A three-dimensional in vitro model for the study of ocular cytotoxicity and irritancy

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 co-culture 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 epithelium. Histological examination of this cellular co-culture 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 test) is performed. The treated tissue is assayed for cytotoxicity and irritancy (MTT and PGE(2), respectively) over a period of time. The high correlation (R > 0.81) of our in vitro data to existing animal eye data shows the potential usefulness of these tissue substrates as an in vitro alternative for evaluating the toxicity of test agents from diverse chemical classes.