Effect of siRNA targeting SHP-1 on angiogenesis in hindlimb ischemia

血管内皮生长因子（Vascular endothelial growth factor，VEGF）通过与血管内皮生长因子受体2（VEGF receptor-2，KDR/flk-1）相互作用促进血管内皮细胞的生长和新生血管的形成。VEGF与KDR/flk-1的结合诱导受体的构象变化，随后是酪氨酸残基的二聚化和自磷酸化。磷酸化的KDR/flk-1可以是细胞内蛋白酪氨酸磷酸酶的底物。SHP-1是一种胞质蛋白酪氨酸磷酸酶，在其N-末端半部分含有两个Src同源2结构域，与活化的细胞因子、生长因子和抗原受体相互作用，并通过其结合的受体或受体底物的去磷酸化在信号转导途径中起负调节作用。因此，设计用于抑制SHP-1表达的治疗性血管生成在后肢缺血中将是有益的。在这里，我们报告，siRNA靶向SHP-1激活KDR/flk-1和加速血管生成在大鼠模型后肢缺血。注射到缺血性闭肌后，基于载体的siRNA减少了SHP-1，增加了KDR/flk-1的磷酸化，并显著增加了毛细血管密度。我们的数据表明，在体内的潜在用途的siRNA靶向SHP-1作为外周缺血性疾病的治疗。

Vascular endothelial growth factor (VEGF) promotes the growth of vascular endothelial cells and the development of new blood vessels through interaction with VEGF receptor-2 (KDR/flk-1). The binding of VEGF to KDR/flk-1 induces conformational changes in the receptor, followed by dimerization and autophosphorylation of the tyrosine residues. The phosphorylated KDR/flk-1 can be a substrate for intracellular protein tyrosine phosphatases. SHP-1 , a cytoplasmic protein tyrosine phosphatase that contain two Src homology 2 domains in its N-terminal half, interacts with activated cytokine, growth factor, and antigen receptors and plays a negative regulatory role in signal transduction pathways by dephosphorylation of the receptors or receptor substrates to which it binds. Thus, therapeutic angiogenesis designed to inhibit expression of SHP-1 would be beneficial in hindlimb ischemia. Here we report that siRNA targeting SHP-1 activates KDR/flk-1 and accelerates angiogenesis in a rat model of hindlimb ischemia. Upon injection to the ischemic adductor muscle, vector-based siRNA reduced SHP-1, increased phosphorylation of KDR/flk-1, and markedly increased capillary density. Our data demonstrate in vivo the potential use of siRNA targeting SHP-1 as therapy for peripheral ischemic diseases.