Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (10) Evaluation of cytotoxicity test on CHL cells

Abstract

The present interlaboratory validation study was performed in order to evaluate the use of Chinese hamster lung cell lines that employs crystal violet staining (CHL–CVS) as an alternative cytotoxicity test to the Draize eye irritation test (Draize test) for cosmetic ingredients. Ten substances, nine of which were surfactants, were evaluated at seven laboratories in the first phase of the validation study; 15 substances including dyes and lipids were evaluated at seven laboratories in the second phase of the validation study; 14 substances including acids and alkalis were evaluated at four laboratories in the third phase of the validation study. The logEC 50 values obtained for CHL–CVS were compared with the maximal average Draize total score (MAS) for a 10% (w/v) solution of 38 cosmetic ingredients as well as isotonic sodium chloride solution. The interlaboratory coefficient of variation (CV) for EC 50s was 35.6%, which was considered to be within a tolerable range. The correlation coefficient and the Spearman's rank correlation coefficient between the in vitro and in vivo tests were −0.729 and 0.709, respectively. The prediction ability of the proposed method was assessed from the linear regression line for a MAS cut-off point of 15. According to this analysis, four substances (two alcohols and two acids) were determined to be false negative. The present study revealed the following characteristic factors of this method: (1) CHL–CVS could be applied to all the test substances including dyes and lipids in this study; (2) The results for medium-insoluble substances varied according to the laboratory; (3) The correlation between the in vivo and in vitro data for acids and alcohols (lower mono-ol) differed from that of the other substances. These results suggested that the CHL–CVS might have a potential to predict the Draize MAS if definite criteria can be established for the compounds to be applicable.