A new factor that may control collagen resorption

Tympanosclerosis

Tympanosclerosis is a disease which affects the tympanic membrane (TM) and middle ear. The locus for the essential pathology is in the connective tissue component of the drum which is the lamina propria. In the middle ear, the pathology is in the basement membrane. In the early stages there is a minimal involvement of the mesenchymal component, usually seen as a small white macula, or scar, in the drum. In advanced disease, the hyalinization of the mesenchymal component together with the attraction of the calcium ion leads to a thick, dense, calcified scar.

The theory of pathogenesis for this disease entity is that the connective tissue component of these structures is stimulated by infection, inflammation, or trauma involving some degree of local immunological hypersensitivity. With severe middle ear infection, the mucosa of the inner surface of the drum becomes permeable, and the ground substance of the lamina propria becomes edematous taking up water together with components of complement from the middle ear disease. The abnormal middle ear secretions contain the immunoglobulin components capable of participating in the process. If there is any damage to the connective tissue, the adsorption and repair permits the body to react immunologically against the destroyed tissue, thereby sensitizing this area.

Experiments were performed with the guinea pig in which the tympanic membrane was removed and the lamina propria isolated and prepared as an immunological antigen. When this material was injected into the rabbits, a high, satisfactory antiguinea pig tympanic membrane antibody was formed (anti-GPTM). It was then possible to remove this anti-GPTM antibody from the serum. The tissue specificity was determined by immunofluorescent staining which showed it to be adsorbed onto the TM, middle ear mucosa, as well as the basement membrane of the respiratory tract. The guinea pigs which were passively sensitized with anti-GPTM antiserum demonstrated the binding of the antibodies on the tympanic membrane when subject to trauma, infection, or cautery. The manifestation was in the anatomical area related to the injury. Complement fixation was, likewise, demonstrated.

Controlled animals which were not traumatized, or were not passively sensitized, included those which were injected with IgG from rabbits not sensitized against GPTM. They showed no fixation of antibody or complement in the TM. Following injury the antibody and complement bound to the TM provide the necessary elements for the subsequent immunopathologic disease entity known at tympanosclerosis.

The turnover and degradation of collagen

The interstitial collagens are degraded predominantly extracellularly, by specific collagenases (metalloproteinases) capable of cleaving the helical region across the three chains at a similar locus, solubilizing the cleaved products from the fibril. Other neutral proteinases may also function in this role by cleaving near cross-links in the fibril. Collagen type, molecular aggregation and small changes in temperature all markedly affect rates of collagenolysis in the fibril. Regulation of collagenolysis is also modulated at the levels of (1) cellular production of latent collagenase (procollagenase), (2) activation of latent collagenase, and (3) production of collagenase inhibitors. Fibroblastic cells and certain macrophages are probably the predominant sources of collagenases in inflammation; an enzyme in polymorphonuclear leucocytes (neutrophils) is distinct from the tissue enzyme. Molecules such as mononuclear cell factor (MCF), homologous with interleukin 1, which augment cellular collagenase production in inflammation, are derived from monocytes. The mechanisms of augmented collagenase production involve new protein synthesis and, if this augmentation is analogous to that produced by urate crystals, it is probably associated with increased levels of procollagenase mRNA. MCF production is itself controlled by products of lymphocytes as well as by interactions of monocytes with the Fc portion of immunoglobulins and components of the extracellular matrix. Activation of latent (pro)collagenase probably occurs in vivo through the action of neutral proteinases such as plasmin (through plasminogen activator). These effects may be indirect and exerted through proteolytic activation of a procollagenase activator. Tissue inhibitors act to regulate the active collagenase.

Radiographic findings in osteoarthritis of the knee joint are not correlated with cartilage histomorphology or immunohistochemistry

The purpose of this study was to investigate whether radiographic joint space narrowing (JSN) of the lateral knee compartment predicts the histomorphological or immunhistochemical grading in cases of osteoarthritis of the knee joint. The lateral joint space was measured on weight-bearing radiographs. Femoral osteochondral plugs of 29 patients undergoing total knee replacement were obtained from lateral condyles. All these patients had severe osteoarthritis of the medial compartment, with the lateral compartment showing different stages of osteoarthritis. The specimens were histomorphologically evaluated with the Mankin score, and the expression of the cartilage-degrading enzymes MMP1 and MMP3 was measured. There was no correlation between the joint space and histomorphological or immunohistochemical data, whereas the enzyme expression was correlated with histomorphological grading. We conclude that radiographic assessment alone is not sufficient to evaluate the cartilage damage of the lateral condyle.

