Injury-Mediated Vascular Regeneration Requires Endothelial ER71/ETV2

Abstract

Objective Comprehensive understanding of the mechanisms regulating angiogenesis might provide new strategies for angiogenic therapies for treating diverse physiologic and pathologic ischemic conditions. The ETS factor ETV2 (aka ER71) is essential for the formation of hematopoietic and vascular systems. Despite its indispensable function in vessel development, ETV2 role in adult angiogenesis has not yet been addressed. We have therefore investigated the role of ETV2 in vascular regeneration. Approach and Results We utilized endothelial Etv2 conditional knockout (CKO) mice and ischemic injury models to assess the role of ETV2 in vascular regeneration. While Etv2 expression was not detectable under steady state conditions, its expression was readily observed in endothelial cells following injury. Mice lacking endothelial Etv2 displayed impaired neovascularization in response to eye injury, wounding, or hindlimb ischemic injury. Lentiviral Etv2 expression in ischemic hindlimbs led to improved recovery of blood flow with enhanced vessel formation. Following injury, Flk1 expression and neovascularization were significantly upregulated by Etv2, while Flk1 expression and VEGF response were significantly blunted in Etv2 deficient endothelial cells. Conversely, enforced Etv2 expression enhanced VEGF mediated endothelial sprouting from embryoid bodies. Lentiviral Flk1 expression rescued angiogenesis defects in endothelial Etv2 CKO mice following hindlimb ischemic injury. Furthermore, Etv2+/−; Flk1+/− double heterozygous mice displayed a more severe hindlimb ischemic injury response compared to Etv2+/− or Flk1+/− heterozygous mice, revealing an epistatic interaction between ETV2 and FLK1 in vascular regeneration. Conclusion Our study demonstrates a novel obligatory role for the ETV2 in postnatal vascular repair and regeneration.

Reprogrammed Human Endothelial Cells

“…10 ETV2 is a member of ETS transcription factor family which is transiently expressed during embryonic development and is absent in adult ECs. 14, 15 Recent studies reported that ETV2 directly reprograms mature amniotic cells into functional ECs avoiding the poor proliferation and lineage instability associated with pluripotent stem cell derived EC. 9, 11 However, the strategy for generating amniotic cell-derived ECs is very complex and requires long-term culture which is not applicable for even sub-acute vascular injury, is impractical and costly and could require immunosuppression given the allogeneic cell source.…”

Recent Advances in the Genetics of Atherothrombotic Disease and Its Determinants

“…100 Conditional knockout of the E-twenty six factor Ets variant 2 in endothelial cells resulted in impaired neovascularization in response to ischemic tissue injury. 101 Mice lacking neuropilin-1 in cardiomyocytes and vascular smooth muscle cells exhibited decreased survival, because of development of cardiomyopathy and aggravated ischemia-induced heart failure. 102 Finally, in a transgenic mouse expressing a peroxisome proliferator-activated receptor-γ mutant (E-V290M) selectively in endothelium, the time to occlusive thrombosis of the carotid artery was significantly shortened after either chemical or photochemical injury.…”

ETS transcription factors in embryonic vascular development

“…While zebrafish etv2 is highly expressed during early vasculogenesis stages, its expression is downregulated shortly after the initiation of circulation [22]. Interestingly, Etv2 expression is induced following injury in the mouse ischemic injury model and is required for vascular regeneration [23]. …”

“…3). More recently, it was shown that murine Etv2 expression was readily observed in endothelial cells after ischemic injury and that neovascularization after injury occurred via Etv2-dependent induction of Flk1, thus identifying an epistatic interaction between Etv2 and Flk1 in vascular regeneration [23]. …”