Red cell deformability and haematological disorders

Morphology, repulsion, and ordering of red blood cells in viscoelastic flows under confinement

Red blood cells (RBC), the primary carriers of oxygen in the body, play a crucial role across several biomedical applications, while also being an essential model system of a deformable object in the microfluidics and soft matter fields. However, RBC behavior in viscoelastic liquids, which holds promise in enhancing microfluidic diagnostic applications, remains poorly studied. We here show that using viscoelastic polymer solutions as a suspending carrier causes changes in the clustering and shape of flowing RBC in microfluidic flows when compared to a standard Newtonian suspending liquid. Additionally, when the local RBC concentration increases to a point where hydrodynamic interactions take place, we observe the formation of equally-spaced RBC structures, resembling the viscoelasticity-driven ordered particles observed previously in the literature, thus providing the first experimental evidence of viscoelasticity-driven cell ordering. The observed RBC ordering, unaffected by polymer molecular architecture, persists as long as the surrounding medium exhibits shear-thinning, viscoelastic properties. Complementary numerical simulations reveal that viscoelasticity-induced repulsion between RBCs leads to equidistant structures, with shear-thinning modulating this effect. Our results open the way for the development of new biomedical technologies based on the use of viscoelastic liquids while also clarifying fundamental aspects related to multibody hydrodynamic interactions in viscoelastic microfluidic flows.

HIIT serves as an efficient training strategy for basketball players by improving blood fluidity and decreasing oxidative stress

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.

Cell-free layer development and spatial organization of healthy and rigid red blood cells in a microfluidic bifurcation

Bifurcations and branches in the microcirculation dramatically affect blood flow as they determine the spatiotemporal organization of red blood cells (RBCs). Such changes in vessel geometries can further influence the formation of a cell-free layer (CFL) close to the vessel walls. Biophysical cell properties, such as their deformability, which is impaired in various diseases, are often thought to impact blood flow and affect the distribution of flowing RBCs. This study investigates the flow behavior of healthy and artificially hardened RBCs in a bifurcating microfluidic T-junction. We determine the RBC distribution across the channel width at multiple positions before and after the bifurcation. Thus, we reveal distinct focusing profiles in the feeding mother channel for rigid and healthy RBCs that dramatically impact the cell organization in the successive daughter channels. Moreover, we experimentally show how the characteristic asymmetric CFLs in the daughter vessels develop along their flow direction. Complimentary numerical simulations indicate that the buildup of the CFL is faster for healthy than for rigid RBCs. Our results provide fundamental knowledge to understand the partitioning of rigid RBC as a model of cells with pathologically impaired deformability in complex in vitro networks.

Effect of Cell Age and Membrane Rigidity on Red Blood Cell Shape in Capillary Flow

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.

Red blood cell lingering modulates hematocrit distribution in the microcirculation

The distribution of red blood cells (RBCs) in the microcirculation determines the oxygen delivery and solute transport to tissues. This process relies on the partitioning of RBCs at successive bifurcations throughout the microvascular network, and it has been known since the last century that RBCs partition disproportionately to the fractional blood flow rate, therefore leading to heterogeneity of the hematocrit (i.e., volume fraction of RBCs in blood) in microvessels. Usually, downstream of a microvascular bifurcation, the vessel branch with a higher fraction of blood flow receives an even higher fraction of RBC flux. However, both temporal and time-average deviations from this phase-separation law have been observed in recent studies. Here, we quantify how the microscopic behavior of RBC lingering (i.e., RBCs temporarily residing near the bifurcation apex with diminished velocity) influences their partitioning, through combined in vivo experiments and in silico simulations. We developed an approach to quantify the cell lingering at highly confined capillary-level bifurcations and demonstrate that it correlates with deviations of the phase-separation process from established empirical predictions by Pries et al. Furthermore, we shed light on how the bifurcation geometry and cell membrane rigidity can affect the lingering behavior of RBCs; e.g., rigid cells tend to linger less than softer ones. Taken together, RBC lingering is an important mechanism that should be considered when studying how abnormal RBC rigidity in diseases such as malaria and sickle-cell disease could hinder the microcirculatory blood flow or how the vascular networks are altered under pathological conditions (e.g., thrombosis, tumors, aneurysm).

Concerted phenotypic flexibility of avian erythrocyte size and number in response to dietary anthocyanin supplementation

BACKGROUND

Endurance flight impose substantial oxidative costs on the avian oxygen delivery system. In particular, the accumulation of irreversible damage in red blood cells can reduce the capacity of blood to transport oxygen and limit aerobic performance. Many songbirds consume large amounts of anthocyanin-rich fruit, which is hypothesized to reduce oxidative costs, enhance post-flight regeneration, and enable greater aerobic capacity. While their antioxidant benefits appear most straightforward, the effects of anthocyanins on blood composition remain so far unknown. We fed thirty hand-raised European starlings (Sturnus vulgaris) two semisynthetic diets (with or without anthocyanin supplement) and manipulated the extent of flight activity in a wind tunnel (daily flying or non-flying for over two weeks) to test for their interactive effects on functionally important haematological variables.

RESULTS

Supplemented birds had on average 15% more and 4% smaller red blood cells compared to non-supplemented individuals and these diet effects were independent of flight manipulation. Haemoglobin content was 7% higher in non-supplemented flying birds compared to non-flying birds, while similar haemoglobin content was observed among supplemented birds that were flown or not. Neither diet nor flight activity influenced haematocrit.

