Concurrent tracking of the trafficking of individual immune cell populations after myocardial infarction (MI) by ‘multicolor’ 1H/19F MRI

19F核磁共振已被证明是炎症无背景成像的一种极好的工具。为此，注射乳化的全氟碳化合物(PFC)，这些细胞优先被循环单核细胞吞噬，在渗入炎症灶后可通过1H/19F磁共振检测到。然而，B细胞、树突状细胞或中性粒细胞在一定条件下也可以内化PFC，小尺寸的PFC可能会通过泄漏的内皮被动扩散到炎性病变中。因此，检测到的19F信号来自复杂的细胞混合物，这些细胞被标记在血流中和/或局部内化PFC。最近，我们发展了19F MRI方法，通过将配备有配体的PFC定向到特定的表位，从而能够主动靶向单个细胞群体。此外，我们开发了一种成像技术，用于同时检测具有不同光谱特征的不同PFC，从而允许同时显示几个目标。为了克服上述限制，这项建议旨在扩展目前的方法，用于：1)针对中性粒细胞、经典/非经典单核细胞和CD4+T细胞：为此，我们将生成PFC来专门标记血流中不同的细胞类型，并实施“多色”19F压缩传感技术以提高检测阈值。我们已经揭示了一种针对中性粒细胞的靶向肽，并将使用噬菌体展示筛选来识别针对这两个单核细胞亚群的新配体。CD4+T细胞将被抗CD4单抗/单抗衍生物和/或具有CD4+T细胞特异性PFC内化特性的新型转基因小鼠靶向。2)追踪MI后免疫细胞的连续渗透和组织结构的变化：监测MI后中性粒细胞、经典/非经典单核细胞和CD4+T细胞进入心脏的情况，可以准确地描绘当前炎症状态的质量。结合多参数1H磁共振成像(T1、T2、CEST)，可以全面描述局部炎症和相关的组织结构变化。为了解决器官间的串扰，骨髓、脾、肾和肺也被包括在成像方案中，这将提供对MI后整体免疫细胞运输的洞察。通过这种方法，我们将进一步研究免疫易感性的改变如何影响心肌梗死后的结果。总之，这种方法将允许(I)局部区域区分不同免疫细胞群体的连续渗透以及组织特性的深入表征，以及(Ii)监测MI对免疫细胞向其他主要靶器官募集的影响。从长远来看，这种方法也可能被转移到临床环境中，以识别患者的个体炎症模式，从而为精确医学量身定做适当的治疗方案。

19F MRI has proven to be an excellent tool for background-free imaging of inflammation. For this, emulsified perfluorocarbons (PFCs) are injected, which are preferentially phagocytized by circulating monocytes that can be detected by 1H/19F MRI after infiltration into inflammatory foci. However, also B-cells, dendritic cells or neutrophils can internalize PFCs under certain conditions and small-sized PFCs may passively diffuse into inflammatory lesions via a leaky endothelium. Thus, the detected 19F signal is derived from a complex mixture of cells which were labelled in the bloodstream and/or locally internalized the PFCs. Lately, we advanced the 19F MRI approach by directing ligand-equipped PFCs to specific epitopes enabling an active targeting of individual cell populations. Furthermore, we developed an imaging technique for concurrent detection of different PFCs with distinct spectral signatures allowing the simultaneous visualization of several targets. To overcome the described limitations, this proposal is aimed at expanding the current approach for:1) Specific targeting of neutrophils, classical/non-classical monocytes and CD4+ T-cells: For this, we will generate PFCs to specifically label the distinct cell types within the bloodstream and implement a ‘multicolor’ 19F compressed sensing technique to enhance the detection thresholds. We already revealed a targeting peptide for neutrophils and will identify novel ligands against both monocyte subsets using phage display screening. CD4+ T-cells will be targeted by anti-CD4 mAb/mAb-derivatives and/or by a novel transgenic mouse with specific PFC internalization properties of CD4+ T-cells. 2) Tracking sequential immune cell infiltration and alterations in tissue texture after MI: Monitoring the infiltration of neutrophils, classical/non-classical monocytes and CD4+ T-cells into the heart after MI will enable a precise mapping of the quality of the current inflammatory state. In combination with multiparametric 1H MRI (T1, T2, CEST), this allows a comprehensive characterization of local inflammation and associated alterations in tissue textures. To address interorgan crosstalk also bone marrow, spleen, kidney and lung are included into the imaging protocol which will provide insight in the overall immune cell trafficking after MI. With this approach, we will furthermore investigate how an altered immunological predisposition will impact on the outcome after MI. In summary, this approach will permit (i) locoregional discrimination of the sequential infiltration of distinct immune cell populations together with in-depths characterization of tissue properties and (ii) to monitor the effect of MI on immune cell recruitment to other major target organs. In the long run, this approach might also be transferred to the clinical setting for identification of individual inflammation patterns in patients to tailor adequate therapy regimes for precision medicine.