Glycoproteins of the connective tissue matrix

A combined physicochemical approach towards human tenocyte phenotype maintenance

During in vitro culture, bereft of their optimal tissue context, tenocytes lose their phenotype and function. Considering that tenocytes in their native tissue milieu are exposed simultaneously to manifold signals, combination approaches (e.g. growth factor supplementation and mechanical stimulation) are continuously gaining pace to control cell fate during in vitro expansion, albeit with limited success due to the literally infinite number of possible permutations. In this work, we assessed the potential of scalable and potent physicochemical approaches that control cell fate (substrate stiffness, anisotropic surface topography, collagen type I coating) and enhance extracellular matrix deposition (macromolecular crowding) in maintaining human tenocyte phenotype in culture. Cell morphology was primarily responsive to surface topography. The tissue culture plastic induced the largest nuclei area, the lowest aspect ratio, and the highest focal adhesion kinase. Collagen type I coating increased cell number and metabolic activity. Cell viability was not affected by any of the variables assessed. Macromolecular crowding intensely enhanced and accelerated native extracellular matrix deposition, albeit not in an aligned fashion, even on the grooved substrates. Gene analysis at day 14 revealed that the 130 kPa grooved substrate without collagen type I coating and under macromolecular crowding conditions positively regulated human tenocyte phenotype. Collectively, this work illustrates the beneficial effects of combined physicochemical approaches in controlling cell fate during in vitro expansion.

Fine structure of the human newborn and infant vocal fold mucosae

This study was carried out to determine the fine structure of the membranous portion of the human newborn and infant vocal fold mucosae and to clarify how the human vocal fold mucosa begins to grow after birth. Light and electron microscopic observations were made on the vocal fold mucosae excised from human newborn and infant larynges. Our findings are summarized as follows. 1) Reinke's space of the newborn vocal fold is a loose structure composed of ground substance and sparse fibers. 2) Ground substance is abundant and glycoproteins (fibronectin) are present in the lamina propria. 3) In the maculae flavae of newborn vocal folds, fibroblasts begin to form collagenous, reticular, and elastic fibers. 4) In the infant maculae flavae, fibroblasts are activated to become stellate in shape and synthesize extracellular matrices such as collagenous and reticular fibers. 5) After birth, the collagenous and reticular fibers synthesized in the maculae flavae extend toward the middle of the membranous portion of the vocal fold mucosa. 6) Glycoprotein (fibronectin) determines the orientation of collagenous and reticular fiber deposition. 7) Glycoprotein (fibronectin) decreases with the increase of the fibrous components in Reinke's space. 8) Elastic fibers increase after collagenous and reticular fibers appear in Reinke's space. 9) Much hyaluronic acid (glycosaminoglycan) is actively produced in the infant maculae flavae. 10) The collagenous and reticular fibers serve as stabilizing scaffolds for the other extracellular matrices, such as elastic fibers and glycosaminoglycan. During infancy, the extracellular matrices synthesized in the maculae flavae appear in the membranous portion of the vocal fold, each at a different time, so as to initiate the 3-dimensional formation of the vocal fold mucosa.

Biochemical markers of hepatic fibrosis

Most liver diseases lead to a pathobiochemical reaction termed liver fibrosis. This is a dynamic process implying different rates of progression or regression. Thus, histological examination of a liver biopsy is essential for a diagnosis but biochemical tests are necessary for assessing the activity of the process and monitoring its evolution. We review the most important constituents of liver connective tissue and the biochemical tests developed for evaluating liver fibrosis. The aminopeptide of type III procollagen is the most widely used parameter: two different radioimmunoassays have been developed with different affinities for the two circulating forms of the molecule. The determination of serum P3P reveals an elevation of blood levels both in acute and chronic liver diseases. In the first, serum P3P is an index of hepatic necrosis and inflammation which correlates with other biochemical parameters. In the second it is an index of active fibrogenesis. Moreover, in primary biliary cirrhosis this parameter is an independent prognostic variable and an important predictor of survival. Other immunoassays exist for different collagen cleavage products, but their clinical value is not established. Laminin and fibronectin are the principal structural glycoproteins in liver. Fibronectin determination does not seem to be of clinical value in liver disease. In contrast, serum laminin correlates with the severity of portal venous pressure in advanced liver disease. Its concentration parallels the severity of varices and may indicate the risk of bleeding. Hyaluronate is a high molecular weight polysaccharide, raised serum concentrations reflect both its increased synthesis by activated fibroblasts and its impaired catabolism by the liver. Thus, it may be useful for evaluating and monitoring the progression of chronic liver disease. The measurement of the activity of prolyl 4-hydroxylase as well as that of lysine oxidase and other enzymes has been proposed, but their clinical value is not sufficiently demonstrated. A panel of tests (e.g., laminin, hyaluronate and the aminopeptide of type III procollagen) seems to be recommended for a biochemical assessment of liver fibrosis in clinical practice.

