Effect of Indocyanine Green on the Growth and Viability of Cultured Human Retinal Pigment Epithelial Cells

The aim of this study was to evaluate the effects of indocyanine green (ICG), which is a fluorescent dye recently used for staining during manipulation of the internal limiting membrane (ILM) in surgery, on cultured human retinal pigment epithelial (HRPE) cells. Different concentrations, up to 0.25% (weight/volume), of ICG were added to the culture medium, which contained the cultured human RPE cells. Then the cell-growth curve and cell viability were assayed with a direct cell count and MTS cell proliferation kit, respectively. Two (2) models of experimentations, a dose-response group and a short-term application group, were designed. We obtained data for IC₅₀ values for 24-, 48-, and 72-hour ICG treatments, which were 0.062%, 0.041%, and 0.035%, respectively. This implies that the longer the culture duration, the lower the concentration of ICG, which can inhibit the HRPE cells. In the group of 3-day sequential incubations with ICG treatment, a 0.01% concentration significantly inhibited HRPE growth. In addition, HRPE cells were damaged immediately after ICG treatment, and the damage was ICG dose-related. In the sequential 3-day incubation, compared to the control group, the surviving HRPE cells of each treated group had the same growth rate. In conclusion, ICG has a relatively toxic effect on cultured HRPE cells, even in much lower concentrations than clinical nondilution status (0.25%). Since an ICG toxic effect on HRPE cells was found in our study (in vitro), we highly recommend staining the ILM with as low a concentration of ICG as possible, and washing out the residual intravitreal ICG as thoroughly as possible after finishing the peeling of the ILM.