Increased metabolism of collagen VI in canine osteoarthritis.

The integrity of joint function depends on both the extracellular matrix and the chondrocytes of articular cartilage. It has been suggested that there is a reciprocal relationship between these two components, which is altered in osteoarthritis. The immunohistochemical distribution of type VI collagen in normal and osteoarthritic canine cartilage was investigated by immunofluorescence and immunoelectron microscopy. Immunogold labelling showed that in normal cartilage type VI collagen was concentrated in the capsule adjacent to the chondrocyte complex. However, in osteoarthritic cartilage, type VI collagen was also observed throughout the cartilage matrix and was greatly increased in the territorial matrix and pericellular capsule surrounding the chondrocytes. Naturally occurring canine osteoarthritis provides a useful model for the study of the human disease, particularly the early stages. The changes in type VI collagen observed in osteoarthritis suggest an attempt at cartilage repair, resulting in the reorganization of the matrix.