Abstract 15882: Ablation of E2F3 in Endothelial Cells Impairs the Functional Recovery of Heart and Limb from Ischemic Injury
E2F family of transcription factors plays a central role in cell cycle control. However, our recent findings suggest that in endothelial cells (ECs), different E2F members have rather diverse functions: E2F1 suppresses angiogenesis while E2F2 regulates vascular contractility and blood-pressure homeostasis. To comprehensively investigate the function of E2F3 in ECs, we have generated two strains of endothelial specific E2F3-knockout mice, Tie2-Cre;E2F3fl/fl and VE-cad-Cre;E2F3fl/fl mice (E2F3 KO), and their respective littermate controls, Tie2-Cre;E2F3+/+ and VE-cad-Cre;E2F3+/+ mice (WT). Hind limb ischemia (HLI) was induced in Tie2-Cre;E2F3fl/fl and Tie2-Cre;E2F3+/+ mice by surgical excision of the left femoral artery. The E2F3 KO but not WT mice exhibited necrosis in the limbs and toes (66.7% and 88.9%, respectively; n=18) at d7 post-HLI. Laser Doppler perfusion imaging revealed an impaired blood-flow recovery in E2F3 KO group (p<0.01 at d7 and d14; n=18 for WT, n=6 for KO). Immunohistological analyses revealed a significantly lower capillary density (Lectin perfusion and staining, p<0.01 at d7 and d14) and EC proliferation rate (BrdU/Lectin staining, P<0.001 at d7 and d14) in the ischemic limb of E2F3 KO mice than in WT controls. Myocardial infarction (MI) was induced by ligation of the LAD coronary artery in VE-cad-Cre;E2F3fl/fl and VE-cad-Cre;E2F3+/+ mice. Echocardiography revealed a significantly lower left ventricular (LV) ejection fraction in E2F3 KO than in WT controls (P<0.01 at d7, d14, and d28; n=10). At day 28, immunohistological analyses indicated that peri-infarct capillary density (P<0.01) and infarct wall thickness (P<0.01) in the LV were significantly lower, and infarct size (P<0.01) was significantly larger, in hearts of E2F3 KO mice than in WT mice. In vitro, the Adenoviral vector-Cre infected E2F3fl/fl cardiac ECs expressed significantly lower levels of cyclin A2, B-Myb, DHFR, cdc2, and cdc6 genes (qRT-PCR) and exhibited lower rates of DNA synthesis (EdU assay) and cell proliferation (cell number count) than ECs isolated from E2F1 KO, E2F2 KO, and WT mice. These results suggest that among all E2F members, E2F3 is essential for EC growth, angiogenesis, and preservation of cardiac and limb tissues from ischemic injury.
- © 2011 by American Heart Association, Inc.