Structure and organization of odontoblasts

Differentiation of odontoblasts involves cell-to-cell recognition, contact stabilization involving the formation of attachment specializations, cytoplasmic polarization, development of the protein synthetic and secretory apparatus, and the active transport of mineral ions. The secretory odontoblast is characterized by an extensive rough-surfaced endoplasmic reticulum, a highly developed Golgi complex, and the presence of specific secretion granules. Type I collagen, a major constituent of dentin matrix, appears to be secreted by the odontoblast into predentin at the proximal portion of the odontoblast process, the major cytoplasmic process extending from the odontoblast cell body into the dentin. The odontoblast process contains a rich network of microtubules and microfilaments. The proximal portion of the process is also a site of fluid-phase endocytosis. Adjacent odontoblasts are held together by numerous macula adherens junctions and a well-developed distal junctional complex adjacent to the predentin. Junctional strands of the occludens type have been observed to be a component of this junctional complex. Tracer studies employing horse-radish peroxidase indicate that this junctional complex does not form a tight barrier to the diffusion of tissue fluid from the interodontoblast spaces into the predentin. Many well-developed gap junctions are formed between adjacent odontoblasts and between odontoblasts and the fibroblasts that make up the subodontoblastic layer. Ca-ATPase activity is demonstrated in the Golgi complex and mitochondrial cristae and along the distal plasma membranes of odontoblasts. ALPase activity is also intense along the entire odontoblast cell surface. The osmium tetroxide-pyroantimonate technique for calcium localization demonstrates prominent reaction precipitates in mitochondria of odontoblasts. Energy-dispersive x-ray microanalysis of anhydrously fixed and processed odontoblasts detected Ca and P peaks throughout the cytoplasm. A sulfur peak is noted in the distal cytoplasm of odontoblasts and in matrix vesicles. Together, these results demonstrate the complexity and variety of cell functions involved in dentinogenesis. © 1996 Wiley-Liss, Inc.     

Comparative gene expression profile analysis between native human odontoblasts and pulp tissue

Aim  To undertake a large-scale analysis of the expression profiles of native human pulp tissue and odontoblasts, and search for genes expressed only in odontoblasts.
Methodology  Microarray was performed to pooled pulp and odontoblasts of native human third molars and to pooled +/− TGF-β1 cultured pulps and odontoblasts (137 teeth). The repeatability of microarray analysis was estimated by comparing the experimental pulp samples with expression profiles of two pulp samples downloaded from the GEO database. The genes expressed only in the experimental pulp samples or in odontoblasts were divided into categories, and the expression of selected odontoblast-specific genes of extracellular matrix (ECM) organization and biogenesis category was confirmed with RT-PCR and Western blot.
Results  A 85.3% repeatability was observed between pulp microarrays, demonstrating the high reliability of the technique. Overall 1595 probe sets were positive only in pulp and 904 only in odontoblasts. Sixteen expressed sequence tags (ESTs), which represent transcribed sequences encoding possibly unknown genes, were detected only in odontoblasts; two consistently expressed in all odontoblast samples. Matrilin 4 (MATN4) was the only ECM biogenesis and organization related gene detected in odontoblasts but not in pulp by microarray and RT-PCR. MATN4 protein expression only in odontoblasts was confirmed by Western blot.
Conclusions  Pulp tissue and odontoblast gene expression profiling provides basic data for further, more detailed protein analysis. In addition, MATN4 and the two ESTs could serve as an odontoblast differentiation marker, e.g. in odontoblast stem cell research.     

影响根尖牙乳头干细胞成牙本质方向分化的因素

背景:根尖牙乳头干细胞是一类牙源性间充质干细胞,在特定诱导因素作用下可分化为成牙本质细胞,形成牙根部牙本质。修复和再生牙髓牙本质复合体是临床治疗牙髓及根尖周病的新策略,尤其是年轻恒牙的保留,因此定向诱导根尖牙乳头干细胞成牙本质方向分化具有重要意义。目的:综述影响根尖牙乳头干细胞成牙本质方向分化的因素,以期为年轻恒牙牙根发育及临床其他领域应用提供研究基础。方法:应用计算机在PubMed数据库、维普数据库、万方数据库及中国期刊全文数据库检索2013年1月至2019年12月相关文献,以“SCAP,odontogenic differentiation”为英文检索词,以“根尖牙乳头干细胞,成牙本质细胞分化”为中文检索词,最终对38篇文献进行归纳总结,其余18篇文献进一步解释说明文章内容。结果与结论:文章系统性回顾了根尖牙乳头干细胞在不同诱导因素作用下通过相关信号通路传导参与根尖牙乳头干细胞向成牙本质细胞定向诱导,例如细胞因子、基因转染、生物活性材料及支架、化学因素、物理因素等。探寻诱导根尖牙乳头干细胞成牙本质方向分化的理想条件,明确其作用效果和作用机制是临床治疗牙髓病、根尖周病及牙髓牙本质复合体组织工程研究的关键问题。     

人成牙本质细胞L型钙离子通道α1亚基D亚型特异性基因的克隆、原核表达和纯化

目的：获得原核表达的人成牙本质细胞L型钙离子通道α1亚基D亚型特异性蛋白。方法：采用RT-PCR技术从人成牙本质样细胞系中获得cDNA,亚克隆至PUC18载体中,经测序确认后,将该基因插入原核表达载体pProEXHTb中,通过电穿孔技术转化E．coli表达菌DH5α,以IPTG诱导蛋白表达,并经Ni—NTA亲和柱层析纯化,SDS-PAGE鉴定。结果：获得的人成牙本质细胞L型钙离子通道α1亚基D亚型特异性cDNA序列与GenBank登录的cDNA序列一致。结论：成功克隆人成牙本质细胞L型钙离子通道α1亚基D亚型特异性基因,建立了原核表达、纯化体系,制备了纯化的人成牙本质细胞L型钙离子通道α1亚基D亚型特异性蛋白。     

