Inter-laboratory validation study of the Skin2 Dermal Model ZK1100 and MTT cytotoxicity assay kits

An inter-laboratory validation study was conducted to evaluate the potential of 4 chemicals to cause irritation with utilizing the Skin2 Dermal Model ZK1100 kit developed by Advanced Tissue Sciences, Inc. (formerly Marrow-Tech, Inc., La Jolla, California, USA). The chemicals tested were sodium dodecyl sulfate (SDS), 1-n-hexadecyl-pyridinium chloride monohydrate (CC), ethanol (EtOH), and dimethyl sulfoxide (DMSO). Eleven Japanese institutions participated in this validation research to evaluate the usefulness of the Skin2 Model ZK1100 kit in accordance with an identical protocol. None of the participating laboratories had previously used the Skin2 Model ZK1100 kit. The MTT-50 value obtained in the individual institutions was 42 to 91 micrograms/ml for SDS, 2.7 to 8.6 micrograms/ml for CC, 2.0 to 9.3% for EtOH, and 11.5 to 21.9% for DMSO. Reproducibility was reasonably good as noted when one test chemical was repetitively tested by the same investigator. MTT-50 values obtained with the present method correlated with DS20 values obtained with Draize's method (r = 0.9881) in one of the participant institutions. The irritation study using the Skin2 Model ZK1100 kit was easy to perform and generated quantitative data. When the test was repeated, reproducibility was demonstrated with a variation of less than 2 sigma. These data suggested that this newly developed in vitro method would be useful in toxicity screening studies in terms of both time and cost, and would serve as a useful alternative to the conventional methods of the eye irritation study.