Considerable amount of research has been focused on dentin mineralization, odontoblast differentiation, and their application in dental tissue engineering. However, very little is known about the differential role of functionally and spatially distinct types of dental epithelium during odontoblast development. Here we show morphological and functional differences in dentin located in the crown and roots of mouse molar and analogous parts of continuously growing incisors. Using a reporter (DSPP-cerulean/DMP1-cherry) mouse strain and mice with ectopic enamel (Spry2+/- ;Spry4-/- ), we show that the different microstructure of dentin is initiated in the very beginning of dentin matrix production and is maintained throughout the whole duration of dentin growth. This phenomenon is regulated by the different inductive role of the adjacent epithelium. Thus, based on the type of interacting epithelium, we introduce more generalized terms for two distinct types of dentins: cementum versus enamel-facing dentin. In the odontoblasts, which produce enamel-facing dentin, we identified uniquely expressed genes (Dkk1, Wisp1, and Sall1) that were either absent or downregulated in odontoblasts, which form cementum-facing dentin. This suggests the potential role of Wnt signalling on the dentin structure patterning. Finally, we show the distribution of calcium and magnesium composition in the two developmentally different types of dentins by utilizing spatial element composition analysis (LIBS). Therefore, variations in dentin inner structure and element composition are the outcome of different developmental history initiated from the very beginning of tooth development. Taken together, our results elucidate the different effects of dental epithelium, during crown and root formation on adjacent odontoblasts and the possible role of Wnt signalling which together results in formation of dentin of different quality. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

• Keywords
• DENTIN, DENTINOGENESIS, INCISOR, LIBS, MICROSTRUCTURE, MOLAR, ODONTOBLAST, ODONTOGENESIS, PROCESSES, TEETH, WNT SIGNALING,
• MeSH
• Cell Differentiation MeSH
• Dentin * MeSH
• Epithelium MeSH
• Extracellular Matrix Proteins genetics   MeSH
• Mice MeSH
• Odontoblasts * MeSH
• Odontogenesis MeSH
• Incisor MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Extracellular Matrix Proteins MeSH

To gain a better understanding of the progression of progenitor cells in the odontoblast lineage, we have examined and characterized the expression of a series of GFP reporters during odontoblast differentiation. However, previously reported GFP reporters (pOBCol2.3-GFP, pOBCol3.6-GFP, and DMP1-GFP), similar to the endogenous proteins, are also expressed by bone-forming cells, which made it difficult to delineate the two cell types in various in vivo and in vitro studies. To overcome these difficulties we generated DSPP-Cerulean/DMP1-Cherry transgenic mice using a bacterial recombination strategy with the mouse BAC clone RP24-258g7. We have analyzed the temporal and spatial expression of both transgenes in tooth and bone in vivo and in vitro. This transgenic animal enabled us to visualize the interactions between odontoblasts and surrounding tissues including dental pulp, ameloblasts and cementoblasts. Our studies showed that DMP1-Cherry, similar to Dmp1, was expressed in functional and fully differentiated odontoblasts as well as osteoblasts, osteocytes and cementoblasts. Expression of DSPP-Cerulean transgene was limited to functional and fully differentiated odontoblasts and correlated with the expression of Dspp. This transgenic animal can help in the identification and isolation of odontoblasts at later stages of differentiation and help in better understanding of developmental disorders in dentin and odontoblasts.

• Keywords
• Odontoblasts, bone, dentin matrix protein 1, dentin sialophosphoprotein, fluorescent protein reporters,
• MeSH
• Cell Differentiation MeSH
• Extracellular Matrix Proteins genetics   MeSH
• Fluorescent Dyes MeSH
• Phosphoproteins genetics   MeSH
• Mice, Transgenic MeSH
• Mice MeSH
• Odontoblasts cytology   MeSH
• Genes, Reporter * MeSH
• Sialoglycoproteins genetics   MeSH
• Transgenes MeSH
• Green Fluorescent Proteins genetics   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• dentin sialophosphoprotein MeSH Browser
• Dmp1 protein, mouse MeSH Browser
• Extracellular Matrix Proteins MeSH
• Fluorescent Dyes MeSH
• Phosphoproteins MeSH
• Sialoglycoproteins MeSH
• Green Fluorescent Proteins MeSH