Detection of collagenase mRNA in odontoclasts of bovine root-resorbing tissue by in situ hybridization.

The odontoclast, which is morphologically similar to osteoclast, is thought to play a major role in root resorption of deciduous teeth. High collagenolytic activity has been detected in the root resorbing tissue. In order to identify collagenase-producing cells and the role of collagenase in root resorption of deciduous tooth, in situ hybridization of collagenase mRNA in bovine root-resorbing tissue sections was performed using a digoxigenin-labeled, nonradioactive RNA probe. Collagenase mRNA expression was clearly observed in odontoclasts in addition to the macrophages, fibroblasts, odontoblasts, and cementoblasts. Multinuclear odontoclasts showed intense tartrate-resistant acid phosphatase (TRAP) activity. We also examined interleukin-1 (IL-1) mRNA expression in the root-resorbing tissue by in situ hybridization. IL-1 transcripts were found to be expressed in odontoclasts, fibroblasts, and macrophages suggesting that IL-1 might be an important factor for promoting root resorption. These results suggest that the collagenase produced by odontoclasts may play a key role in dentin collagen degradation in root resorption.