The Center for Alternatives to Animal Testing is an academic center affiliated with the Division of Toxicological Sciences in the Department of Environmental Health Sciences of the Johns Hopkins University Bloomberg School of Public Health.

 

Johns Hopkins School of Public Health

Commemorative Booklet for CAAT 20th Anniversary Symposium

Corneal Organ Culture Model for Assessing Ocular Irritancy

Keping Xu and Fu-Shin Yu
Medical College of Georgia, Augusta

For five decades, the Draize test has remained the accepted method for evaluating the potential of test material to cause eye irritation or injury. Criticisms of this method focus on the inhumane treatment of animals and the irreproducibility of the subjective scoring procedure. There is a great demand for a mechanistic-based in vitro testing system that will minimize the use of animals in chemical toxicity tests.

Recently, we adapted a simple, long-term organ culture method as an ex vivo model for chemical toxicity tests. Here, toxicity can be assessed by applying test chemicals to the surface of the cultured corneas. Since this system more closely resembles an in vivo testing system than cell culture, it should serve as an appropriate model for chemical safety tests. The corneas we use are prepared from the bovine (or porcine) eyes, economical and resourceful by-products of meat industry; no live animals are euthanized for testing. Using this system, we examined corneal response to chemicals in several paradigms:

We maintained excised bovine corneas in a serum-free medium and examined the effects of two surfactants, SDS and BAC. We found that both surfactants caused alteration of the culture corneas in a concentration-dependent manner. Furthermore, the long-term culture model allows assessment of the functional recovery of the corneas after chemical exposure, a key parameter of the in vivo Draize test. Incubation of 3% SDS (Draize score 16.9) initially caused much leakage; however, by day 4, a functional epithelial barrier is formed in the treated cornea, indicating the corneal injury caused by 3% SDS can be repaired. No evidence of recovery was observed when corneas were exposed to 15% SDS (Draize score 59.2; severely irritating).

Thus, assessing recovery of corneal function is useful not only for predicting ocular irritancy but also for providing a better understanding of mechanisms of damage and the response of cells at tissue levels. Taken together, the combination of corneal organ culture and measurement of corneal epithelial permeability and DNA-binding activity of stress-response transcription factors following chemical exposure has the potential to be a simple and effective alternative method for screening and predicting toxicity profiles of chemicals.