Native cross-links in collagen fibrils induce resistance to human synovial collagenase

Avian tibial dyschondroplasia: a morphological and biochemical review of the growth plate lesion and its causes

Avian tibial dyschondroplasia is a disease found in fast growing strains of chickens, ducks, and turkeys worldwide in which growth plate cartilage accumulates in the metaphyseal region of the tibiotarsus; it is similar to mammalian osteochondrosis. Several biochemical and pathologic studies have shown that the growth plate chondrocytes do not reach their expected size in the hypertrophic zone and necroses prematurely. The chondrocytes also produce decreased amounts of extracellular proteins, such as collagen X and fibroblast growth factor-beta, that are necessary for cartilage maturation. This immature cartilage becomes highly cross-linked in the collagen molecules and apparently resistant to resorption and vascularization by the metaphyseal vessels. The dyschondroplastic cartilage remains in the metaphysis for several weeks. Not until the growth rate of the birds slows down is the cartilage able to be resorbed and replaced by trabecular bone. Many conditions have been found to induce tibial dyschondroplasia, including copper deficiency; fusarochromanone, thiram, and antabuse intoxication; excessive dietary levels of cysteine and homocysteine; metabolic acidosis; and bird rearing environment. However, the mechanism(s) by which these various methods induce tibial dyschondroplasia is presently not known. Current research is focusing on understanding the development of the disease and whether or not all these methods work by the same physiological chain of events. Recent biochemical evidence suggests that a copper deficiency might be caused by a different mechanism than genetically and thiram-induced tibial dyschondroplasia.

Factors influencing growth plate cartilage turnover

A number of nutrients and chemicals have now been identified as consistent inducers of tibia dyschondroplasia (TD). Thiram, Antabuse, and fusarochromanone induce TD when fed at 30 to 75 ppm. Cysteine, cystine, homocysteine, and histidine induced TD when fed at .5 to 3% of the diet. Cation: anion imbalances resulting in acidotic diets also induced TD. Even though prevention of TD induced by these chemicals and nutrients has been established, reversal of the spontaneous TD lesion has not been clearly demonstrated. Thus, the etiology of the spontaneous lesion awaits elucidation. These model systems all suggest that TD is the result of decreased growth plate cartilage degradation. Recent work has shown that increased collagen cross-links in the accumulated cartilage, which makes collagen less susceptible to degradation. Cysteine-induced TD seems to decrease growth plate collagenase activity and production. A role of growth plate macrophages in paracrine signaling of collagenase production by chondrocytes has been presented.

The rates of cleavage of insoluble and soluble collagens by tissue collagenases

The cleavage rates of insoluble and acid-soluble bovine collagens by tissue collagenases from the cultures of C3H mouse mammary adenocarcinoma and from human rheumatoid synovial fibroblasts at 37 degrees C were compared by measuring dansyl (Dns)-IIe and Dns-Leu, amino-terminal residues at the cleaved sites after dansylation. The kinetic parameters, Kcat and Km, defined functionally, were as follows: for insoluble Achilles tendon collagen, Km values were 0.89 and 0.83 microM; Kcat/Km 39.2 and 317 microM-1 h-1. For acid-soluble skin collagen the values were 0.83 and 0.82 microM; 44.6 and 354 microM, respectively. The supernatants from the insoluble and acid-soluble collagens contained 28% and 92% of total Dns-IIe and 1.3% and 43% of total Hyp, respectively. Results showed that both tissue collagenases cleaved insoluble collagen almost as rapidly as they did reconstituted collagen fibrils. The cleavage of collagen was proportional to enzyme concentration. The presence of Dns-IIe and Dns-Leu in the supernatant arises from a second cleavage of the collagen molecule.

Glucose and glucose analogs modulate collagen metabolism

Patients with diabetes often develop complications involving collagen-containing connective tissues. Previous in vitro studies have demonstrated that glucose inhibits collagen fibril formation and subsequent cross-linking. Collagen with diminished cross-linking is more susceptible to collagenolytic degradation. This may underlie the decreased collagen levels. To test this hypothesis, D-glucose and its two analogs, L-glucose and 2-deoxy-D-glucose, were used in chick calvaria organ cultures to examine parameters of collagen metabolism. L-Glucose is not used by the cell and functions as an extracellular glucose-like molecule, while 2-deoxy-D-glucose inhibits normal D-glucose uptake by blockading the glucose transport mechanism. Each of these three sugars had the ability to inhibit collagen fibril formation. D-Glucose stimulated collagen synthesis; L-glucose had no effect; and deoxyglucose inhibited collagen synthesis. D-Glucose was able to reverse the inhibitory effect of deoxyglucose. D-Glucose did not change levels of degradation of newly synthesized collagen while both L-glucose and deoxyglucose stimulated collagen degradation. When glucose transport was inhibited by deoxyglucose, collagen degradation was further enhanced. We suggest that decreased collagen levels in the connective tissues of diabetics may result from a combination of inhibition of collagen fibril formation and subsequent cross-linking, as well as increased collagen degradation.

