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

Heberden Oration 1980: aspects of the cell biology of the rheumatoid synovial lesion

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Human mononuclear cell factors mediate cartilage matrix degradation through chondrocyte activation

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

Collagenase production by cloned populations of rabbit synovial fibroblasts

Monolayers of rabbit synovial fibroblasts treated experimentally with phorbol myristate acetate produce large amounts of collagenase and prostaglandin E2 and have been a suitable experimental model for the proliferative/destructive lesion of rheumatoid arthritis. We used X-irradiation to prolong the in vitro lifespan of these cells so that cloned populations could be studied. By a number of criteria, X-irradiation did not alter the cells to make them unrepresentative of synovial fibroblasts. With limiting dilution techniques, we simultaneously isolated three clones. These clones were shown to have different growth rates and to produce different amounts of collagenase and prostaglandin E2. Rates of protein synthesis, measured by incorporation of 3H-leucine, were similar for all three clones. Our data support the concept that particular populations of synovial cells may contribute selectively to the joint destruction seen in rheumatoid disease.

Stimulation of production of prostaglandin E in gingival cells exposed to products of human blood mononuclear cells

1. Supernatant media from cultures of unstimulated human peripheral blood mononuclear cells contained one or more factors that increased by several hundred-fold the production of prostaglandin E by fibroblast-like cells derived from both inflamed and normal human gingival tissue. 2. This stimulation occurred in a dose-dependent manner and was completely inhibited by 14 microM-indomethacin. 3. Responsiveness to the factor declined as the age of the cell culture increased. 4. An increase in prostaglandin E production was first observed after a 2h exposure to the mononuclear cell factor(s) and could be prevented by cycloheximide. 5. Brief exposure (0.5 and 1.0 h) to mononuclear cell factor did not increase prostaglandin E production by the cells in a subsequent 72 h incubation in the absence of mononuclear cell factor. 6. Addition of arachidonate (10 microM and 15 microM) further enhanced stimulation of prostaglandin E production in response to mononuclear cell factor. 7. The stimulatory activity was resistant to digestion by trypsin, but was heat-labile, so that only 17% remained after treatment at 56 degrees C for 30 min.

Polymorphonuclear granulocytes in rheumatic tissue destruction. III. an electron microscopic study of PMNs at the pannus-cartilage junction in rheumatoid arthritis

Metatarsophalangeal and metacarpophalangeal joints from 3 patients with rheumatoid arthritis were investigated electron microscopically with regard to the occurrence of polymorphonuclear granulocytes (PMNs) at the pannus-cartilage junction. In all 3 cases PMNs could be detected at the junction and within the cartilaginous matrix. PMN cytoplasmic processes surrounded collagenous islands in the cartilage. From the morphological findings it is deduced that PMNs are cells capable of destroying cartilage in inflammatory joint diseases, in particular in rheumatoid arthritis.

Enhanced neutral protease activity in proliferating rheumatoid synovial cells

Proteolytic enzymes associated with rheumatoid synovial cells (RSC) have been implicated in the degradation of articular cartilage. Proteases have been measured in proliferating rheumatoid synovial cells (P-RSC), proliferating nonrheumatoid synovial cells (P-NSC), and their nonproliferating counterparts (NP-RSC and NP-NSC). The P-RSC and P-NSC exhibit enhanced total surface-associated plus secreted neutral protease activity, as compared with NP-RSC and NP-NSC. The P-RSC exhibited significantly higher protease activity in this category compared to P-NSC. The RSC also secreted higher levels of secreted proteases alone compared to NSC. The secreted protease activity alone was not related to the proliferative state of the cells. Extractable protease activity was measured in early-passaged and serially-passaged P-RSC, NP-RSC, P-NSC, and NP-NSC. Extractable cellular protease activity measured at pH ranges from 5.0 through 8.0 was not significantly different between P-RSC and NP-RSC or between P-NSC and NP-NSC. The RSC contained elevated extractable cellular protease activity measured at pH ranges from 5.0 through 8.0 compared to extracts from later-passaged cells. The neutral protease activity in the early-passaged RSC was also higher than that measured at pH 6.0 or 8.0. In synovial cells cellular protease activity was related to the proliferative state and the origin of the cells. The P-RSC exhibited the highest levels of surface associated plus secreted neutral protease activity. The RSC also possessed the highest levels of extractable protease activity compared to NSC.

