Measurement of posttransfusion red cell survival with the biotin label

Ultraviolet light and riboflavin accelerates red blood cell dysfunction in vitro and in a guinea pig transfusion model

BACKGROUND

Quality assessment of modified or processed red blood cell (RBC) components, such as pathogen-reduced RBCs, using only in vitro testing may not always be predictive of in vivo performance. Mouse or rat in vivo models are limited by a lack of applicability to certain aspects of human RBC biology. Here, we used a guinea pig model to study the effects of riboflavin combined with UV light on the integrity of RBCs in vitro and following transfusion in vivo.

MATERIALS AND METHODS

Guinea pig RBCs were collected from whole blood (WB) treated with varying UV doses (10, 20, 40 or 80 J/mL) in the presence of riboflavin (UVR-RBCs). In vitro tests for UVR-RBCs included hemolysis, osmotic fragility, and cellular morphology by scanning electron microscopy. Guinea pigs transfused with one-day post-treatment UVR-RBCs were evaluated for plasma hemoglobin (Hb), non-transferrin bound iron (NTBI), total iron and Perls-detectable hemosiderin deposition in the spleen and kidney, and renal uptake of Hb.

RESULTS

Acute RBC injury was dose dependently accelerated after treatment with UV light in the presence of riboflavin. Aberrant RBC morphology was evident at 20, 40, and 80 J/mL, and membrane lysis with Hb release was prominent at 80 J/mL. Guinea pigs transfused with 40 and 80 J/mL UVR-RBCs showed increased plasma Hb levels, and plasma NTBI was elevated in all UVR-RBC groups (10-80 J/mL). Total iron levels and Perls-hemosiderin staining in spleen and kidney as well as Hb uptake in renal proximal tubules were increased 8 hours post-transfusion with 40 and 80 J/mL UVR-RBCs.

DISCUSSION

UVR-RBCs administered to guinea pigs increased markers of intravascular and extravascular hemolysis in a UV dose-dependent manner. This model may allow for the discrimination of RBC injury during testing of extensively processed RBCs intended for transfusion.

Biotin labeling allows for post-transfusion functional assessment of stored human platelets in mice

BACKGROUND

Platelet radiolabeling with radioisotopes is currently used for human platelet recovery and survival studies. Biotinylation enables ex vivo post-transfusion platelet function testing. Whether platelet biotinylation itself affects platelet function is controversial.

STUDY DESIGN AND METHODS

Platelet concentrates from healthy humans were stored for 6 days. Samples were obtained at 1 or 2 and 6 days, and platelets were labeled following a radiolabeling protocol using saline instead of radioactive indium-111 (sham radiolabeling [sham-RL]). Alternatively, a newly developed biotinylation protocol, a washing protocol, or an unmanipulated control sample were used. Platelet function was assessed by flow cytometry after stimulation with platelet agonists and labeling of platelets with platelet activation markers. To test whether platelets can be activated after transfusion, labeled platelets were transfused into nonobese diabetic/severe combined immunodeficiency mice, and samples were obtained 1 h after transfusion.

RESULTS

The activation profile of biotinylated platelets was comparable to sham-RL platelets before transfusion except for significantly less α-degranulation and more phosphatidyl serine exposure on storage day 1/2. There was no significant difference between sham-RL and biotinylated platelets on storage day 6. Sham-RL and biotinylated platelets were significantly less activatable than washed and unmanipulated control platelets. After transfusion, the activation profile of biotinylated platelets was largely indistinguishable from unmanipulated ones.

DISCUSSION

The decrease in activation level in biotinylated platelets we and others observed appears mainly due to the physical manipulation during the labeling process. In conclusion, biotinylated platelets allow for post-transfusion function assessment, a major advantage over radiolabeling.

Evaluation of a method to fluorescently label platelets for in-human recovery and survival studies

BACKGROUND AND OBJECTIVES

Platelets for transfusion are evaluated for in vivo quality using recovery and survival measurements in healthy human subjects. Radiolabelling is the standard for tracing platelets post-transfusion but imposes logistical and technical limitations. This study investigates the in vitro feasibility of labelling platelets with the calcein family of fluorescent dyes as an alternative to radioisotopes or biotin.

MATERIALS AND METHODS

Protocols for radiolabelling were adapted for use with calcein acetoxymethyl ester (CAM) and biotin. Labelled platelets were analysed by flow cytometry and evaluated for activation and function. We tested feasibility for labelling without manipulation of platelets and for multiplexing of samples.

RESULTS

Labelling at 2 μg CAM/1010 platelets resulted in >99% of CAM+ platelets. There was no significant difference in activation or aggregation between CAM-labelled or biotinylated platelets and vehicle controls although %CD62P+ was significantly lower in platelets that were not processed for labelling. Addition of CAM to the platelet storage bag labelled >95% of platelets. Platelet populations labelled with different dyes could be distinguished by flow cytometry.

CONCLUSION

These data provide a rationale for further development of CAM and other fluorescent dyes as tools for measuring post-transfusion kinetics of platelets.

Advancing in vivo assessment of red blood cell transfusions: A call for radiation-free methods in transfusion medicine

RBC transfusions are a vital clinical therapy to treat anemic patients. The in vivo assessment of red blood cell (RBC) quality post-transfusion is critical to ensuring that the introduction of new RBC products meet established regulatory and clinical quality requirements. Although in vitro quality control testing is routinely performed by blood manufacturers, it is crucial that in vivo tests are performed during the evaluation and regulatory process of new RBC products. This article reviews existing in vivo techniques, like chromium-51 labelling and biotinylation, for determining the circulation and survival of RBCs, and advocates for a move to radiation-free methods. The timely need for radiation-free methods to assess emerging non-DEHP container systems is just one example of why efforts to improve the methods available for in vivo quality assessment is important in transfusion medicine. This review aims to advance our understanding of RBC transfusion in vivo quality assessment and enhance transfusion practices.

( G γ A γ δ β ) 0 $({}^{\rm G}{\gamma}{}^{\rm A}{\gamma}\delta\beta)^0$ -Thalassemia: Report of two cases in a family

Case 1 presented with severe anemia and received an intrauterine blood cell transfusion at 33 weeks of gestation. The anemia spontaneously improved in early infancy. Case 2, the father of Case 1, had an uneventful birth with no evidence of anemia, though microcytic anemia was observed during childhood. The genetic analysis of the β-globin gene cluster identified a novel heterozygous deletion of DNA extending from the Gγ-globin gene downstream to the β-globin gene, confirming a diagnosis of (G γA γδβ)0 -thalassemia. In cases where thalassemia is suspected based on blood tests, a genetic diagnosis should be performed for the sake of the offspring.

