Objective: Vascular smooth muscle cells (VSMCs) undergo the phenotypic changes from contractile to synthetic state during
vascular remodeling after
ischemia.
SIRT1 protects against stress-induced
vascular remodeling via maintaining VSMC differentiated phenotype. However, the effect of smooth muscle
SIRT1 on the functions of endothelial cells (ECs) has not been well clarified. Here, we explored the role of smooth muscle
SIRT1 in endothelial angiogenesis after
ischemia and the underlying mechanisms. Methods: We performed a femoral artery
ligation model using VSMC specific human
SIRT1 transgenic (SIRT1-Tg) and knockout (KO) mice. Angiogenesis was assessed in in vivo by quantification of the total number of capillaries, wound healing and
matrigel plug assays, and in vitro ECs by tube formation, proliferation and migration assays. The interaction of HIF1α with
circRNA was examined by using
RNA immunoprecipitation,
RNA pull-down and in situ hybridization assays. Results: The blood flow recovery was significantly attenuated in SIRT1-Tg mice, and markedly improved in SIRT1-Tg mice treated with
SIRT1 inhibitor EX527 and in SIRT1-KO mice. The density of capillaries significantly decreased in the ischemic gastrocnemius of SIRT1-Tg mice compared with SIRT1-KO and WT mice, with reduced expression of VEGFA, which resulted in decreased number of arterioles. We identified that the phenotypic switching of SIRT1-Tg VSMCs was attenuated in response to
hypoxia, with high levels of
contractile proteins and reduced expression of the synthetic markers and NG2, compared with SIRT1-KO and WT VSMCs. Mechanistically, SIRT1-Tg VSMCs inhibited endothelial angiogenic activity induced by
hypoxia via the exosome cZFP609. The cZFP609 was delivered into ECs, and detained HIF1α in the cytoplasm via its interaction with HIF1α, thereby inhibiting VEGFA expression and endothelial angiogenic functions. Meantime, the high cZFP609 expression was observed in the plasma of the patients with atherosclerotic or diabetic lower extremity
peripheral artery disease, associated with reduced ankle-brachial index. Knockdown of cZFP609 improved blood flow recovery after hindlimb
ischemia in SIRT1-Tg mice. Conclusions: Our findings demonstrate that
SIRT1 may impair the plasticity of VSMCs. cZFP609 mediates VSMCs to reprogram endothelial functions, and serves as a valuable
indicator to assess the prognosis and clinical outcomes of ischemic diseases.