[Action of human serum on differentiation of skin in vitro. Morphological data and study of the incorporation of labeled amino acids].

Epithelial-mesodermal tissue interactions have been shown to be required for normal cytodifferentiation of chick embryo skin. Six-day limb skin does not develop in a protein free chemically defined medium, but keratinization has been observed in medium containing chicken serum. In the present study the authors show that the addition of human serum may stimulate the in vitro differentiation of explants of six-day chick embryo skin. Human serum is able to support skin keratinization and this finding has been confirmed by histological and histochemical criteria. Synthesis of proteins in tissue cultures supplemented with human serum has been studied by use of labeled amino acids such as H3-Leucine and C14-Cystine. These incorporation studies show the existence of macromolecular factors in human serum which may be responsible for the observed skin differentiation.