Ultrasound-Assisted Thrombolysis for Stroke Therapy

描述(申请人提供)：超声和组织型纤溶酶原激活剂(rt-PA)联合治疗，或超声溶栓，已被证明能改善急性缺血性中风患者的再通。为了减少出血事件的风险，已经研究了加强溶栓的有效方法。在我们正在进行的研究中，我们已经证明了显著的溶栓增强与存在稳定的空化相关，这种类型的温和气泡活动可以通过间歇注入造影剂来维持。此外，我们还展示了一氧化氮和其他生物活性气体的包裹和超声触发释放，以促进血管扩张和神经保护。这些初步数据有力地支持了我们建议的中心假设，即超声主要通过机械机制促进血栓溶解。为了验证这一假设，我们建议研究三个具体目标：在目标1中，我们将开发一种双元件环形阵列换能器，以促进220 kHz脉冲超声照射和体内和体外被动空化检测。在整个治疗过程中监测稳定空化的能力将有助于自动化控制和优化溶栓增强。在目标2中，我们将通过在猪出血性中风模型中的活体研究，证明使用t-Elip或rt-PA和造影剂进行220 kHz超声增强溶栓的有效性。作为Aim#2中的一种新方法，我们还将评估通过加载硫化氢、神经保护剂和八氟丙烷的混合物以形成气泡活性的Elip治疗脑出血所达到的神经保护程度，并与加载神经保护剂氙气和少量气泡成核剂的Elip进行比较。在目标3中，我们将在猪动脉血栓模型中研究回声脂质体输送rt-PA和一氧化氮(一种生物活性气体)的可能性。这些研究的成功完成将阐明超声增强溶栓和超声介导的血管扩张或细胞保护气体输送的有效性和潜在风险，并将为设计靶向药物以改善急性卒中治疗中的血栓溶解和神经保护提供重要的新信息。

DESCRIPTION (provided by applicant): Combined ultrasound and tissue plasminogen activator (rt-PA) therapy, or sonothrombolysis, has been shown to improve recanalization in patients with acute ischemic stroke. Effective methods of enhancing thrombolysis have been examined in an attempt to reduce the risk of hemorrhagic events. In our ongoing studies, we have demonstrated that significant enhancement of thrombolysis correlates with the presence of stable cavitation and this type of gentle bubble activity can be sustained using an intermittent infusion of a contrast agent. In addition, we have demonstrated encapsulation and ultrasound-triggered release of nitric oxide and other bioactive gases to promote vasodilation, and neuroprotection. These preliminary data strongly support the central hypothesis of our proposal that ultrasound enhances thrombolysis primarily via mechanical mechanisms. To test this hypothesis we propose to investigate three Specific Aims: In Aim #1, we will develop a dual-element annular array transducer to facilitate simultaneous 220-kHz pulsed ultrasound exposure and passive cavitation detection in vitro and in vivo. The ability to monitor stable cavitation throughout treatment will aid in the automated control and optimization of thrombolytic enhancement. In Aim #2, we will demonstrate the efficacy of 220-kHz ultrasound- enhanced thrombolysis using t-ELIP or rt-PA and a contrast agent through in vivo studies in a porcine hemorrhagic stroke model. As a novel approach in Aim #2, we will also evaluate the degree of neuroprotection achieved by treating the intracerebral hemorrhage with ELIP loaded with a mixture of hydrogen sulfide, a neuroprotectant, and octofluoropropane to nucleate bubble activity, and compare to ELIP loaded with a mixture of xenon, a neuroprotectant, and with a smaller amount of the bubble nucleation agent. In Aim #3, we will investigate the potential of echogenic liposomes to deliver rt-PA and nitric oxide, a bioactive gas, in a porcine arterial thrombus model. Successful completion of the proposed studies will elucidate the utility and potential risks of ultrasound-enhanced thrombolysis and ultrasound-mediated delivery of vasodilatory or cytoprotective gases and will provide important new information to assist the design of targeted agents to improve thrombolysis and neuroprotection in acute stroke treatment.