ABSTRACT
The normal differentiation in vitro of whole skin from the limb-bud of the 5-day chick embryo is described briefly.
Epidermis isolated by tryptic digestion from the 5-day limb-bud and cultivated alone in vitro shows very few mitoses and keratinizes completely within 10 days.
Isolated epidermis grown in vitro in a medium containing excess vitamin A fails to keratinize, secretes mucus and sometimes becomes ciliated; mitoses are rare.
Isolated epidermis explanted in contact with cell-free intercellular material from the mesenchyme becomes oriented towards it and arranged around it in an epithelial manner.
These findings indicate that while the embryonic epidermis can differentiate in the absence of mesenchyme, contact with a basement membrane and the proximity of mesenchyme and its intercellular material are required for the normal growth and functioning of epithelial cells.
