Expression Of Wnt5a And Its Relationship With Shh And FGF-10 In Mouse Palatal Development And RA-induced Cleft Palate

Background: Cleft palate (CP) is one of the most common malformations among live births, occurring with an incidence of 1/700 in the world and 1.82‰in China. CP is caused by genetic factors and interaction with environmental factors. All-trans retinoic acid (at-RA) is the derivative of vitamin A, which plays an important role in embryogenesis, especially in formation of cleft palate as a teratogenic effector. However, mechanisms of at-RA inducing cleft palatogenesis are not clearly understood. The gene homology of human and mice is more than 99%, thus using mouse as the model of cleft palate to study its mechanisms is a trend. In current study, mouse model of RA-induced cleft palate were set up and morphological observations have carried out. Immunohistochemical staining and RT-PCR technique was performed to evaluate the expression of putative key signal molecules, such as Wnt5a, Shh and FGF-10 during the palatogenesis and RA-induced cleft palate.Objective: To study the temporal and spatial distribution of Wnt5a, Shh and FGF-10 in retinoic acid( RA)-induced cleft palate mouse to discover the mechanism and relationship of Wnt5a, Shh, FGF-10 signaling molecules in palatogenesis and RA-induced cleft palate.Methods: Using the mouse model of RA-induced cleft palate, we detected the expression and distribution of Wnt5a at ED14, ED15 and ED16 in control group and RA treated group by immunohistochemistry and RT-PCR (ED: Embryonic day). Results: 1. Of all the fetuses in RA-treated group, the CP rate is 100%. In control group, the palate shelves appose in the midline and fused. But in RA-treated group, the lift of palate shelves and the drop of tong were delayed and small palate shelves developed. Two palate shelves failed to fuse with each other. 2. Wnt5a expressed in both mesenchyme and epithelium in development of palate and showed temporal- spatial change. The expression of Wnt5a mRNA was up-regulated at ED15 in RA-induced cleft palate group compared with the control group. 3. Shh and FGF-10 are both expressed in the all different stage of palatogenesis. In control group, the expression model of Wnt5a was consistent with shh and FGF-10 expression. In RA-treated group the expression model of Wnt5a was consistent with the FGF-10 expression model.Conclusions: 1. After exposure of embryonic mice to RA on ED 10 days, abnormal palatal shelves form in small size, with lift of palate shelves and drop of tongue are delayed. Bilateral palate shelves fail to fuse with each other. 2. Wnt5a takes part in the development of palate, and shows temporal- spatial change. Wnt5a may cross talk with Shh and FGF-10 signaling molecules. 3. Abnormal expression of Wnt5a, Shh and FGF-10 in the RA-induced cleft palate indicates that RA may induce cleft palate by regulating Wnt5a, Shh and FGF-10 signaling molecules.