Promotion of ER stress: a potential therapeutic approach for PCO

Abstract

Purpose Posterior Capsule Opacification (PCO) remains a significant clinical problem following cataract surgery. Endoplasmic Reticulum (ER) stress has been shown to play a critical role in cell death and apoptosis. The aim of this study was to determine the relative effectiveness of ER stressors, thapsigargin (Tg) and arsenic trioxide (As2O3) on induction of cell death in human capsular bags. Methods FHL124 cell survival was assessed by Coomassie blue staining after 4 days. Induction of ER stress genes was detected using real‐time PCR and apoptosis assessed using the TUNEL assay. Human capsular bags were prepared from donor eyes and sealed with the Perfect Capsule device. The agents were again introduced to the bags for a 2 minute period prior to perfusion with EMEM alone. The bags were maintained in EMEM for 28 days and phase images were acquired throughout. Results Tg and As2O3 application to FHL124 cells induced significant up‐regulation of ER stress genes Bip, EIF2α, IRE1 and ATF6. FHL124 cells exposed for 2 minutes to both Tg and As2O3 for 4 days demonstrated reduced cell survival in a dose‐dependent manner. Moreover, TUNEL assay data showed that both Tg and As2O3 could induce FHL124 cell death by apoptosis. Application of the 100uM Tg and 100mM As2O3 to capsular bags for a 2 minute period using the perfect capsule system resulted in a total loss of viable cells following the 4 week culture period. Conclusion Thapsigargin and arsenic trioxide induce an ER stress in human lens epithelial cells, which is associated with a reduced cell survival and promotion of apoptosis. Using the perfect capsule system, a 2 minute exposure of either agent successfully killed all cells within the capsular bag and thus predicts putative therapeutic benefit in vivo.