Human TLR8 induces inflammatory bone marrow erythromyeloblastic islands and anemia in SLE-prone mice

Anemia commonly occurs in systemic lupus erythematosus, a disease characterized by innate immune activation by nucleic acids. Overactivation of cytoplasmic sensors by self-DNA or RNA can cause erythroid cell death, while sparing other hematopoietic cell lineages. Whereas chronic inflammation is involved in this mechanism, less is known about the impact of systemic lupus erythematosus on the BM erythropoietic niche. We discovered that expression of the endosomal ssRNA sensor human TLR8 induces fatal anemia in Sle1.Yaa lupus mice. We observed that anemia was associated with a decrease in erythromyeloblastic islands and a block in differentiation at the CFU-E to proerythroblast transition in the BM. Single-cell RNAseq analyses of isolated BM erythromyeloblastic islands from human TLR8-expressing mice revealed that genes associated with essential central macrophage functions including adhesion and provision of nutrients were down-regulated. Although compensatory stress erythropoiesis occurred in the spleen, red blood cell half-life decreased because of hemophagocytosis. These data implicate the endosomal RNA sensor TLR8 as an additional innate receptor whose overactivation causes acquired failure of erythropoiesis via myeloid cell dysregulation.

Optimizing RBC Transfusion Outcomes in Patients with Acute Illness and in the Chronic Transfusion Setting

Red blood cell (RBC) transfusion is a common clinical intervention used to treat patients with acute and chronic anemia. The decision to transfuse RBCs in the acute setting is based on several factors but current clinical studies informing optimal RBC transfusion decision making (TDM) are largely based upon hemoglobin (Hb) level. In contrast to transfusion in acute settings, chronic RBC transfusion therapy has several different purposes and is associated with distinct transfusion risks such as iron overload and RBC alloimmunization. Consequently, RBC TDM in the chronic setting requires optimizing the survival of transfused RBCs in order to reduce transfusion exposure over the lifespan of an individual and the associated transfusion complications mentioned. This review summarizes the current medical literature addressing optimal RBC-TDM in the acute and chronic transfusion settings and discusses the current gaps in knowledge which need to be prioritized in future national and international research initiatives.

Short-Term Clinical Outcomes of Packed Red Blood Cell Transfusions with Isolated Enzyme-Phase Crossmatch Incompatibility: A Single-Center Cross-Sectional Study

Acute hemolytic transfusion reactions (AHTRs) are feared complications of packed red blood cell (PRBC) transfusions. This study aimed to investigate the clinical consequences of isolated enzyme-phase crossmatch-incompatible PRBC transfusions by clinically observing all events during the study period at a single institution with the primary goal of detecting AHTRs. Ninety-four transfusions of interest were administered during the study period. Laboratory investigations were adequate in 73 episodes, where no AHTR developed and a mean hemoglobin concentration rise of 1.1 g/dL was documented. Three transfusions were terminated prematurely; however, further investigations ruled out AHTR. The remaining 21 transfusions were also completed uneventfully without noteworthy clinical deterioration. This study’s results provide clinical validation to omit pretransfusion screening with enzyme-phase crossmatch and document the safety and short-term efficacy of isolated enzyme-phase incompatible transfusions. The findings may encourage future clinical research to better understand the long-term efficacy of such transfusions, which may be valuable for transfusion-dependent patients.

Optimizing interpretation of survival studies of fresh and aged transfused biotin-labeled RBCs

BACKGROUND

Ex vivo labeling with 51 chromium represents the standard method to determine red blood cell (RBC) survival after transfusion. Limitations and safety concerns spurred the development of alternative methods, including biotinylated red blood cells (BioRBC).

STUDY DESIGN AND METHODS

Autologous units of whole blood were divided equally into two bags and stored under standard blood bank conditions at 2 to 6°C (N = 4 healthy adult volunteers). One bag was biotinylated (15 μg/ml) on storage days 5 to 7 (fresh) and the other was biotinylated (3 μg/ml) on days 35 to 42 (aged). The proportion of circulating BioRBC was measured serially, and cell-surface biotin was quantified with reference to molecules of equivalent soluble fluorochrome. Clearance kinetics were modeled by RBC age distribution at infusion (Gaussian vs. uniform) and decay over time (constant vs. exponential).

RESULTS

Data were consistent with biphasic exponential clearance of cells of uniform age. Our best estimate of BioRBC clearance (half-life [T1/2 ]) was 49.7 ± 1.2 days initially, followed by more rapid clearance 82 days after transfusion (T1/2  = 15.6 ± 0.6 days). As BioRBC aged in vivo, molecules of equivalent soluble fluorochrome declined with a T1/2 of 122 ± 9 days, suggesting gradual biotin cleavage. There were no significant differences between the clearance of fresh and aged BioRBC.

CONCLUSION

Similar clearance kinetics of fresh and aged BioRBC may be due to the extensive washing required during biotinylation. Survival kinetics consistent with cells with uniform rather than Gaussian or other non-uniform age distributions suggest that washing, and potentially RBC culling, may extend the storage life of RBC products.

SARS-CoV-2 Altered Hemorheological and Hematological Parameters during One-Month Observation Period in Critically Ill COVID-19 Patients

Hematological and hemorheological parameters are known to be altered in COVID-19; however, the value of combined monitoring in order to deduce disease severity is only scarcely examined. A total of 44 acute SARS-CoV-2-infected patients (aCOV) and 44 age-matched healthy controls (Con) were included. Blood of aCOV was sampled at admission (T0), and at day 2 (T2), day 5 (T5), day 10 (T10), and day 30 (T30) while blood of Con was only sampled once. Inter- and intra-group differences were calculated for hematological and hemorheological parameters. Except for mean cellular volume and mean cellular hemoglobin, all blood cell parameters were significantly different between aCOV and Con. During the acute disease state (T0-T5), hematological and hemorheological parameters were highly altered in aCOV; in particular, anemic conditions and increased immune cell response/inflammation, oxidative/nitrosative stress, decreased deformability, as well as increased aggregation, were observed. During treatment and convalescence until T30, almost all abnormal values of aCOV improved towards Con values. During the acute state of the COVID-19 disease, the hematological, as well as the hemorheological system, show fast and potentially pathological changes that might contribute to the progression of the disease, but changes appear to be largely reversible after four weeks. Measuring RBC deformability and aggregation, as well as oxidative stress induction, may be helpful in monitoring critically ill COVID-19 patients.

