Partitioning of red blood cells (RBCs) at the level of bifurcations in the microcirculatory system affects many physiological functions yet it remains poorly understood. We address this problem by ...using T-shaped microfluidic bifurcations as a model. Our computer simulations and in vitro experiments reveal that the hematocrit (ϕ0) partition depends strongly on RBC deformability, as long as ϕ0<20% (within the normal range in microcirculation), and can even lead to complete deprivation of RBCs in a child branch. Furthermore, we discover a deviation from the Zweifach–Fung effect which states that the child branch with lower flow rate recruits less RBCs than the higher flow rate child branch. At small enough ϕ0, we get the inverse scenario, and the hematocrit in the lower flow rate child branch is even higher than in the parent vessel. We explain this result by an intricate up-stream RBC organization and we highlight the extreme dependence of RBC transport on geometrical and cell mechanical properties. These parameters can lead to unexpected behaviors with consequences on the microcirculatory function and oxygen delivery in healthy and pathological conditions.
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•red blood cell deformability strongly affects hematocrit partition at capillary bifurcations at intermediate concentrations•at low hematocrits, phase separation is inversed and hematocrit increase is observed in low flow rate branches•intricate RBC organization in capillaries has a decisive influence on their distribution at bifurcations
S100A8 and S100A9 are two calcium binding Myeloid Related Proteins, and important mediators of inflammatory diseases. They were recently introduced as partners for phagocyte NADPH oxidase regulation. ...However, the precise mechanism of their interaction remains elusive. We had for aim (i) to evaluate the impact of S100 proteins on NADPH oxidase activity; (ii) to characterize molecular interaction of either S100A8, S100A9, or S100A8/S100A9 heterocomplex with cytochrome b(558); and (iii) to determine the S100A8 consensus site involved in cytochrome b(558)/S100 interface. Recombinant full length or S100A9-A8 truncated chimera proteins and ExoS-S100 fusion proteins were expressed in E. coli and in P. aeruginosa respectively. Our results showed that S100A8 is the functional partner for NADPH oxidase activation contrary to S100A9, however, the loading with calcium and a combination with phosphorylated S100A9 are essential in vivo. Endogenous S100A9 and S100A8 colocalize in differentiated and PMA stimulated PLB985 cells, with Nox2/gp91(phox) and p22(phox). Recombinant S100A8, loaded with calcium and fused with the first 129 or 54 N-terminal amino acid residues of the P. aeruginosa ExoS toxin, induced a similar oxidase activation in vitro, to the one observed with S100A8 in the presence of S100A9 in vivo. This suggests that S100A8 is the essential component of the S100A9/S100A8 heterocomplex for oxidase activation. In this context, recombinant full-length rS100A9-A8 and rS100A9-A8 truncated 90 chimera proteins as opposed to rS100A9-A8 truncated 86 and rS100A9-A8 truncated 57 chimeras, activate the NADPH oxidase function of purified cytochrome b(558) suggesting that the C-terminal region of S100A8 is directly involved in the molecular interface with the hemoprotein. The data point to four strategic (87)HEES(90) amino acid residues of the S100A8 C-terminal sequence that are involved directly in the molecular interaction with cytochrome b(558) and then in the phagocyte NADPH oxidase activation.
Introduction
The development of an anti‐FVIII inhibitor is the most serious complication of haemophilia A occurring in up to 30% of severe haemophilic patients. The current management of haemophilia ...A with inhibitor uses bypassing agents (BPA) and represents a significant therapeutic burden together with a limited adherence to prophylactic treatment. Emicizumab is the first monoclonal antibody developed in haemophilia A approved for the prevention of bleeding episodes in patients with anti‐FVIII inhibitor.
Aim
The purpose of this study is to evaluate the incremental cost‐effectiveness ratio (ICER) of emicizumab versus BPAs.
Methods
A Markov model was developed over a five‐year time horizon to estimate the comparative costs and benefits of the different therapeutic approaches in this rare disease. Model inputs were clinical, including annual bleeding rate and quality of life, and economical including mainly costs of prophylaxis, bleeds and adverse events.
Results
Emicizumab treatment is dominant, ie lest costly and more effective, in the base‐case analysis saving 234 191 € for a gain of 0.88 QALY. This is confirmed by both the deterministic and probabilistic sensitivity analyses. The main limit of the study remains the absence of long‐term clinical data allowing to relate treatment consumption to clinical benefit, especially in the progression of haemophilic arthropathy.
Conclusion
Our results show that emicizumab is a cost‐effective treatment allowing to consider an easy to implement prophylactic treatment for haemophilia A patients with anti‐FVIII inhibitors.
