TGF-β-Operated Growth Inhibition and Translineage Commitment into Smooth Muscle Cells of Periodontal Ligament-Derived Endothelial Progenitor Cells through Smad- and p38 MAPK-Dependent Signals

Abstract

The periodontal ligament (PDL) is a fibrous connective tissue that attaches the tooth to the alveolar bone. We previously demonstrated the ability of PDL fibroblast-like cells to construct an endothelial cell (EC) marker-positive blood vessel-like structure, indicating the potential of fibroblastic lineage cells in PDL tissue as precursors of endothelial progenitor cells (EPCs) to facilitate the construction of a vascular system around damaged PDL tissue. A vascular regeneration around PDL tissue needs proliferation of vascular progenitor cells and the subsequent differentiation of the cells. Transforming growth factor-β (TGF-β) is known as an inducer of endothelial-mesenchymal transition (EndMT), however, it remains to be clarified what kinds of TGF-β signals affect growth and mesenchymal differentiation of PDL-derived EPC-like fibroblastic cells. Here, we demonstrated that TGF-β1 not only suppressed the proliferation of the PDL-derived EPC-like fibroblastic cells, but also induced smooth muscle cell (SMC) markers expression in the cells. On the other hand, TGF-β1 stimulation suppressed EC marker expression. Intriguingly, overexpression of Smad7, an inhibitor for TGF-β-induced Smad-dependent signaling, suppressed the TGF-β1-induced growth inhibition and SMC markers expression, but did not the TGF-β1-induced downregulation of EC marker expression. In contrast, p38 mitogen-activated protein kinase (MAPK) inhibitor SB 203580 suppressed the TGF-β1-induced downregulation of EC marker expression. In addition, the TGF-β1-induced SMC markers expression of the PDL-derived cells was reversed upon stimulation with fibroblast growth factor (FGF), suggesting that the TGF-β1 might not induce terminal SMC differentiation of the EPC-like fibroblastic cells. Thus, TGF-β1 not only negatively controls the growth of PDL-derived EPC-like fibroblastic cells via a Smad-dependent manner but also positively controls the SMC-differentiation of the cells possibly at the early stage of the translineage commitment via Smad- and p38 MAPK-dependent manners.

FGF2 inhibits endothelial–mesenchymal transition through microRNA-20a-mediated repression of canonical TGF-β signaling

“…These data indicate that active endothelial TGFβ signaling through ALK5 and the Smad2 and Smad3 transcription factors is associated with EndMT and confirms previous data reported by us and others (Kokudo et al, 2008;Krenning et al, 2008;Moonen et al, 2010;Medici et al, 2010Medici et al, , 2011Yoshida et al, 2012).…”

Dkk1 and Msx2–Wnt7b Signaling Reciprocally Regulate the Endothelial–Mesenchymal Transition in Aortic Endothelial Cells

“…Smad transcription factor pathway activation is a consistent molecular mediator of both EndMT 35 and osteogenic mineralization 36 , 37 , signaling downstream of ALK receptor activation. We posited that the responses induced by SFG-Dkk1 transduction of AoECs might be dependent upon these same Smad-dependent signaling pathways.…”

EGF Positively Regulates the Proliferation and Migration, and Negatively Regulates the Myofibroblast Differentiation of Periodontal Ligament-Derived Endothelial Progenitor Cells through MEK/ERK- and JNK-Dependent Signals

“…As described above, the expression of α-SMA in the tensed-side of PDLs was induced during orthodontic tooth movement in 6-week male rats [10], suggesting that PDL fibroblasts might possess the potential to differentiate into MFs in response to mechanical tensile force loading. Intriguingly, we previously demonstrated elevated expressions of the MF markers α-SMA and h1-calponin in the PDL-derived EPC-like SCDC2 cells following stimulation with TGF-β1 [8], suggesting that PDL tissue contains progenitor cells of differentiated MFs that can play important roles in remodeling fibrous tissues in PDL by producing ECM molecules such as type I collagen.…”

“…Intriguingly SCDC2 cells, which abundantly expressed the EC marker Tie-2, vigorously constructed blood vessel structures in a three-dimensional type I collagen scaffold, suggesting that SCDC2 cells retain endothelial progenitor cell (EPC)-like characteristics. In addition, SCDC2 cells expressed not only the EC markers Tie-2, von Willebrand factor (vWF), and CD31 but also the myofibroblast (MF) markers alpha-smooth muscle actin (α-SMA), h1-calponin, and collagen type I alpha 1 (colIα1) [7,8], which suggests that SCDC2 cells may possess MF-like characteristics, which allow them to participate in remodeling of fibrous tissue networks in PDL tissue. MFs are known to arise from undifferentiated mesenchymal cells and are responsible for collagen turnover at the site of fibrous tissue remodeling [reviewed in [9]]: MF expands fibrous tissue by the formation of the collagen network.…”