Molecular Imaging and Theranostics Laboratory (A.P.G.W., E.Y., V.B., X.W.), Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.
Atherothrombosis and Vascular Biology Laboratory (A.P.G.W., E.Y., J.D.M., V.B., M.J.M., A.H., K.P.), Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.
Arterioscler Thromb Vasc Biol. 2023 Jun;43(6):1031-1040. doi: 10.1161/ATVBAHA.122.318883. Epub 2023 Apr 20.
Current clinical imaging of thromboembolic diseases often relies on indirect detection of thrombi, which may delay diagnosis and ultimately the institution of beneficial, potentially lifesaving treatment. Therefore, the development of targeting tools that facilitate the rapid, specific, and direct imaging of thrombi using molecular imaging is highly sought after. One potential molecular target is FXIIa (factor XIIa), which initiates the intrinsic coagulation pathway but also activates the kallikrein-kinin system, thereby initiating coagulation and inflammatory/immune responses. As FXII (factor XII) is dispensable for normal hemostasis, its activated form (FXIIa) represents an ideal molecular target for diagnostic and therapeutic approaches, the latter combining diagnosis/identification of thrombi and effective antithrombotic therapy.
We conjugated an FXIIa-specific antibody, 3F7, to a near-infrared (NIR) fluorophore and demonstrated binding to FeCl-induced carotid thrombosis with 3-dimensional fluorescence emission computed tomography/computed tomography and 2-dimensional fluorescence imaging. We further demonstrated ex vivo imaging of thromboplastin-induced pulmonary embolism and detection of FXIIa in human thrombi produced in vitro.
We demonstrated imaging of carotid thrombosis by fluorescence emission computed tomography/computed tomography and measured a significant fold increase in signal between healthy and control vessels from mice injected with 3F7-NIR compared with mice injected with nontargeted probe (=0.002) ex vivo. In a model of pulmonary embolism, we measured increased NIR signal in lungs from mice injected with 3F7-NIR compared with mice injected with nontargeted probe (=0.0008) and healthy lungs from mice injected with 3F7-NIR (=0.021).
Overall, we demonstrate that FXIIa targeting is highly suitable for the specific detection of venous and arterial thrombi. This approach will allow direct, specific, and early imaging of thrombosis in preclinical imaging modalities and may facilitate monitoring of antithrombotic treatment in vivo.
目前，血栓栓塞性疾病的临床影像学检查通常依赖于对血栓的间接检测，这可能会延迟诊断，并最终导致有益的、潜在的救生治疗的实施。因此，开发能够利用分子影像学快速、特异性、直接地对血栓进行成像的靶向工具是非常需要的。一个潜在的分子靶标是 FXIIa（因子 XIIa），它启动内源性凝血途径，但也激活激肽释放酶-激肽系统，从而启动凝血和炎症/免疫反应。由于 FXII（因子 XII）对于正常止血是可有可无的，其激活形式（FXIIa）代表了诊断和治疗方法的理想分子靶标，后者将血栓的诊断/识别与有效的抗血栓治疗相结合。
我们将一种 FXIIa 特异性抗体 3F7 与近红外（NIR）荧光团偶联，并通过三维荧光发射计算机断层扫描/计算机断层扫描和二维荧光成像证明了其与 FeCl 诱导的颈动脉血栓的结合。我们进一步证明了在组织因子诱导的肺栓塞的体外成像和对体外产生的人血栓中 FXIIa 的检测。
我们通过荧光发射计算机断层扫描/计算机断层扫描证明了颈动脉血栓的成像，并在注射了 3F7-NIR 的小鼠与注射了非靶向探针的小鼠（=0.002）之间测量了健康和对照血管之间信号的显著倍数增加，而在肺栓塞模型中，我们测量了与注射非靶向探针的小鼠相比，注射 3F7-NIR 的小鼠的 NIR 信号增加（=0.0008）和注射 3F7-NIR 的健康小鼠的 NIR 信号增加（=0.021）。
总的来说，我们证明了 FXIIa 靶向非常适合于静脉和动脉血栓的特异性检测。这种方法将允许在临床前成像模式中直接、特异性和早期地对血栓进行成像，并可能有助于在体内监测抗血栓治疗。
