Modulation of Apoptosis Following Combination PEDF and Photodynamic Therapy for Choroidal Neovascularization in the Rat Model

Abstract

Abstract: : Purpose: Photodynamic therapy (PDT) using verteporfin is a clinically accepted therapy for choroidal neovascularization (CNV). We have shown that apoptosis may be a mechanism by which PDT is effective in CNV treatment. In addition we have shown that modulation of caspase and Bcl–2 family occurs after PDT of microvascular endothelial and retinal pigment epithelial cells in vitro. The purpose of this work was to investigate the effect of combination PEDF and verteporfin PDT of CNV in the rat model and determine the effect of PEDF on retina and CNV. Methods: Laser burns were applied in a peripapillary fashion in eyes of Brown–Norway rats and CNV was documented by angiographic leakage 3–4 weeks after laser. 2.5 ug PEDF was injected intravitreally followed by Verteporfin PDT to CNV 24 hours later using 6 mg/m2 verteporfin and laser irradiation using 600 mW/cm2 and 25 J/cm2 at 689 nm. Fluorescein angiography was performed 24 and 72 h after PDT and eyes were enucleated. TUNEL staining on sections after paraformaldehyde fixation and paraffin embedding was performed to evaluate retinal apoptosis of treated lesions. Results: TUNEL positivity was identified in the photoreceptors at 24h and 72h post PDT. At 72h eyes pretreated with PEDF prior to PDT showed increased endothelial apoptosis in the CNV compared with control PDT alone. Conclusions: PEDF may enhance the role of endothelial cell apoptosis in the mechanism of action of Verteporfin PDT treated CNV. Combination strategies using PEDF with PDT may provide a more targeted and effective therapeutic approach for the treatment of CNV.

Keywords: age–related macular degeneration • photodynamic therapy • apoptosis/cell death