Developing a multiscale understanding of biophysical processes in sickle cell disease

项目总结 在这次更新中，我们试图了解镰状细胞病(Scd)的异质性的起源，这是存在的。 在从分子到临床的各个层面上，它是临床管理和 开发新的治疗方法。此外，治疗往往会增加异质性，一些患者会做出反应。 对治疗反应强烈，其他人反应迟钝。我们的中心假设是异质性起源于 镰刀状血红蛋白(HBS)自组装的细胞内动力学研究 红细胞，驱动全血中强烈的非牛顿流体行为和体循环改变 这会导致内皮损伤、血管闭塞、动脉瘤和中风等病理变化。因此，能够 指导治疗干预和开发新疗法最终受到我们有限的理解的阻碍 在SCD病理生理学多尺度生物物理过程的背景下的异质性。在这项工作中，我们将 为SCD病理生理学开发一个从分子到体循环的生物物理框架， 这在每个尺度上都得到了实验验证，这使我们能够预测多尺度的影响 异质性。具体地说，我们将：(1)开发HBS聚合的量化框架， 准确地预测了自组装的动力学；(2)定义了自组装的分布之间的联系 红细胞群体中的HBS聚合物和机械性能；(3)了解细胞 异质性导致非牛顿血液流变性和体循环中流动的改变。这个 此次续订的工作建立在我们过去3年资助期间取得的关键概念进展的基础上：HBS Self- 组装动力学以前被低估了至少一个数量级；HBS聚合物 在有限氧分压下，红细胞呈不均匀分布；镰刀状血中的速度曲线显示很强 非牛顿效应；SCD患者的血流在整个循环中发生改变，并伴有异常的大管壁 相对健康血液的切应力。这项工作还利用了我们拥有的一套独特的、使人信服的工具 在过去三年的资助中开发的：单个HBS的最高时空分辨率测量 迄今为止的纤维组装；第一个能够在大量单一红细胞中定量检测HBS聚合物的平台 在定义明确的氧分压下；能够量化大量人群的粘弹性特性的平台 在明确定义的氧分压下的红细胞；量化流动的血液中亚微米速度场的能力 生理性红细胞压积；一个量化生理性氧梯度内镰状血流量的平台。在基础上建设 这些工具和见解，此次更新工作将开发和验证一个描述如何 异质性从分子到细胞再到系统，我们将开发实验工具 可用于临床管理和治疗开发。

PROJECT SUMMARY In this renewal, we seek to understand the origin of heterogeneity in sickle cell disease (SCD), which is present at every scale from molecules to the clinic, and is the major impediment to clinical management and the development of new therapies. Moreover, therapy often increases heterogeneity, with some patients responding strongly to therapy and others unresponsive. Our central hypothesis is that heterogeneity originates with intracellular kinetics of sickle hemoglobin (HbS) self-assembly that translates into heterogeneous populations of RBCs, which drive strong non-Newtonian fluid behavior in whole blood and alterations in the systemic circulation that precipitate pathologies such as endothelial injury, vaso-occlusion, aneurysm, and stroke. Thus, the ability to guide therapeutic intervention and to develop new therapies is ultimately hindered by our limited understanding of heterogeneity in the context of multiscale biophysical processes in SCD pathophysiology. In this work, we will develop a biophysical framework for SCD pathophysiology that spans from molecules to the systemic circulation, that is experimentally validated at every scale, and that allows us to predict the effects of multiscale heterogeneity. Specifically, we will: (1) Develop a quantitative framework for HbS polymerization that accurately predicts the kinetics of self-assembly; (2) Define the connection between the distribution of HbS polymer and mechanical properties among a population of RBCs; (3) Understand how cellular heterogeneity drives non-Newtonian blood rheology and altered flow in the systemic circulation. The work in this renewal builds on key conceptual advances made during our last 3 years of funding: HbS self- assembly kinetics have previously been underestimated by at least an order of magnitude; HbS polymer is heterogeneously distributed in RBCs at finite oxygen tension; velocity profiles in sickle blood demonstrate strong non-Newtonian effects; blood flow in SCD patients is altered throughout the circulation with aberrantly large wall shear stress relative to healthy blood. This work also leverages a unique and enabling set of tools that we have developed during the last 3 years of funding: the highest spatiotemporal resolution measurements of single HbS fiber assembly to-date; the first platform capable of quantifying HbS polymer in large populations of single RBCs under well-defined oxygen tension; a platform capable of quantifying viscoelastic properties of large populations of RBCs under well-defined oxygen tension; the ability to quantify submicron velocity fields in flowing blood at physiologic hematocrit; a platform to quantify sickle blood flow within physiologic oxygen gradients. Building on these tools and insights, this renewal work will develop and validate a multiscale model describing how heterogeneity propagates from the molecular to cellular to system levels, and we will develop experimental tools that can be used for clinical management and therapeutic development.