Expression of interstitial collagenase during skeletal development of the mouse is restricted to osteoblast-like cells and hypertrophic chondrocytes.

We determined the expression pattern of the matrix metalloproteinase interstitial collagenase (MMP-1) during mouse embryo development using in situ hybridization and immunohistochemistry. Localized MMP-1 mRNA was first detected at 14.5 days postconceptus. The spatial and temporal expression was restricted to areas of endochondral and intramembranous bone formation, such as in the mandibula, maxilla, clavicle, scapula, in the vertebrae, and in the dorsal, but not the ventral part of the ribs. The highest levels of MMP-1 transcripts and MMP-1 protein were found in the metaphyses and diaphyses of the long bones. MMP-1 was expressed by hypertrophic chondrocytes and by osteoblastic cells localized along the newly formed bone trabeculae. No expression was detected in osteoclasts. Two other related members of the MMP family, stromelysin-1 (MMP-3) and stromelysin-2 (MMP-10), were not expressed during days 7.5 and 16.5 of mouse embryogenesis. The tissue-specific expression of MMP-1 and the exclusive ability of interstitial collagenase to digest native collagen of types I, II, III, and X, the major components of bone, cartilage, and tendon, strongly suggests an important and specific function of this enzyme in bone development and remodeling.