CONCLUSION

The concerted adjustments suggest that supplementation generally improved antioxidant protection in blood, which could prevent the excess removal of cells from the bloodstream and may have several implications on the oxygen delivery system, including improved gas exchange and blood flow. The flexible haematological response to dietary anthocyanins may also suggest that free-ranging species preferentially consume anthocyanin-rich fruits for their natural blood doping, oxygen delivery-enhancement effects.

Effects of Preconditioning on RBC Deformability in Critically Ill Patients

RBCs from critically ill patients have depressed deformability, especially in sepsis. Prolonged exposure of RBCs from healthy volunteers to physiologic shear stress (the preconditioning technique) has been associated with improved deformability, but the effect of preconditioning on RBCs from critically ill patients with or without sepsis has never been studied.

Problems of Red Blood Cell Aggregation and Deformation Assessed by Laser Tweezers, Diffuse Light Scattering and Laser Diffractometry

This study aims to highlight the problems with implementing optical techniques (laser tweezers, diffuse light scattering and laser diffractometry) in clinical hemorheological practice. We provide the feasibility of these techniques to assess microrheological effects of various molecular mechanisms affecting RBC aggregation and deformability. In particular, we show that they allow assessment of changes in RBC aggregation in whole blood samples both on the level of single cells and on the level of large ensembles of cells. Application of these methods allows for studying the mechanisms of RBC aggregation because they are sensitive to changes in the medium which surrounds the RBC (i.e., blood plasma, serum or model solutions of blood plasma proteins) and to changes in the cellular properties of RBCs (i.e., effects on the cell membrane due to glycoprotein inhibition).

Technologies for measuring red blood cell deformability

Human red blood cells (RBCs) are approximately 8 μm in diameter, but must repeatedly deform through capillaries as small as 2 μm in order to deliver oxygen to all parts of the body. The loss of this capability is associated with the pathology of many diseases, and is therefore a potential biomarker for disease status and treatment efficacy. Measuring RBC deformability is a difficult problem because of the minute forces (∼pN) that must be exerted on these cells, as well as the requirements for throughput and multiplexing. The development of technologies for measuring RBC deformability date back to the 1960s with the development of micropipette aspiration, ektacytometry, and the cell transit analyzer. In the past 10 years, significant progress has been made using microfluidics by leveraging the ability to precisely control fluid flow through microstructures at the size scale of individual RBCs. These technologies have now surpassed traditional methods in terms of sensitivity, throughput, consistency, and ease of use. As a result, these efforts are beginning to move beyond feasibility studies and into applications to enable biomedical discoveries. In this review, we provide an overview of both traditional and microfluidic techniques for measuring RBC deformability. We discuss the capabilities of each technique and compare their sensitivity, throughput, and robustness in measuring bulk and single-cell RBC deformability. Finally, we discuss how these tools could be used to measure changes in RBC deformability in the context of various applications including pathologies caused by malaria and hemoglobinopathies, as well as degradation during storage in blood bags prior to blood transfusions.

Hemoglobin-to-Red-Cell Distribution Width Ratio Is a Novel Predictor of Long-Term Patient Outcomes After Percutaneous Coronary Intervention: A Retrospective Cohort Study

Background

The hemoglobin level and red cell distribution width (RDW) have been linked to the prognosis of coronary atherosclerotic heart disease (CAHD). However, the relationship between the ratio of hemoglobin to the RDW (HRR) and clinical outcomes after percutaneous coronary intervention (PCI) is not known. Here, we explored the impact of the HRR on clinical outcomes after PCI.

Methods

In our study, we selected 6,046 CAHD patients with PCI hospitalized in the First Affiliated Hospital of Xinjiang Medical University from 2008 to 2016. The patients were grouped according to their HRR ratio: group A (HRR < 10.25, n = 2,344) and group B (HRR ≥ 10.25, n = 3,702). The difference in clinical outcomes between the two groups was compared. Patients were followed up for 35.9 ± 22.6 months.

Results

Three hundred nine patients died during follow-up. These included 166 patients (7.1%) in the HRR < 10.25 group and 143 patients (3.9%) in the HRR ≥ 10.25 group (P < 0.001). The incidences of cardiogenic death (5.7 vs. 3.2%) and major cardiovascular adverse events (16.5 vs. 12.9%) also differed significantly between the groups (both Ps < 0.001). Analysis using the multivariate Cox proportional hazard model found a significant association between a decreased HRR and post-PCI mortality (all-cause death, adjusted HR: 1.479, 95% CI: 1.156–1.893, p = 0.002; cardiac death, adjusted HR: 1.470, 95% CI: 1.116–1.936, p = 0.006).

Conclusion

The HRR is predictive of post-PCI mortality among CAHD patients.

The Hemoglobin-to-Red Cell Distribution Width Ratio to Predict All-Cause Mortality in Patients with Sepsis-Associated Encephalopathy in the MIMIC-IV Database

OBJECTIVE

The hemoglobin-to-red cell distribution width ratio (HRR) is associated with the prognosis of sepsis-associated encephalopathy (SAE). This study aimed to determine the relationship between HRR and SAE and to clarify the possible mechanism of HRR as a prognostic factor for SAE.

