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

Latent collagenase of rheumatoid synovial fluid is not of granulocytic origin

The physicochemical properties of three latent collagenases derived from rheumatoid synovial fluid, polymorphonuclear leucocytes and culture medium of rheumatoid synovium were compared. It has been shown that synovial fluid enzyme is similar to that of synovium collagenase from tissue culture and differs significantly in molecular size and protein charge from granulocyte collagenase. The results indicate that the latent, trypsin-activable collagenase present in rheumatoid synovial fluid is not of granulocytic origin and seems to derive from the synovial membrane.

Histopathological and ultrastructural studies of synovium in Milwaukee shoulder syndrome--a basic calcium phosphate crystal arthropathy

Light and electron microscopic study of synovial specimens from four patients with the Milwaukee shoulder syndrome disclosed vascular congestion, villous and focal synovial lining cell hyperplasia, occasional giant cells, and fibrin deposition both within and on the surface of the synovium. Although these changes are non-specific, the finding of basic calcium phosphate crystal aggregates in all four cases and the near total absence of an inflammatory reaction are helpful in distinguishing this condition from other types of arthritis. The focal areas of synovial cell hyperplasia may relate to the powerful mitogenic effect of both synthetic and naturally occurring calcium-containing crystals in concentrations found in the synovial fluid of these patients.

Effects of prostaglandin E2, indomethacin, trifluoperazine and drugs affecting the cytoskeleton on collagenase production by cultured adherent rheumatoid synovial cells

Cultured adherent rheumatoid synovial cells with fibroblast properties release large amounts of collagenase and prostaglandin E2 (PGE2) into the medium. With age in culture and passage of the cells, the levels of collagenase and PGE2 decrease, but can be increased by a factor (MCF; mononuclear cell factor) released by cultured human blood monocyte-macrophages. The magnitude of the stimulation varies with different synovial cell strains. To determine some of the mechanisms which regulate the collagenase response, synovial cells were exposed to a cyclooxygenase inhibitor (indomethacin) and substances which alter the cytoskeleton (cytochalasin B or colchicine) or interact with Ca2+ X calmodulin (trifluoperazine). The collagenase response was retained even when PGE2 synthesis was totally blocked with indomethacin. The collagenase response, however, was blunted at high indomethacin concentrations (greater than 10 microM) and paradoxically augmented at lower indomethacin concentrations (0.001 microM). In some synovial cell strains, the blunting effect of 10 microM indomethacin was reversed by the addition of low concentrations of exogenous PGE2 (10 ng/ml). Preincubation of synovial cells for 1 or 24 hr with colchicine or cytochalasin B (1-10 microM) resulted in an augmented collagenase and PGE2 response to MCF. Cells preincubated or incubated with 1-50 microM trifluoperazine, a phenothiazine, also augmented collagenase stimulation by MCF, but, in contrast to colchicine or cytochalasin B, trifluoperazine suppressed the PGE2 response. Thus, although PGE2 and collagenase production by synovial cells may be dissociated, altering ambient PGE2 levels affected basal collagenase production and modulated the collagenase response to MCF.

The effects of monocyte-conditioned medium and interleukin 1 on the synthesis of collagenous and non-collagenous proteins by mouse bone and human bone cells in vitro

Cultured adherent human mononuclear cells produce factor(s) which stimulate the release of calcium from new-born mouse calvaria in organ culture. This stimulation of bone resorption is accompanied by an inhibition of the incorporation of [3H]proline into collagen which is independent of increased prostaglandin production by the bone. When human osteoblast-like cells are treated with conditioned medium from human mononuclear cells, collagen accounts for a decreased proportion of the protein synthesised. This effect on matrix synthesis is not accompanied by an inhibitory action of the monocyte-conditioned medium preparations on net cell proliferation. In human osteoblast-like cell cultures, partially purified human interleukin 1 also inhibits the production of the bone-specific protein osteocalcin in a dose-dependent fashion. These observations are consistent with the hypothesis that products of human monocytes similar to, or identical with, human interleukin 1 may be important regulators of bone metabolism and may contribute to the bone loss seen in diseases such as chronic rheumatoid arthritis.

Degradation of cartilage proteoglycan and collagen by synovial cells. Stimulation by macrophages under activation by phagocytosis, lymphocyte factors, bacterial products or other inflammatory stimuli

When cultured together with dead 35S-labelled cartilage discs or at the surface of [3H]proteoglycan/[14C]collagen-coated plates, synovial cells from either arthritic or normal rabbit joints digested both the proteoglycan and the collagen of the substrates after a lag-period of 1-2 days. These digestions were inversely related to the age (number of subculture passages) of the synovial cells and they could be modulated by serum components that were either inhibitory or stimulatory. They were dependent on a protein synthesis by the cells and were paralleled, in young cultures, by the release of collagenase and of a proteoglycan-degrading neutral proteinase. The co-culture of synovial cells with macrophages or their culture with macrophage-conditioned culture media caused a more rapid and more extensive degradation of collagen and proteoglycan due to the stimulation of the synovial cells by a nondialysable macrophage factor. The production of this synovial cell-activating 'matrix regulatory monokine' by the macrophage was enhanced by several immunological or inflammatory stimuli such as lymphocyte factors, phagocytosis, asbestos fibres, endotoxin, adjuvant muramyl dipeptide or chemotactic formyl-methionyl peptide, as well as by other membrane-active agents (phorbol myristate acetate, concanavalin A). It is presumed that these interactions are of importance in the development of cartilage destruction in rheumatoid and other chronic inflammatory arthritis.

