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Scott A Bowman, Suresh Regmi, Tannin A Schmidt, Judith A West-Mays; Effect of Proteoglycan 4 treatment on focal adhesions of lens epithelial cells during TGFβ-induced EMT. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2019. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
After the surgical removal of the lens during cataract surgery, residual lens epithelial cells (LEC) that remain adhered to the capsule undergo epithelial-to-mesenchymal transition (EMT) into myofibroblasts, which can lead to the formation of posterior capsule opacification (PCO). Proteoglycan 4 (PRG4), also known as lubricin, is a lubricant found in synovial fluid and has also been detected at the ocular surface. Previously, we have shown that lens epithelial cells treated with recombinant human PRG4 (rhPRG4) remain adhered to their native capsule and rhPRG4 co-treatment decreases αSMA expression in LEC activated with TGFβ2. The current study continues to investigate the effect of PRG4 on TGFβ-induced EMT of LEC.
Rat lens epithelial cells from 20-day old Wistar rat pups were explanted on their endogenous capsule and maintained in culture using Medium 199. Confluent explants were co-treated with recombinant human PRG4 and recombinant human TGFβ2. Western blotting and immunostaining were used to observe expression of EMT and cell adhesion markers.
Rat LEC explants treated with TGFβ expressed αSMA and showed increased phosphorylation of FAK, localized into focal adhesions. In comparison, explants co-treated with TGFβ and rhPRG4 showed a decrease in αSMA expression and F-actin polymerization into stress fibers. Also, both FAK phosphorylation and the localization of FAK into focal adhesions were decreased in rhPRG4/TGFβ co-treated LEC explants.
Our findings suggest that rhPRG4 prevents TGFβ-induced αSMA formation and stress fiber formation. The rhPRG4 co-treatments also mitigated phosphorylation of FAK and formation of focal adhesions. These findings suggest PRG4 may affect the contact between the LEC and the lens capsule in TGFβ-treated cells, preventing the full myofibroblast phenotype. Future studies will focus on the mechanism of focal adhesion disruption, and the potential of PRG4 as a therapy for PCO.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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