Material properties and biosynthetic activity of articular cartilage from the bovine carpo-metacarpal joint

Abstract

Objective: To determine the site variation of material properties and cellular biosynthetic activity, and to compare these at each site, of articular cartilage from the bovine carpo-metacarpal joint in order to test its usefulness as a model system for investigating the metabolic effects of mechanical stimuli. Design: The mechanical properties and composition of full-depth biopsies of articular cartilage were measured at defined sites in bovine carpometacarpal joints. Metabolic activity at the same sites was assessed by incubating further biopsies in medium containing 35S-sulfate and 3H-leucine then measuring the incorporated radioisotope and cell density. These results were compared with an estimate of the distribution of forces across the joint. Results: Topographical variation of water content, stiffness, cell count or incorporated radioisotope was not significant whereas collagen and glycosaminoglycan varied in different ways. A moderate correlation was found between water and collagen contents, but the correlation between water and glycosaminoglycan contents was poor. Neither compressive stiffness nor creep compliance was predicted strongly by any of the composition measurements. A negative correlation was found between metabolic activity and cell density. Conclusions: Defining the variation of tissue properties across the bovine carpometacarpal joint and the lack of variation in biosynthetic activity will enable proper matching of experimental and control groups of biopsies in studies of the effects of mechanical stimuli on the composition and mechanical properties of articular cartilage. In addition, the lack of correlation between stiffness, water and glycosaminoglycan contents is further evidence that the mechanical properties of the tissue depend significantly on factors other than these broad measures of composition.