Variation in red blood cell deformability and possible consequences for oxygen transport to tissue

Numerical investigation of heterogeneous soft particle pairs in inertial microfluidics

The formation of pairs of particles or cells of different types in microfluidic channels can be desired or detrimental in healthcare applications. It is still unclear what role softness heterogeneity plays in the formation of these particle pairs. We use an in-house lattice-Boltzmann-immersed-boundary-finite-element solver to simulate a pair of particles with different softness flowing through a straight channel with a rectangular cross-section under initial conditions representative of a dilute suspension. We find that softness heterogeneity significantly affects the pair dynamics, determining whether a pair will form or not, and determining the lateral and inter-particle equilibrium behaviour in the pair. We also observe close matches between the transient deformation of particles in a linear pair and single particles in isolation. These results further our understanding of pair behaviour, providing a foundation for understanding particle train formation, and open up the potential to develop reduced-order models for particle pair formation based upon the behaviour of single particles.

Changes in Blood Cell Deformability in Chorea-Acanthocytosis and Effects of Treatment With Dasatinib or Lithium

Misshaped red blood cells (RBCs), characterized by thorn-like protrusions known as acanthocytes, are a key diagnostic feature in Chorea-Acanthocytosis (ChAc), a rare neurodegenerative disorder. The altered RBC morphology likely influences their biomechanical properties which are crucial for the cells to pass the microvasculature. Here, we investigated blood cell deformability of five ChAc patients compared to healthy controls during up to 1-year individual off-label treatment with the tyrosine kinase inhibitor dasatinib or several weeks with lithium. Measurements with two microfluidic techniques allowed us to assess RBC deformability under different shear stresses. Furthermore, we characterized leukocyte stiffness at high shear stresses. The results showed that blood cell deformability–including both RBCs and leukocytes - in general was altered in ChAc patients compared to healthy donors. Therefore, this study shows for the first time an impairment of leukocyte properties in ChAc. During treatment with dasatinib or lithium, we observed alterations in RBC deformability and a stiffness increase for leukocytes. The hematological phenotype of ChAc patients hinted at a reorganization of the cytoskeleton in blood cells which partly explains the altered mechanical properties observed here. These findings highlight the need for a systematic assessment of the contribution of impaired blood cell mechanics to the clinical manifestation of ChAc.

L-cysteine improves blood fluidity impaired by acetaldehyde: In vitro evaluation

Blood fluidity is reportedly influenced by the volume and function of blood cells and plasma and is a predictor of primary cardiovascular events in patients with traditional cardiovascular risk factors. Heavy alcohol consumption was shown to be associated with a higher risk for cardiovascular diseases. Acetaldehyde (ACD), an oxidizing substance formed from ethanol, reportedly stimulates monocyte adhesion, causes abnormalities in the red blood cell (RBC) membrane, and decreases RBC deformability. In addition, it was reported that blood ACD levels are reduced in mice pretreated with L-cysteine. However, there are no studies on the effect of ACD and/or L-cysteine on blood fluidity. In the present study, we evaluated whether ACD impairs blood fluidity. In addition, the effect of L-cysteine on blood fluidity impaired by ACD was examined. Blood samples were obtained from 10 healthy, non-smoking, male volunteers (age: 23.4 ± 1.2 years, body mass index: 21.8 ± 2.6 kg/m²). ACD or ACD and L-cysteine were added to the blood samples before each experiment. We measured the passage time of 100 μL blood and RBC suspension using Kikuchi’s microchannel method. Percentage of microchannel obstruction and the number of adherent white blood cells (WBCs) on microchannel terrace were counted. The blood passage time, percentage of microchannel obstruction, and numbers of adherent WBCs on the microchannel terrace increased after adding ACD in a concentration-dependent manner, whereas they decreased after adding ACD and L-cysteine in a L-cysteine concentration-dependent manner. No significant effects were observed in passage time for 100 μL RBC suspension after adding ACD and L-cysteine. This study suggested that blood fluidity impaired by ACD might improve after adding L-cysteine.