Collagen loss in the stunned myocardium

BACKGROUND

This study was performed to biochemically assess and quantify the previously observed ultrastructural alterations in the collagen matrix of stunned myocardium.

METHODS AND RESULTS

The stunned myocardium was produced in 13 mongrel dogs by a series of 12 coronary artery occlusions of 5 minutes followed by 10-minute reperfusion periods, with a final reperfusion period of 90 minutes. Regional systolic function in the stunned myocardium was 17% of control. Relative end-diastolic length in the stunned region increased up to 8%. There was a nonuniform transmural loss of collagen. Hydroxyproline in the stunned endocardium was not different from control. The stunned midwall and epicardium demonstrated 12.5% (p less than 0.05) and 14.6% (p less than 0.005) decreases, respectively. All transmural layers in the stunned myocardium had significant increases in collagenase activity before procollagenase activation, averaging a 73.6% increase (p less than 0.025). Complete activation of all procollagenase forms with aminophenylmercuric acetate revealed no differences in fully activated collagenase between the stunned and normal regions. The lysosomal enzymes, elastase and cathepsin G, were not different between stunned and normal zone tissue. These results would tend to exclude exogenous sources of protease in the stunned myocardium at the 90-minute final reperfusion time frame. Collagen fibers were isolated from the stunned and normal zone tissue and underwent dansyl chloride reaction. Stunned collagen fibers had 9% greater dansyl labeling, suggesting greater numbers of exposed N-terminal amino acid residues on the fiber and compatible with greater enzymatic cleavage activity on the stunned collagen matrix. Tissue water content was consistently greater in the stunned region compared to the normal: a uniform transmural increase of approximately 1.7%.

CONCLUSIONS

The stunned myocardium is characterized by both systolic dysfunction and diastolic expansion or dilatation. Endogenous procollagenase is activated by the ischemic process leading to degradation of the extracellular matrix. The underlying mechanisms may be relevant in ischemic enlargement of the heart and cardiomyopathy.

Immunoelectron microscopic localization of collagenase inhibitor in bovine dentin

The localization of collagenase inhibitor in bovine dentin was investigated by immunohistochemistry and immunoelectron microscopy using a specific rabbit antiserum raised against the inhibitor purified from culture medium of bovine unerupted third molar pulps. Immunoreactive collagenase inhibitor was mainly localized as an amorphous or granular accumulation along the wall of dentinal tubules in decalcified bovine dentin. A part of the immunoreactive inhibitor appeared as two periodic bands on the collagen fibrils surrounding the dentinal tubules. Those two, a major and a minor band, corresponded to D-periodic fibril bands V-VII and I, respectively. As those two bands are located on both borders between overlap and hole zones of the collagen fibril, C- and N-terminal non-helical peptides and eight regions which are nD (n = 1-4) apart from each non-helical peptide along the triple helix are all equally possible binding sites of the collagenase inhibitor on the collagen molecule. It is interesting that the major band is located not exactly at, but fairly close to, the locus of collagenolytic cleavage, which lies between D-periodic fibril bands IV and V.