Granuloma collagenase and EDTA-sensitive neutral protease production in hepatic murine schistosomiasis

Mice infected with Schistosoma mansoni represent a model for study of hepatic fibrosis in humans. Production of trypsin-activatable inactive collagenase and EDTA-sensitive neutral protease was measured in the culture medium in which granuloma explants or primary cultures were maintained. Collagenase production was maximal in granulomas obtained from liver of mice 8 weeks postinfection and was inhibited by Actinomycin D or cycloheximide, and enhanced by lymphocyte factor(s) or heparin. Isolated schistosome eggs did not release these enzymatic activities but did release EDTA-insensitive protease activity. Both enzymes were separated by ion-exchange chromatography and purified to homogeneity. Isolated collagenase had an isoelectric point of 6.2 and molecular weight of 60,000 and had the functional characteristics of a tissue collagenase. The specific activity of collagenase was 33 units per mg protein at an optimum pH 7.5 and lacked proteolytic activity against noncollagenous protein substrates. Isolated EDTA-sensitive neutral protease had specific caseinolytic activity of 150 units per mg protein and gelatinolytic activity of 300 units per mg protein at an optimum pH 7.5; the enzyme lacked activity against undenatured collagen. Isoelectric point was pH 6.0. Protease activity was inhibited by known inhibitors of collagenases. Production and activation of EDTA-sensitive neutral protease and collagenase accompany increased collagen synthesis and content in the liver of mice 8 weeks postinfection with S. mansoni cercariae. Continued accumulation of liver collagen under these conditions suggests an insufficiency in collagenase activity relative to the increase in collagen synthesis.

Stimulation of rheumatoid synovial cell collagenase and prostaglandin production by partially purified lymphocyte-activating factor (interleukin 1)

Human macrophages produce in culture a factor termed mononuclear cell factor (MCF) that increases the production of collagenase and prostaglandins by isolated adherent rheumatoid synovial cells. A factor with similar biologic activity is also produced by the murine macrophage cell line P388D1. By using a sequential purification scheme involving ammonium sulfate fractionation; chromatography on DEAE-cellulose, Sephacryl S-200, and phenyl-Sepharose; and discontinuous polyacrylamide gel electrophoresis, the P388D1 cell-derived, synovial cell-stimulating factor was copurified with the lymphocyte-activating factor [LAF; interleukin 1 (IL 1)]. The specific activity of the partially purified LAF (IL 1) was approximately 15,000-fold higher than that of the LAF (IL 1) in the original P388D1 cell culture supernatant. On the basis of (i) the copurification of the P388D1 cell-derived LAF (IL 1) and synovial cell-stimulating factors; (ii) the similarity in cell of origin, molecular weight, and phenylglyoxal sensitivity of human MCF and murine LAF (IL 1); and (iii) the presence of LAF (IL 1) activity in preparations of partially purified human MCF, we have postulated that LAF (IL 1) may have effects on cell targets that are nonlymphoid in nature and also that human MCF may be similar to, or identical with human LAF (IL 1). The results of these studies have raised the possibility that LAF (IL 1) may play a role in macrophage-mediated activation of synovial cells and lymphocytes which are involved in the inflammatory responses associated with rheumatoid arthritis.

