Abstract
PurposeTo further improve in vitro models of the cornea, this study focused on the creation of a three-dimensional, stratified, curved epithelium; and the subsequent characterization and evaluation of its suitability as a model for biocompatibility testing.MethodsImmortalized human corneal epithelial cells were grown to confluency on curved cellulose filters for seven days, and were then differentiated and stratified using an air-liquid interface for seven days before testing. Varying concentrations of a commercial ophthalmic solution containing benzalkonium chloride (BAK), a known cytotoxic agent, and two relevant ocular surfactants were tested on the model. A whole balafilcon A lens soaked in phosphate buffered saline (BA PBS) was also used to assess biocompatibility and verify the validity of the model. Viability assays as well as flow cytometry were performed on the cells to investigate changes in cell death and integrin expression.ResultsThe reconstructed curved corneal epithelium was composed of 3–5 layers of cells. Increasing concentrations of BAK showed dose-dependent decreased cell viability and increased integrin expression and cell death. No significant change in viability was observed in the presence of the surfactants. As expected, the BA PBS combination appeared to be very biocompatible with no adverse change in cell viability or integrin expression.ConclusionsThe stratified, curved, epithelial model proved to be sensitive to distinct changes in cytotoxicity and is suitable for continued assessment for biocompatibility testing of contact lenses. Our results showed that flow cytometry can provide a quantitative measure of the cell response to biomaterials or cytotoxic compounds for both the supernatant and adherent cell populations. As a specifically designed in vitro model of the corneal epithelium, this quantitative model for biocompatibility at the ocular surface may help improve our understanding of cell-material interactions and reduce the use of animal testing.
Highlights
The cornea is comprised of three main cellular layers: the epithelium, stroma, and endothelium
To illustrate how cells cover the entire curved surface, pictures were taken after incubation with the metabolic dye thiazoyl blue tetrazolium bromide (MTT) (Figure 2)
All benzalkonium chloride (BAK) concentrations significantly reduced viability when compared to the BA Phosphate buffered saline (PBS) control (p,0.001)
Summary
The cornea is comprised of three main cellular layers: the epithelium, stroma, and endothelium. In vitro ocular toxicity testing has experienced a major advancement with the development of multilayered corneal epithelial cultures. The Draize test was developed as an ocular toxicity test in 1944 and involves the placement of test solutions on the eyes of living animals [5]. It became part of the United States Food and Drug Administration regulations in 1964 [6]. As the corneal epithelium represents the major barrier of the eye, many in vitro epithelial models have since been developed and proposed as alternatives to the in vivo Draize test. Since the 1960s, monolayer cell cultures have been developed using primary and immortalized corneal epithelial cell lines of rabbit and canine origin; and starting in the 1990s, the use of human-derived cells has become more popular [9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