Measurement of post-transfusion red blood cell survival kinetics in sickle cell disease and β-Thalassemia: A biotin label approach

BACKGROUND

Red blood cell (RBC) transfusions are an important treatment modality for patients with sickle cell disease (SCD) and β-thalassemia. A subgroup of these patients relies on a chronic RBC transfusion regimen. Little is known about RBC survival (RCS) of the transfused allogeneic RBCs. In this study, we aimed to study the RCS kinetics of transfused RBCs in SCD and β-thalassemia and to investigate factors that determine RCS.

METHODS AND MATERIALS

We performed a prospective cohort study on fourteen adults with SCD and β-thalassemia disease receiving a chronic transfusion regimen. RCS and the influence of donor and patient characteristics on RCS were assessed by simultaneous transfusion of two allogeneic RBCs using RBC biotinylation. Phenotyping of well-known RBC markers over time was performed using flow cytometry.

RESULTS

RCS of the two transfused RBC units was similar in most patients. Although intra-individual variation was small, inter-individual variation in RCS kinetics was observed. Most patients demonstrated a non-linear trend in RCS that was different from the observed linear RCS kinetics in healthy volunteers. After an initial slight increase in the proportion of biotinylated RBCs during the first 24 h, a rapid decrease within the first 10-12 days was followed by a slower clearance rate.

CONCLUSION

These are the first data to demonstrate that patient-related factors largely determine post-transfusion RCS behavior of donor RBC in SCD and β-thalassemia, while donor factors exert a negligible effect. Further assessment and modeling of RCS kinetics and its determinants in SCD and β-thalassemia patients may ultimately improve transfusion therapy.

Methods to Evaluate the Potential Clinical Significance of Antibodies to Red Blood Cells

Immune-mediated red blood cell (RBC) destruction due to antibodies is an ongoing problem in transfusion medicine for the selection of the safest blood. Serological testing often revealed incompatibility with donors' RBCs. When this incompatible blood was transfused, destruction was due mostly to extravascular-mediated phagocytosis of the antibody-opsonized RBCs; however, intravascular hemolysis was sometimes observed without explanation. Based on serology, antibodies with potential for clinical sequalae could not be ascertained; thus, antigen-negative blood was usually selected for transfusion to avoid problems. Antibodies to antigens having very high frequency in the general population (>95%), however, made selection of antigen-negative blood difficult and sometimes impossible. Some patients, who were sensitized by previous transfusions or by pregnancy, developed multiple antibodies, again creating a problem for finding compatible blood for transfusion, without the ability to discern which of the antibodies may be clinically irrelevant and ignored. Transfusion medicine scientists began searching for an in vitro means to determine the in vivo outcome of transfusion of blood that was serologically incompatible. Methods such as chemiluminescence, monocyte-macrophage phagocytosis, and antibody-dependent cellular cytotoxicity (ADCC) were described. Over the years, the monocyte monolayer assay (MMA) has emerged as the most reliable in vitro assay for the prediction of the clinical relevance of a given antibody. ADCC has not been fully studied but has the potential to be useful for predicting which antibodies may result in intravascular hemolysis. This article captures the protocols for the implementation and readout of the MMA and ADCC assays for use in predicting the clinical significance of antibodies in a transfusion setting. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Monocyte monolayer assay (MMA) Basic Protocol 2: Antibody-dependent cellular cytotoxicity assay (ADCC).

Antibodies against biotin-labeled red blood cells can shorten posttransfusion survival

BACKGROUND

In hematologic and transfusion medicine research, measurement of red blood cell (RBC) in vivo kinetics must be safe and accurate. Recent reports indicate use of biotin-labeled RBC (BioRBC) to determine red cell survival (RCS) offers substantial advantages over ⁵¹ Cr and other labeling methods. Occasional induction of BioRBC antibodies has been reported.

STUDY DESIGN AND METHODS

To investigate the causes and consequences of BioRBC immunization, we reexposed three previously immunized adults to BioRBC and evaluated the safety, antibody emergence, and RCS of BioRBC.

RESULTS

BioRBC re-exposure caused an anamnestic increase of plasma BioRBC antibodies at 5-7 days; all were subclass IgG₁ and neutralized by biotinylated albumin, thus indicating structural specificity for the biotin epitope. Concurrently, specific antibody binding to BioRBC was observed in each subject. As biotin label density increased, the proportion of BioRBC that bound increased antibody also increased; the latter was associated with proportional accelerated removal of BioRBC labeled at density 6 μg/mL. In contrast, only one of three subjects exhibited accelerated removal of BioRBC density 2 μg/mL. No adverse clinical or laboratory events were observed. Among three control subjects who did not develop BioRBC antibodies following initial BioRBC exposure, re-exposure induced neither antibody emergence nor accelerated BioRBC removal.

DISCUSSION

We conclude re-exposure of immunized subjects to BioRBC can induce anamnestic antibody response that can cause an underestimation of RCS. To minimize chances of antibody induction and underestimation of RCS, we recommend an initial BioRBC exposure volume of ≤10 mL and label densities of ≤18 μg/mL.

Red blood cells: The metamorphosis of a neglected carrier into the natural mothership for artificial nanocarriers

Drug delivery research pursues many types of carriers including proteins and other macromolecules, natural and synthetic polymeric structures, nanocarriers of diverse compositions and cells. In particular, liposomes and lipid nanoparticles represent arguably the most advanced and popular human-made nanocarriers, already in multiple clinical applications. On the other hand, red blood cells (RBCs) represent attractive natural carriers for the vascular route, featuring at least two distinct compartments for loading pharmacological cargoes, namely inner space enclosed by the plasma membrane and the outer surface of this membrane. Historically, studies of liposomal drug delivery systems (DDS) astronomically outnumbered and surpassed the RBC-based DDS. Nevertheless, these two types of carriers have different profile of advantages and disadvantages. Recent studies showed that RBC-based drug carriers indeed may feature unique pharmacokinetic and biodistribution characteristics favorably changing benefit/risk ratio of some cargo agents. Furthermore, RBC carriage cardinally alters behavior and effect of nanocarriers in the bloodstream, so called RBC hitchhiking (RBC-HH). This article represents an attempt for the comparative analysis of liposomal vs RBC drug delivery, culminating with design of hybrid DDSs enabling mutual collaborative advantages such as RBC-HH and camouflaging nanoparticles by RBC membrane. Finally, we discuss the key current challenges faced by these and other RBC-based DDSs including the issue of potential unintended and adverse effect and contingency measures to ameliorate this and other concerns.

Circulating Wnt Ligands Activate the Wnt Signaling Pathway in Mature Erythrocytes

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A fluorometric erythrophagocytosis assay using differentiated monocytic THP-1 cells to assess the clinical significance of antibodies to red blood cells

BACKGROUND AND OBJECTIVES

The significance of antibodies to red blood cells (RBCs) is variable and cannot be predicted solely by serological testing. A flow cytometry-based erythrophagocytosis assay was established using phorbol 12-myristate 13-acetate (PMA)-treated THP-1 cells and RBCs labelled with PKH26 to assess allo- and autoantibodies to RBCs.