Lysosomal elastase: effect on mechanical and biochemical properties of normal cartilage, inhibition by polysulfonated glycosaminoglycan, and binding to chondrocytes

Rheumatic joint destruction usually starts with the destabilisation of cartilage. Lysosomal elastase is a candidate effector of this process, since this enzyme is found at the site of cartilage erosion by rheumatoid synovial tissue. In order to prove this hypothesis we assessed the mechanical stability of cartilage during treatment by this enzyme in vitro. An indentation apparatus was used for this purpose and biochemical as well as microscopic techniques were used to supplement the results thus obtained. Our findings show that elastase irreversibly impairs the stability of cartilage by lysis of matrix proteoglycans without the help of additive enzymes. Collagen fragmentation played no significant role during elastase-induced destabilisation, while specific collagenase attacked the collagen network within the matrix only subsequent to the removal of proteoglycans. These findings suggest that elastase is a leading enzyme during proteolytic cartilage degradation. In addition polysulfonated glycosaminoglycan was found to reduce the mechanical effect of elastase on normal cartilage. It is therefore concluded that local inhibition of elastase promises therapeutic benefit during rheumatic cartilage degradation. Upon treatment of cartilage with elastase we observed this enzyme not only within the matrix under destruction but also bound to chondrocytes. These findings support the hypothesis that elastase plays a role on the matrix not only by direct degradation, but also by an indirect effect mediated through living chondrocytes.

The production in culture of metalloproteinases and an inhibitor by joint tissues from normal rabbits, and from rabbits with a model arthritis. I. Synovium

During 5 days of culture, explants of normal rabbit synovium produced no active collagenase, negligible latent collagenase, but significant levels of free collagenase inhibitor. Synovium from joints exhibiting a proliferative arthritis produced greatly elevated levels of collagenase; the appearance of active enzyme in the medium during the second day of culture was associated with the disappearance of free inhibitor. Enzyme levels in the media correlated well with the arthritic status of joints, when explants were prepared up to 10 weeks after the induction of the model arthritis. Synovium from the contralateral joints of rabbits with unilaterally induced arthritis produced no active collagenase, but approximately one-third as much latent collagenase as found with arthritic joints. Enzymatic activities against gelatin and cartilage proteoglycan substrates were demonstrated in synovial culture media in addition to collagenolytic activity. Gel filtration showed that these activities were not due to a single enzyme, and further characterisation confirmed that the enzymes were metalloproteinases. The results are considered in the light of published data, and the involvement of metalloproteinases and their specific inhibitor in the development of arthritic lesions is discussed.

Cell-to-cell interactions in the secretion of enzymes of connective tissue breakdown, collagenase and proteoglycan-degrading neutral proteases. A review

Cell and tissue culture techniques provide valuable tools for investigating cell-to-cell interactions leading to the secretion of connective-tissue degrading enzymes, collagenase and proteoglycan-degrading neutral proteases, in inflammatory situations. These interactions, which might constitute a major regulatory mechanism, are reviewed here. Taken together, the available data strongly suggest that fibroblasts and related mesenchymal cells (such as chondrocytes, fibroblast-like or type B synovial lining cells, corneal stromal cells, etc.) could be the main suppliers of collagenase within tissues. These cells can secrete collagenase in response to factors produced by other cells, mainly macrophages and related cells (monocytes, synovial cells - presumably the macrophage like, type A synovial lining cells), possibly also epithelial cells. Lymphocytes are able to modulate factor production by macrophages so that, through the macrophage link the secretory behavior of the fibroblastic cells may be under the control of the immune defense system and serve as an effector of immune reactions leading to connective tissue destruction.

