Search

Numerical simulation of blood flow is a challenging topic due to the multiphase nature of this biological fluid. The choice of a specific method among the ones available in literature is often motivated by the physical scale of interest. Single-phase approximation allows for lower computational time, but does not consider this multiphase nature. Cell-level simulation, on the other hand, requires high computational resources and is limited to small scales. This work proposes a scale-up approach for cell-level simulation of blood flow, in the framework of unresolved CFD-DEM technique. This method offers the possibility to simulate hundreds of thousands of particles with limited computational effort, but requires specific models for fluid-particle interactions. Regarding blood flow, drag and lift force acting on the red blood cells (RBCs) are responsible for several macroscopic blood characteristics. Despite several correlations available for drag and lift force acting on rigid particles, specific force models for the simulation of deformable particles compatible with RBCs physics are missing. This study employs data obtained from cell-level simulations to derive equations then used in unresolved simulation of RBCs. The strategy followed during the modeling phase is presented, together with the model verification and validation. This approach returns satisfying results when used to simulate blood flow in large-scale channels. Up to half a million RBCs are considered, and computational effort is reported to allow a comparison with other existing methods. Future perspectives include further improvement of the model, such as a deeper understanding of particle-particle interactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Several diseases like Sickle Cell Anemia, Thalassemia, Hereditary Spherocytosis, Malaria, and Micro-angiopathic Hemolytic Anemia can alter the normal shape of red blood cells (RBCs). The objective of this study is to gain insight into how a change in RBC deformability can affect blood heat transfer. The heat sink effect in a bifurcated vessel with two asymptotic cases (case 1: deformable and case 2: nondeformable RBCs) is being studied during hyperthermia treatment in a three-dimensional bifurcated vessel, whose wall is being subjected to constant heat flux boundary condition. Euler-Euler multiphase method along with the granular model and Kinetic theory is used to include the particle nature of RBCs during blood flow in the current model. To enhance the efficiency of the numerical model, user-defined functions (UDFs) are imported into the model from the C++ interface. The numerical model used is verified with the experimental results from (Carr and Tiruvaloor, 1989, "Enhancement of Heat Transfer in Red Cell Suspensions In Vitro Experiments," ASME J. Biomech. Eng., 111(2), pp. 152-156; Yeleswarapu et al. 1998, "The Flow of Blood in Tubes: Theory and Experiment," Mech. Res. Commun., 25(3), pp. 257-262). The results indicate that the deformability of RBCs can change both the flow dynamics and heat sink effect in a bifurcated vessel, which subsequently affects the efficacy and efficiency of the thermal ablation procedure. Both spatial and transient Nusselt numbers of blood flow with deformable RBCs are slightly higher compared to the one with nondeformable RBCs., (Copyright © 2024 by ASME.)

Background: A challenge for coaches and athletes is to find the best combination of exercises during training. Considering its favorable effects, HIIT has been very popular recently., Objective: The goal of this study was to investigate anthropometric features, performance, erythrocyte deformability, plasma viscosity (PV) and oxidative stress in response to acute and long-term (6 weeks) HIIT in adolescent basketball players., Methods: 22 sportsmen between the ages of 14-16 were included. Tabata protocol was applied to the HIIT group in addition to their routine training program 3 days/week, for 6 weeks. Erythrocyte deformability was determined using an ectacytometer (LORCA), PV with a rotational viscometer. Total oxidant status (TOS), total antioxidant status (TAS) were measured by kits., Results: HIIT for 6 weeks induced an improvement in performance tests and waist circumference. 6 weeks of HIIT resulted in a decrement, while the last exercise session yielded an increment in RBC deformability. PV and TOS of HIIT groups were decreased on the 6th week., Conclusions: Our results demonstrate that, HIIT in addition to the routine exercise program is beneficial for improving performance and blood fluidity as well as decreasing oxidative stress in basketball players. Therefore, HIIT seems as an efficient training strategy for highly-trained individuals.

In previous research, we observed that tubulin can be found in three fractions within erythrocytes, i.e., attached to the membrane, as a soluble fraction, or as part of a structure that can be sedimented by centrifugation. Given that its differential distribution within these fractions may alter several hemorheological properties, such as erythrocyte deformability, the present work studied how this distribution is in turn affected by Ca 2+ , another key player in the regulation of erythrocyte cytoskeleton stability. The effect of Ca 2+ on some hemorheological parameters was also assessed. The results showed that when Ca 2+ concentrations increased in the cell, whether by the addition of ionophore A23187, by specific plasma membrane Ca 2 + _ ATPase (PMCA) inhibition, or due to arterial hypertension, tubulin translocate to the membrane, erythrocyte deformability decreased, and phosphatidylserine exposure increased. Moreover, increased Ca 2+ was associated with an inverse correlation in the distribution of tubulin and spectrin, another important cytoskeleton protein. Based on these findings, we propose the existence of a mechanism of action through which higher Ca 2+ concentrations in erythrocytes trigger the migration of tubulin to the membrane, a phenomenon that results in alterations of rheological and molecular aspects of the membrane itself, as well as of the integrity of the cytoskeleton., (© 2023. The Author(s) under exclusive licence to University of Navarra.)

The mechanical properties of red blood cells (RBCs) play key roles in their biological functions in microcirculation. In particular, RBCs must deform significantly to travel through microcapillaries with sizes comparable with or even smaller than their own. Although the dynamics of RBCs in microcapillaries have received considerable attention, the effect of membrane viscoelasticity has been largely overlooked. In this work, we present a computational study based on the boundary integral method and thin-shell mechanics to examine how membrane viscoelasticity influences the dynamics of RBCs flowing through straight and constricted microcapillaries. Our results reveal that the cell with a viscoelastic membrane undergoes substantially different motion and deformation compared with results based on a purely elastic membrane model. Comparisons with experimental data also suggest the importance of accounting for membrane viscoelasticity to properly capture the transient dynamics of an RBC flowing through a microcapillary. Taken together, these findings demonstrate the significant effects of membrane viscoelasticity on RBC dynamics in different microcapillary environments. The computational framework also lays the groundwork for more accurate quantitative modeling of the mechanical response of RBCs in their mechanotransduction process in subsequent investigations., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Blood flow in the microcirculatory system is crucially affected by intrinsic red blood cell (RBC) properties, such as their deformability. In the smallest vessels of this network, RBCs adapt their shapes to the flow conditions. Although it is known that the age of RBCs modifies their physical properties, such as increased cytosol viscosity and altered viscoelastic membrane properties, the evolution of their shape-adapting abilities during senescence remains unclear. In this study, we investigated the effect of RBC properties on the microcapillary in vitro flow behavior and their characteristic shapes in microfluidic channels. For this, we fractioned RBCs from healthy donors according to their age. Moreover, the membranes of fresh RBCs were chemically rigidified using diamide to study the effect of isolated graded-membrane rigidity. Our results show that a fraction of stable, asymmetric, off-centered slipper-like cells at high velocities decreases with increasing age or diamide concentration. However, while old cells form an enhanced number of stable symmetric croissants at the channel centerline, this shape class is suppressed for purely rigidified cells with diamide. Our study provides further knowledge about the distinct effects of age-related changes of intrinsic cell properties on the single-cell flow behavior of RBCs in confined flows due to inter-cellular age-related cell heterogeneity.