MATERIALS AND METHODS

THP-1 cells were differentiated into macrophage-like cells by treatment with PMA. RBC samples coated with alloantibodies or autoantibodies were obtained from 16 patients with autoimmune haemolytic anaemia of warm type (wAIHA) as well as from five pregnant women with warm autoantibodies. RBCs from healthy blood donors were used as controls. RBCs were labelled with the red lipophilic fluorescent dye PKH26 and incubated with PMA-treated THP-1 cells. After removal of nonadherent RBCs by washing and haemolysis of adherent RBCs, erythrophagocytosis was quantified by flow cytometry.

RESULTS

We observed significant phagocytosis of RBCs coated with clinically relevant alloantibodies (i.e. anti-D and anti-K) or autoantibodies from patients with active wAIHA, but not of those coated with alloantibodies (anti-Ch) or autoantibodies from patients and pregnant women without haemolysis.

CONCLUSION

The flow cytometry-based erythrophagocytosis test described here is quantitative, highly reliable, and may be helpful for the assessment of the clinical significance of antibodies to RBCs.

Monocyte monolayer assay in pre-transfusion testing: A magic key in transfusing patients with recurrent bad cross-match due to alloimmunization

BACKGROUND

The monocyte monolayer assay (MMA) is an in-vitro assay that can predict the outcome of blood transfusion of antigen positive units when serologically compatible blood is not available.

MATERIALS AND METHODS

Fifty-four patients testing positive by the antibody screening test using gel agglutination were further examined by the alloantibody identification panel to determine alloantibody specificity. After determining and categorizing the antibodies, patients' samples were examined using the MMA to determine the clinical significance of the detected alloantibodies. We also tested 2 seeding methods (24-well cell culture plates versus 8-well chamber-slides) and 3 visualization/staining techniques (unstained phase contrast, Leishman and Giemsa staining).

RESULTS

35 out of the 54 cases (64.8%) had a monocyte index of >5% which is predictive of occurrence of hemolytic reaction after transfusion; 23 cases with antibodies known to be clinically significant [anti-C, anti-E, anti-c, anti-K, anti-Fy(a), anti Fy(b), anti-JK(b)], 2 with Anti-M specificity, 7 cases with autoantibodies and 3 cases with multiple antibodies. On the other hand, 19 out of the 54 (35.2%) cases included in the study showed a monocyte index of <5% which is predictive of absence of hemolytic reaction after transfusion. The 8-well chamber-slides were better than the 24-well culture plates, as the latter showed a lot of un-phagocytosed RBCs in the background. Also, Leishman staining was better than Giemsa staining with better and clearer differentiation between the RBCs, monocytes and phagocytic vacuoles.

CONCLUSION

MMA can be used as a surrogate cross-match test for the selection of blood units in cases where antigen-negative blood units are not available.

Comparison of a closed system and an open system for blood collection in feline donors

OBJECTIVES

This research aimed to evaluate the performance of a closed blood collection system and to compare it with an open system in terms of feasibility, tolerability by the donor, quality of blood collected and bacterial contamination.

METHODS

Eight feline blood donors were prospectively and randomly subjected to both collection methods. Heart rate (HR), respiratory rate (RR) and blood pressure (BP) were evaluated before sedation, after sedation and after blood collection. The duration of the donation, the formation of a hematoma, and the degree of hemolysis and packed cell volume (PCV) of each blood unit were evaluated. Aliquot samples were aseptically collected from each unit and tested for bacterial contamination by culture and PCR on days 0, 14 and 28 of storage.

RESULTS

There was no significant difference between collection methods for HR and RR at any time point. Before sedation, the mean systolic BP was significantly higher with the closed system (closed 169 mmHg, open 137 mmHg; P = 0.003). The average duration of collection was significantly shorter with the closed system (closed 3 mins 10 s, open 8 mins; P = 0.035); however, the prevalence of a successful blood collection with a single venipuncture and hematoma formation were not significantly different between systems. The mean unit PCV was significantly higher with the open system (closed 31%, open 34%; P = 0.026). On bacterial culture, 15/16 units were negative at all time points (closed 7; open 8). Using PCR, 5/16 units were positive for Ralstonia species for at least one time point (closed 3; open 2).

CONCLUSIONS AND RELEVANCE

Our designed closed system appears to be well adapted to feline blood collection and was well tolerated by the donors, performing similarly to an open system, and could represent a valuable clinical device for the development of a feline blood bank, namely feline blood storage.

What about Platelet Function in Platelet Concentrates?

The characterization of platelet concentrates (PCs) in transfusion medicine has been performed with different analytical methods and platelet lesions (from biochemistry to cell biology) have been documented. In routine quality assessment and validation of manufacturing processes of PCs for transfusion purposes, only basic parameters are monitored and the platelet functions are not included. However, PCs undergo several manipulations during the processing and the basic parameters do not provide sensitive analyses to properly picture out the impact of the blood component preparation and storage on platelets. To improve the transfusion supply chain and the platelet functionalities, additional parameters should be used. The present short review will focus on the different techniques to monitor ex vivo platelet lesions from phenotype characterization to advanced omic analyses. Then, the opportunities to use these methods in quality control, process validation, development, and research will be discussed. Functional markers should be considered because they would be an advantage for the future developments in transfusion medicine.

Caesalpinia crista coat extract protects red blood cell from sodium nitrite-induced oxidative stress and exhibits antiplatelet activity

: To understand the RBC protecting efficiency and antiplatelet activity of methanolic extract of Caesalpinia crista coat (MECCC). RBC-protecting activity of MECCC was evaluated using assays, such as DPPH, level of lipid peroxidation, protein carbonyl content, superoxide dismutase and catalase as a marker of oxidative stress whereas, platelet aggregation inhibition was performed using human platelet-rich plasma (PRP). MECCC showed about 76% of DPPH-scavenging activity, with an IC50 value of 71.89 μg/ml. The MECCC reduced the level of lipid peroxidation and protein carboxylation in RBC caused by NaNO2 in a dose-dependent manner. In addition, MECCC normalized the levels of superoxide dismutase (SOD) and catalase (CAT) in oxidative stress-induced RBC in a dose-dependent manner. This suggested the protective effect of MECCC on RBC against oxidative stress. Furthermore, MECCC also exhibited mild antiplatelet activity by inhibiting both ADP and epinephrine agonists that induced platelet aggregation. The noticed inhibition percentage was found to be 28 and 23%, respectively at the concentration of 150 μg. Interestingly, MECCC did not hydrolyse the RBC suggesting its nontoxic properties. MECCC possesses protective effect of RBC against NaNO2 (10 mmol/l) induce oxidative stress and inhibits platelet aggregation.

