[Mechanism of cleft palate in C57BL/6N mice induced by retinoic acid].

To investigate the mechanism of cleft palate in mice induced by excessive all-trans retinoic acid (atRA). The pregnant mice were randomly divided into atRA-treated group (27) and control group (27). atRA-treated group was given by gavage a single dose of atRA (100 mg/kg) at 8: 00 AM on gestation day 10 (GD10) and the control group was given by gavage the isopyknic corn oil. At GD13-GD15, the fetal mice palate development was observed by HE staining. The mouse embryonic palatal mesenchymal cell proliferation was detected by 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry. The expressions of Smad2, phospho-Smad2 (p-Smad2), Smad4 and Smad7 in mouse embryonic palatal mesenchyme were analyzed by Western blotting. At GD13-GD15, compared with the control, the ratio of BrdU-positive cells in the palatal mesenchyme of atRA-treated fetuses decreased significantly (0.05), especially at GD14, atRA inhibition rate was (65.4±1.7)%. Moreover, atRA decreased the levels of p-Smad2 and Smad4 in embryonic palate mesenchymal cells, whereas the expression of Smad7 was significantly increased at GD14 and GD15. atRA may lead to cleft palate by inhibiting the activation of Smad signaling pathway and affecting the proliferation of palatal mesenchymal cells.