In vitro effects of verteporfin on ocular cells

Photodynamic therapy (PDT) laser light in conjunction with the benzoporphyrin derivative verteporfin is a current clinical treatment for choroidal vascular diseases such as age-related macular degeneration. The aim of this study was to examine the effects of PDT laser-activated and inactive verteporfin on various cultured ocular cells.

Primary human scleral fibroblasts (hFibro), primary human trabecular meshwork (TM) cells (hTMC), primary porcine TM cells (pTMC), and a human retinal pigment epithelial cell line (ARPE-19 cells) were treated with verteporfin with and without activation by PDT laser. Cell viability was determined according to mitochondrial enzyme activity (3-(4,5- dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide assay).

PDT laser treatment alone was insufficient to cause significant cell death in any of the cell types tested. Twenty-four-hour exposure to inactive verteporfin (without PDT laser) caused a dose-dependent decrease in cell viability in hFibro and hTMC, and to a lesser extent ARPE-19 cells. Verteporfin (0.5 µg/ml) without PDT laser activation caused a slight but statistically insignificant reduction in cell viability in hFibro (81.5% ± 19.3%), pTMC (82.9% ± 6.7%), hTMC (80.3% ± 7.7%), and ARPE-19 cells (84.5% ± 14.9%). Verteporfin (0.5 µg/ml) plus 50 µJ/cm(2) PDT laser treatment significantly decreased viability in hFibro (13.5% ± 3.3%), pTMC (7.1% ± 1.5%), hTMC (11.1% ± 5.2%), and ARPE-19 (44.5% ± 7.8%). Similar results were obtained in cells where verteporfin incubation was followed by washout before PDT laser, indicating that verteporfin is internalized by the studied cell lines.

PDT laser-induced cell death was obtained with coincubation of verteporfin or preincubation followed by washout. These results suggest a potential future use of PDT therapy for selective in vivo removal of targeted ocular cells beyond the current use for destroying vascular endothelial cells.