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

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

Tumor cell metastasis

Local tissue invasion and the formation of metastatic lesions are characteristic properties of many malignant tumors. The formation of metastases is a complex process involving the passage of tumor cells from the site of the primary bulk tumor through successive connective tissue barriers, ultimately resulting in the growth of secondary tumor cell colonies in distinct target organ locations. At many stages in the metastatic process, tumor cells interact with multiple components of the extracellular matrix. Recently, the importance of basement membrane as a barrier to invasive cells has been recognized. In the course of the transition from in situ to invasive carcinoma, normal or dysplastic epithelial cells residing on a basement membrane are replaced by neoplastic cells which subsequently invade the basement membrane and enter the underlying stroma. Once in the stroma, tumor cells can then penetrate the walls of blood vessels or the lymphatic system and enter into the circulation. Circulating tumor cells next arrest in the lumina of small vessels, invade the vessel wall, and leave the circulation. These cells are now directly exposed to the extracellular matrix of a target organ where they may grow to form secondary tumors. Throughout the metastatic process tumor cells are thus in contact with, and are potentially responsive to, various components of the extracellular matrix. This review provides a survey of the recent advances in our understanding of the interactions of metastatic tumor cells with the extracellular matrix. Specifically, the role of basement membrane as a barrier to metastatic tumor cells is examined.

Metalloproteinase inhibitors from bovine cartilage and body fluids

Inhibitors of the mammalian metalloproteinases, collagenase, proteoglycanase and gelatinase were isolated from bovine cartilage (extracts and culture medium) and bovine amniotic fluid and serum. These inhibitors either bind or do not bind to concanavalin-A--Sepharose, with Mr (gel filtration) of about 30 000 and 20 000, respectively. Cartilage and chondrocyte culture media contained only concanavalin-A-binding inhibitors whereas cartilage extracts contained only a non-binding inhibitor: serum and amniotic fluid contained both forms of inhibitory activities. In moist biochemical respects, particularly in their abilities to inhibit metalloproteinases, all of the inhibitors were found to be similar. It is concluded that the forms of the inhibitors that differ in Mr may be closely related to the tissue inhibitor of metalloproteinases (TIMP) previously purified from rabbit and human sources. These findings help to clarify other studies on collagenase inhibitors and support the concept that TIMP-like inhibitors may be important in the control of connective tissue degradation.

Mouse bone collagenase inhibitor: purification and partial characterization of the inhibitor from mouse calvaria cultures

The organ culture of neonatal mouse calvaria produced both collagenase and collagenase inhibitor. The inhibitor was purified by a series of column chromatographies: DEAE-cellulose and CM-cellulose ion-exchange chromatography, concanavalin A-Sepharose and heparin-Sepharose affinity chromatography, and finally by Sephacryl S-200 gel filtration. The purified inhibitor migrated as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had a molecular mass of 28,000. The inhibitor was purified 140-fold to a specific activity of 163 units/mg with a yield of 18% over the first step of the purification by DEAE-cellulose chromatography. The inhibitor stained positively for carbohydrate with periodic acid-Schiff's reagent indicating, in conjunction with its affinity to concanavalin A, that the inhibitor is a glycoprotein. In addition to mouse bone collagenase, this inhibitor also inhibited chick bone, rat bone, rabbit corneal, and human gingival collagenase, but did not inhibit bacterial collagenase.

The use of in vitro models for investigating the response of fibrous joints to tensile mechanical stress

To clarify the role of mechanical deformation in the remodeling of fibrous joints, organ culture systems have been developed to apply mechanical stress to cranial sutures under controlled experimental conditions. Tensile mechanical stress applied to cranial sutures from newborn rabbits produces a two- to threefold increase in protein synthesis and a twofold increase in collagen synthesis that can be detected within 6 hours. There is also a threefold increase in the DNA content of the sutures after 48 hours. Under normal conditions sutural fibroblasts synthesize type I collagen but respond to tensile deformation by synthesizing significant amounts of type III collagen. This suggests that the biomechanical environment of a connective tissue cell is an important determinant of the collagen type synthesized. However, the effect is likely to be an indirect one by virtue of its influence on the metabolic activity of the cells. Mechanically activated cells do not preferentially synthesize structural proteins, since mechanical stress stimulates the synthesis not only of structural macromolecules but also of the enzymes responsible for their specific hydrolysis. This is not accompanied by increased degradation, however, perhaps because the metalloproteinase inhibitor TIMP synthesized by the tissues is also increased. Confluent rabbit and mouse periosteal fibroblasts synthesize and release into the culture medium factors that can inhibit bone cell proliferation and stimulate bone resorption in vitro. It seems likely that further investigation of the interaction between fibroblasts and osteoblasts at the bone--fibrous tissue interface will require a reassessment of current thinking concerning the mechanisms regulating sutural osteogenesis.

