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

The role of macrophages in the disappearance of Meckel's cartilage during mandibular development in mice

Meckel's cartilage is a supporting tissue in the embryonic mandible that disappears during development; however, the precise mechanisms of this disappearance process are still undetermined. In this study, we observed morphological changes of Meckel's cartilage with development and analyzed the factors which might be related to this process. Meckel's cartilage of ICR strain mice from 14 to 19 days gestation (E14-19) were used in this study. Histological and immunohistochemical studies indicated the decrease in the amount of sulfated glycoconjugates and the localization of type I collagen in the Meckel's cartilage matrix during development. Chondrocytes also expressed high acid phosphatase activities at these stages. An organ culture study indicated that Meckel's cartilage at E17 disappeared during the cultivation period, while the cartilage at E14 did not disappear. Massive penetration of macrophages into the perichondrium was detected at E16. RT-PCR analysis of Meckel's cartilage indicated the expression of interleukin-1β, type I collagen, MMP-9 at E17, but not at E14. MIP-1α, the candidate molecule for macrophage chemoattractant factor, was expressed at E14. These results indicated the dynamic matrix changes of Meckel's cartilage during development and suggested that the functional changes of chondrocytes in synthesis of type I collagen might be induced by interleukin-1β secreted by the penetrating macrophages.

Relationship of the plasminogen activator/plasmin cascade to osteoclast invasion and mineral resorption in explanted fetal metatarsal bones

An attempt was made to establish whether the activation of plasminogen into plasmin is necessary either for the preparatory phases to bone resorption, involving the recruitment of osteoclast precursors, their migration toward mineralized surfaces, and their final differentiation, or for the subsequent osteoclastic resorption phase. 45Ca-labeled fetal (17 day) mouse metatarsals were cultured under conditions in which they pursue their modeling for a few days. In this model, the resorption phase, monitored by the release of 45Ca into the medium, is entirely dependent on the preparatory phases affecting osteoclast precursors. It was, as expected, stimulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 and inhibited by calcitonin. PTH also enhanced the activity of tissue-type plasminogen activator (PA) in extracts of metatarsals but not that of urokinase (which is, however, the main PA present in the mouse fetal metatarsal culture model). The resorption processes were not dependent on the presence of plasminogen in the media, even when the rudiments were precultured with tranexamic acid to remove their endogenous plasminogen. Moreover, they were not influenced by inhibitors of plasmin, either the plasma inhibitors alpha 2-antiplasmin, alpha 2-macroglobulin, and alpha 1-antitrypsin, or aprotinin, which was tested under a variety of conditions. Aprotinin also did not influence the resorption (loss of calcium and hydroxyproline) of 19 day fetal mouse calvariae cultured with PTH in a medium devoid of plasminogen. It is concluded that the various steps implicated in the bone resorption processes that occur in the metatarsals and in the calvariae culture models are not dependent on the activity of plasmin. The function of PAs in bone, however, could be exerted through direct proteolysis of extracellular proteins other than plasminogen or be mediated by a molecular structural domain distinct from their catalytic domain.

The glycosaminoglycans in cultures of stimulated rat peritoneal macrophages. 2. Gel chromatographic studies and the behaviour of heparan sulfate

The molecular weight distribution of pMP-derived glycosaminoglycans (GAG), i.e. non-sulfated GAG, chondroitin sulfate (CS), and heparin sulfate (HS)-like material was determined. The peritoneal macrophages (pMP) were harvested from rats normal or stimulated by i.p. injection of thioglycolate, carrageenan or BCG, and maintained in culture. The GAG of cell layer and medium were isolated separately after labeling with 35S-sulfate and 3H-acetate. Treatment with nitrous acid served to remove HS-like material. Labeling with 3H-acetate served to detect synthesis of the high m. w. hyaluronic acid (HA). Gel chromatic separation was done using Sephadex G-200 columns. The maximal size of 35S-labeled GAG, especially HS (36 kDa), was reduced in cultural medium and cell layer after stimulation in vivo. Reduction was most pronounced after application of carrageenan followed by thioglycolate and BCG/LPS stimulation. The extracellular GAG of BCG-stimulated pMP were smallest, probably due to degradation. Heparan sulfate-like material made up a larger proportion in monolayer and medium, comprising the total m.w. range up to 36 kDa. The GAG sensitive to nitrous acid were maximal in cultures of carrageenan-stimulated pMP and minimal in those of thioglycolate-stimulated pMP. This type of HS was sensitive to hyaluronidase, too. Any synthesis of high molecular hyaluronic acid was not found in normal or stimulated rat pMP. Therefore MP-associated HA must be adsorbed from other sources or synthesized by early forms of macrophages.

