The interaction of indocyanine green with human retinal pigment epithelium
Andrew A Chang1, Meidong Zhu, Frank Billson
1Department of Clinical Ophthalmology, The University of Sydney, Australia.
Insights
Human retinal pigment epithelium (RPE) cells internalize indocyanine green (ICG) dye. ICG uptake by RPE cells is relevant for interpreting indocyanine green angiography results.
Area of Science:
- Ophthalmology
- Cell Biology
- Biochemistry
Background:
- Indocyanine green (ICG) is a fluorescent dye used in ophthalmology.
- Retinal pigment epithelium (RPE) cells play a crucial role in retinal health and function.
- Understanding the interaction between ICG and RPE cells is important for interpreting diagnostic imaging.
Purpose of the Study:
- To investigate the in vitro interaction between human RPE cells and indocyanine green (ICG).
- To determine the impact of cellular conditions on ICG uptake by RPE cells.
- To assess the clinical relevance of RPE cell ICG interaction in angiography.
Main Methods:
- Primary human RPE cells were cultured and incubated with ICG.
- Infrared fluorescence microscopy was employed to detect and quantify cellular ICG fluorescence.
- The effect of ouabain, a known cellular toxin, on ICG uptake and RPE cell viability was examined.
Main Results:
- Human RPE cells demonstrated significant uptake of ICG, exhibiting strong infrared fluorescence.
- Short-term ouabain exposure (24 hours) reduced ICG fluorescence without affecting cell viability.
- Prolonged ouabain exposure (72 hours) decreased cell viability and paradoxically increased ICG fluorescence.
Conclusions:
- Human RPE cells actively internalize indocyanine green (ICG).
- ICG uptake may involve active transport mechanisms, as suggested by reduced fluorescence after short-term ouabain exposure.
- Altered ICG uptake following prolonged ouabain exposure might be due to compromised cell membrane integrity, impacting fluorescence patterns in ICG angiography.
Purpose:
This study sought to examine the in vitro interaction of human RPE cells with indocyanine green (ICG). The interaction between ICG and the RPE may have clinical relevance in the interpretation of clinical ICG angiography.
Method:
Cultured primary human RPE cells were incubated with ICG. Infrared fluorescence microscopy was used to detect RPE cell ICG fluorescence. The proportions of cells exhibiting ICG infrared fluorescence were quantified. Separate RPE cell populations were incubated with ouabain for 24 and 72 hours, respectively, before addition of the ICG to examine its effect on the uptake of ICG. The effect of ouabain on cell viability was assessed with trypan blue exclusion.
Results:
Normal human RPE cells incubated with ICG exhibited strong infrared fluorescence. Exposure to ouabain for 24 hours before incubation with ICG had little effect on cell viability but significantly reduced cellular ICG fluorescence. In contrast, exposure to ouabain for 72 hours reduced cell viability and increased cellular ICG fluorescence.
Conclusions:
Cultured human RPE cells take up ICG dye. ICG uptake by RPE cells may involve active transport, as cells incubated with ouabain for 24 hours showed no reduction in cell viability but exhibited reduced infrared fluorescence. The paradoxical increased uptake of ICG into the cells after more prolonged exposure to ouabain may be due to ICG's movement through the damaged cell membrane. Fluorescence due to ICG uptake by RPE has clinical relevance in that it contributes to the fluorescence patterns observed in ICG angiography.
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