The metabolic heterogeneity of rabbit ear cartilage chondroitin sulphate

Effect of calcium on cell proliferation and extracellular matrix synthesis in arterial smooth muscle cells and dermal fibroblasts

The effect of calcium on cell proliferation and connective tissue formation was studied in cultured vascular smooth muscle cells (SMC) and dermal fibroblasts. Calcium deficiency caused a modest decrease in proliferation of smooth muscle cells but this effect was small compared to that previously observed with fibroblasts. Synthesis of connective tissue components was affected differently in the two cell types. Biosynthesis of proteoglycans was assessed by metabolic labeling of their glycosaminoglycan side chains. Different levels of extracellular calcium did not affect proteoglycan production by fibroblasts, but it was significantly reduced in smooth muscle cells incubated in calcium-deficient medium. Both smooth muscle cells and fibroblasts were able to produce appreciable amounts of collagen in the complete absence of calcium and in both cell types collagen synthesis was increased when calcium was present. Fibroblasts, however, showed a much smaller response to calcium than did smooth muscle cells. In fibroblasts the maximum rate of collagen synthesis was achieved in a narrow range of calcium concentration which was slightly below that found commonly in the tissue culture medium. By contrast, in smooth muscle cells the rate of collagen synthesis increased greatly when calcium was present and this elevated rate persisted even when the cells were exposed to high levels of extracellular calcium. We conclude that these findings may be of significance to the development of atherosclerotic lesions.

Biosynthesis of aortic collagen and glycosaminoglycan following immunological injury

The effect of immunological injury upon the early in vivo changes in aortic connective tissue metabolism was studied. It was found that a single antigen (bovine serum albumin), when administered in multiple doses, activated collagen synthesis and increased the rate of lgycosaminoglycan synthesis in the arterial wall. The degree of stimulation of both connective tissue components was higher in animals receiving a higher dose of antigen.

Biosynthesis of chondroitin sulphate in cartilage regenerated from perichondrium

In a rabbit's ear cartilage an experimental defect was lined with a perichondrial flap and in a rabbit's trachea a defect in two tracheal cartilages was reconstructed with a free autogenous graft of aural perichondrium. Outgrowth of new tissue, morphologically indistinguishable from cartilage was observed within 4 weeks. In cartilage defects not bridged by perichondrium, no regeneration of cartilage occurred. Inorganic 35SO4, administered in vivo, was incorporated into the newly formed tissue. The labelled product was isolated and identified as chondroitin sulphate. The results support the view that authentic cartilage may be regenerated from the perichondrium.

The metabolic heterogeneity of glycosaminoglycans of the different zones of the epiphyseal growth plate and the effect of ethane-1-hydroxy-1, 1-diphosphonate (EHDP) upon glycosaminoglycan synthesis in vivo

The synthesis of total and unextractable glycosaminoglycans of rabbit epiphyseal growth plate was studied by determination of the incorporation in vivo of 35S-sulphate into various glycosaminoglycans separated by microfractionation procedures using CPC and ECTEOLA columns. In the narrow hypertrophic zone, hyaluronic acid and chondroitin sulphate of low molecular weight were found to be unextractable with 3M guanidinium chloride for 24 h, thus being firmly bound within the tissue. While the unextractable chondroitin sulphate showed a sharply reduced synthesis rate in the hypertrophic zone compared with that in the columnar and resting zones, a rapid increase in the synthesis of extractable chondroitin sulphate toward the calcification front is indicated. At microfractionation, solubility profiles indicated that the unextractable chondroitin sulphate was of predominantly lower molecular weight and/or charge density compared to that of the whole tissue, most evident in the hypertrophic zone. The distribution pattern of incorporated 35S showed a close correspondence to the distribution of the various chondroitin sulphate fractions both for extracted and unextracted tissue. In the hypertrophic zone, higher radioactivity was found for chondroitin sulphate of predominantly low molecular weight and/or charge density in extracted compared to unextracted tissue. Low doses of EHDP caused no change of distribution of the various glycosaminoglycans but generally inhibited their synthesis.

Calf articular cartilage in organ culture in a chemically defined medium. 2. Concentrations of glycosaminoglycans and [35S]-sulfate incorporation at different oxygen tensions

Articular cartilage from 6-month-old calves was maintained in organ culture in Eagle's minimum essential medium at different oxygen tensions between 20 and 50%. When well standardized cartilage pieces of about 1 mm thickness were used the results showed a high degree of reproducibility. The glycosaminoglycans were studied using the cetylpyridinium chloride cellulose and epichlorohydrin triethanolamine (ECTEOLA) column techniques on a microscale. In some experiments the cartilage was labelled with [35S]sulfate. Small alterations of the concentrations and distribution of different glycosaminoglycans were found and were not affected by various oxygen tensions for up to 4 weeks. A small increase was found in the fractions containing low molecular weight chondroitin sulfate. Devitalized cartilage, maintained under identical conditions, remained largely unaltered during the 4 weeks. The [35S]sulfate activity calculated per mole of hexosamine showed a general decrease during culture maintenance. High specific activities in the fractions containing low molecular weight chondroitin sulfate and keratan sulfate were found between 1 and 3 weeks of maintenance in 20% oxygen. Maintenance in 50% oxygen resulted in severely disturbed synthesis of glycoaminoglycans. The results are interpreted as showing that the synthesis pattern of glycosaminoglycans in articular cartilage can be altered by other factors and without the prior loss of glycosaminoglycans.

Protein-polysaccharide biosynthesis. Membrane-bound saccharides

Membrane-bound saccharides obtained from ear cartilage from rabbits recovering from papain injection were examined for glycosyl acceptor properties, alkali lability, molecular size and degree of sulphation. Although considerable glucuronosyl transfer from UDP-glucuronic acid could be demonstrated, less than one-third could be identified as representing chondroitin linkage formation; there was little or no effect of molecular size on acceptor properties. Approximately one-half of the membrane-associated chondroitin-like saccharide chains are solubilized by alkali, whereas one-half require proteolysis for solubilization. These fractions are analytically indistinguishable and both contain xylose and galactose as well as uronic acid and sulphated N-acetyl-galactosamine. All fragments that were examined contained stoicheiometric amounts of axial sulphate ester, strongly suggesting a close relationship between chain extension and sulphation.