The soft tissue cover of the mandibular condyle: age-related changes in high buoyant density proteoglycans, free tissue water and remodelling activity.

Age-related changes in the relative proportion of high buoyant density proteoglycans of the soft tissue cover of the mandibular condyle of domestic pigs and the chemical composition of these proteoglycans were investigated by biochemical methods. The relative proportion of high buoyant density proteoglycans has been shown to decrease with age, with their chemical composition varying as follows: With age, the relative proportions of protein increased, galactosamine decreased, glucosamine was similar in newborns and juveniles, but clearly increased in adults, galactosamine plus glucosamine decreased. As measured by 1H-NMR-relaxation spectroscopic methods, the concentration of free tissue water of the soft tissue cover of the mandibular condyle decreased with age. Its mobility, however, was greater in newborns than in juveniles, but similar in juveniles and adults. The concentration of free tissue water, but not its mobility, correlated weakly with relative proportions of polyanionic side chains (e.g. chondroitin sulphate plus keratan sulphate chains) of the high buoyant density proteoglycans. By affecting the concentration of free tissue water and in turn of matrix solutes and cellular environments, the high buoyant density proteoglycans of the soft tissue cover of the mandibular condyle seem to be involved in regulation of age-related changes in the adaptive remodelling activity of the mandibular condyle.