Constitutive stabilization of β-catenin in the dental mesenchyme leads to excessive dentin and cementum formation

Wnt/beta-catenin signaling plays an important role in morphogenesis and cellular differentiation during development. Essential roles of Wnt/beta-catenin signaling in tooth morphogenesis have been well known, but the involvement of Wnt/beta-catenin signaling in the dental hard tissue formation remains undefined. To understand roles of Wnt/beta-catenin signaling in dentin and cementum formation, we generated and analyzed the conditional beta-catenin stabilized mice in the dental mesenchyme. The OC-Cre;Catnb(lox(ex3)/+) mice exhibited malformed teeth characterized by aberrantly formed dentin and excessively deposited cementum. Large amount of dentin was rapidly formed with widened predentin and numerous globular calcifications in the crown. Whereas roots of molars were short and covered with the excessively formed cellular cementum. With age, the coronal pulp chamber and periodontal space were narrowed by the excessively formed dentin and cementum, respectively. To compare the changes of gene expression in the mutant mice, Col1a1 expression was increased but that of Dspp was decreased in the odontoblasts. However, both of Cal1a1 and Bsp expression was increased in the cementoblasts. The gene expression changes were consistent with the localization of matrix proteins. Biglycan and PC-1 was increased but Phex was decreased in the odontoblasts and dentin matrix, respectively. TNAP was increased but Dmp1 and FGF23 was decreased in the cementoblasts and cementum matrix, respectively. Our results indicate that persistent stabilization of g-catenin in the dental mesenchyme leads to premature differentiation of odontoblasts and differentiation of cementoblasts, and induces excessive dentin and cementum formation in vivo. These results suggest that temporospatial regulation of Wnt/beta-catenin signaling plays critical roles in the differentiation of odontoblasts and cementoblasts, and that inhibition of Wnt/beta-catenin signaling may be important for the formation of dentin and cementum during tooth development. Local modulation of Wnt/beta-catenin signaling has therapeutic potential to improve the regeneration of dentin and periodontium. (C) 2011 Elsevier Inc. All rights reserved.