Coexpression of Ang1 and Tie2 in Odontoblasts of Mouse Developing and Mature Teeth—A New Insight into Dentinogenesis

Angiopoietin-1 regulates vascular angiogenesis and stabilization, and is reported to promote bone formation by facilitating angiogenesis. To estimate the role of Ang1 in odontogenesis, we explored the distribution of Ang1 and the receptor, Tie2 in the mouse developing and mature first molar of the mandible. At embryonic day 18, when differentiation of odontoblasts begins, immunosignals for Ang1 were intensely detected in the basement membrane and the distal side, which faced the basement membrane of odontoblasts. In situ hybridization revealed that Ang1 was expressed in odontoblasts and ameloblasts facing the basement membrane. Tie2 was localized in the distal side of odontoblasts. After birth, Ang1 was detected in the predentin, whereas both Ang1 and Tie2 were colocalized in odontoblasts and odontoblast processes. These distributions were retained up to 8 weeks. In contrast to odontoblasts, ameloblasts, cementoblasts and osteoblasts expressed Ang1 but did not express Tie2. Colocalization of Ang1 and Tie2 in odontoblasts and selective expression of Tie2 in odontoblasts among cells responsible for calcified tissue formation suggested the involvement of autocrine signals of Ang1-Tie2 in dentinogenesis.     

Essential Roles of Bone Morphogenetic Protein-1 and Mammalian Tolloid-like 1 in Postnatal Root Dentin Formation

Introduction

Mutations in the proteinase bone morphogenetic protein-1 (BMP1) were recently identified in patients with osteogenesis imperfecta, which can be associated with type 1 dentinogenesis imperfecta. BMP1 is co-expressed in various tissues and has overlapping activities with the closely related proteinase mammalian tolloid-like 1 (TLL1). In this study we investigated whether removing the overlapping activities of BMP1 and TLL1 affects the mineralization of tooth root dentin.

A feasibility study for the analysis of reparative dentinogenesis in pOBCol3.6GFPtpz transgenic mice

Frozoni M, Balic A, Sagomonyants K, Zaia AA, Line SRP, Mina M. A feasibility study for the analysis of reparative dentinogenesis in pOBCol3.6GFPtpz transgenic mice. International Endodontic Journal,?45, 907-914, 2012. ABSTRACT: Aim To examine the feasibility of using the pOBCol3.6GFPtpz [3.6-green fluorescent protein (GFP)] transgenic mice as an in vivo model for studying the biological sequence of events during pulp healing and reparative dentinogenesis. Methodology Pulp exposures were created in the first maxillary molar of 12-16-week-old 3.6-GFP transgenic mice with CD1 and C57/Bl6 genetic background. Direct pulp capping on exposed teeth was performed using mineral trioxide aggregate followed by restoration with a light-cured adhesive system (AS) and composite resin. In control teeth, the AS was placed in direct contact with the pulp. Animals were euthanized at various time points after pulp exposure and capping. The maxillary arch was isolated, fixed and processed for histological and epifluorescence analysis to examine reparative dentinogenesis. Results Analysis of teeth immediately after pulp exposure revealed absence of odontoblasts expressing 3.6-GFP at the injury site. Evidence of reparative dentinogenesis was apparent at 4?weeks in 3.6-GFP mice in CD1 background and at 8?weeks in 3.6-GFP mice with C57/Bl6 background. The reparative dentine with both groups contained newly formed atubular-mineralized tissue resembling a dentine bridge and/or osteodentine that was lined by cells expressing 3.6-GFP as well as 3.6-GFP expressing cells embedded within the atubular matrix. Conclusion This study was conducted in a few animals and did not allow statistical analysis. The results revealed that the 3.6-GFP transgenic animals provide a unique model for direct analysis of cellular and molecular mechanisms of pulp repair and tertiary dentinogenesis in vivo. The study also shows the effects of the capping material and the genetic background of the mice in the sequence and timing of reparative dentinogenesis.     

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目的    研究核因子κB受体活化因子配基（RANKL）在人继承恒牙缺失滞留乳牙及乳牙根生理性吸收不同时期的表达。方法    选取2010年6-12月沈阳市口腔医院正畸科及儿童牙病科10～15岁患者因治疗需要拔除的乳牙18颗,按牙根吸收长度不同分为牙根吸收早、中、晚期（早期组、中期组、晚期组）,各6颗。同时选取无恒牙胚滞留乳牙（滞留组）和正畸拔除的正常恒牙（对照组）各6颗。采用免疫组化方法检测RANKL蛋白的表达,并测定累积光密度值。结果    牙髓成纤维细胞：对照组RANKL累积光密度值明显低于其余组（均P < 0.01）;早期组、中期组明显低于晚期组（均P < 0.01）。成牙本质细胞：对照组RANKL累积光密度值亦明显低于其余组（均P < 0.01）;早期组、中期组、晚期组三者间差异均有统计学意义（P < 0.01）。破牙细胞：对照组未见破牙细胞;早期组、中期组与晚期组比较差异有统计学意义（P < 0.01）。结论    RANKL是引起乳牙牙根缓慢吸收的因素之一。