3H-mannose utilization by fibroblasts of the periodontal ligament

The synthesis, intracellular translocation, and secretion of mannose-containing glycoproteins(s) by periodontal ligament fibroblasts have been investigated by means of electron microscopic radioautography. Tritiated mannose was administered to young mice via jugular vein, and radioautographs were prepared at 5, 10, 20, and 35 minutes, 4 and 8 hours after injection. Analysis of electron microscopic radioautographs revealed a maximum labeling (94%) with 3H-mannose of the rough endoplasmic reticulum at 5 minutes. Labeling of the Golgi components started to increase from 10 minutes (14%) and reached a maximum level at 20 minutes (31.2%). At 35 minutes, secretion granules, dense bodies, profiles of intracellular collagen, and the cell surface were labeled. At 8 hours, most labelling (79.2%) was extracellular, and associated either with the collagenous matrix (43.7%) or the cell surface (35.5%). Cytoplasmic vesicles containing dense materials around collagen fibrils were also labeled at 8 hours. It is concluded that mannose is directly incorporated into the rough endoplasmic reticulum (RER), and that mannose-containing glycoprotein(s) are packaged in the Golgi apparatus into secretory granules. Mannose-containing glycoprotein(s) become distributed on the periodontal ligament (PDL) fibroblast cell surface, cytoplasmic dense bodies, and the extracellular matrix.

Type VI collagen and glycoprotein MFPI are distinct components of the extracellular matrix

Two collagenous glycoproteins, Mr 140,000 and Mr 150,000, are synthesized and secreted into the medium of cultured fibroblasts. The glycoprotein of Mr 140,000 is identical with the 140K(VI) component of type VI collagen by both immunological and physicochemical criteria. The glycoprotein of Mr 150,000 is immunologically distinct and exhibits the physicochemical characteristics of the putative elastic microfibrillar glycoprotein MFPI.

Inhibition of collagen production in scleroderma fibroblast cultures by a connective tissue glycoprotein extracted from normal dermis

It was shown in a previous paper that a connective tissue glycoprotein (CTGP) extracted from normal rabbit dermis was able to inhibit total protein and collagen syntheses by normal dermis fibroblast cultures. In the present study, the effects of CTGP on scleroderma fibroblasts were investigated. [14C]Proline incorporation into total proteins of the supernatant was not significantly different from that found in controls. By contrast, the amount of collagen, expressed as percentage of total secreted protein, was far higher in scleroderma cultures than in normal ones (14.4% +/- 6.0% vs 4.6% +/- 0.9%). Addition of CTGP to the medium induced a concentration-dependent inhibition of [14C]proline incorporation into proteins from both control and scleroderma cells. In control cultures, no significant decrease of the percentage of collagen was observed, but over 60 micrograms/ml, both cytotoxic effects and inhibition of protein synthesis occurred. In scleroderma cultures, the inhibition was twice as effective on collagen as on noncollagen protein synthesis. The inhibition of collagen secretion was not related either to changes in collagen hydroxylation or to the intracellular catabolism of newly synthesized procollagen.

Inhibition of fibroblastic cell division by a fraction of structural glycoproteins extracted from rabbit dermis

A fraction of structural glycoproteins (SGP) extracted from rabbit dermis exerted a concentration-dependent inhibition on the multiplication of normal dermal fibroblasts and of mouse sarcoma fibroblastic cells CCRF S-180 II. The inhibition was fully reversible when the SGP was eliminated from the culture medium.

A collagenous glycoprotein found in dissociative extracts of foetal bovine nuchal ligament. Evidence for a relationship with type VI collagen

A collagenous glycoprotein (Mr 140000) was isolated from dissociative extracts of foetal bovine nuchal ligament and purified by a combination of ion-exchange and gel-filtration chromatography. This glycoprotein (designated MFPI) exists as a large-Mr disulphide-bonded aggregate in the absence of a reducing agent. The purified glycoprotein was shown to contain about 6% (w/w) carbohydrate, mostly as galactose, glucose and mannose. Amino acid analysis showed the presence of hydroxyproline and hydroxylysine, indicative of its collagenous nature. The collagenous nature of this glycoprotein was further investigated by enzyme digestion. Pepsin digestion produced three major fragments, which were identical with peptides of type VI collagen. Bacterial-collagenase digestion of the unreduced glycoprotein also produced several discrete peptides. However, reduction of the glycoprotein before bacterial-collagenase digestion resulted in the degradation of these discrete peptides. Glycoprotein MFPI extracted in dissociative conditions appears to be a larger-Mr form of type VI collagen, believed to originate from microfibrillar components in the intact tissue.

