Articular cartilage proteoglycans in osteoarthritic STR/Ort mice

Compared to controls, the lateral and medial tibial articular cartilage chondroitin sulfate (CS) content in male STR/Ort mice was elevated between 8 and 19 weeks of age, fell at 24–26 weeks and increased again thereafter. The CS cartilage content of CBA mice remained relatively unchanged. Cartilage CS content was measured in female CBA and STR/Ort mice and in male and female Balb C mice, all at 18 weeks of age. In every case the content was much lower than that found in male STR/Ort mice. CS unsaturated disaccharides were analysed by capillary electrophoresis after digestion of the glycosaminoglycans with chondroitinase ABC. Chondroitin-4-sulfate (C4S) was the predominant isomer at all ages in both strains. The C4S:C6S isomer ratio in CBA mice was much higher in the lateral than the medial cartilage. This difference was much less marked in STR/Ort knee joints: these mice have relatively more C6S than CBA mice. Proteoglycans, extracted from STR/Ort and CBA male mouse cartilage, were characterized by large pore gel electrophoresis and Western blotting. All cartilages contained two slow mobility bands identified as aggrecan by the reactivity with the mab 1C6. Both bands contained C4S and C6S chains. A third band of faster mobility contained only C4S and was 1C6 negative. It was present in both strains. Thus the STR/Ort cartilage contained a normal spectrum of murine articular cartilage proteoglycans.