Augmentation of Tissue Perfusion with Ultrasound-mediated Cavitation

总结 超声（US）用于各种治疗应用。在不同的频率范围内， 美国已被证明可以适度增加动脉直径和组织灌注 在肢体和心肌缺血的动物模型中。在该奖项的最初资助期间，我们描述了如何 US与微泡（MB）造影剂的组合在高功率造影期间经历惯性空化， 对比增强的US（CEU）产生更大的肢体骨骼肌灌注增强（高达 10倍）比我们单独。发现简单的CEU空化方案可以逆转肢体缺血>24小时， 动物模型和外周动脉疾病（PAD）患者的临床试验证实，MB空化 使肢体灌注增加数倍。在我们的研究过程中，这些生物效应的最佳条件 这要求我们设计新的US脉冲方案和3-D曝光能力。从 从机械的角度来看，我们仔细绘制了负责空化诱导流动增强的路径 其依赖于内皮细胞和红细胞的剪切介导的ATP释放， 通过下游介质（NO、胰高血糖素、腺苷）舒张血管。最佳知识 条件和机械基础是至关重要的，我们目前的努力，应用空化和激活的 ATP通道通过增加血流或通过其他潜在有益的抗血栓形成治疗缺血性疾病 和嘌呤能信号的抗炎作用。这次更新的总体目标是利用知识 从第一个资助期，以探讨空化和非空化US的治疗作用， 急性和慢性缺血综合征。在目标1中，临床前模型将用于确定肢体是否 使用先前优化的脉冲方案的MB空化的流量增强可以：（a）防止组织 急性缺血中的坏死，特别关注临床变量（年龄，性别，高脂血症， 糖尿病），和（B）改善慢性疾病中的伤口愈合和肢体功能。嘌呤能的功能作用 将通过使用抑制剂策略或基因修饰的模型来评估血管信号传导。在目标2中， 使用小鼠模型确定MB空化是否直接增加急性MI中的心肌灌注， 使我们能够操纵嘌呤能通路，并在灵长类动物模型中更接近人类生物学。 我们还将研究US介导的ATP释放如何具有减轻炎症和微血管损伤的潜力。 再灌注后血栓形成。在目标3中，我们将测试来自多元素高功率内部的US能量是否 动脉导管通过剪切介导的嘌呤能途径增加下游灌注。该目的是 基于在肺栓塞患者中使用治疗性US导管可以减少 肺血管阻力，即使没有血块溶解。我们的建议代表了以下转化步骤： 开发急性和慢性血管疾病的非侵入性疗法，并将为 我们计划启动的临床试验的设计，因为关键的未解决的问题得到解决。

SUMMARY Ultrasound (US) is used for a variety of therapeutic applications. Over a range of different frequencies and powers, US has been shown to produce to produce modest increases in arterial diameter and tissue perfusion in animal models of limb and myocardial ischemia. In the initial funding period for this award, we described how the combination of US with microbubble (MB) contrast agents that undergo inertial cavitation during high-power contrast-enhanced US (CEU) produces much greater augmentation of limb skeletal muscle perfusion (up to 10-fold) than US alone. Brief CEU cavitation protocols were found to reverse limb ischemia for >24 hrs in animal models, and a clinical trial in patients with peripheral artery disease (PAD) confirmed that MB cavitation increases limb perfusion by several fold. In the course of our studies, optimal conditions for these bioeffects were investigated which mandated us to design novel US pulse schemes and 3-D exposure capability. From a mechanistic standpoint, we carefully mapped pathways responsible for cavitation-induced flow augmentation which rely on shear-mediated ATP release from endothelial cells and erythrocytes, with secondary purinergic vasodilation through downstream mediators (NO, prostaglandins, adenosine). Knowledge of the optimal conditions and mechanistic underpinnings is critical for our current efforts to apply cavitation and activation of ATP channels to treat ischemic disease by augmenting flow or by other potentially beneficial anti-thrombotic and anti-inflammatory effects of purinergic signaling. The overall aim of this renewal is to leverage knowledge from the first funding period in order to explore the therapeutic role of cavitation and non-cavitation US for acute and chronic ischemic syndromes. In Aim 1 preclinical models will be used to determine whether limb flow-augmentation from MB cavitation using previously-optimized pulse schemes can: (a) prevent tissue necrosis in acute ischemia, with a particular focus on the effect of clinical variables (age, sex, hyperlipidemia, diabetes), and (b) improve wound healing and limb function in chronic disease. The functional role of purinergic vascular signaling will be evaluated by using inhibitor strategies or gene--modified models. In Aim 2 we will determine whether MB cavitation directly augments myocardial perfusion in acute MI using murine models that allow us to manipulate purinergic pathways, and in primate models that more closely resemble human biology. We will also study how US-mediated ATP release has the potential to mitigate inflammation, and microvascular thrombosis upon reperfusion. In Aim 3 we will test whether US energy from multi-element high-power intra- arterial catheters increases downstream perfusion through shear-mediated purinergic pathways. This Aim is based on evidence that therapeutic US catheters used in patients with pulmonary embolism can reduce pulmonary vascular resistance even without clot lysis. Our proposal represents the translational steps for development of non-invasive therapies for acute and chronic vascular diseases and will form the basis for the design of clinical trials that we plan to initiate as the key unsolved issues are addressed.