Human Induced Pluripotent Stem Cells-Derived Reconstructed Epidermal Skin Model as an Alternative Model for Skin Irritation

The limited availability of primary normal human epidermal keratinocyte (NHEK) has hampered the large-scale implementation of skin models in biomedical, toxicological, and pharmaceutical research. Therefore, in this study, we aimed to establish an induced pluripotent stem cell (iPSC)-derived epidermal skin model that is not limited by donor type and cell lifespan, and evaluate whether it is equivalent to the primary NHEK-derived reconstructed epidermal skin model (RHE) for skin irritation testing. The results show that high expression of OCT4, SOX2, KLF4, c-MYC, and SSEA-4, TRA-1-60, TRA-1-81 indicated that iPSCs were successfully generated from human fibroblasts in vitro. The expression levels of ectoderm or KC marker genes CGB, IVL, KRT10, KRT14, TP63, and TBP were close to those of NHEKs. This result confirms that iPSCs were successfully differentiated into iPSC-KCs. The expression levels of iPSC-derived-RHE in FLG (60), AQP3 (151), CLDN1 (30.6), IVL (209), KRT5 (39.3), KRT10 (39.2), TSLP (99), IL-6 (53.1), IL-8 (79.4), and TNF-a (91.5) were significantly higher than those in RHE. These results indicate that iPSC-derived RHE has extremely strong vitality and renewal capacity. Meanwhile, there was no significant difference between iPSC-derived RHE and SkinEthic in predicting skin irritation, which means that our iPSC-derived RHE performed well in the test. iPSC-derived RHE can replace other skin models for skin irritation testing related to cosmetics. This technology has the potential to generate an unlimited number of genetically identical skin models and improve the reproducibility of experiments.