MOLECULAR MECHANISMS OF PLATELET THROMBOSIS UNDER FLOW

在美国，每年约有50%的疾病死亡是由 由血栓引起，主要由血小板组成，冠状动脉或 脑动脉虽然组织纤溶酶原激活剂tPA和 链激酶可用于恢复急性闭塞 冠状动脉，目前可用的预防剂（例如，阿司匹林 和噻氯匹定）在预防 心脏或大脑中动脉血栓的发展或复发。在 为了改善动脉血栓性疾病的治疗， 血小板血栓的诱导和控制机制 必须更好地理解形成。模型系统能够遵循 实时剪切应力诱导的直接血小板活化和聚集， 以及血小板-内皮下粘附和随后的聚集 在流动下，对于这种类型的研究特别有用。使用 人体血液成分和流动条件更接近于 在正常和病理动脉中体内遇到的那些将 改善前瞻性抗动脉血栓形成的体外评价 物质.我们建议利用我们现有的实时流模型， 暴露的内皮下研究： 细胞衍生的异常大的血管性血友病因子（vWF）多聚体， 人纤维胶原I型（其在动脉粥样硬化中占主导地位 内皮下）和人VI型胶原蛋白（另一种vWF结合胶原蛋白）， 以及由此产生的对血小板粘附的影响; 血栓形成对血小板释放的vWF的胶原I和VI的影响; tPA介导的vWF蛋白水解对血小板血栓形成的影响。我们将 还构建了血小板血栓形成的实时流动模型，包括 内皮细胞，为了更接近地模拟病理学 发生在体内的事件。这些流动模型将使我们能够 分析：内皮下暴露，vWF介导的血小板-内皮下 粘附和随后的聚集， 包括周围的内皮细胞;直接剪切应力诱导的vWF- 介导的血小板聚集在收缩的动脉模型下， 在存在完整内皮的情况下的病理性血流状况;以及 在这些血流模型中对vWF介导事件的调节作用 内皮细胞产物（前列环素，组织纤溶酶原激活剂， 一氧化氮或活性外腺苷二磷酸酶）。

About 50% of all deaths from illness in the United States each year are caused by thrombi, predominantly composed of platelets, in coronary or cerebral arteries. Although tissue plasminogen activator tPA and streptokinase have been useful in restoring blood flow in acutely occluded coronary arteries, presently available prophylactic agents (e.g., aspirin and ticlopidine) are only moderately effective in preventing the development or recurrence of arterial thrombi in the heart or brain. In order to improve the therapy of arterial thrombotic disorders, basic mechanisms involved in the induction and control of platelet thrombus formation must be better understood. Model systems capable of following in real-time shear stress-induced direct platelet activation and aggregation, as well as platelet-subendothelial adhesion and subsequent aggregation under flow, would be especially useful for this type of study. The use of human blood components and flowing conditions more closely analogous to those encountered in vivo in normal and pathological arteries would improve the in vitro evaluation of prospective anti-arterial thrombotic substances. We propose to utilize our existing real-time flow model of exposed subendothelium for the study of: the interaction of endothelial cell-derived unusually large von Willebrand factor (vWF) multimers with human fibrillar collagen type I (which predominates in atherosclerotic subendothelium) and human collagen type VI (another vWF-binding collagen), and the resulting effects on platelet adhesion; the contribution to thrombosis on collagens I and VI of vWF released from platelets; and the effects on platelet thrombosis of tPA-mediated vWF proteolysis. We will also construct real-time flow models of platelet thrombosis that include endothelial cells and, in order to simulate more closely pathological events that occur in vivo. These latter flow models will enable us to analyze: subendothelial exposure, vWF-mediated platelet-subendothelial adhesion, and subsequent aggregation in a model of vascular injury that includes surrounding endothelial cells; direct shear stress-induced vWF- mediated platelet aggregation in a model of constricted arteries under pathological flow conditions in the presence of intact endothelium; and the modulating effects on vWF-mediated events in these flow models of endothelial cell products (prostacyclin, tissue plasminogen activator, nitric oxide or activity ecto-adenosine diphosphatase).