Multilayered keratinocyte culture used for in vitro toxicology.

Human keratinocytes are the most appropriate target cells for evaluating mechanisms of skin cytotoxicity and pharmacology of chemical agents. After having formed a confluent stratified epithelium with proliferating basal cells and differentiated cell layers, human keratinocytes were harvested after enzymatic detachment as stable, three-dimensional cell aggregates or used as adherent multilayers in microtiter plates to study the local cytotoxicity of different toxic compounds. The advantage of this test is that it uses the adequate target cells and that it evaluates both the ability of the test chemical to penetrate several cellular layers as well as the ability to interfere with cellular function. The end points are cell viability and cell metabolism, which are determined by neutral red uptake and MTT reduction, respectively. For the 13 chemicals evaluated in this study we found good correlation (r = .819) between the potency rankings of keratinocyte NR 50 values and in vivo irritancy data. There was also good agreement (r = .945) between ranking of these chemicals according to midpoint toxicity of both the 3T3 assay and the keratinocyte assay. This test system might be at the present stage a supplementation of the current test battery, which shall replace in vivo irritation tests like the Draize test.