Heparin modulates intracellular cyclic AMP in human trabecular bone cells and adherent rheumatoid synovial cells

Cells were cultured from explants of human trabecular bone excised from eight patients and incubated usually for 20 minutes with bovine parathyroid hormone, salmon calcitonin, prostaglandin E2, or heparin. The intracellular content of cyclic AMP was measured by radioimmunoassay and was significantly increased by parathyroid hormone in four, by calcitonin in two, by prostaglandin E2 in eight, and by heparin in seven out of eight cultures. In the two cultures containing calcitonin-responsive cells heparin inhibited the cyclic AMP response induced by calcitonin. Heparin did not affect the cyclic AMP response to parathyroid hormone or prostaglandin E2. Heparin also increased the cyclic AMP content of cultured adherent rheumatoid synovial cells. It is proposed that, in certain situations of focal pathological bone resorption, although concentrations of circulating hormones may be normal, the local release of products such as heparin may modify the effect of hormones which regulate connective tissue homoeostasis. local changes in hormone responses could contribute to the enhanced bone resorption associated with inflammatory processes such as rheumatoid arthritis.

A fibrosarcoma model derived from mouse embryo cells: growth properties and secretion of collagenase and metalloproteinase inhibitor (TIMP) by tumour cell lines

A new murine fibrosarcoma model has been developed in which it is possible to compare in vitro the behaviour of tumour cells with that of normal parental cells from which the tumour was originally derived by spontaneous transformation in vitro. Tumour cell lines were obtained which showed differing capacities for localized invasion of the skin following subcutaneous injection: these were categorized as either highly invasive or poorly invasive and were compared with the normal cells for (I) their respective saturation densities when grown on plastic, (2) their ability to grow in agar, and (3) their secretions of the metalloenzyme collagenase and the specific inhibitor of metalloproteinases (TIMP). Although increased in vitro saturation density showed some correlation with increased invasiveness in vivo, the most striking correlation was the 10- to 20-fold reduction in TIMP secretion by tumour cells of high invasive potential compared with normal cells or tumour cells with low invasive potential. No collagenase secretion by tumour cells was ever detected. It is proposed that local TIMP levels may play a crucial in the control of tumour invasion in vivo.

In vitro activation of human chondrocytes and synoviocytes by a human interleukin-1-like factor

Monocytes have been shown to secrete factors which stimulate the destruction of cartilage. Since one of the monocyte products, interleukin-1 (IL-1), has been shown to stimulate the release of collagenase and prostaglandin E from synoviocytes, we have investigated whether IL-1 is also responsible for chondrocyte activation. Purified preparations of IL-1 derived from human blood monocytes stimulated the production of prostaglandin E and plasminogen activator by human articular chondrocytes. After Sephadex G-75 chromatography, the lymphocyte-activating and the chondrocyte-activating activities of IL-1 eluted together in the regions corresponding to the void volume and to Kav = 0.2-0.3 (Mr 30,000-45,000) and Kav = 0.5-0.65 (Mr 12,000-17,000). The major peak of stimulating activity was the 12,000-17,000 dalton peak. Upon further analysis of the 12,000-17,000 dalton peak by isoelectric focusing, the major peak of lymphocyte-activating factor activity was recovered at a pI of 6.3 with a minor peak at 4.6-5.3. Similar patterns of activity were observed when the fractions were assayed for the stimulation of the production of prostaglandin E and plasminogen activator by human chondrocytes and of prostaglandin E by human synoviocytes. Treatment of the partially purified lymphocyte activating factor with phenylglyoxal reduced the thymocyte-stimulating activity 99% and the chondrocyte-stimulating activity 100%. These results suggest that IL-1 may stimulate the degradation of connective tissues during inflammation.

Connective tissue antigens stimulate collagenase production in arthritic diseases

Peripheral blood mononuclear cells from patients with rheumatoid arthritis (n = 27), systemic lupus erythematosus (n = 24), juvenile rheumatoid arthritis (n = 30), osteoarthritis (n = 20), apparently healthy adults (n = 12), and nonarthritic children (n = 8) were exposed to several putative connective tissue antigens to determine if the monokine, mononuclear cell factor, was released. Release of this factor was detected by bioassay in which enhancement of collagenase production from human synovial cells or dermal fibroblasts was measured. The antigens, all of homologous tissue origin, included cyanogen bromide-derived peptides of type I, II, and III collagens, type I and II helical collagens, and cartilage proteoglycan. Of the subjects examined, 44% of the rheumatoid group, 42% of the systemic lupus group, 33% of the juvenile rheumatoid group but only 10% of the osteoarthritic group and 5% of the control group released monokine after exposure of peripheral blood mononuclear cells to at least one of these connective tissue antigens. Patients with rheumatoid arthritis most frequently responded to type II peptides (but not to type II helical collagen) although the frequencies of responses to type I peptides, type I helical collagen and proteoglycan were also elevated over levels observed in the control population. Positive responses in these patients typically occurred to only one antigen, were transient, often occurred close to the onset of arthritis, and appeared to be unrelated to disease activity. The profiles of responses in patients with juvenile rheumatoid arthritis and systemic lupus shared many features in common and were distinct from those of adult rheumatoid arthritis. Patients with systemic lupus or juvenile rheumatoid arthritis responded to all of the antigens tested. Positive responses often occurred simultaneously to several antigens. Responses to type II helical collagen were most common while sensitization to type II peptides was infrequently detected. Positive responses were transient, unrelated to overall disease activity, type of juvenile arthritis, or duration of disease in lupus patients. Stimulation of mononuclear cell factor release by connective tissue molecules and their degradation products may make an important contribution to the chronic inflammation commonly seen in these diseases.

