The present invention relates to a method of preparing vascular endothelial cells by transforming (transdifferentiating) adult fibroblasts and a composition, which includes vascular endothelial cells prepared according to the method, for preventing and treating ischemic diseases, the method including a step of transducing adult fibroblasts with a gene. In particular, the present invention confirms that five factors, Foxo1, Er71, Klf2, Tal1, and Lmo2, induce transdifferentiation of adult fibroblasts into induced vascular endothelial cells. Furthermore, the present invention confirms that three factors, Er71, Klf2, and Tal1 induce transdifferentiation of human adult fibroblasts into induced vascular endothelial cells. The resultant induced endothelial cells enable lower limb salvaging by angiogenesis in lower limb ischemic animal models, showing that the induced endothelial cells can be effectively used for prevention or treatment of ischemic diseases.
