A Comparative Study of the Effect of Leukoreduction and Pre-storage Leukodepletion on Red Blood Cells during Storage

Effect of leukoreduction on the omics phenotypes of canine packed red blood cells during refrigerated storage

BACKGROUND

Red blood cell (RBC) storage promotes biochemical and morphological alterations, collectively referred to as storage lesions (SLs). Studies in humans have identified leukoreduction (LR) as a critical processing step that mitigates SLs. To date no study has evaluated the impact of LR on metabolic SLs in canine blood units using omics technologies.

OBJECTIVE

Compare the lipid and metabolic profiles of canine packed RBC (pRBC) units as a function of LR in fresh and stored refrigerated (up to 42 days) units.

ANIMALS

Packed RBC units were obtained from 8 donor dogs enrolled at 2 different Italian veterinary blood banks.

STUDY DESIGN AND METHODS

Observational study. A volume of 450 mL of whole blood was collected using Citrate-Phosphate-Dextrose-Saline-Adenine-Glucose-Mannitol (CPD-SAGM) transfusion bags with a LR filter to produce 2 pRBC units for each donor, without (nLR-pRBC) and with (LR-pRBC) LR. Units were stored in the blood bank at 4 ± 2°C. Sterile weekly samples were obtained from each unit for omics analyses.

RESULTS

A significant effect of LR on fresh and stored RBC metabolic phenotypes was observed. The nLR-pRBC were characterized by higher concentrations of free short and medium-chain fatty acids, carboxylic acids (pyruvate, lactate), and amino acids (arginine, cystine). The LR-pRBC had higher concentrations of glycolytic metabolites, high energy phosphate compounds (adenosine triphosphate [ATP]), and antioxidant metabolites (pentose phosphate, total glutathione).

CONCLUSION AND CLINICAL IMPORTANCE

Leukoreduction decreases the metabolic SLs of canine pRBC by preserving energy metabolism and preventing oxidative lesions.

Regulation of kynurenine metabolism by blood donor genetics and biology impacts red cell hemolysis in vitro and in vivo

ABSTRACT

In the field of transfusion medicine, the clinical relevance of the metabolic markers of the red blood cell (RBC) storage lesion is incompletely understood. Here, we performed metabolomics of RBC units from 643 donors enrolled in the Recipient Epidemiology and Donor Evaluation Study, REDS RBC Omics. These units were tested on storage days 10, 23, and 42 for a total of 1929 samples and also characterized for end-of-storage hemolytic propensity after oxidative and osmotic insults. Our results indicate that the metabolic markers of the storage lesion poorly correlated with hemolytic propensity. In contrast, kynurenine was not affected by storage duration and was identified as the top predictor of osmotic fragility. RBC kynurenine levels were affected by donor age and body mass index and were reproducible within the same donor across multiple donations from 2 to 12 months apart. To delve into the genetic underpinnings of kynurenine levels in stored RBCs, we thus tested kynurenine levels in stored RBCs on day 42 from 13 091 donors from the REDS RBC Omics study, a population that was also genotyped for 879 000 single nucleotide polymorphisms. Through a metabolite quantitative trait loci analysis, we identified polymorphisms in SLC7A5, ATXN2, and a series of rate-limiting enzymes (eg, kynurenine monooxygenase, indoleamine 2,3-dioxygenase, and tryptophan dioxygenase) in the kynurenine pathway as critical factors affecting RBC kynurenine levels. By interrogating a donor-recipient linkage vein-to-vein database, we then report that SLC7A5 polymorphisms are also associated with changes in hemoglobin and bilirubin levels, suggestive of in vivo hemolysis in 4470 individuals who were critically ill and receiving single-unit transfusions.

