Activation of SRC kinases signals induction of posterior capsule opacification.

PURPOSE Posterior capsule opacification (PCO) is a complication of cataract surgery resulting from the proliferation, migration, and epithelial-to-mesenchymal transition (EMT) of lens epithelial cells that remain associated with the lens capsule. These changes cause a loss of vision. The authors developed a chick embryo lens capsular bag model to study mechanisms involved in the onset of PCO. Because Src family kinases (SFKs) signal cell proliferation, migration, and EMT, the authors examined whether the inhibition of SFKs can prevent PCO. METHODS After mock cataract surgery, chick lens capsular bags were pinned to a culture dish and grown in the presence or absence of the SFK inhibitor PP1. Cell movement was followed by photomicroscopy. Progression of proliferation and EMT in the PCO cultures was determined by Western blot analysis and immunofluorescence staining. RESULTS As occurs in PCO, lens cells in this model proliferated, migrated across the posterior capsule, and expressed EMT markers, alpha-smooth muscle actin (alpha-SMA), and fibronectin (FN). Lens cells treated with PP1 maintained an epithelial phenotype, accumulated cadherin junctions, and did not migrate to the posterior capsule, increase proliferation, or express EMT markers. Therefore, exposure to PP1 prevented PCO. Short-term inhibition of SFKs was sufficient to prevent EMT, but longer inhibition was necessary to prevent lens cell migration. CONCLUSIONS Progression of PCO involved early activation of SFKs. Lens cell migration preceded EMT, and each of these two events required activation of an SFK signaling pathway. Suppression of SFK activation blocked PCO, suggesting SFKs as a therapeutic target for the prevention of PCO.