Lithium inhibits palatal fusion and osteogenic differentiation in palatal shelves in vitro

• LiCl induces persistence of the midline epithelial seam (MES) and causes failure of palatal fusion.
• LiCl prevents osteogenic differentiation in palatal shelves.
• LiCl may activate the canonical Wnt signaling to impair the fusion of the secondary palate.

ObjectiveGlycogen synthase kinase-3β (Gsk-3β)/β-catenin signaling regulates development of the secondary palate. It has been unclear about the effects of Gsk-3β/β-catenin signaling on palatal fusion and osteogenic differentiation in palatal shelves.DesignIn this study, palatal shelves from mouse embryonic day 13 (E13) were cultured in vitro with or without lithium chloride (LiCl). Palatal fusion was evaluated by haematoxylin-eosin staining. The expression of osteogenic markers in palatal shelves was measured by quantitative PCR, and immunohistochemical staining. Cell proliferation and apoptosis were examined by Ki-67 immunohistochemical and TUNEL staining, respectively. Gsk-3β expression was evaluated by quantitative PCR and Western blotting. β-catenin protein expression was evaluated by Western blotting.ResultsAfter the treatment with 10 mM LiCl, palatal shelves failed to fuse, and the mRNA and protein levels of osteogenic markers were reduced compared with controls. The number of Ki67-positive cell in the palatal osteoid was significantly higher in the LiCl group than in the controls. The apoptotic cells in the midline epithelial seam were reduced by LiCl. Gsk-3β mRNA and protein expression levels decreased and β-catenin protein expression levels increased by treatment of LiCl.ConclusionOur findings show that LiCl-mediated GSK3β inhibition prevents palatal fusion and osteogenic differentiation in palatal shelves by increased β-catenin signaling. It indicated that overactivation of canonical Wnt signaling might impair the fusion of the secondary palate.