Interleukin 2-independent stimulation of rabbit chondrocyte collagenase and prostaglandin E2 production by an interleukin 1-like factor

In the present study, interleukin 1 (IL 1)-containing media from different sources, namely a murine macrophage cell line (P388D1), rabbit peritoneal macrophages, and human peripheral blood mononuclear cells, were compared for their effect on thymocyte proliferation and on collagenase and PGE2 secretion by chondrocytes. A high correlation was found between the enhancement of thymocyte proliferation and the induction of collagenase and PGE2 secretion by chondrocytes. Furthermore, a highly purified IL 1-like factor, namely mononuclear cell factor (MCF) was also active on chondrocytes. The addition of highly purified IL 2 to rabbit chondrocytes had no effect on collagenase and PGE2 secretion induced by IL 1-containing media. Our findings suggest that the factor which induced collagenase and PGE2 secretion by rabbit chondrocytes was an IL 1-like factor. Thus, collagenase secretion by chondrocytes may be used as an IL 2-insensitive assay for the detection of IL 1-like factors.

Radioimmunoassay of soluble and insoluble collagenases in fibrotic liver

We have postulated that an insufficient active of collagenase relative to increased collagen synthesis may be the cause of the increased collagen accumulation in fibrotic tissues. In the present study, 125I-collagenase and rabbit anti-collagenase immunoglobulin G were used to develop a sensitive radioimmunoassay that detects 0.1 nM (3 ng) of collagenase protein in tissue samples. The assay also can detect collagenase protein that is associated with extracellular-matrix collagen fibrils. Good correlation with an assay of enzyme activity validates the radioimmunoassay for quantification of collagenase. The assay was used to measure amounts of collagenase in relation to fibrotic processes in livers of mice with schistosomiasis. Results indicate that the amounts of collagenase relative to synthesized collagens were significantly lower, and this may contribute to the progressive fibrosis. The occurrence of a maximum amount of collagenase at 7 weeks after infection with Schistosoma mansoni cercariae in concanavalin A-treated animals, as compared with 8 weeks in controls, could account for the large remission of fibrosis in mice so treated. The results emphasize the possible importance of collagenase in controlling or limiting fibrosis.

Rheumatoid synovial cell hormone responses modulated by cell-cell interactions

Cellular interactions within the rheumatoid synovium are likely to be responsible for the destructive properties of this tissue. The responses to hormones which regulate connective tissue metabolism may also be influenced by these cell-cell interactions. To determine the effect of cellular interactions on responses to hormones, human peripheral blood mononuclear cells were cocultured with adherent rheumatoid synovial cells. Coculture resulted in a decrease in response to prostaglandin E2 as assessed by a reduction in the magnitude of the acute prostaglandin-induced cyclic AMP response. In contrast, coculture resulted in an increase in the magnitude of the acute parathyroid hormone-induced cyclic AMP response. The decrease in response to prostaglandin was reversed by the presence of indomethacin during the preincubation, whereas indomethacin had no effect on the cyclic AMP response to parathyroid hormone. Increases in endogenous synovial cell prostaglandin production (stimulated by soluble factors released by the mononuclear cells) accounted for the subsequent decrease in the response to exogenous prostaglandin. The increase in cyclic AMP response to parathyroid hormone could not be explained by a soluble factor and was independent of ambient prostaglandin levels.

Clonal heterogeneity in the fibroblast response to mononuclear cell derived mediators

Human dermal fibroblasts were examined for heterogeneity in proliferation and prostaglandin E2 (PGE2) synthetic response to supernates of mitogen activated mononuclear cell cultures. Eleven substrains from a single neonatal foreskin culture displayed marked clonal heterogeneity in the fibroblast response to mononuclear cell derived mediators. Supernates of mononuclear cell cultures stimulated fibroblast PGE2 synthesis and suppressed proliferation. Substrains displayed tenfold differences in PGE synthesis and the extent of growth suppression. Release of immunologic mediators at sites of inflammatory lesions could lead to alterations in the clonal composition and phenotypic expression of connective tissue cells.

An electron microscopic study of the synovial-bone junction in rheumatoid arthritis

The cellular characteristics of the rheumatoid synovial-bone junction (SBJ) were examined in the electron microscope. Large numbers of mononuclear inflammatory cells along the bone suggested the advance of the rheumatoid inflammatory lesion into bone tissue. The SBJ contained macrophage-rich and osteoclast-rich areas. The presence of the macrophage as a predominant cell type and the marked collagenolysis of the eroded bone matrix suggested that collagenase released by macrophages was responsible for a major portion of the bone erosion. The observation of osteoclasts with ruffled borders, containing free bone crystals in close contact with the bone, indicated that these osteoclasts were stimulated by the rheumatoid synovium. It seems likely that articular bone resorption depends upon the local host response to the macrophage and osteoclast in the rheumatoid joint.

Microinjury to the synovial membrane may cause disaggregation of proteoglycans in rabbit knee joint articular cartilage

Proteoglycans (PGs) isolated from articular cartilage (AC) of mature rabbits subjected to two or more consecutive intraarticular (IA) injections of sterile saline 24 h apart showed an aggregation defect in the presence of excess hyaluronic acid (HA). Although the PG contents of experimental and control cartilages were indistinguishable, a higher proportion of PGs were extractable from the 3 X IA tissues, as assessed by uronic acid analysis. Proteoglycans from experimental and control cartilages when examined by Sepharose CL-2B chromatography showed two subunit populations, the smaller (KAV = 0.70) containing more ketatan sulphate than the larger (KAV = 0.31). Cultures of AC from IA joints released more 35SO4-labelled PGs into the media over 72 h than control tissues and consisted mainly of PG degradation products although 20% could aggregate in the presence of HA. Examination of PG aggregation 2 weeks after 2 X IA or 3 X IA injections showed that the defect initiated was still present; however, cartilage of immature rabbits was not affected by the 2 X IA procedure.

Induction of collagenase synthesis in chondrocytes by a factor synthesized by inflamed synovial tissue

Rabbit inflamed synovial tissue grown in culture synthesizes a factor that induces collagenase synthesis in chondrocytes and in cartilage. Synthesis of this factor by the synovial tissue is inhibited by cycloheximide but not by indomethacin. The factor has an apparent molecular weight of 30,000, is stable to heat and to trypsin treatment but is inactivated by acid. Induction of collagenase synthesis in chondrocytes occurs after a lag period of 6 hours.