Cerebral and muscle microvascular oxygenation in children with sickle cell disease: Influence of hematology, hemorheology and vasomotion

The present study investigated cerebral and muscle hemoglobin oxygen saturation (tissue oxygen index, TOI) in children with sickle cell anemia (SS), sickle cell hemoglobin C disease (SC) and healthy children (AA). TOI was measured by near-infrared spectroscopy (NIRS) and spectral analysis of the TOI variability was used to assess flowmotion and vasomotion. Arterial oxyhemoglobin saturation (SpO₂), hemorheological and hematological parameters were also measured in SS and SC children. Both TOI were lower in SS compared to both AA and SC children, with SC exhibiting lower values than AA children. Cerebral vasomotion expressed in absolute values was enhanced in SS compared to AA and SC children. Muscle vasomotion did not differ between the three groups. Hematocrit, SpO₂ and red blood cell deformability were positively associated with cerebral TOI in SS children. We demonstrated that 1) cerebral and muscle TOI were markedly decreased in SS children while the decrease of TOI was milder in SC children, 2) cerebral TOI level was associated with several biological markers in SS children only and 3) cerebral vasomotion was enhanced in SS, possibly to counterbalance the effects of chronic cerebral hypoxia.

The effect of exercise on blood fluidity: Use of the capillary model to assess the clogginess of blood

AIM

The goal was to evaluate the effects of exercise on the clogginess of blood as well as the effect of increased blood cell count and hematocrit levels after exercise. We also investigated the mechanisms underlying the clogginess of blood.

METHODS

The time required for blood to pass through microchannels was measured. We focused on assessing the consecutive passage times for serial 20 μL volumes. We used heparinized peripheral blood obtained from subjects after exercise conducted at three intensity levels. Blood samples were also adjusted to achieve specific hematocrit levels or supplemented by addition of adenosine diphosphate (ADP).

RESULTS

The sequential blood passage times of consecutive 20 μL volumes increased with platelet aggregation and adhesion of white blood cells (WBC). We also observed an increase with blood cell counts and hematocrit levels. These changes occurred after high intensity exercise but not after low or medium intensity exercise. Furthermore, the sequential blood passage times of 20 μL volumes increased with platelet aggregation and adhesion of WBC at an ADP concentration at the threshold of aggregation but not at higher levels of hematocrit.

CONCLUSIONS

These findings suggested that high intensity exercise might induce the clogginess of blood by enhanced platelet aggregation and adhesion of WBC.

Intravenous injection of mesenteric lymph produced during hemorrhagic shock decreases RBC deformability in the rat

OBJECTIVE

To test the hypothesis that gut-derived factors carried in trauma-hemorrhagic shock (T/HS) lymph are sufficient to induce red blood cells (RBC) injury, to investigate their potential mechanisms of action, and to define the time post-T/HS that these factors appear in the lymph.

METHODS

Mesenteric lymph collected from T/HS or trauma-sham shock (T/SS) rats over different time periods was injected intravenously into male rats at a rate of 1 mL/h for 3 hours. RBC deformability was measured using laser-assisted ektacytometer to calculate the elongation index. From the shear-stress elongation curve, the stress required for the erythrocytes to reach 50% of their maximal elongation was also determined. RBC deformability was measured before lymph infusion and at 1 hour and 3 hours after the initiation of lymph infusion. The effect of the lymph samples (5% v/v) was also determined in vitro by incubating naïve whole blood with the lymph samples. The potential role of T/HS lymph-induced RBC oxidant injury mediated by inducible nitric oxide synthase (iNOS)-generated oxidants and/or white blood cells (WBC) was investigated using iNOS inhibitors and WBC depletion, respectively. In all the in vivo studies, five to seven rats were studied per group.

RESULTS

The intravenous injection of T/HS lymph but not T/SS lymph caused in vivo RBC injury. The biological activity of T/HS lymph varied over time with the RBC-injurious factors being produced only during the first 3 hours postshock. The in vivo inhibition of iNOS did not prevent lymph-induced RBC injury. T/HS lymph incubated in vitro with naïve whole blood resulted in RBC injury, but this injury was not observed in blood depleted of WBC.

CONCLUSIONS

These results indicate that T/HS lymph produced during the initial 3-hour postshock period is sufficient to induce RBC injury in otherwise normal rats and that the lymph-induced RBC injury is not dependent on activation of the iNOS pathway but seems to require WBC.

