Kyushu University Academic Staff Educational and Research Activities Database
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Mitarai Hiromi Last modified date:2024.05.13

Assistant Professor / Department of General Dentistry
Comprehensive Dentistry
Kyushu University Hospital

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Undergraduate School
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 Reseacher Profiling Tool Kyushu University Pure
Division of General Dentistry, Kyushu University Hospital .
Academic Degree
Doctor of Dental Science
Country of degree conferring institution (Overseas)
Field of Specialization
General Dentistry, Endodontology
Total Priod of education and research career in the foreign country
Research Interests
  • Development of new periodontal ligament regeneration therapy
    keyword : periodontal ligament, stem cell, exosome
  • The effect of Transgelin on homeostasis of human periodontal ligament cells
    keyword : human periodontal ligament cells
Academic Activities
1. NaatiFakatava, HiromiMitarai, AsukaYuda, AkiraHaraguchi, HirokoWada, DaigakuHasegawa, HidefumiMaeda, NaohisaWada, Actin alpha 2, smooth muscle, a transforming growth factor-β1-induced factor, regulates collagen production in human periodontal ligament cells via Smad2/3 pathway, J Dent Sci, 2023.04, Background/purpose: Actin alpha 2, smooth muscle (ACTA2) is an actin isoform that forms the cytoskeleton. Actin plays a crucial role in numerous cellular functions. ACTA2 is a marker of functional periodontal ligament (PDL) fibroblasts and is upregulated by transforming growth factor-β1 (TGF-β1); however, the underlying function of ACTA2 in PDL tissue is unknown. We aimed to examine the localization and potential function of ACTA2 in PDL tissues and cells.

Materials and methods: RNA expression was determined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and quantitative RT-PCR. Protein expression was determined using immunofluorescence staining and Western blot analysis. Soluble and insoluble collagen production was examined using the Sircol collagen assay and picrosirius red staining, respectively. Small interfering RNA (siRNA) was used for knockdown assay to examine the effect of ACTA2 in human PDL cells.

Results: ACTA2 expression was observed in human primary PDL cells and PDL cell line (2-23 cells). TGF-β1 upregulated ACTA2, collagen type Ⅰ alpha1 chain (COL1A1), periostin (POSTN), and fibrillin-Ⅰ(FBN1) expression and soluble and insoluble collagen production in 2-23 cells. However, ACTA2 depletion by siRNA strongly suppressed PDL-related gene expression and collagen production compared with those of TGF-β1-stimulated control cells. Furthermore, ACTA2 knockdown significantly suppressed the phosphorylation of Smad2 and Smad3.

Conclusion: ACTA2 plays a crucial role in PDL-related marker expression and collagen production via Smad2/3 phosphorylation. Our findings might contribute to the development of novel and effective periodontal therapies..
2. Hiromi Mitarai, Naohisa Wada, Daigaku Hasegawa, Shinichiro Yoshida, Mai Arima, Atsushi Tomokiyo, Sayuri Hamano, Suguru Serita, Hiroyuki Mizumachi, Hidefumi Maeda, Transgelin mediates transforming growth factor-β1-induced proliferation of human periodontal ligament cells., Journal of periodontal research., 10.1111/jre.12466, 52, 6, 984-993, 2017.12, BACKGROUND AND OBJECTIVE:
Human periodontal ligament cells (HPDLCs) express transforming growth factor-β1 (TGF-β1) that regulates differentiation and proliferation, and plays key roles in homeostasis of PDL tissue. Transgelin is a cytoskeleton-associated protein with an Smad-binding element in its gene promoter region. In this study, we examined the localization and potential function of transgelin in PDL tissue and cells.

Microarray analysis of HPDLC lines (2-14, 2-23 and 2-52) was performed. Expression of transgelin in HPDLCs was examined by quantitative reverse transcription-polymerase chain reaction, immunofluorescence staining and western blot analysis. Effects of TGF-β1 and its signaling inhibitor, SB431542, on transgelin expression in HPDLCs were examined by western blot analysis. The effects of transgelin knockdown by small interfering RNA (siRNA) on HPDLC proliferation stimulated by TGF-β1 were assessed by WST-1 assay.

In microarray and quantitative reverse transcription-polymerase chain reaction analyses, the expression levels of transgelin (TAGLN) in 2-14 and 2-23 cells, which highly expressed PDL markers such as periostin (POSTN), tissue non-specific alkaline phosphatase (ALPL), α-smooth muscle actin (ACTA2) and type I collagen A1 (COL1A1), was significantly higher than those in 2-52 cells that expressed PDL markers weakly. Immunohistochemical and immunofluorescence staining revealed expression of transgelin in rat PDL tissue and HPDLCs. In HPDLCs, TGF-β1 treatment upregulated transgelin expression, whereas inhibition of the type 1 TGF-β1 receptor by SB431542 suppressed this upregulation. Furthermore, TAGLN siRNA transfection did not promote the proliferation of HPDLCs treated with TGF-β1. The expression levels of CCNA2 and CCNE1, which regulate DNA synthesis and mitosis through the cell cycle, were also not upregulated in HPDLCs transfected with TAGLN siRNA.

Transgelin is expressed in PDL tissue and might have a role in HPDLC proliferation induced by TGF-β1 stimulation..
1. Fakatava Naati、御手洗裕美、祐田明香、長谷川大学、前田英史、和田尚久, The Role of Acta2 in Periodontal Ligament cell stimulated with TGF-β1, 日本歯科保存学会, 2020.06.