RAGE Is Essential for Subretinal Fibrosis in Laser-Induced Choroidal Neovascularization: Therapeutic Implications

Subretinal fibrosis, a complication of neovascular age-related macular degeneration (nAMD), involves the epithelial-mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells as a contributing mechanism. The receptor for advanced glycation end products (RAGE) is a multiligand receptor implicated in fibrotic diseases, but its role in subretinal fibrosis has not been studied. This study investigated the role of RAGE in subretinal fibrosis.

Subretinal fibrosis was induced in male RAGE-/- and wild-type (WT) mice via laser photocoagulation, and fibrosis lesion volume was assessed on day 35 using optical coherence tomography and immunostaining. In vitro, EMT was induced in primary human RPE cells with transforming growth factor-beta 2 (TGF-β2). The role of RAGE in EMT was studied in cells pretreated with RAGE antagonists (FPS-ZM1 or azeliragon), followed by cotreatment with TGF-β2 for 48 hours. Signaling studies were conducted by pretreatment with FPS-ZM1 for 2 hours, cotreatment with TGF-β2 for 60 minutes, and subsequent immunoblot analysis.

In RAGE-/- mice, subretinal fibrosis after laser-induced choroidal neovascularization was significantly reduced, with a smaller fibrosis volume, less inflammation, decreased activation of pSmad2, and reduced deposition of fibrotic markers (αSMA, collagen I) compared to WT mice. In vitro treatment with TGF-β2 in human RPE cells increased mitochondrial reactive oxygen species and upregulated EMT markers (αSMA, collagen I, and fibronectin), which were inhibited by cotreatment with FPS-ZM1 or azeliragon. FPS-ZM1 blocked TGF-β2-induced Smad2-dependent signaling and EMT without affecting the extracellular signal-regulated kinase (ERK) pathway.

Our findings indicate that RAGE plays a role in RPE cell EMT in subretinal fibrosis and that RAGE antagonists attenuate this process, making RAGE a promising therapeutic target for subretinal fibrosis in nAMD.