The viscoelastic response of the red blood cells (RBCs) affected by hematological disorders become severely impaired by the altered biophysical and morphological properties. These include traits like reduced deformability, increased membrane viscosity, and change in cell shape, causing substantial changes in the overall hemodynamics. RBCs, by virtue of their highly elastic membrane and low bending rigidity, exhibit complex dynamics when exposed to cyclic, transient forces in the microcirculation. Here, we employ mesoscopic numerical simulations based on the dissipative particle dynamics (DPD) framework to explore the dynamics of healthy, schizont stage malaria-infected and type 2 diabetes mellitus affected RBCs subjected to external time-dependent loads. The paper focuses on the imposition and cessation of external forcing on the cells of two different typologies, saw-tooth cyclic wave loading and sudden loads in the form of creep and relaxation phenomena. The effects of varying the rate of stress and the applied stress magnitude were investigated. Our simulations disclosed unique shape transitions of the hysteresis curves at varied loading rates. A careful analysis reveals a critical threshold of half cycle time of the from wherein the deformation of all cells observed, healthy or otherwise, falls under the nearly reversible deformation regime displaying minimal energy dissipation. Finally, we also examined the individual effects of the different constitutive and geometric characteristics attributed to the pathological cells and observed interesting recovery dynamics of spherocytes and cells having high shear moduli. The distinguished deformation behaviour of healthy and diseased cells could establish external force as a valuable initial biomarker.

On-chip study of blood flow has emerged as a powerful tool to assess the contribution of each component of blood to its overall function. Blood has indeed many functions, from gas and nutrient transport to immune response and thermal regulation. Red blood cells play a central role therein, in particular through their specific mechanical properties, which directly influence pressure regulation, oxygen perfusion, or platelet and white cell segregation toward endothelial walls. As the bloom of in-vitro studies has led to the apparition of various storage and sample preparation protocols, we address the question of the robustness of the results involving cell mechanical behavior against this diversity. The effects of three conservation media (EDTA, citrate, and glucose-albumin-sodium-phosphate) and storage time on the red blood cell mechanical behavior are assessed under different flow conditions: cell deformability by ektacytometry, shape recovery of cells flowing out of a microfluidic constriction, and cell-flipping dynamics under shear flow. The impact of buffer solutions (phosphate-buffered saline and density-matched suspension using iodixanol/Optiprep) are also studied by investigating individual cell-flipping dynamics, relative viscosity of cell suspensions, and cell structuration under Poiseuille flow. Our results reveal that storing blood samples up to 7 days after withdrawal and suspending them in adequate density-matched buffer solutions has, in most experiments, a moderate effect on the overall mechanical response, with a possible rapid evolution in the first 3 days after sample collection., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

The drug-induced diverse response among patients is a severe problem for improving hemorheological character. However, there is no validated method for personalized therapy to the best of our knowledge. Here, we apply a gravity-driven deformability cytometry platform (GD-DCP) to profile the drug response of the red cell deformability (RCD) at the single-cell level using pentoxifylline (PTX) as a model drug, the effect of different concentrations of PTX (0, 2, 20, 200 μg mL -1 , the clinical dosage of PTX is 20 μg mL -1 ) on RCD in patients with cardiovascular disease was explored. Based on the GD-DCP, about 38 and 56% of the acute phase of acute myocardial infarction (AMI) patients in the acute phase and coronary heart disease (CHD) patients respond positively to PTX, respectively, indicating that PTX has a strong patient dependency on RCD. Moreover, RCD is observed to be significantly inversely correlated with the activation of membrane protein kinase C (PKC) as well as the concentration of Ca 2+ (both P < 0.001). The results of animal experiments show that the protective effects of PTX on myocardial ischemia rats have substantial individual variation, too. It is noted that the effect of PTX is highly consistent between RCD in vitro and in vivo outcomes (blood viscosity, myocardial injury, and electrocardiogram (ECG)) in the same rat. All these new findings suggest that the GD-DCP is a promising method that uses deformability in vitro as one of the important criteria in personalized medicine, and our study provides unique insight into the individual-dependent mechanisms of PTX for improving RCD., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Objectives: Validation of the measurement of erythrocyte deformability as a useful prognostic, rheological biomarker for patients with sickle cell disease (SCD)., Methods: The degree of reduced deformability was based on the value of the maximum elongation index (EI max ) of the deformability curve of an osmotic gradient ektacytometer. The performance of this technique was analytically and clinically validated by analysing 200 normal subjects and 100 patients with well-documented thalassemia's and Hb variants in relation to their clinical condition., Results: In this study, we show that EI max is a reproducible parameter with a small inter-individual coefficient of (Biological) variation (CV)=1.6% and a small intra-individual CV=3.5%. We demonstrate that loss of deformability correlates with the clinical condition and the various mutations underlying sickle cell disease and thalassemia. For SCD patients, a strongly reduced EI max with a cut-off =0.360 is a signal for future vaso-occlusive (VOC) events requiring hospitalisation with a specificity=85%, sensitivity=80%, PPV=81% and NPV=84% based on a ROC curve (AUC=0.89)., Conclusion: This study validated the clinical utility of EI max as a prognostic marker for future clinical problems in individual high-risk SCD patients. In addition, EI max may help to achieve an adequate personal transfusion policy for an optimal blood flow in anaemic patients with SCD., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Infection with the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and the associated coronavirus disease-19 (COVID-19) might affect red blood cells (RBC); possibly altering oxygen supply. However, investigations of cell morphology and RBC rheological parameters during a mild disease course are lacking and thus, the aim of the study. Fifty individuals with mild COVID-19 disease process were tested after the acute phase of SARS-CoV-2 infection (37males/13 females), and the data were compared to n = 42 healthy controls (30 males/12 females). Analysis of venous blood samples, taken at rest, revealed a higher percentage of permanently elongated RBC and membrane extensions in COVID-19 patients. Haematological parameters and haemoglobin concentration, MCH and MCV in particular, were highly altered in COVID-19. RBC deformability and deformability under an osmotic gradient were significantly reduced in COVID-19 patients. Higher RBC-NOS activation was not capable to at least in part counteract these reductions. Impaired RBC deformability might also be related to morphological changes and/or increased oxidative state. RBC aggregation index remained unaffected. However, higher shear rates were necessary to balance the aggregation-disaggregation in COVID-19 patients which might be, among others, related to morphological changes. The data suggest prolonged modifications of the RBC system even during a mild COVID-19 disease course., (© 2022 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Red blood cell (RBC) deformability is modulated by the phosphorylation status of the cytoskeletal proteins that regulate the interactions of integral transmembrane complexes. Proteomic studies have revealed that receptor-related signaling molecules and regulatory proteins involved in signaling cascades are present in RBCs. In this study, we investigated the roles of the cAMP signaling mechanism in modulating shear-induced RBC deformability and examined changes in the phosphorylation of the RBC proteome. We implemented the inhibitors of adenylyl cyclase (SQ22536), protein kinase A (H89), and phosphodiesterase (PDE) (pentoxifylline) to whole blood samples, applied 5 Pa shear stress (SS) for 300 s with a capillary tubing system, and evaluated RBC deformability using a LORRCA MaxSis. The inhibition of signaling molecules significantly deteriorated shear-induced RBC deformability (p < 0.05). Capillary SS slightly increased the phosphorylation of RBC cytoskeletal proteins. Tyrosine phosphorylation was significantly elevated by the modulation of the cAMP/PKA pathway (p < 0.05), while serine phosphorylation significantly decreased as a result of the inhibition of PDE (p < 0.05). AC is the core element of this signaling pathway, and PDE works as a negative feedback mechanism that could have potential roles in SS-induced RBC deformability. The cAMP/PKA pathway could regulate RBC deformability during capillary transit by triggering significant alterations in the phosphorylation state of RBCs.