Determinants of the daily rhythm of blood fluidity

Background

Numerous processes in the living body exhibit daily rhythmicity. In this study, we characterized a daily rhythm of blood fluidity and identified its determinants.

Methods

The subjects were nine young males. We measured the physiological parameters and performed hematological and biochemical analyses. We repeated the measurements six times during the day at 7:30 (just after getting up and before breakfast), 10:00, 13:30 (after lunch), 16:30, 19:30 (after dinner), and 21:30. The subjects performed sedentary work all day, and the contents and time of the meals were uniform. Investigation of blood rheology was based on Kikuchi's microchannel method.

Results

Blood passage time varied significantly with time of day. Stepwise regression analysis was used to determine the significant factors affecting blood passage time. Body temperature, heartbeat, hematocrit, white blood cell and total cholesterol were significant determinants of blood passage time.

Conclusion

We confirmed that blood fluidity has a daily rhythm. In addition, we found that the determinants of blood fluidity included physiological parameters such as body temperature and heartbeat, hematological parameters such as hematocrit, and white blood cell and total cholesterol.

Augmenting microgel flow via receptor-ligand binding in the constrained geometries of microchannels

We investigated the flow dynamics of biotin-conjugated microgel capsules in avidin-conjugated microchannel constrictions. Microgels were prepared using a microfluidic assembly approach. Biotinylated microgels passing through avidin-modified constrictions slowed relative to several control systems. This effect was observed below a critical velocity of the microgels in the channel-at-large. The reduction in microgel velocity in the constriction occurred for several different sizes of microgels and orifices. Soft compliant microgels showed a lower velocity in the constriction relative to rigid microgels with the same concentration of biotin on the surface, due to the ability of the softer microgels to deform in the orifice and maximize their surface area when in contact with the orifice wall.

Alteration of alpha-spectrin ubiquitination after hemorrhagic shock

BACKGROUND

RBC deformability after trauma and hemorrhagic shock (T/HS) leads to the microcirculatory dysfunction and clinical manifestations of organ failure. However, the cellular mechanism of this phenomenon remains unknown. Spectrins are important for the shape and physical properties of erythrocytes, such as deformability and resistance to mechanical stress. Previous studies have shown that erythrocyte alpha-spectrin is ubiquitinated. Studies of sickled cells and aged erythrocytes, 2 conditions known to have decreased RBC deformability, have shown decreased alpha-spectrin ubiquitination, which may contribute to the inability of these cells to change shape. It was hypothesized that decreased alpha-spectrin ubiquitination could participate in the mechanism(s) whereby T/HS erythrocytes become less deformable.

METHODS

The level of alpha-spectrin ubiquitination in erythrocytes isolated from T/HS rats was determined and compared with erythrocytes from control sham-shocked (T/SS) animals. After T/SS (n = 4) or T/HS (n = 7), alpha- and beta-spectrin subunits were isolated using a low ionic-strength buffer at 37 degrees C for 30 minutes. The relative amount of ubiquitinated alpha-spectrin was evaluated by Western blotting using a monoclonal antibody to ubiquitin.

RESULTS

The relative level of alpha-spectrin ubiquitination (normalized to total alpha-spectrin in the same preparation) was found to be significantly decreased after T/HS (.319 +/- .03) compared with T/SS control erythrocytes (.485 +/- .06, P < .05). To evaluate the content and relative amounts of the other membrane proteins, the profiles of T/HS and T/SS erythrocytes were compared by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. This did not reveal any significant quantitative differences between T/SS and T/HS spectrin or other membrane proteins.

CONCLUSIONS

The finding of decreased alpha-spectrin ubiquitination after T/HS suggests that this mechanism could contribute to increased rigidity of the erythrocyte membrane.

Biological Soft Materials

With one or two exceptions, biological materials are "soft", meaning that they combine viscous and elastic elements. This mechanical behavior results from self-assembled supramolecular structures that are stabilized by noncovalent interactions. It is an ongoing and profound challenge to understand the self-organization of biological materials. In many cases, concepts can be imported from soft-matter physics and chemistry, which have traditionally focused on materials such as colloids, polymers, surfactants, and liquid crystals. Using these ideas, it is possible to gain a new perspective on phenomena as diverse as DNA condensation, protein and peptide fibrillization, lipid partitioning in rafts, vesicle fusion and budding, and others, as discussed in this selective review of recent highlights from the literature.

