Abstract 10980: Sirt7 Regulates Endothelial Cell Functions and Promotes Angiogenic Response in Mice Model of Hindlimb Ischemia
Introduction: Sirt7, one of the members of mammalian sirtuin, plays a key role in oncogenic transformation. Little is known about the functional role of Sirt7 in angiogenic responses. Hypothesis: Sirt7 regulates endothelial cell functions and blood vessel growth.
Methods: Sirt7 deficient (Sirt7-/-) and wild-type (WT) mice were subjected to unilateral femoral artery ligation to induce hindlimb ischemia. We performed bone marrow (BM) transplantation using either WT or Sirt7 -/- mouse as donors. In vitro loss- and gain-of-function experiments were performed with human umbilical vein endothelial cells (HUVECs).
Results: Blood flow recovery of hindlimb following ischemic surgery was significantly impaired in Sirt7-/- mice compared with WT mice. Immunostaining of ischemic muscle showed a significant decrease in capillary density in Sirt7-/- mice compared with WT mice at 7 days after surgery. There was a significant decrease in angiogenesis-related transcript expression including VEGF, FGF2, PDGF-B in adductor muscle tissue in sirt7-/- compared with WT mice. Neutrophils and macrophages infiltration into ischemic site were decreased in Sirt7-/- mice compared with WT mice at 24 hours after surgery. Consistent with these results, gene expression of inflammation-related genes, such as interleukin-1β, interleukin-6, TNF-α, and MCP-1 were significantly lower in Sirt7-/- than in WT mice. There was no difference in blood flow recovery following ischemic surgery between WT mice transplanted with WT or Sirt7-/- BM cells, suggesting that Sirt7 deficiency in BM cells have little effect on blood flow recovery in response to hindlimb ischemia. In vitro, Sirt7 expression was detectable in total RNA isolated from HUVECs. Knockdown of endogenous Sirt7 by small interfering RNA (siRNA) significantly attenuated hypoxia-induced tube formation and migration. VEGF-induced cell proliferation was completely abolished by Sirt7 knockdown. Conversely, adenovirus-mediated Sirt7 overexpression augmented tube formation and VEGF-induced proliferation.
Conclusions: Sirt7 promotes angiogenic response by modulating endothelial cell functions and angiogenic growth factors expression. Sirt7 plays a pivotal role in ischemia-induced angiogenic response in mice.
- © 2012 by American Heart Association, Inc.