AbstractThe posttranscriptional regulation of miRNAs is important for organism development. To investigate the role of miRNAs in angiogenesis, we performed a loss‐of‐function screening assay in human umbilical vein endothelial cells (HUVECs) and found that knockdown of 7 miRNAs (miR‐95a, miR‐126, miR‐129, miR‐137, miR‐139, miR‐200a, and miR‐335) significantly suppressed cell viability. As miR‐200a was highly expressed in HUVECs, blocking endogenous miR‐200a using 2′‐OMe antisense oligonucleotide (ASOs) resulted in a decrease of cell viability and migration. Bioinformatics analysis indicates the 3′ untranslated region (UTR) of thrombospondin‐1 (THBS1) has a putative binding site for miR‐200a. MiR‐200a can directly bind to THBS1 3′UTR and negatively regulate THBS1 expression. The identification of endothelial cells (ECs) related miRNA and its target gene may gain new insight into the mechanism of angiogenesis. © 2011 IUBMB IUBMB Life, 63(7): 553‐559, 2011