The annexin A2 system promotes retinal neoangiogenesis in OIR by enhancing fibrin clearance. (A) Representative cross-sections (magnification ×40) of retinas, from P17 oxygen-treated Anxa2^+/+ and Anxa2^−/− mice, stained with DAPI (blue), isolectin B4 (green), and anti-fibrinogen (red). Close-up views of the peripheral retina are also shown (magnification ×200). Fibrin deposition is indicated by arrowheads. (B) Representative immunoblot of fibrin within retinal tissue from P17 oxygen-treated Anxa2^+/+ and Anxa2^−/− mice. (C) Representative cross-sections (magnification ×40) of retinas from P17 oxygen-treated Anxa2^−/− mice injected with either empty (V) or A2-encoding (A2) virus, stained with DAPI (blue), isolectin B4 (green), and anti-fibrinogen (red). Close-up views of the peripheral retina are also shown (magnification ×200). Fibrin deposition is indicated by arrowheads. (D) Representative immunoblot of fibrin within retinal tissue from P17 oxygen-treated Anxa2^−/− mice injected with empty or A2-encoding virus. S indicates sclera; V, vitreous body. Scale bars, 500 μm (A; magnification ×40) and 100 μm (C; magnification ×200). The data are representative of 5 (A,C) and 3 (B,D) independent experiments.