Bone resorption in cholesteatomas. An experimental study

A model for studying different aspects of human cholesteatomas in vivo in the immunodeficient "nude' mice is described. Epithelial-mesenchymal interaction was studied in human cholesteatoma membranes, transplanted to the flank region. Findings of cystic lesions lined by stratified keratinizing epithelium were frequent and the connective tissue reaction were weak. Furthermore human cholesteatomy membranes were transplanted into the middle ear cavity of the "nude' mice. After 21-28 days bone resorption was shown in the labyrinthine capsule, not always with sign of inflammation.

Characterization of blood mononuclear cells of rheumatoid arthritis patients. II. Depressed PPD presentation by monocytes to T lymphocytes

Purified blood monocytes from patients with rheumatoid arthritis (RA) were significantly less capable of presenting purified protein derivative of tuberculin (PPD) to autologous lymphocytes than monocytes from patients with osteoarthritis, degenerative spine diseases, or healthy controls. Since lymphocytes from RA patients exhibited a normal response to soluble PPD or concanavalin A, the lowered T-cell reactivity had to be attributed to a diminished antigen-presenting capacity of monocytes. Several reasons may be responsible for this altered monocyte function in rheumatoid arthritis: a shift of monocytes to subpopulations expressing less Ia-like antigens, an inherent monocyte disorder, or a "preactivation" of monocytes associated with a reduced antigen-presenting capacity.

Purification to homogeneity of pig leucocyte catabolin, a protein that causes cartilage resorption in vitro

Catabolin, a protein that causes proteoglycan resorption in explants of living cartilage, was purified to homogeneity from culture medium conditioned by culturing buffy-coat leucocytes from 60 litres of pig blood in the presence of concanavalin A. The purification steps were (1) gel filtration of concentrated medium, (2) chromatofocusing, (3) hydroxyapatite chromatography, (4) anion-exchange chromatography (Mono Q), (5) reversed-phase high-pressure liquid chromatography (h.p.l.c.) (Zorbax ODS). These achieved approx. 9000-fold purification from the starting material. The purified protein when reduced ran as a single band on sodium dodecyl sulphate (SDS)/polyacrylamide-gel electrophoresis with Mr 21000. On isoelectric focusing its pI was 4.8-5.0, and there was evidence of micro-heterogeneity. The protein co-migrated with active material on h.p.l.c., isoelectric focusing and SDS gels (15 and 12.5% acrylamide) under both reducing and non-reducing conditions. The pure protein caused proteoglycan release from cultured bovine nasal cartilage at 20pM. Its possible identity with interleukin 1 is discussed.

Morphologic and mitogenic responses of rabbit synovial fibroblasts to transforming growth factor beta require transforming growth factor alpha or epidermal growth factor

We tested the hypothesis that normal synovial fibroblasts might proliferate in response to transforming growth factors (TGFs), peptides that are extracted with acid-ethanol from bovine kidney or salivary gland and that cause anchorage-independent growth of normal cells. A 72-hour exposure of confluent monolayers of rabbit synovial fibroblasts in 10% fetal calf serum to partially purified TGF-beta in the presence of TGF-alpha gave a 2- to 5-fold increase in incorporation of 3H-thymidine, protein content, and cell number. Similar results were obtained with high pressure liquid chromatography-purified TGF-beta in the presence of epidermal growth factor (EGF) (a type of TGF-alpha). By itself, purified TGF-beta was not mitogenic; it depended absolutely on EGF. However, only TGF-beta along with EGF, and not EGF alone, induced a marked morphologic change: a piling up of cells into foci resembling those commonly seen in primary cultures of rheumatoid synovial cells. Mitogenic responses induced by the TGF-beta-EGF combination were prevented by all-trans-retinoic acid but not by indomethacin or dexamethasone. The data indicate that TGF-beta, a peptide extracted from normal cells, can act in concert with EGF to cause proliferation and piling up of synovial cells and raise the possibility that these factors may play a role in rheumatoid arthritis and other proliferative but nonmalignant diseases as well.

Effects of retinol and dexamethasone on cytokine-mediated control of metalloproteinases and their inhibitors by human articular chondrocytes and synovial cells in culture

Human articular chondrocytes in culture produced large amounts of specific mammalian collagenase, gelatinase and proteoglycanase when exposed to dialysed supernatant medium derived from cultured human blood mononuclear cells (mononuclear cell factor) or to conditioned medium, partially purified by fractionation with ammonium sulphate (60-90% fraction), from cultures of human synovial tissue (synovial factor). Human chondrocytes and synovial cells also released into culture medium an inhibitor of collagenase of apparent molecular weight about 30 000, which appeared to be similar to the tissue inhibitor of metalloproteinases synthesised by tissues in culture. The amounts of free collagenase inhibitor were reduced in culture media from chondrocytes or synovial cells exposed to mononuclear cell factor or synovial factor. While retinol inhibited the production of collagenase brought about by mononuclear cell factor or synovial factor, it restored the levels of inhibitor, which were reduced in the presence of mononuclear cell factor or synovial factor. Dexamethasone markedly reduced the production of collagenase by synovial cells, while only partially inhibiting factor-stimulated collagenase production by chondrocytes. Addition of puromycin as an inhibitor of protein synthesis reduced the amounts of both collagenase and inhibitor to control or undetectable levels.

