Abstract
Purpose: :
Epithelial mesenchymal transition (EMT) of epithelial cells can be accompanied by increased expression of cyclooxygenase–2 (COX–2). The purpose of this study was to evaluate normal and cataractous canine lens epithelial cells (LEC) to determine if COX–2 expression is associated with the EMT–like changes that occur during posterior capsular opacification (PCO) formation, and if inhibition of the COX–2 pathway could prevent EMT–like changes.
Methods: :
Sample population included normal canine lens capsules without evidence of cataract and anterior capsulotomy samples from canine cataract patients. Samples underwent immunohistochemical staining using anti–COX–2 antibody. Quantitative RT–PCR (qRTPCR) was used to evaluate COX–2 mRNA expression in normal and cataractous LEC. An LEC wound healing model was used to evaluate whether inhibition of COX–2 would impede EMT of LEC, a characteristic of cataracts and PCO. Briefly, a 1mm wound was created in confluent cultured LEC followed by treatment with rofecoxib, celecoxib, or vehicle in unsupplemented media. LEC migration was monitored and Western immunoblotting was used to confirm decreased COX–2 expression during treatment.
Results: :
Cataractous LEC stained more intensely for COX–2 than normal LEC. qRTPCR demonstrated significantly increased COX–2 mRNA expression in canine cataracts compared to normal canine lenses. When wounded LEC were treated with either rofecoxib or celecoxib, there were decreased EMT–like changes compared to controls, and Western immunoblotting confirmed inhibition of COX–2.
Conclusions: :
COX–2 protein and mRNA expression is increased in cataractous LEC, where LEC are undergoing EMT and posterior migration. Inhibition of COX–2 prevented EMT–like changes in cultured LEC. Utilization of COX–2 inhibitors following cataract surgery may provide a safe PCO prevention strategy by inhibiting EMT and the migration of residual LEC.
Keywords: posterior capsular opacification (PCO) • EMT (epithelial mesenchymal transition)