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AFTAB TAIYAB, Julie Holms, Judith A West-Mays; β-catenin/Smad3 interaction regulates myofibroblast transition of lens epithelial cells. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1606.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior Capsular Opacification (PCO) or secondary cataract is a common postoperative complication following cataract surgery that results in blindness. Previous reports show that TGFβ-induced Epithelial to Mesenchymal (myofibroblast) Transition (EMT) is involved in PCO. However, the signaling events that regulate EMT during TGFβ-induced PCO are not fully understood. Here, we have examined the potential interaction between TGF-β-induced canonical (Smad3 pathway) and non-canonical (β-catenin;Rho/ROCK/MRTF) pathways in the EMT of LECs. We hypothesize that this interaction is crucial for the progression of EMT in the lens.
Wistar rats 17-19 days old were sacrificed by asphyxiation and their eyes were removed. Lens epithelial explants were prepared by dissecting out the posterior lens fiber cell mass, leaving the anterior epithelium intact on the capsule. Explants were cultured in serum free medium with or without TGFβ2, and TGFβ2 in combination with the β-catenin/CBP interaction inhibitor, ICG-001, or the Smad3 inhibitor, SIS3, for 48 hrs. Western blot and immunofluorescence analyses were carried out and the data was statistically analyzed using Graphpad Prism.
Western blot and Immunofluorescence analyses revealed a decrease in expression of the known EMT marker, α-SMA, along with an absence in stress fiber formation upon inhibition of TGFβ-induced Smad3 activation by SIS3. In addition, inhibition of Smad3 activation abrogated TGFβ-induced expression of fascin, an actin bundling protein that facilitates stress fiber formation. Interestingly, co-treatment of TGFβ –treated explants with ICG-001 resulted in decreased Smad3 activation. Further, inhibition of Smad3 activation suppressed nuclear translocation of myocardin-related transcription factor (MRTF), the major transcription factor that regulates cytoskeletal remodeling during EMT.
The decrease in α-SMA and fascin levels along with attenuation of stress-fiber formation upon inhibition of TGFβ-induced Smad3 activation indicates the importance of TGFβ/Smad3-mediated canonical signaling during transformation of LECs into myofibroblasts. The decrease in phosho-Smad3 upon inhibition of β-catenin/CBP interaction and absence of nuclear MRTF-A upon inhibition of Smad3 activation reveal novel interactions between TGFβ-mediated canonical and non-canonical signaling during EMT in the lens.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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