Effects of 2,3,7,8-Tetrachlorodibenzo-p-dioxin on the Development of Murine Palate in Organ Culture

Objective: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (tetrachlorodibenzodioxin) is known to cause cleft palates in pregnant mice in vivo. This study aimed at investigating the effects of tetrachlorodibenzodioxin on murine palatogenesis in vitro using organ culture.Materials and Methods: Palatal shelves from ICR mice foetuses (gestational day, 12.5) were removed and dissected to isolate the palatal tissue. Tissues were cultured in a chemically defined, serumless medium using a suspension culture technique. Palatal fusion rates were assessed in suspension cultures containing tetrachlorodibenzodioxin at concentrations of 0.1, 1, 10 and 50 ng/mL and in non-treated controls. Palates from the control and 10 ng/mL groups were stained immunohistologically with antibodies against cleft palate-related factors (transforming growth factor-beta3, muscle segment homeobox 1, Lim-homeobox 8, fibroblast growth factor receptor 1, fibroblast growth factor receptor 2).Results: Over 90% of the palatal shelves completely fused in suspension culture after careful removal of the neural tissues. With tetrachlorodibenzodioxin addition, the palatal fusion rate decreased to 50% at a concentration of 1 ng/mL, however, the rate did not decrease any further at higher concentrations. Immunohistologically, transforming growth factor-beta3 disappeared earlier in the tetrachlorodibenzodioxin group.Conclusions: Tetrachlorodibenzodioxin contributes to the pathogenesis of cleftpalate in vitro; however, direct intracellular effects are insufficient to fully accountfor the observed effects of tetrachlorodibenzodioxin, and it is possible that indirect mechanisms are also in play in vivo.