Enhanced Wnt/β-catenin signalling during tooth morphogenesis impedes cell differentiation and leads to alterations in the structure and mineralisation of the adult tooth.
BACKGROUND
Previous studies have indicated that over-activation of the wingless interaction site (Wnt)/β-catenin signalling pathway has important implications for tooth development, at the level of cell differentiation and morphology, as well as for the production of supernumerary teeth. Here, we provide evidence for a crucial role of this signalling pathway during the stage of tooth morphogenesis. We have developed an in vitro model consisting of 14.5-day-old mouse embryo first molars, in which the Wnt pathway is overactivated by the glycogen synthase kinase-3 inhibitor 6-bromoindirubin-3'-oxime (BIO; 20 µM).


RESULTS
We found that over-activation of the Wnt/β-catenin pathway delayed the differentiation and growth of the inner dental epithelium. In addition, in contrast to controls in which Nestin protein expression was restricted to differentiated odontoblasts, in BIO-treated molars, Nestin expression spread through sub-odontoblastic cellular layers. This alteration appears to be related to: (i) the over-expression of Bmp4 in the same region, (ii) the delay in odontoblast precursor cell differentiation and (iii) increased proliferation of mesenchymal cells. Furthermore, treatments longer than 6 days induced the malformation of typical dental structures and led to a total lack of cell differentiation. Finally, over-activation of the Wnt route during odontogenesis resulted in adult teeth which presented altered size, morphology and mineralisation.


CONCLUSIONS
Our results indicate that Wnt/β-catenin over-activation during tooth morphogenesis is sufficient to cause dramatic alterations in the adult tooth, by delaying cellular differentiation and stimulating proliferation of the dental mesenchyme of developing teeth.
Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa 48940, Vizcaya, Spain.
Maitane
M
Aurrekoetxea
Jon
J
Lopez
Patricia
P
García
Gaskon
G
Ibarretxe
Fernando
F
Unda
D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008963:Molar / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism* / Q000637:transplantation*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D064231:Nestin; D009804:Odontoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009805:Odontogenesis / Q000187:drug effects / Q000235:genetics*; D010091:Oximes / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013737:Testis; D014074:Tooth Calcification / Q000187:drug effects / Q000502:physiology; D016042:Transplantation, Heterotopic; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000187:drug effects / Q000235:genetics; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
C483321:6-bromoindirubin-3'-oxime; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D007211:Indoles; D007381:Intermediate Filament Proteins; D009419:Nerve Tissue Proteins; C577485:Nes protein, mouse; D064231:Nestin; D010091:Oximes; D051153:Wnt Proteins; D051176:beta Catenin; D038362:Glycogen Synthase Kinase 3