64Cu-NOTA-CD44-Fc PET/CT显像检测冠状动脉粥样硬化侵蚀斑块的可行性研究

Recent studies have found that 1/3 patients with acute coronary syndrome are caused by plaque erosion. Early detection of erosive plaques is essential to reduce the occurrence of ACS. The histological characteristics between eroded and ruptured plaques are diferent significantly, and existed PET molecular probes cannot specifically detect erosive plaques. Our previous study found that 18F-NaF PET/CT could well display the ruptured plaques, but could not identify criminal lesions of ACS caused by erosive plaques. The results of Boris's study suggested that platelet membrane glycoprotein VI (GPVI) labeled by 64Cu could detect erosive plaques by PET/CT imaging, but this probe have no specificity for detecting eroded plaques. .Rich in hyaluronan is the main feature of erosive plaques, and recent study published by JACC suggest that hyaluronan has great potential as a target for detecting erosive plaques. The N-terminal of CD44 peptide chain can specifically bind to hyaluronan, and human studies have confirmed that hyaluronan can specifically bind to CD44 which over-expressed on the surface of cells. In this study, molecular probe 64Cu-NOTA-CD44-Fc will be synthesized, and comparing 64Cu-NOTA-CD44-Fc micro PET/CT of ApoE-/- atherosclerosis model mice with 18F-NaF micro PET/CT, immunohistochemistry and autoradiography. To explore the feasibility of hyaluronan specific detection of erosive plaque with this probe, it is expected that 64Cu-NOTA-CD44-Fc can become the molecular probe that can specifically detect the erosion plaque so far.

近年研究发现1/3的急性冠脉综合征（ACS）是由侵蚀斑块引起的，早期检测侵蚀斑块对减少ACS发生至关重要。侵蚀斑块与破裂斑块组织学特征差异较大，已有的PET分子探针无法特异检测侵蚀斑块。我们前期研究发现18F-NaF PET能很好的显示破裂斑块，但无法识别由侵蚀斑块所致的罪犯病变。Boris研究提示64Cu-GPVI-Fc PET可显示侵蚀斑块但非特异。富含透明质酸（HA）是侵蚀斑块的主要组织学特征，最近JACC发表研究提示HA作为检测侵蚀斑块的靶点潜力巨大。CD44可特异性结合HA，已证实HA可与细胞表面过表达的CD44特异性结合。本研究拟合成64Cu-NOTA-CD44-Fc，研究其与ApoE-/-动脉粥样硬化模型小鼠18F-NaF micro PET成像、免疫组化及放射自显影的相关研究，探讨该探针靶向HA特异性检测侵蚀斑块的可行性，期望它成为目前为止可以特异性检测侵蚀斑块的分子探针。

近1/3的急性冠脉综合征（acute coronary syndrome, ACS）是由侵蚀斑块引起的，侵蚀斑块常无阻塞性病变且与破裂斑块组织学特征差异较大，现有的影像学手段及分子探针无法有效的早期可视化侵蚀斑块。研究表明，侵蚀斑块表面富含大量透明质酸（hyaluronan acid, HA）是其主要组织学特征，CD44蛋白可特异性结合HA。本项目通过新型分子探针64Cu-NOTA-CD44的合成及其生物学性质研究，ApoE-/-动脉粥样硬化模型小鼠micro PET/CT及其病理、生化对照研究。获得的重要结果如下：1.在小分子人重组CD44蛋白C端通过化学键改造及修饰后成功合成探针64Cu-NOTA-CD44，并证实其靶向HA具有较高的亲和力，体内外稳定性好，体内药代动力学特征良好；2.动脉粥样硬化模型小鼠病变部位摄取64Cu-NOTA-CD44及18F-NaF水平均较对照组增高，随周龄越高越明显，但两者的高摄取部位及水平存在差异，64Cu-NOTA-CD44高摄取部位存在大量HA，而18F-NaF高摄取部位钙化成分少见，但无论哪种显像剂高摄取部位均伴有大量的炎症浸润。本项目的主要科学意义在于，构建了一种新型分子探针64Cu-NOTA-CD44，其靶向HA具有高亲和力、高特异性、体内外稳定性好、核素标记率及放射性化学纯度高、体内药代动力学特征良好，micro PET/CT成像显示它可以早期结合在动脉粥样硬化模型鼠侵蚀斑块病变处，具有高靶/本底比，且摄取水平与病理及代谢组学所示斑块危险程度一致性良好，可以早期识别及预警动脉粥样硬化不稳定斑块，为冠心病动脉粥样硬化的诊治提供新靶点及疗效评估手段，此外，通过证实64Cu-NOTA-CD44靶向HA识别的侵蚀斑块与18F-NaF基于微钙化检测的易损斑块有所不同，但病变部位均存在病理证实的大量的炎症巨噬细胞浸润，提示易损斑块的关键病理机制复杂多样，不同靶点探针识别的易损斑块有差异，但炎症反应始终贯穿整个动脉粥样硬化过程。