METHODS

A multivariate Cox proportional-hazards regression model was used to assess the correlation between HRR and all-cause mortality. Piecewise linear regression and smooth-curve Cox proportional-hazards regression models were used to observe whether there was a nonlinear relationship between HRR and all-cause mortality in SAE.

RESULTS

This study included 8853 patients with SAE. A nonlinear relationship between HRR and SAE was observed through a two-segment regression model. The left inflection point for the HRR threshold was calculated to be 15.54, which was negatively correlated with all-cause mortality (HR = 0.83, 95% CI = 0.76-0.91, p < 0.001). Subgroup analyses revealed significant interactions between white blood cell count, glucose, and patients who received dialysis and HRR. The inverse correlation between HRR and SAE was more pronounced in patients who did not receive vasopressin (HR = 0.91, 95% CI = 0.87-0.96, p < 0.001) than in those who did receive vasopressin (HR = 0.94, 95% CI = 0.88-1.02, p=0.152) and was significantly more pronounced in patients without myocardial infarction (HR = 0.91, 95% CI = 0.88-0.96, p < 0.001) than in those with myocardial infarction (HR = 0.94, 95% CI = 0.87-1.02, p < 0.114).

CONCLUSION

This large retrospective study found a nonlinear relationship between all-cause mortality and HRR in patients with SAE in intensive care units, with low HRR being inversely associated with increased all-cause mortality in patients with SAE.

Physical Biomarkers of Disease Progression: On-Chip Monitoring of Changes in Mechanobiology of Colorectal Cancer Cells

Disease can induce changes to subcellular components, altering cell phenotype and leading to measurable bulk-material mechanical properties. The mechanical phenotyping of single cells therefore offers many potential diagnostic applications. Cells are viscoelastic and their response to an applied stress is highly dependent on the magnitude and timescale of the actuation. Microfluidics can be used to measure cell deformability over a wide range of flow conditions, operating two distinct flow regimes (shear and inertial) which can expose subtle mechanical properties arising from subcellular components. Here, we investigate the deformability of three colorectal cancer (CRC) cell lines using a range of flow conditions. These cell lines offer a model for CRC metastatic progression; SW480 derived from primary adenocarcinoma, HT29 from a more advanced primary tumor and SW620 from lymph-node metastasis. HL60 (leukemia cells) were also studied as a model circulatory cell, offering a non-epithelial comparison. We demonstrate that microfluidic induced flow deformation can be used to robustly detect mechanical changes associated with CRC progression. We also show that single-cell multivariate analysis, utilising deformation and relaxation dynamics, offers potential to distinguish these different cell types. These results point to the benefit of multiparameter determination for improving detection and accuracy of disease stage diagnosis.

Hemorheology and oxidative stress in patients with differentiated thyroid cancer following I-131 ablation/metastasis treatment

BACKGROUND

Although radioiodine theraphy (RAIT) is thought to affect blood cells and oxidative stress, hemorheological alterations following dose-dependent RAIT remains unknown.

OBJECTIVE

The aim of this study was to determine the effects of RAIT on hemorheological and oxidative stress parameters in patients with differentiated thyroid cancers (DTC).

METHODS

Totally 31 DTC patients (mean age 46.32±11.15 years) and 26 healthy controls (mean age 50.50±6.22 years) were included. Venous blood samples were collected from each patient before and after treatment (7th day, 1th month and 6th month). Erythrocyte aggregation-deformability and oxidative stress parameters were determined. p < 0.05 was considered as statistically significant.

RESULTS

Erythrocyte deformability of the patients determined at 16.87 and 30 Pascal were significantly lower than healthy individuals. Erythrocyte aggregation index (AI) of the patients was higher, whereas erythrocyte aggregation half-time (t½) was lower compared to control. Erythrocyte deformability values and AI were not significantly different from the pre- and post-radioiodine treatment groups. There was no statistically significant difference between the oxidative stress parameters before and after the treatment.

CONCLUSIONS

Patients were in a worse hemorheological condition compared to healthy individuals. After RAIT, RBC deformability and aggregation were not affected and no significant change in oxidative stress parameters was detected.

Feline non-regenerative anemia: Diagnostic and treatment recommendations

PRACTICAL RELEVANCE

Non-regenerative anemia, or anemia with reticulocytopenia, is a daily diagnosis in feline practice.

CLINICAL CHALLENGES

The disease processes underlying non-regenerative anemia are many and diverse. A major diagnostic evaluation may be required to correctly diagnose and treat the underlying cause.

AUDIENCE

All veterinarians caring for cats will face the diagnostic and therapeutic challenge of non-regenerative anemia. Readers will benefit from the review of diagnostic testing and therapeutic options for non-regenerative anemia.

EVIDENCE BASE

This review summarizes the currently available literature informing diagnostic and treatment recommendations related to non-regenerative anemia. The evidence available to support the recommendations in this review is graded as low and includes predominantly expert opinion, case reports and cases series, on which the authors' interpretation/consensus is based.