Regulation of stromal cell collagenase production in adult rabbit cornea: in vitro stimulation and inhibition by epithelial cell products

Media conditioned by epithelial cells from the adult rabbit cornea were capable of both stimulating and inhibiting production of latent collagenase by stromal cells from the same source. Cytochalasin B was required in this in vitro system for both secretion of stimulators by epithelial cells and production of collagenase by stromal cells in response. Optimal production of collagenase by stromal cells in response. Optimal production of stimulators occurred in low-density epithelial cell cultures. Chromatographed conditioned medium from such cultures contained three stimulator fractions with apparent molecular weights of 19,000, 54,000, and greater than or equal to 90,000. High-density epithelial cell cultures secreted inhibitors of stromal cell collagenase production with apparent molecular weights of 7000 and 19,000. Cytochalasin B was not required for production of inhibitors. Inhibitory conditioned medium blocked the effect of the 19,000-dalton and 54,000-dalton stimulator on stromal cells. The data suggest that epithelial cells, in ways depending on their density, may modulate collagen degradation in the integument.

Absence of immunoglobulins in rheumatoid cartilage-pannus junctions

Immune complexes (IC) present in the superficial region of rheumatoid articular cartilage may be an important factor in the invasion of the cartilage by pannus. The presence of such IC at the cartilage-pannus junction in rheumatoid articular cartilage invaded by pannus was investigated by using immunoelectron microscopy with horseradish peroxidase anti-human immunoglobulin (Ig). It was observed that, although the pannus-free surface of the cartilage contained easily detectable deposits of Ig, the areas covered by pannus failed to show any Ig in the 5 5 patients studied. This was true even in areas immediately adjacent to the advancing edge of the pannus which presumably had only recently been invaded by the granulation tissue. These results were confirmed by fluorescent antibody ultraviolet microscopy. It was concluded that rheumatoid pannus invasion of the free cartilage surface containing trapped IC results in the disappearance of such complexes.

Cell-mediated immunity to collagen and collagen alpha chains in rheumatoid arthritis and other rheumatic diseases

Peripheral blood mononuclear cells from patients with rheumatoid arthritis, gout, ankylosing spondylitis and degenerative joint disease were cultured in the presence of native types I, II and III collagens and alpha chains from each of these types of collagen. The culture supernatant fluids were harvested and assayed for lymphocyte-derived chemotatic factor for monocytes. Reactions to one or more of the native collagens was found in 50 per cent (10 of 20) of the patients with rheumatoid arthritis, 20 per cent (two of 10) of the patients with gout and ankylosing spondylitis but in none of the 10 patients with degenerative joint disease or in normal subjects. Reaction to one or more alpha chains was found in 90 per cent (18 of 20) of the patients with rheumatoid arthritis, 60 per cent (six of 10) of the patients with gout, 50 per cent (five of 10) of the patients with ankylosing spondylitis, 30 per cent (three of 10) of the patients with degenerative joint disease and in 10 per cent of the normal subjects (one of 10). All the reactions were quantiatively stronger in patients with rheumatoid arthritis. These results indicate that patients with rheumatoid arthritis have cell-mediated immunity to homologous native and denatured collagens but that the reaction is not specific for rheumatoid arthritis. Some patients with gout, ankylosing spondylitis and degenerative joint disease also have low levels of immunity.

Synovial fluid beta 2 microglobulin and hydroxyproline fractions in rheumatoid arthritis and nonautoimmune arthropathies

Fourteen patients with classical and definite seropositive rheumatoid arthritis (RA), 5 patients with microcrystalline arthritis, and 7 patients with osteoarthrosis were studied with respect to markers of newly synthesised collagen (synovial NDOH pro levels); markers of connective tissue resorption (synovial DOH pro and NBH levels); markers of lymphoid tissue activity (synovial and plasma beta 2m levels). Higher amounts of NDOH pro in RA synovial fluid are compatible with the hypothesis of a local connective tissue production as suggested by Uitto et al. on basis of a higher protocollagen proline hydroxylase activity in RA synovial tissue. DOH pro and NBH do not differ significantly in synovial fluid from RA or gouty patients, but the correlations between these forms of OH pro and, respectively, synovial lymphocytes and polymorphonuclear leucocytes are indicative of different processes of connective tissue remodelling in the 2 conditions. Synovial beta 2m levels are a direct function of total synovial lymphocyte counts independently of the type of arthropathy being explored. The ratio of synovial to plasma beta 2m is systematically above unity in RA patients only.

