Butler W T, Ritchie H
Department of Basic Sciences, University of Texas-Houston Health Sciences Center 77030, USA.
Int J Dev Biol. 1995 Feb;39(1):169-79.
Odontoblasts are responsible for formation of predentin, which is transformed to dentin when apatite crystals are formed and the fibrillar matrix becomes mineralized. Odontoblasts are specialized cells that synthesize and secrete a unique set of non-collagenous proteins (NCPs), as well as the collagenous matrix largely comprised of type I collagen. The NCPs consist of dentin specific and mineralized tissue specific proteins, as well as other proteins that are found in a variety of tissues. Three dentin specific proteins have been recognized to date: dentin phosphoprotein (DPP), also called phosphophoryn, AG1 (dentin matrix protein 1, Dmp1) and dentin sialoprotein (DSP). DPP appears to be made by odontoblasts and appears at the mineralization front within a short time. It may be secreted via odontoblastic processes. DPP binds to collagen and potentially initiates formation of apatite crystals. A second DPP function appears to be to bind to the 100 face of growing apatite crystals and to inhibit or slow their growth; thus, DPP may play a dual role by initiating mineralization and then affecting the crystal growth and perhaps the habit of the crystals. Although no function has been ascribed to AG1 or DSP, they should prove to be important markers for the odontoblast phenotype. A recent unique finding is that two separate genes appear to code for more than one DSP mRNA; other transcripts may result from differential splicing. Examples of mineralized tissue specific proteins expressed by osteoblasts as well as odontoblasts are bone sialoprotein (BSP) and osteocalcin. Some NCPs expressed by osteoblasts, odontoblasts and several other tissues include osteopontin (OPN) and the chondroitin sulfate containing proteoglycans, decorin and biglycan. We propose that characterization of odontoblasts in tissues and cultures should rely upon utilization of sets of markers for the above NCPs and their mRNAs. Similar approaches are commonly used in investigations on osteoblasts. Finally, dentin (like bone) contains other molecules such as growth factors, and serum derived proteins, found within the matrix; no functional significance has yet been placed upon this finding. Future experiments should focus upon the elucidation of the three dimensional structures of the collagenous fibrillar network and of the NCPs to determine the relationships to mineralization. The role played by odontoblasts in controlling extracellular events, such as by selective secretory routes, will require careful exploration.
成牙本质细胞负责前期牙本质的形成，当磷灰石晶体形成且纤维状基质矿化时，前期牙本质转化为牙本质。成牙本质细胞是一种特殊的细胞，能合成并分泌一组独特的非胶原蛋白（NCPs），以及主要由I型胶原组成的胶原基质。NCPs包括牙本质特异性和矿化组织特异性蛋白，以及在多种组织中发现的其他蛋白。迄今为止，已识别出三种牙本质特异性蛋白：牙本质磷蛋白（DPP），也称为磷磷蛋白、AG1（牙本质基质蛋白1，Dmp1）和牙本质涎蛋白（DSP）。DPP似乎由成牙本质细胞产生，并在短时间内出现在矿化前沿。它可能通过成牙本质细胞突起分泌。DPP与胶原结合，并可能启动磷灰石晶体的形成。DPP的第二个功能似乎是与生长中的磷灰石晶体的100面结合，并抑制或减缓其生长；因此，DPP可能通过启动矿化，然后影响晶体生长以及可能的晶体习性，发挥双重作用。虽然尚未赋予AG1或DSP任何功能，但它们应被证明是成牙本质细胞表型的重要标志物。最近一个独特的发现是，两个不同的基因似乎编码不止一种DSP mRNA；其他转录本可能来自差异剪接。成骨细胞以及成牙本质细胞表达的矿化组织特异性蛋白的例子有骨涎蛋白（BSP）和骨钙素。成骨细胞、成牙本质细胞和其他几种组织表达的一些NCPs包括骨桥蛋白（OPN）以及含硫酸软骨素的蛋白聚糖、核心蛋白聚糖和双糖链蛋白聚糖。我们建议，对组织和培养物中的成牙本质细胞进行表征应依赖于利用上述NCPs及其mRNA的标志物组合。类似的方法常用于成骨细胞的研究。最后，牙本质（如骨）含有其他分子，如生长因子和在基质中发现的血清衍生蛋白；这一发现尚未被赋予功能意义。未来的实验应集中于阐明胶原纤维网络和NCPs的三维结构，以确定它们与矿化的关系。成牙本质细胞在控制细胞外事件中所起的作用，如通过选择性分泌途径，将需要仔细探索。
