['We aimed to investigate the anti-angiogenic properties of miR-155 via in vitro and in vivo studies.', 'miR-155 was knocked down using lentivirus-mediated RNA interference. The proliferation, migration, and tube formation of human retinal microvascular endothelial cells (HRMECs) were measured using BrdU, Transwell, and Matrigel assays, respectively. An oxygen-induced retinopathy (OIR) model was induced using neonatal C57BL/6J pups. Anti-miR-155 was intravitreally injected on postnatal day 12, and the retinal non-perfused areas and extent of neovascularization were measured on postnatal day 18 using transcardiovascular fluorescein isothiocyanate (FITC)-dextran perfusion and retina sections. A laser-induced choroidal neovascularization (CNV) model was induced in adult C57BL/6J mice. To evaluate the leakage areas, fundus fluorescein angiography was performed on day 14 after anti-miR-155 intravitreal injection. The neovascularization area of the CNV model was also examined in confocal and retina section studies. The expression levels of SHIP1 and p-Akt (Thr308, Ser473, and Thr450) were evaluated both in vitro and in vivo.', 'The expression of miR-155 was elevated in HRMECs after treatment with vascular endothelial growth factor (VEGF) and in neovascularized mouse model retinas. Anti-miR-155 lentivirus reduced the VEGF-induced proliferation, migration, and tube formation abilities of HRMECs. Anti-miR-155 attenuated retinal neovascularization in in vivo CNV and OIR models. In VEGF-treated HRMECs and retina neovascularization models, p-Akt (Ser473) was significantly upregulated, while SHIP1 was downregulated. Conversely, the inhibition of miR-155 restored the expression of SHIP1 and reduced the phosphorylation of effectors in the Akt (Ser473) signaling pathway.'] Does down-regulation of microRNA-155 attenuate retinal neovascularization via the PI3K/Akt pathway?