Fast RBC loading by fluorescent antibodies and nuclei staining dye and their potential bioanalytical applications

This study was designed to load different antibodies (Abs) and a fluorescent dye onto the red blood cell (RBC) surface. We have used fluorescein isothiocyanate (FITC)-conjugate anti-human Ab, CD22-PE (B-cell marker-phycoerythrin Ab), and 4',6-diamidino-2-phenylindole (DAPI) for insertion over the RBC surface. In a first step, conjugation experiments were performed: in dimethyl sulfoxide (DMSO), RBCs were conserved and modified by succinic anhydride to create an additional -COOH group, and then activated with 3-(3-dimethylaminopropyl)carbodiimide-N-hydroxysuccinimide (EDC-NHS) in 2-(N-morpholino) ethanesulfonic acid hydrate buffer for insertion of labeled Abs or DAPI. In a second step, fluorescence signals were evaluated by microscopy and the mean fluorescence intensities of cell lysates were measured by spectrofluorometry. The results showed clear evidence for adsorption of FITC- and PE-labeled Abs to activated conserved RBCs. DAPI was adsorbed well also to DMSO-conserved RBCs without the need for an activation step. The DMSO conservation step was enough to create reactive RBCs for insertion of specific Abs and fluorescent dyes. The additional modification by succinic anhydride and activation with EDC-NHS resulted in two- to seven-fold increase in fluorescence signals, indicating a much higher RBC loading capacity. These Ab- and fluorescent dye-functionalized RBCs have potentially high application in developing new biomedical diagnostic and in vitro assay techniques.

Reexamination of the chromium-51-labeled posttransfusion red blood cell recovery method

BACKGROUND

The chromium-51-labeled posttransfusion recovery (PTR) study has been the gold-standard test for assessing red blood cell (RBC) quality. Despite guiding RBC storage development for decades, it has several potential sources for error.

METHODS

Four healthy adult volunteers each donated an autologous, leukoreduced RBC unit, aliquots were radiolabeled with technetium-99m after 1 and 6 weeks of storage, and then infused. Subjects were imaged by single-photon-emission computed tomography immediately and 4 hours after infusion. Additionally, from subjects described in a previously published study, adenosine triphosphate levels in transfusates infused into 52 healthy volunteers randomized to a single autologous, leukoreduced, RBC transfusion after 1, 2, 3, 4, 5, or 6 weeks of storage were correlated with PTR and laboratory parameters of hemolysis.

RESULTS

Evidence from one subject imaged after infusion of technetium-99m-labeled RBCs suggests that, in some individuals, RBCs may be temporarily sequestered in the liver and spleen immediately following transfusion and then subsequently released back into circulation; this could be one source of error leading to PTR results that may not accurately predict the true quantity of RBCs cleared by intra- and/or extravascular hemolysis. Indeed, adenosine triphosphate levels in the transfusates correlated more robustly with measures of extravascular hemolysis in vivo (e.g., serum iron, indirect bilirubin, non-transferrin-bound iron) than with PTR results or measures of intravascular hemolysis (e.g., plasma free hemoglobin).

CONCLUSIONS

Sources of measurement error are inherent in the chromium-51 PTR method. Transfusion of an entire unlabeled RBC unit, followed by quantifying extravascular hemolysis markers, may more accurately measure true posttransfusion RBC recovery.

Development, validation, and potential applications of biotinylated red blood cells for posttransfusion kinetics and other physiological studies: evidenced-based analysis and recommendations

The current reference method in the United States for measuring in vivo population red blood cell (RBC) kinetics utilizes chromium-51 (⁵¹ Cr) RBC labeling for determining RBC volume, 24-hour posttransfusion RBC recovery, and long-term RBC survival. Here we provide evidence supporting adoption of a method for kinetics that uses the biotin-labeled RBCs (BioRBCs) as a superior, versatile method for both regulatory and investigational purposes. RBC kinetic analysis using BioRBCs has important methodologic, analytical, and safety advantages over ⁵¹ Cr-labeled RBCs. We critically review recent advances in labeling human RBCs at multiple and progressively lower biotin label densities for concurrent, accurate, and sensitive determination of both autologous and allogeneic RBC population kinetics. BioRBC methods valid for RBC kinetic studies, including successful variations used by the authors, are presented along with pharmacokinetic modeling approaches for the accurate determination of RBC pharmacokinetic variables in health and disease. The advantages and limitations of the BioRBC method-including its capability of determining multiple BioRBC densities simultaneously in the same individual throughout the entire RBC life span-are presented and compared with the ⁵¹ Cr method. Finally, potential applications and limitations of kinetic BioRBC determinations are discussed.

Measuring Post-transfusion Recovery and Survival of Red Blood Cells: Strengths and Weaknesses of Chromium-51 Labeling and Alternative Methods

The proportion of transfused red blood cells (RBCs) that remain in circulation is an important surrogate marker of transfusion efficacy and contributes to predict the potential benefit of a transfusion process. Over the last 50 years, most of the transfusion recovery data were generated by chromium-51 (⁵¹Cr)-labeling studies and were predominantly performed to validate new storage systems and new processes to prepare RBC concentrates. As a consequence, our understanding of transfusion efficacy is strongly dependent on the strengths and weaknesses of ⁵¹Cr labeling in particular. Other methods such as antigen mismatch or biotin-based labeling can bring relevant information, for example, on the long-term survival of transfused RBC. These radioactivity-free methods can be used in patients including from vulnerable groups. We provide an overview of the methods used to measure transfusion recovery in humans, compare their strengths and weaknesses, and discuss their potential limitations. Also, based on our understanding of the spleen-specific filtration of damaged RBC and historical transfusion recovery data, we propose that RBC deformability and morphology are storage lesion markers that could become useful predictors of transfusion recovery. Transfusion recovery can and should be accurately explored by more than one method. Technical optimization and clarification of concepts is still needed in this important field of transfusion and physiology.

A method for red blood cell biotinylation in a closed system

BACKGROUND

Several circumstances require the accurate measurement of red blood cell (RBC) survival and clearance, such as determination of posttransfusion recovery of stored RBCs to investigate the effect of new additive solutions. To this end, biotin as a marker of RBCs to track donor RBCs in the blood of the recipient has been used in many studies. However, so far only experimental, nonvalidated, biotin-labeled red cell concentrates (RCCs) are transfused. The goal of this study was to produce a standardized biotin-labeled RCC product in a fast, simple, and sterile manner that can be used for clinical research and for the evaluation of new blood products according to Good Practice Guidelines (GPG) for blood establishments.