Cells Under Stress: An Inertial-Shear Microfluidic Determination of Cell Behavior

The deformability of a cell is the direct result of a complex interplay between the different constituent elements at the subcellular level, coupling a wide range of mechanical responses at different length scales. Changes to the structure of these components can also alter cell phenotype, which points to the critical importance of cell mechanoresponse for diagnostic applications. The response to mechanical stress depends strongly on the forces experienced by the cell. Here, we use cell deformability in both shear-dominant and inertia-dominant microfluidic flow regimes to probe different aspects of the cell structure. In the inertial regime, we follow cellular response from (visco-)elastic through plastic deformation to cell structural failure and show a significant drop in cell viability for shear stresses >11.8 kN/m2. Comparatively, a shear-dominant regime requires lower applied stresses to achieve higher cell strains. From this regime, deformation traces as a function of time contain a rich source of information including maximal strain, elastic modulus, and cell relaxation times and thus provide a number of markers for distinguishing cell types and potential disease progression. These results emphasize the benefit of multiple parameter determination for improving detection and will ultimately lead to improved accuracy for diagnosis. We present results for leukemia cells (HL60) as a model circulatory cell as well as for a colorectal cancer cell line, SW480, derived from primary adenocarcinoma (Dukes stage B). SW480 were also treated with the actin-disrupting drug latrunculin A to test the sensitivity of flow regimes to the cytoskeleton. We show that the shear regime is more sensitive to cytoskeletal changes and that large strains in the inertial regime cannot resolve changes to the actin cytoskeleton.

Investigation of the effects of major ozone autohemotherapy application on erythrocyte deformability and aggregation

BACKGROUND

Ozone is used intensively worldwide in treatment and research of various pathologies due to its healing effects.

OBJECTIVE

The aim of this study is to investigate the effect of major ozone autohemotherapy on erythrocyte deformability and aggregation.

METHODS

10 and 50μg/ml doses of ozone was applied for 20 minute to venous blood samples obtained from 10 healthy male volunteers. Erythrocyte aggregation, deformability were measured by an ektacytometer. Total oxidant status, total antioxidant status were measured via a commercial kit. The oxidative stress index was calculated.

RESULTS

Ozone at 10 and 50μg/ml doses did not alter erythrocyte aggregation. 50μg/ml ozone increased red blood cell (RBC) deformability measured at 0.53 Pa. Compared with the Control value, there was a significant increase in TOS, TAS for the doses of 10 and 50μg/ml. The increase in TAS was found to be more significant at 10μg/ml dose. The most obvious increase in OSI value was observed at 50μg/ml.

CONCLUSION

Our results demonstrate that although 10μg/ml ozone has no effect on hemorheology, 50μg/ml ozone concentration has positive effects on RBC deformability, thus circulation at 0.53 Pa corresponding to the shear stress encountered during venous circulation.

Possible erythrocyte contributions to and exacerbation of the post-thrombolytic no-reflow phenomenon

BACKGROUND

Reperfusion injury often occurs with therapeutic intervention addressing the arterial occlusions causing acute myocardial infarction and stroke. The no-reflow phenomenon has been ascribed to leukocyte plugging and blood vessel constriction in the microcirculation.

OBJECTIVE

To assess possible red cell contributions to post-thrombolytic no-reflow phenomenon.

METHODS

Blood clots were formed by recalcifying 1 ml of citrated fresh human venous blood and then lysed by adding 1,000 units of streptokinase (SK) at several intervals within 1 hour. Red cell deformability was tested by both a microscopic photometric and a filtration technique, viscosity by a cone and plate viscometer, and erythrocyte aggregation by an optical aggregometer.

RESULTS

Two sampling methods were devised for the microscopic photometric test, both of which indicated increases of erythrocyte stiffness after being lysed from the clot by SK. In accompanying experiments, the viscosity, aggregation and filterability of the post-lytic erythrocytes were assessed. Results indicated increased viscosity in Ringer's, decreased aggregation index and filterability through a 5 μm pore size Nuclepore membrane.

CONCLUSION

Findings demonstrated that post-lytic changes in red cell deformability do occur which could contribute to the no-reflow phenomenon.

Blood Quality Diagnostic Device Detects Storage Differences Between Donors

In 2013, nearly 15 million units of banked blood were transfused in the United States of America alone. Blood shortages are expected to increase globally. Donated blood is not equal due to differences in quality and deterioration rate. There are no methods to detect time-dependent biochemical and biophysical changes of red blood cells (RBCs) or the deterioration rate of donated RBCs. Nine randomly selected RBC units collected by the San Diego Blood Bank were examined for interdonor variability over six weeks of storage. In vitro RBC quality was assessed weekly by conventional biochemical tests including free Hb, K+, ATP, P50, 2,3 DPG, lactate, and pH. Deformability was measured via cell filtration. Briefly, the RBC suspension (10% Hct), was forced through a 5.0-μm pore membrane (106 mm2) at various flow rates. No interdonor variability in biochemical or mechanical parameters was observed at baseline. Interdonor variability in biochemical properties (free Hb, K+, ATP, P50, 2,3 DPG, lactate, and pH) was observed after 14 days of storage. However, significant differences from baseline in RBC mechanical properties (i.e., filterability) were observed as early as 7 days into storage at the lowest flow rates and after 28 days of storage at all flow rates. There was a net decrease in filterability over time for all donors, but the rate at which filterability decreased (i.e., deterioration rates) was different when comparing individual donors. Changes in all biochemical parameters were significant different between donors. These data suggest that filterability is more sensitive to changes in blood quality than conventional biochemical parameters.

