Morita Tsuyoshi, Fujikawa Kaoru, Baba Otto, Shibata Shunichi
Department of Maxillofacial Anatomy, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Department of Oral and Maxillofacial Anatomy, Graduate School of Oral Sciences, Tokushima University, Tokushima, Japan.
Gene Expr Patterns. 2016 May;21(1):28-40. doi: 10.1016/j.gep.2016.06.002. Epub 2016 Jun 8.
Hyaluronan (HA) is a major constituent molecule in most extracellular matrices and is synthesized by Hyaluronan synthase (Has). In the present study, we examined expression patterns of Has1, -2, -3 mRNA in developing mouse molar and incisor tooth germs from embryonic day (E) 11.5 to postnatal day (P) 7, focusing on Hertwig's epithelial root sheath (HERS) and the apical bud in particular. Has1 mRNA expression was not detected in all tooth germs examined. Has2 mRNA was expressed in the surrounding mesenchyme from E12.0 to 18.0 in both molar and incisor tooth germs, but disappeared after birth. Meanwhile, Has3 mRNA was exclusively expressed within the enamel organ, especially in the inner enamel epithelium (IEE), stellate reticulum (SR), and stratum intermedium (SI) until the early bell stage at E16.0. Has3 mRNA disappeared as IEE differentiated into differentiating ameloblasts (dABs), but remained in SI until the root developmental stage of the molar tooth germ at P7. Has3 mRNA was also expressed in HERS until P7. In incisors, Has3 mRNA was expressed in the apical bud, especially in the transit-amplifying (TA) cell region from E16.0 to P7, and in the papillary layer (PL) adjacent to the mature enamel. These gene expression patterns suggested that Has3 is the main control factor for prenatal and postnatal HA synthesis of the tooth germ, and may in part regulate crown and root formation of the tooth germ, maintenance of stem cell niches in the apical bud as well as mineral transport in PL.
透明质酸（HA）是大多数细胞外基质中的主要组成分子，由透明质酸合酶（Has）合成。在本研究中，我们检测了从胚胎第11.5天（E）到出生后第7天（P）发育中的小鼠磨牙和切牙牙胚中Has1、-2、-3 mRNA的表达模式，特别关注赫特维希上皮根鞘（HERS）和根尖芽。在所检测的所有牙胚中均未检测到Has1 mRNA表达。Has2 mRNA在磨牙和切牙牙胚中从E12.0到18.0均在周围间充质中表达，但出生后消失。同时，Has3 mRNA仅在釉器内表达，特别是在E16.0的早期钟状期之前，在内釉上皮（IEE）、星网状层（SR）和中间层（SI）中表达。随着IEE分化为分化成釉细胞（dABs），Has3 mRNA消失，但在SI中一直存在到磨牙牙胚在P7的牙根发育阶段。Has3 mRNA在HERS中也表达至P7。在切牙中，Has3 mRNA在根尖芽中表达，特别是在从E16.0到P7的过渡增殖（TA）细胞区域，以及在与成熟釉质相邻的乳头层（PL）中表达。这些基因表达模式表明，Has3是牙胚产前和产后HA合成的主要控制因子，可能部分调节牙胚的冠根形成、根尖芽中干细胞龛的维持以及PL中的矿物质运输。