STUDY DESIGN AND METHODS

RCC fractions were labeled with two different concentrations of biotinylation reagent in a closed system, to prevent bacterial contamination of the end product. Using flow cytometry, the reproducibility and robustness of the biotin labeling was assessed, as well as the stability of the biotin label on the (un-)irradiated RCC fraction. Additionally, parameters such as phosphatidylserine (PS) exposure, sodium (Na), potassium (K), free hemoglobin, adenosine triphosphate (ATP), pH, and morphology were determined prior to and after biotin labeling to rule out detrimental effects of the labeling procedure on the RCC.

RESULTS

Our data show that RCCs can be labeled under sterile conditions in a closed system with two different biotinylation reagent concentrations, without affecting the biological activity.

CONCLUSION

An easy, rapid (<2 hr), and robust method was developed to manufacture biotin-labeled RCCs for clinical research compliant to GPG.

In premature infants there is no decrease in 24-hour posttransfusion allogeneic red blood cell recovery after 42 days of storage

BACKGROUND

Critically ill preterm very-low-birthweight (VLBW) neonates (birthweight ≤ 1.5 kg) frequently develop anemia that is treated with red blood cell (RBC) transfusions. Although RBCs transfused to adults demonstrate progressive decreases in posttransfusion 24-hour RBC recovery (PTR₂₄ ) during storage-to a mean of approximately 85% of the Food and Drug Administration-allowed 42-day storage-limited data in infants indicate no decrease in PTR₂₄ with storage.

STUDY DESIGN AND METHODS

We hypothesized that PTR₂₄ of allogeneic RBCs transfused to anemic VLBW newborns: 1) will be greater than PTR₂₄ of autologous RBCs transfused into healthy adults and 2) will not decrease with increasing storage duration. RBCs were stored at 4°C for not more than 42 days in AS-3 or AS-5. PTR₂₄ was determined in 46 VLBW neonates using biotin-labeled RBCs and in 76 healthy adults using ⁵¹ Cr-labeled RBCs. Linear mixed-model analysis was used to estimate slopes and intercepts of PTR₂₄ versus duration of RBC storage.

RESULTS

For VLBW newborns, the estimated slope of PTR₂₄ versus storage did not decrease with the duration of storage (p = 0.18) while for adults it did (p < 0.0001). These estimated slopes differed significantly in adults compared to newborns (p = 0.04). At the allowed 42-day storage limit, projected mean neonatal PTR₂₄ was 95.9%; for adults, it was 83.8% (p = 0.0002).

CONCLUSIONS

These data provide evidence that storage duration of allogeneic RBCs intended for neonates can be increased without affecting PTR₂₄ . This conclusion supports the practice of transfusing RBCs stored up to 42 days for small-volume neonatal transfusions to limit donor exposure.

Antibodies to biotinylated red blood cells in adults and infants: improved detection, partial characterization, and dependence on red blood cell-biotin dose

BACKGROUND

Biotin-labeled red blood cells (BioRBCs) are used for in vivo kinetic studies. Because BioRBC dosing occasionally induces antibodies, a sensitive and specific anti-BioRBC detection assay is needed.

STUDY DESIGN AND METHODS

Aims were to 1) develop a gel card assay to evaluate existing, naturally occurring and BioRBC-induced plasma antibodies, 2) compare gel card and tube agglutination detection results, and 3) test for a relationship of antibody induction and BioRBC dose. Reagent BioRBCs were prepared using sulfo-NHS biotin ranging from densities 18 (BioRBC-18) to 1458 (BioRBC-1458) µg/mL RBCs.

RESULTS

Among BioRBC-exposed subjects, gel card and tube agglutination results were concordant in 21 of 22 adults and all 19 infant plasma samples. Gel card antibody detection sensitivity was more than 10-fold greater than tube agglutination. Twelve to 16 weeks after BioRBC exposure, induced anti-antibodies were detected by gel card in three of 26 adults (12%) at reagent densities BioRBC-256 or less, but in none of 41 infants. Importantly, induced anti-BioRBC antibodies were associated with higher BioRBC dose (p = 0.008); no antibodies were detected in 18 subjects who received BioRBC doses less than or equal to BioRBC-18. For noninduced BioRBC antibodies, six of 1125 naïve adults (0.3%) and none of 46 naïve infants demonstrated existing anti-BioRBC antibodies using reagent BioRBC-140 or -162. Existing anti-BioRBCs were all neutralized by biotin compounds, while induced antibodies were not.

CONCLUSIONS

The gel card assay is more sensitive than the tube agglutination assay. We recommend reagent BioRBC-256 for identifying anti-BioRBCs. Use of a low total RBC biotin label dose (≤ BioRBC-18) may minimize antibody induction.

Estimation of adult and neonatal RBC lifespans in anemic neonates using RBCs labeled at several discrete biotin densities

BACKGROUND

Prior conclusions that autologous neonatal red blood cells (RBC) have substantially shorter lifespans than allogeneic adult RBCs were not based on direct comparison of autologous neonatal vs. allogeneic adult RBCs performed concurrently in the same infant. Biotin labeling of autologous neonatal RBCs and allogeneic adult donor RBCs permits concurrent direct comparison of autologous vs. allogeneic RBC lifespan.

METHODS

RBCs from 15 allogeneic adult donors and from 15 very-low-birth-weight (VLBW) neonates were labeled at separate biotin densities and transfused simultaneously into the 15 neonates. Two mathematical models that account for the RBC differences were employed to estimate lifespans for the two RBC populations.

RESULTS

Mean ± SD lifespan for adult allogeneic RBC was 70.1 ± 19.1 d, which is substantially shorter than the 120 d lifespan of both autologous and adult allogeneic RBC in healthy adults. Mean ± SD lifespan for neonatal RBC was 54.2 ± 11.3 d, which is only about 30% shorter than that of the adult allogeneic RBCs.

CONCLUSION

This study provides evidence that extrinsic environmental factors primarily determine RBC survival (e.g., small bore of the capillaries of neonates, rate of oxygenation/deoxygenation cycles) rather than factors intrinsic to RBC.