Assessment of stored red blood cells through lab-on-a-chip technologies for precision transfusion medicine

Transfusion of red blood cells (RBCs) is one of the most valuable and widespread treatments in modern medicine. Lifesaving RBC transfusions are facilitated by the cold storage of RBC units in blood banks worldwide. Currently, RBC storage and subsequent transfusion practices are performed using simplistic workflows. More specifically, most blood banks follow the "first-in-first-out" principle to avoid wastage, whereas most healthcare providers prefer the "last-in-first-out" approach simply favoring chronologically younger RBCs. Neither approach addresses recent advances through -omics showing that stored RBC quality is highly variable depending on donor-, time-, and processing-specific factors. Thus, it is time to rethink our workflows in transfusion medicine taking advantage of novel technologies to perform RBC quality assessment. We imagine a future where lab-on-a-chip technologies utilize novel predictive markers of RBC quality identified by -omics and machine learning to usher in a new era of safer and precise transfusion medicine.

Hypoxic storage of murine red blood cells improves energy metabolism and post-transfusion recoveries

BACKGROUND

The Red blood cell (RBC) storage lesion results in decreased circulation and function of transfused RBCs. Elevated oxidant stress and impaired energy metabolism are a hallmark of the storage lesion in both human and murine RBCs. Although human studies don't suffer concerns that findings may not translate, they do suffer from genetic and environmental variability amongst subjects. Murine models can control for genetics, environment, and much interventional experimentation can be carried out in mice that is neither technically feasible nor ethical in humans. However, murine models are only useful to the extent that they have similar biology to humans. Hypoxic storage has been shown to mitigate the storage lesion in human RBCs, but has not been investigated in mice.

MATERIALS AND METHODS

RBCs from a C57BL6/J mouse strain were stored under normoxic (untreated) or hypoxic conditions (SO2 ~ 26%) for 1h, 7 and 12 days. Samples were tested for metabolomics at steady state, tracing experiments with 1,2,3-¹³C₃-glucose, proteomics and end of storage post transfusion recovery.

RESULTS

Hypoxic storage improved post-transfusion recovery and energy metabolism, including increased steady state and ¹³C₃-labeled metabolites from glycolysis, high energy purines (adenosine triphosphate) and 2,3-diphospholgycerate. Hypoxic storage promoted glutaminolysis, increased glutathione pools, and was accompanied by elevation in the levels of free fatty acids and acyl-carnitines.

DISCUSSION

This study isolates hypoxia, as a single independent variable, and shows similar effects as seen in human studies. These findings also demonstrate the translatability of murine models for hypoxic RBC storage and provide a pre-clinical platform for ongoing study.

Comparison of Two Alternative Procedures to Obtain Packed Red Blood Cells for β-Thalassemia Major Transfusion Therapy

β-thalassemia major (βTM) patients require frequent blood transfusions, with consequences that span from allogenic reactions to iron overload. To minimize these effects, βTM patients periodically receive leucodepleted packed red blood cells (P-RBCs) stored for maximum 14 days. The aim of this study was to compare two alternative routine procedures to prepare the optimal P-RBCs product, in order to identify differences in their content that may somehow affect patients’ health and quality of life (QoL). In method 1, blood was leucodepleted and then separated to obtain P-RBCs, while in method 2 blood was separated and leucodepleted after removal of plasma and buffycoat. Forty blood donors were enrolled in two independent centers; couples of phenotypically matched whole blood units were pooled, divided in two identical bags and processed in parallel following the two methods. Biochemical properties, electrolytes and metabolic composition were tested after 2, 7 and 14 days of storage. Units prepared with both methods were confirmed to have all the requirements necessary for βTM transfusion therapy. Nevertheless, RBCs count and Hb content were found to be higher in method-1, while P-RBCs obtained with method 2 contained less K⁺, iron and storage lesions markers. Based on these results, both methods should be tested in a clinical perspective study to determine a possible reduction of transfusion-related complications, improving the QoL of βTM patients, which often need transfusions for the entire lifespan.

