Localization of pro-collagen type ii mrna and collagen type ii in the healing tooth socket of the rat

Sprague-Dawley rats (50 days old) were anaesthetized and the maxillary right molars extracted. The rats were killed at 2, 3, 6, 8 and 10 days after extraction. The maxillae were dissected and prepared for either routine histology, in situ hybridization for pro-collagen type II mRNA, or immunohistochemical detection of collagen type II. Pro-collagen type II mRNA was expressed maximally in the healing tooth socket at 8 days after the extractions, but the protein was not expressed at any time. This suggests that the translation of pro-collagen type II mRNA does not occur in osteoblasts following tooth extraction. Ossification was present in the socket at 6 days after the extractions, which is consistent with the suggestion that an early feature of osteoblastic differentiation may be the expression of type II pro-collagen mRNA.