The signal transduction pathway of TGF-β1 and its effect on the growth and differentiation of dental pulp stem cells from human exfoliated deciduous teeth
Date Issued
2012
Date
2012
Author(s)
Chen, I-Li
Abstract
Aim : Transforming growth factor-β1 (TGF-β1) regulates many biological process and is thought to be important in response to dental tissue injury. Dental pulp stem cells
from human exfoliated deciduous teeth (SHED) were discovered in the recent ten years and considered a desirable stem cell source. The purpose of this study is to investigate the effects of TGF-β1 on SHED. We hypothesize that TGF-β1 can affect cell viability, collagen production and alkaline phosphatase (ALP) expression in SHED via both
Smad and non-Smad MAPK pathway, which might have cross-talk with each other.
Materials and Methods : Primary-cultured SHED were treated with different concentration of TGF-β1. We used MTT assay, Sircol Collagen assay, ALP staining and ALP activity quantitative assay to detect the effect of TGF-β1 on cell viability, matrix formation, and cell differentiation. Besides, SHED were pretreated with SB431542 (an
ALK5-Smad2/3 inhibitor), U0126 (a MEK-ERK1/2 inhibitor), 5Z-7-Oxozeaenol (a TAK1 inhibitor), or SB203580 (a p38 MAPK inhibitor) for examining the related signaling pathways. Phosphorylation of Smad2 was examined by Enzyme-linked
immunosorbent assay (ELISA) for evaluating the cross-talk within the Smad and non-Smad MAPK pathway. Changes in mRNA expression were determined by reversetranscription Polymerase Chain Reaction (RT-PCR).
Results : TGF-β1 stimulated cell proliferation and matrix production of SHED in a dose-dependent manner, which could be reversed by pretreatment of SB431542, 5Z-7-Oxozeaenol and SB203580; nevertheless, it was not suppressed by U0126. In cell differentiation, low concentration of TGF-β1 (0.5-1 ng/ml) up-regulated the ALP activity of SHED, whereas high concentration (5-10 ng/ml) down-regulated its
expression. SB431542 could reverse the effect of TGF-β1 at both low and high concentrations. SB203580 itself down-regulated ALP activity significantly; however, 5Z-7-Oxozeaenol only reversed the effect of TGF-β1 in low concentration. Concerning the signal transduction, the expression of phospho-Smad2, which was quickly induced
by TGF-β1 and repressed by SB431542, was found to be completely abolished by 5Z-7-Oxozeaenol.
Conclusion : The regulation about signal transduction of TGF-β1 in SHED is complicated. In addition to the cross-talk of Smad and non-Smad pathway, different
concentration of TGF-β1 can mediate different cell response via different signaling pathways. These results are crucial to the mechanism of pulpal repair, that can be useful for further investigation of pulpal regeneration.
Subjects
SHED
TGF-β1
Smad
Alkaline phosphatase
Type
thesis
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