Characterization of Anti-Dal Alloantibodies Following Sensitization of Two Dal-Negative Dogs

Since its discovery, the immunogenicity of the Dal blood type has not been further investigated. The aim of this study was to better characterize anti- Dal alloantibodies produced following sensitization of Dal-negative dogs, notably their rate of appearance, the agglutination titer over time, and their immunoglobulin class. A secondary objective was to obtain polyclonal anti- Dal alloantibodies to increase the availability of Dal blood typing. Of 100 healthy laboratory Beagles tested, 2 Dal-negative dogs were identified as recipients. Ten healthy Dal-positive dogs were investigated as potential blood donors. All dogs were extensively blood typed for DEA 1, 3, 4, 5, and 7, as well as for Dal. Then, the recipients were transfused uneventfully with 10 ml/kg of Dal-positive but otherwise compatible packed red blood cells. Posttransfusion blood samples were collected routinely over a minimum of 1 year. Using a gel column technology, anti- Dal alloantibodies were detected as early as 4 days posttransfusion and remained detectable 2 years posttransfusion, with maximum agglutination titers reached at 1 and 2 months posttransfusion. The immunoglobulin class was IgG. The immunogenicity and clinical significance of the Dal blood type were confirmed. The results support the recommendations that previously transfused dogs be crossmatched starting 4 days posttransfusion and for the animal’s lifetime. The polyclonal anti- Dal antibodies produced will allow blood typing of a significant number of dogs, especially transfused dogs facing blood incompatibilities and canine blood donors.

Quality Assessment of Established and Emerging Blood Components for Transfusion

Blood is donated either as whole blood, with subsequent component processing, or through the use of apheresis devices that extract one or more components and return the rest of the donation to the donor. Blood component therapy supplanted whole blood transfusion in industrialized countries in the middle of the twentieth century and remains the standard of care for the majority of patients receiving a transfusion. Traditionally, blood has been processed into three main blood products: red blood cell concentrates; platelet concentrates; and transfusable plasma. Ensuring that these products are of high quality and that they deliver their intended benefits to patients throughout their shelf-life is a complex task. Further complexity has been added with the development of products stored under nonstandard conditions or subjected to additional manufacturing steps (e.g., cryopreserved platelets, irradiated red cells, and lyophilized plasma). Here we review established and emerging methodologies for assessing blood product quality and address controversies and uncertainties in this thriving and active field of investigation.

Drug delivery by erythrocytes: "Primum non nocere"

Red blood cells (RBCs) are naturally capable of transporting diverse cargoes throughout the circulatory system, both loaded to their surface or within their inner volume. Starting largely from the 1970s, diverse approaches for encapsulation into, and surface coupling onto, RBCs have been investigated as potential drug delivery systems. In the last decade, these efforts have yielded diverse strategies to load drugs and nanocarriers to RBCs, and to optimize their pharmacokinetics, distribution, and effects in the body. Several formulations of donor RBCs encapsulated with enzymes and drugs are currently undergoing clinical trials for treatment of oncologic and neurologic conditions. Newer approaches include design of drugs with an affinity to circulating RBCs, encapsulation into RBCs using membrane permeating compounds, and design of hybrid drug delivery systems combining synthetic components with fragments of RBC membranes. Notwithstanding the growing enthusiasm and optimism in RBC drug delivery, in this article we discuss potentially problematic issues of this biomedical concept, especially impairment of biocompatibility of the carrier RBCs, and other adverse and unintended effects. Rigorous and systematic analysis of the cautionary aspects described in this article should be further developed and extended in order to soberly gauge the risk/benefit balance of any given RBC-based drug delivery application. While there is little doubt that RBC drug delivery will ultimately flourish, focusing research efforts on approaches that are unlikely to cause adverse effects in patients will help to sooner bring this day.

A Novel Physiology-Based Mathematical Model to Estimate Red Blood Cell Lifespan in Different Human Age Groups

Direct measurement of red blood cell (RBC) survival in humans has improved from the original accurate but limited differential agglutination technique to the current reliable, safe, and accurate biotin method. Despite this, all of these methods are time consuming and require blood sampling over several months to determine the RBC lifespan. For situations in which RBC survival information must be obtained quickly, these methods are not suitable. With the exception of adults and infants, RBC survival has not been extensively investigated in other age groups. To address this need, we developed a novel, physiology-based mathematical model that quickly estimates RBC lifespan in healthy individuals at any age. The model is based on the assumption that the total number of RBC recirculations during the lifespan of each RBC (denoted by N max) is relatively constant for all age groups. The model was initially validated using the data from our prior infant and adult biotin-labeled red blood cell studies and then extended to the other age groups. The model generated the following estimated RBC lifespans in 2-year-old, 5-year-old, 8-year-old, and 10-year-old children: 62, 74, 82, and 86 days, respectively. We speculate that this model has useful clinical applications. For example, HbA1c testing is not reliable in identifying children with diabetes because HbA1c is directly affected by RBC lifespan. Because our model can estimate RBC lifespan in children at any age, corrections to HbA1c values based on the model-generated RBC lifespan could improve diabetes diagnosis as well as therapy in children.

Adenosine monophosphate deaminase 3 activation shortens erythrocyte half-life and provides malaria resistance in mice

The factors that determine red blood cell (RBC) lifespan and the rate of RBC aging have not been fully elucidated. In several genetic conditions, including sickle cell disease, thalassemia, and G6PD deficiency, erythrocyte lifespan is significantly shortened. Many of these diseases are also associated with protection from severe malaria, suggesting a role for accelerated RBC senescence and clearance in malaria resistance. Here, we report a novel, N-ethyl-N-nitrosourea-induced mutation that causes a gain of function in adenosine 5'-monophosphate deaminase (AMPD3). Mice carrying the mutation exhibit rapid RBC turnover, with increased erythropoiesis, dramatically shortened RBC lifespan, and signs of increased RBC senescence/eryptosis, suggesting a key role for AMPD3 in determining RBC half-life. Mice were also found to be resistant to infection with the rodent malaria Plasmodium chabaudi. We propose that resistance to P. chabaudi is mediated by increased RBC turnover and higher rates of erythropoiesis during infection.

Research Opportunities to Improve Neonatal Red Blood Cell Transfusion

Red blood cell (RBC) transfusion is a common and lifesaving therapy for anemic neonates and infants, particularly among those born prematurely or undergoing surgery. However, evidence-based indications for when to administer RBCs and adverse effects of RBC transfusion on important outcomes including necrotizing enterocolitis, survival, and long-term neurodevelopmental impairment remain uncertain. In addition, blood-banking practices for preterm and term neonates and infants have been largely developed using studies from older children and adults. Use of and refinements in emerging technologies and advances in biomarker discovery and neonatal-specific RBC transfusion databases may allow clinicians to better define and tailor RBC transfusion needs and practices to individual neonates. Decreasing the need for RBC transfusion and developing neonatal-specific approaches in the preparation of donor RBCs have potential for reducing resource utilization and cost, improving outcomes, and assuring blood safety. Finally, large donor-recipient-linked cohort studies can provide data to better understand the balance of the risks and benefits of RBC transfusion in neonates. These studies may also guide the translation of new research into best practices that can rapidly be integrated into routine care. This review highlights key opportunities in transfusion medicine and neonatology for improving the preparation and transfusion of RBCs into neonates and infants. We focus on timely, currently addressable knowledge gaps that can increase the safety and efficacy of preterm and term neonatal and infant RBC transfusion practices.

