erythematosus. No correlation between prostanoid release from monocytes and inflammatory activity of the disease was found. However, even monocytes from patients with early stage or mild inflammatory activity displayed a 'stimulated' arachidonic acid metabolism. In contrast only patients with active systemic lupus erythematosus showed in this respect comparable secretory activity or monocytes. Our findings may point to a possible pathogenic role of prostanoids in rheumatoid arthritis, which may also have some implication for the early diagnosis of this disease and for its differentiation from other chronic inflammatory rheumatic conditions.

Mononuclear cell-mediated modulation of synovial cell metabolism. I. Collagen synthesis

Human PHA-stimulated mononuclear cells produce a factor which inhibits synovial cell collagen and non-collagen protein synthesis, whereas it enhances hyaluronic acid (HA) production. Indomethacin (10(-4)-10(-6) M), a cyclo-oxygenase inhibitor, suppresses this effect, suggesting that the mechanism is prostaglandin-mediated. The active material, of apparent molecular weight 12 000-20 000, also displays the properties of the mononuclear cell factor (MCF) previously described by others, since its stimulates collagenase and PGE2 release by the cultured synovial cells. Furthermore, it co-purifies with interleukin 1 (IL 1) as shown by lymphocyte-activating factor activity. This strongly suggests that IL 1 could be responsible for some (or all) the effects observed on MCF-exposed synovial cells. From these data, we deduce the possibility that mononuclear cells may participate in limiting synovial collagen deposition in rheumatoid arthritis.

Substrain heterogeneity in prostaglandin E2 synthesis of human dermal fibroblasts. Differences in prostaglandin E2 synthetic capacity of substrains are not stimulus-restricted

We examined prostaglandin E2 (PGE2) biosynthetic heterogeneity in fibroblast substrains and possible mechanisms that might mediate this heterogeneity. PGE2 synthesis of fibroblast substrains, in response to phytohemagglutinin-stimulated mononuclear cell supernates, ranged from 9.0 +/- 1.0 ng/ml to 79.3 +/- 7.4 ng/ml (mean +/- SD). The phenotypic behavior of individual substrains was stable. Substrains were also heterogeneous in PGE2 response to phorbol myristate acetate, and displayed stability in this phenotype as well. Substrains which were high responders to mononuclear cell supernate also ranked high in response to phorbol myristate acetate. Similar heterogeneity was observed in response to purified interleukin-1. Arachidonic acid added exogenously did not raise interleukin-1 responsiveness of low-producer substrains to that of high producers, suggesting that differences in PGE2 synthesis among substrains did not reflect differences in substrate availability or phospholipase activity. Supernates of high- and low-responder phenotype substrains, when added to cells of the reciprocal strain or to unrelated fibroblasts, did not affect the pattern of PGE2 synthesis. The concordance of substrain responsiveness to mononuclear cell supernate and phorbol myristate acetate suggests that heterogeneity among substrains in PGE2 synthesis is related to the ability to produce PGE2, rather than to the ability to respond to a given mediator. In addition, differences in PGE2 synthesis among substrains do not appear to result from release of regulatory autokines.

Soluble mediators from mononuclear cells increase the synthesis of glycosaminoglycan by dermal fibroblast cultures derived from normal subjects and progressive systemic sclerosis patients

Dermal fibroblast cultures from patients with progressive systemic sclerosis (PSS) synthesize up to 5 times more glycosaminoglycan (GAG) than normal cultures. In an in vitro model of fibroblast-lymphocyte interactions, we show that the supernatants of activated mononuclear cells (MNC) modulate GAG synthesis, as measured by the incorporation of 3H-glucosamine into GAG following incubation of the confluent fibroblast monolayers with active supernatant preparations. GAG accumulation was selectively increased up to 18 times in normal dermal fibroblast cultures. Cell viability was not affected, and 3H-thymidine uptake and cell numbers were depressed in cultures treated with the supernatants. In contrast to normal dermal fibroblast cultures, PSS fibroblasts responded to MNC supernatants by only a 1-2-fold increase in GAG. Supernatants of concanavalin A-activated PSS MNC had higher stimulatory activity than those of normal MNC. Supernatants made with MNC that had been depleted of monocytes on Sephadex G-10 columns were only minimally stimulatory. The GAG-stimulatory supernatants modulated the synthesis, but not the degradation of GAG. Gel filtration on a calibrated Sephadex G-100 column indicated the presence of stimulatory activity in both the 50,000 and 15,000 molecular weight fractions. These activities were trypsin-sensitive, but had different susceptibilities to heat. The active column fractions also contained interleukin-1 activity, as shown in an assay measuring proliferation of mouse thymocytes. Like our factors, interleukin-1 preparations increased GAG in normal and PSS dermal fibroblasts. Products of activated MNC may modulate normal and pathologic processes in human skin.