Macrophage factor that induces neutral protease secretion by normal rabbit chondrocytes. Studies of some properties and effects on metabolism of chondrocytes

Normal rabbit-articular chondrocytes secrete very small amounts of degradative enzymes in culture. Rabbit peritoneal macrophages, when activated with lipopolysaccharides, release a factor in the medium which stimulates the chondrocytes to produce significantly high levels of collagenase and other neutral protease for 2-3 days. The soluble mediator from macrophages appears to be a polypeptide with a molecular weight of 13000-15000 and can be inactivated by short-term treatment with trypsin or pronase. The enzyme-synthesis by chondrocytes can be stimulated to the same extent by repeated addition of the macrophage-medium. The metabolism of chondrocytes is altered due to the presence of this mediator. The cellular proliferation is diminished, while the rates of degradation as well as biosynthesis of the matrix are increased. These studies suggest the possibility that in the conditions such as osteoarthritis, where the synovial cells may not play an active role in cartilage degradation, the proteases can be produced by the cartilage cells themselves after the stimulation by macrophage-derived mediators. These intrinsic enzymes may be responsible for the slow, but progressive degeneration of cartilage tissue.

Mononuclear cell modulation of connective tissue function: suppression of fibroblast growth by stimulation of endogenous prostaglandin production

The role of immune cell products in modulating connective tissue metabolism was investigated. Supernates of both unstimulated and phytohemagglutinin-stimulated human mononuclear cell cultures suppressed fibroblast proliferation (up to 90%) and concomintantly stimulated fibroblast prostaglandin E(PGE) synthesis (20- to 70-fold). The growth suppression was, at least in part, a secondary result of the increased fibroblast PGE synthesis; growth suppression (a) paralled the increased fibroblast PGE synthesis, (b) was reversed by addition of inhibitors of prostaglandin synthesis (indomethacin, meclofenamate, and eicostaetraynoic acid), and (c) was reproduced by addition of exogenous PGE2 to fibroblast cultures. The prostaglandin-stimulatory, growth-suppressive activity was a product of non-T-lymphocyte, adherent cells and was present within 6 h of mononuclear cell culture. The activity was heat (56 degrees C) and trypsin sensitive, nondialyzable, and appeared in the 12,000-20,000 mol wt fractions by Sephadex G-100 chromatography. The activity in supernates of mononuclear cell cultures was removed by incubation with fibroblasts but not by similar incubation with peripheral blood mononuclear cells. Mononuclear cells release a factor(s) which modulates fibroblast proliferation by altering prostaglandin metabolism.

Stimulation of collagenase production by collagen in mammalian cell cultures

In this study, we investigated the possible regulatory role of collagen in collagenase production by cultured human skin fibroblasts and human and rabbit synovial cells. Addition of types I, II or III collagen in solution to the culture media markedly stimulated trypsin-activable collagenase activity in these cultures. In the human cell cultures the stimulatory effect of collagen was further enhanced by a soluble factor isolated from human monocyte culture media (Dayer, Russell and Krane, 1977). Both native and denatured forms of collagen stimulated enzyme production; their relative efficacy varied among the different types. The native form of both types I and II collagen showed a greater effect on collagenase production than the corresponding denatured form, whereas with type III collagen the denatured form was more effective.

Collagenase production by synovial fibroblasts treated with phorbol myristate acetate

A series of intracellular events occurring after treatment of rabbit synovial fibroblasts with 0.01 micrograms/ml phorbol myristate acetate (PMA) were measured. Ten minutes after addition of PMA, there was a temporary increase in intracellular cyclic AMP levels, followed by a transient decrease in incorporation of 3H-thymidine into DNA. Approximately 500 ng/mg cell protein of PGE2 were found in culture medium from the 12- to 24-hour incubation period, but significant collagenase was not detectable until 24 to 36 hours. Treatment with aspirin or indomethacin abolished PGE2 production but did not affect collagenase levels. Production of enzyme was associated with a cessation of cell proliferation, measured by protein content/culture and cell number. No enzyme was detectable in untreated cultures. Synovial fibroblasts treated with phorbol myristate acetate may provide a good model for studies on the mechanism of induction of collagenase production.