Decrease in the Risk of Posttransplant Hepatocellular Carcinoma Recurrence After the Conversion to Prestorage Leukoreduction for Transfused Red Blood Cells

BACKGROUND

Prestorage leukoreduction has the advantage over poststorage leukoreduction in reducing leukocyte-derived molecules in red blood cells (RBC) unit, which induce immunomodulation. Our institution newly introduced prestorage leukoreduction, instead of conventional poststorage leukoreduction, for liver transplant recipients since March 2012. In this study, we aimed to evaluate the risk of posttransplant hepatocellular carcinoma (HCC) recurrence after the conversion of poststorage leukoreduction into prestorage leukoreduction for transfused allogeneic RBCs.

METHODS

Among 220 patients who underwent living-donor liver transplantation for HCC, 83 of 113 who received only poststorage-leukoreduced RBCs were matched with 83 of 107 who received only prestorage-leukoreduced RBCs using 1:1 propensity score matching based on factors like tumor biology. The primary outcome was overall HCC recurrence. Survival analysis was performed with death as a competing risk event.

RESULTS

In the matched cohort, recurrence probability at 1, 2, and 5 years posttransplant was 9.6%, 15.6%, and 18.1% in prestorage group and 15.6%, 21.6%, and 33.7% in poststorage group (hazard ratio [HR], 0.52; 0.28-0.97; P = 0.040). Multivariable analysis confirmed a significance of prestorage leukoreduction (HR, 0.29; 0.15-0.59; P < 0.001). Overall death risk was also lower with prestorage leukoreduction (HR, 0.51; 0.26-0.99; P = 0.049). In subgroup analysis for the unmatched cohort, recurrence risk was significantly lower in prestorage group within the patients who underwent surgery 2 years (HR, 0.24; 0.10-0.61; P = 0.002), 1 year (HR, 0.16; 0.03-0.92; P = 0.040), and 6 months (HR, 0.13; 0.02-0.85; P = 0.034), respectively, before and after the conversion to prestorage leukoreduction.

CONCLUSIONS

Our findings suggest a potential benefit of prestorage leukoreduction in reducing the risk of HCC recurrence in liver transplant recipients who received allogeneic RBCs during the perioperative period.

The Effects of Pre-Storage Leukoreduction on the Conservation of Bovine Whole Blood in Plastic Bags

Simple Summary

Blood transfusion is a life-saving veterinary therapeutic procedure. While fractionated blood components are used in humans, whole blood is most commonly used in animals, especially for farm animals. Whole blood contains white blood cells that can cause a transfusion reaction in animals. Here, we proposed that using a blood bag with leukocyte filtration is sufficient for blood conservation under field conditions and thus can be an option for transfusion medicine in the case of farm animals. The filtered bag was efficient in removing white cells from cattle whole blood and could be used under field conditions. Blood stored after white blood cells were removed showed less acidic load. Further experimental studies are required to prove that blood without white cells results in a decrease in transfusion reactions in cattle.

Abstract

Leukoreduction (LR) is a technique that consists of reducing the number of leukocytes in whole blood or blood components that can contribute to decreasing storage lesions and the occurrence of post-transfusion complications. We propose that using a blood bag with pre-storage leukocyte filtration is sufficient for blood conservation under field conditions. Ten healthy Nelore cows were used. Whole blood was sampled from each animal and stored at 2 to 6 °C in CPD/SAG-M (citrate phosphate dextrose bag with a saline, adenine, glucose, mannitol satellite bag) triple bags (Control) and in CPD/SAG-M quadruple bags with a leukocyte filter (Filter). At baseline and after 7, 14, 21, 28, 35, and 42 days (D0, D7, D14, D21, D28, D35, and D42, respectively), complete hematological, blood gas, and biochemical evaluations were determined. The filtered bag removed 99.3% of white blood cells from cattle blood, and the entire filtration process was performed in the field. There was a reduction in the number of red blood cells (RBCs) in both groups from D14 onward, with a decrease of 19.7% and 17.1% at D42 for the Control and Filter bags, respectively. The hemoglobin (Hb) concentration had variation in both groups. Potassium, pO₂, pCO₂, and sO₂ increased, and sodium, bicarbonate, and pH decreased during storage. The filtered bag was efficient in removing white cells from cattle whole blood and could be used under field conditions. Blood stored after LR showed differences (p < 0.05) in blood gas analysis towards a better quality of stored blood (e.g., higher pH, lower pCO₂, higher sO₂). Further experimental studies are required to prove that blood without white cells results in a decrease in transfusion reactions in cattle.

