Transforming growth factor-beta1 (TGF-beta1) is known to be a potent inducer of odontoblast differentiation and dentin synthesis. Objective: In order to determine how TGF-beta1 signal is transduced and modulated within human odontoblasts, we compared the gene expression profiles of odontoblast precursor pulp cells (OPPC) and odontoblasts differentiated in vitro. Methods: We used 96 gene-containing DNA arrays (“TGF/BMP Signaling Pathway Gene Array”, SuperArray, Frederick, MD, USA) that contain genes directly involved in signaling downstream of TGF-beta1, genes modulating TGF-beta1 signaling pathway at various levels, and genes whose expression is known to be regulated by TGF-beta1. Results: About thirty genes were found to be expressed in OPPC and odontoblasts in vitro, including Smad-2 and -4, c-Jun, ecotropic viral integration site -1 (Evi-1), TGFbeta-induced factor (TGIF), inhibitors of DNA binding-3 and -4, goosecoid, type III collagen alpha 1 chain (COL3A1), and TGF-beta1 itself. Profile comparison of odontoblasts and OPPC revealed low expression levels of COL3A1, Evi-1 and TGIF genes in odontoblasts and a higher level of the TGF-beta1 gene. Statistical analysis with Student's t test revealed significant differences for COL3A1 (x 3.14; p ≤ 0.01), Evi-1 (x 7.67; p ≤ 0.01) and TGF-beta1 (x 90; p ≤ 0.007). Similar results were obtained by the use of semi-quantitative RT-PCR. Expression of these genes was also detected in in vivo human pulp samples by the same methodologies. Conclusions: The various molecules identified in this study suggest that TGF-beta1 signaling is finely regulated in human dental pulp cells, including odontoblasts. Our study provides a valuable basis for the further analysis of fine mechanisms involved in odontoblast differentiation induced by TGF-beta1.

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