DPP-4 Inhibitors Attenuate Fibrosis After Glaucoma Filtering Surgery by Suppressing the TGF-β/Smad Signaling Pathway

PURPOSE: This study investigated the effect of dipeptidyl peptidase-4 inhibitors (DPP-4is) on fibrosis after glaucoma filtering surgery with clinical data and an in vitro model that used transforming growth factor-β (TGF-β) to induce human Tenon's fibroblast (HTF) fibrosis. METHODS: The medical records of 41 eyes of 35 patients with diabetes with neovascular glaucoma (NVG) who received initial trabeculectomy were retrospectively reviewed. The surgical success rate was compared between cases that received (n = 23) and did not receive (n = 18) DPP-4i treatment for diabetes. The antifibrotic effects of linagliptin (a DPP-4i) were evaluated with quantitative real-time PCR for fibrosis markers (α-smooth muscle actin, collagen Iα, and fibronectin), a scratch assay, and a collagen gel contraction assay of primary cultured HTFs treated with TGF-β1 and linagliptin. Western blotting analysis was performed to evaluate the levels of phosphorylated Smad2 and Smad3 in the presence of linagliptin. RESULTS: The Kaplan-Meier curve for bleb survival was higher in patients who received DPP-4is (P = 0.017, log-rank test). The in vitro experiments demonstrated that treatment with linagliptin attenuated the elevated levels of fibrosis markers induced by TGF-β1 in HTFs. Linagliptin treatment also prevented the migration and gel contraction of HTFs. Linagliptin inhibited the phosphorylation of Smad2 and Smad3, which is the canonical pathway of TGF-β signaling. CONCLUSIONS: The current study indicates the potential effect of DPP-4is for maintaining bleb function after glaucoma filtering surgery in patients with diabetes with NVG. Our results demonstrate that linagliptin attenuates fibrotic change in HTFs by inhibiting TGF-β/Smad signaling.