The distribution of type VI collagen in the developing tissues of the bovine femoral head

Type VI collagen appears central to the maintenance of tissue integrity. In adult articular cartilage, type VI collagen is preferentially localised in the chondron where it may be involved in cell attachment. In actively remo delling developing cartilage, the distribution is less certain. We have use d confocal immunohistochemistry and in situ hybridisation to investigate ty pe VI collagen distribution in third trimester bovine proximal femoral epip hyses. In general, type VI collagen immunofluorescence was concentrated in the chondrocyte pericellular matrix, with staining intensity strongest in r egions which persist to maturity and weakest in regions that remodel during development. Type VI collagen was also present in cartilage canals. In the growth plate and around the secondary centre of ossification, the intensit y of type VI collagen stain rapidly decreased with chondrocyte maturation a nd was absent at hypertrophy, except where canal branches penetrated the gr owth plate and stain was retained around the adjacent chondrocytes. In situ hybridisation confirmed the presence of type VI collagen mRNA in cartilage canal mesenchymal cells but the signal was low in chondrocytes, suggesting minimal levels of synthesis and turnover. The results are consistent with a role for type VI collagen in stabilising the extracellular matrix during development.