斑块炎症和动脉血栓超声分子成像评价易损斑块的可行性

Identification of vulnerable plaques has great important clinical implications for predicting and preventing future cardiovascular events, which is responsible for the high mortality rate. Unfortunately, current noninvasive imaging methods for visualizing the vulnerable plaque are clinically limited. Many targeting molecules of inflammation and thrombosis, such as P-selectin, ICAM-1, VCAM-1, TF, vWF and GPIIb/IIIa, play a crucial role in vulnerable plaques and have an elevated level of expression. Ultrasound molecular imaging (UMI) offers the possibility of real-time, noninvasive visualization of those molecular markers, has a potential to detect vulnerable plaques. However, it was hampered by "axial flow phenomenon" and high shear stress in larger arterial vessels. We, recently, have developed two novel site-targeted microbubbles, magnetic microbubbles targeted to VCAM-1 and microbubbles modified by cyclic RGD, which could overcome the hampers in larger arterial vessels. In vitro and in vivo we have demonstrated they increase binding to relevant molecular targets, resulting in improved the detection of molecular changes of inflammatory atherosclerosis and arterial thrombi. We, therefore, hypothesized that direct imaging of the biologic targets involved in inflammation and thrombosis in atherosclerosis by UMI could identify and detect the vulnerable plaques. In this study, we are going to filter and identify the candidate molecules, which would be the molecular markers for the vulnerable plaque, by Proteomics and confirmed by histopathology, western blotting and immunohistochemistry. The targeted molecular markers for vulnerable plaque, such as P-selectin, ICAM-1, VCAM-1, TF, vWF and GPIIb/IIIa, et al, are then used to create magnetic or non-magnetic ultrasound molecular probes. In atherosclerotic mouse model, we are going to clarify the relations between ultrasound molecular signal and histopathological indicators of atherosclerosis (such as macrophages, smooth muscle cells, fibrous cap, necrotic core, vasa vasorum, et al), to determine the role of UMI in detecting the vulnerable plaques and evaluating the therapeutic effect. This study would provide new insight into the vulnerable plaques and eventually lead to development of new noninvasive approach to identify vulnerable plaques.

识别和预警易损斑块有重要临床价值，目前缺乏有效的无创影像诊断手段。易损斑块中有大量炎症和血栓相关蛋白分子高表达。超声分子成像（UMI）可以评价这些分子的变化，有望识别易损斑块。然而，大动脉的"轴流现象"和高剪切应力制约了其发展。我们前期创新构建出携VCAM-1单抗磁性靶泡和携环RGD多肽靶泡，突破了制约动脉UMI的瓶颈，它们可以提高斑块炎症和动脉血栓UMI能力。因此，我们假设通过UMI评价斑块炎症和血栓相关分子的表达水平可识别易损斑块。本项目拟采用蛋白质组学、免疫组化和免疫印迹等手段筛选和证实可表征易损斑块的蛋白分子（如：P-selectin、VCAM-1、TF、vWF和GPIIb/IIIa等），以其为靶点构建超声分子探针，在小鼠斑块模型上阐明分子探针信号与斑块组织病理学指标（巨噬细胞数量、纤维帽厚度和脂质坏死中心大小等）的关系，以期获得无创评价易损斑块的新方法和有重要学术价值的研究成果。

识别和预警易损斑块有重要临床价值，目前缺乏有效的无创影像诊断手段。超声分子成像可以评价易损斑块中高表达的炎症和血栓相关蛋白分子，有望识别易损斑块。然而，大动脉的高剪切应力制约了其发展。我们前期成功构建携cRGD靶泡，突破了制约动脉UMI的瓶颈。本项目的研究结果表明cRGD靶向微泡显著提高在高剪切应力下靶向微泡的粘附动脉富含血小板血栓中活化血小板的效能。在确定携cRGD靶向微泡对活化血小板的靶向效果后，我们应用小鼠动脉粥样硬化斑块模型证实动脉斑块内皮上血小板的数量和GP IIb/IIIa受体与斑块的稳定性相关，是理想的超声分子成像靶点,靶向GP IIb/IIIa的超声分子成像可以定量评价血小板上的GP IIb/IIIa受体，其声强度与GP IIb/IIIa表达水平显著相关，进一步阐明了超声分子成像评价易损斑块的可行性。本项目的研究成果为超声分子成像和其它的分子成像技术评价易损斑块提供有价值的分子学基础，靶向血小板上的GP IIb/IIIa受体有望成为一种无创、有效评价易损斑块的新方法。