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

Objective: To investigate the mechanism of cleft palate in mice induced by excessive all-trans retinoic acid (atRA). Methods: The pregnant mice were randomly divided into atRA-treated group (n=27) and control group (n=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. Results: At GD13-GD15, compared with the control, the ratio of BrdU-positive cells in the palatal mesenchyme of atRA-treated fetuses decreased significantly (P<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. Conclusions: atRA may lead to cleft palate by inhibiting the activation of Smad signaling pathway and affecting the proliferation of palatal mesenchymal cells.目的： 通过建立小鼠腭裂模型观察全反式维甲酸（all-trans retinoic acid，atRA）对胎鼠腭突间充质细胞增殖及转化生长因子β（transforming growth factor-β，TGF-β）/Smad信号通路的影响，探讨atRA诱发腭裂的机制。 方法： 将孕鼠根据体质量按随机数字表随机分为atRA组和对照组（每组各27只），于妊娠第10天（gestation day 10，GD10）上午8时，分别予以100 mg/kg atRA和等体积玉米油溶剂灌胃。HE染色观察GD13~GD15胎鼠上腭发育，5-溴脱氧尿嘧啶核苷（5-bromo-2-deoxyuridine，BrdU）免疫组织化学染色观察atRA对GD13~GD15胎鼠腭突间充质细胞增殖的影响，蛋白质印迹法检测胎鼠腭突间充质细胞内Smad2、磷酸化Smad2（phospho-Smad2，p-Smad2）、Smad4、Smad7的蛋白表达。 结果： 与对照组相同时间点相比，atRA组GD13~GD15胎鼠腭突间充质细胞BrdU阳性率均显著降低（P<0.05），尤其是GD14，atRA抑制率达（65.4±1.7）%。与对照组相同时间点相比，atRA组GD14和GD15胎鼠腭突间充质细胞p-Smad2和Smad4蛋白表达显著降低（P<0.05），GD13~GD15胎鼠腭突间充质细胞Smad7蛋白表达显著升高（P<0.05）。 结论： atRA可能通过抑制Smad信号通路的激活影响腭突间充质细胞增殖，从而导致腭裂的发生。.