Biochemical study of cardiac valvular tissue. Biosynthesis in vitro of hexosamine-containing substances in bovine heart valve

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.

Acid mucopolysaccharides of congenitally defective, rheumatic, and normal human aortic valves

The qualitative nature, total amount, and relative proportion of various acid mucopolysaccharides (AMPSs) found in congenitally defective (bicuspid), young rheumatic, and normal aortic valvular tissue were compared. No differences in the qualitative nature of AMPSs were found in any of the aortic tissues studies; hyaluronic acid, chondroitin sulfate B, and chondroitin sulfate A/C were the primary AMPS components, with a trace amount of heparin. Congenitally defective aortic valves showed increasing amounts of calcification, a lowering of total AMPS content, and an alteration in the relative proportions of various AMPS with advancing age, as compared with age-matched normal aortic valves. The total AMPS content of rheumatic aortic valves from individuals under the age of 21 years was found to be significantly higher than that of age-matched normal controls. In addition, these rheumatic aortic valves showed an alteration in AMPS composition that was similar to that of congenitally defective aortic valves obtained from older individuals. These observations suggest nonspecific changes in the AMPS composition caused by chronic tissue damage, calcification, and fibrosis.

The collagen of heart valve

A hydroxylysine-rich type I collagen has been isolated from pepsin-digested porcine heart valve. The ratio of alpha1 to alpha2 in the isolated molecule was 2:1. The component alpha chains exhibited unusual chromatographic behavior in comparison to corresponding chains from human dermis and lathyritic rat skin collagen. The composition of component cyanogen bromide peptides identified the alpha chains as authentic type I chains and demonstrated hydroxylysine enrichment throughout the length of the chain. delta6-Dehydro-5,5'dihydroxylysinonorleucine, a collagen cross-link derived from two hydroxylysyl residues and ordinarily found in hard tissue collagens was found to be the predominant cross-link in heart valve.

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.