Effect of heavy metals on human rheumatoid synovial cell proliferation and collagen synthesis

The dose-dependent effects of heavy metals on cell proliferation, collagen synthesis, and non-collagen protein synthesis were studied in early passage cultures of human synovial cells exposed to 1-100 microM concentration of gold, silver, mercury, cadmium or lead for 5 days. The incorporation of [3H]thymidine into trichloroacetic acid insoluble material was inhibited 50% by each of the heavy metals at concentrations between 1 and 10 microM. Gold, lead and mercury (10 microM) decreased the DNA content of the cultures by less than 15%; silver (10 microM) and cadmium (10 microM) resulted in decreased DNA content, which was attributed to cytotoxicity. A dose-dependent inhibition of [3H]proline incorporation into bacterial collagenase resistant (non-collagen) protein was observed after incubation with 10 microM mercury, lead and silver. During incubations with 10 microM gold and cadmium, collagenase resistant protein accumulation increased. All the heavy metals except for gold inhibited collagen accumulation to a greater extent than non-collagen protein accumulation. Gold (10 microM) stimulated the amount of collagen produced per cell, and the percentage of collagen to total protein was increased 50%. The rate of collagen accumulation in medium decreased during incubation with 10 microM silver, mercury, cadmium and lead. The stimulation of collagen synthesis may be a unique property of gold related to the therapeutic indices of gold, compared to other heavy metals, in rheumatoid arthritis.

Effects of glycosaminoglycan-polysulfate and two non-steroidal anti-inflammatory drugs on prostaglandin E2 synthesis in Chinese hamster ovary cell cultures

We have studied the influence of a polysulfated glycosaminoglycan (Arteparon) in comparison with indomethacin and piroxicam on the synthesis of prostaglandin E2 in Chinese hamster ovary cell cultures (CHO). The two non-steroidal anti-inflammatory drugs (NSAD) were found to be strong inhibitors of prostaglandin E2 (PGE2) synthesis. The inhibition was found to be dose-dependent. Arteparon, an antidegenerative drug for the treatment of osteoarthritis, was also found to inhibit PGE2 synthesis in the CHO cell cultures. The inhibition was not as strong as that of the NSAD and no correlation between the concentration of Arteparon and the inhibition of PGE2 synthesis could be demonstrated.

Inhibition of cartilage breakdown by hydrocortisone in a tissue culture model of rheumatoid arthritis

Bovine nasal cartilage discs cocultured with human rheumatoid synovial membrane or synovial-membrane-conditioned media release proteoglycan largely as a result of cartilage breakdown. We assessed the effects of hydrocortisone on proteoglycan distribution between cartilage and culture medium, and on cartilage breakdown expressed as the release of either proteoglycan or 35S-products from prelabelled discs. The presence of synovial membrane inhibited the capacity for net proteoglycan synthesis, preventing its accumulation in cartilage; this was little affected by hydrocortisone. The major response to pharmacological concentrations of hydrocortisone was suppression of both spontaneous and synovial-membrane-induced cartilage breakdown. The autolysis of synovial protein that normally occurred during culture was similarly prevented by comparable doses of corticosteroid. Changes in chromatographic distribution of the 35S-labelled degradation products released from cartilage conformed with a corticosteroid-induced inhibition of endogenous lysosomal or related proteinase activity. Additionally, inhibition of the early events in synovial membrane that are responsible for chondrocyte-mediated breakdown of cartilage may contribute significantly to the overall corticosteroid effect.

The interaction of purified rabbit bone collagenase with purified rabbit bone metalloproteinase inhibitor

1. Pure rabbit bone metalloproteinase inhibitor (TIMP) bound tightly to pure rabbit bone collagenase with an apparent Kd of 1.4 X 10(-10) M. 2. The molecular weight of the enzyme-inhibitor complex was found to be 54 000, but no enzyme activity could be recovered from the complex after treatment with either mercurials or proteinases. The complex thus differed from latent collagenase in terms of size, susceptibility to mercurials and behaviour on concanavalin A-Sepharose. 3. The interaction of the purified components was compared with that of crude collagenase and crude inhibitor in culture medium. Mercurial treatment partially reversed the inhibition in the crude system, but not when the purified components were used. 4. The significance of the results is discussed in relation to the extracellular control of the activity of collagenase.

Fibroblast prostaglandin E2 synthesis. Persistence of an abnormal phenotype after short-term exposure to mononuclear cell products

Acquired abnormalities of connective tissue metabolism in inflammatory diseases often persist when lesional tissue is maintained in in vitro culture. Although connective tissue cells are exposed to inflammatory cell-derived mediators in vivo and such mediators have been shown to alter connective tissue cell behavior, it is unclear whether the persistence of metabolic defects in vitro could result from remote in vivo exposure to these mediators. An in vitro model was used to test whether transient exposure of normal fibroblasts to inflammatory mediators could lead to metabolic alterations that persist during in vitro culture. Short-term exposure of human foreskin fibroblasts in vitro to supernates of mitogen-activated peripheral blood mononuclear cells led to persistent abnormalities of prostaglandin E2 (PGE2) metabolism. Fibroblasts previously exposed to mononuclear cell products synthesized more than twice as much PGE2 when stimulated compared with similarly stimulated but previously unexposed control fibroblasts of the same strain. The enhanced PGE2 synthesis persisted for as long as 20 wk and 19 cell generations after the original exposure to mononuclear cell products. Exposure of fibroblast populations to mononuclear cell products may, thus, lead to metabolite alterations that are still evident after multiple cell generations.

Morphologic observations in the early phase of the cartilage-pannus junction. Light and electron microscopic studies of active cellular pannus

The early phase of cartilage destruction by active cellular pannus in rheumatoid joints was observed under light and electron microscopy. In the early phase of pannus formation, cartilage was covered by several layers of fibroblast-like cells. This was also the case at the advancing edge of the pannus. Invasion of the cartilage by macrophage-like cells has been observed to start beneath this layer. Observations under electron microscope demonstrated that the main cells participating in the cartilage destruction at the cartilage-pannus junction were either fibroblast-like or macrophage-like cells, and suggested the possibility that these two types of cells were derived from synovial type A and type B cells. Morphologic observations also suggested a possibility of transformation of the fibroblast-like cell into the macrophage-like cell at the cartilage-pannus junction.