Environmental pH modulation of collagenase in normal human fibroblast cultures

Normal human skin fibroblast cultures have been used to assess the effects of relatively minor changes in environmental pH on collagenase, a major extracellular gene product. Collagenase accumulation in the culture medium, measured both as enzyme activity and immunoreactive material, was 2- to 10-fold greater at pH 7.6--8.2 than at pH 6.8--7.2. The pH-associated increase in collagenase was paralleled by an increase in general protein synthesis. Nevertheless, prototypic lysosomal and cytoplasmic enzymes changed very little under identical culturing conditions. Although substantial intracellular protein degradation occurred at all pH values, the small differences either in general protein degradation or in specific collagenase degradation in the medium were of insufficient magnitude to account for the increased accumulation of collagenase.

Morphology of osteoclasts in resorbing fetal rat bone explants: effects of PTH and AIF in vitro

Osteoclastic bone resorption was studied using 45Ca-labeled fetal rat bones cultured in the presence of parathyroid hormone (PTH) and an anti-invasion factor (AIF) derived from bovine hyaline cartilage which is enriched in a collagenase inhibitor. The specific morphological expressions of osteoclasts cultured in PTH and AIF were observed in both light and electron microscopy and analyzed cytometrically. Stimulation of bone resorption with PTH revealed significant increases in the numbers and activity of osteoclasts, whereas bones cultured in the presence of AIF showed significant decreases in numbers of osteoclasts and altered cell features including the loss of osteoclast contact with bone surfaces. These structural modifications were evaluated with 45Ca release data derived from matched-pair explants of fetal rat bones, revealing the existence of a relationship between resorptive states of the cultured bones and morphological expressions of osteoclastic activity.

Effects of D-penicillamine on lymphocyte modulation of synovial collagenase production

While D-Penicillamine is effective in the treatment of rheumatoid arthritis, its mechanism of action is unknown. In this study, effects of D-Penicillamine on collagenase production by adherent rheumatoid synovial cells were investigated. D-Penicillamine did not directly affect the synovial collagenase production. However, lymphocyte-free-supernatant (LFS) recovered from lymphocytes exposed to D-Penicillamine in vivo and in vitro significantly reduced collagenase production by adherent synovial cells. LFS from lymphocytes of normal subjects and from non-D-Penicillamine treated rheumatoid patients stimulated collagenase production. These investigations indicate that D-Pencillamine indirectly affects collagenase production by cultured synovial cells and suggests beneficial effects on controlling the primary disease process.

Collagenase production by rheumatoid synovial cells: morphological and immunohistochemical studies of the dendritic cell

The dendritic cells of dissociated, adherent rheumatoid synovial cell cultures are recognised by their distinctive morphological features--compact cytoplasm around the nucleus and long, branched cytoplasmic extensions. Such cells usually composed approximately 10% of the total adherent cell population but could vary from as few as 2% to as many as 40% with different synovial specimens. Histological studies have shown the cells to contain many mitochondria and large, spherical cytoplasmic inclusions which often distort the dendritic extensions. Although lysosomes were observed, no evidence for phagocytic activity was obtained. Immunolocalisation studies by means of a monospecific antibody to human collagenase have shown that the dendritic cell attached to a collagenous substratum produces and releases this enzyme in vitro. In contrast collagenase was detected in only a few of the fibroblast- and macrophage-like cells, and it was always intracellular. It is proposed that the dendritic cell may have an important role in the pathophysiology of the rheumatoid joint, particularly with regard to collagenase-mediated cartilage destruction.