Reticulin and its related structural connective tissue proteins in the rheumatoid synovium

Argyrophilic reticulin fibres are an important component of the rheumatoid synovium and their distribution and that of their individual protein constituents have been studied in synovial biopsies from a series of 29 cases of rheumatoid arthritis. In acutely inflamed synovia they are predominantly found underneath the hyperplastic synovial lining layer and related to the inflammatory cell infiltrate. With developing chronicity the reticulin network is gradually replaced by mature collagen. This histological pattern is mirrored by changes in the individual components of reticulin fibres-fibronectin, the non-collagenous reticulin component of Pras and Glynn (NCRC) and collagen type III.

Ultrastructure and composition of connective tissue in hyalinosis cutis et mucosae skin

Skin biopsies from a patient with hyalinosis cutis et mucosae (HCM) were studied by routine histology, electron microscopy, biochemical extractions, and immunofluorescence for extracellular matrix proteins. The upper dermis consisted of large hyaline regions mainly composed of noncollagenous proteins. A portion of this material was solubilized by reduction in 8 M urea. Anti-sera against these proteins revealed multiple antigens most of which were also detectable in normal skin. The hyaline regions showed a reduced content of collagens, particularly of thick fibrils and of fibronectin. The basal lamina around capillaries and at the dermal-epidermal junction appeared as multiple, concentric layers of amorphous laminae intercalated with thin collagen fibrils. They consisted of collagens type III and IV and of laminin as shown by immunofluorescence. Antibodies could also be raised against laminin of HCM skin which showed strong cross-reactions with authentic mouse laminin. Cultured fibroblasts from the HCM lesion showed increased synthesis of noncollagenous proteins at the expense of newly synthesized collagens. Some but not all of these noncollagenous proteins were also produced by fibroblasts from normal skin. The above data indicate that the hyaline material in HCM originates from the overproduction of noncollagenous proteins, most of which are normal constituents of human skin.

Ibuprofen inhibition of postsurgical adhesion formation: a time and dose response biochemical evaluation in rabbits

Recently, a reduction in postoperative adhesion formation in rabbits which received high-dose ibuprofen (280 mg/kg/day) treatment in the perioperative interval was reported. Because these results could have resulted from a nonspecific effect of ibuprofen, the effects of ibuprofen on peritoneal injury in a time and dose response fashion was evaluated. Seventy rabbits were assigned to seven groups. All rabbits received a dose of ibuprofen 1 hr prior to surgery. The time of the second dose was either 8 or 12 hr after the surgical procedure; 8 hr for groups A, C, and E; 12 hr for groups B, D, and F (A, B: 70 mg/kg; C, D: 35 mg/kg; E, F: 17.5 mg/kg, respectively). Thereafter, rabbits received further dosing every 6 hr to complete a total 10-dose regimen. Group G served as a nontreatment control. Surgical injury was induced by either abrasion or ischemia of the right uterine horn. Immediately after closing the incision, 10 muCi of 14C-labeled glucosamine and 10 muCi of 14C-labeled proline were injected into each rabbit. All rabbits underwent a second laparotomy on the fifth postoperative day for evaluation of adhesion formation. Uterine tissue adjacent to the site of uterine healing was excised for determination of glycosaminoglycan and collagen concentration. In the nontreatment control group G, 5 of the 10 rabbits had severe grade 2 adhesions at the time of second laparotomy, 3 had grade 1 filmy adhesions, and 2 had no adhesions. This is in marked contrast (P less than 0.025) to the group that received ibuprofen at 70 mg/kg/day with the first postoperative dose 8 hr after surgery (group A). In this group, no rabbits had severe grade 2 adhesions, 3 rabbits had filmy grade 1 adhesions, and 7 rabbits were free of pelvic adhesions. A gradual tendency towards more adhesions and more severe adhesions was apparent in groups B-F as the dose of ibuprofen was decreased and the time of first postoperative injection was prolonged. The recovery of 14C-labeled glucosamine from the glycosaminoglycan extraction demonstrated a positive correlation between the cpm recovered and the severity of adhesions formed. Groups A and B had, overall, the lowest ratios of glucosamine (1.47 +/- 0.08 and 1.56 +/- 0.09, respectively) which were statistically different from the nontreatment control group G (1.76 +/- 0.11, P less than 0.05). There was also a positive correlation between the formation of severe adhesions and the ratio of 14C-labeled proline recovered by collagen extraction.(ABSTRACT TRUNCATED AT 400 WORDS)

The interaction of pentosan polysulphate (SP54) with human neutrophil elastase and connective tissue matrix components

The binding of pentosan polysulphate (SP54) to human polymorphonuclear leucocyte elastase (PMNE) and some of its natural and synthetic substrates has been investigated. Using an ion exchange (DE52) assay system the binding of SP54 to PMNE was found to be 100 times stronger than to collagen or proteoglycan (PG). While the order for in vitro binding of the drug to purified substrates was found to be PG greater than gelatin greater than type I collagen, in vivo experiments indicated that SP54 was localized in tissues rich in collagen. Using gel-exclusion chromatography it was shown that these tissues also contained proteinaceous components other than PG and collagen which interacted with SP54. These results indicate that the potent inhibitor activity of SP54 against PMNE (50% inhibition at 1.7 X 10(-7)M) probably occurs by a specific interaction with the enzyme rather than by substrate binding inhibition, although the latter interaction may be important for localising the drug in these tissues.

