Effects of Gel Type Artificial Tears on Human Corneal Keratocytes and Conjunctival Epithelial Cells

Abstract

Purpose: To evaluate the biological effects and cytotoxicity of gel-type artificial tears on human corneal keratocytes and conjunctival cells in vitro. Methods: Human corneal keratocytes and conjunctival epithelial cells were exposed to Soothe and Systane at variable concentrations. Evaluations were conducted through an MTT-based calorimetric assay to measure the metabolic activity and through a lactate dehydrogenase (LDH) assay to assess cellular damage. Apoptotic response was examined using fluorescent microscopy and flow cytometric analysis, and cellular morphologic results were evaluated with a transmission electron microscope. Results: The inhibitory effects of corneal keratocyte and conjunctival cell proliferations increased at higher concentrations and longer exposure times to Soothe and Systane. The LDH titers increased after Soothe exposure, but showed no significant difference after Systane exposure. Soothe and Systane treatments both produced fluorescence, representing apoptotic cells. In flow cytometry, the maximal apoptotic response was observed for both types of artificial tears, although Systane showed less edema, as well as reduced cytoplasmic and nuclear cell degeneration compared to those of Soothe. Conclusions: The apoptotic responses of Soothe and Systane are associated with inhibitory effects of human corneal keratocyte and conjunctival epithelial cell proliferations. To inhibit the cellular proliferation of human corneal keratocytes and conjunctival epithelial cells, Systane may be less severe than Soothe at higher concentrations and longer exposure times.