Suitability of different reconstructed human skin models in the skin and liver Chip2 microphysiological model to investigate the kinetics and first‐pass skin metabolism of the hair dye, 4‐amino‐2‐hydroxytoluene

Abstract

The HUMIMIC skin‐liver Chip2 microphysiological systems model using the epidermal model, EpiDerm™, was reported previously to mimic application route‐dependent metabolism of the hair dye, 4‐amino‐2‐hydroxytoluene (AHT). Therefore, we evaluated the use of alternative skin models—SkinEthic™, EpiDermFT™ and PhenionFT™—for the same purpose. In static incubations, AHT permeation was similar using SkinEthic™ and EpiDerm™ models. Older Day 21 (D21) SkinEthic™ models with a thicker stratum corneum did not exhibit a greater barrier to AHT (overall permeation was the same in D17 and D21 models). All epidermal models metabolised AHT, with the EpiDerm™ exhibiting higher N‐acetylation than SkinEthic™ models. AHT metabolism by D21 SkinEthic™ models was lower than that by D17 SkinEthic™ and EpiDerm™ models, thus a thicker stratum corneum was associated with fewer viable cells and a lower metabolic activity. AHT permeation was much slower using PhenionFT™ compared to epidermal models and better reflected permeation of AHT through native human skin. This model also extensively metabolised AHT to N‐acetyl‐AHT. After a single topical or systemic application of AHT to Chip2 model with PhenionFT™, medium was analysed for parent and metabolites over 5 days. The first‐pass metabolism of AHT was demonstrated, and the introduction of a wash step after 30 min decreased the exposure to AHT and its metabolites by 33% and 40%–43%, respectively. In conclusion, epidermal and FT skin models used in the Chip2 can mimic the first‐pass skin metabolism of AHT. This highlights the flexibility of the Chip2 to incorporate different skin models according to the purpose.