Osmotic Gradient Ektacytometry Research Articles

Osmotic gradient ektacytometry – a novel diagnostic approach for neuroacanthocytosis syndromes

Osmotic gradient ektacytometry – a novel diagnostic approach for neuroacanthocytosis syndromes

Modification of deglycerolization procedure improves processing and post-thaw quality of cryopreserved sickle trait red cell concentrates

Red blood cell (RBC) transfusion is a critical therapy for those with sickle cell disease (SCD). Alloimmunization is frequent for those with SCD and may limit the availability of matched RBC. Cryopreserved RBCs, from family members or donors with a similar RBC antigen profile could provide a viable alternative to avoid further alloimmunization and prevent hemolytic transfusion-related events. However, cryopreserved SCD and Sickle Cell trait (S-trait) donor RBC units suffer from reduced recovery following deglycerolization. This study proposes and tests a modified deglycerolization protocol using an automated cell processor to mitigate RBC loss. Six red cell concentrates (RCC) from donors with S-trait and six control RCCs were glycerolized, frozen (<−65 °C) and deglycerolized on the ACP 215 using modified parameters (decreased hypertonic solution flow rate (100 mL/min) and hypertonic equilibration delay (120 s), and increased NaCl dilution volumes (500 mL). Quality testing included: hematocrit (HCT), hemolysis, indices, extracellular potassium, morphology, osmotic fragility, osmotic gradient ektacytometry, hemoglobin (HGB), and recovery. Canadian standards (CS) indicate that acceptable deglycerolized units for transfusion require a HCT ≤0.80 L/L, HGB ≥35 g/unit, and hemolysis <0.8 % in 90 % of units tested. No significant differences in HGB or RBC recovery were observed between study groups. Significant differences between study groups were identified in osmotic fragility and osmotic gradient ektacytometry parameters. Of the 6 S-trait RCCs, 3/6 units were within the HCT, HGB and hemolysis thresholds set by the CS. The modified deglycerolization protocol provides a path for the routine cryopreservation of S-trait RBCs.

SARS-CoV-2 Infection and Anemia-A Focus on RBC Deformability and Membrane Proteomics-Integrated Observational Prospective Study.

The multifaceted impact of COVID-19 extends beyond the respiratory system, encompassing intricate interactions with various physiological systems. This study elucidates the potential association between SARS-CoV-2 infection and anemia, with a particular emphasis on the deformability of red blood cells (RBCs), stability of hemoglobin, enzymatic activities, and proteomic profiles. The study encompasses a cohort of 74 individuals, including individuals positive for COVID-19, a control group, and patients with other viral infections to discern the specific effects attributable to COVID-19. The analysis of red blood cells was focused on deformability measured by osmotic gradient ektacytometry, hemoglobin stability, and glycolytic enzyme activity. Furthermore, membrane proteins were examined using advanced proteomics techniques to capture molecular-level changes. Findings from the study suggest a correlation between anemia and exacerbated outcomes in COVID-19 patients, marked by significant elevations in d-dimer, serum procalcitonin, creatinine, and blood urea nitrogen (BUN) levels. These observations suggest that chronic kidney disease (CKD) may play a role in the development of anemia in COVID-19 patients, particularly those of advanced age with comorbidities. Furthermore, the proteomic analyses have highlighted a complex relationship between omics data and RBC parameters, enriching our understanding of the mechanisms underlying the disease. This research substantiates the complex interrelationship between COVID-19 and anemia, with a specific emphasis on the potential repercussions of SARS-CoV-2 infection on RBCs. The findings contribute to the growing body of evidence supporting the extensive impact of COVID-19 on RBCs.

A novel composition of endogenous metabolic modulators improves red blood cell properties in sickle cell disease.

