Differentiation of the digestive tract epithelium of the chick embryo cultured in vitro enveloped in a fragment of the vitelline membrane, in the absence of mesenchyme

Abstract

The capacity for autodifferentiation of the endoderm of the digestive tract of the chick embryo and the culture conditions which permit the differentiation of the endoderm in the absence of mesenchyme were studied using the vitelline membrane. 0 Endodermal epithelia are unable to develop, when cultured alone directly on the basal medium. However, when cultured enveloped in a fragment of the vitelline membrane according to Wolff's method (1961), the endodermal epithelia taken from various parts of 4- to 9-day digestive tracts survive and differentiate into a specific type of epithelium according to their origin, in the absence of mesenchyme. Similarly, when cultured enveloped in a fragment of the vitelline membrane in the absence of mesenchyme, 2.5-day (stage 14 to 18) endodermal pieces differentiate into several types of histologically identifiable digestive tract epithelia: those of oesophagus, proventriculus, gizzard, pancreas, liver, small intestine, and large intestine. The endodermal epithelia cultured in vitro enveloped in the vitelline membrane undergo the following sequence of events: On the 1st day, the epithelial cells lose their orientation. From the 2nd to the 3rd day, the cells orientate themselves again and form an organized epithelial layer. Then mitoses take place. From the 5th day onward, they start to differentiate. Serum in the basal medium is essential, but embryo extract is dispensable for the autodifferentiation of the endoderm under the present culture conditions. Egg-albumen or vitreous body can substitute for the vitelline membrane and allow survival and differentiation of the endoderm in the absence of mesenchyme. Similar endodermal differentiation is achieved even when the endoderm is cultured enveloped in a fragment of the vitelline membrane which has previously been separated mechanically into two layers or subjected to treatments with heat, 0.1 N HCl, 0.1 N NaOH, ethanol, acetone, or 5.5 M NaNO₂.