Near-Wall Migration Dynamics of Erythrocytes in Vivo: Effects of Cell Deformability and Arteriolar Bifurcation

Red blood cell (RBC) deformability has a significant impact on microcirculation by affecting cell dynamics. Despite previous studies that have demonstrated the margination of rigid cells and particles in vitro, little information is available on the in vivo margination of deformability-impaired RBCs under physiological flow and hematocrit conditions. Thus, in this study, we examined how the deformability-dependent, RBC migration alters the cell distribution under physiological conditions, particularly in arteriolar network flows. The hardened RBCs (hRBCs) were found to preferentially flow near the vessel walls of small arterioles (diameter = 47.1-93.3 μm). The majority of the hRBCs (63%) were marginated within the range of 0.7R-0.9R (R: radial position normalized by vessel radius), indicating that the hRBCs preferentially accumulated near the vessel walls. The laterally marginated hRBCs maintained their lateral positions near the walls while traversing downstream with attenuated radial dispersion. In addition, the immediate displacement of RBCs while traversing a bifurcation also contributes to the near-wall accumulation of hRBCs. The notable difference in the inward migration between the marginated nRBCs and hRBCs after bifurcations further supports the potential role of bifurcations in the accumulation of hRBCs near the walls.

Hemorheology in kidney transplantation: A role for cardiovascular risk?

Uremic patients undergoing dialysis (HD) present a cardiovascular risk of death 10-20 fold higher than general population, but also kidney transplantation keeps considerable cardiovascular burden.Hemorheologic profile alterations have been described in HD; comprehensive data on kidney transplant recipients (KT) are missing. Aim of our study is to characterize the hemorheological profile in KT, and to compare these data with HD and healthy volunteers (HV).We investigated 47 HV, 90 HD and 108 KT.We confirm hemorheological alterations in HD. KT, when compared to HD, normalizes many parameters: plasma viscosity, whole blood viscosity at 1-Hz and 200-Hz shear rate, erythrocyte aggregation index and yield stress. KT show a markedly lower erythrocyte deformability (ED). We found no differences among hemorheological parameters between the different classes of immunosuppressive drugs used.In conclusion, HD show various hemorheological defects; this could support the high incidence of cardiovascular complications. KT improves most hemorheological alterations; nevertheless, ED is reduced in KT, maintaining a detrimental injury at microcirculatory level and leading to the progression of fibrosis till to end-stage injury. Impaired ED in KT could also contribute to progression of interstitial fibrosis and tubular atrophy (IF/TA) in grafts.

Hemorheologic alterations in peritoneal dialysis

Dialysis patients present a cardiovascular risk substantially higher than general population, due to both traditional and non-traditional risk factors. Hemorheologic alterations have been extensively described in hemodialysis patients (HD), while little data on hemorheology exist about peritoneal dialysis patients (PD). Aim of our study is to characterize the hemorheological profile of 49 PD, and to compare these data with HD and healthy volunteers. PD showed an improvement of parameters related to macro-circulation (plasma viscosity, whole blood viscosity at 1-Hz, erythrocyte aggregation index and yield stress) when compared to HD, while microcirculatory function resulted severely impaired, as expressed by high values for whole blood viscosity 200-Hz shear rate and lower erythrocyte deformability (ED). In conclusion, we found hemorheologic alterations in PD, with substantial differences with respect to HD; in particular, PD showed profound dysfunction in microcirculatory flow with impaired ED. This alterations may act as a risk factor for accelerated atherosclerosis and precipitate cardiovascular events, and it may have a detrimental effect in the peritoneal microcirculation promoting endothelial activation with subsequent fibrosis, leading to peritoneal membrane malfunctioning.

High-throughput linear optical stretcher for mechanical characterization of blood cells

This study describes a linear optical stretcher as a high-throughput mechanical property cytometer. Custom, inexpensive, and scalable optics image a linear diode bar source into a microfluidic channel, where cells are hydrodynamically focused into the optical stretcher. Upon entering the stretching region, antipodal optical forces generated by the refraction of tightly focused laser light at the cell membrane deform each cell in flow. Each cell relaxes as it flows out of the trap and is compared to the stretched state to determine deformation. The deformation response of untreated red blood cells and neutrophils were compared to chemically treated cells. Statistically significant differences were observed between normal, diamide-treated, and glutaraldehyde-treated red blood cells, as well as between normal and cytochalasin D-treated neutrophils. Based on the behavior of the pure, untreated populations of red cells and neutrophils, a mixed population of these cells was tested and the discrete populations were identified by deformability. © 2015 International Society for Advancement of Cytometry.

The Prognostic Role of Red Blood Cell Distribution Width in Coronary Artery Disease: A Review of the Pathophysiology

Red blood cell distribution width (RDW) is a measure of red blood cell volume variations (anisocytosis) and is reported as part of a standard complete blood count. In recent years, numerous studies have noted the importance of RDW as a predictor of poor clinical outcomes in the settings of various diseases, including coronary artery disease (CAD). In this paper, we discuss the prognostic value of RDW in CAD and describe the pathophysiological connection between RDW and acute coronary syndrome. In our opinion, the negative prognostic effects of elevated RDW levels may be attributed to the adverse effects of independent risk factors such as inflammation, oxidative stress, and vitamin D₃ and iron deficiency on bone marrow function (erythropoiesis). Elevated RDW values may reflect the intensity of these phenomena and their unfavorable impacts on bone marrow erythropoiesis. Furthermore, decreased red blood cell deformability among patients with higher RDW values impairs blood flow through the microcirculation, resulting in the diminution of oxygen supply at the tissue level, particularly among patients suffering from myocardial infarction treated with urgent revascularization.