In this study, the motion and deformation of a red blood cell in a Poiseuille flow through microvessels under the effect of a uniform transverse magnetic field is comprehensively investigated to get a better insight into blood hemorheology. The rheology of the RBC and the surrounding blood flow are examined numerically in two dimensions using a Finite Element Method. It is essential to know that the flow patterns of blood change in the presence of an RBC. The simulation results demonstrate that the magnetic field has significant influence on the flow stream and the behavior of the RBC, including the motion and the cells deformation.

Capillary blood vessels, the smallest vessels in the body, form an intricate network with constantly bifurcating, merging and winding vessels. Red blood cells (RBCs) must navigate through such complex microvascular networks in order to maintain tissue perfusion and oxygenation. Normal, healthy RBCs are extremely deformable and able to easily flow through narrow vessels. However, RBC deformability is reduced in many pathological conditions and during blood storage. The influence of reduced cell deformability on microvascular hemodynamics is not well established. Here we use a high-fidelity, 3D computational model of blood flow that retains exact geometric details of physiologically realistic microvascular networks, and deformation of every one of nearly a thousand RBCs flowing through the networks. We predict that reduced RBC deformability alters RBC trafficking with significant and heterogeneous changes in hematocrit. We quantify such changes along with RBC partitioning and lingering at vascular bifurcations, perfusion and vascular resistance, and wall shear stress. We elucidate the cellular-scale mechanisms that cause such changes. We show that such changes arise primarily due to the altered RBC dynamics at vascular bifurcations, as well as cross-stream migration. Less deformable cells tend to linger less at majority of bifurcations increasing the fraction of RBCs entering the higher flow branches. Changes in vascular resistance also seen to be heterogeneous and correlate with hematocrit changes. Furthermore, alteration in RBC dynamics is shown to cause localized changes in wall shear stress within vessels and near vascular bifurcations. Such heterogeneous and focal changes in hemodynamics may be the cause of morphological abnormalities in capillary vessel networks as observed in several diseases., (© 2022. The Author(s).)

Polycythemia vera (PV) is a Ph-negative myeloproliferative neoplasm (MPN) which is characterized by erythrocytosis and a high incidence of thrombotic complications, including stroke. The study aimed to evaluate red blood cell (RBC) morphodynamic properties in PV patients and their possible association with stroke. We enrolled 48 patients with PV in this cross-sectional study, 13 of which have a history of ischemic stroke. The control group consisted of 90 healthy subjects. RBC deformability and aggregation analysis were performed using a laser-assisted optical rotational red cell analyzer. The following parameters were calculated: aggregation amplitude (Amp), RBC rouleaux formation time constant (Tf), time of formation of three-dimensional aggregates (Ts), aggregation index (AI), rate of complete disaggregation (y-dis), and the maximal elongation of RBC (EImax). Statistical analysis was performed with the R programming language. There were significant differences in RBCs morphodynamics features between patients with PV and the control group. Lower EImax (0.47 (0.44; 0.51) vs. 0.51 (0.47; 0.54), p < 0.001) and γ-dis (100 (100; 140) vs. 140 (106; 188) s -1 , p < 0.001) along with higher amplitude (10.1 (8.6; 12.2) vs. 7.7 (6.6; 9.2), p < 0.001) was seen in patients with PV compared with control. A statistically significant difference between PV patients with and without stroke in aggregation amplitude was found ( p = 0.03). A logistic regression model for stroke was built based on RBC morphodynamics which performed reasonably well ( p = 0.01) . RBC alterations may be associated with overt cerebrovascular disease in PV, suggesting a possible link between erythrocyte morphodynamics and increased risk of stroke.

The viscoelastic properties of red blood cells (RBC) facilitate flexible shape change in response to extrinsic forces. Their viscoelasticity is intrinsically linked to physical properties of the cytosol, cytoskeleton, and membrane-all of which are highly sensitive to supraphysiological shear exposure. Given the need to minimise blood trauma within artificial organs, we observed RBC in supraphysiological shear through direct visualisation to gain understanding of processes leading to blood damage. Using a custom-built counter-rotating shear generator fit to a microscope, healthy red blood cells (RBC) were directly visualised during exposure to different levels of shear (10-60 Pa). To investigate RBC morphology in shear flow, we developed an image analysis method to quantify (a)symmetry of deforming ellipsoidal cells-following RBC identification and centroid detection, cell radius was determined for each angle around the circumference of the cell, and the resultant bimodal distribution (and thus RBC) was symmetrically compared. While traditional indices of RBC deformability (elongation index) remained unaltered in all shear conditions, following ~100 s of exposure to 60 Pa, the frequency of asymmetrical ellipses and RBC fragments/extracellular vesicles significantly increased. These findings indicate RBC structure is sensitive to shear history, where asymmetrical morphology may indicate sublethal blood damage in real-time shear flow., (© 2021. The Author(s).)

Employing natural cells as drug carriers has been a hotspot in recent years, attributing to their biocompatibility and inherent dynamic properties. In the earlier stage, cells were mainly used as vehicles by virtue of their lipid-delimited compartmentalized structures and native membrane proteins. The scope emphasis was 'what cell displays' instead of 'how cell changes'. More recently, the dynamic behaviours, such as changes in surface protein patterns, morphologies, polarities and in-situ generation of therapeutics, of natural cells have drawn more attention for developing advanced drug delivery systems by fully taking advantage of these processes. In this review, we revolve around the dynamic cellular transformation behaviours which facilitate targeted therapy. Cellular deformation in geometry shape, spitting smaller vesicles, activation of antigen present cells, polarization between distinct phenotypes, local production of therapeutics, and hybridization with synthetic materials are involved. Other than focusing on the traditional delivery of concrete cargoes, more functional 'handles' that are derived from the cells themselves are introduced, such as information exchange, cellular communication and interactions between cell and extracellular environment., Competing Interests: Declaration of Competing Interest Z.G. is a scientific cofounder of ZenCapsule and ZCapsule. The other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

Sickle cell disease, a genetic disorder affecting a sizeable global demographic, manifests in sickle red blood cells (sRBCs) with altered shape and biomechanics. sRBCs show heightened adhesive interactions with inflamed endothelium, triggering painful vascular occlusion events. Numerous studies employ microfluidic-assay-based monitoring tools to quantify characteristics of adhered sRBCs from high resolution channel images. The current image analysis workflow relies on detailed morphological characterization and cell counting by a specially trained worker. This is time and labor intensive, and prone to user bias artifacts. Here we establish a morphology based classification scheme to identify two naturally arising sRBC subpopulations-deformable and non-deformable sRBCs-utilizing novel visual markers that link to underlying cell biomechanical properties and hold promise for clinically relevant insights. We then set up a standardized, reproducible, and fully automated image analysis workflow designed to carry out this classification. This relies on a two part deep neural network architecture that works in tandem for segmentation of channel images and classification of adhered cells into subtypes. Network training utilized an extensive data set of images generated by the SCD BioChip, a microfluidic assay which injects clinical whole blood samples into protein-functionalized microchannels, mimicking physiological conditions in the microvasculature. Here we carried out the assay with the sub-endothelial protein laminin. The machine learning approach segmented the resulting channel images with 99.1±0.3% mean IoU on the validation set across 5 k-folds, classified detected sRBCs with 96.0±0.3% mean accuracy on the validation set across 5 k-folds, and matched trained personnel in overall characterization of whole channel images with R2 = 0.992, 0.987 and 0.834 for total, deformable and non-deformable sRBC counts respectively. Average analysis time per channel image was also improved by two orders of magnitude (∼ 2 minutes vs ∼ 2-3 hours) over manual characterization. Finally, the network results show an order of magnitude less variance in counts on repeat trials than humans. This kind of standardization is a prerequisite for the viability of any diagnostic technology, making our system suitable for affordable and high throughput disease monitoring., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: UAG and Case Western Reserve University have financial interests in BioChip Labs Inc. (Cleveland, Ohio). BioChip Labs Inc. offers commercial clinical microfluidic biomarker assays for inherited or acquired blood disorders. Financial interests include licensed intellectual property, stock ownership, research funding, employment, and consulting. UAG and Case Western Reserve University have financial interests in Xatek Inc. (Cleveland, Ohio). Xatek Inc. offers point-of-care global assays to evaluate the hemostatic process. Financial interests include licensed intellectual property and stock ownership. UAG and Case Western Reserve University have financial interests in Hemex Health Inc. (Portland, Oregon). Hemex Health Inc. offers point-of-care diagnostics for hemoglobin disorders, anemia, and malaria. Financial interests include licensed intellectual property, stock ownership, research funding, employment, and consulting. UAG has financial interests in DxNow Inc. (Gaithersburg, MD). DxNow Inc. offers microfluidic and bio-imaging technologies for in vitro fertilization, forensics, and diagnostics. Financial interests include licensed intellectual property and stock ownership. Competing interests of Case Western Reserve University employees are overseen and managed by the Conflict of Interests Committee according to a Conflict-of-Interest Management Plan. A patent application has been filed related to the methods discussed in this work.