The role of fibronectin in the pathogenesis of antigen-induced arthritis in the rabbit

Fibronectin (FN), a high molecular weight glycoprotein, is present in plasma and is a normal structural component of the synovium in the rabbit, as it is in man. FN is also involved in the sequence of changes seen in synovium in experimental antigen-induced arthritis. Its widespread distribution in inflamed synovia in the initial acute phase of induced arthritis probably merely reflects the presence of FN of plasma origin in serous exudates. In established experimental arthritis, FN co-distributes with fibrin, while in synovia undergoing organisation, FN is present intracellularly in several types of mesenchymal cells (suggesting local synthesis) and is deposited on immature collagen fibrils. However, it is no longer present when mature collagen is formed. The persistence of FN, along with fibrin, in inflamed joints, and its involvement in fibrosis, suggest that it may play a significant part in determining the chronicity of this form of experimental arthritis.

Structural glycoproteins from rabbit aortic media

Rabbit aortic intima-media fragments were incubated with [14C]mannose and [3H]fucose for 6 h to detect glycoproteins synthesized in situ. The radioactively labelled and the non-labelled samples were extracted with 0.2 mM-CaCl2/0.5 mM-dithiothreitol/0.5 mM-ATP and chloroform/methanol/water (4:4:1, by vol.). The delipidated residue was extracted with 5 M-guanidinium chloride/0.05 M-dithiothreitol/0.1 M-Tris/0.4% Na2EDTA, pH 7.5, before (extract 1) and after hydrolysis with collagenase (extract 2). The proteins in extracts 1 and 2 were S-carboxamidomethylated and separated by molecular-sieve chromatography, polyacrylamide-gel electrophoresis and isoelectric focusing in sucrose gradients in urea. The apparent molecular weights of glycoproteins were 36 000 (glycoprotein I) from extract 1, 50 000 (glycoprotein II) and 130 000 (glycoprotein III) from extract 2. The molecular weights of the non-labelled and radioactively labelled glycoproteins were identical. Glycoproteins I, II and III contain large amounts of polar amino acids and methionine. They contain neither hydroxyproline nor 3-methylhistidine. A hydroxyproline-containing component of 160 000-apparent-mol.wt. relatively rich in polar amino acids and labelled with incorporated sugars was isolated from extract 1. The incorporation in vitro of radioactive sugars into glycoproteins I, II, III and collagenous glycoproteins indicates that they are synthesized in the surviving aorta by the smooth-muscle cells.

Biochemical evaluation of postsurgical wound repair: prevention of intraperitoneal adhesion formation with ibuprofen

Proteins central to normal wound repair, including collagen and proteoglycans, were extracted during postoperative mesothelial regeneration, then the quantitation was correlated to macroscopic observations of normal peritoneal reepithelialization and/or postoperative adhesion formation. Sixty-three New Zealand white female rabbits of reproductive age were prospectively assigned to either Group A, untreated control; Group B, which received intramuscular injections of ibuprofen, 70 mg/kg per injection (immediately and 6 hr after surgery); or Group C, which received 5 intramuscular injections of ibuprofen (4 hr before surgery, and immediately, 6, 12, and 18 hr after surgery). The right uterine horn underwent one of three standardized surgical traumas: (1) abrasion of the peritoneal surface with a scalpel until punctate bleeding developed, (2) ischemia of the uterine horn by removal of the collateral blood supply (devascularization), (3) crushing of the uterine horn by cross clamping for 3 min with a Kelley hemostat. Thereafter, 10 microCi of C-14-labeled glucosamine and 10 microCi of C-14-labeled proline were injected into the marginal ear vein of each rabbit. All rabbits underwent a laparotomy on the fifth postoperative day for evaluation of adhesion formation and tissue biopsy for protein extraction. No reduction in adhesion formation was found using a 2-dose postoperative treatment regimen. However, using a 70 mg/kg X 5-doses regimen in the immediate perioperative interval, a significant reduction in both adhesion formation and severe adhesion formation (both P less than 0.025) were found following standardized surgical injury. The extent of adhesion formation was correlated with the extractable glycosaminoglycan and collagen concentrations. As determined by recovered glucosamine and proline, a positive correlation was apparent between the severity of adhesion grade and formation of new glycosaminoglycans or collagens. Thus, ibuprofen appears to inhibit adhesion formation through suppression of fibroproliferative inflammation.

