Department of Maxillofacial Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo .
Eur J Histochem. 2020 Feb 10;64(1):3092. doi: 10.4081/ejh.2020.3092.
The gene expression and protein synthesis of small leucine-rich proteoglycans (SLRPs), including decorin, biglycan, fibromodulin, and lumican, was analyzed in the context of the hypothesis that they are closely related to tooth formation. In situ hybridization, immunohistochemistry, and organ culture with metabolic labeling of [35S] were carried out in mouse first molar tooth germs of different developmental stages using ICR mice at embryonic day (E) 13.5 to postnatal day (P) 7.0. At the bud and cap stage, decorin mRNA was expressed only in the surrounding mesenchyme, but not within the tooth germ. Biglycan mRNA was then expressed in the condensing mesenchyme and the dental papilla of the tooth germ. At the apposition stage (late bell stage), both decorin and biglycan mRNA were expressed in odontoblasts, resulting in a switch of the pattern of expression within the different stages of odontoblast differentiation. Decorin mRNA was expressed earlier in newly differentiating odontoblasts than biglycan. With odontoblast maturation and dentin formation, decorin mRNA expression was diminished and localized to the newly differentiating odontoblasts at the cervical region. Simultaneously, biglycan mRNA took over and extended its expression throughout the new and mature odontoblasts. Both mRNAs were expressed in the dental pulp underlying the respective odontoblasts. At P7.0, both mRNAs were weakly expressed but maintained their spatial expression patterns. Immunostaining showed that biglycan was localized in the dental papillae and pulp. In addition, all four SLRPs showed clear immunostaining in predentin, although the expressions of fibromodulin and lumican mRNAs were not identified in the tooth germs examined. The organ culture data obtained supported the histological findings that biglycan is more predominant than decorin at the apposition stage. These results were used to identify biglycan as the principal molecule among the SLRPs investigated. Our findings indicate that decorin and biglycan show spatial and temporal differential expressions and play their own tissue-specific roles in tooth development.
小富含亮氨酸的蛋白聚糖（SLRPs）的基因表达和蛋白质合成，包括核心蛋白聚糖、大蛋白聚糖、纤维连接蛋白和亮蛋白聚糖，在它们与牙齿形成密切相关的假说背景下进行了分析。在不同发育阶段的 ICR 小鼠的第一磨牙牙胚中，通过胚胎期（E）13.5 至出生后（P）7.0 进行了原位杂交、免疫组织化学和代谢标记 [35S] 的器官培养。在芽和帽期，核心蛋白聚糖 mRNA 仅在周围的间质中表达，而不在牙胚内表达。然后，大蛋白聚糖 mRNA 在牙胚的凝聚间质和牙髓中表达。在附着期（晚期钟状期），核心蛋白聚糖和大蛋白聚糖 mRNA 均在成牙本质细胞中表达，导致成牙本质细胞分化的不同阶段的表达模式发生转换。核心蛋白聚糖 mRNA 在新分化的成牙本质细胞中的表达早于大蛋白聚糖。随着成牙本质细胞的成熟和牙本质的形成，核心蛋白聚糖 mRNA 的表达减少并定位于颈部的新分化的成牙本质细胞。同时，大蛋白聚糖 mRNA 接管并扩展其在新和成牙本质细胞中的表达。两种 mRNA 均在相应成牙本质细胞下方的牙髓中表达。在 P7.0，两种 mRNA 的表达均较弱，但仍保持其空间表达模式。免疫染色显示大蛋白聚糖定位于牙乳头和牙髓。此外，所有四种 SLRPs 在前期牙本质中均显示出清晰的免疫染色，尽管在检查的牙胚中未鉴定出纤维连接蛋白和亮蛋白聚糖的 mRNA 表达。器官培养数据支持组织学发现，在附着期，大蛋白聚糖比核心蛋白聚糖更为突出。这些结果用于确定大蛋白聚糖是所研究的 SLRPs 中的主要分子。我们的研究结果表明，核心蛋白聚糖和大蛋白聚糖在空间和时间上表现出差异表达，并在牙齿发育中发挥其自身的组织特异性作用。
