Dental lamina as source of odontogenic stem cells: evolutionary origins and developmental control of tooth generation in gnathostomes

Abstract

This study considers stem cells for odontogenic capability in biological tooth renewal in the broad context of gnathostome dentitions and the derivation of them from oral epithelium. The location of the developmental site and cell dynamics of the dental lamina are parameters of a possible source for odontogenic epithelial stem cells, but the phylogenetic history is not known. Understanding the phylogenetic basis for stem cell origins throughout continuous tooth renewal in basal jawed vertebrates is the ultimate objective of this study. The key to understanding the origin and location of stem cells in the development of the dentition is sequestration of stem cells locally for programmed tooth renewal. We suggest not only the initial pattern differences in each dentate field but local control subsequently for tooth renewal within each family. The role of the specialized odontogenic epithelium (odontogenic band) is considered as that in which the stem cells reside and become partitioned. These regulate time, position and shape in sequential tooth production. New histological data for chondrichthyan fish show first a thickening of the oral epithelium (odontogenic band). After this, all primary and successive teeth are only generated deep to the oral epithelium from a dental lamina. In contrast, in osteichthyan fish the first teeth develop directly within the odontogenic band. In addition, successors are initiated at each tooth site in the predecessor tooth germ (without a dental lamina). We suggest that stem cells specified for each tooth family are set up and located in intermediate cells between the outer and inner dental epithelia.

Signaling Networks Regulating Tooth Organogenesis and Regeneration, and the Specification of Dental Mesenchymal and Epithelial Cell Lineages

“…Similarly, in the reptiles the replacement tooth arises from an outgrowth of the dental lamina each time the previous tooth has grown to a certain size (Richman and Handrigan 2011). In contrast, in the fish species studied, there seems to be no successional dental lamina, and the new teeth are initiated directly from the epithelium of the previous tooth or from the oral epithelium (Smith et al 2009). Wnt signaling has been associated with tooth replacement both in mammals and reptiles and may be a key factor regulating tooth renewal across vertebrates (Järvinen et al 2009;Richman and Handrigan 2011).…”

Evolution and developmental diversity of tooth regeneration

“…The collaboration of these two genes may infer tooth competence [25][26][27][28]. In sharks, the thickening or proliferation of the cells in the odontogenic band continues posto-dorsally coincident with an in-pushing of the basal layer into the underlying and condensed mesenchyme [29][30][31] (Fig. 1).…”

“…1). This creates a fold of epithelium that is continuous along the jaw, known as the dental lamina [30][31][32]. The oro-lingual extent of the dental lamina is where new tooth replacements are formed (Fig.…”

“…The source of epithelial cells necessary for replacing teeth, in most toothed vertebrates, appears to be the dental lamina [10,12,14,28,30,33,46,57,62]. The early odontogenic band provides genetic cues that support a dental fate and the patterning of tooth units from these epithelial cells.…”

“…The early odontogenic band provides genetic cues that support a dental fate and the patterning of tooth units from these epithelial cells. Cells of the dental lamina are likely to be essential for the capacity to replace the entire dentition [30] and without the maintenance of these specialised cells the dentition would not replenish and in some cases could be lost, as observed in many mammals. The dental lamina can be structurally diverse among vertebrates -even within each clade of vertebrates the mode of tooth replacement can show variation (Fig.…”