Simultaneous Fluorescent Identification of Odontoblasts and Ameloblasts

The tooth is mainly composed of dentin and enamel. Identification of dentin-producing odontoblasts and enamel-producing ameloblasts using reporter techniques is useful to study tooth development and regeneration with tissue engineering. Ameloblasts express Amelogenin, Ameloblastin, Enamelin, and Amelotin, whereas odontoblasts express Dentin sialophosphoprotein (Dspp) and Dentin matrix protein1 (Dmp1). Although there are several transgenic lines using promoter elements or bacterial artificial chromosomes (BACs) to label odontoblasts and ameloblasts, there is a possibility that the expression patterns vary from the endogenous genes. Here, we established 2 lines of mice where tdTomato was knocked into the second exon of X-chromosomal Amelogenin (Amelx), and green fluorescent protein (GFP) was knocked into the second exon of Dspp. tdTomato and GFP were highly expressed on secretory ameloblasts and secretory and fully differentiated odontoblasts, respectively. In addition, DSPP and AMELX were not produced in the dentin matrix and enamel matrix of Dspp(GFP/GFP) and Amelx(tdTomato) male mice (as representative of Amelx(tdTomato/Y) hemizygous male mice), respectively. Moreover, micro-computed tomography analysis of Amelx(tdTomato) male mice revealed a notable reduction in enamel volume but increased dentin mineral density. Dspp(GFP/GFP) mice had reduced dentin mineral density. To identify odontoblasts and ameloblasts from developing tooth, we examined the expression of mesenchymal cell surface molecules CD90, CD166 and epithelial cell surface molecules CD49f, Epcam1 with fluorescence on odontoblasts and ameloblasts in these mice. We found that GFP(+) odontoblasts and tdTomato(+) ameloblasts in tooth germ from 0.5-d-old Dspp(GFP/+) mice and Amelx(tdTomato) male mice were enriched in CD45(-)/Ter119(-)/Epcam1(-)/CD90(+)/Integrin alpha 4(+)cell fractions and CD45(-)/Ter119(-)/Epcam1(+)/CD49f(+)/CD147(+) cell fractions, respectively. By using antibodies against mesenchymal and epithelial cell surface molecules and fluorescence, we can easily distinguish odontoblasts from ameloblasts and isolate each cell for further studies. These mice would serve as useful models for tooth development and regeneration as well as provide concurrent observation for the differentiation processes of odontoblasts and ameloblasts in vivo and in vitro.

Automated summary

The tooth is mainly composed of dentin and enamel, and identification of dentin-producing odontoblasts and enamel-producing ameloblasts using reporter techniques is crucial for studying tooth development and tissue engineering regeneration. By establishing transgenic mouse lines labeling odontoblasts and ameloblasts, researchers were able to track the expression patterns of related genes and observe changes in enamel volume and dentin mineral density, providing valuable insights for tooth development and regeneration research. Additionally, examining the expression of specific cell surface molecules in these mice allowed for easy distinction and isolation of odontoblasts and ameloblasts, contributing to further studies in differentiation processes.