Solubility of collagen from normal and scleroderma fibroblasts in culture

Increased biosynthesis of glycosaminoglycans by scleroderma fibroblasts in culture

Fibroblasts from normal and scleroderma skin, grown in culture, were incubated with radioactive glucosamine to study the biosynthesis of glycosaminoglycans (GAG). Incorporation of 3H-glucosamine and GAG biosynthesis was increased in 6 of 9 scleroderma fibroblast cultures examined. This increase ranged from 26 to 96% over normal values and was reproducible. Over 70% of the 3H-glucosamine incorporated was found in the medium of the cultures, and this fraction was used to isolate GAG. Characterization of media GAG from normal and control cultures showed that about 80% of the radioactive GAG could be degraded by a specific fungal hyaluronidase; therefore, it represented hyaluronic acid. Our findings indicate that the majority of scleroderma dermal fibroblasts display increased biosynthesis of GAG in culture and that this increase is mostly in the hyaluronic acid fraction.

Biochemical characterization of collagens and of a non-collagenous protein synthesized by guinea pig lung fibroblasts in culture

Employing various radioactive amino acids, protein biosynthesis by guinea pig lung fibroblasts has been studied in monolayer culture. The cells were shown to synthesize and secrete several collagenous and noncollagenous proteins. The biosynthesized macromolecules have been characterized employing molecular sieve and ion exchange chromatography (DEAE-cellulose column), SDS-polyacrylamide gel electrophoresis, and enzymatic digestion. It was found that the guinea pig lung fibroblasts synthesized mainly type I procollagen molecules which appeared in the media in various stages of cleavage. The intact procollagen molecules and the various processed products were identified by their electrophoretic migration in SDS-polyacrylamide slab gels and further characterized by 1) elution position on SDS-agarose columns under reducing conditions; 2) hydroxyproline content; 3) change in elution position on SDS-agarose after pepsin digestion; 4) chromatographic separation on DEAE-cellulose columns and electrophoretic mobility of the various peaks; and 5) susceptibility to collagenase digestion. Slab gel electrophoresis under non-reducing conditions of aliquots of culture media after limited pepsin digestion indicated the presence of disulfide-bonded type III collagen alpha-chains. In addition, the lung fibroblasts synthesized a non-collagenous protein composed of two disulfide-bonded chains. The individual chains appeared to have a molecular weight of approximately 220,000 when examined under reducing conditions. This protein has been identified as fibronectin based on its molecular weight, its resistance to collagenase attack, its susceptibility to protease digestion and its precipitation with specific antisera to fibronectin.

Investigation of type I and type III collagens of the lung in progressive systemic sclerosis

The interstitial collagens, type I and type III, were investigated in lung tissue from patients with progressive systemic sclerosis (PSS) with pulmonary involvement. By use of CNBr digestion of whole tissue, the relative content of type I versus type III collagen was unchanged. This contrasts with idiopathic pulmonary fibrosis. Limited pepsin digestion released greater amounts of collagen (55%) than normal (16%), but the individual collagen chains were chemically indistinguishable. A reduced amount of the more stable collagen crosslink, hydroxylysinonorleucine, was observed which was consistent with the relatively greater degree of solubilization.

Collagen heterogeneity in systemic scleroderma and other diseases

Proportions of collagen type I and type III were investigated in different tissues (kidney, liver, heart muscle, esophagus, lung and skin) in a single case of malignant systemic scleroderma. The proportion of collagen type III was higher than in healthy controls. Similarly, an increase in the proportion of collagen type III was shown in tissues affected by other inflammatory diseases. Further the authors suggest that the increase in total kidney collagen, especially type III, has important consequences for kidney function; in the described case it had the critical influence on the fatal course of the disease, and the patient died from uremia.

Connective tissue synthesis by cultured scleroderma fibroblasts. II. Incorporation of 3h-glucosamine and synthesis of glycosaminoglycans

Fibroblasts from normal and scleroderma skin, grown tissue culture, were incubated with 3H-glucosamine for 24 hours. No definite trends could be established in 3H-glucosamin incorporation or glycosaminoglycan synthesis. Over 90% of the total 3H activity as well as the glycosaminoglycans synthesized were secreted into the medium. Characterization of glycosaminoglycans showed that in both the medium and cells, hyaluronic acid ins the major glycosaminoglycan in normal and scleroderma fibroblasts. In the medium, hyaluronic acid represented 87% of the total glycosaminoglycans; it was slightly decreased in the cells. Fibroblasts were compared from the upper and lower areas of the affected dermis and an uninvolved dermal area of the same scleroderma patients.

Connective tissue synthesis by cultured scleroderma fibroblasts. I. In vitro collagen synthesis by normal and scleroderma dermal fibroblasts

The authors have been unable to demonstrate an increase in collagen synthesis by fibroblasts isolated from sclerodermatous skin. In order to elucidate this problem further, scleroderma fibroblasts were biopsied from upper dermis, from lower (including subcutaneous) dermis, and from adjacent clinically noninvolved skin. All cell lines failed to show a significant increase in collagen synthesis when they were compared to control fibroblast lines. One difference among them was that fibroblasts from involved areas showed a rate of collagen synthesis equal to or less than cells isolated from adjacent clinically noninvolved sites.