DEVELOPMENT OF A STRATUM-CORNEUM AND BARRIER FUNCTION IN AN ORGANOTYPIC SKIN CULTURE

The stratum corneum of human skin is responsible for maintaining the e pidermal permeability barrier, We have developed a bilayered skin cult ure (SC) which forms a corneum 35 +/- 1 cell layers thick 21 days afte r being raised to the air-liquid (A/L) interface. By the 7th day after raising to the A/L interface the corneocytes were irregularly shaped and had cross-sectional areas (CSA) of greater than or equal to 300 mu m(2). By the 21st day the corneocytes had assumed polygonal shapes an d had a CSA (100-250 mu m(2)) similar to that of human foreskin. The t otal lipid (TL) content of the corneum averaged 5-7% of the lyophilize d weight. Ceramide content increased from 20% of TL at day 7 of A/L in terface culture to 30% at dag 21. Triglycerides decreased from 43% to 17% of TL during the same period. Free fatty acids comprised 5.5% of T L at day 21 of A/L interface culture. The intercorneocyte spaces conta ined stacks of lipid lamellae. However, the stacks lacked the Landmann unit repeat. Abnormal lamellar structures were observed in both the i ntra- and extracorneocyte spaces. Transepidermal mater loss (TEWL) was > 4mg/cm(2) per h throughout the culture period. Lipid supplementatio n of the culture medium and culturing in a low humidity environment im proved barrier function by 50%. However, the effects mere not additive . The SC developed a near-normal corneum, but did not achieve barrier competence, due at least partially to abnormalities in lipid compositi on and organization. Improvement of barrier function with lipid supple mentation or low humidity indicates that modifications of the culture environment may facilitate the SC in assembling a permeability barrier equivalent to human skin.