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The rare osteosclerotic disease, pycnodysostosis, is characterized by decreased osteoclastic bone collagen degradation due to the absence of active cathepsin K. Although this enzyme is primarily expressed by osteoclasts, there is increasing evidence that it may also be present in other cells, including fibroblasts. Since fibroblasts are known to degrade collagen intracellularly following phagocytosis, we analyzed various soft connective tissues (periosteum, perichondrium, tendon, and synovial membrane) from a 13-week-old human fetus with pycnodysostosis for changes in this collagen digestion pathway. In addition, the same tissues from cathepsin K-deficient and control mice were analyzed. Microscopic examination of the human fetal tissues showed that cross-banded collagen fibrils had accumulated in lysosomal vacuoles of fibroblasts. Morphometric analysis of periosteal fibroblasts revealed that the volume density of collagen-containing vacuoles was 18 times higher than in fibroblasts of control patients. A similar accumulation was seen in periosteal fibroblasts of three children with pycnodysostosis. In contrast to the findings in humans, an accumulation of internalized collagen was not apparent in fibroblasts of mice with cathepsin K deficiency. Our observations indicate that the intracellular digestion of phagocytosed collagen by fibroblasts is inhibited in humans with pycnodysostosis, but probably not in the mouse model mimicking this disease. The data strongly suggest that cathepsin K is a crucial protease for this process in human fibroblasts. Murine fibroblasts may have other proteolytic activities that are expressed constitutively or up regulated in response to a deficiency of cathepsin K. This may explain why cathepsin K-deficient mice lack the dysostotic features that are prominent in patients with pycnodysostosis.

Recent data suggest that gelatinase A (matrix metalloproteinase-2, MMP-2) plays an important role in the degradation of collagen of soft connective tissues. In an attempt to investigate its participation in more detail we assessed the digestion of collagen in cultured rabbit periosteal explants and compared this with the level of active MMP-2 and collagenases. The data demonstrated that both collagen degradation and MMP activity increased with time. Conditioned medium obtained from explants cultured for 72 h showed that the level of active MMP-2 correlated with collagen degradation (r = 0.80, d.f. = 23, P < 0.0001). Such a relationship was not found with collagenase activity (r = -0.08, d.f. = 21, NS). The possible involvement of MMP-2 in collagen degradation was investigated further by incubating explants with selective gelatinase inhibitors (CT1166, CT1399 and CT1746). In the presence of these compounds breakdown of collagen was almost completely abolished (approximately 80%). Finally we assessed whether periosteal fibroblasts had the capacity to degrade collagen type I that conferred resistance to collagenase activity. Breakdown of this collagen did not differ from degradation of normal collagen. Taken together, our data provide support for the view that MMP-2 plays a crucial role in collagen degradation of soft connective tissue.

Numerous data strongly suggest the involvement of cytokines and the matrix metalloproteinase collagenase (MMP-1) in the pathogenesis of periodontitis. Recently, we have demonstrated that, upon culturing under the influence of IL-1 alpha + EGF, a large amount of inactive procollagenase (MMP-1) is stored in the extracellular matrix of periosteal tissue. We now show that this endogenous reservoir of proenzyme can be operative after activation with plasmin and is able to induce a rapid and almost complete breakdown of the collagenous extracellular matrix. The level of collagen degradation following activation showed a strong correlation with the amount of proenzyme that was incorporated in the tissue. The highest level of degradation (70% of the total amount of collagenous proteins) was found with the IL-1 alpha + EGF-treated explants, followed by those treated with IL-1 alpha alone (35%). Explants cultured with EGF or in the absence of cytokines, containing only small amounts of procollagenase, showed little collagen breakdown following plasmin activation (7%). Inhibition of metalloproteinases by EDTA, or blockage of plasmin by PMSF, prevented the degradation in all explants irrespective of the amount of proenzyme present in the tissue. Our findings demonstrate that endogenous proenzyme stored in a native connective tissue matrix can be activated at a later time interval which results in a massive breakdown of the tissue. This study shows a possible pathway of collagenase-induced breakdown without recent de novo synthesis of the enzyme. Such a sequence may be operative in chronic inflammatory diseases, such as periodontitis, where production of procollagenase under the influence of cytokines spans a longer time period, whereas breakdown is often characterized by a cyclic behaviour.