The most common forms of sickle cell disease (SCD) are sickle cell anemia (SCA; HbSS) and HbSC disease. In both, especially the more dense, dehydrated and adherent red blood cells (RBCs) with reduced deformability are prone to hemolysis and sickling, and thereby vaso-occlusion. Based on plasma amino acid profiling in SCD, a composition of 10 amino acids and derivatives (RCitNacQCarLKHVS; Axcella Therapeutics, USA), referred to as endogenous metabolic modulators (EMMs), was designed to target RBC metabolism. The effects of ex vivo treatment with the EMM composition on different RBC properties were studied in SCD (n=9 SCA, n=5 HbSC disease). Dose-dependent improvements were observed in RBC hydration assessed by hemocytometry (MCV, MCHC, dense RBCs) and osmotic gradient ektacytometry (Ohyper). Median (interquartile range [IQR]) increase in Ohyper compared to vehicle was 4.9% (4.0%-5.5%), 7.5% (6.9%-9.4%), and 12.8% (11.5%-14.0%) with increasing 20×, 40×, and 80X concentrations, respectively (all p<0.0001). RBC deformability (EImax using oxygen gradient ektacytometry) increased by 8.1% (2.2%-12.1%; p=0.0012), 9.6% (2.9%-15.1%; p=0.0013), and 13.3% (5.7%-25.5%; p=0.0007), respectively. Besides, RBC adhesion to subendothelial laminin decreased by 43% (6%-68%; p=0.4324), 58% (48%-72%; p=0.0185), and 71% (49%-82%; p=0.0016), respectively. Together, these results provide a rationale for further studies with the EMM composition targeting multiple RBC properties in SCD.

Defining Hereditary Pyropoikilocytosis (HPP) in the Molecular Diagnostic Era

Misconceptions continue in distinguishing hereditary elliptocytosis (HE) with hemolysis in early perinatal period and hereditary pyropoikilocytosis (HPP). In 1975, Zarkowsky and colleagues described a group of children with transfusion dependent congenital hemolytic anemia with the unique morphology of “microspherocytes, measuring 2-3 microns in diameter, and cells with blunted projections or triangular in shape”, a morphology resembling the heat induced damage to normal erythrocytes - hence the name hereditary pyropoikilocytosis (HPP). Subsequently, similar cases were described with or without demonstrable heat sensitivity (Ravindranath &amp; Johnson, 1985). Regardless, the common denominators were 1) transfusion dependency early in infancy - resolved with splenectomy, 2) severe microcytosis, often &amp;lt;60 fL, and 3) a decrease in membrane bound spectrin (decreased spectrin/band3 ratio). Family studies showed normal RBC morphology in both parents (Ravindranath &amp; Johnson, 1985) or in some cases, one parent with HE (Zarkowsky et al., 1975). Protein chemistry studies showed decreased tetramer formation and tryptic digests showed mutations within the n-terminal alpha 1 domain of alpha spectrin - the dimer/dimer interaction site. Thus, homozygosity or double heterozygosity of mutations in the dimer/dimer interaction site of alpha spectrin (alpha 1 domain of alpha spectrin) defined HPP while classical HE cases showed heterozygous mutations in the alpha 1 domain. A fact unexplained was how this results in spectrin deficiency, specifically, alpha spectrin deficiency (Ravindranath &amp; Johnson, 1985). Using the molecular analytical tool AnemiaID (courtesy of Agios Pharmaceuticals, Inc.), we show that HPP is defined by the co-inheritance of two SPTA1 mutations and Alpha-LeLy polymorphism ( αLeLy rs28525570; SPTA1[c.5572C&amp;gt;G;c.6531-12C&amp;gt;T]) in one or both alleles, thus explaining the increased propensity for red cell fragmentation and the spectrin deficiency noted on acrylamide gels [Table: Clinical and molecular characteristics of our cases]. Of note, homozygosity for αLeLy polymorphism and one SPTA1 variant did not result in clinical HPP phenotype [HE-2 in Table]. At a clinical laboratory level, the extreme microcytosis in HPP is evident in the markedly diminished band3 content on eosin-5'-maleimide (EMA) binding test- mean channel fluorescence (MCF) of &amp;lt;275.0 (control: 473.0-549.0) while HE (including neonatal HE with hemolysis) show a double peak pattern in EMA (the minor peak representing the fragmented cells while the major peak had MCF higher than control MCF) and the characteristic trapezoid pattern on osmotic gradient ektacytometry (not shown).

