| Background: Tongue plays a critical role in the regulation of midface development especially the palate. At day 14 mouse embryos, tongue become flat gradually and then dropped into the mouth, after that the lateral palate take a rotation and extend toward the horizontal line, contact and fuse. One of the main mechanisms of cleft palate is the obstacle of palatal shelves'?horizontal elevation, this is directly relative to the sharp, the volume of tongue and whether it is withdrawl movement. The development of tongue began at day 11?mouse embryos, tongue primordium?beginning to intumescentiae at the base of the mouth gradually. At Embryo day 12, tongue continue to development until fill all the mouth. It begin to happen organization differentiation at day 13,the mesenchymal under the tongue epithelium have regional?aggregation, a few cell extend and develop to myoblast, the myotube begin to formation. Till embryo day 15, myoblast arrange to bind? already, there has more myofibrils in it. And at embryo day 18 , it has been well differentiated of striated muscle that the cell nuclei spread at the surrounding area.Retinoic acid (RA) is kind of vitamin A derivatives, it can be used as the addition reagent of cosmetics and also the medicine of dermatoses and cancer, which is common to see in daily life. Contact and intake excess amounts of RA has proven to be one of the important environmental factors of cleft palate and lip in human. This study adopts the animal model of cleft palate mice induced by retinoic acid, apply the immunohistochemical stains and real-time PCR method to detect the expression of skeletal muscle specific markers of the tongue muscle development in different stages.Objective: Through detect the expression of members of the myogenic determination factor family Myf5, MyoD and Myosin in mice developing tongue muscle induced by retinoic acid, explore whether the abnormal of tongue can be induced by retinoic acid in its development .Methods: We gave all-trans RA (100mg/kg) orally to E10 ICR pregnant mice and induce animal model with cleft palate. At different periods of tongue muscle development, using immunohistochemical staining and real-time PCR method, detect the exprese level and distribution of Myf5, MyoD, and using the immunohistochemical staining of Myosin, detecting the express level and distribution of Myosin protein and observe the?alignment of tongue myofibers.Results: 1, Immunohistochemical results show that Myf5 and MyoD expressed in the nucleus of tongue muscle cells, at E13 the quantity and express strength of positive cells reach the peak. AT E14.5 it trend to decrease; Myosin express in the cytoplasm, express stronger at E14.5 and the myofibers appear aberrant. Contrast to the normal group, the three skeletal muscle markers are declining in protein expression in the experimental group. 2, Real-time PCR results showed the same trends as protein, and mRNA expression of Myf5 and MyoD peaked at E13.The mRNA expression level of the two gene decreased continuing from E13 to E14.5? significantly after RA treatment (P < 0.01) .Conclusions: In the development of mice tongue muscle induced by retinoic acid, the abnormal low expression of Myf5,MyoD and Myosin suggest the delay of the growth and differentiation of tongue, and the abnormal development of tongue may be one of the mechanism of cleft palate. |
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