Mechanical clearance of red blood cells by the human spleen: Potential therapeutic applications of a biomimetic RBC filtration method

During their lifespan, circulating RBC are frequently checked for their deformability. This mechanical quality control operates essentially in the human spleen. RBC unable to squeeze though narrow splenic slits are retained and cleared from the blood circulation. Under physiological conditions this prevents microvessels from being clogged by senescent, rigid RBC. Retention of poorly deformable RBC is an important determinant of pathogenesis in malaria and may also impact the clinical benefit of transfusion. Modulating the splenic retention of RBC has already been proposed to support therapeutic approaches in these research fields. To this aim, the development of microplates for high throughput filtration of RBC through microsphere layers (microplate-based microsphiltration) has been undertaken. This review focuses on potential therapeutic applications provided by this technology in malaria chemotherapy and transfusion.

Multiplexed fluidic plunger mechanism for the measurement of red blood cell deformability

The extraordinary deformability of red blood cells gives them the ability to repeatedly transit through the microvasculature of the human body. The loss of this capability is part of the pathology of a wide range of diseases including malaria, hemoglobinopathies, and micronutrient deficiencies. We report on a technique for multiplexed measurements of the pressure required to deform individual red blood cell through micrometer-scale constrictions. This measurement is performed by first infusing single red blood cells into a parallel array of ~1.7 μm funnel-shaped constrictions. Next, a saw-tooth pressure waveform is applied across the constrictions to squeeze each cell through its constriction. The threshold deformation pressure is then determined by relating the pressure-time data with the video of the deformation process. Our key innovation is a self-compensating fluidic network that ensures identical pressures are applied to each cell regardless of its position, as well as the presence of cells in neighboring constrictions. These characteristics ensure the consistency of the measurement process and robustness against blockages of the constrictions by rigid cells and debris. We evaluate this technique using in vitro cultures of RBCs infected with P. falciparum, the parasite that causes malaria, to demonstrate the ability to profile the deformability signature of a heterogeneous sample.

A functional microengineered model of the human splenon-on-a-chip

The spleen is a secondary lymphoid organ specialized in the filtration of senescent, damaged, or infected red blood cells. This unique filtering capacity is largely due to blood microcirculation through filtration beds of the splenic red pulp in an open-slow microcirculation compartment where the hematocrit increases, facilitating the recognition and destruction of unhealthy red blood cells by specialized macrophages. Moreover, in sinusal spleens such as those of humans, blood in the open-slow microcirculation compartment has a unidirectional passage through interendothelial slits before reaching the venous system. This further physical constraint represents a second stringent test for erythrocytes ensuring elimination of those cells lacking deformability. With the aim of replicating the filtering function of the spleen on a chip, we have designed a novel microengineered device mimicking the hydrodynamic forces and the physical properties of the splenon, the minimal functional unit of the red pulp able to maintain filtering functions. In this biomimetic platform, we have evaluated the mechanical and physiological responses of the splenon using human red blood cells and malaria-infected cells. This novel device should facilitate future functional studies of the spleen in relation to malaria and other hematological disorders.

The association between perioperative allogeneic transfusion volume and postoperative infection in patients following lumbar spine surgery

BACKGROUND

Perioperative allogeneic red blood cell transfusion is a risk factor for surgical site infection. The purpose of this study was to determine if the volume of perioperative allogeneic red blood cell transfusion influences the risk of surgical site infection following lumbar spine procedures.

METHODS

A retrospective matched case control study was performed by reviewing all patients who had undergone lumbar spine surgery at our institution from 2005 to 2009. Surgical site infections (spinal or iliac crest) were identified, all within thirty days of the procedure. Controls were matched to the infection cohort according to age, sex, body mass index, diabetic status, smoking status, Charlson Comorbidity Index, length of surgery, and procedure. A conditional logistic regression was performed to examine the association between transfusion volume and surgical site infection. The results were summarized by an odds ratio.

RESULTS

A total of 1799 lumbar procedures were identified with an infection rate of 3.1% (fifty-six cases). On the basis of the numbers, there was no significant difference in the matched variables between the infection cohort and the matched controls. The volume of transfusion was significantly associated with surgical site infection (odds ratio, 4.00 [95% confidence interval, 1.96 to 8.15]) after adjusting for both unmatched variables of preoperative hemoglobin level and volume of intraoperative blood loss.

CONCLUSIONS

In this retrospective matched case control study, the association between surgical site infection following lumbar spine surgery and volume of perioperative allogeneic red blood cell transfusion was supported.

