Abstract 3829: Endothelial Cell Response to Hypoxia is Modulated by Microrna-210 Direct Targeting of Ephrin-A3
MicroRNAs (miRNAs) are small non-protein-coding RNAs that negatively modulate gene expression. In this study, miRNAs role in endothelial cell response to hypoxia was investigated. It was found that the expression of miR-210 progressively increased upon exposure to hypoxia. Interestingly, HIF1-alpha was necessary and sufficient for miR-210 induction, while HIF2-alpha was not necessary. miR-210 over-expression in normoxic endothelial cells increased the formation of capillary-like structures on Matrigel and VEGF-induced cell migration. Conversely, miR-210 blockade via LNA-anti-miRNA transfection decreased the formation of capillary-like structures stimulated by hypoxia and inhibited cell migration in response to VEGF. miR-210 over-expression did not affect endothelial cell growth in both hypoxia and normoxia. However, anti-miR-210 transfection inhibited cell growth and induced apoptosis, both in normoxia and in hypoxia. We found that one relevant target of miR-210 in hypoxia was Ephrin-A3, since miR-210 was necessary and sufficient to down-regulate its expression. Moreover, luciferase reporter assays showed that Ephrin-A3 was a direct target of miR-210. Ephrin-A3 modulation by miR-210 had significant functional consequences: indeed, the expression of an Ephrin-A3 allele that is not targeted by miR-210, prevented miR-210-mediated stimulation of both tubulogenesis and chemotaxis. A combination of proteomic and transcriptomic approaches has been undertaken, identifying potential direct and indirect targets of miR-210 action. We conclude that miR-210 induction is a crucial element of endothelial cell response to hypoxia, affecting cell survival, migration and differentiation.