From the Department of Pharmacology (R.A., M.H.), University of Michigan, Ann Arbor.
Department of Internal Medicine, Division of Cardiovascular Medicine(M.H.), University of Michigan, Ann Arbor.
Arterioscler Thromb Vasc Biol. 2019 Sep;39(9):1817-1830. doi: 10.1161/ATVBAHA.119.312848. Epub 2019 Jul 25.
Microvascular thrombosis is the hallmark pathology of thrombotic thrombocytopenic purpura (TTP), a rare life-threatening disease. Neurological dysfunction is present in over 90% of patients with TTP, and TTP can cause long-lasting neurological damage or death. However, the pathophysiology of microvascular thrombosis in the brain is not well studied to date. Here, we investigate the formation and resolution of thrombosis in pial microvessels. Approach and Results: Using a cranial intravital microscopy in well-established mouse models of congenital TTP induced by infusion of recombinant VWF (von Willebrand factor), we found that soluble VWF, at high concentration, adheres to the endothelium of the vessel wall, self-associates, and initiates platelet adhesion resulting in the formation of pial microvascular thrombosis in ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) mice. Importantly, VWF-mediated pial microvascular thrombosis occurred without vascular injury to the brain, and thrombi consisted of resting platelets adhered onto ultra-large VWF without fibrin in the brain in rVWF (recombinant VWF) challenged ADAMTS13 mice. Prophylactic treatment with recombinant ADAMTS13 (BAX930) effectively prevented the onset of the VWF-mediated microvascular thrombosis and therapeutic treatment with BAX930 acutely resolved the preexisting or growing thrombi in the brain of ADAMTS13 mice after rVWF challenge. The absence of platelet activation and fibrin formation within VWF-mediated thrombi and efficacy of BAX930 was confirmed with an endothelial-driven VWF-mediated microvascular thrombosis model in mice.
Our results provide important insight into the initiation and development of microvascular thrombi in mouse models that mimics TTP and indicate that rADAMTS13 could be an effective interventional therapy for microvascular thrombosis, the hallmark pathology in TTP.
微血管血栓形成是血栓性血小板减少性紫癜（TTP）的标志病理学特征，TTP 是一种罕见的危及生命的疾病。超过 90%的 TTP 患者存在神经功能障碍，TTP 可导致持久的神经损伤或死亡。然而，迄今为止，大脑微血管血栓形成的病理生理学尚未得到很好的研究。在这里，我们研究了脑皮微脉管中血栓的形成和溶解。
我们使用在重组 VWF（血管性血友病因子）输注诱导的先天性 TTP 建立的成熟小鼠模型中的颅颅活体显微镜，发现高浓度的可溶性 VWF 黏附于血管壁的内皮细胞，自身缔合，并引发血小板黏附，导致 ADAMTS13（一种金属蛋白酶与血小板反应蛋白 1 型基序，成员 13）小鼠的脑皮微血管血栓形成。重要的是，VWF 介导的脑皮微血管血栓形成没有发生脑血管损伤，血栓由附着在超大 VWF 上的静止血小板组成，在 rVWF（重组 VWF）挑战的 ADAMTS13 小鼠的脑中没有纤维蛋白。预防性使用重组 ADAMTS13（BAX930）可有效预防 VWF 介导的微血管血栓形成的发生，并且在 rVWF 挑战后，BAX930 的治疗性治疗可迅速溶解 ADAMTS13 小鼠脑中原发性或生长性血栓。通过在小鼠中内皮驱动的 VWF 介导的微血管血栓形成模型证实了 VWF 介导的血栓内没有血小板激活和纤维蛋白形成以及 BAX930 的疗效。
我们的研究结果为模拟 TTP 的小鼠模型中微血管血栓形成的起始和发展提供了重要的见解，并表明 rADAMTS13 可能是 TTP 标志性病理学微血管血栓形成的有效介入治疗方法。
