Mechanisms of mechano-chemical rupture of blood clots and thrombi

机械力-化学作用下血栓破裂的机制 普拉尚特湾约翰·普罗希特放大图片作者：John W. Weisel 该提案的目的是探索和了解血液凝块和血栓的断裂韧性，从而 为危及生命的血栓栓塞提供了机制基础。一系列实验， 理论建模和计算机模拟将揭示机械应力（由于血液流动）在 与酶裂解的协同作用诱导从分子到连续尺度的结构损伤， 血栓栓塞的倾向。具体目标是：（1）测量和建模骨折 纤维蛋白凝胶在准静态条件下的韧性，（2）研究速率依赖性耗散效应， 纤维蛋白凝胶的韧性，和（3）研究血细胞，血栓前血液成分， 和血凝块破裂时的纤维蛋白溶解。在特定目标（SA）1中，我们将测量纤维蛋白凝块的韧性 和纳米尺度断裂提供了结构基础。在SA 2中，我们将深入研究 纤维蛋白凝胶断裂的热力学和速率依赖性，包括流体流过孔隙和流体 拖动纤维蛋白纤维，以捕捉能量耗散如何增加韧性。在平移SA 3中，我们将 研究血小板、红细胞和中性粒细胞对生理相关凝块韧性的影响 在不存在和存在生理纤维蛋白溶解激活剂（tPA）的情况下。我们还将研究 静脉血栓栓塞症患者的血液制成的凝块，以探讨（促）血栓形成的作用 血液成分的改变对凝块机械稳定性的影响。我们的初步研究表明，i）韧性 的交联纤维蛋白凝胶是在那些合成水凝胶的范围内，ii）tPA添加到裂纹尖端 降低了裂纹生长的载荷，iii）纤维在裂纹尖端沿着拉伸方向排列和断裂， 和iv）裂纹扩展由共价键和非共价键的断裂引起。我们还开发了V） 动态力光谱学在计算机中使用拉伸机械测试纤维蛋白纤维和纤维蛋白网络 模拟和vi）原子应力方法，以使用来自模拟的输出来映射应力-应变场。 我们将使用可溶胀生物聚合物水凝胶的连续和有限元模型， 纤维蛋白分子被迫展开的模型。我们将采用多尺度计算建模， 纤维蛋白纤维原子结构的分子动力学模拟和纤维蛋白的Langevin模拟 图形处理器上的网络加速。拟议的实验涵盖了所有的 宏观拉伸试验、剪切流变仪、电子显微镜和共聚焦显微镜， 定量分析破裂血块的结构变化我们的实验和建模将帮助我们 了解血栓栓塞的机制，并将解决临床上的重要问题：为什么 血块结构/机械性能与心血管疾病之间是否存在强关联？的 新的知识也将有助于设计新的水凝胶基生物材料，目前处于最前沿， 机械、材料科学和生物工程的研究。

Mechanisms of mechano-chemical rupture of blood clots and thrombi Prashant K. Purohit, John L. Bassani, Valeri Barsegov and John W. Weisel The goal of this proposal is to explore and understand the fracture toughness of blood clots and thrombi, thus providing a mechanistic basis for life-threatening thrombotic embolization. A combination of experiments, theoretical modeling and computer simulations will reveal how mechanical stresses (due to blood flow) in synergy with enzymatic lysis induce structural damage from the molecular to continuum scales and affect the propensity of a clot to embolize. The specific aims of this proposal are: (1) Measure and model fracture toughness of fibrin gels in quasi-static conditions, (2) Investigate rate dependent dissipative effects on toughness of fibrin gels, and (3) Study the effects of blood cells, prothrombotic blood composition, and fibrinolysis on rupture of blood clots. In Specific Aim (SA) 1, we will measure toughness of fibrin clots and provide a structural basis for rupture at the micron and nanometer scales. In SA2, we will delve into the thermodynamics and rate-dependence of the fracture of fibrin gels, including fluid flow through pores and fluid drag on fibrin fibers to capture how energy dissipation increases toughness. In the translational SA3, we will investigate toughness of physiologically relevant clots with effects of platelets, red blood cells, and neutrophils in the absence and presence of the physiological fibrinolytic activator (tPA). We will also study the rupture of clots made from the blood of venous thromboembolism patients to explore the effects of (pro)thrombotic alterations of blood composition on clot mechanical stability. Our preliminary studies show that i) the toughness of cross-linked fibrin gels is in the range of those for synthetic hydrogels, ii) the addition of tPA to a crack tip reduces the loads for crack growth, iii) fibers are aligned and broken along the tensile direction at the crack tip, and iv) crack propagation results from the rupture of covalent and non-covalent bonds. We also developed v) dynamic force spectroscopy in silico to mechanically test fibrin fibers and fibrin networks using pulling simulations and vi) atomic stress approach to map the stress-strain fields using the output from simulations. We will use continuum and finite element models of swellable biopolymer hydrogels, and statistical mechanical models for the forced unfolding of fibrin molecules. We will employ multiscale computational modeling based on Molecular Dynamics simulations of atomic structures of fibrin fibers, and Langevin simulations of fibrin networks accelerated on Graphics Processing Units. The proposed experiments cover the whole gamut of macroscopic tensile tests, shear rheometry, electron microscopy and confocal microscopy to visualize and quantitate the structural alterations of ruptured blood clots. Our experiments and modeling will help us to understand the mechanisms of thrombotic embolization and will address the clinically important question: why is there a strong association between clot structure/mechanical properties and cardiovascular diseases? The new knowledge will also help to design new hydrogel-based biomaterials that are currently at the forefront of research in mechanics, materials science and bioengineering.