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Naoki Okumura, Keisuke Hashimoto, Hirokazu Okuda, Emi Ueda, Theofilos Tourtas, Ursula Schlotzer-Schrehardt, Friedrich E Kruse, Noriko Koizumi; Feasibility of TGF-β inhibition for the treatment of Fuchs endothelial corneal dystrophy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1434. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Endoplasmic reticulum (ER) stress is thought to be involved in the pathophysiology of Fuchs endothelial corneal dystrophy (FECD). We reported that the corneal endothelium in FECD is hyper responsive to TGF-β, resulting in excessive extracellular matrix (ECM) production. In this study, we investigated whether TGF-β signaling causes ER stress and evaluated the feasibility of TGF-β signaling as a therapeutic target of FECD.
Descemet’s membrane including corneal endothelial cells (CEC) were obtained from 30 patients during Descemet’s membrane endothelial keratoplasty (DMEK), and from 30 donor corneas as a control. TGF-β1, TGF-β2, TGFβR1, and TGFβR2 expression was evaluated by RT-PCR. As cellular models, CEC were isolated from 3 FECD-patient corneas and 3 donor corneas, then cultured and immortalized (henceforth: iFECD and iHCEC). ECM proteins fibronectin and collagen type 1, ER stress sensors ATF6, IRE1, and PERK, and apoptosis related proteins CHOP, caspase3, and PARP were examined by western blotting. Unfolded protein was evaluated by aggresome staining. SB431542, TGFβR1 siRNA, and Smad3 inhibitor was used to evaluate the effect of inhibiting TGF-β signaling on ER-stress-mediated apoptosis. Mitochondrial membrane potential was evaluated by flow cytometry.
RT-PCR demonstrated that TGF-β1, TGF-β2, TGFβR1, and TGFβR2 expression was significantly higher in FECD-patient corneal endothelium than in controls (p<0.01). In cell models, TGF-β2 induced production of ECM proteins and activation of PERK and CHOP at a higher level in iFECD than in iHCEC. In iFECD, SB431542, TGFβR1 siRNA, and Smad3 inhibitor suppressed expression of fibronectin and formation of unfolded protein. ATF6, IRE1, and PERK were activated in iFECD, but SB431542 downregulated activation of those sensor proteins. Flow cytometry showed that SB431542 significantly suppressed the percentage of mitochondrial membrane demoralized cells (p<0.01). Consistently, cleavage of caspase 3 (apoptosis executor molecule) and PARP was suppressed by SB431542.
The expression level of TGF-β isoforms and TGF-β receptors is high in FECD-patient corneal endothelium, which maybe induces high responsiveness to TGF-β and leads to ER stress. Inhibition of TGF-β signaling might be a therapeutic target by suppressing ER-stress-mediated cell death as well as accumulation of ECM of FECD.
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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