👤 Chihiro Nakatomi

Orthodontic treatment enables tooth movement through bone remodeling. The effects of fibroblast growth factor 2 (FGF2) on human periodontal ligament fibroblasts (HPdLFs) in response to mechanical stimulation that occurs during orthodontic treatment remain unexplained. We investigated the effects of FGF2 and mechanical stress on HPdLF differentiation, focusing on cementoblast differentiation. The effects of FGF2 and mechanical stress (applied for 24 hours using a centrifuge) on HPdLFs were evaluated. Changes in marker levels were assessed using real-time reverse transcriptase-polymerase chain reaction and western blotting. Furthermore, the effect of FGF2 treatment on HPdLF mineralization was assessed after 3 and 5 weeks using Alizarin red S staining (BMK-R009: Bio Future Technologies, Tokyo, Japan). Treatment of HPdLFs with 20 ng/mL FGF2 increased the expression of CEMP1 and RUNX2 but did not significantly alter the expression of FGF2, FGFR1, and FGFR2. In HPdLFs exposed to mechanical stress, expression of FGFR1 and OCN was increased, whereas that of FGF2, CEMP1, CAP, GLUT1, ALP, and OPN was reduced considerably. Treatment of mechanically-stressed HPdLFs with FGF2 did not change FGF2 expression, but expression of FGFR1, CEMP1, CAP, and GLUT1 increased significantly. In addition, FGFR1 was significantly upregulated at the protein level, whereas cementoblast differentiation markers showed an upward trend. Mineralization showed no changes at 3 weeks. However, at 5 weeks, considerable mineralization was observed in mechanically-stressed cells continuously exposed to FGF2. Mechanical stress increases FGFR1 expression in HPdLFs. FGF2 promotes the differentiation of mechanical-stressed HPdLFs into cementoblasts and their mineralization. Show less

Apert syndrome is characterized by craniosynostosis and bony syndactyly of the hands and feet. The cause of Apert syndrome is a single nucleotide substitution mutation (S252W or P253R) in fibroblast growth factor receptor 2 (FGFR2). Clinical experience suggests increased production of saliva by Apert syndrome patients, but this has not been formally investigated. FGFR2 signaling is known to regulate branching morphogenesis of the submandibular glands (SMGs). With the Apert syndrome mouse model (Ap mouse), we investigated the role of FGFR2 in SMGs and analyzed the SMG pathology of Apert syndrome. Ap mice demonstrated significantly greater SMG and sublingual gland (SMG/SLG complex) mass/body weight and percentage of parenchyma per unit area of the SMG compared with control mice. Furthermore, gene expression of Fgf1, Fgf2, Fgf3, Pdgfra, Pdgfrb, Mmp2, Bmp4, Lama5, Etv5, and Dusp6 was significantly higher in the SMG/SLG complex of Ap mice. FGF3 and BMP4 exhibited altered detection patterns. The numbers of macrophages were significantly greater in SMGs of Ap mice than in controls. Regarding functional evaluations of the salivary glands, no significant differences were observed. These results suggest that the gain-of-function mutation in FGFR2 in the SMGs of Ap mice enhances branching morphogenesis. Developmental Dynamics 247:1175-1185, 2018. © 2018 Wiley Periodicals, Inc. Show less

The Hey family (also known as Chf, Herp, Hesr, and Hrt) is a set of Hairy/Enhancer of Split-related basic helix-loop-helix type transcription factors. Hey1, Hey2, and HeyL have been identified in mammals. Although Hey proteins are known to regulate cardiovascular development, muscle homeostasis, osteogenesis, neurogenesis, and oncogenesis, their roles in tooth development have been largely obscure. Therefore, this study aimed to clarify detailed spatiotemporal expression patterns of Hey1 and Hey2 in developing molars and incisors of mice by section in situ hybridization. Hey1 and Hey2 were not significantly expressed in tooth germs at epithelial thickening, bud, and cap stages during molar development. In the dental epithelium in molars at the bell stage and incisors, Hey2 transcripts were restricted to the undifferentiated inner enamel epithelium and down-regulated in preameloblasts and ameloblasts. On the other hand, Hey1 was mainly expressed in preameloblasts and down-regulated in differentiated ameloblasts. Both genes were not significantly expressed in other dental epithelial tissues, including the outer enamel epithelium, stellate reticulum, and stratum intermedium cells. In the dental mesenchyme, Hey1 was intensely transcribed in the subodontoblastic layer of the dental pulp in both molars and incisors, whereas Hey2 was barely detectable in mesenchymal components. Our data implied that Hey2 function is restricted to transient amplifying cells of the ameloblast cell lineage and that Hey1 plays a role in the composition of the subodontoblastic layer, in addition to ameloblast differentiation. These findings provide novel clues for the better understanding of tooth development. Show less