Regeneration of halved embryonic lower first mouse molars: correlation with the distribution pattern of non dividing IDE cells, the putative organizers of morphogenetic units, the cusps

Recently we demonstrated that non-cycling, cap-stage, mouse molar inner den tal epithelial (IDE) cells corresponding to the primary enamel knot (EK) ar ea underwent a coordinated temporo-spatial patterning leading to their patc hy irregular segregation at the tips of the forming cusps. These non-cyclin g cells were suggested to perhaps represent the organizers of the morphogen etic units (OMU), the cusps. The present study has analyzed the regenerativ e capacity of halved cap-stage first lower mouse molars through three dimen sional (3D) reconstructions. Partial regeneration of the anterior half and possible complete regeneration of the posterior half were documented. Using BrdU (5-bromo-2'-deoxyuridine) labeling and 3D reconstructions of the IDE, we have correlated the patterns of cusp regeneration with the distribution of BrdU negative IDE cells, These data support a morphogenetic role for th e non-cycling IDE cells.