Immunohistochemical localization of connective tissue growth factor, transforming growth factor-beta1 and phosphorylated-smad2/3 in the developing periodontium of rats

Connective tissue growth factor (CTGF) is a downstream mediator of transforming growth factor-beta1 (TGF-β1), and TGF-β1-induced CTGF expression is regulated through the SMAD pathway. CTGF is implicated in the development of cartilage, bone and tooth. However, its expression in the developing periodontium is unclear. Therefore, we aimed to investigate the immunolocalization of CTGF, TGF-β1 and phosphorylated SMAD2/3 (pSMAD2/3) in the developing periodontium of rats.

The maxillaries of Wistar rats, 2, 3, 7 and 12 wk of age, were used and the localization of CTGF, TGF-β1 and pSMAD2/3 was detected using immunoperoxidase techniques.

Hertwig' s epithelial root sheath (HERS) cells were strongly positive for CTGF and TGF-β1, but not for pSMAD2/3. Positive staining for CTGF, TGF-β1 and pSMAD2/3 was found in bone and periodontal ligament. In cementum, most cementoblasts associated with cellular cementum and some cementocytes stained strongly for CTGF, whereas cementoblasts associated with acellular cementum did not express CTGF. No signal for TGF-β1 was observed in cellular and acellular cementum. In addition, most cementocytes were strongly positive for pSMAD2/3.

CTGF, TGF-β1 and pSMAD2/3 are localized in bone and periodontal ligament, but are differentially expressed in HERS and cementum. The results of our study indicate that the regulation of CTGF expression by TGF-β1 might be cell-type specific in periodontium.