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.

A lethal, Larsen-like multiple joint dislocation syndrome

We describe here two isolated cases of lethal, Larsen-like multiple joint dislocation syndrome. Death occurred shortly after birth with pulmonary insufficiency due to tracheomalacia and/or lung hypoplasia. Both had abnormal dermal collagen bundles. In one case, histochemical studies showed abnormal cartilagenous matrix and striking deficiency in the dense collagen bundles of joint capsules; electronmicroscopic studies of the hyaline cartilage of the trachea documented a relative increase of the small, short fibers with decrease of the matrix collagen fibers. This study confirms that this Larsen-like syndrome is a disorder of connective tissue, possibly involving dysmaturity of the collagen fibers, with a predilection for joint capsules and tracheal cartilage. This lethal condition is characterized by pulmonary insufficiency, tracheomalacia, and collagen fiber dysmaturity.

Noncollagenous proteins in cartilage of normal subjects and patients with degenerative joint disease. A gel electrophoretic study

Normal articular cartilage from subjects of various ages and cartilage from patients with degenerative joint disease were extracted with 4M guanidinium chloride. After dialysis against 8M urea pH 6.8, a 0.2M NaCl fraction was obtained by ion exchange chromatography on DE-52 in 8M urea. This fraction was concentrated, reduced, and analyzed by sodium dodecyl sulfate--polyacrylamide gel electrophoresis (7% gels). Six major noncollagenous protein bands (P1-P6) were found; 2 were identified as the link proteins. The approximate molecular weights of P1-P6 were: 87,000, 64,000, 56,000, 46,000, 41,000, and 27,000. A similar sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern of P1-P6 was found in young baboons, in normal young and aged humans, and in patients with degenerative joint disease. Peaks corresponding to extracted collagen were decreased in older patients and increased in patients with degenerative joint disease, even those of advanced age.

Collagenase for Peyronie's disease experimental studies

This pilot study was designed to test the feasibility of using purified clostridial collagenase in the clinical management of Peyronie's disease. The basic properties of this agent are discussed. We studied its effect on Peyronie's plaque tissue by a quantitative in vitro assay utilising the liberation of free alpha-amino groups as an index of enzymatic collagenolysis. Tissue from three patients with Peyronie's disease was used. Tunica albuginea from a second group of three normal patients was studied in the same manner, and no selectivity for the collagen of Peyronie's plaques was identified. Utilising human pericardium as a uniform collagenous substrate, a simple dose-effect relationship was established, and the distribution characteristics of injected collagenase observed. Its effects on blood vessels and nerves in vivo was determined as well as the effects of collagenase on the histology of normal and diseased human tissue in vitro. A tentative dose for use in Peyronie's disease was established, which is discussed in light of existing toxicological data. The study was designed to test the feasibility of purified collagenase in the clinical management of Peyronie's disease. Data included detail plaque digestion and dose-effect relationships in vitro, as well as the histological effects on plaques, blood vessels, and nerves in vivo and in vitro. It is concluded that collagenase may warrant further clinical testing in the treatment of Peyronie's disease.

Collagens of basement membranes

Recent biochemical and immunohistochemical studies have described several components of basement membranes including heparan sulfate proteoglycan, 2 high molecular weight glycoproteins (fibronectin and laminin), and 2 collagen types (IV and V). These collagens have several properties which distinguish them from other types that are located in the interstitium: (a) type IV forms an amorphous, felt-like matrix, and neither IV nor V is found in large, cross-banded fibrils, (b) both have an increased content of hydrophobic amino acids, (c) the precursor (pro) forms are larger than those of interstitial collagens, (d) type IV contains interruptions within the triple helix, and e) both IV and V are resistant to human skin collagenase but are substrates for selected neutral proteases derived from mast cells, macrophages, and granulocytes. By immunofluorescence staining, type IV collagen has been localized to basement membranes at the dermal-epidermal junction, in capillaries, and beneath endothelial cells in larger vessels. Ultrastructurally it has been shown to be a specific component of the lamina densa. Type V collagen has been localized to the pericellular matrices of several cells types and may be specific for extramembranous structures which are closely associated with basal laminae. Other collagenous proteins have been described which may be associated with the extracellular matrix. One of these is secreted by endothelial cells in culture and by peptide mapping represents a novel collagen type. It is secreted under ascorbate-free conditions and is highly sensitive to proteolytic degradation. It has been proposed that a dynamic reciprocity exists between cells and their extracellular matrix which partially determines cell shape, biosynthesis, migration, and attachment. Examples of phenotypic modulation in several of these phenomena have been shown with endothelial cells grown on different substrates and isolated from different vascular environments.

