Hypothesis: can type IX collagen "glue" together intersecting type II fibers in articular cartilage matrix? A proposed mechanism.

Type IX collagen is crosslinked to the surface of type II collagen molecules, and has been proposed as the glue that binds the collagen network of cartilage matrix. However, there is as yet no evidence that the crosslinks that have been described to date provide interfibrillar connections, and the only mechanism proposed for such connections between intersecting fibers is unlikely on stereochemical grounds. We propose that both type IX collagen and an intermediary molecule are necessary for network stabilization and that proteoglycans are likely candidates for the role of intermediary.