Tubular dentin formation by TGF-β/BMP signaling in dental epithelial cells

Objectives This study aimed to identify formation of tubular dentin induced by transforming growth factor-beta (TGF-beta) and bone morphogenic protein (BMP) signaling pathway in dental epithelial cells. Methods We collected conditioned medium (CM) of rTGF-beta 1/rBMP-2-treated HAT-7 and treated to MDPC-23 cells. The expression levels of odontoblast differentiation markers, KLF4, DMP1, and DSP were evaluated by real-time PCR and Western blot analysis. To evaluate whether CM of rTGF-beta 1/rBMP-2 induces tubular dentin formation, we made a beagle dog tooth defect model. Results Here, we show that Cpne7 is regulated by Smad4-dependent TGF-beta 1/BMP2 signaling pathway in dental epithelial cells. CM of rTGF-beta 1/rBMP-2 treated HAT-7 or rCPNE7 raises the expression levels of KLF4, DMP1, and DSP in MDPC-23 cells. When rTGF-beta 1 or rBMP-2 is directly treated to MDPC-23 cells, however, expression levels of Cpne7-regulated genes remain unchanged. In a beagle dog defect model, application of rTGF-beta 1/BMP2-treated CM resulted in tubular tertiary dentin mixed with osteodentin at cavity-prepared sites, while rTGF-beta 1 group exhibited homogenous osteodentin. Conclusions Taken together, Smad4-dependent TGF-beta 1/BMP2 signaling regulates Cpne7 in dental epithelial cells, and CPNE7 protein secreted from pre-ameloblasts mediates odontoblast differentiation via epithelial-mesenchymal interaction.

Automated summary

This study identified that the Smad4-dependent TGF-beta 1/BMP2 signaling pathway regulates the expression of Cpne7 in dental epithelial cells, and the CPNE7 protein mediates odontoblast differentiation through epithelial-mesenchymal interaction. The results showed that conditioned medium treated with TGF-beta 1/BMP2 can induce the formation of tubular dentin.