Kinetics of release of aggrecan from explant cultures of bovine cartilage from different sources and from animals of different ages

Abstract

It is the presence of aggrecan trapped as a complex with hyaluronan and link protein within the collagen fibres that gives articular cartilage its unique biomechanical properties of being able to withstand compressive loads (Maroudas 1980). The chondrocytes are responsible for the synthesis and catabolism of aggrecan complexes in the extracellular matrix of cartilage. In normal tissue the concentration of aggrecan complexes in the extracellular matrix is maintained at a constant level (Handley et al. 1990). It has been shown that when articular cartilage is exposed to retinoic acid or interleukin-1 there is an elevated rate of loss of aggrecan from the tissue (llic et al. 1992). Work utilising explant cultures of cartilage has shown that the catabolism of aggrecan in cultures exposed to either retinoic acid or interleukin-1 involves the cleavage of the core protein of this proteoglycan at a distinct site within the interglobular domain (Sandy et al. 1991, Ilic et al. 1992). Little is known about the kinetics of loss of aggrecan from cartilage and how this varies with the source of tissue and the age of the animal that the tissue is derived from. This paper describes the kinetics of loss of both the chemical and radiolabeled pools of aggrecan present in explant cultures of bovine articular and nasal septum from foetal and mature animals maintained in the presence and absence of retinoic acid.