Isolation and characterization of lung connective-tissue glycoproteins

1. Glycoproteins of hamster, rat and baboon lung parenchyma were investigated by using [14C]glucosamine incorporation in vitro followed by sequential extraction of the macromolecular components and characterization of the glycoproteins in the extracts. 2. Slices of lung parenchyma maintained in vitro incorporated [U-14C]glucosamine linearly with time into non-diffusible macromolecules for up to 5h. All the macromolecule-associated 14C label was present as [14C]glucosamine. 3. These 14C-labelled macromolecules were extracted from previously delipidated and salt-extracted lung by 5M-guanidinium chloride in the presence of dithiothreitol and proteinase inhibitors before (extract A1) and after (extract A2) hydrolysis of the collagen by collagenase. The [14C]glucosamine-labelled glycoproteins in extracts A1 and A2 contained 55 and 5% respectively of the total [14C]glucosamine incorporated in the lung of all three species studied. 4. The [14C]glucosamine-labelled glycoproteins were analysed by gel-filtration chromatography, sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing. The major [14C]glucosamine-labelled glycoproteins of baboon lung parenchyma had apparent mol.wts. of about 400 000, 140 000 and 65 000 with isoelectric points respectively of 4.8, 5.4 and 5.4. The hamster lung glycoproteins with isoelectric points of 4.1 and 5.8 were devoid of hydroxyproline and contained galactose, mannose and N-acetylglucosamine. These experiments indicate that several distinct glycoproteins are synthesized in situ by the cells of pulmonary parenchyma and may well play a role in its structure and function.

Two major non-collagenous glycoproteins in embryonic chick arteries

Glycoprotein-containing extracts were obtained from thoracic arteries of embryonic chicks by sequential treatment involving 6 M guanidinium chloride, purified bacterial collagenase, and 6 M guanidinium chloride plus 50 mM dithiothreitol. Two major glycopolypeptides, designated G1 and G2, having apparent mol. wts. of 140,000 and 130,000 respectively were detected by SDS/polyacrylamide gel electrophoresis. Equilibrium density gradient ultracentrifugation demonstrated G1 and G2 to be glycoproteins and not proteoglycans or glycosaminoglycans. Amino acid analysis of a glycoprotein-enriched fraction confirmed the non-collagenous nature of G1 and G2. The highly insoluble nature of these glycoproteins suggests that these species are intimately associated with the extracellular matrix. Glycoproteins of similar size were also extracted from wing tendons indicating that G1 and G2 may be common to the elastic tissues of the chick.

Isolation and preliminary characterization of a structural glycoprotein complex from bovine corneal stroma

After extraction of bovine corneal stroma with 1M CaC1(2) and subsequent digestion of the insoluble residue with purified bacterial collagenase, two crude structural glycoprotein (SPG) fractions were obtained; one which precipitated upon dialysis against water of the collagenase solubilized material and the other which was extracted by 8M urea from the collagenase insoluble material. Amino acid analyses of these crude SGP fractions indicated that they were primarily non-collagenous but that very small amounts of collagen-derived amino acids were present. Upon gel filtration of these SGP fractions on Sepharose 4B-CL, void volume fractions were isolated from each of the crude fractions which were enriched, relative to the original crude fractions, in the collagen-derived amino acids. Carbohydrate analysis indicated that the void volume fractions had the properties of glycoproteins rather than proteoglycans. Upon disulfide reduction and SDS-PAGE, each of these fractions was resolved into five major protein bands with molecular weights of 155,000, 137,000, 117,000 82,000 and 34,000. Only the three largest bands contained the collagen derived amino acids. These data are consistent with the presence within bovine corneal stroma of a large structural glycoprotein complex comprised of at least five protein components associated through disulfide bonds. Collagen apparently is associated with three of these, either through covalent crosslinkage, or as part of the primary structure.

Biosynthesis of glycoproteins by rabbit dental pulp fibroblasts in culture

Confluent dental pulp fibroblast cultures incorporated L-[3H]-fucose in a linear manner with time into non-diffusible macromolecules over 24 h. Ascorbate supplementation did not appear to alter the amount or type of macromolecules. Equilibrium CsCl-density-gradient centrifugation established that the [3H]-fucose-labelled macromolecules released into the medium were predominantly glycoproteins. Sodium dodecyl sulphate-polyacrylamide-gel electrophoresis showed that the major fucosylated glycoprotein had an apparent molecular weight of 230,000, but several other species were also seen. The major fucosylated glycoprotein was fibronectin by its affinity for gelatin and its immunoprecipitation with a specific anti-(cold-insoluble globulin).

