Signaling transduction pathway of TGF-β1 and its effect on differention of human dental pulp cell

Aim: Transforming growth factor β1 (TGF-β1) plays a role in repair and dentinogenesis in dental pulp cells. The purpose of this study is to investigate whether TGF-β1 stimulates the two signaling pathways, MEK/ERK and Smad2 to mediate Runx2 expression, collagen matrix deposition and alkaline phosphatase in human dental pulp cells.aterials and Methods: Primary-cultured human dental pulp cells were treated with TGF-β1. in some experiments, cells were pretreated with U0126 (a MEK/ERK inhibitor), Noggin (a BMP antagonist), or SB431542 (an ALK5/ Smad 2/3 inhibitor) 30 minutes before adding TGF-β1. Signaling of TGF-β1 was investigated by western-blot assay. Cell proliferation was evaluated by MTT assay. Cell differentiation and mineralization was evaluated by alkaline phosphatase (ALP) staining. Changes in mRNA expression were determined by reverse-transcriptase polymerase chain reaction (RT-PCR). Collagen content was determined by Sircol Collagen assay.esults: In human dental pulp cell, TGF-β1 induce the expression of ERK, Smad 2, Smad 1/5/8 signaling. Cell under the treatment of TGF-β1 (5 ng/ml & 10 ng/ml) showed a decrease in ALP activity and gene expression of ALP and Runx-2. TGF-β1 (5 ng/ml) induced collagen formation in dental pulp cell. Pretreatment of U0126 (a MEK/ERK inhibitor) and Noggin (a Smad 1/5/8 inhibitor) was not effective to prevent these events. SB431542 (an ALK5/ Smad 2/3 inhibitor) attenuate the TGF-β 1-induced decline of ALP activity and Runx-2 expression. In conclusion, TGF-β1 down-regulates Runx-2 and ALP activity of human dental pulp cells via ALK5/Smad2/3 signaling.onclusion: Signal transduction of TGF-β1 in human dental pulp cell is complex. In addition to the well-known Smad2/3 pathway, Smad 1/5/8 and MAPK/ERK also take part in this complex system. These events are crucial in the mechanism of pulpal repair and regeneration.