Figure 2. Cytotoxicity test using cell counting kit-8 assay. Various concentrations of tert-Butyl hydroperoxide (tBHP; 0-50 mM) with or without clusterin (2 μg/ml) were used for 2 h in cultured human corneal endothelial cells. tBHP showed a dose-dependent cytotoxic effect on HCECs. At a concentration of 5 mM tBHP, tBHP caused 48.9±6.8% decrease in cell viability and clusterin increased cell viability, compared with the control (p=0.002, Mann-Whitney test). A indicates HCECs from a 40-year-old donor. B indicates HCECs from a 33-year-old donor.