Dermal Irritation in 3D Human Tissue Constructs
3-D reconstructed human epidermal (RHE) tissue constructs are organotypic in vitro models, which can be utilized in a variety of assays to evaluate the dermal irritation, corrosivity, cytotoxicity, phototoxicity, and/or anti inflammatory potential of test materials. Tissue viability is determined using the vital dye MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). The reduction of MTT in treated cultures is expressed as a percentage relative to untreated (negative control) cultures.
RHE tissue constructs are made from human epithelial cells, which are cultured on specially designed cell culture inserts. The cells differentiate to form a fully differentiated epidermis, complete with a functional stratum corneum (see picture below). An advantage of using 3-D tissues is that test materials are applied topically, so solids, undiluted final formulations, and insoluble test materials can be tested.
MTT, a vitality-indicating dye, is actively taken up by the tissues and subsequently reduced in the mitochondria of living cells. This chemical reaction produces a purple-colored compound (formazan) within the cells, causing the live tissues to turn deep purple in color. For specific assay procedures, please see Step-by-Step.
Assay Design: Quick Facts
Assay Model: organotypic RHE tissue constructs
Endpoints: Relative viability by MTT reduction, ET50 * (the exposure time that induces a 50% reduction in viability, relative to solvent controls), cytokine expression, dermal penetration, others
- For time-to-toxicity only. Alternate assay endpoints are detailed in the Applications section.