We performed a detailed analysis of changes in the profiles of osmotic deformability using the method of gradient ektacytometry. Changes in all determinants that form the deformation properties of red blood cells in Wistar rats in the juvenile period and before puberty were determined. The dynamics of the formation of the rheological properties of the blood after birth is characterized by a wave-like change in the studied determinants. The changes are explained by adaptive reactions to extrauterine life as a result of hematopoiesis activation and the transition of the red bone marrow to a new level of functioning with the predominant replacement of physiological reticulocytosis in newborns with mature erythrocytes. The most critical period is from 10 days to 1 month after birth. Starting from the second month, the deformation parameters of erythrocytes are stabilized., (© 2021. Springer Science+Business Media, LLC, part of Springer Nature.)

Red blood cells (RBC) are constantly exposed to varying mechanical forces while traversing the cardiovascular system. Upon exposure to mechanical stimuli (e.g., shear stress), calcium enters the cell and prompts potassium-efflux. Efflux of potassium is accompanied by a loss of intracellular fluid; thus, the volume of RBC decreases proportionately (i.e., 'Gárdos effect'). The mechanical properties of the cell are subsequently impacted due to complex interactions between cytosolic viscosity (dependent on cell hydration), the surface-area-to-volume ratio, and other molecular processes. The dynamic effects of calcium on RBC mechanics are yet to be elucidated, although accumulating evidence suggests a vital role. The present study thus examined the effects of calcium on contemporary biomechanical properties of RBC in conjunction with high-precision geometrical analyses with exposure to shear. Mechanical stimulation of RBC was performed using a co-axial Couette shearing system to deform the cell membrane; intracellular signaling events were observed via fluorescent imaging. Calcium was introduced into RBC using ionophore A23187. Increased intracellular calcium significantly impaired RBC deformability; these impairments were mediated by a calcium-induced reduction of cell volume through the Gárdos channel. Extracellular calcium in the absence of the ionophore only had an effect under shear, not at stasis. Under low shear, the presence of extracellular calcium induced progressive lysis of a sub-population of RBC; all remaining RBC exhibited exceptional capacity to deform, implying preferential removal of potentially aged cells. Collectively, we provide evidence of the mechanism by which calcium acutely regulates RBC mechanical properties., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In order to have research on the deformation characteristics and mechanical properties of human red blood cells (RBCs), finite element models of RBC optical tweezers stretching and atomic force microscope (AFM) indentation were established. Non-linear elasticity of cell membrane was determined by using the neo-Hookean hyperelastic material model, and the deformation of RBC during stretching and indentation had been researched in ABAQUS, respectively. Considering the application of machine learning (ML) in material parameters identification, ML algorithm was combined with finite element (FE) method to identify the constitutive parameters. The material parameters were estimated according to the deformation characteristics of RBC obtained from the change of cell diameter with stretching force when RBC was stretched. The non-linear relationship between material parameter and RBC deformation was established by building a FE-model. The FE simulation of RBC stretching was used to construct the training set and the neural network trained by a large number of samples was used to predict the material parameter. With the predicted parameter, FE simulation of RBC under AFM indentation to explore the local deformation mechanism was completed.

Background: In blood banking practice, the storage duration is used as the primary criterion for inventory management, and usually, the packed red blood cells (PRBC) units are supplied primarily according to first-in-first-out (FIFO) principle. However, the actual functionality of individual PRBC units is mostly ignored. One of the main features of the RBCs not accounted for under this approach is the deformability of the red cells, i.e., their ability to affect the recipients' blood flow. The objective of the study was to analyze unit-to-unit variability in the deformability of PRBCs during their cold storage., Methods: RBC samples were obtained from twenty leukoreduced PRBC units, stored in SAGM. The deformability of cells was monitored from the day of donation throughout 42 days. RBC deformability was determined using the computerized cell flow-properties analyzer (CFA) based on cell elongation under a shear stress of 3.0 Pa, expressed by the elongation-ratio (ER). The image analysis determines the ER for each cell and provides the ER distribution in the population of 3000-6000 cells., Results: The deformability of freshly-collected RBCs exhibited marked variability already on the day of donation. We also found that the aging curve of PRBC deformability varies significantly among donors., Significance: The present study has demonstrated that storage duration is only one of the factors, and seemingly not even the major one, affecting the PRBCs functionality. Therefore, the FIFO approach is not sufficient for assessing the potential transfusion outcome, and the PRBC functionality should be determined explicitly for each unit., (Copyright © 2020. Published by Elsevier Ltd.)

Purpose: Impaired red blood cell (RBC) deformability impedes tissue perfusion. This study aims to investigate RBC biomechanics in type 2 diabetes mellitus (DM) patients with different grades of diabetic retinopathy (DR) and to correlate RBC deformability with hematological and serum biochemical markers., Methods: This cross-sectional study included 86 type 2 DM patients (31 with no DR, 31 with non-proliferative DR [NPDR] and 24 with proliferative DR [PDR]) and 32 control subjects. RBC deformability was measured by a microfluidic cross-slot channel (elongation index, EI). Venous blood samples were taken for assessment of hematological and serum biochemical markers., Results: RBC deformability showed significant reduction in diabetic patients, being lowest in the PDR group, followed by NPDR and DM with no DR groups, and highest in control group (P = .018). RBC deformability was not affected by age or gender but showed significant associations with certain hematological and serum biochemical markers. In the regression analysis controlling for DM status, urea concentration and reticulocyte count were shown to be negatively associated with EI., Conclusion: Impaired RBC deformability measured by a microfluidic cross-slot channel in DM patients with different grades of DR underscores the contribution of RBC rheological properties to the pathogenesis and progression of DM related microangiopathy., (© 2020 The Authors. Microcirculation published by John Wiley & Sons Ltd.)