Scar wars strategies. Target collagen

Hypertrophic scarring and keloid formation are clinical problems with effectively limited solutions. Although numerous methods have been devised to combat them, this article focuses on promising pharmacologic strategies that target collagen metabolism. Laboratory investigations of amino-acid analogs, procollagen peptides, D-penicillamine, and pentoxifylline have demonstrated them to be effective inhibitors of collagen synthesis in cultured cells and/or in animal models. Clinical trials of intralesional administration of interferons have shown impressive reductions in the size and collagen production of keloids. Furthermore, interference of extracellular matrix-enhancing cytokines, such as TGF-beta, may be an effective solution to keloids and hypertrophic scars. Additional research of soluble cytokine receptors, autoantibodies to cytokines, cytokine receptor antagonists, and cytokine-binding molecules may lead to the development of better therapeutic agents.

Role of the extracellular matrix in age-related modifications of the rat aorta. Ultrastructural, morphometric, and enzymatic evaluations

Connective tissues such as blood vessels are known to be greatly affected by age because of impaired functional properties and increased susceptibility to diseases. With the aim of providing further information on the role of the extracellular matrix in age-related modifications, we investigated the aorta in the rat model from birth to senescence by means of morphological and morphometric observations and by evaluation of lysyl oxidase activity. Results focused on the dramatic vascular rearrangements due to progressive fibrosis of the extracellular matrix and on prominent elastin modifications. The presence of lysyl oxidase activity, even in the oldest animals, might be at least partly responsible for the increased stiffness of the aging extracellular matrix. The striking age-related remodeling of the aortic architecture and the alterations of the interactions between cellular and extracellular compartments might greatly influence the functional properties of the arterial wall in senescence, at least contributing to the consequences of some apparently age-related vascular disorders.

Hydroxypyridinium collagen cross-links in human liver fibrosis: study of alveolar echinococcosis

Liver samples from patients with three different types of liver diseases, alveolar echinococcosis (a dense and irreversible fibrosis), hepatocellular carcinoma and alcoholic cirrhosis, were analyzed for their content in hydroxypyridinium cross-links found in mature collagen. We demonstrated the presence of small amounts of pyridinoline in control livers (0.27 +/- 0.06 pmol/pmol of collagen). Pyridinoline content was increased in fibrotic livers, with the highest values found in patients with alveolar echinococcosis (up to 1.33 pmol/pmol of collagen). The deoxy analogue of pyridinoline was not detected in either normal or fibrotic livers. Pyridinoline levels, expressed as picomoles per picomole of collagen, were similar in all patients with carcinoma (0.7 +/- 0.05 pmol/pmol of collagen). They were heterogeneous in patients with alveolar echinococcosis and were particularly high in patients with alcoholic cirrhosis (1.04 +/- 0.11 pmol/pmol of collagen). These results demonstrate for the first time the presence of an hydroxypyridinium cross-link in liver fibrosis and suggest that pyridinoline measurement might be an important criterion in assessing the irreversibility of human liver fibrosis.

Immunohistochemical study on tissue inhibitors of metalloproteinases in normal and pathological human livers

The localization of tissue inhibitor of metalloproteinases (TIMP) in normal and pathological livers was examined by immunohistochemistry using monoclonal antibodies at the light microscopic level. In normal liver, immunoreactive TIMP was detected in smooth muscle cells and endothelial cells of blood vessels, fibroblasts, bile duct cells and Kupffer cells, indicating that TIMP is likely to be a general element of the liver. Immunoreactivity was observed in newly-formed blood vessels, proliferating bile ductules, and fibroblasts in the expanded portal area and fibrous septa of chronic active hepatitis and cirrhosis. TIMP was strongly stained in the capsule of hepatocellular carcinoma. The intensity of the immunoreaction in the capsule was generally greater than that in cirrhotic liver apart from the tumor mass. In three of five cases with hepatocellular carcinoma, endothelial walls in contact with tumor cells were positive.

Degradation of bovine incisor root collagen in an in vitro caries model

The effects of pH, ionic strength and proteinases on the destruction of bovine incisor root collagen were studied. Experiments were done with powdered and intact root specimens. Completely demineralized root powder was subjected to solutions of varying pH and ionic strength: (a) 0.1 M acetic acid, pH 4.0, (b) 0.1 M acetic acid + 0.15 M KCl, pH 4.0, (c) 0.1 M Hepes, pH 7.0 or to (d) 0.1 M Hepes + 0.15 M KCl, pH 7.0 at 37 degrees C. The surfaces of intact root specimens were exposed to 0.1 M acetic acid, pH 4.0 (which resulted in erosive lesions) or to 0.1 M lactic acid, 0.2 mM methane hydroxy diphosphonate, pH 5.0 (which produced subsurface lesions) at 37 degrees C. After incubation, the extracts were analysed for soluble collagen and the insoluble matrices were treated with trypsin at 15 degrees C to determine the denatured collagen. To estimate sensitivity to non-specific proteinases, demineralized root powder was also treated with trypsin under physiological conditions of temperature, pH and ionic strength. The denaturation and subsequent solubilization of collagen material from the fibrils could be influenced by variations in pH and ionic strength but these effects were small when compared to proteolytic degradation under physiological conditions. This supports the hypothesis that, in root caries, destruction of exposed matrix collagen depends largely on the presence and activity of proteinases.

