[Reversibility of the morphological and functional dedifferentiation occurring in cultures of avian embryonic liver cells (author's transl)].

Primary cell cultures are established from 8-day quail embryo livers. During the first three days the culture is made up of areas of epithelial-like cells and scattered fibroblasts. The cytoplasm of the epithelial cells shows a high glycogen content as detected by the PAS reaction controlled with salivary amylase digestion. During the following days an important increase in the number of fibroblastic cells is observed. After 6-7 days of cultivation, the epithelial cells have disappeared and the culture is entirely fibroblastic. PAS technique does not show any trace of glycogen in these cultures which have been prolonged up to 45 days. Six-to 45-day primary cultures entirely made up of fibroblasts were associated with hepatic or pulmonary mesenchyme in organotypic culture for 3-4 days. In some cases the explant was first cultivated in vitro for 2 days and then grafted into a 5-day-old chick embryo on the chorioallantoic membrane for 6 days. In the secondary cultures hepatocytes showing an epithelial arrangement and a high glycogen content were observed. It appears from this observation that some of the primary culture fibroblasts are in fact dedifferentiated parenchymal cells. Such a dedifferentiation is a reversible phenomenon since the cells retain the ability to express their initial determination if they are placed in convenient environmental conditions. The role of the specific tissular arrangement in the stability of the differentiated state is discussed.