Inter-donor variability in deformability of red blood cells in blood units

OBJECTIVE

This study aimed to examine the donor-to-donor variability in the deformability of red blood cells (RBCs) from freshly collected blood donations (F-RBC) and packed RBCs.

BACKGROUND

Packed RBCs are supplied for transfusion by the first-in-first-out (FIFO) criterion, assuming that their quality is the same for packed RBCs with equal storage duration. To challenge this notion, we determined the deformability of F-RBC and packed RBCs stored for different durations.

METHODS

Three RBC groups were employed: A. 79 samples of F-RBC; B. 76 samples of packed RBC units, randomly used for transfusion at different storage durations; and C. 65 samples of outdated packed RBCs stored for 35 to 37 days. All packed RBC units were non-leukofiltrated and stored in Citrate-phosphate-dextrose solution with adenine (CPDA-1). RBC deformability was determined using a computerised cell-flow properties analyser, which monitors the shape change of cells directly visualised in a narrow-gap flow chamber and provides the cells' deformability distribution in a large RBC population.

RESULTS

The F-RBC deformability exhibited a wide-range inter-donor variability. The cold storage of packed RBCs exerted a mild reduction of deformability, which became significant, compared to the initial inter-donor variability, only after 3 weeks of storage.

CONCLUSION

Packed RBCs are generally supplied for transfusion by the FIFO criterion based on the assumption that the storage duration is a key factor of RBC quality. This study demonstrates that the deformability of red blood cells is significantly different in donors, and substantial variability persists throughout the entire process of their storage. Therefore, the FIFO criterion is not sufficient for assessing the RBC deformability, which should, therefore, be specifically characterised for each unit.

Red blood cell metabolism in Rhesus macaques and humans: comparative biology of blood storage

Macaques are emerging as a critical animal model in transfusion medicine, because of their evolutionary similarity to humans and perceived utility in discovery and translational science. However, little is known about the metabolism of Rhesus macaque red blood cells (RBC) and how this compares to human RBC metabolism under standard blood banking conditions. Metabolomic and lipidomic analyses, and tracing experiments with [1,2,3-¹³C₃]glucose, were performed using fresh and stored RBC (sampled weekly until storage day 42) obtained from Rhesus macaques (n=20) and healthy human volunteers (n=21). These results were further validated with targeted quantification against stable isotope-labeled internal standards. Metabolomic analyses demonstrated inter-species differences in RBC metabolism independent of refrigerated storage. Although similar trends were observed throughout storage for several metabolic pathways, species- and sex-specific differences were also observed. The most notable differences were in glutathione and sulfur metabolites, purine and lipid oxidation metabolites, acylcarnitines, fatty acyl composition of several classes of lipids (including phosphatidylserines), glyoxylate pathway intermediates, and arginine and carboxylic acid metabolites. Species-specific dietary and environmental compounds were also detected. Overall, the results suggest an increased basal and refrigerator-storage-induced propensity for oxidant stress and lipid remodeling in Rhesus macaque RBC cells, as compared to human red cells. The overlap between Rhesus macaque and human RBC metabolic phenotypes suggests the potential utility of a translational model for simple RBC transfusions, although inter-species storage-dependent differences need to be considered when modeling complex disease states, such as transfusion in trauma/hemorrhagic shock models.