Regulation of corneal collagenase production: stimulation of serially passaged stromal cells by blood mononuclear cells

After three or more passages, stromal cell outgrowths from explants of normal rabbit corneas and from corneas previously burned with alkali did not produce collagenase until they were stimulated by the addition of rabbit blood-derived mononuclear cells or media conditioned by them. Normal stromal cells required stimulation by lymphocytes or their products from alkali-burned animals, whereas those from alkali-burned corneas were stimulated by lymphocytes from either normal or alkali-burned rabbits.

Lymphocytes from synovial tissue of a boy with X-linked hypogammaglobulinemia and chronic polyarthritis

Lymphocytes were eluted from synovial tissue of a boy with X-linked hypogammaglobulinemia and chronic polyarthritis. The cell suspension contained 53% lymphocytes and 28% peroxidase-positive, macrophagelike cells, No B lymphocytes, 83% T lymphocytes, and 10% Fc-receptor-bearing lymphocytes were detected. Lymphocyte transformation was induced by polyclonal mitogens (phytohemagglutinin and pokeweed mitogen) whereas no response to antigens (purified protein derivative and Candida albicans antigen) was obtained. The eluted cells displayed antibody-dependent cytotoxicity.

Synovial fluid and serum hydroxyproline fractions in rheumatoid arthritis

In rheumatoid arthritis (RA) the synovial fluid lymphocyte count closely parallels the synovial fluid dialysable hydroxyproline, a marker of collagen resorption. This observation stresses the primordial role of lymphocytes in RA joint injury. The actual and eventually potential destruction of any single joint, as expressed by synovial fluid dialysable hydroxyproline levels, seems to reflect the general picture of disease activity as evaluated by the number of active joints (joint count), ESR and rheumatoid factor titres (latex fixation). Although urinary hydroxyproline levels are generally within the normal range in RA, they can be used as index of articular tissue destruction and as a parameter of overall disease activity when groups of patients are studied longitudinally in detail. The present study sheds no further light on the significance of synovial fluid and blood non-dialysable hydroxyproline levels.

Collagen production by cultures containing multinucleated cells derived from synovial fibroblasts

Multinucleate cells are found frequently in rheumatoid synovium. In this study, polyethylene glycol was used to fuse rabbit synovial fibroblasts. Approximately 40% of the cells developed more than one nucleus in a 24 hour period, during which time cell membranes had increased permeability. In cultures containing multinucleate cells, 3H-thymidine incorporation was depressed for 24 hours although 3H-leucine incorporation into TCA precipitable material was unaffected; autoradiography showed that depression of 3H-thymidine continued for at least 4 days. Collagenase production by cultures containing fused cells was increased more than 10-fold over control cultures during a 28 day period.

Collagenase immunolocalization in cultures of rheumatoid synovial cells

Cultures of rheumatoid synovial cells that have been enzymatically dissociated and are adherent to a culture vessel are morphologically heterogeneous. When these cells are cultured on a collagenous substrate for 2 to 6 days at 37 degrees C in serum-free medium, they produce collagenase. A monospecific antibody to human collagenase has localized the enzyme extracellularly around cytoplasmic extensions of dendritic cells and intracellularly within a few macrophage-like and fibroblast-like cells.

Cellular control of collagen breakdown in rheumatoid arthritis

Remodelling of connective tissue and its destruction in rheumatoid arthritis is related to collagenolysis. Study of collagenase released by rheumatoid synovial cels has indicated that the enzyme is released as latent form from adherent synovial cells in culture. As a latent enzyme it is protected from complexing with alpha2 macroglobulin, the principal proteinase inhibitor. Activation in vivo is very likely caused by proteases which destroy or complex with a portion of collagenase responsible for its latency. Recent data suggest that the latent collagenase is an enzyme-inhibitor complex and not a true zymogen.