STRATUM-CORNEUM LIPIDS OF HUMAN EPIDERMAL KERATINOCYTE AIR-LIQUID CULTURES - IMPLICATIONS FOR BARRIER FUNCTION

Purpose. The purpose of this study is to investigate the permeability barrier, i.e., the stratum corneum (SC) lipids, of human epidermal ker atinocyte air-liquid cultures and compare them with those of human SC. Method. The SC lipids composition was analyzed by TLC technique, the organization by electron microscopic procedure, and the phase transiti on temperature by Infrared spectroscopic method. Results. Electron mic roscopy demonstrated that The SC lipids of cultures were largely retai ned inside the corneocytes, and that the intercellular lipids lack bot h the basic unit repetition (ie., broad : narrow : broad : broad : nar row : broad of electron lucent bands) and the covalently-bound lipid e nvelope normally found in human SC. These characteristics are similar to those found in SC from patients with atopic dermatitis or psoriasis , or from animals with essential fatty acid deficiency, suggesting tha t the cultures may be hyperproliferative. In addition, the high free s terol content and the altered fatty acid/ceramide composition of these cultures argue that the compromised barrier function is linked to hyp erproliferation and lipid synthesis, or vice versa. Infrared spectrosc opic analyses confirm that there are major conformational differences between the lipids of human and cultured SC. Conclusions. The profound differences in SC lipid composition, organization and conformational properties attest that permeability alone is not a sufficiently sensit ive marker to define barrier equivalence between cultures and human sk in.