The role of connective tissue in the maintenance of epithelial differentiation in the adult.

Specimens of buccal mucosa and ear skin were introduced into the uteri of isologous rats and the animals maintained under estrogen stimulation for ten weeks, whereupon the uteri were removed and processed for light- and electron-microscopic examination. The majority of implants were successful with the epithelium having migrated to replace the adjacent uterine epithelium. Epidermis and oral epithelium growing on its own connective tissue in the uterus showed a normal pattern of histodifferentiation, including the formation of a thickened keratinized surface and appendages such as hair and sebaceous glands. Ultrastructurally, maturation was similar to that of normal tissue. Epidermis growing on uterine connective tissue did not form appendages but the ultrastructural pattern of cytodifferentiation was similar to control tissue. Buccal epithelium on the uterine stroma was markedly altered in its pattern of maturation, the epithelium appearing thinner than usual and showing a pattern of maturation resembling that of non-keratinization. These results suggest that normal histodifferentiation in epidermis and oral epithelium requires the presence of the appropriate connective tissue; in its absence epidermis has an intrinsic capacity for more or less normal cytodifferentiation but this is lacking in the buccal epithelium.