Group headed by H.Lesot

The embryonic tooth in the mouse was initially chosen in our group as a model to investigate the nature and role of epithelial-mesenchymal interactions during organogenesis. First dealing with normal development in situ and in vitro, the data were then completed by considering specific mutant or transgenic mice (collaboration with R. Peterkova). More recently, this work was re-oriented to investigate the possibility to reconstitute tooth germs by culturing and then implanting re-associations between dissociated single cells, which brought information on cell plasticity and position information.

The embryonic tooth is composed of the enamel organ (epithelial origin) and a dental mesenchyme (ecto-mesenchymal origin), which both interact and reciprocally exchange sequential sets of information. These interactions are mediated by extracellular matrix constituents of the basement membrane and also involve diffusible signaling molecules. This allows a strict time and space regulation of cell kinetic, organ morphogenesis, epithelial histogenesis, change in the mesenchymal cell heterogeneity and cell differentiation in both compartments: odontoblasts secreting dentin in the crown and root, ameloblasts secreting enamel in the crown, and cementoblasts in the root.

By means of well-established collaborations, four complementary points are currently investigated:

1) The relationship between epithelial histogenesis and crown morphogenesis: induction, organization, positioning and fate of the primary enamel knot (a morphogenetic signaling center).

2) Mechanisms potentially involved in the reactivation of the dental lamina (FGFs and Shh) as a possibility to induce ectopic tooth formation or dental tissues development.

3) Tooth organ engineering, based on a biomimetic approach, thus re-employing the data we could get from studying tooth development.

4) The characteristics of dental mesenchymal cells to help in the selection or design of non-embryonic cell sources to be used for organ engineering