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Maturation-related differences in the structure and composition of proteoglycans synthesized by chondrocytes from bovine articular cartilage
Journal article   Open access   Peer reviewed

Maturation-related differences in the structure and composition of proteoglycans synthesized by chondrocytes from bovine articular cartilage

Eugene J‐M A Thonar, Joseph A Buckwalter and Klaus E Kuettner
The Journal of biological chemistry, Vol.261(5), pp.2467-2474
1986
DOI: 10.1016/S0021-9258(17)35958-6
PMID: 3080435
url
https://doi.org/10.1016/S0021-9258(17)35958-6View
Published (Version of record) Open Access

Abstract

Calf (2-3-month-old) and steer (approximately 18-month-old) bovine articular chondrocytes were isolated and cultured as high density monolayers. The proteoglycans synthesized on day 5 during a 15-h period of labeling with [35S]sulfate or [3H]glucosamine were isolated and characterized. The majority (greater than 70%) of the newly synthesized proteoglycans were found in the medium. When viewed in the electron microscope, medium-derived proteoglycans of high buoyant density were longer in calf than in steer. The medium and extracts of the cell layer were pooled and the radiolabeled proteoglycans were fractionated by isopycnic density gradient centrifugation performed under dissociative conditions. The low buoyant density fraction contained, in both calf and steer, small-sized nonaggregating proteoglycans containing chondroitin sulfate. The high buoyant density fraction contained greater than 90% of the newly synthesized proteoglycans. The majority were able to interact with hyaluronic acid to form aggregates. Calf high buoyant density fraction proteoglycans were larger, had longer chondroitin sulfate chains and lower ratios of keratan sulfate chains/chondroitin sulfate chains than steer high buoyant density fraction proteoglycans. These maturation-related differences are typical of those present in the proteoglycans of the calf and steer cartilage matrix from which the chondrocytes were isolated. Experiments with beta-D-xylosides showed that steer cultures had the capacity to synthesize twice as many chondroitin sulfate chains/cell as calf cultures. At each xyloside concentration used, chondroitin sulfate chains were longer in calf than steer. At both ages, chain size decreased with increase in rate of synthesis; the relationship between chain size and rate of synthesis was, however, quite different at the two ages. The results of these studies suggest that articular chondrocytes have an inherent program that determines the quality of proteoglycans synthesized at different ages.
 Fundamental and applied biological sciences. Psychology Proteins Biological and medical sciences Glycoproteins Analytical, structural and metabolic biochemistry

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