The Effect Of Photodynamic Therapy With Visudyne On The Prevention Of Posterior Capsule Opacification

Objective To investigate the cytotoxic effect of photodynamic therapy (PDT) with Visudyne on cultured rabbit lens epithelial cells (RLECs) and human lens epithelial cell lines (HLECs). To determine the maximal effective safe dose of Visudyne. To study the mechanism of PDT-induced cytotoxicity in vitro. To evaluate the effect and safety of PDT on the prevention of posterior capsule opacification (PCO) in rabbit eyes.Methods (1) RLECs and HLECs were primary cultured and/or subcultured in vitro. Ultrastrcture of cells was observed using transmission electron microscopy. Cytotoxicity of different concentration of Visudyne and the maximal effective safe dose of PDT was tested by MTT assay. (2) Cell cycle of HLECs after PDT was analyzed and apoptotic change was evaluated using PI or Annexin V-FITC/PI assay by flow cytometry. Apoptotic morphological changes were observed by transmission electron microscopy. (3) Sodium hyaluronate with (PDT-treated group) or without (control group) Visudyne was injected into the capsular bag after lens extraction using phacoemulsification. After ten-minute incubation, laser was irradiated. Six weeks and twelve weeks postoperatively, PCO was evaluated in three ways:clinically, from photographs and histologically. Central posterior capsule thickness was measured. Transmission electron microscopy was also used to observe the ultrastrcture of cornea and iris.Results (1) RLECs were cultured successfully. The Laser alone or Visudyne at concentration of 0.125ug/ml or less had no cytotoxicity. Visudyne at concentration more than 0.125ug/ml showed dose-response cytotoxicity. PDT also showed dose-response cytotoxicity. (2) The cell population was significantly increased at the G2 phase and decreased at the S phase. Annexin V-FITC staining at 12h,24h and 48h after PDT were 77.17±2.55%,93.13±1.14%and 97.47±0.90%. Morphologic changes observed by transmission electron microscopy suggested typical signs of apoptosis. (3) Six and twelve weeks after surgery, PCO was showed much less in PDT-treated group than in control group. Six weeks after surgery, the scores of fibrotic PCO as well as regeneratory PCO were significantly lower in PDT-treated group than in control group. Twelve weeks after surgery, the scores of fibrotic PCO, but not those of regeneratory PCO, were lower in PDT-treated group than in control group. Histologically, the rings of Soemmering in PDT-treated group were much smaller than those in control group. There was no statistically significant difference between two groups in central capsule thickness. Ultrastrcture observed by transmission electron microscopy showed normal cornea and iris.Conclusions (1) Photodynamic therapy with Visudyne had strong cytotoxic effect on RLECs and HLECs in vitro. LECs were almost fully destroyed by PDT with Visudyne at concentration of 0.125ug/ml,5min incubation; power density 500mW/cm2 and 30J/cm2; 60s illumination. (2) The cyctotoxicity of PDT with Visudyne was induced by G2 arrest and mediated by apoptotic mechanism, which occurred shortly after photosensitization. (3) PDT using Visudyne effectively and safely decresed PCO in rabbit eyes.