The effects of razoxane (ICRF 159) on the production of collagenase and inhibitor (TIMP) by stimulated rabbit articular chondrocytes

Monolayer cultures of rabbit chondrocytes were stimulated to produce collagenase with conditioned medium from human peripheral blood mononuclear cells (MCM), and the ability of Razoxane to modulate the production of collagenase and specific tissue inhibitor of metalloproteinases (TIMP) was studied. Collagenase production was inhibited and TIMP increased by Razoxane, in a dose-dependent manner, when cells were treated daily for 3 days. Over this period the effect of Razoxane was progressive; 50 micrograms/ml or less had no effect at day 1 but 50 micrograms/ml was effective by day 3. The effectiveness of Razoxane was inversely related to the degree of MCM stimulation and the confluency of the culture. On removal of the drug, chondrocytes stimulated with MCM recovered their ability to produce collagenase, and TIMP production returned to near normal. The results suggest that the ability of Razoxane to reduce collagenase and increase TIMP production may correlate with its effectiveness in treating psoriatic arthritis.

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.

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.

Extraction of latent-type collagenase from cultured bovine dental pulps with NaCl or urea or by collagen degradation

All of the collagenase activity extracted from cultured bovine dental pulp tissue with NaCl or urea solutions was due to enzyme in a latent form and identified as a typical animal collagenase. Isotonic sucrose solution solubilized no detectable collagenase activity from cultured dental pulps. Also, no collagenase activity was extracted from either fresh bovine dental pulps or those cultured in Tyrode's solution containing 50 micrograms/ml cycloheximide. A two-day difference was observed between the appearance of collagenase activity in the cultured pulps and in the culture medium. The activity profiles in the culture media showed essentially no difference with or without the addition of cyclohexamide on and after the 10th day of culture, indicating that the biosynthesis of collagenase in the cultured pulp might have terminated around that time. About 80% of the total pulp collagenase activity was extracted by a bacterial collagenase procedure. Nearly half (43.5%) of the collagenase activity extracted from the cultured pulps with NaCl or urea solution was precipitated with collagen molecules in the presence NaCl, and most of the precipitated activity retained in the precipitate even after washing it with NaCl-buffer solution. These facts suggest a close association of collagenase with the collagen in cultured dental pulp tissue.

Enhanced breakdown of bovine articular cartilage proteoglycans by conditioned synovial medium. The effect of serum and dextran sulphate

Medium from cultured bovine synovial membrane when applied to articular cartilage from the same animal enhanced proteoglycan breakdown, as measured by the release of [35S]sulphate from prelabelled cartilage, principally by activating chondrocytes to secrete or activate their own enzymes. This effect persisted whether or not the synovium was cultured in medium containing fetal calf serum. The release of proteoglycans from cartilage was markedly enhanced when the synovium was cultured in the presence of dextran sulphate (200 micrograms/ml), while dextran sulphate had no effect upon cartilage alone or when added together with medium cultured in the absence of dextran sulphate. Since the release of the proteoglycan breakdown products from frozen and thawed cartilage was not stimulated by dextran sulphate, this agent appeared to be enhancing the indirect chondrocyte-mediated effect of synovial medium rather than the direct proteolytic enzyme-induced effect. A possible mechanism for the production of a substance responsible for the chondrocyte-mediated matrix degradation is proposed, involving monocyte-like or macrophage-like cells, either resident in the synovial tissue or derived from the circulation.

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.