Collagen degradation in ischaemic rat hearts

Myocardial extracellular matrix is organized into a complex arrangement of intercellular and pericellular fibres and fibrils that serves as a supporting framework for contracting cells. Recent evidence suggests that changes in ventricular shape and function occurring after ischaemic injury may be related to alterations of this matrix. In this report we describe the rapid and extensive loss of collagen in myocardial infarction produced by ligating the left anterior descending coronary artery of the rat for 1-3 h. The total collagen content in the myocardial infarct zones after 1, 2 and 3 h of ligation was 75 +/- 8%, 65 +/- 7% and 50 +/- 10% respectively (mean +/- S.D.) of that of either the non-infarcted tissue controls or of the same regions in sex- and age-matched normal left ventricles. A marked decrease also occurred in the residual collagens which were not extractable with 6 M-guanidine hydrochloride, suggesting that rapid degradation of insoluble collagen fibres may also occur. The decreased collagen content in the 3 h myocardial infarct coincided with the appearance of several enzyme activities. Collagenase, other neutral proteinase and presumed lysosomal serine proteinase activities were increased by 3, 3 and 2 times the control values respectively. These results suggest that the increased activities of collagenase and other neutral proteinases may be responsible for the rapid degradation of extracellular matrix collagen in myocardial infarct.

Collagenases from periarticular ligaments and tendon: enzyme levels during the development of joint contracture

Our laboratories have previously demonstrated that normal rabbit periarticular ligaments, anterior cruciate ligaments (ACL), medial collateral ligaments (MCL) and patellar tendon (PT) secrete collagenase. In this current study we examined these connective tissues following an immobilization period of 4 weeks. In the ligaments producing collagenase, activity was expressed only in the control, not in the immobilized joint. Control and experimental patellar tendon samples produce collagenolytic activity, suggesting that the expression of enzyme is less affected in tendons as compared to ligaments. Characterization of these collagenases was carried out using an antiserum directed against rabbit synovial collagenase. We demonstrated that ligament (ACL) and tendon (PT) collagenases cross react with this antibody in a double immunodiffusion assay. Protein blots of PT, ACL and MCL collagenases identified one major species (Mr = 45,000) and a minor species (Mr = 50,000) of immunoreactive proteins in all three connective tissues. Differences between control and experimental enzyme levels appear to be due to less collagenase protein being produced by immobilized ligaments.

Increased resistance of the collagen in avian dystrophic muscle to collagenolytic attack: evidence for increased crosslinking

Fibrous collagen from normal (line 412) and dystrophic (line 413) chicken pectoral muscles was examined for susceptibility to bacterial collagenase by a pH-stat titration method to assess the kinetics of peptide bond hydrolysis. These experiments showed that there was a profound difference in the kinetics of hydrolysis using fibrous collagen purified from normal and dystrophic muscle. Although normal collagen was readily hydrolyzed by the collagenase, dystrophic collagen was not hydrolyzed in the presence of 200 microM Ca and was hydrolyzed slowly in the presence of 5 mM Ca. At this high Ca concentration, the Km for collagenase was six times higher in dystrophic collagen than in normal, whereas the maximum reaction rate (Vmax) remained the same. After CNBr digestion, peptides from both sources were readily hydrolyzed by collagenase in the presence of 200 microM Ca, and there was no noticeable difference in the reaction kinetics. The above results were not modified whether the chicken was sacrificed on day 4 or day 98 post-hatching, and the insusceptibility to collagenase preceded the clinical manifestations of dystrophy. The structure of both fibrous and CNBr-treated collagen from normal and dystrophic muscle was compared. One and two-dimensional gel electrophoreses showed identical peptide maps. Gel filtration of CNBr peptides showed in the excluded volume the presence of twice as much high-molecular-weight (presumably crosslinked) peptides from dystrophic collagen compared with normal. We conclude that the intermolecular crosslinks are more extensively formed in dystrophic collagen and that this increased crosslinking results in the increased resistance of the dystrophic collagen to collagenase.

Effect of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) and dichloromethylidene-bisphosphonate (Cl2MBP) on the structure of the organic matrix of heterotopically induced bone tissue

The effect of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) and dichloromethylidene-bisphosphonate (Cl2MBP) on the structure of the organic matrix of heterotopically induced bone in guinea pig was studied. Heterotopic bone formation was induced by transplantation of allogenic urinary bladder epithelium. Starting from the day of transplantation the animals were treated subcutaneously with HEBP and Cl2MBP with a dose of 12.5 mg P/kg/day during 35 days. The control group was injected with 0.9% NaCl solution. The advantage of heterotopic bone induction as an experimental model is the fact that the applied drugs act on de novo bone formation. Collagen fibers were treated as markers of bone because their size and spatial arrangement reflect the structure and maturity of organic matrix of this tissue. Decalcified histological sections of induced bone, taken 35 days after implantation of inductor, were stained by the picrosirius method. This staining enhances the natural birefringency of collagen fibers and allows for better and specific visualization of collagen fibers bundles under polarizing microscope. In this way the amount of information in the analysed image is increased. Thirty five microphotographs were analysed from each of the investigated groups with the use of optical diffractometry. The radial distribution of light intensity in diffraction patterns was analysed what allowed to evaluate spatial frequencies connected with the width of collagen bundles in induced bone tissue. Since the spatial arrangement of collagen fibers in newly formed bone is random, analysis of angular distribution of light intensity in diffractograms was not performed. Using discriminant analysis the significant differences between all three studied groups of animals were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging and cross-linking of skin collagen

This report represents a clear demonstration of a cross-link in collagen whose abundance is related to chronological aging of an organism. Recently its structure was identified as histidinohydroxylysinonorleucine. Quantification of the cross-link in various aged samples of bovine and human skin indicate that it rapidly increases from birth through maturation. Subsequently, a steady increase occurs with aging, approaching 1 mole/mole of collagen. This compound seems to be related to the relative proportions of soluble to insoluble collagen from skin in neutral salt, dilute acid, and denaturing aqueous solvents (higher concentration in the insoluble portion). It is absent from other major collagenous tissues such as dentin, bone and tendon.

