Abstract
Purpose::
These studies were designed to assess the performance of the Clonetics Human Corneal Epithelial Model in evaluating irritancy response to different classes of chemicals, and loss and recovery of ocular barrier function after chemical exposure.
Methods::
The Clonetics Human Corneal Epithelial Model culture system was used to evaluate 23 compounds in various chemical classes at a total of 34 different concentrations. The cytotoxicity response of the culture system was evaluated for irritancy potential and time-to-toxicity was determined using the MTT cytotoxicity assay. Data was analyzed to determine a prediction model that separates ocular irritants from non-irritants. Barrier properties of the model system were characterized by trans-epithelial electrical resistance (TEER). TEER data were measured up to 48 hrs. after exposure of selected compounds.
Results::
Cytotoxicity results were compared with Draize Modified Maximum Average Scores (MMAS), and with the irritancy categories of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). Irritancy response showed sensitivity (irritating chemicals identified correctly) of 100% (11/11), specificity (non-irritating chemicals identified correctly) of 70% (16/23), and an overall concordance of 79% (27/34). Barrier properties were also evaluated as an alternate endpoint for noninvasive irritancy testing. The system exhibited epithelial barrier properties consistent with the formation of intact epithelium. TEER measurement results for multiple lots of models averaged >1700 Ω×cm2, which approaches the values observed in ex vivo corneal tissue. TEER typically decreased by greater than 80% within 5 minutes of exposure for most compounds evaluated, including some designated as non-irritants. The culture process was continued after removal of these treatments to allow for evaluation of corneal epithelial recovery. Complete recovery was observed within 24 hrs. in some cases.
Conclusions::
These results indicate that the Clonetics Human Corneal Epithelial Model is a robust in vitro system for the evaluation of corneal epithelial function and response.
Keywords: cornea: epithelium • ocular irritancy/toxicity testing