Abstract
Purpose: :
To evaluate the effects of sub-retinal injection of indocyanine green (ICG) on retinal function and to assess its effects on survival of cultured RPE.
Methods: :
Mice were given sub-retinal injections of (1 ul/eye) 0.5 mg/ml or 0.25 mg/mL of ICG in right eye. The left eyes of the same mice were injected with 1 ul of saline to serve as controls. Simultaneous bilateral electroretinograms (ERGs) were recorded prior to sub-retinal injection, and 24 h and 48 h after injection. Human retinal pigment epithelial cell line, ARPE-19 was cultured in normal (5 mmol) or high (25 mmol) glucose conditions. To assess the survival effect, cells were exposed to 10ul, 50ul, and 100ul of 0.1 mg/mL for 5 min followed by removal of ICG and replenish with fresh culture media. After 24 h viable cells count was performed by trypan blue staining and lactate dehydrogenase (LDH) release assay.
Results: :
The ERG responses were significantly altered in dye-injected eyes compared to their control, PBS-injected eyes. Mice injected with the higher dose of ICG (0.5 mg/ml) showed significant reduction of scotopic b-wave amplitudes at both 1(56%) and 2 days (59%) post challenge compared to the controls. In contrast the low dose of ICG (0.25 mg/ml) resulted in relatively low reduction of b wave amplitude at day 1 (31%) versus day 2 (54%). Similar levels of a-wave amplitude reduction were seen in both concentrations of ICG at day 1 and day 2. The exposure of ARPE-19 with ICG resulted in increased cell death and the response was concentration-dependent as evidenced by reduced survival in 100 ul group. Importantly, compared to normal glucose conditions, there was a larger ratio of cells death observed in ARPE-19 cells cultured under high glucose conditions.
Conclusions: :
Sub-retinal injection of both low and high dose ICG resulted in decreased ERG a- and b-wave amplitudes at both day one and day two post treatment, suggesting an acute effect of ICG on retinal function. The in-vitro data suggest that ARPE-19 cells in both low and high glucose conditions showed decrease cell survival following acute ICG exposure, with proportionately higher cell death in high glucose and higher ICG concentrations. Further studies are warranted to assess the chronic impact to ICG on retinal function and RPE survival.
Keywords: retinal culture • retinal pigment epithelium • drug toxicity/drug effects