Comparison of Two in vitro Models to Assess Ocular Irritation

Abstract

Abstract: : Purpose:To compare and contrast two commercial in vitro models to understand their potential to serve as an early predictive tool to assess ocular irritation of selected topical ophthalmic compounds. Mat–Tek’s EpiOcular^TM system consists of normal human–derived keratinocytes while SkinEthic’s Human Corneal Epithelium model consists of immortalized human corneal epithelial cells. Both systems are 3–dimensional cultures grown on inserts at the air–liquid interface in a chemically defined medium. Methods:A series of compounds were chosen based on literature reports of their irritancy potential. Upon receipt of the in vitro model inserts, they were transferred to plates containing medium and incubated at 37°C overnight prior to treatment with test compound. The test article was applied to the apical surface of the culture at the appropriate volume to deliver the desired concentration. After the 60–minute incubation at 37°C, the cultures were washed with PBS and the MTT assay was performed to assess tissue viability. Each compound was tested in duplicate and negative controls were run in parallel. Data were expressed as a percentage of viable cells relative to the corresponding negative control. Results:Based on this side–by–side comparison of the assays, both assays appear equivalent in their ability to detect irritancy of the compounds tested. There is a linear dose response curve for both the systems with concentrations ranging from 0.001 percent to 2 percent. Conclusions:SkinEthic’s model was preferred due to decreased material requirements, along with fewer steps prior to and during the experimental procedure. The fact that SkinEthic’s model employs human corneal cells is also an important consideration for ophthalmic products. As an early screen, an assay that is predictive, has fewer steps, and requires less bulk material, is highly desirable.

Keywords: cornea: epithelium