Extracorporeal circulation is accompanied by changes in red blood cell morphology and structural integrity that affect cell function and survival, and thereby may contribute to the various side effects of heart-lung machine-assisted surgery. Our main objectives were to determine the effect of circulation of red blood cells in a stand-alone extracorporeal circuit on several parameters that are known to be affected by, as well as contribute to red blood cell aging. As a source of RBCs, we employed blood bank storage units of different ages. In order to assess the relevance of our in vitro observations for the characterization of extracorporal circulation technology, we compared these changes in those of patients undergoing extracorporeal circulation-assisted cardiac surgery. Our results show that circulation in a heart-lung machine is accompanied by changes in red blood cell volume, an increase in osmotic fragility, changes in deformability and aggregation behavior, and alterations in the exposure of phosphatidylserine and in microvesicle generation. RBCs from 1-week-old concentrates showed the highest similarities with the in vivo situation. These changes in key characteristics of the red blood cell aging process likely increase the susceptibility of red blood cells to the various mechanical, osmotic, and immunological stress conditions encountered during and after surgery in the patient's circulation, and thereby contribute to the side effects of surgery. Thus, aging-related parameters in red blood cell structure and function provide a foundation for the validation and improvement of extracorporeal circulation technology., (© 2020 The Authors. Artificial Organs published by International Center for Artificial Organ and Transplantation (ICAOT) and Wiley Periodicals LLC.)

The decrease in cellular deformability shows strong correlation with erythrocyte aging. Cell deformation can be divided into passive deformation and active deformation; however, the active deformation has been ignored in previous studies. In this work, Young's moduli of age-related erythrocytes were tested by atomic force microscopy. Furthermore, the deformation and passive and active deformation values were calculated by respective areas. Our results showed that erythrocytes in the densest fraction had the highest values of the Young's modulus, deformation, and active deformation, but the lowest values of passive deformation. Moreover, values of the deformation and active deformation both increased gradually with erythrocyte aging. The present data indicate that the elastic hysteresis loop between the approach and the retract curve could be regarded as erythrocyte deformability, and cellular deformability could be characterized by energy states. In addition, active deformation might be a crucial mechanical factor for clearing aged erythrocytes. This could provide an important information on erythrocyte biomechanics in the removal of aged cell., Competing Interests: Declaration of competing interest The authors declare that none of them has any financial or personal relationships with people or organizations that can inappropriately influence this work or the conclusions drawn from this investigation., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Great deformability allows red blood cells (RBCs) to flow through narrow capillaries in tissues. A number of microfluidic devices with capillary-like microchannels have been developed to monitor storage-related impairment of RBC deformability during blood banking operations. This proof-of-concept study describes a new method to standardize and improve reproducibility of the RBC deformability measurements using one of these devices., Study Design and Methods: The rate of RBC flow through the microfluidic capillary network of the microvascular analyzer (MVA) device made of polydimethylsiloxane was measured to assess RBC deformability. A suspension of microbeads in a solution of glycerol in phosphate-buffered saline was developed to be used as an internal flow rate reference alongside RBC samples in the same device. RBC deformability and other in vitro quality markers were assessed weekly in six leukoreduced RBC concentrates (RCCs) dispersed in saline-adenine-glucose-mannitol additive solution and stored over 42 days at 4°C., Results: The use of flow reference reduced device-to-device measurement variability from 10% to 2%. Repeated-measure analysis using the generalized estimating equation (GEE) method showed a significant monotonic decrease in relative RBC flow rate with storage from Week 0. By the end of storage, relative RBC flow rate decreased by 22 ± 6% on average., Conclusions: The suspension of microbeads was successfully used as a flow reference to increase reproducibility of RBC deformability measurements using the MVA. Deformability results suggest an early and late aging phase for stored RCCs, with significant decreases between successive weeks suggesting a highly sensitive measurement method., (© 2020 AABB.)

Flow-induced damage to red blood cells has been an issue of considerable importance since the introduction of the first cardiovascular devices. Early blood damage prediction models were based on measurements of damage by shear stress only. Subsequently, these models were extrapolated to include other components of the fluid stress tensor. However, the expanded models were not validated by measurements of damage in response to the added types of stress. Recent investigations have proposed that extensional stress might be more damaging to red cells than shear stress. In this study, experiments were conducted to compare human red cell deformation under laminar extensional stress versus laminar shear stress. It was found that the deformation caused by shear stress is matched by that produced by an extensional stress that is approximately 34 times smaller. Assuming that blood damage scales directly with cell deformation, this result indicates that mechanistic blood damage prediction models should weigh extensional stress more than shear stress.

Background: Previously, hemorheology studies using Rheoscan mainly focused on chronic kidney disease, cardiovascular disease, and endocrine disease in adults. The study using LORCA focused on erythrocyte disease. There were no studies using Rheoscan in children., Objective: We aimed to investigate erythrocyte deformability among various hematologic diseases occurring in children, namely, iron deficiency anemia (IDA), hereditary spherocytosis (HS), immune thrombocytopenia (ITP), and aplastic anemia (AA)., Methods: Differences between those with HS, IDA, ITP, AA and healthy controls were compared among 43 patients, comprising 7 patients with HS, 8 patients with IDA, 6 patients with AA, 9 patients with ITP, and 13 healthy controls. Erythrocyte deformability was measured using a microfluidic ektacytometer (RheoScan-D, RheoMeditech, Seoul, Korea). The erythrocyte elongation index (EI) was defined as (L - W)/(L + W), where L and W are the major and minor axes of the ellipse, respectively., Results: The EI values of IDA, HS and AA were significantly decreased compared with healthy controls, but those of ITP were similar to healthy controls., Conclusions: This study showed that erythrocyte deformability differed among various hematologic diseases. Further study concerning correlation in relation to the diagnostic and prognostic significance of erythrocyte deformability in hematologic disease is needed.

Background: Disturbed microcirculation is related to diabetic complications, and erythrocyte deformability is a critical factor regulating microcirculation., Objectives: To know the relationship between the impaired deformability and density profile in diabetic erythrocytes., Methods: We recruited patients with type 2 diabetes (n = 15, diabetic group) and age- and sex-matched non-diabetic subjects (n = 15, control group). Erythrocyte density (ED) profile was obtained by the phthalate ester separation technique. ED distribution was fitted by sigmoidal curve, yielding specific gravity of phthalate ester allowing passage of half erythrocytes population (ED50) and slope factor. Erythrocyte deformability was estimated by our specific filtration technique., Results: Diabetic group showed significantly (p < 0.001) higher HbA1c and fasting blood glucose concentration. Erythrocyte deformability in diabetic group was impaired as compared with that in control group (p < 0.001) and proportional to HbA1c (p = 0.009). However, ED50 and the slope factor in diabetic group did not differ from respective parameters in control group., Conclusions: This study demonstrated that erythrocyte deformability was impaired in diabetic patients even under treatment. HbA1c up to 7.5% is concluded not to alter the erythrocyte density but to impair the deformability, which might be a warning to clinicians for prevention of diabetic complications.

Human red blood cells (RBCs) need to deform in order to pass through capillaries in human vasculature with diameter smaller than that of the RBC. An altered RBC cell membrane stiffness (CMS), thereby, is likely to have consequences on their flow rate. RBC CMS is known to be affected by several commonly encountered disease conditions. This study was carried out to investigate whether an increase in RBC CMS, to the extent seen in such commonly encountered medical conditions, affects the RBC flow rate through channels with diameters comparable to that of the RBC. To do this, we use RBCs extracted from a healthy individual with no known medical conditions and treated with various concentrations of Bovine Serum Albumin (BSA). We study their flow through polycarbonate membranes with pores of diameter 5μm and 8μm which are smaller than and comparable to the RBC diameter respectively. The studies are carried out at constant hematocrit and volumetric flow rate. We find that when the diameter of the capillary is smaller than that of the RBC, the flow rate of the RBCs is lowered as the concentration of BSA is increased while the reverse is true when the diameter is comparable to that of the RBC. We confirm that this is a consequence of altered CMS of the RBCs from their reorientation dynamics in an Optical Tweezer. We find that a treatment with 0.50mg/ml BSA mimics the situation for RBCs extracted from a healthy individual while concentrations higher than 0.50mg/ml elevate the RBC CMS across a range expected for individuals with a condition of hyperglycemia. Using a simple theoretical model of the RBC deformation process at the entry of a narrow channel, we extract the RBC membrane bending modulus from their flow rate., Competing Interests: The authors have declared that no competing interests exist.

