Model of Platelet Adhesion and Thrombus Formation

描述(申请人提供)：血小板与血管损伤部位的黏附不仅是防止过度出血(止血)的关键事件，而且在动脉粥样硬化斑块破裂后形成富含血小板的血栓(血栓)中也是关键事件，动脉粥样硬化斑块破裂是心脏病发作和中风的主要原因。在后一种情况下，阻止血小板介导的凝块形成的药物的开发往往因为无法预测止血可能受到损害的程度而受到阻碍。不幸的是，没有足够的计算模型可以潜在地帮助临床医生基于直接的细胞和分子信息来预测哪些患者可能有出血或急性血栓事件的风险。部分问题可能是由于无法研究人体内血小板血栓的形成。尽管如此，有证据表明，血小板最初黏附于受损血管壁的能力是由两种不同的血小板黏附受体协同作用控制的：1)血小板糖蛋白Ibα(GPIb1)，由于与表面固定的von Willebrand因子(VWF)快速形成和解离，支持血小板移位；2)整合素1221，支持血小板与暴露的胶原蛋白牢固黏附。第三种血小板受体1IIb23与血浆纤维蛋白原结合，对调节血小板：促进血栓生长和稳定的血小板相互作用至关重要。在这个项目中，我们建议在体外和体内的血小板黏附模型的基础上，扩展我们对剪切流中血小板流体动力学和受体介导的聚集的成功的多尺度模拟，以考虑多细胞血栓的起始、生长和破裂的过程。重要的是，我们可以使用Diacovo实验室开发的独特而强大的动物模型来观察生理相关条件下(即体内)人类血小板介导的血栓形成，这将用于验证和完善计算模型。一旦开发出来，多尺度血小板黏附模型将被应用于预测止血缺陷的临床观察，例如von Willebrand病(VWD)，这是人类最常见的遗传性出血疾病。由此产生的模拟还将为加入血小板激活所需的额外受体：配体相互作用提供一个严格的框架，如GPVI：胶原、P2Y12：ADP和PAR1：凝血酶。这将使我们能够应用我们的模型来预测与应用抗血小板药物相关的可能的有害后果，这些药物用于防止血管病变患者的血栓形成。拟议的工作围绕三个具体目标组织：目标1：建立一个多尺度的血小板黏附和血栓启动模型，其中包括GPIb1：VWF、1221：胶原和1IIb23：纤维蛋白原相互作用。目的2：血栓稳定性和血栓破裂形成的多尺度模型。目的3：基于来自体外和体内研究的分子输入参数预测临床出血表型。 公共卫生相关性： 目前缺乏基于分子和细胞特性的止血(损伤后止血)和血栓形成(血管病理性闭塞)的预测模型。我们建议开发一个多尺度的计算机模拟，并通过一个独特的实验模型进行验证，在这个模型中，可以在转基因小鼠的真实活体环境中观察到人的血小板。该模拟将首先应用于遗传性出血性疾病的临床研究和诊断，并在未来能够预测使用阿司匹林和Plavix等抗凝剂治疗的患者的表型。

DESCRIPTION (provided by applicant): Platelets adhesion to sites of vascular injury is a key event not only in the prevention of excessive bleeding (hemostasis) but also in the formation of platelet-rich clots (thrombi) in response to atherosclerotic plaque rupture, which is a leading cause of heart attacks and stroke. In the latter case, the development of drugs that prevent platelet-mediated clot formation are often hampered by an inability to predict the extent to which hemostasis may be impaired. Unfortunately, no adequate computational model exists that could potentially aid clinicians in predicting which patients may be at risk for bleeding or acute thrombotic events based on direct cellular and molecular information. Part of the problem may result from an inability to study human platelet thrombus formation in vivo. That said, there is evidence demonstrating that the ability of platelets to initially stick to the injured vessel wall is controlled by the synergistic action of two distinct platelet adhesion receptors: 1) Platelet glycoprotein Ib alpha (GPIb1) that supports platelet translocation due to rapid rates of bond formation and dissociation with surface-immobilized von Willebrand factor (VWF), and 2) the integrin 1221 that supports firm adhesion of platelets to exposed collagen. A third platelet receptor, 1IIb23, binds to plasma fibrinogen and is critical for mediating platelet: platelet interactions that contribute to thrombus growth and stability. In this project, we propose to extend our successful multiscale simulation of platelet hydrodynamics and receptor-mediated aggregation in shear flow to consider the processes of multicellular thrombus initiation, growth, and rupture based on in vitro and in vivo models of platelet adhesion. Importantly, we have access to unique and powerful animal models developed by the Diacovo lab to observe human platelet-mediated thrombus formation under physiologically relevant conditions (i.e. in vivo), which will be used to validate and refine the computational model. Once developed, the multiscale platelet adhesion model will be applied to the prediction of clinical observations of defects in hemostasis such as von Willebrand disease (VWD), the most common inheritable bleeding disorder in humans. The resulting simulation will also provide a rigorous framework for incorporation of additional receptor: ligand interactions required for platelet activation such as GPVI: collagen, P2Y12:ADP, and PAR1:thrombin. This will enable us to apply our model to predicting possible deleterious consequences associated with the administration of antiplatelet drugs used to prevent thrombus formation in patients with diseased blood vessels. The proposed work is organized around three specific aims: Aim 1: Development of a multiscale model of platelet adhesion and thrombus initiation, incorporating GPIb1:VWF, 1221:collagen, and 1IIb23:fibrinogen interactions. Aim 2: Multiscale modeling of thrombus stability and rupture with embolus formation. Aim 3: Prediction of clinical bleeding phenotype based on molecular input parameters from in vitro and in vivo studies. PUBLIC HEALTH RELEVANCE: A predictive model of hemostasis (cessation of blood loss following injury) and thrombosis (pathological occlusion of blood vessels) based on molecular and cellular properties is currently lacking. We propose to develop a multiscale computer simulation that is validated with a unique experimental model in which human platelets can be observed in the realistic in vivo setting of a genetically modified mouse. The simulation will be first applied to the clinical investigation and diagnosis of hereditary bleeding disorders, and in the future will enable phenotype prediction of patients treated with anticoagulants such as aspirin and Plavix.