Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, Osaka, Japan.
Department of Dental Biomaterials, Osaka University Graduate School of Dentistry, Osaka, Japan.
J Dent Res. 2023 Sep;102(10):1162-1171. doi: 10.1177/00220345231182355. Epub 2023 Jul 14.
Teeth consist of 3 mineralized tissues: enamel, dentin, and cementum. Tooth malformation, the most common craniofacial anomaly, arises from complex genetic and environmental factors affecting enamel structure, size, shape, and tooth eruption. Hyaluronic acid (HA), a primary extracellular matrix component, contributes to structural and physiological functions in periodontal tissue. Transmembrane protein 2 (TMEM2), a novel cell surface hyaluronidase, has been shown to play a critical role during embryogenesis. In this study, we demonstrate messenger RNA expression in inner enamel epithelium and presecretory, secretory, and mature ameloblasts. knock-in reporter mice reveal TMEM2 protein localization at the apical and basal ends of secretory ameloblasts. Micro-computed tomography analysis of epithelial-specific conditional knockout (-) mice shows a significant reduction in enamel layer thickness and severe enamel deficiency. Enamel matrix protein expression was remarkably downregulated in - mice. Scanning electron microscopy of enamel from - mice revealed an irregular enamel prism structure, while the microhardness and density of enamel were significantly reduced, indicating impaired ameloblast differentiation and enamel matrix mineralization. Histological evaluation indicated weak adhesion between cells and the basement membrane in - mice. The reduced and irregular expressions of vinculin and integrin β1 suggest that deficiency attenuated focal adhesion formation. In addition, abnormal HA accumulation in the ameloblast layer and weak claudin 1 immunoreactivity in - mice indicate impaired tight junction gate function. Irregular actin filament assembly was also observed at the apical and basal ends of secretory ameloblasts. Last, we demonstrated that -deficient mHAT9d mouse ameloblasts exhibit defective adhesion to HA-containing substrates in vitro. Collectively, our data highlight the importance of TMEM2 in adhesion to HA-rich extracellular matrix, cell-to-cell adhesion, ameloblast differentiation, and enamel matrix mineralization.
牙齿由 3 种矿化组织组成：牙釉质、牙本质和牙骨质。牙齿畸形是最常见的颅面异常，由影响牙釉质结构、大小、形状和牙齿萌出的复杂遗传和环境因素引起。透明质酸（HA）是一种主要的细胞外基质成分，有助于牙周组织的结构和生理功能。跨膜蛋白 2（TMEM2）是一种新型的细胞表面透明质酸酶，在胚胎发生过程中发挥着关键作用。在这项研究中，我们证明了 TMEM2 在牙内釉上皮细胞和前分泌、分泌和成熟成釉细胞中的信使 RNA 表达。TMEM2 敲入报告小鼠揭示了 TMEM2 蛋白在分泌成釉细胞的顶端和基底末端的定位。上皮细胞特异性条件性敲除（-/-）小鼠的微计算机断层扫描分析显示，釉质层厚度显著减少，釉质严重缺乏。-/-小鼠的釉质蛋白表达显著下调。-/-小鼠的釉质扫描电子显微镜显示，釉质棱柱结构不规则，而釉质的显微硬度和密度显著降低，表明成釉细胞分化和釉质基质矿化受损。-/-小鼠的组织学评估表明细胞与基膜之间的粘附较弱。-/-小鼠中粘着斑蛋白的 Vinculin 和整合素β1 的表达减少且不规则，表明 缺失减弱了粘着斑的形成。此外，在 -/-小鼠中，HA 在成釉细胞层中的积累异常和 Claudin 1 的免疫反应性减弱表明紧密连接门控功能受损。在分泌期成釉细胞的顶端和基底末端也观察到不规则的肌动蛋白丝组装。最后，我们证明了 -/-mHAT9d 小鼠成釉细胞在体外对富含 HA 的底物的粘附能力受损。总之，我们的数据强调了 TMEM2 在与富含 HA 的细胞外基质的粘附、细胞间粘附、成釉细胞分化和釉质基质矿化中的重要性。