Objectives: During cardiac surgery, circulating red blood cells (RBCs) are at risk of exposure to environmental factors during extracorporeal circulation and transfusion of stored RBCs. For this study, the authors observed morphological differences, deformability, density distribution, and erythrocyte indices of RBCs during cardiac surgery with cardiopulmonary bypass (CPB)., Design: Prospective study., Setting: Tertiary care center affiliated with a university hospital., Participants: Adults who underwent elective cardiac surgery requiring CPB., Interventions: Blood samples were obtained from 13 patients before incision (baseline), at initiation of CPB, after separation from CPB, and at completion of surgery., Measurements and Main Results: The morphological index (MI) in RBCs using light microscopy and the maximum deformability index (DImax) using an ektacytometer were evaluated. In addition, the fractionation of RBCs and erythrocyte indices were measured. The MI at initiation of CPB was significantly higher without blood transfusion compared with baseline, although the DImax did not significantly decrease simultaneously. The DImax after separation from CPB and at completion of surgery were significantly lower than that at baseline. This lowered DImax was accompanied by a significantly reduced mean corpuscular volume and elevated mean corpuscular hemoglobin concentration compared with baseline. Dense RBC subpopulations increased after initiating CPB. The MI after separation from CPB and at completion of surgery partially recovered. Administered stored RBCs showed a high MI and the lowest DImax., Conclusions: Morphological changes at initiation of CPB are considered potentially reversible transformations without loss of the membrane surface area and do not have a significant effect on the DImax. A decrease in deformability likely is due to transfusion of stored RBCs., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The capacity to undergo substantial deformation is a defining characteristic of the red blood cell (RBC), facilitating transit through the splenic interendothelial slits and microvasculature. Establishment of this remarkable property occurs during a process of reticulocyte maturation that begins with egress through micron-wide pores in the bone marrow and is completed within the circulation. The requirement to undertake repeated cycles of deformation necessitates that both reticulocytes and erythrocytes regulate membrane-cytoskeletal protein interactions in order to maintain cellular stability. In the absence of transcriptional activity, modulation of these interactions in RBCs is likely to be achieved primarily through specific protein posttranslational modifications, which at present remain undefined. In this study, we use high-throughput methods to define the processes that underlie the response to deformation and shear stress in both reticulocytes and erythrocytes. Through combination of a bead-based microsphiltration assay with phosphoproteomics we describe posttranslational modification of RBC proteins associated with deformation. Using microsphiltration and microfluidic biochip-based assays, we explore the effect of inhibiting kinases identified using this dataset. We demonstrate roles for GSK3 and Lyn in capillary transit and maintenance of membrane stability following deformation and show that combined inhibition of these kinases significantly decreases reticulocyte capacity to undergo repeated deformation. Finally, we derive a comprehensive and integrative phosphoproteomic dataset that provides a valuable resource for further mechanistic dissection of the molecular pathways that underlie the RBC's response to mechanical stimuli and for the study of reticulocyte maturation., (© 2019 by The American Society of Hematology.)

Introduction: Physical exercise or hypoxic exposure influences erythrocyte susceptibility to osmotic stress, and the aquaporin 1 (AQP1) facilitates the transport of water in erythrocytes. This study investigated whether high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) affect erythrocyte osmotic deformability by modulating AQP1 function under hypoxic stress., Methods: Forty-five healthy sedentary males were randomized to engage in either HIIT (3-min intervals at 40% and 80% V˙O2 reserve, n = 15) or MICT (sustained 60% V˙O2 reserve, n = 15) on a bicycle ergometer for 30 min·d, 5 d·wk for 6 wk, or to a control group that did not perform any exercise (n = 15). All subjects were analyzed with osmotic gradient ektacytometry for assessing erythrocyte membrane stability and osmotic deformability after hypoxic exercise (HE) (100 W under 12%O2 for 30 min)., Results: Before the intervention, HE increased the shear stress at 50% of maximal elongation (SS1/2) and the ratio of SS1/2 to maximal elongation index (SS1/2/EImax) on erythrocytes pretreated with 50 Pa of shear stress for 30 min and diminished HgCl2-depressed osmolality at 50%EImax (Ohyper). However, both HIIT and MICT for 6 wk diminished the elevations of erythrocyte SS1/2 and SS1/2/EImax caused by HE. Moreover, HIIT also increased contents of erythrocyte AQP1 proteins while enhancing HgCl2-depressed Ohyper and area under elongation index-osmolarity curve after HE. Additionally, changes in erythrocyte AQP1 contents were associated with changes in HgCl2-depressed erythrocyte Ohyper and area under elongation index-osmolarity curve., Conclusions: Acute HE reduces erythrocyte membrane stability, whereas either HIIT or MICT attenuates the depression of erythrocyte membrane stability by HE. Moreover, HIIT increases the AQP1 content and facilitates the HgCl2-mediated osmotic deformability of erythrocytes after HE.

This paper utilized digital holographic microscopy and optical tweezers to study microdeformation of red blood cells (RBCs) dynamically under oxidative stress. RBCs attached with microbeads were stretched by dual optical tweezers to generate microdeformation. Morphology of RBCs under manipulation were recorded dynamically and recovered by off-axis digital holographic microscopy method. RBCs treated with H 2 O 2 at different concentrations were measured to investigate the mechanical properties under oxidative stress. Use of optical tweezers and off-axis digital holographic microscopy enhanced measuring accuracy compared with the traditional method. Microdeformation of RBCs is also more consistent with the physiological situation. This proposal is meaningful for clinical applications and basic analysis of Parkinson's disease research.

Background and Objective: Hemorheologic alterations have been suggested to play a role in the pathogenesis of diabetic microvascular complications. We measured various hemorheologic parameters and assessed their possible role as a diagnostic tool for diabetic nephropathy (DN)., Methods: 248 subjects with type 2 diabetes and 222 subjects with prediabetes were included in this study. Hemorheologic parameters, including erythrocyte sedimentation rate (ESR), elongation index at 3 Pa (EI) were measured using microfluidic hemorheometer. Various metabolic parameters were measured from fasting blood samples. The subjects were stratified into three groups according to classification of DN by urinary albumin to creatinine ratio (ACR) and four groups by estimated glomerular filtration rate (GFR), than analyzed., Results: Significant differences were observed in metabolic and hemorheologic parameters according to progression of DN. Among them, (Fibrinogen×ESR)/ EI differed in all three groups of urinary ACR. In multiple regression analysis, (Fibrinogen×ESR)/ EI was an independent predictor of urine ACR after adjusted with confounding factors (ß  = 0.010, p < 0.001). (Fibrinogen×ESR)/ EI also showed significant difference no or minimal CKD stage, moderate CKD and severe CKD classified by GFR. This parameter showed area under curve (AUC) of the receiver operating characteristic (ROC) curve of 0.762, and moderate sensitivity and specificity to predict prevalence of microalbuminuria., Conclusions: (Fibrinogen×ESR)/ EI is a sensitive parameter for screening diabetic nephropathy.

