Thymosin beta 4 is associated with RUNX2 expression through the Smad and Akt signaling pathways in mouse dental epithelial cells

Abstract

In previous studies by our group, we reported that thymosin beta 4 (Tb4) is closely associated with the initiation and development of the tooth germ, and can induce the expression of runt-related transcription factor 2 (RUNX2) during the development of the tooth germ. RUNX2 regulates the expression of odontogenesis-related genes, such as amelogenin, X-linked (Amelx), ameloblastin (Ambn) and enamelin (Enam), as well as the differentiation of osteoblasts during bone formation. However, the mechanisms through which Tb4 induces the expression of RUNX2 remain unknown. In the present study, we employed a mouse dental epithelial cell line, mDE6, with the aim to elucidate these mechanisms. The mDE6 cells expressed odontogenesis-related genes, such as Runx2, Amelx, Ambn and Enam, and formed calcified matrices upon the induction of calcification, thus showing characteristics of odontogenic epithelial cells. The expression of odontogenesis-related genes, and the calcification of the mDE6 cells were reduced by the inhibition of phosphorylated Smad1/5 (p-Smad1/5) and phosphorylated Akt (p-Akt) proteins. Furthermore, we used siRNA against Tb4 to determine whether RUNX2 expression and calcification are associated with Tb4 expression in the mDE6 cells. The protein expression of p-Smad1/5 and p-Akt in the mDE6 cells was reduced by treatment with Tb4-siRNA. These results suggest that Tb4 is associated with RUNX2 expression through the Smad and PI3K-Akt signaling pathways, and with calcification through RUNX2 expression in the mDE6 cells. This study provides putative information concerning the signaling pathway through which Tb4 induces RUNX2 expression, which may help to understand the regulation of tooth development and tooth regeneration.

Thymosin β4 is associated with bone sialoprotein expression via ERK and Smad3 signaling pathways in MDPC-23 odontoblastic cells

“…SIS3 treatment inhibits TGF-β1-induced β-catenin transcription and stabilization in mesenchymal stem cells, but these phenomena are not affected by Pd98059 treatment (14). Additionally, Tβ4 increases Runx2 expression via Smad1/5/8 and PI3K/Akt signaling to a lesser degree compared with ERK/MAPK signaling in dental epithelial cells (42). In the present study, Tβ4 increased BSP promoter activity, which was decreased by Pd98059 or SIS3 treatment in MdPc-23 cells.…”

“…cytosolic Smad2 or Smad3 translocate into the nucleus by interacting with Smad4, where they regulate the expression of genes associated with bone matrix synthesis including Runx2, ALP, cOL type I and OcN in Mc3T3-E1 cells (40,41). In a recent study, Tβ4 knockdown decreased Runx2 expression via Smad1/5/8 and PI3K/protein kinase B (Akt) signaling in dental epithelial cells (42). The results of the present study indicated that Tβ4 increased Smad3 phosphorylation and expression of Runx2, but did not increase the phosphorylation of Smad2 in MdPc-23 cells.…”

MicroRNA-449c-5p inhibits osteogenic differentiation of human VICs through Smad4-mediated pathway

“…We detected the expression of Runt-related transcription factor 2 (Runx2) after transfection with miR-449c-5p mimic and inhibitor. Runx2 is a key transcription factor associated with osteogenic differentiation 17 – 19 . The Result showed that miR-449c-5p overexpression significantly suppressed Runx2 mRNA expression while miR-449c-5p inhibitor promoted the expression of Runx2 (Fig.…”

Inhibiting actin depolymerization enhances osteoblast differentiation and bone formation in human stromal stem cells

“…Several studies have reported that the main actin binding proteins in vertebrate such as thymosin-beta 4 and profilin regulate cell differentiation, e.g. odontogenic differentiation or sternum development (Lee et al, 2013;Someya et al, 2015) related to Akt, P38, JNK, ERK, BMP pathways, followed by transcriptional regulation of Runx2 and Osterix (Lee et al, 2013;Sonowal et al, 2013;Someya et al, 2015). Since there exists over 60 families of actin-binding proteins that influence actin filament assembly/disassembly, it will be very interesting to explore the networks associated with actin assembly (composed by kinases and actin binding proteins) during different lineage commitment and differentiations of stem cells.…”