Disturbance of microcirculation due to unhealthy lifestyle: Cause of type 2 diabetes

Recently, type 2 diabetes seems to be increasing annually in all developed countries. The outcome of type 2 diabetes is often tragic due to succession of complications including renal disorders requiring hemodialysis, blindness, and limb amputation. The expenses for the care of diabetic patients are also a large burden on the society. These circumstances strongly indicate the necessity of prevention. For satisfactory prevention, the clarification of the etiology related to lifestyle is important, but it remains insufficient to date. In this paper, we present a hypothesis of the etiology of type 2 diabetes from the viewpoint of microcirculation. As mentioned later, an unhealthy lifestyle first causes disturbance of the microcirculation, and a portion of the blood is considered to bypass the capillaries via arteriovenous shunts. This prevents the delivery of glucose and insulin to cells of peripheral tissues, causing hyperglycemia unrelated to the cell insulin sensitivity or the endocrine state, i.e., apparent reduction of insulin sensitivity. Disturbance of the microcirculation also causes oxidative stress in peripheral tissues by inducing ischemia and hypoxia. This oxidative stress is considered to further exacerbate reduction of insulin sensitivity. This hypothesis is supported by the well-known fact that insulin sensitivity recovers with improvement in lifestyle including moderate exercise.

Rheological properties of erythrocytes from male hypercholesterolemia

Diet and general health status has close relation to the flow behavior of blood, which influences the circulation of the blood in the body. In this study, we have compared the rheological properties of erythrocyte, plasma and whole blood from high-cholesterol male subjects with healthy male subjects. Intravenous blood was taken from healthy males (n=10) and males with high cholesterol (n=14). Basic health profile, BMI, hematological count and lipid profile (total cholesterol, LDL, HDL and triglyceride) of the blood were determined. Viscosity and shear rate dependent flow behavior of the subjects blood were measured by cone and plate rheometer, and permeability of erythrocytes by pulsed field gradient NMR. Using the microchannel flow analyzer (MC-FAN), the microcirculation of erythrocyte and plasma were investigated. Our data showed a difference in viscosity and consistency index of the whole blood, and permeability (P<0.05) of erythrocytes between the two groups. Also, the time taken for the flow of erythrocyte and plasma through the MC-FAN was slower for the high-cholesterol group. Correlation study showed that consistency index of the blood is closely related to the level of LDL (P<0.05), and total cholesterol, HDL and LDL (P<0.01) highly correlated with the microcirculation of erythrocyte and plasma. A negative correlation (P<0.05) was found between total cholesterol, HDL and LDL, and permeability of erythrocytes. It is concluded that high level of cholesterol, LDL and HDL in vivo alter the morphology and flow behavior of blood cells that can subsequently increase the risk of impairing physical function and microcirculation.

Prestorage leukocyte reduction prevents the formation of microaggregates that occlude artificial capillary vessels

PURPOSE

The passage behavior of stored blood through an artificial microchannel system, as a model of capillary vessels, was examined.

MATERIALS AND METHODS

Using blood obtained from a total of 17 healthy volunteers, untreated and prestorage leukocyte reduced blood, or untreated and prestorage microfiltered (35 microm-pore size) blood were stored, and then the passage behavior through the microchannels was evaluated. Also, using blood from 16 patients stored for about 2 weeks, the effect of a leukocyte reduction filter, microfilter or mesh filter (175-210 microm-pore size) on the passage through the microchannels was examined.

RESULTS

Untreated blood passed through the microchannels immediately after blood collection, but after 1 week occlusion of the microchannels occurred. Prestorage leukocyte reduced blood, however, passed through the microchannels for up to 6 weeks. Occlusion of the microchannels occurred with both the untreated and prestorage microfiltered blood. Although filtration through a leukocyte reduction filter provided blood that can pass through the microchannels, occlusion occurred with blood filtered in other way.

