The ECVAM International Validation Study on In Vitro Tests for Acute Skin Irritation: Report on the Validity of the EPISKIN and EpiDerm Assays and on the Skin Integrity Function Test

ECVAM sponsored a formal validation study on three in vitro tests for skin irritation, two employing reconstituted human epidermis models (EPISKIN, EpiDerm) and the skin integrity function test (SIFT), which employs ex vivo mouse skin. The goal of the study was to assess whether the in vitro tests would predict in vivo classifications according to the EU classification scheme, R 38 and No-label (i.e. non-irritant). 58 chemicals (25 irritants and 33 non-irritants) were tested, having been selected to give broad coverage of physico-chemical properties, and an adequate distribution of irritancy scores derived from in vivo rabbit skin irritation tests. In Phase 1, 20 of these chemicals (9 irritants and 11 non-irritants) were tested with coded identity by a single (lead) laboratory for each of the methods, to confirm the suitability of the protocol improvements introduced after a prevalidation phase. When cell viability (evaluated by the MTT reduction test) was used as the endpoint, the predictive ability of both EpiDerm and EPISKIN was considered sufficient to justify their progression to Phase 2, while the predictive ability of the SIFT was inadequate. Since both the skin models provided false predictions around the in vivo classification border (rabbit Draize test score 2), the release of the cytokine, interleukin-1a (IL-1¿), was also determined. In Phase 2, each human skin model was tested in three laboratories, with 58 chemicals. The main endpoint measured for both EpiDerm and EPISKIN was cell viability. In samples from chemicals which gave MTT assay results above the threshold of 50% viability, IL-1a release was also measured, to determine whether the additional endpoint would improve the predictive ability of the tests. For EPISKIN, the sensitivity was 75% and the specificity was 81% (MTT assay only); assessed with the combination of the MTT and IL-1a assays, the sensitivity increased to 91%, with a specificity of 79%. For EpiDerm, the sensitivity was 57% and the specificity was 85% (MTT assay only), while the predictive capacity of EpiDerm was not improved by the measurement of IL-1a release. Following independent peer review, in April 2007 the ECVAM Scientific Advisory Committee endorsed the scientific validity of the EPISKIN test as a replacement for the rabbit skin irritation method, and of the EpiDerm method for identifying skin irritants as part of a tiered testing strategy. This new alternative approach will probably be the first in vitro toxicity test to replace the Draize rabbit skin irritation test in Europe and internationally, since, in the very near future, new EU and OECD Test Guidelines will be proposed for regulatory acceptance.

SPIELMANN Horst;  HOFFMANN Sebastian;  LIEBSCH Manfred;  BOTHAM Phil;  FENTEM Julia;  ESKES Chantra;  ROGUET Roland;  COTOVIO Jose;  COLE Thomas;  WORTH Andrew;  HEYLINGS Jon;  JONES Penny;  ROBLES Catherine;  KANDAROVA Helena;  GAMER Armin;  REMMELE Marina;  CURREN Rodger;  RAABE Hans;  COCKSHOTT Amanda;  GERNER Ingrid;  ZUANG Valerie; 

2008-02-22

FRAME

JRC42254

0261-1929,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC42254,