Expression Of Smad2/3 In Normal Palate Development And Cleft Palate Induced By Retinoic Acid In Different Stages

Objective:The purpose of the present study was to observe the expression of Smad2/3 in normal palate development and cleft palate which induced by retinoic acid(RA) in the different stages and to elucidate the mechanism by which RA induced the cleft palate.Methods:There were 56 pregnant BALB/c mice of SPF level divided into four groups. The experimental group was treated with a single dose of retinoic acid(RA)(50mg/kg) on gestation day(GD) 10 or GD12 by gastric intubations via oral gavage. The RA was dissolved in corn oil. The control animals were treated with the equivalent volume of corn oil alone. The pregnant mice were euthanized by cervical dislocation on GD 17. Fetal mice were removed from the pregnant mice. Mice cleft palate were observated for the conclusion of the rate of deformity. After RA or corn oil alone treatment on GD 10 or 12,pregnant mice were euthanized by cervical dislocation on GD14、GD15. The embryonic palatal development were examined by light microscopy and the expression of Smad2/3 in mouse embryonic palate mesenchymal(MEPM) cells and medial edge epithelium(MEE)cells were measured by immunohistochemical staining.Results:The variation in the incidence of cleft palate induced by RA on GD10 or GD12 was significant(P﹤0.05). The results of HE staining showed that the palate shelves of control mice appose in the midline and fuse. The RA exposure at GD10 cause an small sized palate.Treatment with RA on GD12 produced a normal sized palate, but without fusion of the palate shelves. Expression of Smad2/3 protein was increased significantly in MEE cells and MEPM cells after RA treatment on GD10(P﹤0.05). These changes were not observed in the RA exposed on the GD12 group. There was no significant difference between the RA exposed on GD12 group and the control group(P﹥0.05).Conclusion:The occurrence of a cleft palate and the expression of Smad2/3 protein induced by RA varies depending on the stage of development.