Identification of matrix metalloproteinases and their inhibitor in the articular disc of the craniomandibular joint of the rabbit

Connective tissue cells synthesize and secrete matrix metalloproteinases (MMPs), a family of matrix-degrading enzymes (comprising collagenases, gelatinases and stromelysins), which are capable of degrading all the constituent molecules of connective tissues at physiological pH. This investigation documents the synthesis and distribution of MMPs and their inhibitor TIMP-1 (tissue inhibitor of metalloproteinases-1) in the developing articular disc of the craniomandibular joint of the rabbit using indirect immunofluorescence microscopy. Cells of the disc synthesized all three classes of MMPs as well as TIMP-1 in all regions of the disc at all stages examined. MMPs and TIMP-1 were detected as bright intracellular accumulations probably within Golgi vesicles and as occasional diffuse, matrix-bound deposits. These results suggest that MMP-mediated matrix remodelling is a prominent feature of growth in craniomandibular joint disc.