ASSESSMENT OF THE OCULAR IRRITANCY POTENTIAL OF HAIR CONDITIONERS IN A 3-DIMENSIONAL IN-VITRO HUMAN SKIN MODEL

A three-dimensional human tissue model has been developed in our labor atory and used as a substrate for assessing ocular cytotoxicity and ir ritancy potential. The full-thickness model is a coculture of dermal f ibroblasts and epithelial cells (keratinocytes). Metabolically and mit otically active fibroblasts are seeded onto medical-grade nylon mesh, where they attach and secrete collagen and extracellular matrix protei ns. Then keratinocytes are seeded onto the top of this submerged strom al tissue, and the tissue grows into a multilayered epithelium. Histol ogic examination of this cellular coculture system reveals a cellular organization similar to the rabbit/human cornea. The resulting substra te 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 tr eated tissue is assayed for cytotoxicity (using MTT) over a period of time. The high correlation (r = 0.87) of our in vitro data with existi ng animal eye data shows the potential usefulness of these tissue subs trates as an in vitro alternative for evaluating the toxicity of hair care formulations.