Heidenreich Regina, Murayama Toshinori, Silver Marcy, Essl Christine, Asahara Takayuki, Rocken Martin, Breier Georg
Department of Dermatology, Eberhard Karls University, Tuebingen, Germany.
J Vasc Res. 2008;45(5):437-44. doi: 10.1159/000126106. Epub 2008 Apr 16.
The vascular endothelial growth factor/vascular endothelial growth factor receptor 2 (VEGF/VEGFR-2) signal transduction system plays a key role during embryonic vascular development and adult neovascularization. In contrast to many endothelial genes, VEGFR-2 is expressed at low levels in most adult vessels but is strongly upregulated during neovascularization, leading to a pro-angiogenic response. Here, we analyzed the activity of regulatory sequences of the murine Vegfr2 gene during neovessel formation in vivo under ischemic and inflammatory conditions. Hindlimb ischemia was induced in transgenic mice, expressing the LacZ reporter gene under the control of Vegfr2 promoter/enhancer elements. Most vessels in the ischemic muscle tissue showed strong endothelium-specific reporter gene expression, whereas nearly no LacZ-expressing capillaries were observed in untreated control tissue. Cutaneous punch wounds were created to induce angiogenesis under inflammatory conditions, leading to robust LacZ expression in the majority of the blood vessels in the wound tissue. Since the cornea is physiologically avascular, the functionality of these promoter/enhancer elements exclusively in newly formed vessels was confirmed using the cornea micropocket assay. Taken together, our results show that these Vegfr2 regulatory elements are active during adult neovessel formation in general. Therefore, these sequences may prove to be valuable targets for novel endothelium-specific anti-angiogenic as well as pro-angiogenic treatment strategies. They may especially allow directing therapeutic gene expression to sites of adult neovascularization. Moreover, the Vegfr2/LacZ reporter mice represent a powerful model to generally analyze the transcriptional control mechanisms involved in the induction of Vegfr2 expression during adult neovascularization.
血管内皮生长因子/血管内皮生长因子受体2(VEGF/VEGFR-2)信号转导系统在胚胎血管发育和成人血管新生过程中起关键作用。与许多内皮基因不同,VEGFR-2在大多数成人血管中低水平表达,但在血管新生过程中强烈上调,导致促血管生成反应。在此,我们分析了小鼠Vegfr2基因调控序列在体内缺血和炎症条件下新血管形成过程中的活性。在Vegfr2启动子/增强子元件控制下表达LacZ报告基因的转基因小鼠中诱导后肢缺血。缺血肌肉组织中的大多数血管显示出强烈的内皮特异性报告基因表达,而在未处理的对照组织中几乎未观察到表达LacZ的毛细血管。制造皮肤打孔伤口以在炎症条件下诱导血管生成,导致伤口组织中大多数血管中出现强烈的LacZ表达。由于角膜在生理上是无血管的,使用角膜微袋试验证实了这些启动子/增强子元件仅在新形成的血管中的功能。综上所述,我们的结果表明这些Vegfr2调控元件在一般成人血管新生过程中是活跃的。因此,这些序列可能被证明是新型内皮特异性抗血管生成以及促血管生成治疗策略的有价值靶点。它们尤其可能允许将治疗性基因表达导向成人血管新生部位。此外,Vegfr2/LacZ报告基因小鼠代表了一种强大的模型,可用于全面分析成人血管新生过程中Vegfr2表达诱导所涉及的转录控制机制。