Developing a multiscale understanding of biophysical processes in sickle cell disease

项目摘要 在这次更新中，我们试图了解镰状细胞病（SCD）异质性的起源， 在从分子到临床的每一个尺度上，它是临床管理和治疗的主要障碍。 开发新的疗法。此外，治疗往往会增加异质性，一些患者会对 对治疗反应强烈而其他人则反应迟钝。我们的中心假设是异质性起源于 镰状血红蛋白（HbS）自组装的细胞内动力学，转化为异质群体， 红细胞，其驱动全血中的强非牛顿流体行为和体循环的改变 其促成病理学，例如内皮损伤、血管闭塞、动脉瘤和中风。因此， 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 SCD病理生理学中多尺度生物物理过程背景下的异质性。在这项工作中，我们将 为SCD病理生理学建立一个生物物理学框架，从分子到体循环， 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， 异质性具体而言，我们将：（1）开发HbS聚合的定量框架， 准确地预测自组装的动力学;（2）定义分布之间的联系， 红细胞群体中HbS聚合物和机械特性;（3）了解细胞如何 异质性驱动非牛顿血液流变学和体循环中的改变的流动。的 这项更新工作建立在我们过去3年资助期间取得的关键概念进展基础上：HbS自我- 组装动力学以前被低估了至少一个数量级; HbS聚合物是 有限氧张力下红细胞中的不均匀分布;镰状血中的速度曲线显示出强的 非牛顿效应; SCD患者的血流在整个循环中发生改变，壁异常大 相对于健康血液的剪切应力。这项工作还利用了我们拥有的一套独特的工具， 在过去3年的资金开发：最高的时空分辨率测量的单一HbS 迄今为止的纤维组装;第一个能够定量大量单个RBC中HbS聚合物的平台 在定义明确的氧张力下;一个能够量化大群体粘弹性的平台 红细胞在明确定义的氧张力下的速度场;在流动的血液中定量亚微米速度场的能力， 生理红细胞压积;一个在生理氧梯度内量化镰状血流的平台。基础上 这些工具和见解，这项更新工作将开发和验证一个多尺度模型，描述如何 异质性从分子水平传播到细胞水平再到系统水平，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.