Whole blood viscosity and red blood cell adhesion: Potential biomarkers for targeted and curative therapies in sickle cell disease

Abstract

Sickle cell disease (SCD) is a recessive genetic blood disorder exhibiting abnormal blood rheology. Polymerization of sickle hemoglobin, due to a point mutation in the β-globin gene of hemoglobin, results in aberrantly adhesive and stiff red blood cells (RBCs). Hemolysis, abnormal RBC adhesion, and abnormal blood rheology together impair endothelial health in people with SCD, which leads to cumulative systemic complications. Here, we describe a microfluidic assay combined with a micro particle image velocimetry technique for the integrated in vitro assessment of whole blood viscosity (WBV) and RBC adhesion. We examined WBV and RBC adhesion to laminin (LN) in microscale flow in whole blood samples from 53 individuals with no hemoglobinopathies (HbAA, N = 10), hemoglobin SC disease (HbSC, N = 14), or homozygous SCD (HbSS, N = 29) with mean WBV of 4.50 cP, 4.08 cP, and 3.73 cP, respectively. We found that WBV correlated with RBC count and hematocrit in subjects with HbSC or HbSS. There was a significant inverse association between WBV and RBC adhesion under both normoxic and physiologically hypoxic (SpO 2 of 83%) tests, in which lower WBV associated with higher RBC adhesion to LN in subjects with HbSS. Low WBV has been found by others to associate with endothelial activation. Altered WBV and abnormal RBC adhesion may synergistically contribute to the endothelial damage and cumulative pathophysiology of SCD. These findings suggest that WBV and RBC adhesion may serve as clinically relevant biomarkers and endpoints in assessing emerging targeted and curative therapies in SCD. 1 | INTRODUCTION Sickle cell disease (SCD) is one of the most common inherited diseases in the world. 1,2 It is caused by a single-point mutation in the β-globin gene of hemoglobin. Sickle hemoglobin (HbS) polymerizes into long and stiff chains within the red blood cell (RBC) under low-oxygen conditions. 3,4 As a result, HbS-containing RBCs (sickle RBCs) become abnormally stiff and adherent (impairing microcirculatory blood flow), and fragile (resulting in hemolysis). Microvascular occlusion causes episodic and unpredictable vaso-occlusive events (VOE), pain, and Erdem Kucukal and Yuncheng Man contributed equally to this study.

Concurrent Assessment of Deformability and Adhesiveness of Sickle Red Blood Cells by Measuring Perfusion of an Adhesive Artificial Microvascular Network

“…Endpoints in current clinical trials evaluating new therapies for SCD typically include a combination of conventional hematologic parameters (e.g., total Hb, HbF level) and observed clinical complications (e.g., frequency of VOC). However, not every novel SCD therapy produces a change in conventional laboratory values (e.g., crizanlizumab, L-glutamine) (Kucukal et al, 2020;Lu et al, 2020). Additionally, monitoring for clinical complications (e.g., counting VOC over a period of time) is a slow and subjective process.…”

“…Finally, none of these common endpoints assess RBC functional properties, and hence cannot determine if the therapy has reduced the rheological abnormalities associated with SCD. Incorporating hemorheological biomarkers (RBC deformability and adhesiveness) into the clinical trial protocols alongside traditional clinical endpoints has the potential to provide a much more informative, mechanistic, and less subjective assessment of the effectiveness of novel SCD therapies (Kucukal et al, 2020;Lu et al, 2020).…”

Manual and Automatic Image Analysis Segmentation Methods for Blood Flow Studies in Microchannels

“…Consequently, further studies of the interaction between cells and particles and of the particle coating are required. Also to support the diagnosis, Kucukal et al [ 76 ] quantified the viscosity of preprocessing-free whole blood samples from the sickle cell disease patient population by using the micro-PIV technique for in vitro assessment of whole blood viscosity and RBC adhesion. More recently, Kucukal et al [ 77 ] have been able to measure the velocity of whole blood flow in a microchannel during coagulation using a simple optical setup and processing the images using PIV and wavelet-based optical flow velocimetry.…”

The Rheology of the Carotid Sinus: A Path Toward Bioinspired Intervention

“…The predictive relevance of blood viscosity in the literature has been suspected to be intrinsically germane to many disease processes. Types of problems where blood viscosity appears to play some pathophysiologic role include immunologic diseases ( Gudmundsson et al, 1993 ), inflammatory diseases ( Nwose, 2010 ), hemolytic anemias ( Bowers et al, 2013 , 2018 ; Kucukal et al, 2020 ), hearing loss ( Hildesheimer et al, 1990 ; Garcia Callejo et al, 2006 ), diabetes ( Nakanishi et al, 2004 ; Richards and Nwose, 2010 ; Schiapaccassa et al, 2019 ), renal disorders ( Jung et al, 2017 ), sickle cell disease ( Klug et al, 1974 ), and cerebrovascular disease ( Song et al, 2017 ). However, the association between cardiovascular disease and blood viscosity has been looked at most extensively throughout the literature ( Lowe, 1992 ; Kenyeres et al, 2008 ; Chevalier et al, 2013 ; Buyan et al, 2017 ; Celik et al, 2017 ; Peters et al, 2017 ; Sloop et al, 2018 ; Cekirdekci and Bugan, 2020 ; Engin and Guvenc, 2020 ).…”