Retinal vascular diseases are characterized by pathologic neovascularization, Previous research found that conditional knockout of Twist1 in endothelial cells significantly decreased neovascularization in mouse model of oxygen induced retinopathy (OIR). TWIST1 was also found directly regulated by HIF-1 in promoting tumor angiogenesis. Therefore, we hypothesize that TWIST1 might play an important role in retinal neovascularization. In this study, we plan to investigate the role of TWIST1 in regulating of angiogenesis of human retinal vessel endothelial cells . Our results hopefully benefit our understanding of the mechanism of retinal neovascularization, which has a profound theoretical and clinical significance for retinal vascular diseases.