In vitro organogenesis of pancreas in Xenopus laevis dorsal lips treated with retinoic acid

摘要

Dorsal lips of Xenopus laevis may differentiate into pancreas after treatment with retinoic acid in vitro. The dorsal lip region is fated to be dorsal mesoderm and anterior endoderm. Dorsal lip cells isolated from stage 10 early gastrula differentiate into tissues such as notochord, muscle and pharynx. However, in the present study, dorsal lips treated with 10~(-4) M retinoic acid for 3h differentiated into pancreas-like structures accompanied by notochord and thick endodermal epithelium. Sectionsof the explants showed that some cells gathered and formed an acinus-like structure as observed under microscopes. In addition to the morphological changes, expressions of the pancreas-specific molecular markers, XIHbox8 and insulin, were induced in retinoic acid-treated dorsal lip explants. Therefore, it is suggested that retinoic acid may induce the dorsal lip cells to differentiate into a functional pancreas. However, continuous treatment with retinoic acid did not induce pancreas differentiation atany concentration. Dorsal lips treated with retinoic acid within 5h after isolation differentiated into pancreaslike cells, while those treated after 15h or more did not. The present study provided a suitable test system for analyzing pancreas differentiation in early vertebrate development.