Among the many factors influencing fibrin formation and structure (concentration, temperature, composition, pH, etc.), it has been suggested that the polydispersity of fibrinogen may play an ...important role. We propose here a detailed investigation of the influence of this parameter on fibrin multiscale structure. Two commercial fibrinogen preparations were used, a monodisperse and a polydisperse one. First, the respective compositions of both fibrinogen preparations were thoroughly determined by measuring the fibrin-stabilizing factor; fibronectin; α, β, and γ intact chain contents; the γ/γ′ chains ratio; the N-glycosylation; and the post-translational modifications. Slight variations between the composition of the two fibrinogen preparations were found that are much smaller than the compositional variations necessary to alter significantly fibrin multiscale structure as observed in the literature. Conversely, multiangle laser light scattering-coupled size exclusion chromatography and dynamic light scattering measurements showed that the polydisperse preparation contains significant amounts of aggregates, whereas the other preparation is essentially monodisperse. The multiscale structure of the fibrins produced from those two fibrinogen preparations was determined by using x-ray scattering, spectrophotometry, and confocal microscopy. Results show that fibers made from the aggregate-free fibrinogen present a crystalline longitudinal and lateral structure and form a mikado-like network. The network produced from the aggregates containing fibrinogen looks to be partly built around bright spots that are attributed to the aggregate. The multiscale structure of mixtures between the two preparations shows a smooth evolution, demonstrating that the quantity of aggregates is a major determining factor for fibrin multiscale structure. Indeed, the effect of a few percent in the mass of aggregates is larger than any other effect because of compositional differences under the same reaction conditions. Finally, we propose a mechanistic interpretation of our results, which points at a direct role of the aggregates during polymerization, which disrupts the ideal ordering of monomers inside fibrin protofibrils and fibers.
Because of the widespread clinical use of heparins, their effects on the enzymatic cascade are very well known. In contrast, little is known about the direct effect of heparins on the nanostructure ...of fibrin fibers, even though this nanostructure plays a major role in the mechanical strength and lysis of clots. This lack of reliable data can be correlated with the lack of a nonintrusive, quantitative method to determine this structure. We recently developed such a method that allows the simultaneous determination of the average fiber radius and the protein content using spectrometric data. In this study, we assessed the nanostructure of fibrin in a system composed of human thrombin and fibrinogen.
We provide quantitative evidence showing that both unfractionated heparin and low molecular weight heparin directly alter the nanostructure of fibrin fibers independent of their other actions on the coagulation cascade; as expected, the pentasaccharide fondaparinux has no effect.
Our results show that in addition to the effect of heparin on the coagulation cascade, modifications of the fibrin nanostructure may also contribute to improved fibrinolysis.
•Drying of blood pools is significantly influenced by blood clotting.•Clotting modifies the morphology of the drying pool (matte/glossy, colour, location of cracks).•Clotting modifies the temporal ...evolution of the drying area.•A clotting-reactivation protocol of citrated blood allows obtaining results in good agreement with freshly drawn blood.
Little is currently known about the importance of clotting during the drying of blood pools. While this is of little moment for droplets where drying occurs faster than contact-phase-induced clotting, clotting may significantly influence blood pools drying as it transform a liquid into a gel. To investigate this influence, we compare the drying of citrated and unmodified blood pools at constant haematocrit, showing large morphological differences during drying, both in the surface appearance, in the colour lightness, as well as in the generation and location of cracks. Further, we designed a clotting-reactivation protocol which allowed recovering the morphological evolution of pure blood drying while using citrate-sampled blood. This result opens the way to the use of citrated blood in blood pools investigations.
HDAC6, a major cytoplasmic deacetylase, is shown here to fine-tune the kinetics of platelet activation, a process that must be precisely regulated to ensure hemostasis after blood vessel injury while ...preventing pathologic thrombus formation. The discoid shape of resting platelets in the circulation is maintained by several highly acetylated microtubules organized in a marginal band. During platelet activation, microtubules undergo major reorganizations, which contribute to the shape change of activating platelets. We show that, during these activation-induced shape changes, a dramatic HDAC6-mediated tubulin deacetylation takes place, followed by microtubule reacetylation in spread platelets. In addition, although HDAC6-controlled tubulin deacetylation is not required for platelet activation, the capacity of HDAC6 to prevent tubulin hyperacetylation influences the speed of platelet spreading. These results are particularly important in view of HDAC6 inhibitors being currently used in clinical trials and represent the first example of cell signaling by lysine acetylation in platelet biology.
Introduction
Rotational Thromboelastometry (ROTEM) is a point of care method used to monitor coagulation during surgery and to guide transfusion strategies in patients presenting with severe ...bleeding. The aim of our study was to determine the impact of four direct oral anticoagulants (DOACs) on 3 commonly used ROTEM tests.
Methods
Whole blood samples from 20 healthy donors were spiked in vitro with apixaban, edoxaban, rivaroxaban or dabigatran at 5 different plasma concentrations (0‐1000 ng/mL). EXTEM, INTEM and FIBTEM tests were systematically performed.
Results
There was a linear relationship between the increase in clotting time (CT) and plasma DOAC concentrations in both the EXTEM and INTEM tests. We found that the DOAC concentration required to double EXTEM CT was 1042 ± 225 ng/mL for apixaban, 134 ± 38 ng/mL for edoxaban, 176 ± 26 ng/mL for rivaroxaban and 284 ± 73 ng/mL for dabigatran. INTEM CT was less sensitive than EXTEM CT whatever the anticoagulant. EXTEM CT was above the normal range for 5 of 5 spiked samples when the plasma concentrations were ~1000 ng/mL for apixaban, ~100 ng/mL for edoxaban, ~200 ng/mL for rivaroxaban and ~200 ng/mL for dabigatran. Maximum Clot Firmness in EXTEM, INTEM and FIBTEM tests was not affected whatever the DOAC or its concentration.
Conclusion
This study found a DOAC dose‐dependent increase in ROTEM CTs. ROTEM tests were only poorly impacted by low levels of edoxaban, rivaroxaban or dabigatran. Apixaban had only a low effect even at high concentrations.
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