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Matthew L Hupy, Michelle G Pedler, Biehuoy Shieh, Dongyan Wang, Xiao-jing Wang, J. Mark Petrash; SMAD7 mediated suppression of epithelial to mesenchymal transition markers in lens. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5633.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior capsular opacification (PCO) is the most common complication of cataract surgery. PCO is a result of TGF-β-induced fibrosis in which residual cells undergo epithelial-to-mesenchymal transitions (EMT), yielding cells with a myofibroblastic morphology. Our prior tissue culture studies demonstrated that aldose reductase (AR) plays a noncatalytic role in TGF-β-signaling in LEC, and that LEC from AR transgenic mice (ARTG) demonstrate elevated levels of TGF-β-signaling through the Smad pathway leading to EMT. The inhibitory SMAD7 has been reported to suppress TGFβ-induced Smad signaling and EMT in non-ocular tissues. In this study, we investigated the efficacy of SMAD7 in suppressing EMT in lens using both cell culture and in vivo cataract surgery models.
An enhanced version of SMAD7 used in these studies was engineered to contain a Tat-peptide to facilitate cell penetration (confirmed by immunofluorescence) and was purified from E. coli host cultures. Primary lens epithelial cells from ARTG mice were examined by western blotting for EMT markers following treatment with TGF-β2 and our enhanced SMAD7. The ability of SMAD7 to influence EMT was also evaluated in an extracapsular lens extraction (ECLE) model performed in ARTG mice. Five days after ECLE, RNA from lens capsules was used in QRT-PCR assays to measure transcript levels of EMT markers such as α smooth muscle actin (αSMA) and fibronectin (FN).
Exposure to TGF-β2 led to a 40% increase in αSMA in LEC cultured from ARTG mice. Addition of SMAD7 completely prevented the TGF-β2-induced increase in αSMA. Levels of gene transcripts for the EMT markers αSMA and FN were elevated in ARTG lens capsules following ECLE, but were decreased by 41% and 26%, respectively, when SMAD7 was introduced into the capsular bag at the time of lens extraction surgery.
SMAD7 reduces EMT markers as shown by TGF-β2 induction of αSMA in cultured LECs. SMAD7 reduces the induction of EMT markers αSMA and FN following ECLE surgery in mice. We hypothesize that suppression of the Smad pathway through the use of an enhanced version of SMAD7 is a potential strategy for reducing the onset and progression of PCO following cataract surgery.
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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