In vitro synchronization of embryonic mouse incisor preodontoblasts and preameloblasts: repercussions on terminal differentiation.
Preodontoblasts divide asynchronously and their terminal differentiation occurs gradually. Experimental data suggested that the expression of competence by preodontoblasts to respond to specific epigenetic signals, triggering their overt differentiation, requires a minimal number of cell cycles. The intrinsic timing mechanism could imply division counting and preodontoblasts of juxtaposed cell generations might sequentially withdraw from the last physiological cycle. To test such an hypothesis, embryonic mouse lower incisors were cultured in vitro and treated sequentially with nocodazole in order to induce a transitory synchronization of the dividing preodontoblasts and preameloblasts. This synchronization led to a disorganization of the physiological gradual terminal differentiation of the odontoblasts, giving rise to three distinct domains comprising respectively: 1) odontoblasts with altered polarization and predentin secretion; 2) odontoblasts demonstrating equivalent polarization and predentin deposition; and 3) preodontoblasts-odontoblasts involved in gradual terminal differentiation. These results strongly suggest that the gradient of odontoblast functional differentiation results from sequential withdrawal from asynchronous cell cycles of competent cells able to overtly differentiate.
Schmitt
R
R
INSERM U424, Institut de Biologie Médicale, Faculté de Médicine de Strasbourg, France. Regine.Schmitt@medecine.u-strasbg.fr
Ruch
J V
JV
D000565:Ameloblasts / Q000166:cytology* / Q000187:drug effects; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D002478:Cells, Cultured; D003804:Dentin / Q000378:metabolism; D007180:Incisor / Q000196:embryology; D051379:Mice; D015739:Nocodazole / Q000494:pharmacology; D009804:Odontoblasts / Q000166:cytology* / Q000187:drug effects; D009924:Organ Culture Techniques; D011498:Protein Precursors / Q000378:metabolism; D013997:Time Factors
D000970:Antineoplastic Agents; D011498:Protein Precursors; D015739:Nocodazole