Response of immature chicken meniscus to strenuous exercise: biochemical studies of proteoglycan and collagen

Male white Leghorn chickens were exercised on a treadmill at 70-80% of their maximal oxygen consumption starting at 4 weeks and continuing up to 20 weeks of age. The effect of the strenuous exercise regime on the extracellular matrix of menisci was followed through studies of proteoglycans and collagen. Avian menisci contain type I collagen, chondroitin sulfate proteoglycans, which increase with age in amount and degree of aggregation, and dermatan sulfate proteoglycans, which decrease with age. Five weeks of exercise cause a premature decrease of dermatan sulfate proteoglycans, while the chondroitin sulfate-containing molecules become significantly more aggregated than those of the tissue of age-matched controls. Strenuous exercise also causes a significant decrease in the number of pyridinoline crosslinks per mole of collagen in the menisci of young runners. The exercise-induced changes of proteoglycan and collagen occur only during the period of active growth, and all parameters return to normal when the animals reach skeletal maturity. The early proteoglycan aggregation and dermatan sulfate decrease induced by exercise are probably an adaptation to the increased loading. Although the mechanism by which strenuous exercise reduces or delays the formation of collagen pyridinoline crosslinks in menisci of skeletally immature animals is unknown, their decrease could negatively affect the mechanical properties of the tissue during the period of active growth.

Cell-layer-associated proteolytic cleavage of the telopeptides of type I collagen in fibroblast culture

In human skin fibroblast cultures a fraction of the procollagen that was processed to collagen and remained in the cell layer was further proteolytically modified by removal of both N- and C-terminal telopeptides. The proteolytic activity was associated with the cell layer, since secreted collagens were found always to contain intact telopeptides. The inclusion of neutral polymers, which caused the accumulation of the collagen in the cell layer [Bateman, Cole, Pillow & Ramshaw (1986) J. Biol. Chem. 261, 4198-4203], made the telopeptide cleavage more apparent in those cells which expressed the proteolytic activity. The extent of this cleavage was variable from cell culture to cell culture and between experiments with the same fibroblast line. The proteolytic activity was pH-dependent; cleavage was greatest at a culture-medium pH of 7.5 and 8.0 and was completely inhibited at a culture-medium pH of 7.0 and 6.5. The activity was significantly inhibited by soybean trypsin inhibitor, an elastase-specific inhibitor (N-acetylalanylalanylprolylvalylchloromethane) and the thrombin inhibitor hirudin. This cell-associated proteolytic activity may play a role in collagen degradation by removing the telopeptides, which are the primary sites of collagen cross-linking, thus destabilizing the collagen matrix sufficiently to render it susceptible to further proteolytic breakdown.

Initial characterization of a neutral metalloproteinase, active on native 3/4-collagen fragments, synthesized by ROS 17/2.8 osteoblastic cells, periodontal fibroblasts, and identified in gingival crevicular fluid

Analysis of collagenolytic activity in gingival crevicular fluid (GCF) has revealed the presence of an enzyme capable of fragmenting native 3/4- and 1/4-collagen cleavage products generated by collagenase. An enzyme with similar activity was also identified in media conditioned by fibroblasts from rat periodontal ligament and gingiva, and by rat osteoblastic cells (ROS 17/2.8, 17/2A, 17/2B). In culture, the enzyme was secreted in a latent form that could be activated by organomercurials. For further characterization of this novel enzyme (MMP-V), the osteoblast proteinase was partially purified. ROS 17/2.8 conditioned medium was harvested daily and the 25%-60% sat. ammonium sulfate fraction chromatographed on an AcA 54 gel filtration column. Latent forms of MMP-V (apparent Mr approximately 54 k) and collagenase (Mr approximately 54 k) were resolved from gelatinase (Mr approximately 76 k) and two collagenase inhibitors (Mr approximately 62 k, approximately 36 k). Activated MMP-V degraded native 3/4-collagen fragments from collagen types I and II in a step-wise manner and was active on denatured collagen. MMP-V showed a divalent cation requirement, was active at neutral pH, and was inhibited by collagenase inhibitor and fetal bovine serum, but not by serine, thiol, or carboxyl proteinase inhibitors. These properties indicate that MMP-V is a member of the matrix-degrading, neutral-metalloproteinase family of enzymes which include collagenase, gelatinase, stromelysin, and telopeptidase. The enzyme may function in the degradation of collagen fibrils by cleaving proteinase-resistant 3/4-collagen fragments that are stabilized by association with neighboring collagen molecules.