Purpose: Valvular incompetence and venous wall abnormalities have been suggested as primary etiologic factors responsible for the development of varicose veins. This study was conducted to evaluate the connective tissue constituents of greater saphenous varicosities. Proteolytic activity, a factor that can lead to matrix degradation and cause weakening and dilation of the venous wall, was also assessed., Methods: The collagen and elastin contents of 16 nonthrombophlebitic greater saphenous varicose veins (VV) and seven normal greater saphenous veins (NV) were quantified. In addition, four duplex scanning-confirmed competent segments of greater saphenous veins (i.e., potential varicose veins [PV]) affected by varicosis at alternate sites were analyzed. Proteolytic activity was determined by zymography and radiolabeled substrate assay., Results: The content of collagen was significantly increased in the VV and PV compared with NV (VV = 189 +/- 7 mg/gm, PV = 189 +/- 9 mg/gm vs NV = 144 +/- 10 mg/gm, p < 0.05). Conversely, the elastin content in the VV and PV was significantly reduced (VV = 53 +/- 3 mg/gm, PV = 50 +/- 4 mg/gm vs NV = 74 +/- 4 mg/gm, p < 0.05). The collagen to elastin ratio demonstrated an alteration in VV and PV compared with NV (VV = 3.7 +/- 0.3, PV = 3.9 +/- 0.4 vs NV = 2.0 +/- 0.2, p < 0.05). Casein and gelatin zymography did not demonstrate significant qualitative differences in the enzymatic activities among the three groups. Quantitative analysis of the elastase activity in the venous tissues was similarly not appreciably altered (VV = 5.1 +/- 0.2 U/gm, PV = 5.3 +/- 0.2 U/gm vs NV = 5.7 +/- 0.3 U/gm)., Conclusion: A significant increase in the collagen content and a significant reduction in the elastin content of VV were demonstrated. The net increase in the collagen/elastin ratio is indicative of an imbalance in the connective tissue matrix. The biochemical profile of PV was similar to VV and significantly different from NV. These preliminary data support the presence of connective tissue abnormalities before valvular insufficiency. In addition, the absence of an increase in the proteolytic activity excludes enzymatic matrix degradation as an essential component in the formation of venous varicosities.

Periodontal soft tissues were cleaved from freshly extracted human teeth. Tissues were then prepared for subsequent biochemical and morphological studies according to the following plan: 1) immediate immersion in liquid nitrogen for the biochemical assay of superoxide dismutase (SOD); 2) immediate fixation prior to routine preparation for routine transmission electron microscopy; 3) immediate fixation prior to preparation for electron microscopic immunohistochemistry. Biochemical analysis showed that the human periodontal ligament contained about twice as much SOD activity as human skin (dermis), but considerably less enzyme activity than that seen in red blood cells. Interestingly, periodontal SOD activity appeared to decrease with age. Immunohistochemistry localized enzyme activity to the periphery of matrix collagen fibrils and to the glycocalyx of tissue fibroblasts. The pathophysiology of this enzyme regarding inflammatory diseases such as periodontitis is discussed.

Serum levels of type IV collagen and hepatic type IV collagenase activity, as markers for formation and degradation respectively of basement membrane collagen (type IV collagen) in liver, were measured in patients with various alcoholic liver diseases. Development of alcoholic liver fibrosis seems to be due to both increased formation and decreased degradation of basement membrane collagen. Both measurements of type IV collagenase activity and serum level of type IV collagen were assumed to be useful to predict irreversible state of hepatic fibrosis.

The distribution of subunit A of Factor XIII (FXIIIa) and of collagenous components was investigated by the avidin-biotin-peroxidase complex (ABC) method for FXIIIa and by the Sirius red F3BA method, respectively, in 43 cases of radicular cysts. Besides the covering epithelial layer, the radicular cyst wall was composed of the following three layers: an inner granulomatous layer, an outer fibrous connective tissue layer, and an intermediate layer. In each layer, a positive reaction for FXIIIa was observed in certain connective tissue cells. These FXIIIa-containing cells were few in number in the inner layer where collagenous components were also sparse. In the slightly to moderately fibrous intermediate layer, these cells markedly increased in number and were dendritic or stellate in shape. In the outer densely fibrous connective tissue layer, they decreased slightly in number and were slender and spindle-shaped. The results obtained in the present study indicate the close relationship between the distribution of FXIIIa-containing cells and of collagenous components. Such a relationship suggests that these cells play an important role in the process of fibrosis occurring in the radicular cyst wall.

Changes in collagen fractions as well as in the activity of leucocytic collagenase and collagenolytic cathepsin of rats after 30 days of gamma-rays exposure were examined. A statistically significant decrease in total collagen content resulting from the reduction of salt--soluble (NSC) and acid--soluble (ASC) collagen fractions was found. An increased content of insoluble collagen fraction (ISC) may confirm the opinion about stimulative gamma-rays influence upon cross--links formation. An increase in collagenolytic enzymes activity may account for an elevated degradation of collagen; with a contribution of leucocytic collagenase and collagenolytic cathepsin. Perhaps the quantitative increase in insoluble collagen stimulates elevated biosynthesis of collagenolytic enzymes determining the process of protein degradation. Further investigations are needed to explain the radiobiological effects of gamma-rays on the connective tissue.

