Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tübingen, 72076 Tübingen, Germany.
Department of Dermatology, University Medical Center, Eberhard Karls University Tübingen, 72076 Tübingen, Germany.
Theranostics. 2019 Apr 13;9(10):2868-2881. doi: 10.7150/thno.28892. eCollection 2019.
In a variety of diseases, from benign to life-threatening ones, inflammation plays a major role. Monitoring the intensity and extent of a multifaceted inflammatory process has become a cornerstone in diagnostics and therapy monitoring. However, the current tools lack the ability to provide insight into one of its most crucial aspects, namely, the alteration of the extracellular matrix (ECM). Using a radiolabeled platelet glycoprotein VI-based ECM-targeting fusion protein (GPVI-Fc), we investigated how binding of GPVI-Fc on fibrous tissue could uncover the progression of several inflammatory disease models at different stages (rheumatoid arthritis, cutaneous delayed-type hypersensitivity, lung inflammation and experimental autoimmune encephalomyelitis). The fusion protein GPVI-Fc was covalently linked to 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and subsequently labeled with Cu. We analyzed noninvasively Cu-GPVI-Fc accumulation in murine cutaneous delayed-type hypersensitivity, anti-glucose-6-phosphate isomerase serum-induced rheumatoid arthritis, lipopolysaccharide-induced lung inflammation and an experimental autoimmune encephalomyelitis model. Static and dynamic Positron Emission Tomography (PET) of the radiotracer distribution was performed , with autoradiography confirmation, yielding quantitative accumulation and a distribution map of Cu-GPVI-Fc. tissue histological staining was performed on harvested samples to highlight the fusion protein binding to collagen I, II and III, fibronectin and fibrinogen as well as the morphology of excised tissue. Cu-GPVI-Fc showed a several-fold increased uptake in inflamed tissue compared to control tissue, particularly in the RA model, with a peak 24 h after radiotracer injection of up to half the injected dose. Blocking and isotype control experiments indicated a target-driven accumulation of the radiotracer in the case of chronic inflammation. Histological analysis confirmed a prolonged accumulation at the inflammation site, with a pronounced colocalization with the different components of the ECM (collagen III and fibronectin notably). Binding of the fusion protein appeared to be specific to the ECM but unspecific to particular components. Imaging of Cu-GPVI-Fc accumulation in the ECM matrix appears to be a promising candidate for monitoring chronic inflammation. By binding to exposed fibrous tissue (collagen, fibronectin, etc.) after extravasation, a new insight is provided into the fibrotic events resulting from a prolonged inflammatory state.
在各种疾病中，从良性到危及生命的疾病，炎症都起着重要作用。监测炎症这一多方面过程的强度和程度已成为诊断和治疗监测的基石。然而，目前的工具缺乏提供其最关键方面之一的洞察力的能力，即细胞外基质（ECM）的改变。我们使用放射性标记的血小板糖蛋白 VI 基 ECM 靶向融合蛋白（GPVI-Fc），研究了 GPVI-Fc 与纤维组织的结合如何在不同阶段（类风湿关节炎、皮肤迟发型超敏反应、肺部炎症和实验性自身免疫性脑脊髓炎）揭示几种炎症疾病模型的进展。融合蛋白 GPVI-Fc 与 1,4,7-三氮杂环壬烷-1,4,7-三乙酸（NOTA）共价连接，然后用 Cu 标记。我们在小鼠皮肤迟发型超敏反应、抗葡萄糖-6-磷酸异构酶血清诱导的类风湿关节炎、脂多糖诱导的肺部炎症和实验性自身免疫性脑脊髓炎模型中分析了非侵入性 Cu-GPVI-Fc 的积累。对示踪剂分布进行了静态和动态正电子发射断层扫描（PET），并进行了放射自显影确认，得出了 Cu-GPVI-Fc 的定量积累和分布图。对采集的样本进行组织学染色，以突出融合蛋白与胶原 I、II 和 III、纤维连接蛋白和纤维蛋白原以及切除组织的形态的结合。与对照组织相比，Cu-GPVI-Fc 在炎症组织中的摄取增加了几倍，尤其是在 RA 模型中，在放射性示踪剂注射后 24 小时达到了注射剂量的一半。阻断和同型对照实验表明，在慢性炎症的情况下，示踪剂的积累是靶向驱动的。组织学分析证实了在炎症部位的长时间积累，与 ECM 的不同成分（尤其是胶原 III 和纤维连接蛋白）的明显共定位。融合蛋白的结合似乎对 ECM 是特异性的，但对特定成分是非特异性的。在 ECM 基质中观察到 Cu-GPVI-Fc 积累的成像似乎是监测慢性炎症的有前途的候选方法。通过在渗出后与暴露的纤维组织（胶原、纤维连接蛋白等）结合，为长期炎症状态引起的纤维化事件提供了新的见解。
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