Assessment of the Ocular Irritancy Potential of Hair Conditioners in a Three-Dimensional in Vitro Human Skin Model

Abstract

A three-dimensional human tissue model has been developed in our laboratory and used as a substrate for assessing ocular cytotoxicity and irritancy potential. The full-thickness model is a coculture of dermal fibroblasts and epithelial cells (keratinocytes). Metabolically and mitotically active fibroblasts are seeded onto medical-grade nylon mesh, where they attach and secrete collagen and extracellular matrix proteins. Then keratinocytes are seeded onto the top of this submerged stromal tissue, and the tissue grows into a multilayered pithelium. Histologic examination of this cellular coculture system reveals a cellular organization similar to the rabbit/human cornea. The resulting substrate has been used effectively to study the effects of a variety of test compounds (surfactants, powders, creams) at diluted or full-strength concentrations in a time-course assay. The protocol mimics the way in which in vivo animal testing (Draize eye testing) is performed. The treated tissue is assayed for cytotoxicity (using MTT) over a period of time. The high correlation (r = 0.87) of our in vitro data with existing animal eye data shows the potential usefulness of these tissue substrates as an in vitro alternative for evaluating the toxicity of hair care formulations.