Role of collagenases in tumor cell invasion

Collagenases are a family of metalloproteinases which may play a role in facilitating tumor cell invasion of the extracellular matrix. Tumor cells traverse two types of extracellular matrix: basement membranes and interstitial stroma, at multiple stages of the metastatic process. The matrix is a dense meshwork of collagen, proteoglycans, elastin and glycoproteins. Normally the matrix does not contain open spaces large enough for cell movement. Therefore numerous investigators have postulated that collagenolytic proteases, secreted by tumor cells or associated host cells, breakdown the extracellular matrix during tumor cell invasion. A large number of animal and human tumors have been shown to contain collagenase at a higher level than corresponding benign tissues. Separate collagenolytic metalloproteinases have been identified which degrade specific types of collagen. A basement membrane collagenolytic protease was shown to be elevated in a series of metastatic murine tumor cells. Immunologic studies using antibodies specific for collagenase have demonstrated that in vivo, tumor cells can produce collagenase. Therefore identification of collagenase in cultured lines of tumor cells is not an artifact of in vitro cultivation. In some cases, tumor cells may induce host cells to produce collagenase. The best evidence to date that collagenases actually play a role in invasion is derived from experiments in which natural collagenase inhibitors block tumor cell invasion of extracellular matrix in vitro.

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.

Purification of rabbit bone inhibitor of collagenase

1. Rabbit bones in tissue culture synthesize an inhibitor of collagenase during the first 4 days of culture. 2. The inhibitor was purified by a combination of gel filtration, concanavalin A--Sepharose chromatography, ion-exchange chromatography and zinc-chelate affinity chromatography. 3. The purified inhibitor migrated as a single band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and had a mol.wt. of 28000. 4. The inhibitor blocked the activity of the metalloproteinases collagenase, gelatinase, neutral proteinase III (proteoglycanase), human leucocyte collagenase and gelatinase, but not thermolysin or bacterial collagenase. The serine proteinases plasmin and trypsin were not inhibited. 5. The inhibitor interacted with purified rabbit bone collagenase with 1:1 stoichiometry. 6. The inhibitory activity was lost after incubation for 1 h at 90 degrees C, after treatment with trypsin (250 micrograms/ml) at 37 degrees C for 30 min and after reduction and alkylation.

An inhibitor of collagenase from human amniotic fluid. Purification, characterization and action on metalloproteinases

1. An inhibitor of collagenase of apparent mol.wt. 28000 was isolated from term human amniotic fluid. 2. It is active against mammalian collagenases from a number of species and tissues as well as other mammalian metalloproteinases, but has no activity against bacterial metalloproteinases. 3. Activity is destroyed by treatment with either trypsin or 4-aminophenylmercuric acetate, by heat, and by reduction and carboxymethylation. 4. All the properties observed suggest that it is similar to the synthesized tissue inhibitor of metalloproteinases.

Synthesis of a collagenase inhibitor by gingival fibroblasts in culture

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

Neutral proteinases from articular chondrocytes in culture. I. A latent collagenase that degrades human cartilage type II collagen

Culture media collected from secondary monolayer and spinner cultures of rabbit articular chondrocytes showed evidence of collagenolytic activity by the following criteria: (1) Amicon PM-10 concentrates of culture medium released [14C] glycine from reconstituted rabbit skin collagen fibrils at 37 degrees C; (2) medium concentrated by lyophilization decreased the relative viscosity of human cartilage collagen in solution. The loss in viscosity was partially inhibited if medium was preincubated with o-phenanthroline, and (3) degradation of human cartilage collagen after 60 h incubation at 24 degrees C was characterized primarily by the appearance of 75 000 dalton (TCA) and 25 000 dalton ((TCB) products. The majority of the collagenase (EC 3.4.24.3) from cultured chondrocytes was secreted in latent form, since preincubation with either trypsin or p-aminophenylmercuric acetate significantly increased activity against human cartilage collagen. Chondrocyte collagenase may be important in mediating the normal slow turnover of cartilage collagen and may be particularly active in collagen destruction associated with early stages of synovial joint arthritides, before attack by non-cartilage cells or extra-articular soft tissues.

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.

The latent collagenase and gelatinase of human polymorphonuclear neutrophil leucocytes

Two metallo-proteinases of human neutrophil leucocytes, collagenase and gelatinase, were studied. Collagenase specifically cleaved native collagen into the TCA and TCB fragments, whereas gelatinase degraded denatured collagen, i.e. gelatin, and the TCA fragments produced by collagenase. On subcellular fractionation by zonal sedimentation, collagenase was found to be localized in the specific granules, separate from gelatinase, which was recovered in smaller subcellular organelles known as C-particles. Neither enzyme was present in the azurophil granules, which contain the two major serine proteinases of neutrophils, elastase and cathepsin G. Collagenase and gelatinase were separated by gel filtration from extracts of partially purified granules. Both enzymes were found to occur in latent forms and were activated either by trypsin or by 4-aminophenylmercuric acetate. Gelatinase was also activated by cathepsin G, which, however, destroyed collagenase. Both enzymes were destroyed by neutrophil elastase. Activation resulted in a decrease by 25 000 in the apparent mol. wt. of both latent metallo-proteinases.

