Development of a stratum corneum and barrier function in an organotypic skin culture

The stratum corneum of human skin is responsible for maintaining the epidermal permeability barrier. We have developed a bilayered skin culture (SC) which forms a corneum 35 +/- 1 cell layers thick 21 days after 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 > or = 300 microns 2. By the 21st day the corneocytes had assumed polygonal shapes and had a CSA (100-250 microns 2) similar to that of human foreskin. The total lipid (TL) content of the corneum averaged 5-7% of the lyophilized weight. Ceramide content increased from 20% of TL at day 7 of A/L interface culture to 30% at day 21. Triglycerides decreased from 43% to 17% of TL during the same period. Free fatty acids comprised 5.5% of TL at day 21 of A/L interface culture. The intercorneocyte spaces contained stacks of lipid lamellae. However, the stacks lacked the Landmann unit repeat. Abnormal lamellar structures were observed in both the intra- and extracorneocyte spaces. Transepidermal water loss (TEWL) was > 4 mg/cm2 per h throughout the culture period. Lipid supplementation of the culture medium and culturing in a low humidity environment improved barrier function by 50%. However, the effects were not additive. The SC developed a near-normal corneum, but did not achieve barrier competence, due at least partially to abnormalities in lipid composition and organization.(ABSTRACT TRUNCATED AT 250 WORDS)