Biochemical Findings in Normal and Osteoarthritic Articular Cartilage. II. Chondroitin Sulfate Concentration and Chain Length, Water, and Ash Content*

Abstract

Softening and erosion of cartilage, the characteristic early lesions of osteoarthritis, occur in sites of decreased chondroitin sulfate concentration. The role of aging and the specific biochemical events that produce this alteration in glycosaminoglycan composition have been under study in several laboratories. Collins and McElligott found increased radiosulfate fixation in these lesions compared with normal articular cartilage from the same individuals, suggesting increased synthesis of polysaccharide (1). These observations indicated an increased turnover of chondroitin sulfate in osteoarthritic cartilage lesions, and attention has become focused on the mechanism responsible for breakdown of this glycosaminoglycan.As reported previously (2), when the cartilage proteinpolysaccharide complex was extracted from human articular cartilage obtained at autopsy, a decrease in the concentration of chondroitin sulfate but not protein was found in the areas of erosion. This observation pointed to a specific breakdown of the glycosaminoglycan, since proteolysis might be expected to cause removal of both components such as occurs after papain injection into rabbits (3). An enzyme resembling testicular hyaluronidase could be responsible, but reports of the presence of hyaluronidase in tissues other than testis were unconvincing or unconfirmed. A reevaluation of the tissue distribution of this enzyme resulted in the finding of an enzyme with most of the characteristics of testicular hyaluronidase in

Composition and glycosaminoglycan metabolism of articular cartilage from habitually loaded and habitually unloaded sites

“…This was apparent when the uronic acid values were related either to the water content or to the DNA content of the tissues, since these were essentially the same in unloaded cartilage as in loaded cartilage. The similarity of water content values in loaded and unloaded cartilage suggests that normal unloaded cartilage is different from atrophic (10,25) or osteoarthritic cartilage (26,27) in which the uronic acid content is decreaseld but the water content is increased. Presumably, the hyperhydration in damaged cartilage reflects an abnormality in the collagen network of the tissue that permits the hydrophilic proteoglycans to expand their molecular domains (28,29).…”

An essay on the biology of osteoarthritis

“…These sites of cartilage softening and erosion have a decreased concentration of hexosamine,26 sulfate,le chondroitin sulfates, 6 and, in more advanced lesions, keratan sulfate,s in comparison to normal cartilage sites from the same joints. Protein extracted along with the polysaccharide is not significantly decreased in concentration, even in more advanced lesions; collagen concentration is also unaltered in these lesions6 Erosion of the cartilage means loss of the entire cartilage substance, collagen and all.…”

In vitro rabbit articular cartilage organ model I. Morphology and glycosaminoglycan metabolism

“…DISCUSSION An in vitro adult rabbit articular cartilage organ model has been reported. Dziewiatkowski and others (1)(2)(3)(4)(5)13,14) have clearly shown that 90% plus of s 5 S 0 , is incorporated into glycosaminoglycans and that its incorporation is related to the rate of synthesis. By utilizing this technique we have shown that the articular cartilage slices and floating plugs have the property of a constant rate of 35S0, incorporation into glycosaminoglycans from day 7 to day 14.…”