Surgical Intramyocardial Angiogenesis in a Swine Model

血管生成是治疗冠状动脉疾病（CAD）的一种有前途的新治疗方式。 然而，尽管我们实验室和其他实验室的动物研究结果令人印象深刻，但血管生成疗法在人类中的初步临床应用仅产生了适度的客观益处。终末期CAD患者是目前血管生成治疗的目标人群，几乎所有患者都有晚期内皮功能障碍，导致内皮物质的产生和反应异常。 由于血管生成生长因子在很大程度上通过激活酪氨酸激酶受体释放内皮源性一氧化氮来发挥作用，因此在终末期CAD患者中观察到的效果失败可能与这些内皮源性物质的刺激释放不足有关。 本研究旨在明确内皮功能对外源性生长因子治疗的影响以及对心肌缺血的内源性血管生成反应的作用。 为此，将使用高胆固醇血症猪模型，重现与CAD患者相似的心肌微循环变化。 将创建几个研究组，包括具有正常、功能障碍或血管内皮细胞治疗的动物，其中将进行慢性心肌缺血的手术诱导和缓释生长因子装置（FGF-2、VEGF或安慰剂）的植入。 在每个研究组中，将在微血管反应性研究中对内皮反应进行体外评估，并使用心肌灌注同位素标记微球测定、超声显微测量、免疫细胞化学和真实的时间PCR分析等工具，在功能、微血管、组织学和分子水平上定量测定血管生成反应。 通过阐明内皮和内皮调节剂在功能性血管生成反应中的作用，本研究的结果将导致对治疗性血管生成的更完整的理解，并可能使这种治疗方式发展成为一种安全，有效和有吸引力的CAD治疗选择。

Angiogenesis is a promising new therapeutic modality for the treatment of coronary artery disease (CAD). However, despite impressive results of animal studies from our laboratory as well as others, preliminary clinical use of angiogenic therapy in humans has only resulted in modest if any objective benefit. Patients with end-stage CAD, who represent the population currently targeted by angiogenic therapy, virtually all have advanced endothelial dysfunction that results in abnormal production and response to endothelial substances. Since angiogenic growth factors operate in large part through the release of endothelial-derived nitric oxide via the activation of tyrosine kinase receptors, the observed failure of effect in patients with end-stage CAD may relate to a deficiency in the stimulated release of these endothelial-derived substances. This research proposes to define the role of endothelial function on the effects of exogenous growth factor therapy and on the endogenous angiogenic response to myocardial ischemia. To this end, a hypercholesterolemic porcine model will be used that recreates myocardial microcirculatory changes similar to those encountered in humans with CAD. Several study groups that include animals with normal, dysfunctional, or pharmacologically- treated endothelium will be created, in which surgical induction of chronic myocardial ischemia and implantation of sustained- release growth factor devices (FGF-2, VEGF, or placebo) will be performed. In each study group, endothelial responses will be assessed in vitro on microvascular reactivity studies, and the angiogenic response will be quantitatively determined at the functional, microvascular, histological, and molecular levels, using tools such as isotope-labeled microsphere assays of myocardial perfusion, sonomicrometry, immunocytochemistry and real time PCR analysis. By clarifying the role of the endothelium and endothelial-modulating agents in the functional angiogenic response, the findings from this research will lead to a more complete understanding of therapeutic angiogenesis, and may allow for the development of this modality towards a safe, effective, and attractive option for the treatment of CAD.