Expression of transforming growth factor-beta 1 (TGF-β1) in the developing periodontium of rats

Abstract

Transforming growth factor-beta 1 (TGF-beta1) has been reported to be expressed within several tissue compartments of developing molar crowns and therefore is implicated in tooth development. Additionally, TGF-beta1 may also play a crucial role in tissue repair and regeneration. The aim of this study was to determine the distribution of TGF-beta1 in the developing periodontal attachment apparatus (cementum, periodontal ligament, and alveolar bone) in Lewis rats. Animals aged 3, 6, and 12 wks were killed, their mandibles removed, fixed, demineralized, and processed in paraffin. The localization of TGF-beta1 in tissues was detected by polyclonal goat antibodies against human TGF-beta1 by means of immunoperoxidase techniques. TGF-beta1 messenger RNA was detected by in situ hybridization with a cocktail oligonucleotide probe. Cell counts were determined for analysis of the percentage of cells stained positive for TGF-beta1. Results revealed that TGF-beta1 was expressed in the developing alveolar bone, periodontal ligament, and cementum at all stages of tissue development studied. Staining was stronger at sites of cementum and alveolar bone compared with the periodontal ligament. Intensity of the positive staining, based on 3 grades, indicated a similarity between the tissues obtained from different ages, but varied between several cell types. Cementoblasts and osteoblasts stained more strongly than fibroblasts. Large numbers (approximately 90%) of the osteocytes in developing bone expressed TGF-beta1; however, in mature bone, fewer osteocytes stained for TGF-beta1. The percentages of positively stained cementoblasts, osteoblasts, and fibroblasts in the periodontal space were greater at the apical portion than at the cervical portion of the root. TGF-beta1 mRNA was expressed in osteoblasts, some bone marrow cells, cementoblasts, and fibroblasts. This study indicates that TGF-beta1 may play an important role in the modulation of tissue formation and development of the periodontium.