Differentiation of the yolk-sac endoderm under the influence of the digestive-tract mesenchyme

To reveal differentiation potency of yolk-sac endoderm, this tissue from quail embryos was cultured alone or in association with digestive-tract mesenchymes of chick embryos. When yolk-sac endoderm was cultured alone in vitro, the endoderm of the area vitellina differentiated into the yolk-sac parenchyma, but the endoderm of the extraembryonic area pellucida (EEAP) failed to differentiate into yolk-sac parenchyma, and the endoderm of the area vasculosa became necrotic. When endoderm of the area vitellina was cultured in association with digestive-tract mesenchymes, all the endodermal cells developed into yolk-sac parenchymal cells after two days. Later, basophilic cells appeared among them, and differentiated into both mesenchyme-specific epithelia and intestinal-type epithelium with a striated border, and villi were also formed. Goblet cells appeared in all types of recombinations. The endoderm of the EEAP cultured with digestive-tract mesenchymes gave similar results to that of the area vitellina. In contrast, endoderm of the area vasculosa, when cultured with digestive-tract mesenchymes, became necrotic. The present investigation demonstrated that the endoderms of the area vitellina and of the EEAP differ in self-differentiation potency, and that their developmental fates can be modified by the influence of digestive-tract mesenchymes. These endoderms can differentiate into the mesenchyme-specific epithelia, though they often differentiate also into the intestinal-type epithelium.