Donor glucose-6-phosphate dehydrogenase deficiency decreases blood quality for transfusion

BACKGROUNDGlucose-6-phosphate dehydrogenase (G6PD) deficiency decreases the ability of red blood cells (RBCs) to withstand oxidative stress. Refrigerated storage of RBCs induces oxidative stress. We hypothesized that G6PD-deficient donor RBCs would have inferior storage quality for transfusion as compared with G6PD-normal RBCs.METHODSMale volunteers were screened for G6PD deficiency; 27 control and 10 G6PD-deficient volunteers each donated 1 RBC unit. After 42 days of refrigerated storage, autologous 51-chromium 24-hour posttransfusion RBC recovery (PTR) studies were performed. Metabolomics analyses of these RBC units were also performed.RESULTSThe mean 24-hour PTR for G6PD-deficient subjects was 78.5% ± 8.4% (mean ± SD), which was significantly lower than that for G6PD-normal RBCs (85.3% ± 3.2%; P = 0.0009). None of the G6PD-normal volunteers (0/27) and 3 G6PD-deficient volunteers (3/10) had PTR results below 75%, a key FDA acceptability criterion for stored donor RBCs. As expected, fresh G6PD-deficient RBCs demonstrated defects in the oxidative phase of the pentose phosphate pathway. During refrigerated storage, G6PD-deficient RBCs demonstrated increased glycolysis, impaired glutathione homeostasis, and increased purine oxidation, as compared with G6PD-normal RBCs. In addition, there were significant correlations between PTR and specific metabolites in these pathways.CONCLUSIONBased on current FDA criteria, RBCs from G6PD-deficient donors would not meet the requirements for storage quality. Metabolomics assessment identified markers of PTR and G6PD deficiency (e.g., pyruvate/lactate ratios), along with potential compensatory pathways that could be leveraged to ameliorate the metabolic needs of G6PD-deficient RBCs.TRIAL REGISTRATIONClinicalTrials.gov NCT04081272.FUNDINGThe Harold Amos Medical Faculty Development Program, Robert Wood Johnson Foundation grant 71590, the National Blood Foundation, NIH grant UL1 TR000040, the Webb-Waring Early Career Award 2017 by the Boettcher Foundation, and National Heart, Lung, and Blood Institute grants R01HL14644 and R01HL148151.

Hypoxic storage of red blood cells improves metabolism and post-transfusion recovery

BACKGROUND

Blood transfusion is a lifesaving intervention for millions of recipients worldwide every year. Storing blood makes this possible but also promotes a series of alterations to the metabolism of the stored erythrocyte. It is unclear whether the metabolic storage lesion is correlated with clinically relevant outcomes and whether strategies aimed at improving the metabolic quality of stored units, such as hypoxic storage, ultimately improve performance in the transfused recipient.

STUDY DESIGN AND METHODS

Twelve healthy donor volunteers were recruited in a two-arm cross-sectional study, in which each subject donated 2 units to be stored under standard (normoxic) or hypoxic conditions (Hemanext technology). End-of-storage measurements of hemolysis and autologous posttransfusion recovery (PTR) were correlated to metabolomics measurements at Days 0, 21, and 42.

RESULTS

Hypoxic red blood cells (RBCs) showed superior PTR and comparable hemolysis to donor-paired standard units. Hypoxic storage improved energy and redox metabolism (glycolysis and 2,3-diphosphoglycerate), improved glutathione and methionine homeostasis, decreased purine oxidation and membrane lipid remodeling (free fatty acid levels, unsaturation and hydroxylation, acyl-carnitines). Intra- and extracellular metabolites in these pathways (including some dietary purines) showed significant correlations with PTR and hemolysis, though the degree of correlation was influenced by sulfur dioxide (SO₂ ) levels.

CONCLUSION

Hypoxic storage improves energy and redox metabolism of stored RBCs, which results in improved posttransfusion recoveries in healthy autologous recipients-a Food and Drug Administration gold standard of stored blood quality. In addition, we identified candidate metabolic predictors of PTR for RBCs stored under standard and hypoxic conditions.