Safety and Efficacy of Mitapivat in Adult Patients with Erythrocyte Membranopathies (SATISFY)

Background: Membranopathies encompass hemolytic disorders arising from genetic defects in erythrocyte membrane proteins and include hereditary spherocytosis and stomatocytosis. Congenital dyserythropoietic anemia type II (CDA II) is associated with SEC23B gene variants and its phenotype may be similar to hereditary spherocytosis. Anemia with or without the need for chronic transfusion, jaundice, splenomegaly, iron overload are complications common in both hereditary membranopathies and CDA II. Current treatment options for membranopathies and CDA II 1, apart from splenectomy, are primarily supportive. Mitapivat, an investigational pyruvate kinase-R (PKR) activator, has demonstrated efficacy in improving anemia and reducing hemolysis in adult patients with PK deficiency, thalassemia, sickle cell disease, and a mouse model of hereditary spherocytosis. Study Design and Methods: This study (NCT05935202) is an investigator initiated, prospective, multicenter, single-arm phase 2 trial. The study will be conducted in the European Union in Denmark and The Netherlands. It is the first clinical study in the context of the European Reference Network EuroBloodNet and will be sponsored by its closely associated non-for-profit EuroBloodNet Association. A sibling study in Toronto, Canada will be registered separately, and data will be pooled in a prespecified statistical analysis plan. The study will include approximately twenty-five adult patients (aged 18 years and older) diagnosed with a membranopathy or CDA II. Diagnosis must be confirmed genetically. Average hemoglobin concentration (Hb) must be less than 13.0 g/dL for males and 11.0 g/dL for females. Patients with average Hb &amp;gt;10.0 g/dL for males and females at screening must meet at least one of the following additional criteria: Splenomegaly, fatigue attributed to hemolysis, or paraclinical hemolysis. Adequate organ function is required. Patients cannot be included if they have a diagnosis of PK deficiency or if they have received red blood cell (RBC) transfusions (≥5 units the last 12 months or any within the last 3 months). During the 8-week Dose Escalation Period, subjects will receive an initial dose of 50 mg mitapivat twice daily (BID). Based on safety and changes in Hb levels, dosing may be increased to 100 mg BID at week 4. Patients who tolerate mitapivat may be eligible to continue in two consecutive 24-week Fixed Dose Periods, with an interim analysis in between the two fixed dose periods. The primary objective of this study is to evaluate the safety of mitapivat, assessed through the occurrence of treatment-emergent adverse events. Secondary objectives include assessing the effects of mitapivat on Hb concentration (≥1.0 g/dL increase sustained at two scheduled visits), hemolysis, erythropoiesis, patient-reported outcome measures, and spleen size. Exploratory endpoints include enzyme activity and stability of PK, Hb oxygen affinity, proteomics and metabolomics. To assess how activation of PK will impact RBC function we will measure RBC deformability (osmotic gradient ektacytometry and cell membrane stability) in whole blood and in different RBC subpopulations. Acknowledgement: This project is carried out within the framework of European Reference Network on Rare Haematological Diseases (ERN-EuroBloodNet)-Project ID No 101085717. ERN-EuroBloodNet is partly co-funded by the European Union within the framework of the Fourth EU Health Programme. The study is funded by a grant from Agios Pharmaceuticals.

Pyruvate Kinase Thermostability Is Associated with Red Blood Cell Adhesion, Deformability and Oxygen Affinity in Patients with Sickle Cell Disease

