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

• Published in: International journal of biological sciences 2012-01, Vol.8 (7), p.1062-1074
• Main Authors: Yoshida, Mariko, Okubo, Naoto, Chosa, Naoyuki, Hasegawa, Tomokazu, Ibi, Miho, Kamo, Masaharu, Kyakumoto, Seiko, Ishisaki, Akira
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; Cell Proliferation - drug effects; Cells, Cultured; Endothelial Cells - cytology; Endothelial Cells - drug effects; Fluorescent Antibody Technique; Myocytes, Smooth Muscle - cytology; Myocytes, Smooth Muscle - drug effects; Myocytes, Smooth Muscle - metabolism; p38 Mitogen-Activated Protein Kinases - metabolism; Periodontal Ligament - cytology; Rats; Research Paper; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction - drug effects; Smad Proteins - metabolism; Stem Cells - cytology; Stem Cells - drug effects; Transforming Growth Factor beta - pharmacology
• ISSN: 1449-2288; 1449-2288
• DOI: 10.7150/ijbs.4488

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.