Metformin inhibits subretinal fibrosis by activating Klotho by miR-126-5p

Subretinal fibrosis is a main cause of visual loss in patients with neovascular age-related macular degeneration (nAMD), for whom there has been a lack of effective medication. Metformin can improve inflammation and angiogenesis in eye diseases. This study aimed to investigate the mechanism by which metformin inhibits subretinal fibrosis. A subretinal fibrosis cell model was induced by treating human retinal pigment epithelial cells (ARPE-19) with TGF-β1, a subretinal fibrosis mouse model was induced by a laser, and both cells and mice were treated with metformin. Cell proliferation, migration, and invasion were detected by CCK-8, scratch, and Transwell assays. Western blotting and immunofluorescence were used to evaluate protein expression levels, and RT‒qPCR was used to detect gene expression levels. HE and Masson staining were used to observe the morphological changes in retinal and choroidal tissues. Metformin treatment inhibited the TGF-β1-induced proliferation, migration, invasion and epithelial‒mesenchymal transition (EMT) of ARPE-19 cells and effectively ameliorated laser-induced subretinal fibrosis in mice. Mechanistically, metformin inhibits the expression of miR-126-5p, promotes Klotho synthesis, slows the progression of subretinal fibrosis, and miR-126-5p targets and negatively regulates Klotho. Metformin activates Klotho by inhibiting miR-126-5p, thereby reversing TGF-β1-induced ARPE-19 cell EMT and improving laser-induced subretinal fibrosis in mice.