In vivo evidence of angiogenesis induced by transcription factor ets-1 - Ets-1 is located upstream of angiogenesis cascade

Background - A transcription factor, ets-1, regulates the transcription of metalloproteinase genes, the activity of which is necessary for matrix degradation and the migration of endothelial cells. However, no study has demonstrated that ets-1 itself has an angiogenic action in vivo. Thus, we examined ( 1) the effects of overexpression of the ets-1 gene on angiogenesis in a rat hindlimb ischemia model, and ( 2) how ets-1 induced angiogenesis. Methods and Results - In this study, we used the HVJ-liposome method, which is highly effective for transfection, to transfect the human ets-1 gene. At 4 weeks after transfection, the capillary density and blood flow were significantly increased in a hindlimb transfected with the human ets-1 gene compared with control. These data clearly demonstrated that ets-1 has the ability to stimulate angiogenesis in vivo. To elucidate the molecular mechanisms by which ets-1 induced angiogenesis, we focused especially on the expression of hepatocyte growth factor (HGF) and vascular endothelial growth factor ( VEGF), potent angiogenic growth factors, because the promoter regions of both genes contain ets binding sites. Interestingly, overexpression of ets-1 upregulated both tissue HGF and VEGF concentrations in rat hindlimb. More importantly, administration of neutralizing antibody against HGF and VEGF attenuated the increase in blood flow and BrdU-positive cells induced by ets-1. Upregulation of HGF and VEGF by ets-1 was also confirmed by in vitro experiments using human vascular smooth muscle cells. Conclusions - The present study demonstrated that ets-1 regulated angiogenesis through the induction of angiogenic growth factors ( VEGF and HGF). Overexpression of ets may provide a new therapeutic strategy to treat peripheral arterial disease.