Identification of proteinases in rheumatoid synovium. Detection of leukocyte elastase cathepsin G and another serine proteinase

Extracts of rheumatoid synovial tissue obtained at surgical synovectomy contained neutral proteinases as well as cathepsin D. The neutral proteinase activity was particle-bound but could be solubilized by 1 M MgCl2. About half of the solubilized activity adsorbed to aproptinin-Sepharose at pH 7.5 and was desorbed at pH 3.3. This activity was shown to be due to leukocyte elastase and cathepsin G by enzymological and immunological criteria. The neutral proteinase activity that did not adsorb to aprotinin-Sepharose was not due to elastase or cathepsin G. It was able to hydrolyse proteoglycan and was inhibited by diisopropylfluorophosphate, soybean and lima bean trypsin inhibitors. It was, therefore, a serine proteinase. Its inhibition characteristics were different from those of plasmin, kallikrein or thrombin. All of the neutral proteinase activity of synovial extracts was attributable to serine proteinases, no evidence of metallo-proteinases was found. The possible role of the neutral proteinases in the degradation of the matrix of cartilage is discussed. A simple procedure for purifying leukocyte elastase and cathepsin G is described as well as the raising of specific antisera to these enzymes.

A latent collagenase from rheumatoid synovial fluid. Purification and partial characterization

1. A latent collagenase (EC 3.4.24.3) has been isolated from rheumatoid synovial fluids and purified by (NH4)2SO4 precipitation and column chromatography, utilising Sephadex G-150, DEAE Sephadex A-50 and Sephadex G-100 superfine grade. 2. The final preparation activated by trypsin (EC 3.4.21.4) had a specific activity against thermally reconstituted collagen fibrils of 259 micrograms collagen degraded/min per mg enzyme protein, representing a nearly 800-fold increase over that of the original rheumatoid synovial fluid. 3. The latent collagenase preparation can be activated by trypsin and to some extent by HgCl2 but not by 3 M NaSCN, 3.5 M NaCl, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) or p-chloromercuribenzoate. 4. Inhibition studies and the acrylamide gel electrophoretic pattern of collagen degradation products showed that the trypsin-activated enzyme has the essential features of a neutral collagenase. 5. The molecular weights, determined by calibrated gel filtration, were 52 000 and 43 000 for the latent and the activated enzyme, respectively. 6. The nature of the latency of synovial fluid collagenase is discussed.

The extraction of a neutral metalloproteinase from the involuting rat uterus, and its action on cartilage proteoglycan

1. Homogenates of rat uteri removed 1 and 2 days post partum were centrifuged at 6000 g. Both pellets and supernatants degraded Azocoll, a general proteinase substrate, at pH 7.5. More than 80% of the total activity was in the pellet fraction. 2. Part of the pellet activity was in a latent form. Trypsin and 4-aminophenylmercuric acetate (a thiol-blocking agent) both activated this latent form, indicating that it is an enzyme--inhibitor complex. An endogenous serine proteinase activated part of the latent enzyme during the assay. 3. The enzyme activity was low before parturition and after involution; it was highest during the first 2 days post partum, when the largest losses of uterine wet weight and matrix macromolecules occur. 4. Up to 70% of the enzyme in the pellets was extracted by heating at 60 degrees C for 4 min in 0.1 M-CaCl2/0.05 M-Tris/HCl, pH 7.5. Approx. 30% of the extracted enzyme was still latent. 5. The extracted enzyme was a metalloproteinase, since it was inhibited completely by 1,10-phenanthroline, but not by inhibitors of thiol or serine proteinases. 6. The enzyme was further purified 15--30-fold by gel chromatography and precipitation with (NH4)2SO4. The apparent molecular weight, estimated by gel filtration, was 24000 for the latent form and 12000 for the active form. The pH optimum was 7--7.5. 7. The enzyme also degraded cartilage proteoglycan. This activity was studied by viscometry and the products were analysed by analytical ultracentrifugation. The major product had a mol.wt. of approx. 100000. The sites of cleavage were in the protein core, since no free oligosaccharides were detected. 8. This neutral metalloproteinase is distinct from uterine collagenase and from a uterine metal-dependent endopeptidase that hydrolyses a heptapeptide related to collagen.

