Constitutional variations of acidic glycosaminoglycans in normal and arthritic bovine articular cartilage proteoglycans at different ages.

Proteoglycans extracted from normal and arthritic bovine articular cartilage of various ages were fractionated and purified under associative and dissociative conditions. After proteolytic digestion, the composition of the acidic glycosaminoglycans (AGAG) in the proteoglycans was determined enzymatically by digestion with chondroitinase-AC II, chondroitinase-ABC, Streptomyces, hyaluronidase and keratanase. Under both associative and dissociative conditions, uniform distribution of chondroitin sulfate (CS) isomers from proteoglycans of different ages was observed: With increasing age, the relative proportion of 4-sulfated disaccharide units in total AGAG decreased, whereas that of 6-sulfated disaccharide units increased. The relative proportion of 4-sulfated disaccharide units in total CS and the ratio of 4-sulfated disaccharide units to 6-sulfated disaccharide units were greater in arthritic cartilages than in normal cartilages of the same ages. At all three ages studied, the relative proportion of 4-sulfated disaccharide units in sequential fractions increased with the decrease of cesium chloride (CsC1) density, as the proportion of 6-sulfated disaccharide units decreased. The relative proportions of hyaluronic acid (HA) and keratan sulfate (KS) increased with age. The AGAG components of cartilage proteoglycans were distributed with a certain regularity in the fractions of CsCl density gradients, but underwent changes with increasing age and in arthritic process.

Age-dependent constitution of chondroitin sulfate isomers in cartilage proteoglycans under associative conditions.

Associated proteoglycans were prepared with guanidine-HCl from bovine articular cartilage of various ages. They were purified and fractionated by equilibrium centrifugation in cesium chloride (CsCl) density gradients. The compositions of chondroitin sulfate (CS) isomers in associated proteoglycans of articular cartilages of three ages were compared based on the relative amounts of disaccharide units. The results indicated that the proportions of 4-sulfated disaccharide units comprised around 2/3, 1/3, and 1/6 of the total CS in the associated proteoglycans of calf, 18-month-old cow, and 8-year-old cow, respectively. In contrast, the proportions of 6-sulfated disaccharide units in the proteoglycans were in the reverse order; they comprised nearly 1/3, 1/2, and 2/3 of the total CS, respectively, at the three ages. Thus, with increasing age, the ratio of 4-sulfated disaccharide units to 6-sulfated disaccharide units decreased significantly. With the decrease of CsCl density in the gradients, the proportion of 4-sulfated disaccharide units to total CS as well as that of 4-sulfated disaccharide units to 6-sulfated disaccharide units increased in the associated proteoglycans of all ages. The increased ratios of 4-sulfated to 6-sulfated disaccharide units with decreasing CsCl density were significant among the individual proteoglycans: 1.84-2.36 in calf, 0.40-0.89 in 18-month-old cow, and 0.16-0.28 in 8-year-old cow.

Constitutional heterogeneity of the glycosaminoglycans in articular cartilage proteoglycans.

Proteoglycans were extracted from bovine articular cartilage with guanidine-HCl and fractionated in cesium chloride density gradients by equilibrium ultracentrifugation. The acidic glycosaminoglycan (AGAG) components were then determined enzymatically with chondroitinase-ABC and streptomyces hyaluronidase. Under associative and dissociative conditions, the distribution of the AGAG components was as follows: the ratio of 4-sulfated disaccharide units to total AGAG increased with decreasing density gradients whereas that of 6-sulfated disaccharide units to total AGAG increased with increasing density gradients. The ratio of disulfated disaccharide units to total AGAG increased somewhat with decreasing density gradients whereas that of non-sulfated disaccharide units tended to decrease. Although the cartilage proteoglycan macromolecules were heterogeneous, a certain regularity was observed with respect to the distribution of sulfate and the degree of sulfation in the chondroitin sulfate chains of the proteoglycans.

Distribution of chondroitin sulfate in cartilage proteoglycans under associative conditions.

Proteoglycan aggregates and proteoglycan subunits were extracted from bovine articular cartilage with guanidine-HC1 folowed by fractionation by equilibrium centrifugation in cesium chloride density gradients. The distribution of chondroitin sulfates (CS) in the cartilage proteoglycans was studied at the disaccharide level by digestion with chondroitinases. In the proteoglycan aggregate fraction, it was observed that the proportion of 4-sulfated disaccharide units to total CS increased from the bottom to the top fractions, whereas that of 6-sulfated disaccharide units was in the reverse order. Thus, the ratio of 4-sulfated disaccharide units to 6-sulfated disaccharide units increased significantly with decreasing density. The proportion of non-sulfated disaccharide units to total CS tended to increase with increasing density. These data indicate a polydisperse distribution of CS chains, under the conditions used here, in proteoglycan aggregates from bovine articular cartilage.

An ultrastructural study of the articular cartilage in calcium pyrophosphate dihydrate (CPPD) crystal deposition disease (chondrocalcinosis articularis).

An ultrastructural study of articular cartilage from five patients with calcium pyrophosphate dihydrate (CPPD) crystal deposition disease was performed. The CPPD crystals, identified by micro X-ray diffraction, were usually found in clusters, located in intercellular areas of the intermediate cartilage layer. The matrix surrounding the clusters either showed a normal morphology or a homogeneous appearance, within which faint cross striations but no distinctly fibrillar outlines could be identified. Another change in the matrix, characterized by an increased electron density and longitudinally fragmented collagen fibres, was also seen. This latter change was generally seen without concomitant CPPD crystal deposition. No specific relationship between the crystals and the collagen fibres or the granular background material of the matrix was encountered.