Hemolysis in Preterm Neonates

Hemolysis can be an important cause of hyperbilirubinemia in premature and term neonates. It can result from genetic abnormalities intrinsic to or factors exogenous to normal to red blood cells (RBCs). Hemolysis can lead to a relatively rapid increase in total serum/plasma bilirubin, hyperbilirubinemia that is somewhat slow to fall with phototherapy, or hyperbilirubinemia that is likely to rebound after phototherapy. Laboratory methods for diagnosing hemolysis are more difficult to apply, or less conclusive, in preterm infants. Transfusion of donor RBCs can present a bilirubin load that must be metabolized. Genetic causes can be identified by next-generation sequencing panels.

Clearance of stored red blood cells is not increased compared with fresh red blood cells in a human endotoxemia model

BACKGROUND

It is thought that the clearance of transfused red blood cells (RBCs) is related both to the storage time of the transfusion product and to the inflammatory status of the recipient. We investigated these effects in a randomized, "two-hit," healthy volunteer transfusion model, comparing autologous RBCs that were stored for 35 days with those that were stored for 2 days.

STUDY DESIGN AND METHODS

Healthy male volunteers donated 1 unit of autologous RBCs either 2 days (2D) or 35 days (35D) before the study date. The experiment was started by infusion of 2 ng/kg lipopolysaccharide ("first hit"). Two hours later, the stored RBCs ("second hit") were reinfused, followed by the labeling of RBCs with biotin. Clearance of biotin-labeled RBCs (BioRBCs) was measured during the 5-hour posttransfusion endotoxemia period along with measurements of phosphatidylserine (PS) exposure, lactadherin binding, and expression of CD47 (cluster of differentiation 47; a transmembrane protein encoded by the CD47 gene).

RESULTS

In the 2D stored RBCs group, 1.5% ± 3.4% of infused BioRBCs were cleared from the circulation 5 hours posttransfusion versus 4.8% ± 4.0% in the 35D stored RBCs group (p = 0.1). There were no differences in PS exposure, lactadherin binding, or CD47 expression between fresh and stored RBCs or between pretransfusion and posttransfusion measurements.

CONCLUSION

Our study shows a low clearance of RBCs even during endotoxemia. Furthermore, short-term clearance of BioRBCs during endotoxemia was not related to storage duration. Consistent with these observations, PS exposure, lactadherin binding, and CD47 expression did not differ between 2D and 35D stored cells before or after transfusion. We conclude that, in the presence of endotoxemia, clearance of 35D stored autologous RBCs is not increased compared with 2D stored fresh RBCs.

A Mass Balance-Based Semiparametric Approach to Evaluate Neonatal Erythropoiesis

Postnatal hemoglobin (Hb) production in anemic preterm infants is determined by several factors including the endogenous erythropoietin levels, allogeneic RBC transfusions administered to treat anemia, and developmental age. As a result, their postnatal Hb production rate can vary considerably. This work introduces a novel Hb mass balance-based semiparametric approach that utilizes infant blood concentrations of Hb from the first 30 postnatal days to estimate the amount of Hb produced and the erythropoiesis rate in newborn infants. The proposed method has the advantage of not relying on specific structural pharmacodynamic model assumptions to describe the Hb production, but instead utilizes simple mass balance principles and nonparametric regression analysis. The developed method was applied to the Hb data from 79 critically ill anemic very low birth weight preterm infants to evaluate the dynamic changes in erythropoiesis during the first month of life and to determine the inter-subject variability in Hb production. The estimated mean (±SD) cumulative amount of Hb produced by the infants over the first month of life was 6.6 ± 3.4 g (mean body weight, 0.768 kg), and the mean estimated body weight-scaled Hb production rate over the same period was 0.23 ± 0.12 g/day/kg. A significant positive correlation was observed between infant gestational age and the mean body weight-scaled Hb production rate over the first month of life (P < 0.05). We conclude that the proposed mathematical approach and its implementation provide a flexible framework to evaluate postnatal erythropoiesis in newborn infants.

Hemolytic Disorders Causing Severe Neonatal Hyperbilirubinemia

A shortened erythrocyte life span, because of hemolytic disorders, is a common cause of extreme neonatal hyperbilirubinemia. Clinical and laboratory examinations can frequently identify the underlying cause of extreme neonatal hyperbilirubinemia. In this article, several tests, techniques, and approaches have been reviewed, including red blood cell morphology assessment, end-tidal carbon monoxide quantification, eosin-5-maleimide flow cytometry, as well as next-generation DNA sequencing using neonatal jaundice panels.

Modulation of red blood cell population dynamics is a fundamental homeostatic response to disease

Increased red blood cell (RBC) volume variation (RDW) has recently been shown to predict a wide range of mortality and morbidity: death due to cardiovascular disease, cancer, infection, renal disease, and more; complications in heart failure and coronary artery disease, advanced stage and worse prognosis in many cancers, poor outcomes in autoimmune disease, and many more. The mechanisms by which all of these diseases lead to increased RDW are unknown. Here we use a semi-mechanistic mathematical model of in vivo RBC population dynamics to dissect the factors controlling RDW and show that elevated RDW results largely from a slight reduction in the in vivo rate of RBC turnover. RBCs become smaller as they age, and a slight reduction in the rate of RBC turnover allows smaller cells to continue circulating, expanding the low-volume tail of the RBC population's volume distribution, and thereby increasing RDW. Our results show that mildly extended RBC lifespan is a previously unrecognized homeostatic adaptation common to a very wide range of pathologic states, likely compensating for subtle reductions in erythropoietic output. A mathematical model-based estimate of the clearance rate may provide a novel early-warning biomarker for a wide range of morbidity and mortality.

Red blood cell population dynamics

Hematology analyzers provide a static snapshot of the circulating population of red blood cells (RBCs). The RBC population is rapidly changing, with more than 2 million RBCs turning over every second in the typical healthy adult. The static snapshot provided by the complete blood count does not capture many of the dynamic aspects of this population, such as the rate of RBC maturation and the rate of RBC turnover. By integrating basic science with hematology analyzer measurements, it is possible to estimate the rates of these dynamic processes, yielding new insights into human physiology, with potential diagnostic application.