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

19 F MRI已被证明是炎症无背景成像的绝佳工具。为此，注射乳化的全氟化碳（PFC），其优先被循环单核细胞吞噬，所述循环单核细胞可以在浸润到炎性病灶中之后通过1H/19 F MRI检测到。然而，B细胞、树突状细胞或嗜中性粒细胞也可以在某些条件下内化PFCs，并且小尺寸的PFCs可以通过渗漏的内皮被动地扩散到炎性病变中。因此，检测到的19 F信号来源于在血流中标记和/或局部内化PFC的细胞的复杂混合物。最近，我们通过将配体装备的PFC引导至特定表位来推进19 F MRI方法，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，用于同时检测不同的PFC，具有不同的光谱特征，允许同时可视化的几个目标。为了克服所描述的局限性，该提议旨在扩展当前的方法：1）嗜中性粒细胞、经典/非经典单核细胞和CD 4 + T细胞的特异性靶向：为此，我们将产生PFC以特异性标记血流内的不同细胞类型，并实施“双”19 F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，并将利用噬菌体展示筛选来鉴定针对这两种单核细胞亚群的新型配体。抗CD 4 mAb/mAb衍生物和/或具有CD 4 + T细胞特异性PFC内化特性的新型转基因小鼠将靶向CD 4 + T细胞。2)追踪MI后免疫细胞浸润和组织质地的改变：监测MI后中性粒细胞、经典/非经典单核细胞和CD 4 + T细胞向心脏的浸润将能够精确绘制当前炎症状态的质量。结合多参数1H MRI（T1，T2，CEST），可以全面表征局部炎症和组织纹理的相关变化。为了解决器官间串扰，还将骨髓、脾、肾和肺纳入成像方案中，这将提供MI后整体免疫细胞运输的见解。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MI后的结局。总之，这种方法将允许（i）局部区分不同免疫细胞群体的顺序浸润以及组织特性的深入表征，以及（ii）监测MI对免疫细胞募集到其他主要靶器官的影响。从长远来看，这种方法也可能被转移到临床环境中，用于识别患者的个体炎症模式，为精准医学定制适当的治疗方案。

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.