Redefining Clinical Viscosity in Sickle Cell Diseaseby Leveraging Microfluidic Technologies

项目总结/摘要 镰状细胞病（SCD）是一种破坏性的单基因疾病，其中突变血红蛋白聚合 变成刚性纤维，导致红细胞（RBC）变硬，并且，典型地，增加血液粘度， 血管闭塞的病理过程。血液粘度的概念在临床上很重要，因为医生 指导他们明智地使用输血，以避免“高粘滞”，但也受到临床 科学上过于简单化而非循证的输血指南。这种过于简化的观点 血液粘度的降低是有问题的，原因有几个。首先，指南忽视了血液粘度 取决于SCD中的血管大小、剪切率和氧张力（直接影响RBC硬度）， 血红蛋白（Hb）浓度。此外，在微循环中，SCD病理生理学 发生，血管的口径接近血细胞的大小，复杂的流体， 血液不能用其“体积”粘度来描述。最后，过去几十年的研究表明， SCD还涉及内皮功能障碍和异常粘附以及大量细胞-细胞相互作用 涉及网织红细胞、血小板和白细胞亚群，所有这些都进一步受到溶血性 副产物、凝血蛋白和炎性细胞因子。因此，这些因素的多因素相互作用 复杂的生物物理学和生物学特性协同作用以改变血液的“有效”粘度， 在微循环中。这些有助于SCD中的有效粘度的复杂过程不能被认为是有效的。 在体内动物模型中进行定量研究，并且没有现有的体外测定可以整合所有这些变量。 为此，对于这项MPI R 01赠款，伍德和林博士，谁都有广泛的和互补的 在微系统工程和实验血液学方面的专业知识，与肯普博士密切合作， 系统生物学家，将采用多学科的实验和计算方法来开发一种体外 包含所有相关物理、生物和生化变量的脉管系统模型， 有助于增加有效血液粘度，并因此导致SCD中的血管闭塞。的大量数据 然后将通过计算和统计建模来构建一个 全面了解SCD血管闭塞背景下的有效血液粘度。成功 该项目的完成还将作为一个分析平台，最终导致患者特异性 输血方案符合每个患者的个体血液学特征。此外，方法和 这些方法将为SCD的新治疗策略的开发奠定基础。

Project Summary/Abstract Sickle cell disease (SCD) is a devastating monogenic disease in which mutant hemoglobin polymerizes into rigid fibers leading to red cell (RBC) stiffening, and, canonically, to increased blood viscosity and to the pathologic process of vaso-occlusion. The concept of blood viscosity is clinically important, as physicians are instructed to use blood transfusions judiciously to avoid “hyperviscosity” but are also hampered by clinical transfusion guidelines that are scientifically oversimplified and not evidence-based. This overly simplified view of blood viscosity is problematic for several reasons. First, the guidelines overlook the reality that blood viscosity depends on blood vessel size, shear rate, and oxygen tension (which directly affects RBC stiffness) in SCD, in addition to hemoglobin (Hb) concentrations. Furthermore, in the microcirculation, where SCD pathophysiology takes place and the caliber of the blood vessel approaches the size of the blood cells, a complex fluid such as blood cannot be described by its “bulk” viscosity. Finally, the last several decades of research have revealed that SCD also involves endothelial dysfunction and aberrant adhesion and a multitude of cell-cell interactions involving reticulocytes, platelets, and leukocyte subpopulations, all of which are further modulated by hemolytic byproducts, coagulation proteins, and inflammatory cytokines. Therefore, the multifactorial interactions of these complex biophysical and biological characteristics synergize to alter the “effective” viscosity of blood, especially in the microcirculation. These complex processes that contribute to effective viscosity in SCD cannot be quantitatively studied in in vivo animal models, and no existing in vitro assays can integrate all of these variables. To that end, for this MPI R01 grant, Drs. Wood and Lam, who both have extensive and complementary expertise in microsystems engineering and experimental hematology, in close collaboration with Dr. Kemp, a systems biologist, will apply a multi-disciplinary experimental and computational approach to develop an in vitro model of the vasculature that incorporates all of the relevant physical, biological, and biochemical variables that contribute to increased effective blood viscosity and therefore, vaso-occlusion in SCD. The vast amounts of data generated by our experiments will then be computationally and statistically modeled to construct a comprehensive understanding of effective blood viscosity in the context of SCD vaso-occlusion. Successful completion of this project will also serve as an analytical platform that will ultimately lead to patient-specific transfusion regimens catered towards each patient’s individual hematologic profile. Moreover, the approach and methods developed here will be the basis to developing new therapeutic strategies for SCD.