Immune regulation of collagenase secretion in rheumatoid and osteoarthritic synovial cell cultures

Primary cultures of synovial cells were obtained by proteolytic dispersion of synovial tissue from patients with rheumatoid arthritis (n = 19), psoriatic arthritis (n = 2), osteoarthritis (n = 13) and other joint problems (n = 3). The levels of endogenously secreted collagenase were variable from patient to patient but did not differ significantly between rheumatoid arthritis and osteoarthritis. The endogenous collagenase secretion was likely a consequence of mononuclear cell factor (MCF) release from monocytes/macrophages which have been shown to be present among the heterogeneous primary rheumatoid synovial cell population (Dayer et al., 1976). As also demonstrated by these investigators, medium containing MCF can be generated from peripheral blood mononuclear cells in a T lymphocyte-dependent process by the addition of phytohemagglutinin (PHA). The addition of such medium stimulated collagenase secretion from all our synovial cell cultures regardless of the endogenous level. Protein synthesis but not synovial cell proliferation was required for MCF stimulation of collagenase secretion. The direct addition of PHA to primary synovial cell cultures stimulated collagenase secretion in some but not all cases indicating the presence of T lymphocytes in these positively-responding cultures. In some of these primary synovial cell cultures in which the addition of PHA stimulated collagenase secretion, secretion was also stimulated by the addition of collagen peptides, native collagen, proteoglycan or purified protein derivative of tuberculin. We propose that, in these instances, MCF release is mediated by antigen-sensitized lymphocytes. Antigen-responsive cultures were not restricted to the rheumatoid population. Our data are compatible with the idea that infiltrated lymphocytes in inflamed synovial tissue become sensitized to cartilage and joint capsule components released during tissue degradation and contribute to matrix destruction by mediating MCF release with consequent stimulation of collagenase synthesis and secretion from synovial cells.

Differential release of plasminogen activator and latent collagenase from mononuclear cell-stimulated synovial cells

Independent studies have previously shown that mononuclear cell supernatants stimulate the release of plasminogen activator and latent collagenase from synovial cell monolayer cultures. Simultaneous secretion of these enzymes could be an important pathway for tissue destruction under inflammatory conditions, since plasminogen activator can cause activation of latent collagenase in the presence of plasminogen. We investigated the kinetics of release of the two enzymes from synovial cells in response to the addition of mononuclear cell supernatants and retinoic acid. Synovial cells derived from osteoarthritic and rheumatoid arthritic patients responded similarly. Plasminogen activator is released within a few hours of stimulation, and secretion usually stops when the stimulus is removed. In contrast, significant amounts of collagenase are secreted only after an initial lag period of 1--2 days, and secretion is sustained long after removal of mononuclear cell supernatant. Another difference in regulation of the secretion of these two neutral proteinases is that the addition of all-trans retinoic acid to the same synovial cell culture elevates plasminogen activator secretion while suppressing that of latent collagenase. Differential regulation of these enzymes under conditions of chronic inflammation may allow for continual accumulation of latent enzyme(s) which are activated during short periods of plasminogen activator release.

Synovial factors and chondrocyte-mediated breakdown of cartilage: inhibition by hydrocortisone

Cartilage-synovium interactions were explored in a model culture system. Bovine nasal-cartilage discs were cocultured with minced rheumatoid synovium or synovium-conditioned media (SCM) in the presence or absence of hydrocortisone. Cartilage breakdown was assessed by the release of proteoglycan (PG) and hydroxyproline, and matrix biosynthesis by [35S]sulfate incorporation during pulse labeling. Chondrocyte-dependent breakdown in response to synovial factors (i.e., "catabolin" activity) was assessed by the difference in PG release between living and dead cartilages. Short-term contact with minced synovial membrane or exposure to its products released at a distance was sufficient to induce cartilage degradation in coculture; continued exposure was not required for breakdown to persist. Conditioned media from short-term synovial culture were similarly potent, and the induced breakdown was chondrocyte dependent. Matrix biosynthesis was inhibited in exposed cartilage but could be rapidly restored to normal on synovium removal despite the persistence of cartilage breakdown. Early hydrocortisone treatment suppressed the initiation of cartilage breakdown in cocultures and largely abolished the appearance of inductive factors in SCM. Later applications had little effect either in cocultures or in catabolin assays. We conclude that synovium-induced breakdown is an early event and that chondrocyte catabolic mechanisms once they have been activated are sufficient to maintain breakdown at a high level. Hydrocortisone, as well as limiting proteolysis, inhibits early tissue interactions at the level of synovial catabolin production or release.

Rheumatoid synovial cell morphologic changes induced by a mononuclear cell factor in culture

Adherent rheumatoid synovial cells in culture produce large amounts of prostaglandin E2 (PGE2) and collagenase. When exposed to a monocyte-derived factor, such cells exhibit marked increases in PGE2 and collagenase production. In addition, cellular morphology becomes more stellate. In the presence of this factor, indomethacin inhibits both PGE2 production and the stellate changes, whereas collagenase production usually continues at a high rate. Addition of PGE2 to cultures reproduces the stellate change as does the cyclic adenosine monophosphate (cAMP) analog 8-bromo-cAMP. Colchicine inhibits morphologic transformation induced by the monocyte-derived factor, whereas cytochalasin B has no effect. It appears that the stellate morphology is dependent upon PGE2-induced cAMP stimulation and is not related to collagenase production per se.

