EXPRESSION OF INTERSTITIAL COLLAGENASE IS RESTRICTED TO SKELETAL TISSUE DURING MOUSE EMBRYOGENESIS

Collagenases are thought to be involved in physiological and pathologi cal processes that require extracellular matrix remodeling. Using the in situ hybridization technique, we describe the expression of interst itial collagenase gene during mouse embryogenesis between E6.5 and E17 . We demonstrate that interstitial collagenase expression is exclusive ly detected in one event, namely the onset of bone formation, Transcri pts accumulate in hypertrophied chondrocytes, found in the mature cart ilaginous matrix of long-bone growth plates or ribs, and in osteoblast s and/or in endothelial cells that have migrated into the shafts of de veloping long bones, The expression of the tissue inhibitor of metallo proteinases (TIMP-2) gene precedes the expression of interstitial coll agenase in developing bones, These data suggest that interstitial coll agenase plays a specific role in bone development and that the tight r egulation of its activity during development is achieved not only by p ost-translational mechanisms with TIMPs, as previously suggested, but also at the transcriptional level.