Extracellular Vesicles in Red Blood Cell Concentrates: An Overview

Red blood cell (RBC) concentrates may be stored for up to 42 days before transfusion to a patient. During storage extracellular vesicles (EVs) develop and can be detected in significant amounts in RBC concentrates. The concentration of EVs is affected by component preparation methods, storage solutions, and inter-donor variation. Laboratory investigations have focused on the effect of EVs on in vitro assays of thrombin generation and immune responses. Assays for EVs in RBC concentrates are not standardized. The aims of this review are to describe the factors that determine the presence of erythrocyte-EVs in RBC concentrates, the current techniques used to characterize them, and the potential role of EV analysis as a quality control maker for RBC storage.

Red cell distribution width predicts out of hospital outcomes in critically ill emergency general surgery patients

Introduction

Red cell distribution width (RDW) is associated with mortality and bloodstream infection risk in critically ill patients. We hypothesized that an increase in RDW at hospital discharge in critically ill patients who received emergency general surgery (EGS) would be associated with increased mortality after hospital discharge.

Methods

We performed a two-center observational study of patients treated in medical and surgical intensive care units. We studied 1567 patients, who received critical care between 1998 and 2012 who underwent EGS and survived hospitalization. The exposure of interest was RDW within 24 hours of hospital discharge and categorized a priori in quintiles as ≤13.3%, 13.3% to 14.0%, 14.0% to 14.7%, 14.7% to 15.8%, 15.8% to 17.0% and >17.0%. The primary outcome was 90-day all-cause mortality. Adjusted ORs were estimated by multivariable logistic regression models with inclusion of covariate terms for age, race, gender, Deyo-Charlson Index, sepsis and number of organs with acute failure.

Results

The cohort patients were 51.4% male and 23.2% non-white. 23.9% had sepsis and the mean age was 58 years. 90-day postdischarge mortality was 6.8%. Patients with a discharge RDW 15.8% to 17.0% or RDW >17.0% have an adjusted OR of 90-day postdischarge mortality of 3.64 (95% CI 1.04 to 12.68; p=0.043) or 4.58 (95% CI 1.32 to 15.93; p=0.02), respectively, relative to patients with a discharge RDW ≤13.3%. Further, patients with a discharge RDW ≥15.8 have an adjusted OR of 30-day hospital readmission of 2.12 (95% CI 1.17 to 3.83; p=0.013) relative to patients with a discharge RDW ≤13.3%.

Conclusions

In EGS patients requiring critical care who survive hospitalization, an elevated RDW at the time of discharge is a robust predictor of all-cause patient mortality and hospital readmission after discharge.

Level of evidence

Level II, prognostic retrospective study.

Leukoreduction of packed red blood cells attenuates proinflammatory properties of storage-derived microvesicles

BACKGROUND

Leukoreduction prior to packed red blood cell (pRBC) storage is not a universally accepted practice. Our laboratory has previously shown that microvesicles (MVs) accumulate in pRBC units during storage and play an important role in lung injury after resuscitation. Currently, the effect of leukoreduction on MV formation in stored pRBC units is unknown. In the present study, we investigated the hypothesis that leukoreduction of pRBC units prior to storage would attenuate the production of MVs and decrease pulmonary inflammation after hemorrhage and resuscitation.

METHODS

Leukoreduced and nonleukoreduced pRBC units were prepared from human donors and C57/Bl6 mice and stored for up to 42 d and 14 d, respectively. At intervals during storage, MVs were isolated from pRBC units, quantified and characterized based on size, morphology, and levels of proinflammatory cytokines. In additional experiments, mice underwent controlled hemorrhage followed by resuscitation with normal saline (NS) with or without equal numbers of MVs isolated from leukoreduced or nonleukoreduced stored mouse pRBC. Histologic lung sections were evaluated for the presence of tissue edema and inflammatory cells.

