Abstract
Purpose::
To evaluate ultraviolet, violet and blue light - induced damage of cultured human RPE cells in an effort to develop an in vitro model that can be used to evaluate IOL materials in protecting the retina from blue light.
Methods::
Human RPE cells, ARPE-19, were cultured in 4 groups: 1 control and 3 irradiated groups: 400, 420, and 435.8 nm light irradiated. The treated cells were then irradiated using a PRA integrated arc lamp system. Specific wavebands (400, 420, and 435.8 nm) were obtained by covering the cells with interference filters (Melles Griot). And then, three cell groups were irradiated for 3, 6 and 9 hours, respectively. Before each irradiation, the UV output in µW was measured with a Photodyne radiometer together with a sensor head. Calculated irradiance (W/cm2) for 400 nm was 0.038 W/cm2, and 0.017 W/cm2 for 420 nm, respectively. Also, the calculated energy levels (J/ cm2) for 400 nm were 410, 820, and 1230 J/ cm2, and 420 nm were 183, 367, and 549 J/ cm2. After irradiation, all 4 groups were further incubated for 24 hours while they were analyzed using the Alamar blue assay (Medicorp Inc.) for cell viability, and confocal microscopy (Carl Zeiss) for morphological assessment. Confocal analysis concentrated on the study of the cell nuclei (Hoechst 33342) and mitochondria (Rhodamine 123).
Results::
The Alamar blue assay results for 400 nm - exposed cells clearly showed energy level - dependent decreases in cell viability in comparison to non-irradiated control cells, while 420 nm and 435.8 nm - exposed cells showed similar viability as control cells at all energy levels. Morphological evaluation of 400 nm irradiated cells also showed the degradation of mitochondria and nuclei while 420 and 435.8 nm groups showed no significant difference.
Conclusions::
The findings suggest that violet and blue light-induced cultured RPE cell damage can be evaluated by assays that probe cellular and morphological viability, and that these two assays together provide a valuable in vitro model for evaluating IOL materials in protecting the retina from blue light.
Keywords: radiation damage: light/UV • retinal pigment epithelium