In vitro RHE skin sensitization assays: Applicability to challenging substances

In the last 20 years, alternative approaches to the identification of skin sensitization hazards have been at the forefront of the 3Rs and have helped refine the validation and acceptance processes. However, experience with the local lymph node assay showed that, post-validation, challenges still occurred, particularly when a wider diversity of chemical substances was addressed, a situation which will arise with validated in vitro alternatives. In the present work, a range of substances potentially challenging to assess in current nonanimal OECD test guidelines were evaluated in several of the emerging in vitro alternatives. Twelve such substances (of which just over half were known skin sensitizers) were assessed in 4 assays, all based on reconstructed human epidermis (RHE) models. For hazard identification, the overall predictive accuracy ranged around 70% for three assays, although for one (SensCeeTox), it fell below 50% when human data was used as the benchmark. In most cases, sensitivity was high, such that sensitization was overpredicted. As the substances were challenging to assess in other nonanimal methods, the results indicate that the 3D RHE models may be a useful tool for assessing skin sensitization potentials without needing to revert to animal use.

EpiDerm (EPI-200), Interleukin-18 (IL-18)

acetone:olive oil (4:1), Hexaethylene glycol monododecyl ether, Resorcinol, Isopropyl myristate, Abietic acid, Aniline, Propyl paraben, 2-Chloro-6-methyl-3-aminophenol, 2-Hydroxy-4-methoxybenzophenone, Farnesol, Benzoyl peroxide, Amylcinnamyl alcohol, Tween 80