Co-operation between interleukin-1 and the fibrinolytic system in the degradation of collagen by articular chondrocytes

1. The interaction between interleukin 1 (IL-1) and the fibrinolytic system in the control of collagen degradation by rabbit chondrocytes has been investigated in a tissue-culture system where cells are grown on a 14C-labelled collagen matrix. 2. Culture of rabbit chondrocytes in the presence of human recombinant IL-1 beta at a concentration of 57pM for 48 h led to the presence of procollagenase but not active collagenase in the medium. The latent collagenase could be activated by incubation with an organomercurial, aminophenylmercuric acetate (APMA). 3. Addition of IL-1 beta to chondrocytes grown on a 14C-labelled collagen matrix did not increase the degradation of the matrix compared to control over a 48 h period. However, in the presence of plasmin (200 micrograms ml-1) or plasminogen (100 micrograms ml-1), IL-1 beta (57 pM) caused almost complete degradation of the collagen matrix. Plasmin or plasminogen alone caused only slight degradation of the collagen matrix. 4. Tissue inhibitor of metalloproteinases (TIMP) or the selective metalloproteinase inhibitor, SC44463, inhibited the degradation induced by IL-1 beta and plasminogen in a concentration-related manner and at concentrations that were correlated with inhibition of collagenase. 5. When concentrations of IL-1 beta which caused only minimal degradation of the matrix in the presence of plasminogen were combined with fibrin (1 microgram ml-1), there was almost total degradation of the matrix by 48 h. 6. These results indicate there is a synergistic interaction between IL-1 and the fibrinolytic system in the degradation of collagen by rabbit chondrocytes in culture.

Modulation by interleukin 1 and tumor necrosis factor alpha of production of collagenase, tissue inhibitor of metalloproteinases and collagen types in differentiated and dedifferentiated articular chondrocytes

The actions of interleukin 1 (IL1) and tumor necrosis factor alpha (TNF alpha) on several parameters of the collagen metabolism of rabbit articular chondrocytes were studied by comparing the responses of either differentiated chondrocytes in primoculture or dedifferentiated cells in late passage culture to human recombinant (hr) IL1 alpha, hr-TNF alpha and cytokine-enriched fractions of rabbit macrophage-conditioned media. In response to IL1 or TNF alpha, differentiated chondrocytes (i.e., producing the cartilage-specific collagens, types II and XI, but no type I), sharply reduced their synthesis of collagen, a reduction which involved both types II and XI collagens, without consistently changing their production of non-collagenous proteins; they also incorporated a smaller proportion of collagen into the matrix. Similar levels of response were obtained for hr-IL1 alpha at picomolar and for hr-TNF alpha at nanomolar concentrations. However, the action of TNF alpha, but not of IL1, was manifested only in the presence of serum. Simultaneously, IL1, but not TNF alpha, induced the chondrocyte production of procollagenase (a difference which contrasted with the similar levels of procollagenase induced by both cytokines in synovial and skin fibroblasts) but neither cytokine influenced the accumulation of the collagenase inhibitor TIMP. These effects were not affected by indomethacin and are thus unlikely to be prostaglandin-mediated. During their dedifferentiation in monolayer subcultures, chondrocytes became more sensitive to the procollagenase-inducing ability of IL1 and TNF alpha, but their response to TNF alpha was lower than to IL1. They also increased their production of TIMP, which remained unaffected by the cytokines. Simultaneously, they decreased their production of collagen and substituted progressively the synthesis of fibroblast-specific collagens, types I, III and V, for types II and XI. Acting on dedifferentiated cells, even in the presence of indomethacin, IL1 and TNF alpha further decreased the synthesis of collagen, reducing the production of both typical type I (i.e. [alpha 1(I)]2 x alpha 2(I) molecules) and type V collagens as well as their incorporation into the matrix, but increasing the synthesis of type III collagen. Therefore not only IL1, but also TNF alpha can exert profound influences on the collagen degradation and repair processes occurring in the pathology of articular cartilage.

