Proteoglycan composition and biosynthesis by human osteochondrophytic spurs of the femoral head.

The composition and biosynthesis of sulphated proteoglycan by human osteophytes and cells derived from them by explanation were studied. In organ-culture, the newly synthesized proteoglycan aggregated poorly with hyaluronic acid but was roughly compared to the proteoglycan aggregates derived from osteofemoral cartilage. Other characteristics of adult hyaline cartilage were preserved (i.e., high ratio of chondroitin-6-sulphate to chondroitin-4-sulphate, large hydrodynamic size and long chondroitin sulphate chains). Moderately high levels of keratan-sulphate (15-17% of the total glycosaminoglycans) were found and large keratan sulphate chains (Mr greater than 7000) confirmed by use of monoclonal antibody 1/20/5D4. Cells generated from the explants synthesized both hydrodynamically large proteoglycans and small proteoglycans. The most buoyant fraction of a CsCl density gradient (A4) contained considerable amounts of dermatan sulphate (5.2-24.4%). The Kav of the A4 fraction was 0.56 on Sepharose CL-2B and contained large glycosaminoglycan chains (Kav, 0.36 on Sepharose CL-6B). The measurements were similar to those obtained separately on osteofemoral head cartilage. These studies showed that the cartilaginous cap of human osteophytes has the capacity to synthesize the entire repertoire of sulphated proteoglycans of mature hyaline cartilage.