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Jade Lasiste, Denise Miyamoto, Pablo Zoroquiain, Sabrina Bergeron, Miguel N Burnier, Christina Mastromonaco; Metformin inhibits epithelial-to-mesenchymal transition in an in vitro model of posterior capsule opacification. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3186.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior capsule opacification (PCO) is the most common complication after cataract surgery, affecting up to 50% of patients 2-5 years post-operatively. Epithelial-to-mesenchymal transition (EMT) is the main pathophysiology underlying PCO. Metformin, a drug with an excellent safety profile used primarily for diabetes, has been shown to suppress EMT. The objective of this study was to test the effectiveness of metformin in inhibiting EMT in an in vitro model of PCO.
The human lens epithelial cell (LEC) line HLE-B3 was exposed to transforming growth factor-beta (TGF-β) and fibroblast growth factor (FGF) to induce EMT. Subsequently, the effect of metformin on the following cellular parameters were determined: (1) survival, using a viability assay and drug concentrations from 0-100 mM; (2) expression of epithelial (pax6, E-cadherin) and mesenchymal (α-smooth muscle actin or α-SMA, fibronectin) markers via Western blot; (3) morphology, via microscopy and image analysis; (4) and migration, using the wound assay. The presence of OCT1, the receptor for metformin uptake, and the ratio of active to inactive protein kinase B (pAkt/Akt), were assessed via Western blot. OCT1 expression was confirmed with immunohistochemistry on donor eyes. Statistical analysis of variance with Tukey post-hoc test was done for analysis of cytotoxicity, morphology and migration data.
Metformin is lethal to half (LC50) and all (LC100) cells at 30 and 80 mM, respectively. A decrease in viability (P<0.05) was noted at 5 mM. Compared to controls, EMT-induced LECs treated with 1 mM metformin showed increased pax6 and E-cadherin and decreased α-SMA and fibronectin expression. LECs treated with metformin also maintained roundness and circularity consistent with their epithelial phenotype. In addition, migration was significantly inhibited with 0.5 mM metformin (P<0.05). HLE-B3 and LECs from donor eyes expressed OCT1, and treated cells showed a decreased pAkt/Akt ratio.
Metformin inhibits EMT in LECs, decreasing survival and migration and maintaining epithelial phenotype. Findings suggest that metformin entry into the cell is through the OCT1 receptor, its action mediated via decreased Akt activation. Metformin thus has potential as an adjunct to treatment. Toxicity to proximal eye tissues and effectiveness in vivo must be tested to determine dose, route and timing of administration.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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