Structural crosslinking of lung connective tissue collagen in the blotchy mouse

Male mice with the sex-linked mutation Blotchy (Blo) have a defect in copper metabolism which results in deficient activity of a number of copper-containing enzymes. Inbred Blo/y mice spontaneously develop lung abnormalities which resemble emphysema and often die of ruptured aortic aneurysm. Lung, tail tendon, and tibial bone collagens from inbred Blo/y and their normal (+/y) litter mates were reduced with standardized [3H]NaBH4, acid and alkaline hydrolyzed, and chromatographed in order to quantify the aldehydic crosslink precursors, and the labile reducible and nonreducible stable mature covalent intermolecular crosslinks. Reducible lung collagen crosslinks were markedly (60%) decreased in the Blo/y mice and few, if any, mature nonreducible crosslinks were present. Total aldehydes were also decreased (65%) when Blo/y was compared to +/y. In tail tendon and bone, collagen crosslinks were decreased by only 28% and 15%, respectively. Selectively severe lack of activity of the copper-dependent enzyme level oxidase in lung with only partial lack in tendon and bone could account for the results obtained. Alternatively, insufficient reducible crosslinks, coupled with increased collagen turnover in the lung could prevent formation of the more mature stable crosslinks required to provide a proper connective tissue framework for the Blo/y lung.

Collagen metabolism in fibrotic liver. Effects of concanavalin A and aggregated myeloma immunoglobin G

We previously have shown [Takahashi & Kobayashi (1982) Hepatology 2, 249-254] that the administration of concanavalin A to mice with schistosomiasis caused liver collagen content to be reduced by 50%. Here we report the effects of concanavalin A and aggregated mouse myeloma IgG on liver lysyl oxidase activity and present further evidence concerning the possible mechanism by which the liver collagen content was decreased in infected-treated mice. The lysyl oxidase activity at 8 weeks after infection in both treated mice and untreated infected controls was about 28-fold greater than in the age-matched uninfected controls. The specific radioactivity of intracellular free [14C]proline, the rate of collagen synthesis, the ratio of collagenase-sensitive, protein-bound, hydroxyproline to proline of collagen and the intracellular degradation of newly synthesized collagen were similar in treated animals and in untreated infected controls. In contrast, the extracellular degradation of newly secreted collagen and the specific radioactivity of protein-bound [14C]hydroxyproline in the agent-treated groups were about 2-fold greater than those in the untreated infected controls. These results suggest that the observed 50% decrease in content of liver collagen of mice treated with the agents apparently was due to the increased extracellular degradation of newly secreted collagen.

Diabetes stimulates procollagen degradation in rat tendon in vitro

To identify the mechanisms responsible for the paucity of recently synthesized collagen in connective tissues during diabetes, in vitro procollagen metabolism was studied in non-diabetic (control) and diabetic rats. Achilles tendons from the two groups were incubated for 1-8 h (35 degrees C) in medium containing [14C]proline and the radiolabeled collagen in the tissue, and that released into the media, were examined by SDS-polyacrylamide gel electrophoresis and fluorography. The bulk of the radiolabeled collagen in tendon from the diabetics was recovered as degradation products; these, but also procollagen and collagen components, were prominent in the control tissues. Moreover, the collagenous components synthesized by the diabetic rat tendons were more readily digested in vitro by trypsin than those produced by control tissues. We conclude that diabetes reduces collagen accretion in connective tissues in part due to increased intracellular degradation of procollagen.

Isolation from cultured porcine gingival explants of a neutral proteinase with collagen telopeptidase activity

A neutral proteinase, distinct from collagenase, was isolated by gel-filtration from medium that had been conditioned by the culture of explanted porcine gingiva. This enzyme was shown to cleave the alpha 1 (I) chain carboxyterminal telopeptide in native collagen proximal to (i.e. nearer to the helix than) the lysyl residue at position 17 which is known to be important in the formation of covalent intermolecular cross-links. We refer to this activity as 'telopeptidase'. The enzyme had an apparent Mr of 70,000, as determined by gel-filtration. It was inhibited by ethylene diamine tetraacetic acid but not by N-ethyl-maleimide nor by phenylmethylsulphonyl fluoride. It is therefore probably a metalloproteinase. The pH optimum for this activity was 7.0-7.5. Incubation of the enzyme with fibrillar (acid-insoluble) calf-skin collagen resulted in solubilization of collagen in which shortening of the carboxy-terminal telopeptides could be demonstrated. It is suggested that the telopeptidase, acting within a region of the Type I collagen molecule which is known to be essential for the stability of collagen fibrils, could potentially play an important role in collagen degradation in vivo.

Collagen and elastin synthesis in human stroma and breast carcinoma cell lines: modulation by the extracellular matrix

The desmoplastic response to breast carcinoma is being studied. The stimulation of stromal cell proliferation by a preformed breast tumor matrix was shown. An additional mechanism for stimulating scleroprotein deposition is described here. On a per-cell basis, the synthesis of collagen and elastin was increased by 50% and 70%, respectively, in fibroblasts grown on the preformed breast tumor matrix compared to the same cells grown on plastic or on their own preformed matrix. Breast tumor cells themselves synthesized small amounts of collagen and elastin compared to fibroblasts. These levels were unchanged when breast tumor cells were grown on the preformed matrix of fibroblasts. Addition of steroid hormones to cultured cells grown on plastic or on preformed matrices in various combinations, did not change the levels of either collagen or elastin synthesis. The matrix of human breast tumor cells exerts a dual effect; it is mitogenic for fibroblasts, and also stimulates the level of collagen and elastin synthesis, events that could contribute to the formation of the desmoplastic response to human breast cancer in situ.

