PURPOSE: This study evaluated the concentration-dependent effects of glycerin on cellular metabolic activity in transformed human conjunctival and corneal epithelial cells exposed to desiccation stress.

METHODS: Human corneal epithelial cells from American Type Culture Collection (ATCC-HCEC) and the Riken Cell Bank (Riken-HCEC), as well as human conjunctival epithelial cells (HConjEC), were cultured until confluent. Six concentrations of glycerin (0.1%, 0.2%, 0.5%, 1.0%, 1.2%, and 1.5%) were tested against 50% Hank's balanced salt solution (HBSS) as a negative (no protection) control for each experiment. Cells were pre-exposed to test articles for one hour, after which solutions were removed from cells and the plates were left uncovered in a tissue culture hood with air-flow exposure for 0, 15, 30 or 45 minutes to induce air desiccation. Metabolic activity of the cells was determined by alamarBlue assay and measured in relative fluorescent units (RFUs). Integrated responses of the change in normalized RFUs were analyzed by calculating the areas under the curve (AUC) for each test well over the time course.

RESULTS: Minimal differences were observed between glycerin-pretreated cells and the HBSS control at the 0-minute time point across all three cell lines. Across the desiccation exposure periods, all six concentrations of glycerin produced significantly higher AUC values of normalized metabolic activity compared with the HBSS control in all cell lines tested.

CONCLUSIONS: Glycerin concentrations ranging from 0.1% to 1.5% demonstrated protective effects against air-induced desiccation in conjunctival and corneal epithelial cells. These findings indicate that glycerin may contribute to protection from desiccation stress and support ocular surface homeostasis.