The Characteristic And Mechanisms Of Tongue Development In Retinoic Acid-induced Cleft Palate In Mice

Background: Cleft lip or palate is one of the most common birth defects. Among the pathogenesis of cleft lip or palate, in addition to the dysplasia of palate, developmental disorder of surrounding structure can also give rise to cleft lip or palate,. It is known that micrognathia and glossoptosis are the key factors of cleft palate in Pierre Robin sequence. Cleft palate induced by abnormal development of tongue has been reported in many animal studies. Until now, the characteristic and mechanisms of tongue development during retinoic acid-induced cleft palate are still not clear.Objective: Based on mice cleft palate model induced by Retinoic acid(RA), characteristics of tongue development at different fetal periods were studied, whereas the possible mechanism on abnormal tongue development were evaluated. Through detect the expression of members of the myogenic determination factor family Myf5, Myo D and cell proliferation protein marker PH3 to analyze the differentiation and proliferation of tongue muscle.Methods: All-trans RA(100mg/kg) were introduced to C57BL/6J pregnant mice at E10.5 orally. Mice with cleft palate had been established successfully. Hematoxylin-eosin staining was used to analyze the characteristics of tongue development at E11.5, E12.5, E13.5, E14.5, E15.5 and E16.5, besides the expression of Myosin. The distribution and expression of the myogenic determination factor families(Myf5 and Myo D) were detected by immunohistochemical staining. Proliferation of tongue muscle cell was studied by cell proliferation protein marker PH3.Results: 1. Results of Hematoxylin-eosin staining showed that palate has already fused in control group at E16.5, whereas that palate shelves still located on the lateral of tongue, which failed to elevate and fuse in RA-treated group. Abnormalities of myofibrils at anterior of tongue and fewer muscle fibers at genioglossus wereobserved. Difference of morphology between two groups were observed at E11.5, E14.5 and E15.5. The rsults of Myosin IHC could be seen clearly at E14.5 and E15.5.Moreover,the muscle fibers arranged at special direction tidily at E15.5.Compared to control group,RA-treated group haved less muscle fibers. Although. Meanwhile, compared with control group,the expression of PH3 red uced early at E11.5 and E12.5.And the expression both of PH3 and Myf5 decr eased more severely at E13.5.At same point,the expression of Myf5 did decre ased significantly. And we detected the decreased expression both of Myf5 and Myo D at E 15.5. The expression of Myf5 at genioglossus between control gr oup and RA-treated group showed significant difference at later stage entirely(E13.5,E14.5,E15.5)Conclusion: It was concluded that abnormal tongue muscle development had effect on the cleft palate development which induced by retinoic acid, The inhibition on proliferation of mesenchymal cells derived from cranial neural crest induced by RA may relate to the abnormal tongue muscle development. Regulation of cell proliferation and differentiation of myoblast in tongue primordium by RA may cause the abnormal development of tongue muscle. Myoblast at genioglossus has the greatest impact.