Induction of increased collagen and elastin biosynthesis in copper-deficient pig aorta

Young pigs raised on a copper-deficient diet develop severe abnormalities of connective tissue due to defective cross-linking of collagen and elastin. They eventually succumb to anemia and cardiovascular damage, the latter apparently due to the defective connective tissue metabolism. We evaluated the effects of nutritional copper deficiency upon collagen and elastin synthesis using short-term explant cultures of the medial portion of four successive segments of the descending aorta from 110-day-old pigs raised on a copper-deficient diet. Collagen synthesis was evaluated by collagenase susceptibility, and elastin synthesis was quantified by immunoprecipitation with an antiporcine-elastin antiserum. In the normal developing aorta, elastin synthesis was maximal in the upper thoracic aorta, while levels of collagen synthesis were highest in the lower abdominal aorta. Both activities subsided by 110 days postpartum. Compared with controls, the copper-deficient group showed: 1) histopathologic changes confined to the luminal half of the thoracic aorta; 2) a 1.3- to 1.6-fold increase in cellularity along the entire length of the organ; 3) a 1.3- to 2.4-fold increase in relative collagen synthesis, the greatest change occurring in the thoracic portion; 4) a 3- to 4-fold increase of relative elastin synthesis in the thoracic aorta, the abdominal aorta remaining unchanged; 5) 4- to 10-fold increases in collagen production; and 6) a greater than 15-fold increase in elastin production by the tissue of the thoracic aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum from type IIA hyperlipoproteinemic patients does not stimulate proliferation of and collagen synthesis in human fetal aortic smooth muscle cells in culture

The effect of serum from type IIA hyperlipoproteinemic patients on the proliferation and synthesis of collagen and other proteins of human fetal aortic smooth muscle cells (SMC) was studied. The activity of lysyl oxidase secreted into the culture medium was also measured. Type IIA hyperlipoproteinemic sera did not affect the proliferation of human aortic SMC as compared to normolipidemic sera, regardless of incubation time. The findings were similar for 3 different human fetal aortic SMC lines and one fibroblast line from adult human skin. The synthesis of collagen and other proteins was inhibited rather than stimulated in the presence of type IIA hyperlipoproteinemic sera. The activity of lysyl oxidase was not affected by type IIA hyperlipoproteinemic sera. The atherogenicity of hypercholesterolemia cannot be explained either by its direct effect on the proliferation of arterial SMC, as has been suggested by animal cell studies, or by its direct effect on the fibrogenicity of these cells.

Stiffness and contractile properties of avian normal and dystrophic muscle bundles as measured by sinusoidal length perturbations

Both tension and stiffness as a function of muscle length were measured under relaxing conditions on isolated small bundles of chemically skinned myofibers from normal and dystrophic chicken pectoral muscles. It was shown that the dystrophic muscle was stiffer than normal muscle and developed more tension for the same amount of stretch. A fraction of stiffness was not removed by extraction with either 0.6 M KI or with 5 M guanidine HCl mixed with 1% mercaptoethanol. The stiffness of dystrophic muscle was also unaffected by treatment with bacterial collagenase under conditions that destroyed the stiffness of tendon. Nyquist plots of normal and dystrophic muscles during calcium-activated isometric contraction were very similar and were characteristic of fast-twitch muscle, as evidenced by three clear exponential processes. The normal appearance of the Nyquist plot of dystrophic muscle demonstrates that cross-bridge function is not altered, and the characteristic slowing of contraction and relaxation is not a consequence of a fast-to-slow transformation of muscle types. The increased stiffness of dystrophic muscle may be a very fundamental change in the biomechanics of dystrophy. We postulate that the stiffness is mediated by an altered form of collagen, which is collagenase-resistant by virtue of excessive crosslinking.

The effect of alloxan diabetes on prolyl and lysyl hydroxylase activity in uninflamed and inflamed rat gingiva

The influence of diabetes on gingival inflammation was studied through its effect on prolyl and lysyl-hydroxylase activities and on tissue-collagen content. Inflammation induced for 7 days with either endotoxin or antigen-antibody complexes reduced the activity of both enzymes by about 45 per cent, and decreased the concentration of soluble and insoluble collagens. Diabetes alone decreased the enzyme activity by more than 50 per cent but prevented the loss of the soluble and insoluble collagens which occurs during inflammation. The complex interaction of diabetes and inflammation on collagen metabolism in gingival tissue may be explained in part by abnormalities of collagen synthesis; alterations in collagen maturation and degradation, and in leukocyte function, may also occur.

Inhibition of collagen fibril formation in vitro and subsequent cross-linking by glucose

Glucose inhibits collagen fibril formation in vitro. A linear dose response was observed, with half-maximum inhibition of fibril formation occurring at 50 mM glucose. Nonfibrillar collagen cannot be cross-linked by lysyl oxidase, an enzyme that catalyzes the initial cross-linking reaction. The degree of decreased fibril formation correlated with the loss of ability of the collagen to serve as a substrate for lysyl oxidase. Collagen that is not cross-linked is unstable and more susceptible to collagenolytic attack. Interference with collagen cross-linking and more rapid degradation may explain the decreased amounts of interstitial collagen and the poor healing of wounds associated with diabetes mellitus.

