超小超顺磁性氧化铁标记树突状细胞对兔动脉粥样硬化的磁共振成像研究

Atherosclerosis is an inflammatory disease involving activation of responses to modified lipoproteins. Dendritic cells (DCs) are professional antigen-presenting cells that activate T cells. DCs present in atherosclerotic development process, and are the major factors and starting center, because they move to inflammation plaques directional, rich in plaque, and have close relationship with the stability of the plaques. In this project, we choose white New Zealand rabbit as experimental subject, to establish the atherosclerosis animal model through endothelial abrasion of the abdominal aorta combined with high-fat and high-cholesterol diet. The specific molecular imaging probe is made with ultrasmall superparamagnetic iron oxide particles (USPIO) marked dendritic cell which is divided from bone marrow of rabbit. The specific molecular imaging probe is used for magnetic resonance imaging target study of atherosclerosis plaque, and the results will be compared with pathological findings and electron microscopy observation. The project is to show atherosclerotic plaques on MR imaging and explore atherosclerosis formation mechanism through the vivo tracking of dendritic cells in atherosclerotic plaque formation process with molecular imaging methods, to provide experimental evidence for clinical MR examinations of human atherosclerosis, to evaluate the stability of plaque and, to make the early positioning and qualitative diagnosis of the atherosclerosis plaque, to guide clinically making early treatment and evaluation prognosis, and to reduce the morbidity and mortality of the disease.

动脉粥样硬化是一种与炎症免疫反应有关的疾病。树突状细胞是抗原递呈细胞。在动脉粥样硬化发生发展过程中，树突状细胞向炎症的斑块定向运动，并在斑块中丰富表达，是动脉粥样硬化免疫反应中主要的起始因素和中心环节，并与斑块的稳定性密切相关。本项目以新西兰大白兔为实验对象，通过损伤动脉内膜及高脂饮食建立动脉粥样硬化动物模型，用超小超顺磁性氧化铁颗粒（USPIO）标记从兔骨髓中分离培养出的树突状细胞制成特定的分子影像学探针，对兔动脉粥样硬化斑块进行磁共振靶向成像研究，并将影像学结果与病理学及电镜结果相对照。以期用分子影像学方法对树突状细胞在动脉粥样硬化斑块形成过程中进行活体示踪，从一个侧面阐明动脉粥样硬化的形成机制，为人类动脉粥样硬化的临床MRI检查提供实验依据，对动脉粥样硬化斑块进行早期定位及定性诊断，并评价斑块的稳定性。从而指导临床对该病进行早期治疗及判断预后，降低心、脑血管系统疾病的发生率及致残率。

动脉粥样硬化是心血管疾病的主要诱因，识别易损斑块和治疗将有助于降低临床终末事件的风险。目前，斑块的磁共振成像存在一些困难，也有使用超顺磁性氧化铁(SPIO)作为造影剂进行研究的报道。然而，很少有研究将SPIO与药物结合到治疗性纳米复合物中。本研究依据斑块微环境为弱酸性的条件下，探索生物相容性顺磁性氧化铁纳米颗粒(NPs)联合低ph敏感性环糊精用于动脉粥样硬化的影像学诊断和治疗。此外，斑块的血管平滑肌细胞(VSMCs)富含profilin-1，这是一种参与细胞骨架聚合调控和重组的小的肌动蛋白结合蛋白动脉硬化斑块高表达profilin-1蛋白，最近的研究表明，profilin-1的过表达主要通过调控VSMCs的增殖和迁移，引起动脉粥样硬化、高血压、心肌肥厚等心血管疾病的发生。本研究构建的分子探针，特别是与profilin-1抗体(PFN1)结合的纳米探针，体外实验证实能够靶向动脉粥样硬化血管平滑肌细胞(VSMCs)。我们进一步用抗炎药物雷帕霉素(RAP)构建RAP@PFN1-CD-MNPs纳米药物，其在体内体外均具有良好的生物相容性及靶向性。此外，与PFN1结合的PFN1-CD-MNPs在长期治疗中降低了CD-MNPs的肾毒性。体内磁共振成像(MRI)和体外近红外荧光(NIRF)显示PFN1-CD-MNPs在动脉粥样硬化斑块中的积累。离体荧光实验证实RAP@PFN1-CD-MNPs纳米药物能缓解动脉硬化进展。因此，PFN1-CD-MNPs不仅是一种有前途的多功能成像探针，而且可以作为未来动脉粥样硬化诊疗一体化纳米平台的响应性纳米载体，是一种很有前途的纳米载体。