RESUMO
Retinoic acid plays an important role in embryogenesis, by regulating morphogenesis, cell proliferation, differentiation, and extracellular matrix production. Also retinoic acid is a potent teratogen and induces a variety of limb and craniofacial malformations including cleft palate, that is the most common congenital malformation. Fibroblast growth factor 2 (FGF2) and fibroblast growth factor receptor 2 (FGFR2) are an important role in the secondary induction for the epithelial-mesenchymal transformation during development. Mutations in them, produce a congenital malformation in the skeletal system and the craniofacial tissue. It was of interest to explore the hypothesis of an inhibitory effect exerted by retinoic acid on the cell proliferating activity and the expression of FGF2 and FGFR2 in the developing palate in vivo. In the present study, author observed the expression of PCNA as a marker for the cell proliferating activity, FGF2 and FGFR2 to compare with developmental stages and locations in normal and retinoic acid-induced cleft palate. Retinoic acid was administered orally at gestational day (GD) 10 to ICR mice. The pregnant mice were sacrificed on GD 12, 13, 14, 15 to obtain the fetuses. Scanning electron microscope and immunohistochemistry was performed. In the retinoic acid-treated fetuses, palatal shelves did not elevate and cleft palate was induced. On GD 12, 13 in the palatal mesenchyme of the retinoic acid treated-fetuses, expression of the PCNA decreased. On GD 12 in the palatal epithelium of the retinoic acid-treated fetuses, expression of FGFR2 decreased, but after GD 13, the patterns of expression of FGFR2 were not affected. On GD 12, 13 in the palatal epithelium and mesenchyme of the retinoic acid-treated fetuses, expression of FGF2 decreased dramatically, but after GD 14, it was similar to that in the normal fetal palate. These results suggest that retinoic acid inhibits the cell proliferating activity and the expression of FGF2, FGFR2 in the palatal mesenchyme on GD 12, 13, which is critical in the developing palate, and elevation of palatal shelves is delayed and impaired. Moreover, it seems that retinoic acid inhibits the epithelial-mesenchymal transformation of epithelium. Finally, cleft palate is induced.
Assuntos
Animais , Feminino , Camundongos , Gravidez , Proliferação de Células , Fissura Palatina , Desenvolvimento Embrionário , Transição Epitelial-Mesenquimal , Epitélio , Matriz Extracelular , Extremidades , Feto , Fator 2 de Crescimento de Fibroblastos , Fatores de Crescimento de Fibroblastos , Fibroblastos , Imuno-Histoquímica , Mesoderma , Camundongos Endogâmicos ICR , Morfogênese , Palato , Antígeno Nuclear de Célula em Proliferação , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos , TretinoínaRESUMO
The distribution of transforming growth factor -alpha (TGF -alpha ) and epidermal growth factor (EGF) on the cardiovascular system of developing mouse embryos of gestational age 7 to 12 days were immunohistochemically (ABC method) studies to investigate the differential expression of these growth factors. Paraffin embedded sections were immunostained with antibodies for TGF -alpha and EGF. In the 8 -day -old mouse embryos, the endocardial tissue, myocardial tissue and cardiac jelly were all TGF -alpha stained. EGF stain was observed in the cardiac jelly and myocardial tissue but was not observed in the endocardial tissue. This suggests that in the initial phase of the cardiovascular system development, TGF -alpha function as earlier growth factor than EGF. The 9, 10 and 11 -day -old embryos showed TGF -alpha stain in the broad spectrum of developing cardiovascular tissues such as, the bulbus cordis, primitive atrium, sinus venosus, aortic sac, dorsal aorta, vitelline artery, endocardial cushion tissue, and myocardium of primitive ventricle. However, EGF stain was observed only in the bulbus cordis, primitive atrium and endocardial tissue. This finding indicates that TGF -alpha function as a more extensive growth factor than EGF. The 12 -day -old embryos showed stronger EGF stain than TGF -alpha in the primitive ventricle, bulbus cordis, and endocardial tissue. This suggests that EGF function as a more growth factor than TGF -alpha at this particular developmental stage and plays important role at the end stage of the primitive heart development.