The effect of L-carnosine on erythrocyte deformability and aggregation according to the cell age in young and aged rats

This study aimed to investigate alterations in hemorheology induced by L-carnosine, an anti- oxidant dipeptide, and to determine their relationship to oxidative stress in density-separated erythrocytes of aged and young rats. 28 male Sprague Dawley rats were divided into 4 groups as aged (Aca), young (Yca) L-carnosine groups (250 mg/kg L-carnosine, i.p.) and aged (As), young (Ys) control groups (saline, i.p.). Density separation was further performed to these groups in order to separate erythrocytes according to their age. Blood samples were used for the determination of erythrocyte deformability, aggregation; and oxidative stress parameters. Erythrocyte deformability of Yca group measured at 0.53 Pa was lower than Aca group. Similarly, deformability of least-dense (young) erythrocytes of Yca group was decreased compared to least-dense erythrocytes of Aca groups. Total antioxidant capacity (TAC) of Aca group was higher and oxidative stress index (OSI) lower than As group. Although L-carnosine resulted in an enhancement in TAC of aged rats, this favorable effect was not observed in erythrocyte deformability and aggregation in the dose applied in this study.

Measuring cell mechanics by optical alignment compression cytometry

To address the need for a high throughput, non-destructive technique for measuring individual cell mechanical properties, we have developed optical alignment compression (OAC) cytometry. OAC combines hydrodynamic drag in an extensional flow microfluidic device with optical forces created with an inexpensive diode laser to induce measurable deformations between compressed cells. In this, a low-intensity linear optical trap aligns incoming cells with the flow stagnation point allowing hydrodynamic drag to induce deformation during cell-cell interaction. With this novel approach, we measure cell mechanical properties with a throughput that improves significantly on current non-destructive individual cell testing methods.

An innovative shape equation to quantify the morphological characteristics of parasitized red blood cells by Plasmodium falciparum and Plasmodium vivax

The morphology of red blood cells is affected significantly during maturation of malaria parasites, Plasmodium falciparum and Plasmodium vivax. A novel shape equation is presented that defines shape of parasitized red blood cells by P. falciparum (Pf-red blood cells) and P. vivax (Pv-red blood cells) at four stages of infection. The Giemsa-stained thin blood films are prepared using blood samples collected from healthy donors, patients having P. falciparum and P. vivax malaria. The diameter and thickness of healthy red blood cells plus Pf-red blood cells and Pv-red blood cells at each stage of infection are measured from their optical images using Olysia and Scanning Probe Image Processor softwares, respectively. Using diameters and thicknesses of parasitized red blood cells, a shape equation is fitted and relative two-dimensional shapes are plotted using MATHEMATICA. The shape of Pf-red blood cell drastically changes at ring stage as its thickness increases by 82%, while Pv-red blood cell remains biconcave (30% increase in thickness). By trophozoite and subsequent schizont stage, the Pf-red blood cell entirely loses its biconcave shape and becomes near spherical (diameter and thickness of ~8 µm). The Pv-red blood cell remains biconcave throughout the parasite development even though its volume increases. These results could have practical use for faster diagnosis, prediction, and treatment of human malaria and sickle-cell diseases.

Hemorheological responses to progressive resistance exercise training in healthy young males

Background

This study aimed to explore the effects of progressive resistance exercise training (PRET) on hemorheology.

Material/Methods

Exercise sessions included 1–3 sets of 8–12 repetitions at 40–60% of 1-repetition maximum (1-RM) for 3 weeks and at 75–80% of 1-RM during weeks 4–12. Red blood cell (RBC) deformability and aggregation were determined by ektacytometry, plasma and whole blood viscosities (WBV) by rotational viscometry. Lactate concentration was evaluated by an analyzer and fibrinogen was evaluated by coagulometry. Plasma total oxidant/antioxidant status was measured by colorimetry.

Results

Following an acute increase after exercise on the first day, RBC deformability was elevated during weeks 3 and 4 (p=0.028; p=0.034, respectively). The last exercise protocol applied in week 12 again caused an acute increase in this parameter (p=0.034). RBC aggregation was increased acutely on the first day, but decreased after that throughout the protocol (p<0.05). At weeks 4 and 12 pre-exercise measurements of WBV at standard hematocrit and plasma viscosity were decreased (p=0.05; p=0.041, respectively), while post-exercise values were increased (p=0.005; p=0.04, respectively). Post-exercise WBV at autologous hematocrit measured at week 12 was increased (p=0.01). Lactate was elevated after each exercise session (p<0.05). Fibrinogen was decreased on the third week (p<0.01), while it was increased on the 4^th week (p=0.005). Plasma antioxidant status was increased at week 3 (p=0.034) and oxidative stress index was decreased at week 4 (p=0.013) after exercise.

Conclusions

The results of this study indicate that PRET may have positive effects on hemorheological parameters.

Red blood cell endothelial nitric oxide synthase does not modulate red blood cell storage hemolysis

BACKGROUND

The red blood cell (RBC) endothelial nitric oxide synthase (eNOS) has been shown to regulate intrinsic RBC rheologic properties, such as membrane deformability, suggesting that a functional eNOS could be important in RBC viability and function during storage. This study examines the correlation between RBC eNOS deficiency and the propensity of RBCs to hemolyze under selected stress conditions including prolonged hypothermic storage.

STUDY DESIGN AND METHODS

Fresh or stored RBCs from normal and eNOS knockout (KO) mice or from healthy human volunteers were subjected to selected hemolytic stress conditions including mechanical stress hemolysis, osmotic stress hemolysis, and oxidation stress hemolysis and evaluated during standard storage in CPDA-1 solutions.