Collagens act as ligands to stimulate human monocytes to produce mononuclear cell factor (MCF) and prostaglandins (PGE2)

Blood mononuclear cells from patients with rheumatoid arthritis produce the lymphokine, leukocyte inhibitory factor (LIF) in response to collagens in vitro, and blood monocytes release prostaglandins (PGE2) and a factor, mononuclear cell factor (MCF) which stimulates collagenase and PGE2 production by cultured synovial cells. We therefore examined the effect of collagens on the production of PGE2 and MCF. Blood mononuclear cells from 6 patients with rheumatoid arthritis and 6 normal subjects were cultured in native human types I, II, or III collagen-coated tubes, or with streptokinase-streptodornase (SK-SD), and the supernatant media derived from these cultures analyzed for the presence of MCF, PGE2, and LIF. Types II and III collagens, as well as SK-SD, markedly stimulated MCF production by the cells from all 12 subjects (MCF activity, expressed as a mean stimulation index (SI) +/- SEM, was 43 +/- 12 for type II, 33 +/- 7 for type III, and 37 +/- 23 for SK-SD). Type I collagen was less stimulatory (mean SI 10 +/- 7). Cells from the patients with rheumatoid arthritis, but not the normal subjects, produced LIF in response to types II or III collagens but not to type I collagen. PGE2 production by blood mononuclear cells paralleled that of MCF, although abrogation of PGE2 release with indomethacin did not reduce MCF production. alpha chains purified from denatured collagens also stimulated MCF production. Using cells from patients with rheumatoid arthritis, type II collagen stimulated production of all three factors in the presence of polymyxin B or fibronectin-depleted serum, suggesting, respectively, that neither endotoxin nor fibronectin were responsible for their generation. Monocytes, purified from normal blood by an adherence technique, but not lymphocytes depleted of monocytes, released MCF and PGE2 when cultured with type II collagen. These results demonstrate that collagens can act as ligands to stimulate monocytes, as well as antigens to stimulate sensitized lymphocytes, to produce soluble factors that may contribute to the destruction of connective tissue.

The effect of lymphokines on proliferation and collagen synthesis of cultured human synovial cells

Human mononuclear cell supernatants were obtained by incubating 3 X 10(6) cells per ml of Dulbecco's modified Eagles medium at 37 degrees C for 24 h or 48 h, either in presence or absence of phytohaemagglutinin. After removal of intact cells, the supernatants were dialysed and diluted (1:1, 1:2, 1:5, 1:10) again using the above medium. The diluted supernatants, containing a final concentration of 10% (v/v) human platelet-factor poor serum, were found to stimulate the proliferation of human synovial cells in culture and to increase both the total amount of collagen and the percentage of Type III collagen synthesized by these cells. Incubation of the mononuclear cells in presence of phytohaemagglutinin appeared to further enhance the stimulatory effects of the supernatants upon the synovial cells. Since activated mononuclear leucocytes such as lymphocytes and macrophages are present in rheumatoid synovia, this study suggests that factors released from activated mononuclear leucocytes may play an important role in the proliferation of rheumatoid synovial tissue and development of the pannus.

Effects of products from macrophages, blood mononuclear cells and or retinol on collagenase secretion and collagen synthesis in chondrocyte culture

Collagenase secretion was studied on cultures of rabbit articular chondrocytes. Differentiation of the cells was assessed by characterizing the type of 3H-labelled collagen produced during treatment with (1) conditioned media from rabbit peritoneal macrophages and human blood mononuclear cells, and (2) with retinol, a potent cartilage resorbing agent in tissue culture. Conditioned media stimulated collagenase secretion. Total collagen synthesis was reduced due to a decrease of synthesis of alpha 1 chains; the amount of alpha 2 chains synthesized was unchanged. This is thought to be due to a reduction in type II synthesis. Retinol did not stimulate collagenase secretion. Total collagen synthesis was reduced by retinol. alpha 2 chain synthesis, however, was significantly increased, suggesting a switch of collagen synthesis in favor of type I collagen, and therefore, dedifferentiation. These results demonstrate that dedifferentiation of chondrocytes with respect to collagen synthesis is not necessarily associated with a stimulation of collagenase secretion.

Collagenases and collagen degradation

Degradation of interstitial collagens probably takes place through different enzymatic mechanisms than degradation of basement membrane and pericellular collagens. Interstitial collagens are resorbed under pathological and physiological conditions by collagenases which function extracellularly and cleave polypeptide chains in the collagen triple helix at specific loci resulting in solubilization from the fibril. Production of collagenase in humans is ascribable to fibroblast-like cells which can be stimulated to synthesize new enzyme for release outside of the cell. In several inflammatory conditions, such as rheumatoid synovitis, modulation of collagenase production is mediated by interactions with surrounding inflammatory cells. Monocyte-macrophages produce a stimulatory factor, which has homologies with interleukin 1, which not only increases collagenase synthesis but also PGE2 synthesis. The PGE2 in turn has profound effects on cellular function. Production of the mononuclear cell factor is modulated by several interactions including T lymphocytes and T lymphocyte products, collagen of the extracellular matrix and the Fc portion of immunoglobulins. It is probable, from analogies with other stimulants such as phorbol myristate acetate, that the increase in collagen synthesis is controlled at the level of transcription. Further regulation of collagenase action outside of the cell is probably accomplished by proteolytic activation of a latent collagenase zymogen and interactions with inhibitory proteins also produced by cells in the local environment of the resorptive process.

Involvement of prostaglandin E and adenosine 3', 5'-monophosphate in lipopolysaccharide-stimulated collagenase release by rat Kupffer cells

Kupffer cells exposed to bacterial lipopolysaccharide in vitro synthesized collagenase and released the major portion of it into the extracellular space while the intracellular level of enzyme was not altered significantly. Cycloheximide prevented the appearance of collagenase in the medium indicating de novo synthesis. Indomethacin, an inhibitor of cyclooxygenase, also blocked collagenase synthesis. In line with this observation. Kupffer cells were found to synthesize substantial amounts of prostaglandin E2 when exposed to lipopolysaccharide; concomitantly, cellular cAMP levels were increased. Indomethacin was shown to abolish the stimulated cAMP formation. Addition to the culture medium of cAMP or dibutyryladenosine 3', 5'-monophosphate as well as of prostaglandin E2 or, to a lesser extent, prostaglandin E1 allowed indomethacin-inhibited cells to resume the production of collagenase. It is proposed that in rat Kupffer cells lipopolysaccharide-elicited collagenase synthesis and excretion is mediated sequentially by stimulated production of prostaglandin E2, enhanced adenylate cyclase activity and increased intracellular cAMP levels.