CONCLUSIONS

The present results show that stored blood produces abundant microaggregates, potentially occluding capillary vessels. These microaggregates are not formed after prestorage leukocyte reduction or can be removed by use of a leukocyte reduction filter.

Negative air ions created by water shearing improve erythrocyte deformability and aerobic metabolism

To elucidate a potential mechanism by which negative air ions improve aerobic metabolism, changes in venous blood lactate levels, pH, erythrocyte deformability, and plasma superoxide dismutase activity and ceruloplasmin levels were examined during a 1-h exposure to negative air ions created by water shearing or corona discharge in nine adult healthy volunteers. The blood lactate level decreased from 1.3 +/- 0.3 to 1.0 +/- 0.2 mmol/l, pH increased from 7.388 +/- 0.025 to 7.417 +/- 0.036, and erythrocyte deformability improved from 37.0 +/- 2.2 to 35.1 +/- 3.0 s, expressed as the mean +/- s.d., when exposed to negative air ions created by water shearing, but did not change when exposed to negative air ions created by corona discharge. Other variables did not change in either exposure. The results obtained suggest that negative air ions created by water shearing improve aerobic metabolism by improving erythrocyte deformability.

PRACTICAL IMPLICATIONS

The paper shows that negative air ions created by water shearing method improve aerobic metabolism only during a 1-h exposure, which may be caused by improvement of erythrocyte deformability, but negative air ions created by corona discharge have no effects. A potential mechanism is that negative air ions enter the circulating blood via the lungs and electrons of these ions are delivered to the plasma protein. Why negative air ions created by corona discharge have no effects is considered that water binding does not exist so that the lifetime of these ions is markedly short, by which the ions cannot reach the alveoli of the lungs sufficiently.

Short-term control of capsaicin on blood and oxidative stress of rats in vivo

Capsaicin (8-methyl-n-vanillyl-6-nonenamide), a pungent component found in red pepper can induce body heat and possibly enhance blood flow as well as increase energy expenditure, and prevent oxidative stress. Male Wistar rats were divided into vehicle, 1 mg/kg body weight capsaicin and 3 mg/kg body weight capsaicin groups. Samples were taken from the animals on day 1 of i.p. treatment with capsaicin and on 3 consecutive days of i.p. treatment with capsaicin. Our investigation demonstrated that blood flow measurements in rats was negatively correlated with LDL after treatment with capsaicin. Although capsaicin did not show a noticeable effect on the serum total cholesterol level, LDL decreased while HDL and triglyceride increased in rats treated with 3 mg/kg capsaicin for 3 days. The antioxidant effect of capsaicin was not shown when the rats were treated with 1 mg/kg body weight capsaicin. However, rats treated with 3 mg/kg body weight capsaicin for 3 days showed a reduction of oxidative stress measured as malondialdehyde in the liver, lung, kidney and muscle. Liver glycogen was found to decrease after 3 days treatment with 3 mg/kg body weight capsaicin. From this study, it is hypothesized that capsaicin can be a potent antioxidant and aid in lowering LDL even when consumed for a short period.

Optical Bioimaging: From Living Tissue to a Single Molecule: Imaging and Functional Analysis of Blood Flow in Organic Microcirculation

Activity of blood cells, erythrocytes, leucocytes, and platelets, in microcirculation was observed by using an intravital microscope and confocal laser scanning microscope connected with an image processing system including fluorescence and phosphorescence emission methods. Dynamic functions of the blood flow were mainly observed in mesentery, brain, and liver tissues of rats. The results are summarized as follows: Deformability of diabetic erythrocytes was significantly lower than that of healthy controls, particularly at high shear rate. The spring constant and Young's modulus of diabetic erythrocytes obviously stiffened, making them hard to deform in the capillary. During hemorrhagic shock and thrombosis, flow velocity and oxygen partial pressure of blood decreased in the brain and liver tissues that can be visualized by using FITC stained erythrocytes and Pd-porphyrin derivative as a pO(2) probe. Platelet adhesion and thrombus formation in the micro-vessels accelerated under the photodynamic reaction; diabetic platelets showed augmented adhesion and aggregation on the vessel wall which was followed by acute thromboembolism. Active oxygen radicals take part in thrombus formation, accompanied with adhesion of the activated leucocytes. Fluorescent dye probes, rhodamine G and acridine orange, are quite useful for visualization of the flow behavior of platelets and leucocytes, respectively.

