Regional andtemporal changes inthesynthesis ofmatrix metalloproteinas es andTIMP-1during development ofthe rabbit mandibular condyle

Connective tissues synthesise andsecrete afamily ofmatrix metalloproteinases (MMPs;collagenases, gelatinases andstromelysins) capable ofdegrading allthecomponents ofconnective tissue matrices at physiological pH.We document thepatterns ofsynthesis anddistribution ofMMPs andthetissue inhibitor ofmetalloproteinases-1 (TIMP-1) within thedeveloping rabbit mandibular condyle using immunofluorescence microscopy. MMPs andTIMP-1weredetected bothasbright intracellular accumulations within Golgi vesicles andalso asdiffuse matrix-bound extracellular deposits. Cells inthe articular zone, proliferative zone, condylar cartilage andboneofthemandibular ramuswereshownto produce all3classes ofMMPs andTIMP-1withtheexception ofstromelysin, which wasnotsynthesised by cells oftheboneofspongiosum. Temporal synthesis ofMMPs andTIMP-1within these regions varied during theperiod 18dpostcoitum to14dpostnatum. Ourresults document unique patterns ofMMP and TIMP-1synthesis during embryonic andearly postnatal development ofcondylar cartilage andsupport the concept that cells synthesise andsecrete MMPs andTIMP-1before undergoing proliferation and hypertrophy. A comparison ofthese results withdataintherabbit growth plate showmanysimilarities, but somedifferences exist that probably reflect differences inthemodesofgrowth ofthe2cartilages.