Effect of D-penicillamine pre- and post-implantation treatment on formation of sponge-induced granulation tissue in rats

DNA, collagen and sulfated glycosaminoglycans (GAGs) of rat sponge granulation tissue were studied after 42 days of D-penicillamine (D-pen) treatment at 100, 250 or 500 mg/kg/day, starting 10 days before or 28 days after induction of granulation tissue formation. The effects were compared with those observed when the same dosage was started at the onset of the granulation tissue formation and with pair-fed controls. D-pen stimulated the cell invasion into the sponge implants, as manifested by an increased DNA content, particularly with pre-treatment. Pre-treatment reduced the net deposition of of collagen per cell as assessed by the lower hydroxyproline/DNA ratio, at the lower dose leading to reduced collagen concentration. The total amount of granulation tissue collagen remained essentially unaffected within the observation period. Salt-soluble collagen was augmented in a dose-dependent manner, irrespective of treatment protocol, signifying decreased collagen cross-linking. Both pre- and post-implantation treatment enhanced the radiosulfate incorporation into sulfated GAGs, regardless of dose, whereas treatment from the day of sponge implantation had no effect. It is concluded that D-pen enhances the early connective tissue response to injury. Reduction of collagen cross-linking and net collagen deposition, concomitant with stimulation of the proteoglycan metabolism, may pertain to the antirheumatoid activity of D-pen. The observations suggest that long-term administration of D-pen, starting before new attacks of arthritis, may be most effective in controlling developing articular fibrosis.

A neutral proteinase from human gingival fibroblasts active against the c-terminal cross-linking region of type I collagen

An enzyme that was capable of releasing small fragments containing hydroxynorleucine from the c-terminal extra-helical region of the alpha 1 chain of reduced (tritiated) soluble type I collagen was found, along with collagenase, in medium that had been conditioned by the culture of human gingival fibroblasts (Gin-1). The enzyme was present in a latent form or forms and could be activated by treatment with either trypsin or p-hydroxymercuribenzoate. It was maximally active at neutral pH and inhibited by EDTA. It is suggested that this enzyme, acting within a region of the molecule which is of major importance in stabilizing fibrillar collagen through intermolecular cross-linking, could potentially play an important role in collagen turnover in vivo.

Cleavage of the carboxy-terminal cross-linking region of type I collagen by proteolytic activity from cultured porcine gingival explants

Medium conditioned by the culture of porcine gingival explants was shown to contain, in addition to collagenase, proteolytic activity capable of releasing small fragments, devoid of hydroxyproline but containing hydroxynorleucine, from reduced (tritiated) type I collagen in solution at neutral pH. Quantitative comparison of this effect with that of cathepsin D, at pH 4, revealed that the fragments were derived at least in part from the carboxy-terminal, extra-helical portion of the collagen alpha 1-chains. Incubation of concentrated conditioned medium with fibrillar acetic acid-insoluble collagen resulted in the solubilization of the TC 3/4 and TC 1/4 fragments characteristic of the action of collagenase. However, alpha 1-chain fragments isolated from the latter were found to lack the antigenic determinant normally present on the amino-terminal side of the (hydroxy-)lysine residue which is known to be involved in intermolecular cross-linking. It is therefore suggested that the proteolytic activity described above was involved in the solubilization process. Both the release of low molecular fragments from soluble collagen and the solubilization effect were abolished by ethylenediaminetetra-acetic acid.

Reversibility of D-penicillamine induced collagen alterations in rat skin and granulation tissue

Granulation tissue was produced in rats by subcutaneous implantation of Visella sponges. D-penicillamine (D-pen) 100 or 500 mg/kg was administered daily for 42 days by gastric tubing. Pairfed, placebo treated animals were included as controls. Half of the groups were kept for additionally 28 days without medication. The inhibitory effect of D-pen on cross-link formation in newly synthesized collagen was readily reversible. By contrast, cross-link deficiency lasting beyond the observation period was observed in the higher polymeric collagen variants released by dilute acid, heat exposure or limited pepsin proteolysis as estimated by solubility, alpha/beta chain ratio and/or aldehyde content. By SDS-polyacrylamide gel electrophoresis on gels containing 3.6 M urea it was shown that purified dermal acid soluble collagen from treated animals consisted of a mixture of type I and III collagen, whereas only type I collagen was detected in controls. The band pattern was identical in reduced and unreduced collagen samples. Four weeks after D-pen discontinuance type III collagen had disappeared from the acid extract. Moreover, the ratio of type III to type I collagen in the pepsin digest from both granulation tissue and skin showed a persistent rise with D-pen. These observations indicate that D-pen destabilized type III collagen in particular by interference with its disulfide linkages. The amount of granulation tissue remained unaffected throughout the experiment, whereas the skin collagen content decreased at the higher dose level. The regeneration was not completed by the end of the observation period. Modulation of the molecular stability of granuloma collagens may be of relevance for the antirheumatoid effect of D-pen, but the sustained effect on normal tissues may imply a long standing impairment of their supportive capacity.

