Further verification of an in vitro tier system for the identification of cosmetic ingredients that are not ocular irritants.

A tier evaluation system for the identification of cosmetic ingredients that are not ocular irritants was applied to 59 cosmetic ingredients, for which in vivo data were available. The tier system employs monolayer cultures of SIRC cells, an established cell line originally derived from rabbit cornea, and a threedimensional living dermal model (LDM; MATREX(TM)), which consists of human dermal fibroblasts in a contracted collagen lattice. The effects of ingredients on monolayer cultures of SIRC cells were determined by Crystal Violet staining (in the SIRC-CVS assay), and the effects on the LDM were measured by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (in the LDM-MTT assay). The classifications of eye irritancy predicted by the in vitro system were compared with previously reported data obtained with the in vivo Draize rabbit eye test. The in vivo classification was based on appearance of corneal damage, or a maximal average score (MAS) of 15 as the cut-off point. The SIRC-CVS assay was effective in the prediction of compounds that would be non-irritants at a concentration of 10%, while the subsequent LDM-MTT assay could predict non-irritancy at various lower and higher concentrations, including 10%. The tier system gave very few false-negative predictions, though false positives were unavoidable. Performing the LDM-MTT assay with an additional 73 ingredients gave similar results in the prediction of non-irritancy at various concentrations. Our findings indicate that the tier system may be suitable for the safety assessment of eye irritancy of ingredients intended to be used in cosmetics and medicated cosmetics in Japan.