A basement membrane-associated glycoprotein from skeletal muscle

We have isolated a major glycoprotein that appears to be associated with rat skeletal muscle basement membrane. We determined that the glycoprotein was part of the muscle cell surface complex when we found it to be enriched in preparations of muscle ghosts. We isolate the glycoprotein from homogenized muscle preextracted with 4 M and 8 M urea. It elutes as a major component in the presence of 8 M urea/50 mM 2-mercaptoethanol. Its apparent molecular weight on sodium dodecyl sulfate gels is 130,000. Amino acid analysis indicates that it is not a collagen but that it does contain small amounts of hydroxyproline and hydroxylysine. There may be collagenous domains in the glycoprotein molecule, for it is cleaved into three fragments by purified bacterial collagenase. Immunoperoxidase staining confirms that the 130,000-dalton protein is localized at the surface of adult skeletal muscle cells. It is probably a general basement membrane-associated glycoprotein because we found material immunologically cross-reactive with the muscle glycoprotein in basement membrane regions of kidney, liver, brain, and small intestine. We have shown the glycoprotein to be distinct from fibronectin, laminin, and types I, III, IV, and V collagens in enzyme-linked immunosorbent assays.

Characterization of a structural glycoprotein from bovine ligamentum nuchae exhibiting dual amine oxidase activity

A structural glycoprotein has been extracted from bovine ligamentum nuchae by using 5 M guanidine hydrochloride containing a disulfide bond reducing agent and purified by preparative gel electrophoresis. The isolated material appeared to be monodisperse, with a molecular weight of approximately 34000, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by analytical ultracentrifugation. It contains 10% carbohydrate comprising mannose, N-acetylglucosamine, galactose, and sialic acid in a 6:5:3:3 molar ratio. The glycoprotein has been assayed for peptidyl-lysine oxidase activity by using [3H]lysine-aortic elastin, prepared from 15- to 17-day-old chick embryos, as a substrate. In the absence of free lysine, the specific activity of the preparation over a 2-h incubation was approximately 60 X 10(4) dpm/mg of purified protein. Addition of 10 mM lysine resulted in an approximately 50% decrease in the specific activity. Free lysine was shown to act as a substrate for the glycoprotein preparation as indicated by control experiments using [3H]lysine in place of the aortic substrate. These results demonstrate that the glycoprotein exhibits a dual amine oxidase activity. In the presence of 0.27 mM beta-aminopropionitrile fumarate, a concentration which completely inhibits peptidyl-lysine oxidase activity in other lysyl oxidases, the glycoprotein preparation was inhibited by approximately 14%. In the absence of 5 M guanidine hydrochloride and reducing agent, the glycoprotein undergoes aggregation which in the presences of copper ions results in the formation of cylindrical tactoids, the diameter of which (11 nm) corresponds closely to that of the fibrils which in the majority of connective tissue matrices constitute the microfibrillar component mainly associated with elastic fibers.

Current concepts in the diagnosis of human soft tissue sarcomas

The surgical pathologist is often called upon to make a rapid decision about the malignant potential of a soft tissue tumor. These tumors have specific stromas that support growth and endow the tumor with unique qualities, as well as being manifestations of the phenotypic expression of tumor cells. Collagen, the major protein of the stroma of tumors, is now recognized as a family of proteins, each a different gene product. Immunofluorescence microscopy studies using antibodies directed against purified stromal components, particularly the different type specific collagens, may soon be available in large quantities. These are potentially useful tools for the surgical pathologist not only in making that important decision, but also for developing a classification scheme for human sarcomas. This scheme will inevitably have a more sound biological basis than those currently used.

The nature of the microfibrillar glycoproteins of elastic fibres. A biosynthetic study

1. Cell cultures propagated from foetal bovine ligamentum nuchae synthesized and secreted two glycoproteins, designated MFP I and MFP II, that are closely related to elastic-fibre microfibrils. Glycoproteins MFP I (apparent mol.wt. 150 000) and MFP II (apparent mol.wt. 300 000) were metabolically labelled, separated from other culture-medium components by immunoprecipitation with a specific anti-(microfibrillar protein) serum, and analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and sodium dodecyl sulphate/gel-filtration chromatography. 2. Ligament cells also synthesized and secreted fibronectin, but salt-fractionation and immunoprecipitation studies with a specific anti-(cold-insoluble globulin) serum established that neither glycoprotein MFP I nor glycoprotein MFP II was related to fibronectin. 3. The secretion of glycoprotein MFP I, but not that of glycoprotein MFP II, was enhanced by the addition of ascorbate to the culture medium. 4. Ascorbate-supplemented ligament cells incorporated [3H]proline into glycoprotein MFP I, and 36% of the nondiffusible proline residues were hydroxylated, exclusively as 4-hydroxy[3H]proline. Less than 1% of the total proline residues in [3H]proline-labelled glycoprotein MFP II were hydroxylated. 5. Ascorbate-supplemented cells incorporated [14C]lysine into glycoprotein MFP I and 30% of the non-diffusible lysine residues were hydroxylated. 6. Newly secreted glycoprotein MFP I was digested by highly purified bacterial collagenase to yield polypeptide fragments of apparent mol.wts. 50 000 and 30 000. Glycoprotein MFP II was not digested by bacterial collagenase. 7. The results suggest that elastic-fibre microfibrils are composed of a novel collagenous glycoprotein MFP I in association, as yet undefined, with a non-collagenous glycoprotein MFP II.

