Localization of collagen type VI in articular cartilage of young and adult mice.

Collagen type VI was demonstrated immunomorphologically in articular cartilage (distal femur) of young (2-8 weeks) and adult mice by fluorescence and electron microscopy (gold-labelled second antibody--sandwich method) using pre- and post-embedding techniques. This collagen type was mainly seen in the vicinity of chondrocytes, and in larger amounts in adult cartilage. Electron-microscopic inspection (pre-embedding technique) revealed labelling above plaques that were 40-160 nm in size, and from which up to 7 fine filaments (< or = 10 nm) per unit sectional plane radiated. Using the post-embedding technique, only labelled plaques could be demonstrated; fine filaments were not perceptible. This was partly a result of the low contrast. It is assumed that the globular ends of up to 20 of the fine type VI filaments are anchored in one plaque and that the antibodies bind to the non-collagenous globular domains. Filaments radiated from the plaques and formed a three-dimensional network that stabilized the structures of the cartilaginous matrix. Antibodies against fibronectin also labelled similar plaques. The ends of the type VI filaments are possibly linked into the plaques by fibronectin.