Indocyanine green induces apoptosis in human retinal pigment epithelial cells

PURPOSE: To examine whether indocyanine green (ICG) dye induces apoptosis in human retinal pigment epithelial (RPE) cells. DESIGN: Laboratory investigation. METHODS: Pure cultures of human RPE cells were isolated. Retinal pigment epithelial cells were incubated with different concentrations of ICG dye (1 mg/ml, 5 mg/ml, or 20 mg/ml) for 30 minutes. The rate of RPE cell apoptosis was assessed with Annexin V-FITC staining and propidium iodide (PI) by flow cytometry. RESULTS: Retinal pigment epithelial cells maintained their monolayer morphology after incubation with ICG dye. However, ICG induced a statistically significant amount of apoptosis in RPE cells at all the concentrations (1 mg/ml, 5 mg/ml, and 20 mg/ml) after 30 minutes of incubation (P <.05). The solvent solution alone (without the ICG dye) did not induce any significant apoptosis in RPE cells, when compared with culture medium. CONCLUSIONS: The incubation of RPE cells with ICG dye increased the number of apoptotic RPE cells in vitro. Our findings indicate that the decision over the intravitreal application of ICG dye needs to be made with caution.