Extracellular matrix destruction by invasive tumor cells

The invasion of normal tissues and penetration of basement membranes by malignant cells is likely to require the active participation of hydrolytic enzymes. The four major groups of connective tissue proteins, glycoproteins, proteoglycans, collagen and elastin, vary in their quantitative distributions between different tissues. With the exception of elastin, they also vary qualitatively within each class, so that there are no 'typical' connective tissue barriers to tumor cell penetration. The matrix constituents are stabilized and organized by a variety of covalent and noncovalent interactions between the connective tissue proteins. These interactions play important roles in matrix integrity and may alter the susceptibilities of the constituents to degradative enzymes. It is likely that the complete degradation of the matrix will require the action of more than one enzyme because of differing susceptibilities to tissue proteinases. Primary and transplantable tumors produce well-characterized enzymes which may participate in invasion. These enzymes may also be involved in connective tissue turnover in other normal and pathological situations. The use of long-term tumor cell cultures has verified that tumor cells themselves are capable of producing these enzymes. However, there are many potential modulating influences operative in vivo which are absent in culture so that details of actual mechanisms and control of digestion of complex substrates are not well understood. Recent work on the degradation by tumor cells of extracellular matrices previously produced by cultured cells is likely to shed more light on pathways of tissue destruction in vivo. Experiments with tumor cell variants of defined metastatic potentials will also be useful, but invasive and metastatic abilities are not necessarily correlated. It is unlikely that simple correlations can be drawn between the production of one particular degradative enzyme by all tumor cells and the complex biological mechanisms operative during tumor invasion.

Inhibition of collagen accumulation in fibrotic processes: review of pharmacologic agents and new approaches with amino acids and their analogues

Accumulation of collagen is the major pathologic feature in a variety of fibrotic processes, including dermal fibrosis in progressive systemic sclerosis, morphea, familial cutaneous collagenoma, connective tissue nevi of the collagen type and in keloids. Recent advances in the biochemistry of collagen have allowed us to define specific levels of collagen biosynthesis and degradation at which a pharmacologic intervention can lead to reduced collagen deposition. In this review, we are discussing the mechanisms of action by some of the therapeutic agents currently in use. We further present some new developments involving amino acids and their analogues which could potentially provide us with novel means to reduce the excessive accumulation of collagen in dermal fibrotic processes.

Partial purification of collagenase and gelatinase from human polymorphonuclear leucocytes. Analysis of their actions on soluble and insoluble collagens

The separation and further purification of human polymorphonuclear-leucocyte collagenase and gelatinase, using modifications of the method of Cawston & Tyler [(1979) Biochem J. 183, 647-656], are described. The final preparations yielded collagenase of specific activity 260 units/mg and gelatinase of specific activity 13 000 units/mg. Gelatinase was purified to apparent homogeneity in a latent form, and analysis of the activation of 125I-labelled latent enzyme by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and gel-filtration techniques suggested that no peptide material was lost on conversion into the active form. The purified natural inhibitors alpha 2-macroglobulin, tissue inhibitor of metalloproteinases ('TIMP') and amniotic-fluid inhibitor of metalloproteinases all inhibited the two polymorphonuclear-leucocyte metalloproteinases, but the last two inhibitors were slow to act and complete inhibition was difficult to attain. Collagenase degraded soluble types I and III collagen equally efficiently, but soluble type II collagen less well. Gelatinase alone had little activity on these substrates, although it enhanced the action of collagenase. Gelatinase was capable of degrading soluble types IV and V collagen at 25 degrees C, whereas collagenase was only active at higher temperatures when the collagens were susceptible to trypsin activity. By using tissue preparations of insoluble collagens (type I, II or IV) the activity of leucocyte collagenase was low and gelatinase activity was negligible, as measured by the solubilization of hydroxyproline-containing material. The two enzymes together were two or three times more effective in the degradation of these insoluble collagens.

The effect of D-penicillamine and methylprednisolone on the morphology of experimental granulation tissue in rats

The effects of D-penicillamine and methylprednisolone on the formation of granulation tissue was studied in rats with Visella-sponge induced granulation tissue after 42 days of treatment. D-penicillamine in doses of 20 mg-, 100 mg-, 500 mg/kg/day caused no morphological differences compared with the control groups as regards ingrowth of granulation tissue and its content of collagen fibres, inflammatory cells, vessels and glycosaminoglycans. Treatment with methylprednisolone, 0.2 mg-, 2.0 mg-, and 5.0 mg/kg/day caused a dose dependent reduction in the ingrowth of granulation tissue. Methylprednisolone caused a reduction in the number of fibroblasts and collagen fibres, but no differences in the content of glycosaminoglycans could be demonstrated between the treated and the control groups. Granulation tissue produced during combination treatment with D-penicillamine 100 mg and methylprednisolone 2.0 mg/kg/day did not differ from that observed after methylprednisolone treatment alone. Thus, only high doses of methylprednisolone gave rise to an antiinflammatory action in this morphological study on granulation tissue, whereas D-penicillamine had no effect within the present dose interval. The quantitative alterations are in agreement with parallel biochemical analyses. However, the inhibitory effect of D-penicillamine on collagen crosslinking was not associated with light microscopic changes in the ultrastructure of the collagen fibres.