Objective: To investigate the possible involvement of 2,3,7,8- tetrachlorodibenzo-p-dioxin in the pathogenesis of cleft palate in mouse palatal cells. Materials and Methods: Palatal shelves of gestation day 12.5 ICR mouse foetuses were removed and cultured with serum. One day after the second passage, the medium was changed to serum-free and 2,3,7,8-tetrachlorodibenzo-p-dioxin was added at 1 ng/mL, 10 ng/mL, and 100 ng/mL. After culture for 1 and 3 hours, all cellular RNA was isolated from the cells. Expression of some cleft palate-related genes was analysed semiquantitatively using reverse transcriptase-polymerase chain reaction. Five genes (Tgfb3, Msxl, Lhx8, Fgfrl, and Fgfr2) were selected on the basis that functional disturbance of these genes causes cleft palate with high frequency. The data were compared with GAPDH. Results: In the first passage, many mouse embryonic palatal mesenchymal cells had spread out, and a number of monolayer spindle-shaped cells were identified. The cells were stable in the second passage and also in the serum-free medium. One hour after addition oj'2,3,7,8-tetrachlorodibenzo-p-dioxin, Tgfb3 mRNA expression was reduced at a concentration of 100 ng/mL. After 3 hours, Tgfb3, Msxl, and Lhx8 mRNA expression were also reduced. However, there was no effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the gene expression for Fgfrl and Fgfr2 mRNA. Conclusion: 2,3,7,8-Tetrachlorodibenzo-p-dioxin may contribute to the induction of cleft palate by suppressing Tgfb3, Msxl, and Lhx8 gene expression.
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