RESULTS

Fresh RBCs from normal and eNOS KO mice demonstrated comparable susceptibility to hemolysis triggered by mechanical stress (mechanical fragility index 6.5 ± 0.5 in eNOS KO vs. 6.4 ± 0.4 for controls; n = 8-9), osmotic stress, and oxidative stress. Additionally, RBCs from both mouse groups exhibited similar hemolytic profile at the end of 14-day hypothermic storage, analogous to 42 days of human RBC storage. Storage of human RBCs (28 days in CPDA-1) in the presence of NOS cofactors (L-arginine and tetrahydro-L-biopterin) or inhibitor (N(5) -[imino(methylamino)methyl]-L-ornithine monoacetate) did not affect cell recovery or hemolytic response to the selected stressors.

CONCLUSION

These studies suggest that RBC eNOS does not modulate susceptibility to hemolysis in response to selected stress conditions or prolonged hypothermic storage. Other strategies to increase nitric oxide (NO) bioactivity after prolonged storage utilizing NOS-independent pathways such as the nitrate-nitrite-NO pathway may prove a more promising approach.

The BOLD effect

The purpose of this chapter is to introduce the novice NMR imager to blood oxygen level dependent (BOLD) contrast as well as remind the seasoned veteran of its beauty. Introduction to many of the factors that influence the BOLD signal is given higher priority than pursuing any subset in exquisite detail. Instead, references are given for readers seeking intense investigations into a given aspect. The hope is that this overview inspires the reader with the elegant simplicity of BOLD contrast while not, at first, intimidating too much with the underlying complexity. As one's knowledge of NMR matures so too will one's understanding, appreciation, and application of BOLD MRI. BOLD contrast derives from variations in the magnetic susceptibility of blood due to variations in the concentration of deoxyhemoglobin. These magnetic susceptibility effects produce local magnetic fields around blood vessels that can result in phase dispersion of nearby spins and, therefore, changes in signal intensity in NMR images. After providing brief historical context for BOLD, this chapter will follow the trail of magnetic susceptibility through definition, its source and location in vivo, and how the source and location in vivo interact with anatomical (e.g., blood vessel size) and imaging considerations (e.g., pulse sequence) to influence the BOLD signal. We will conclude by briefly highlighting clinical and preclinical applications using BOLD contrast.

Sickle cell biomechanics

As the predominant cell type in blood, red blood cells (RBCs) and their biomechanical properties largely determine the rheological and hemodynamic behavior of blood in normal and disease states. In sickle cell disease (SCD), mechanically fragile, poorly deformable RBCs contribute to impaired blood flow and other pathophysiological aspects of the disease. The major underlying cause of this altered blood rheology and hemodynamics is hemoglobin S (HbS) polymerization and RBC sickling under deoxygenated conditions. This review discusses the characterization of the biomechanical properties of sickle RBCs and sickle blood as well as their implications toward a better understanding of the pathophysiology of the disease.

Blood rheological properties in patients with atopic dermatitis (AD)

Inflammatory processes and psychological states may mutually enhance each other as well as contribute to haemorheological alterations. The objective of the recent study was to determine blood rheological profile in patients with AD at different clinical stages. Blood rheology, as estimated by blood viscosity as well as deformability (elongation index-EI) and aggregation of erythrocytes (aggregation half time (AT1/2)--expressing the kinetic aspects and syllectogram amplitude (AMP)--representing total aggregation extent) were measured in 25 female AD patients, who showed clinical features of mild to severe AD and in 14 healthy subjects. There were no significant differences in blood rheological properties between patients with mild AD and the controls. A significant decrease in erythrocytes AT1/2 and AMP as well as EI were observed in severe AD patients as compared to other groups. Whole blood and plasma viscosity were similar in all groups. Both erythrocytes deformability and aggregation may be affected by pathophysiological processes associated with AD. Only AD patients with severe skin changes showed increased aggregability and decreased deformability of erythrocytes, suggesting that the phenomenon might be related to the disease activity.

Hemorheological parameters in children with iron-deficiency anemia and the alterations in these parameters in response to iron replacement

AIM

Iron-deficiency anemia (IDA) is a common disorder in pediatric patients. There are a limited number of studies having controversial results in investigating red blood cell (RBC) deformability and aggregation in adult IDA patients. The aim of this study is to determine the change of hemorheological parameters, including RBC deformability, aggregation, and plasma and whole blood viscosity, in children with IDA following iron supplementation therapy.

MATERIALS AND METHODS

The study was performed on 20 children with IDA (average age 35.5 +/- 6.5 months) and 20 age-matched healthy children. The anemia group was treated with 5 mg/kg/day peroral iron for 2 months. Hematological and hemorheological parameters were determined before and after treatment. An ectacytometer was used for the assessment of RBC deformability and aggregation and a cone-plate rotational viscometer for plasma and whole blood viscosities. Hematological parameters were determined using an electronic hematology analyzer.

RESULTS

Although IDA resulted in a decrement in RBC deformability, aggregation, plasma, and whole blood viscosities, these parameters returned to control values after iron supplementation therapy. Serum ferritin levels and hematological parameters (Hb, MCV, MCH, MCHC) that were lower in IDA patients were also found to be increased after treatment.

CONCLUSION

Iron treatment not only reverses the symptoms of anemia but also may contribute to blood flow regulation by causing increments in the alterations observed in hemorheological parameters during anemia.