RESULTS

For both human and mouse pRBCs, the number of MVs significantly increased throughout the storage period. There were significantly fewer MVs present in leukoreduced units. The average MV size significantly increased over time and was similar between groups. Levels of interleukin 1α (IL-1α), regulated on activation, normal T cell expressed and secreted (RANTES), and macrophage-derived chemokine (MDC) were lower in MVs from leukoreduced pRBC units as compared with MVs from nonleukoreduced units. Hemorrhaged mice resuscitated with NS with the addition of MV from leukoreduced pRBC demonstrated significantly less pulmonary edema and inflammatory cell recruitment as compared to those resuscitated with NS with the addition of MV from nonleukoreduced pRBC.

CONCLUSIONS

Prestorage leukoreduction of pRBC units reduces the formation and proinflammatory properties of MV, which in turn decreases lung injury secondary to MV from stored pRBC units after hemorrhage and resuscitation.

N-acetylcysteine improves the quality of red blood cells stored for transfusion

Storage inflicts a series of changes on red blood cells (RBC) that compromise the cell survival and functionality; largely these alterations (storage lesions) are due to oxidative modifications. The possibility of improving the quality of packed RBC stored for transfusion including N-acetylcysteine (NAC) in the preservation solution was explored. Relatively high concentrations of NAC (20-25 mM) were necessary to prevent the progressive leakage of hemoglobin, while lower concentrations (≥2.5 mM) were enough to prevent the loss of reduced glutathione during the first 21 days of storage. Peroxiredoxin-2 was also affected during storage, with a progressive accumulation of disulfide-linked dimers and hetero-protein complexes in the cytosol and also in the membrane of stored RBC. Although the presence of NAC in the storage solution was unable to avoid the formation of thiol-mediated protein complexes, it partially restored the capacity of the cell to metabolize H₂O₂, indicating the potential use of NAC as an additive in the preservation solution to improve RBC performance after transfusion.

Duration of red blood cell storage and inflammatory marker generation

Red blood cell (RBC) transfusion is a life-saving treatment for several pathologies. RBCs for transfusion are stored refrigerated in a preservative solution, which extends their shelf-life for up to 42 days. During storage, the RBCs endure abundant physicochemical changes, named RBC storage lesions, which affect the overall quality standard, the functional integrity and in vivo survival of the transfused RBCs. Some of the changes occurring in the early stages of the storage period (for approximately two weeks) are reversible but become irreversible later on as the storage is extended. In this review, we aim to decipher the duration of RBC storage and inflammatory marker generation. This phenomenon is included as one of the causes of transfusion-related immunomodulation (TRIM), an emerging concept developed to potentially elucidate numerous clinical observations that suggest that RBC transfusion is associated with increased inflammatory events or effects with clinical consequence.

Omics markers of the red cell storage lesion and metabolic linkage

The introduction of omics technologies in the field of Transfusion Medicine has significantly advanced our understanding of the red cell storage lesion. While the clinical relevance of such a lesion is still a matter of debate, quantitative and redox proteomics approaches, as well quantitative metabolic flux analysis and metabolic tracing experiments promise to revolutionise our understanding of the role of blood processing strategies, inform the design and testing of novel additives or technologies (such as pathogen reduction), and evaluate the clinical relevance of donor and recipient biological variability with respect to red cell storability and transfusion outcomes. By reviewing existing literature in this rapidly expanding research endeavour, we highlight for the first time a correlation between metabolic markers of the red cell storage age and protein markers of haemolysis. Finally, we introduce the concept of metabolic linkage, i.e. the appreciation of a network of highly correlated small molecule metabolites which results from biochemical constraints of erythrocyte metabolic enzyme activities. For the foreseeable future, red cell studies will advance Transfusion Medicine and haematology by addressing the alteration of metabolic linkage phenotypes in response to stimuli, including, but not limited to, storage additives, enzymopathies (e.g. glucose 6-phosphate dehydrogenase deficiency), hypoxia, sepsis or haemorrhage.