Lens capsule and secondary cataract

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PROJECT SUMMARY Posterior capsular opacification (PCO) is a major vision-impairment problem that emerges after cataract surgery and Nd:YAG laser posterior capsulotomy is required to restore vision. During PCO, the lens epithelial cells (LECs) that remain tethered to the anterior capsule after cataract surgery proliferate, migrate to the posterior capsule where they undergo epithelial-to-mesenchymal transition (EMT) and secrete extracellular matrix, leading to fibrous tissue formation along with wrinkling of the posterior capsule. Transforming growth factor-2 (TGFβ2) has been proposed as a major driver of EMT. We have previously demonstrated that the advanced glycation end products (AGEs) present in aged lens capsules promote the TGFβ2-mediated EMT of LECs. In our preliminary studies for this proposal, we have discovered that capsule-AGEs through binding to RAGE receptor promote senescence of LECs. We have also observed that senescent LECs promote EMT of nonsenescent LECs through paracrine mechanisms. Our data also suggest a greater synthesis of TGFβ2 in senescent cells than nonsenscent cells. Based on these observations, we propose a novel hypothesis that capsule AGEs induce senescence in LECs, which promotes the EMT of LECs during posterior capsule opacification. This hypothesis is further supported by our recent observation of senescent cells in the posterior capsules of psuedophakic human donor eyes. In Aim 1, we will test the hypothesis that lens capsule AGEs induce senescence of LECs through formation of reactive oxygen species in cells cultured on AGE- modified extracellular matrix. In Aim 2, we will test the hypothesis that senescent cells promote the EMT of human LECs through paracrine mechanisms. The secretion of TGFβ2 and IL-6 from senescent cells and their ability to induce EMT in nonsenescent cells will be investigated. In Aim 3, we will test the hypothesis that inhibition/downregulation of RAGE prevents LEC senescence and PCO-like changes in human capsular bags. Together, the proposed studies are expected to expand our understanding of the molecular mechanisms of lens fibrosis and aid in the development of novel drugs for treating PCO.