Millions of people worldwide are afflicted with sickle cell disease (SCD), a hereditary blood disease caused by a mutation of the ?-hemoglobin gene. Once thought to be simply due to increased rigidity of sickle red cells, SCD pathophysiology is now known to involve numerous cellular interactions among sickle red cells, white cells, platelets, reticulocytes (immature red cells), endothelial cells, and soluble factors (e.g. cytokines, coagulation factors, etc). Each of these pathologic interactions then contributes to microvascular occlusion, or vaso-occlusion, hemolysis (increased red destruction), and endothelial dysfunction. These key findings were primarily observed using in vivo animal models, which provide physiologically relevant but ultimately qualitative data. As SCD cellular interactions are inherently biophysical in nature, involving pathologic alterations in cell deformability and cell adhesion under hemodynamic conditions, quantitative methods are needed to fully understand the underlying mechanisms of these phenomena. Moreover, due to lack of sufficient technology, the relative contribution of each of these specific interactions on vaso-occlusion, hemolysis, and endothelial dysfunction are unknown. To that end, we have recently reported a novel """"""""endothelialized"""""""" microfluidic in vitro model of the microvasculature that recapitulates and integrates this ensemble of pathophysiological processes at the physiologically relevant microvascular (<30 ?m) size scale (Tsai et al, JCI, 2012). This """"""""microvasculature-on-a-chip"""""""" is ideally suited for the systematic and quantitative biophysical analyses of sickle cell vaso-occlusion, hemolysis, and endothelial dysfunction. For this work, we will further develop and optimize our microvasculature-on-a-chip microfluidic system to test our general hypothesis that in SCD, specific cellular interactions have differential effects on vaso-occlusion, hemolysis and endothelial dysfunction, and these contributions will change under different conditions, (e.g., white blood cell count, hemodynamics, anatomic site, on therapy, etc.). Specifically, we will first further optimize and build upon our system to enable the simultaneous testing of multiple conditions including concentrations of specific blood cell subpopulations, pharmacologic agents, wall shear stress, endothelial cell type, and oxygen tension, a major effector of sickle cell vaso-occlusion;this will achieve the high-throughput efficiency required to obtain the large amounts of data we need to extract from each experiment. We will then quantify the contributions of these cellular interactions under a variety of conditions to determine which dominate, and are therefore the most clinically relevant targets. Finally, we will apply varying dosages of standard and novel therapeutic agents to quantify their effects on those specific cellular interactions and to establish our microfluidic device as a viable drug discovery system for SCD. Overall, these studies will create a parameter space for the multitude of cell interactions in SCD and provide a quantitative framework for clinical hematologists to generate hypotheses and rationally design clinical trials for future SCD therapeutics.

Public Health Relevance

Sickle cell disease is a life-threatening genetic blood disorder that is characterized by episodic plugging of blood vessels throughout the body due to numerous complex blood cell interactions that are poorly understood. Using microfluidic technology, we have designed a microvasculature-on-a-chip to quantitatively and systematically study these cell interactions. In addition to being a research enabling device, this microfluidic system will also be used to test new sickle cell drugs and to potentially predict and diagnose acute and chronic complications.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL121264-01
Application #
8614121
Study Section
Instrumentation and Systems Development Study Section (ISD)
Program Officer
Hanspal, Manjit
Project Start
2014-01-01
Project End
2018-12-31
Budget Start
2014-01-01
Budget End
2014-12-31
Support Year
1
Fiscal Year
2014
Total Cost
$361,190
Indirect Cost
$129,658
Name
Emory University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
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Qiu, Yongzhi; Ciciliano, Jordan; Myers, David R et al. (2015) Platelets and physics: How platelets ""feel"" and respond to their mechanical microenvironment. Blood Rev 29:377-86
Mannino, Robert G; Myers, David R; Ahn, Byungwook et al. (2015) ""Do-it-yourself in vitro vasculature that recapitulates in vivo geometries for investigating endothelial-blood cell interactions"". Sci Rep 5:12401
Sakurai, Yumiko; Fitch-Tewfik, Jennifer L; Qiu, Yongzhi et al. (2015) Platelet geometry sensing spatially regulates α-granule secretion to enable matrix self-deposition. Blood 126:531-8
McGann, Patrick T; Tyburski, Erika A; de Oliveira, Vysolela et al. (2015) An accurate and inexpensive color-based assay for detecting severe anemia in a limited-resource setting. Am J Hematol 90:1122-7
Kee, Matthew F; Myers, David R; Sakurai, Yumiko et al. (2015) Platelet mechanosensing of collagen matrices. PLoS One 10:e0126624
Qiu, Yongzhi; Brown, Ashley C; Myers, David R et al. (2014) Platelet mechanosensing of substrate stiffness during clot formation mediates adhesion, spreading, and activation. Proc Natl Acad Sci U S A 111:14430-5
Brown, Ashley C; Stabenfeldt, Sarah E; Ahn, Byungwook et al. (2014) Ultrasoft microgels displaying emergent platelet-like behaviours. Nat Mater 13:1108-14

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