Despite their wide clinical usage, stent functionality may be compromised by complications at the site of implantation, including early/late stent thrombosis and occlusion. Although several studies have described the effect of fluid-structure interaction on local haemodynamics, there is yet limited information on the effect of the stent presence on specific hemorheological parameters. The current work investigates the red blood cell (RBC) mechanical behavior and physiological changes as a result of flow through stented vessels. Blood samples from healthy volunteers were prepared as RBC suspensions in plasma and in phosphate buffer saline at 45% haematocrit. Self-expanding nitinol stents were inserted in clear perfluoroalkoxy alkane tubing which was connected to a syringe, and integrated in a syringe pump. The samples were tested at flow rates of 17.5, 35 and 70 ml/min, and control tests were performed in non-stented vessels. For each flow rate, the sample viscosity, RBC aggregation and deformability, and RBC lysis were estimated. The results indicate that the presence of a stent in a vessel has an influence on the hemorheological characteristics of blood. The viscosity of all samples increases slightly with the increase of the flow rate and exposure. RBC aggregation and elongation index (EI) decrease as the flow rate and exposure increases. RBC lysis for the extreme cases is evident. The results indicate that the stresses developed in the stent area for the extreme conditions could be sufficiently high to influence the integrity of the RBC membrane.

Background: Arteriovenous fistula (AVF) may affect erythrocytes through many pathways (e.g., mechanical, inflammatory). However, these effects haven't been elucidated completely yet., Objective: To follow-up the hemorheological and the hematological changes in the presence of artificial carotid-jugular fistula in rats., Methods: Female Wistar rats were subjected to sham-operated group (SG, n = 6) and to fistula group (FG, n = 10). Under general anesthesia, the right carotid artery and jugular vein were isolated via a neck incision, and in the FG carotid-jugular fistula was performed by microsurgical techniques. Hematological variables, red blood cell (RBC) deformability and membrane (mechanical) stability parameters were determined before operation and on the 1st and 6th postoperative weeks. Density separated samples ('young' and 'old' RBCs) were also tested., Results: In FG group hematocrit, RBC and platelet counts increased gradually to reach highly significant level of increment on the 6th postoperative week. RBC deformability significantly was impaired. The membrane stability test showed lower deformability values after applying mechanical shearing. No significant differences were observed between density separated RBC subpopulations., Conclusions: The presence of arteriovenous fistula may lead to an increment of RBC mass and impairment of RBC deformability. These changes could be one of the pathways through which the fistula influences the microcirculation.

Objective: The aim of this study was to analyse the effects of dance movement therapy exercises (DMT) on the rheological properties of blood in elderly women., Methods: The study encompassed group of women (mean aged: 67 years), who were subjected to three-month dance movement therapy programme (n = 20). Blood samples from all the women were examined for their haematological, rheological, and biochemical parameters both prior to the study and three months thereafter., Results: DMT did not cause statistically significant differences in the number of erythrocytes, thrombocytes, leukocytes and the haematocrit value. DMT affected the rheological parameters of the blood in elderly women, improving the erythrocyte deformability at the lowest shear stress value and reducing the half-time of the total aggregation. Plasma viscosity and concentration of fibrinogen did not change after dance therapy., Conclusions: DMT modulate rheological properties of blood of older women. The results of this study suggest that physical exercise program for older women can prevent unfavorable age-related changes. Some indicators such as the haematological parameters, plasma viscosity and fibrinogen level were not affected by DMT in older women, suggesting the maintenance of homeostasis.

Purpose : To investigate differences in red blood cell (RBC) deformability between birdshot chorioretinopathy (BCR) subjects and matched controls, and to postulate its relationship with lack of vascular occlusion in BCR. Methods : In a single center, prospective, non-randomized mechanistic study, blood samples were collected from eight healthy controls and nine BCR patients, and subjected to biochemical and hematological tests, as well as RBC indices assessment using dual-beam optical tweezers. Results : The mean age of the controls was 52.37 ± 10.70 years and BCR patients was 53.44 ± 12.39 years. Initial cell size ( I o ) for the controls was 8.48 ± 0.25 μm and 8.87 ± 0.31 μm for BCR RBCs ( p  = 0.014). The deformability index (DI) for the controls was 0.066 ± 0.02 and that for BCR RBCs was 0.063 ± 0.03 ( p  = 0.441). Conclusion : There was no statistically significant difference in DI between RBCs from BCR and healthy controls. This may explain the rare occurrence of retinal vascular occlusion despite the underlying vasculitic pathophysiology of BCR.

Aim: Nitric oxide (NO) prevents the decline of RBC deformability under high altitude and other ischemic and hypoxic conditions, but the clear mechanisms remain unknown. Here, we have carried out a systematic study to find the mechanisms of NO-induced regulation of RBC deformability under hypoxia., Methods: NO levels, RBCs membrane elongation index (EI), membrane protein band 3 methemoglobin (MetHb) were determined during hypoxia (0 to 120 minutes). To validate the role of NO in regulating RBC deformability, tests were also performed with a NO donor (sodium nitroprusside) or a NO synthase inhibitor (l-nitro-arginine methylester) under 60 minutes hypoxia., Results: Hypoxia for 45 minutes increased NO levels from 25.65 ± 1.95 to 35.26 ± 2.01 μmol/L, and there was a plateau after 60 minutes hypoxia. The EI did not change before 45 minutes hypoxia, but decreased from 0.567 ± 0.019 to 0.409 ± 0.042 (30 Pa) after 60 minutes hypoxia. The cross-linking of band 3 and phosphotyrosine increased after 45 minutes hypoxia. All can be alleviated by supplement NO and aggregated by inhibiting NOS. However, the MetHb was not present this trend., Conclusion: NO may prevent decreased of RBCs deformability through reducing the cross-linking of membrane band 3 under hypoxia; this helps microvascular perfusion of RBCs during ischemic and hypoxic disease states., (© 2018 Wiley Periodicals, Inc.)

Background: Myalgic encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a poorly understood disease. Amongst others symptoms, the disease is associated with profound fatigue, cognitive dysfunction, sleep abnormalities, and other symptoms that are made worse by physical or mental exertion. While the etiology of the disease is still debated, evidence suggests oxidative damage to immune and hematological systems as one of the pathophysiological mechanisms of the disease. Since red blood cells (RBCs) are well-known scavengers of oxidative stress, and are critical in microvascular perfusion and tissue oxygenation, we hypothesized that RBC deformability is adversely affected in ME/CFS., Methods: We used a custom microfluidic platform and high-speed microscopy to assess the difference in deformability of RBCs obtained from ME/CFS patients and age-matched healthy controls., Results and Conclusion: We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls. Our observations suggest that RBC transport through microcapillaries may explain, at least in part, the ME/CFS phenotype, and promises to be a novel first-pass diagnostic test.

The detailed kinetics study of erythrocyte deformability is useful for the early diagnosis of blood diseases and for monitoring the blood rheology. Present solutions for a three-dimensional (3D) reconstruction of erythrocytes has a limited potential. This study aimed to use erythrocyte transmission electron images (ETIs) to evaluate the morphological relationship between adjacent ETIs and generate erythrocytes 3D model. First, ultrathin serial sections of skeletal muscle tissue were obtained using an ultramicrotome. Further, the set of ETIs in a capillary were captured by transmission electron microscopy. The images were aligned by translations and rotations using custom software to optimize the morphological relationship between adjacent ETIs. These coordinate transformations exploit the unique principal axis of inertia of each image to define the body coordinate system and hence provide the means to accurately reconnect the adjacent ETIs. The sum of the distances between the corresponding points on the boundary of adjacent ETIs was minimized and, further, was optimized by using physiological relationship between the adjacent ETIs. The analysis allowed to define precise virtual relationship between the adjacent erythrocytes. Finally, extracted erythrocytes' cross-section images allowed to generate 3D model of the erythrocytes.