The enzymatic evaluation of procollagenase and collagenase inhibitors in crude biological media

The validity of the enzymatic assay of procollagenase within crude biological media containing also the collagenase inhibitor TIMP (tissue inhibitor of metalloproteinases) as well as other (pro)metalloproteinases and sometimes, metalloproteinase-TIMP complexes, has been reevaluated. To be enzymatically assayed, procollagenase has to be activated. The standard activation procedures by either trypsin or 4-aminophenylmercuric acetate (APMA) both allow an optimal recovery of collagenase from procollagenase when the media do not contain free TIMP. However, they do not destroy TIMP nor do they reactivate the collagenase present in enzyme-inhibitor complexes. Therefore, the collagenase formed by the activation of procollagenase in the presence of free TIMP is immediately inactivated by binding to the inhibitor. As a result, both the bound collagenase and TIMP can no longer be assayed by enzymatic methods. An optimal recovery of collagenase can, however, be obtained if free TIMP is neutralized by the binding of other tissue metalloproteinases (such as those present in culture media of rabbit bone marrow-derived macrophages) prior to the activation and assay of procollagenase. Similarly, it is possible to recover under an active free form a large part of the TIMP present in collagenase- (or other metalloproteinase-)TIMP complexes by heating the complexes at acid pH under conditions which inactivate the collagenase.

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.

Granulocyte elastase as a new biochemical marker in the diagnosis of chronic joint diseases

Human granulocyte elastase (EC 3.4.21.37) is released from granulocytes in large amounts in chronic inflammatory joint diseases and is therefore of special pathogenic and diagnostic importance. In order to examine the diagnostic significance of this enzyme as a clinico-chemical parameter, we determined the concentration of granulocyte elastase in complex with alpha 1-proteinase inhibitor by an enzyme immunoassay in synovial fluids and plasma of patients with chronic joint diseases. In inflammatory synovial fluids the concentration of complexed elastase correlates well with the granulocyte number and may increase to an extremely high level. In 90% of patients with manifest rheumatoid arthritis increased elastase levels are also observed in the plasma, probably due to the large gradient between the synovial fluid and plasma concentration, whereas in osteoarthrosis normal plasma concentrations were observed. Thus, these results indicate that normal plasma concentrations in patients with chronic joint diseases exclude the diagnosis of rheumatoid arthritis with high probability. The simultaneous determination of complexed elastase in plasma and synovial fluid improves the nosological differentiation of chronic joint diseases. Elastase activity on a specific chromogenic substrate, which was found in many inflammatory synovial fluids, is mainly attributed to elastase alpha 2-macroglobulin complexes. In some purulent synovial fluids, however, we were able to detect free elastase, which has been shown to play an important role in the destruction of articular cartilage.

Partial characterization of the macrophage factor that stimulates fibroblasts to produce collagenase and to degrade collagen

Rabbit bone marrow-derived macrophages in culture produce and release a soluble factor that activates collagenase secretion and collagen degradation by cultured skin fibroblasts from either rabbit, mouse or human origin. The factor is heat-labile and is inactivated by phenylglyoxal. After gel filtration, it is recovered in both an apparent high-Mr (67000-76000) and a low-Mr (9000-14000) form. Chromatography on cation exchangers suggests two molecular species with different charge properties. These characteristics are compatible with known properties of rabbit interleukin 1.