Elastogenesis and microfibrillar glycoprotein synthesis by bovine ligamentum nuchae cells in culture

Cell cultures propagated from fetal bovine ligamentum nuchae were found to accumulate an extensive extracellular matrix containing collagen and elastic fibers when maintained for periods up to 8 weeks. The synthesis by these cells of two glycoproteins, designated MFP I and MFP II, which are immunologically related to components of the elastic fiber microfibrils was investigated. MFP II, apparent mol. t. 300,000, was shown to be a non-collagenous glycoprotein whereas MFP I, apparent mol. wt. 150,000, was found to be a novel collagenous glycoprotein containing hydroxyproline and glycosylated hydroxylysine residues but exhibiting properties of distinct from the known collagens. Two glycoproteins having characteristics similar to MFP I and MFP II were also identified in an extract of the cell layer and in a "microfibrillar protein preparation" from intact nuchal ligament.

Degradation of connective tissue matrices by macrophages. II. Influence of matrix composition on proteolysis of glycoproteins, elastin, and collagen by macrophages in culture

Thioglycollate-elicited mouse peritoneal macrophages were cultured in contact with the mixture of extracellular matrix proteins produced by rat smooth muscle cells in culture. Both live macrophages and their conditioned media hydrolyzed glycoproteins, elastin, and collagen. Live macrophages also degraded extracellular connective tissue proteins secreted by endothelial cells and fibroblasts. The glycoproteins in the matrix markedly inhibited the rate of digestion of the other macromolecules, particularly elastin. When plasminogen was added to the matrix, activation of plasminogen to plasmin resulted in the hydrolysis of the glycoprotein components, which then allowed the macrophage elastase easier access to its substrate, elastin. Thus, although plasmin has no direct elastinolytic activity, its presence accelerated the rate of hydrolysis of elastin and therefore the rate of matrix degradation. These findings may be important in an understanding of disease states, such as emphysema and atherosclerosis, that are characterized by the destruction of connective tissue.

Degradation of connective tissue matrices by macrophages. I. Proteolysis of elastin, glycoproteins, and collagen by proteinases isolated from macrophages

We have investigated the ability of neutral and lysosomal enzymes of mouse macrophages to degrade the insoluble extracellular matrices secreted by smooth muscle cells, endothelial cells, and fibroblasts. Matrices produced by smooth muscle cells contained glycoproteins, elastin, and collagens, but matrices of endothelial cells and fibroblasts contained no elastin. Sequential enzyme digestion of residual matrix revealed that plasmin, a product of macrophage plasminogen activation, degraded 50-70% of the glycoprotein in the matrices but did not degrade the elastin or the collagens. Purified macrophage elastase degraded glycoprotein and elastin components but had no effect on the collagens. The rate of elastin degradation by macrophage elastase was decreased in the presence of the glycoproteins. In contrast, human granulocyte elastase effectively degraded the matrix glycoproteins, elastin, and, to a lesser extent, collagens, Mammalian collagenase degraded only collagens. Conditioned medium from resident and inflammatory macrophages, containing mixtures of the secreted proteinases, degraded the glycoprotein and elastin components of the matrices. However, conditioned medium was less effective in degrading matrix than comparable amounts of purified macrophage elastase because > 90% of the elastase in the medium was in a latent form. Inclusion of plasminogen in the assays accelerated degradation. In the presence of plasminogen, glycoproteins were degraded readily by medium from P388D1, pyran copolymer-, thioglycollate-, and periodate-elicited macrophages and, to a lesser extent, by medium from endotoxin-elicited and resident macrophages; medium from P388D1, thioglycollate-, and periodate-elicited macrophages was most effective in elastin degradation, and resident, endotoxin-elicited and pyran copolymer-elicited macrophages degraded almost no elastin. The macrophage cathepsins D and B degraded all the matrix components at an optimum pH of 5.5 and acted with the secreted neutral proteinases to degrade the connective tissue macromolecules to amino acids and oligopeptides. These data indicate that macrophages at inflammatory sites contain and secrete proteolytic enzymes that could degrade the extracellular matrix.