What controls collagen resorption in vivo?

The local control of collagen degradation in mammals in vivo is currently considered to depend primarily on variations on the level of activity of specific collagenases. Such variations are believed to depend on three factors: a) the rate of active collagenase synthesis and/or of activation of inactive enzyme precursors; b) the action of serum and/or tissue collagenase inhibitors; and c) different combinations of both mechanisms. We suggest that another element contributing to the regulation of collagen degradation in vivo is the susceptibility of the substrate. Support for this suggestion is derived from two sources: 1) experimental data, indicating that the rate of collagen degradation depends on the genetic type of substrate, on its state of aggregation (including degree of cross-linking), and on the nature and amount of other macromolecules associated with collagen in vivo. Other experimental findings supporting our hypothesis are the universal presence of collagen-bound collagenase, the apparent greater affinity of the enzyme for the more recently synthetized substrate molecules, and the increased amounts of intact collagen that may be solubilized from some tissues undergoing massive collagen degradation, 2) analogy with currently accepted views on intracellular protein catabolism, which cannot be rejected a priori as irrelevant to the problem.

Neuromuscular junction macromolecules in the pathogenesis of amyotrophic leteral sclerosis

An hypothesis regarding the pathogenesis of amyotrophic lateral sclerosis is presented, which places emphasis on extraneural cells. Classical experimental denervation is compared and contrasted with motor neuron disease, both from information in the literature as well as concepts deriving from the hypothesis. Background information regarding neuromuscular junction-specific (16S) acetylcholinesterase and a basal lamina-enriched surface glycoprotein (fibronectin) are presented, which suggest not only their mutual interaction, but likely parallel regulation on muscle cell surfaces by the motor nerve. Since 16S acetylcholinesterase likely contains basal lamina-type collagen and fibronectin specifically associates with collagen, a model relating activation of latent collagenase enzyme in amyotrophic lateral sclerosis is described. It is suggested that continued degeneration, including transneuronal effects, of the motor system ensues from random, continuous loss of nerve-muscle adherence resulting from collagen resorption at the neuromuscular junction.

Effect of tensile mechanical stress on the synthesis of metalloproteinases by rabbit coronal sutures in vitro

The application of a continuous tensile mechanical stress (30 g) to explants of coronal sutures from newborn rabbits (1-2 days) produced increases in enzyme activity of 33.7% for collagenase, 95.2% for gelatinase, and 35.9% for NMP III over a 4-day culture period. All three activities were in latent form and required activation with either 4-APMA or trypsin. The increases in enzyme activities were not accompanied by an alteration in the degradation of structural proteins. This was due to the ability of the cells to synthesize an inhibitor (mol wt 29,000 daltons) which complexed the increased quantities of enzyme. This necessitated a substantial stimulation of inhibitor production because there was still a residue of free inhibitory activity in the media of stressed cultures after 4 days. We previously showed using the same model system that coronal sutures respond to tensile mechanical stress by a two-fold increase in collagen synthesis. The present data suggest that when the priority of the cell population is the synthesis of structural proteins, the inhibitor, in addition to preventing the hydrolysis of newly synthesized peptides, also maintains matrix degradation at normal turnover levels.

A latent gelatin specific proteinase of human leucocytes and its activation

1. Gelatin specific proteinase (gelatinase) exists in human leucocytes extracts mainly in a latent form. 2. It is activated by different proteinases as well as by some chemicals (urea, NaSCN, HgCl2). 3. Non-proteolytic activation of latent gelatinase and the decreasing of its molecular weight associated with it strongly suggests that it is an enzyme-inhibitor complex.