The 7D4, 4C3 and 3B3 (-) Chondroitin Sulphation Motifs are expressed at Sites of Cartilage and Bone Morphogenesis during Foetal Human Knee Joint Development

Abstract

Novel sulphation motifs within the glycosaminoglycan (GAG) chain structure of chondroitin sulphate (CS)- containing s are associated with sites of growth and differentiation in many biological systems where they function as molecular recognition sites involved in the binding, sequestration or presentation of soluble signalling molecules (e.g. growth factors, cytokines, morphogens). The specific sulphation motifs on CS identified by monoclonal antibodies 3-B-3(-), 4-C-3 and 7-D-4 are also associated with distinct cohorts of cells in areas of tissue morphogenesis in human foetal knee joint development. We hypothesize that such motifs may have roles to play in the regulation of proliferative/differentiative events during tissue morphogenesis. In the present investigation we have examined the distribution of these CS motifs within the rudiment cartilage, stromal connective tissues surrounding the rudiment cartilages and developing growth plates of the human foetal knee joint. These CS motifs had broad, overlapping distributions throughout the differentiating connective tissues undergoing morphogenesis and after joint cavitation were localised very specifically to the rudiment cartilage destined to form the permanent articular cartilage postnatally, and to the terminally differentiated chondrocytes and calcified cartilage-bone interface in the growth plate cartilages. The overlapping distributions of these molecules within the presumptive articular cartilage, prior to secondary ossification, suggests that they participate in early signalling events involved in tissue development and indicates that the cells within this zone are phenotypically distinct from those of the underlying rudiment cartilage.