Partial purification of a factor from human synovium that possesses interleukin 1, chondrocyte stimulating and catabolin-like activities

Human synovial explants in culture release material that stimulates the production of prostaglandin E2 (PGE2) and several extracellular enzymes by human chondrocytes. Fractionation of conditioned medium by gel filtration revealed a protein of approx. 15 kDa, which in addition to stimulating production of PGE2 and plasminogen activator by human articular chondrocytes, possessed interleukin 1 activity and induced cartilage degradation. Further purification using iso-electric focussing again showed co-elution of these activities with a major pI of 6.9 and a minor pI of 5.1-5.3. This study indicated that human synovium releases a factor that is closely related to or identical with interleukin 1 and suggests that this protein may participate in cellular interactions that occur within the rheumatoid joint.

Quantitative histologic studies on the pathogenesis of periarticular osteoporosis in rheumatoid arthritis

The pathogenesis of periarticular osteopenia in rheumatoid arthritis (RA) was investigated by histomorphometry on juxtaarticular bone removed during joint surgery. Twenty areas from 12 RA patients were compared with 14 areas from 6 osteoarthritis (OA) patients. There was no difference between the 2 groups in the percent of total bone volume. However, increased bone formation was suggested by an increase in the percent of active osteoid surface in RA compared with that in OA. Bone resorption was also increased in RA, as evidenced by increases versus OA in percent total resorptive surface, percent active resorptive surface, and number of osteoclasts. These results demonstrate increased turnover of bone in RA, especially in the resorptive phase of the periarticular trabecular bone. It is proposed that soluble factor(s) synthesized in the contiguous rheumatoid synovium may be transferred to the periarticular bone space, stimulating osteoclasts to resorb bone.

Modulation of connective tissue metabolism by partially purified human interleukin 1

We have investigated the relationship between the monokine interleukin 1 (IL-1) and the connective tissue-stimulating activities produced by monocytes such as mononuclear cell factor (MCF). Using almost exclusively human tissue we have monitored a wide range of MCF-like activities through the partial purification of IL-1 by gel filtration and isoelectric focusing. Activities measured include stimulation of chondrocytes to produce prostaglandins, plasminogen activator and proteoglycanase, enhancement of synovial cell proliferation, and stimulation of cartilage resorption, in addition to IL-1 (lymphocyte activating factor) activity. The activities described show the same molecular heterogeneity; the active material has similar potencies in the different systems, and removal of IL-1 activity by pretreatment with phenylglyoxal also results in loss of the connective tissue-stimulating activities. These results show that the factors responsible for this wide range of activities are very closely related to IL-1 and give further evidence in support of the possible involvement of IL-1 in the processes of joint destruction occurring in chronic inflammatory conditions such as rheumatoid arthritis.

Peripheral blood mononuclear cells stimulate N-acetyl-beta-glucosaminidase levels of human synovial fibroblast-like cells

Fibroblast-like synovial cells isolated from intact joints of non-arthritic human donors released up to nine-times higher activity of the lysosomal acid hydrolase N-acetyl-beta-glucosaminidase (NAG) than controls when incubated in conditioned medium from homologous peripheral blood mononuclear cells (MCCM). This increase occurred without decrease in cell numbers or other evidence of cytotoxicity. An increase in cell-associated NAG activity was also suggested, but this was not statistically significant. Indomethacin present during production of MCCM or added with MCCM to fibroblast cultures did not alter the response to MCCM, indicating that the effect of MCCM was not due to the presence of products from the cyclo-oxygenase pathway. At a concentration known to block protein synthesis in most cells (10(-5) M), cycloheximide markedly suppressed the NAG releasing response to MCCM. The secretion of NAG due to MCCM was not affected by all-trans retinoic acid (10(-6) M) but was suppressed by the corticosteroid, dexamethasone.