Connective tissue components were detected immunohistochemically in cultured rat hepatocytes and sinusoidal lining cells. In the Ito and endothelial cells, the staining reactions to prolyl hydroxylase were strong. The reaction in the hepatocytes, however, was weaker, and there was no staining reaction to prolyl hydroxylase in the Kupffer cells. In the Ito cells, types III and IV collagen were clearly positive, whereas reactions to type I collagen were very weak. In the endothelial cells, type IV collagen stained clearly, whereas the reaction for type I collagen was very weak, and there was no reaction for III. Laminin was clearly positive in the Ito and endothelial cells. Connective tissue components were not detectable in the Kupffer cells. The hepatocytes were positive for types I, III, and IV collagen, but the staining reactions to type IV collagen were weak. Laminin staining was almost negative. These results suggest that type IV collagen is produced mainly by nonparenchymal cells and that types I and III collagen are produced by both parenchymal and nonparenchymal liver cells.

An IgG2a murine monoclonal antibody derived against human eosinophils was shown to immunoprecipitate the 78,000 dalton form of human eosinophil peroxidase (EPO). To confirm the specificity of the antibody, we used a glucose-oxidase avidin biotin procedure to immunostain 32 human cell lines and tissues. An eosinophilic subline of HL-60 promyelocytic leukemia was the only cell type other than eosinophils to be recognized by the antibody. Because previous reports have described occult eosinophilic degranulation in tissues with a variety of pathological conditions, we immunostained cryostat sections of four consecutive lymph node biopsies of nodular sclerosis Hodgkin's disease with the monoclonal antibody. Our objective was to characterize by immunohistology the eosinophilic infiltration in a lymphoma that frequently contains substantial numbers of eosinophils. In all four cases of nodular sclerosis Hodgkin's disease, there was striking and extensive deposition of EPO in a dendritic pattern throughout the connective tissue and collagen bands. The extent of deposition of EPO in the bands far exceeded the degree of infiltration by intact eosinophils, as determined by examination of routinely stained tissue sections. A similar dendritic pattern was not observed in any of six benign lymph nodes that were immunostained for EPO. We conclude that the monoclonal antibody described in this report is specific for EPO and that eosinophils extensively degranulate and release EPO in the bands of nodular sclerosis Hodgkin's disease. Moreover, the degree of eosinophilic infiltration in this disorder cannot be assessed solely on the basis of intact eosinophils.

Specific collagenases responsible for the initial enzymic step leading to degradation of the collagen fibrils of connective tissues have been found in both latent and active forms. The most important factor controlling the local activity of collagenase extracellularly may be an inhibitor that is synthesised by connective tissues, and it is proposed that latent enzymes are all enzyme-inhibitor complexes.

Type VII collagen is the major structural protein of anchoring fibrils, which are believed to be critical for epidermal-dermal adhesion in the basement membrane zone of the skin. To elucidate possible mechanisms for the turnover of this protein, we examined the capacities of two proteases, human skin collagenase, which degrades interstitial collagens, and a protease with gelatinolytic and type IV collagenase activities, to cleave type VII collagen. At temperatures below the denaturation temperature, pepsin cleaves type VII collagen into products of approximately 95 and approximately 75 kDa. Human skin collagenase cleaved type VII collagen into two stable fragments of approximately 83 and approximately 80 kDa, and the type IV collagenase (gelatinase) produced a broad band of approximately 80 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cleavage of type VII collagen was linear with time and enzyme concentration for both enzymes. Although the Km values were similar for both enzymes, the catalytic rate of cleavage by type IV collagenase is much faster than by interstitial collagenase, and shows a greater rate of increase with increasing temperature. Sequence analysis of the cleavage products from both enzymes showed typical collagenous sequences, indicating a relaxation in the helical part of the type VII collagen molecule at physiological temperature which makes it susceptible to gelatinolytic degradation. Interstitial collagenase from both normal skin cells and cells from patients with recessive dystrophic epidermolysis bullosa, a severe hereditary blistering disease in which both an anchoring fibril defect and excessive production of collagenase can be observed, produced identical cleavage products from type VII collagen. These data suggest a pathophysiological link between increased enzyme levels and the observed decrease or absence of anchoring fibrils.

Copper's role in connective tissue is linked to the enzyme lysyl oxidase. From a biochemical perspective, copper is a cofactor for the enzyme and a determinant of its activity in connective tissues. Lysyl oxidase catalyses a post-translational oxidation of certain lysine and hydroxylysine residues. The peptidyl aldehydes so formed become active centres for the formation of cross-links in collagen and elastin. Less well understood is how copper controls the steady-state activity of lysyl oxidase; the enzyme fails in copper deficiency. Giving copper to a deprived animal increases lysyl oxidase activity in aortic tissue. Such activation in vivo appears to require caeruloplasmin. Suspending aortic tissue in a copper-enriched growth medium also activates lysyl oxidase provided that tissue structure is kept intact. Activation in vitro occurs with the binding of copper to a large-molecular-weight component, presumably the enzyme. Binding will not occur if protein synthesis is blocked. These studies clearly show that the synthesis of mature elastin and collagen can be controlled by the availability of copper. They further suggest that transport of copper to aortic tissue and its engagement to lysyl oxidase are linked to the synthesis or lysyl oxidase, an extracellular carrier, or both.