诊断超声联合环RGD微泡通过靶向消溶富血小板血栓稳定易损斑块的实验研究

Stabilization of atherosclerotic plaques has great important clinical implications for preventing future cardiovascular events. Unfortunately, current methods for stabling vulnerable plaques are limited. Accumulated evidence has shown that activated platelet/platelet-rich thrombus in plaques which were significantly related to plaque vulnerability, maybe can serve as a novel target for the treatment of vulnerable plaques. However, systemic anti-platelet agents without plaque-targeting have shown limited success in clinical practice because of bleed risk and drug resistance. Ultrasound combined with microbubble can dissolve the acute platelet-rich thrombus in large vascular through its direct and localized mechanical damage on vessel walls. In additation, our previous studies have demonstrated that low-intensity diagnostic ultrasound combined with MB-cRGD (DU+MB-cRGD) can targeted imaging the activated platelets in the plaques. Therefore, we hypothesized that low-intensity DU+MB-cRGD is capable to targeted dissolve the activated platelets/platelet-rich thrombi in plaque and consequently improve the vulnerability of plaque. This project is proposed to: (1) verify the correlation between the activated platelet in the plaque and its vulnerability; (2) explore the appropriate ultrasound condition for targeted dissolving the activated platelet in the plaque; (3) evaluate the effect of DU+MB-cRGD on treatment of vulnerable plaques and its pathological mechanism by ultrasound molecular imaging, histological examinations, scanning/transimission electron microscopy test, so as to develop an efficient and safe approach for the treatment of vulnerable plaques.

稳定动脉易损斑块具有重要的临床价值，然而，目前其治疗手段具有一定的局限性。研究显示：斑块内聚集的活化血小板或富血小板血栓与易损性显著相关，表明斑块内活化血小板可作为治疗易损斑块的靶点，然而抗血小板药物的治疗缺乏局部靶向性，其出血风险及药物抵抗现象限制了其临床应用。超声联合微泡可以通过对血管壁产生直接和局部的物理损伤效应，溶解大血管急性富血小板血栓，而且我们前期研究已证实诊断超声联合环RGD微泡能靶向显影易损斑块上的活化血小板。因此，我们提出假设：诊断超声联合环RGD微泡能靶向消溶斑块内的活化血小板从而改善斑块易损性。本项目拟采用超声分子成像、组织病理和电镜等方法，在小鼠动脉粥样模型上，A、验证斑块内活化血小板与其易损性相关；B、探索靶向消溶斑块内活化血小板的适宜超声条件；C、评价超声联合MBcRGD治疗易损斑块的有效性和可行性及其病理机制，以期发展出一种有效、安全的治疗易损斑块的新方法。

稳定和逆转易损斑块是有效预防和减少急性动脉粥样硬化心血管事件发生的最根本措施，斑块内聚集的活化血小板以及斑块内的新生血管均与易损性显著相关，两者均可作为治疗易损斑块的靶点。然而，抗血小板药物的治疗缺乏局部靶向性，其出血风险及药物抵抗现象限制了其临床应用；而且临床上亦缺乏可选择性抑制斑块内血管新生的有效方法。因此，以斑块内聚集的活化血小板以及斑块内的新生血管为治疗靶点，我们分别开展两部分的实验研究：A)探讨了诊断超声联合携环RGD靶向微泡消溶斑块内聚集的活化血小板进而稳定易损斑块的可行性及其可能病理机制；B)探讨了微聚焦治疗超声联合普通微泡选择性毁损斑块内新生血管的可行性研究。我们的研究结果发现：A)适宜机械指数的诊断超声联合携环RGD微泡靶向活血小板上的GPIIb/IIIa受体能够快速检测识别动脉粥样硬化斑块，并可以通过靶向消溶斑块内聚集的活化血小板改善斑块的稳定性，有望发展出一种安全，有效的稳定和逆转易损斑块的一种新技术，并可避免“抗血小板药物”的全身毒副作用；B)合适能量的微聚焦治疗超声联合普通微泡可以选择性毁损斑块内的新生滋养血管，进而达到稳定易损斑块的目的，亦有望发展出一种无创、有效的用于临床稳定易损斑块的新方法。