Direct measurement of erythrocyte deformability in diabetes mellitus with a transparent microchannel capillary model and high-speed video camera system

To measure erythrocyte deformability in vitro, we made transparent microchannels on a crystal substrate as a capillary model. We observed axisymmetrically deformed erythrocytes and defined a deformation index directly from individual flowing erythrocytes. By appropriate choice of channel width and erythrocyte velocity, we could observe erythrocytes deforming to a parachute-like shape similar to that occurring in capillaries. The flowing erythrocytes magnified 200-fold through microscopy were recorded with an image-intensified high-speed video camera system. The sensitivity of deformability measurement was confirmed by comparing the deformation index in healthy controls with erythrocytes whose membranes were hardened by glutaraldehyde. We confirmed that the crystal microchannel system is a valuable tool for erythrocyte deformability measurement. Microangiopathy is a characteristic complication of diabetes mellitus. A decrease in erythrocyte deformability may be part of the cause of this complication. In order to identify the difference in erythrocyte deformability between control and diabetic erythrocytes, we measured erythrocyte deformability using transparent crystal microchannels and a high-speed video camera system. The deformability of diabetic erythrocytes was indeed measurably lower than that of erythrocytes in healthy controls. This result suggests that impaired deformability in diabetic erythrocytes can cause altered viscosity and increase the shear stress on the microvessel wall.

Oral supplementation with gamma-linolenic acid extracted from Mucor circinelloides improves the deformability of red blood cells in hemodialysis patients

BACKGROUND

The development of abnormalities in red blood cell (RBC) deformability in patients undergoing hemodialysis remains a major problem, because it is related to peripheral microcirculation, oxygen supply, and various complications in such patients. gamma-Linolenic acid (GLA; 18:3n-6), one of the polyunsaturated fatty acids and a precursor of prostaglandin E(1), is reported to have a favorable effect on the deformability of circulating blood cells in diabetic patients.

METHODS

In order to clarify the efficacy of GLA on RBC deformability in 7 patients undergoing maintenance hemodialysis, we examined in a pilot study the changes in the deformability of RBC and the changes in the phospholipid fatty acid composition in both plasma and RBC membrane before and after high-dose oral supplementation with GLA derived from Mucor circinelloides for 12 weeks.

RESULTS

Before supplementation, the micropore passage time of RBC suspension, which is an indicator of RBC deformability, in these patients was markedly longer than that in healthy control subjects. After administering GLA, the prolonged passage time of the patients both rapidly and steadily decreased and nearly reached control levels. Light microscopic observations of RBCs using Giemsa stain revealed a decreased number of poikilocytes after supplementation. An analysis of the fatty acid composition before treatment and 8 weeks after starting the treatment showed the dihomo-gamma-linolenic acid (DGLA; 20:3n-6) level in the plasma to have increased (p < 0.05), while the arachidonic acid (AA; 20:4n-6) concentration in the RBC membrane decreased (p < 0.05). The level of DGLA in the RBC membrane, the level of GLA, and the ratio of GLA + DGLA/AA in plasma and RBC membrane did not change significantly; however, these all tended to increase.

CONCLUSION

The results of this pilot study indicate that the oral supplementation of GLA extracted from M. circinelloides improves the poor RBC deformability in hemodialysis patients, partly by inducing changes in the composition of fatty acids in plasma and RBC membrane.

A silicon micromachined device for use in blood cell deformability studies

An application of silicon micromachining to the analysis of blood cell rheology is described. The system, based upon a micromachined flow cell, provides a specific measurement of each cell in a statistically significant population in terms of both flow velocity profile and an index of cell volume while the cells flow through an array of microchannels. The rationale, design, and fabrication of the silicon micromachined flow cell is discussed. Interrelated considerations determining the design of the associated fluidic, mechanical, imaging, and real-time image analysis subsystems are examined. Sample data comparing normal and iron deficiency anaemic blood are presented to illustrate the potential of this technique.