Erythrocytes deformation is one of the exciting properties of erythrocytes. It is still under investigation by many of the researchers in different disciplines. The clinicians and researchers are still looking for a simple and efficient method to monitor and tracking the erythrocytes deformation. This research article represented a microscopic technique that could be a helpful tool in evaluation and studying of erythrocytes deformation under different shear stresses. This technique was used to compare the deformation of normal erythrocytes and iron deficiency anemia. Elongation index was calculated and used in the quantitative analysis of erythrocytes deformation. It was found that the deformability of normal erythrocytes was higher than that of iron deficiency anemia. Normal erythrocytes and iron deficiency anemia showed strong negative correlations with the mean cell volume and the mean cell hemoglobin concentration under different shear stresses. This study introduces more understanding of the erythrocytes deformation by using a simple microscopic technique. The elongation index could be used as a measurable parameter to evaluate the deformability of the erythrocyte in normal and abnormal cases.

The current paradigm in the pathogenesis of several hemolytic red blood cell disorders is that reduced cellular deformability is a key determinant of splenic sequestration of affected red cells. Three distinct features regulate cellular deformability: membrane deformability, surface area-to-volume ratio (cell sphericity), and cytoplasmic viscosity. By perfusing normal human spleens ex vivo, we had previously showed that red cells with increased sphericity are rapidly sequestered by the spleen. Here, we assessed the retention kinetics of red cells with decreased membrane deformability but without marked shape changes. A controlled decrease in membrane deformability (increased membrane rigidity) was induced by treating normal red cells with increasing concentrations of diamide. Following perfusion, diamide-treated red blood cells (RBCs) were rapidly retained in the spleen with a mean clearance half-time of 5.9 minutes (range, 4.0-13.0). Splenic clearance correlated positively with increased membrane rigidity ( r = 0.93; P < .0001). To determine to what extent this increased retention was related to mechanical blockade in the spleen, diamide-treated red cells were filtered through microsphere layers that mimic the mechanical sensing of red cells by the spleen. Diamide-treated red cells were retained in the microsphilters (median, 7.5%; range, 0%-38.6%), although to a lesser extent compared with the spleen (median, 44.1%; range, 7.3%-64.0%; P < .0001). Taken together, these results have implications for understanding the sensitivity of the human spleen to sequester red cells with altered cellular deformability due to various cellular alterations and for explaining clinical heterogeneity of RBC membrane disorders., (© 2018 by The American Society of Hematology.)

Background: External applied pneumatic pressure is usually used for rapid transfusion of red blood cells (RBCs). However, increased shear stress can cause increased hemolysis and decreased RBC elongation indices. Therefore, the purpose of this study was to measure the degree of hemolysis and the alteration of RBC elongation indices under varying external pressure in fresh and aged blood., Methods: Venous blood samples were obtained from 20 healthy human volunteers. Each blood bag was divided into 2 subgroups (5 or 35 days of storage), and 5 levels of pressure were applied: 0, 150, 200, 250, and 300 mmHg. After infusion, a laboratory study was conducted. The percentages of irreversibly changed cells were evaluated using Bessis classification. RBC elongation indices were measured using a microfluidic ektacytometer., Results: There were no significant differences in the percentage of irreversibly changed RBCs between the pressures of 0 and 300 mmHg. Moreover, there were no significant differences in laboratory test results or elongation indices among all levels of pressure. Irreversibly changed RBCs and hemolysis were increased depending on the storage period., Conclusion: Irreversible changes in RBCs did not occur as a result of external pressure. The hemolysis and elongation indices of fresh RBCs were not influenced by external pneumatic pressure up to 300 mmHg. Only the storage period affected the irreversible changes in RBCs and hemolysis. Therefore, the application of external pressure to RBCs in variously aged blood is likely to be a safe procedure.

Background: Cardiac syndrome X (CSX) is often described as angina or angina-like chest pain with a normal coronary arteriogram, yet the underlying pathophysiological mechanisms have not been fully elucidated. The aim of the current study was to determine alterations in blood rheology (erythrocyte aggregation and deformability, plasma viscosity - PV) in patients with CSX., Methods: The study comprised 26 CSX patients (55.77 ± 12.33 years) and 37 age- and sex-matched (56.32 ± 11.98 years) healthy controls. Erythrocyte aggregation and deformability were measured by an ektacytometer and PV with a rotational viscometer., Results: Erythrocyte deformability measured at 1.69 and 3.00 Pa was lower in the CSX patients compared to the controls (p = .0001 and .017, respectively). Erythrocyte aggregation index (AI) (72.758 ± 7.65 vs. 66.483 ± 6.63, p = .002) and PV measured at a shear rate of 375 s -1 (1.932 ± 0.225 vs. 1.725 ± 0.331, p = .019) were significantly higher in patients with CSX. When AI, RDW and erythrocyte deformability measured at 1.69 Pa were evaluated together, it was observed that the increase in AI and RDW augments the risk of having CSX (OR: 1.2 and 2.65, respectively), while the rise in deformability decreases this risk (OR = 0.02)., Conclusions: Hemorheological impairments are associated with CSX.

The immersed boundary-lattice Boltzmann method (IB-LBM) was used to examine the motion and deformation of three elastic red blood cells (RBCs) during Poiseuille flow through constricted microchannels. The objective was to determine the effects of the degree of constriction and the Reynolds (Re) number of the flow on the physical characteristics of the RBCs. It was found that, with decreasing constriction ratio, the RBCs experienced greater forced deformation as they squeezed through the constriction area compared to at other parts of the microchannel. It was also observed that a longer time was required for the RBCs to squeeze through a narrower constriction. The RBCs subsequently regained a stable shape and gradually migrated toward the centerline of the flow beyond the constriction area. However, a sick RBC was observed to be incapable of passing through a constricted vessel with a constriction ratio ≤1/3 for Re numbers below 0.40.

Decreased red cell deformability is characteristic of several disorders. In some cases, the extent of defective deformability can predict severity of disease or occurrence of serious complications. Ektacytometry uses laser diffraction viscometry to measure the deformability of red blood cells subject to either increasing shear stress or an osmotic gradient at a constant value of applied shear stress. However, direct deformability measurements are difficult to interpret when measuring heterogenous blood that is characterized by the presence of both rigid and deformable red cells. This is due to the inability of rigid cells to properly align in response to shear stress and results in a distorted diffraction pattern marked by an exaggerated decrease in apparent deformability. Measurement of the degree of distortion provides an indicator of the heterogeneity of the erythrocytes in blood. In sickle cell anemia, this is correlated with the percentage of rigid cells, which reflects the hemoglobin concentration and hemoglobin composition of the erythrocytes. In addition to measuring deformability, osmotic gradient ektacytometry provides information about the osmotic fragility and hydration status of erythrocytes. These parameters also reflect the hemoglobin composition of red blood cells from sickle cell patients. Ektacytometry measures deformability in populations of red cells and does not, therefore, provide information on the deformability or mechanical properties of individual erythrocytes. Regardless, the goal of the techniques described herein is to provide a convenient and reliable method for measuring the deformability and cellular heterogeneity of blood. These techniques may be useful for monitoring temporal changes, as well as disease progression and response to therapeutic intervention in several disorders. Sickle cell anemia is one well-characterized example. Other potential disorders where measurements of red cell deformability and/or heterogeneity are of interest include blood storage, diabetes, Plasmodium infection, iron deficiency, and the hemolytic anemias due to membrane defects.