Evidence in support of a self-perpetuating HLA-DR-dependent delayed-type cell reaction in rheumatoid arthritis

Originating from observations on similarities between the rheumatoid synovial tissue and skin lesions in delayed-type hypersensitivity reactions--similarities as to massive infiltrates of "helper" T lymphocytes close to HLA-DR-expressing macrophage/dendritic cells--a notion is formed on the importance of local macrophage-dependent helper T-cell activation in the rheumatoid joint similar to that in a delayed-type skin reaction. In vitro studies on suspended synovial cells have been used to test and qualify these ideas. It is shown that (i) HLA-DR-expressing cells in normal synovial intima can, like epidermal Langerhans cells, mediate T-cell activation; (ii) the large numbers of rheumatoid synovial HLA-DR-expressing macrophage-like/dendritic cells are heterogeneous and mediate either efficient activation or suppression of T-lymphocyte proliferation, and (iii) specificity of rheumatoid T cells can be analyzed with the help of autologous synovial antigen-presenting cells; a specific anti-collagen type II response is reported in three patients.

Chemical and immunological features of pleural effusions: comparison between rheumatoid arthritis and other diseases

The value of determination of pleural fluid glucose, pH, lactic dehydrogenase, IgG, IgA, IgM, C3, C4, anti-IgG antibody, and hydroxyproline in distinguishing between pleural effusions caused by rheumatoid arthritis (RA) and those resulting from other diseases was studied. The series comprised seven patients with RA and 115 patients with other diseases including systemic lupus erythematosus, tuberculosis, malignant disease, empyema, pneumonia, congestive heart failure, and nonspecific pleural effusion. The low glucose concentration, the low pH and the low C4 level in rheumatoid pleural effusion were the most valuable diagnostic findings. The presence of anti-IgG antibody in pleural fluid was not specific for RA. The concentration of hydroxyproline in pleural fluid and the pleural fluid-to-plasma hydroxyproline ratio were significantly higher in RA than in tuberculosis and malignant disease. The results support the view that local metabolic and immunological phenomena as well as a high turnover of collagen occur in the pleural cavity in RA.

Effects of all-trans-retinoic acid (retinoic acid) and 4-hydroxyphenylretinamide on synovial cells and articular cartilage

We studied the effects of two retinoids, naturally occurring all-trans-retinoic acid (retinoic acid) and the synthetic 4-hydroxyphenylretinamide (4-OH-PRT) on monolayer cultures of rabbit synovial fibroblasts and on explants of rabbit articular cartilage. Treatment of fibroblasts with phorbol myristate acetate (PMA; 10(-8) M) induced the synthesis and secretion of large amounts of collagenase: this was inhibited if the cells were treated with retinoic acid (10(-6) M) or dexamethasone (10(-7 M). Combined treatment with retinoic acid and the steroid prednisolone, at concentrations as low as 19(-10) M, gave an additive inhibition of collagenase production. Both retinoids inhibited collagenase production, but only 4-OH-PRT prevented the increase in prostaglandin E2 (PGE2) induced by PMA. Levels of plasminogen activator were also increased by treatment with PMA, and concomitant addition of either retinoid further enhanced this stimulation. Possible toxicity was assessed by measuring release of glycosaminoglycans (GAG) from explants of articular cartilage. Treatment with retinoic acid induced release of 80% of the total GAG, whereas treatment with 4-OH-PRT resulted in release of 40% of the total, a finding similar to that seen with untreated samples. 4-OH-PRT inhibited production of collagenase and PGE2 by rabbit synovial fibroblasts but was not toxic to articular cartilage.

Bone resorption in human cholesteatomas

In vivo studies of different aspects of bone resorption in human cholesteatomas are described in the immunodeficient “nude” mice. Cholesteatoma membranes were transplanted into the middle ear cavities of the mice. After 21–28 days, growth of cholesteatoma tissue could be demonstrated in 8 of 13 animals. In 7 of these 8 animals bone resorption of the labyrinthine wall and ossicles could be demonstrated; resorption with acute inflammation was found in only two animals. The cellular mechanism in relation to bone resorption is discussed.

Messenger function of prostaglandins in cell to cell interactions and control of proteinase activity in the rheumatoid joint

Destruction of joint structures in arthritis may result from failure of normal mechanisms controlling interactions among cells of the various tissues of the joint. Normal synovium in culture produces less prostaglandin E (PGE) and collagenase than rheumatoid. When rheumatoid synovium is dissociated into cells, the adherent cell cultures rapidly lose the ability to synthesize large amounts of PGE and collagenase and become indistinguishable from normal synovial cells. A mononuclear cell factor (MCF) derived from supernatant media of cultured human blood mononuclear cells and a 'synovial factor(s)' (SF) from cultures of either normal or rheumatoid synovial fragments both stimulate production of PGE and proteinase by cells derived from human synovium, cartilage and bone. The activities of factors which may be present in these stimulatory supernatants may be unmasked in vitro when they are removed from the normal control present in vivo. Normal synovium probably contains cells which, with the appropriate stimulus, may be recruited to participate in joint tissue degradation. Normal connective tissue turnover may also be controlled by a neutral metallo-proteinase inhibitor (TIMP), which is produced in considerable amounts by normal synovium, but which cannot be detected in cultures of rheumatoid synovium. While corticosteroids inhibit the production and action of MCF and SF, they stimulate production of TIMP by normal or rheumatoid synovial tissue in vitro and may contribute to the endogenous control mechanisms. PGE may also have a modulatory role in these cellular interactions.