EXPRESSION OF TRANSFORMING-GROWTH-FACTOR-BETA-1 (TGF-BETA-1) IN THE DEVELOPING PERIODONTIUM OF RATS

Transforming growth factor-beta 1 (TGF-beta 1) has been reported to be expressed within several tissue compartments of developing molar crow ns and therefore is implicated in tooth development. Additionally TGF- beta 1 may also play a crucial role in tissue repair and regeneration. The aim of this study was to determine the distribution of TGF-beta 1 in the developing periodontal attachment apparatus (cementum, periodo ntal ligament, and alveolar bone) in Lewis rats. Animals aged 3; 6, an d 12 wks were killed, their mandibles removed, fixed; demineralized, a nd processed in paraffin. The localization of TGF-beta 1 in tissues wa s detected by polyclonal goat antibodies against human TGF-beta 1 by m eans of immunoperoxidase techniques. TGF-beta 1 messenger RNA was dete cted by in situ hybridization with a cocktail oligonucleotide probe. C ell counts were determined for analysis of the percentage of cells sta ined positive for TGF-beta 1 Results revealed that TGF-beta 1 was expr essed in the developing alveolar bone, periodontal ligament, and cemen tum 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, indic ated a similarity between the tissues obtained from different ages, bu t varied between several cell types. Cementoblasts and osteoblasts sta ined more strongly than fibroblasts. Large numbers (similar to 90%) of the osteocytes in developing bone expressed TGF-beta 1; however, in m ature bone, fewer osteocytes stained for TGF-beta 1. The percentages o f positively stained cementoblasts, osteoblasts, and fibroblasts in th e periodontal space were greater at the apical portion than at the cer vical portion of the root. TGF-beta 1 mRNA was expressed in osteoblast s, some bone marrow cells, cementoblasts, and fibroblasts, This study indicates that TGF-beta 1 may play an important role in the modulation of tissue formation and development of the periodontium.