Rosa Joana T, Witten Paul Eckhard, Huysseune Ann
Research Group Evolutionary Developmental Biology, Biology Department, Ghent University, Ghent, Belgium.
Comparative, Adaptive and Functional Skeletal Biology (BIOSKEL), Centre of Marine Sciences (CCMAR), University of Algarve, Campus Gambelas, Faro, Portugal.
Front Physiol. 2021 Oct 6;12:723210. doi: 10.3389/fphys.2021.723210. eCollection 2021.
Bone-producing osteoblasts and dentin-producing odontoblasts are closely related cell types, a result from their shared evolutionary history in the ancient dermal skeleton. In mammals, the two cell types can be distinguished based on histological characters and the cells' position in the pulp cavity or in the tripartite periodontal complex. Different from mammals, teleost fish feature a broad diversity in tooth attachment modes, ranging from fibrous attachment to firm ankylosis to the underlying bone. The connection between dentin and jaw bone is often mediated by a collar of mineralized tissue, a part of the dental unit that has been termed "bone of attachment". Its nature (bone, dentin, or an intermediate tissue type) is still debated. Likewise, there is a debate about the nature of the cells secreting this tissue: osteoblasts, odontoblasts, or yet another (intermediate) type of scleroblast. Here, we use expression of the P/Q rich secretory calcium-binding phosphoprotein 5 () to characterize the cells lining the so-called bone of attachment in the zebrafish dentition. is expressed in late cytodifferentiation stage odontoblasts but not in the cells depositing the "bone of attachment". nor in osteoblasts lining the supporting pharyngeal jaw bone. Together with the presence of the osteoblast marker Zns-5, and the absence of covering epithelium, this links the cells depositing the "bone of attachment" to osteoblasts rather than to odontoblasts. The presence of dentinal tubule-like cell extensions and the near absence of osteocytes, nevertheless distinguishes the "bone of attachment" from true bone. These results suggest that the "bone of attachment" in zebrafish has characters intermediate between bone and dentin, and, as a tissue, is better termed "dentinous bone". In other teleosts, the tissue may adopt different properties. The data furthermore support the view that these two tissues are part of a continuum of mineralized tissues. Expression of can be a valuable tool to investigate how differentiation pathways diverge between osteoblasts and odontoblasts in teleost models and help resolving the evolutionary history of tooth attachment structures in actinopterygians.
产生骨组织的成骨细胞和产生牙本质的成牙本质细胞是密切相关的细胞类型，这源于它们在古代真皮骨骼中共同的进化历史。在哺乳动物中，这两种细胞类型可以根据组织学特征以及细胞在牙髓腔或三联牙周复合体中的位置来区分。与哺乳动物不同，硬骨鱼的牙齿附着方式具有广泛的多样性，从纤维附着到与下方骨骼的牢固骨融合。牙本质与颌骨之间的连接通常由矿化组织环介导，这是牙齿单位的一部分，被称为“附着骨”。其性质（骨、牙本质或中间组织类型）仍存在争议。同样，关于分泌这种组织的细胞的性质也存在争议：成骨细胞、成牙本质细胞还是另一种（中间）类型的成骨细胞。在这里，我们使用富含P/Q的分泌性钙结合磷蛋白5（）的表达来表征斑马鱼牙列中所谓附着骨内衬的细胞。在成牙本质细胞的晚期细胞分化阶段表达，但在沉积“附着骨”的细胞中不表达。在支持性咽颌骨内衬的成骨细胞中也不表达。与成骨细胞标志物Zns-5的存在以及覆盖上皮的缺失一起，这将沉积“附着骨”的细胞与成骨细胞而非成牙本质细胞联系起来。然而，牙本质小管样细胞突起的存在和骨细胞的几乎不存在，将“附着骨”与真正的骨区分开来。这些结果表明，斑马鱼中的“附着骨”具有介于骨和牙本质之间的特征，作为一种组织，更适合称为“牙本质骨”。在其他硬骨鱼中，这种组织可能具有不同的特性。这些数据进一步支持了这两种组织是矿化组织连续体一部分的观点。的表达可以成为研究硬骨鱼模型中成骨细胞和成牙本质细胞之间分化途径如何分歧以及帮助解决辐鳍鱼类牙齿附着结构进化历史的有价值工具。