Introduction: Sickle cell disease(SCD) is caused by a mutation in the beta globin gene that causes formation of abnormal hemoglobin S (HbS). Red blood cells (RBCs) from patients with SCD are less deformable and take on the shape of sickle upon deoxygenation. This results in multiple downstream effects including RBC adhesion, microvascular occlusion and chronic hemolysis. RBCs rely solely on anaerobic glycolysis to produce adenosine triphosphate (ATP), which is needed to maintain the cell's structure and function. Pyruvate kinase (PK) is a key enzyme involved in the last step of glycolysis. We have previously demonstrated a decrease in PK activity and stability as a novel pathophysiological feature of SCD. Currently there are several clinical trials ongoing investigating the efficacy of PK activation by small molecules such as mitapivat (NL8517, NCT04000165, NCT05031780), AG-946 (NCT04536792) and etavopivat (NCT04624659, NCT04987489). In this study we aim to investigate how PK properties correlate to sickle RBC properties in order to explore if impaired PK function is associated with specific features of the complex SCD pathophysiology. Methods: Homozygous HbS (HbSS) and HbS/ β0 thalassemia patients were eligible to participate. Patients who received blood transfusion (&amp;lt;3 months) were excluded. Dense RBCs (MCHC &amp;gt;41 g/dL, Advia 120/2120 Siemens) and HbF and HbS levels (Tosoh G8) were measured. PK and hexokinase (HK) activity were measured on purified RBCs. PK thermostability (reflected by % residual PK activity) was measured on purified RBCs lysates after one hour of incubation (53°C). RBC adhesion to laminin (Biolamina) was measured using a microfluidic device (IBIDI µ-Slide I 0.4). RBC hydration (Ohyper), RBC deformability (EImax) and point of sickling (PoS) were assessed by osmotic and oxygen gradient ektacytometry using the Laser-Optical Rotational Red Cell Analyzer (Lorrca, RR Mechatronics). Oxygen affinity (P50) was measured with the Hemox-Analyzer (TCS). Statistical analysis was performed in Graphpad Prism (Pearson's correlation). Results: Fifty-seven patients with SCD (53 HbSS, 4 HbS/β 0 thalassemia) were included of which 17 were children (median age 14 years [range 6-17]) and 40 were adults (median age 36 years [range 18-58]). Baseline characteristics are depicted in Table 1. Figure 1 shows a heatmap with correlation coefficients of all laboratory parameters from Table 1 as measured in this cohort. When focusing on PK properties we found that patients with SCD and lower PK thermostability had significantly higher absolute reticulocyte counts (ARC, p&amp;lt;0.0001), lower hemoglobin (p=0.012) and HbF (p=0.020) levels and increased RBC adhesion to laminin (p=0.007). Furthermore, PK thermostability was significantly correlated with EImax (p=0.017) and inversely correlated with PoS (p=0.011) and P50 (p=0.003), indicating that patients with less stable RBC PK had less deformable RBCs which sickled at a higher oxygen tension. RBC adhesion to laminin was significantly correlated with both ARC (p=0.0003) and dense RBCs (p=0.019). To explore whether our findings were a reflection of reticulocytosis we fractionated whole blood samples of HbSS patients according to cell density. We found that more RBCs from the most dense fraction adhered to laminin than from the less dense, reticulocyte enriched, fraction, even though RBCs from this less dense fraction had reduced PK-thermostability. Additionally, the most dense RBCs had the lowest PK activity, were less deformable and had a higher PoS (data not shown). Altogether these findings indicate that the reduced PK thermostability we found in our SCD cohort is associated with an overall functionally impaired RBC population with increased RBC adhesion and ARC. We found no correlation of markers of RBC dehydration (Ohyper and % dense RBCs) with PK thermostability which suggests that RBCs with reduced PK thermostability are not more dehydrated. Discussion/conclusion: This study shows for the first time a significant correlation between PK thermostability in sickle RBCs and RBC functions, such as adhesion, deformability and oxygen affinity. Our results suggest that enhancing the activity and stability of PK, with PK activators, is an attractive target in SCD that might improve other pathophysiological targets outside RBC metabolism. Future studies are needed to explore how activation of PK will affect these altered sickle RBC properties in vivo.

Effects of L-Glutamine on Biomarkers of Response in Sickle Cell Disease: A Pharmacokinetics-Pharmacodynamics Analysis

OralL-glutamine (Endari®) has been approved by the US-FDA to reduce the acute complications of sickle cell disease (SCD) in patients at least 5 years of age. L-glutamine has several roles in the body including de novo synthesis of intracellular glutathione which acts as an antioxidant. However, the mechanisms of action by which L-glutamine could reduce complications in SCD require further investigation. Additionally, there are no known biomarkers to assess response to L-glutamine therapy. We conducted an open-label, dose-ascending trial (NCT04684381) of L-glutamine in pediatric (n=4) and adult (n=4) participants with SCD as well as in adult healthy volunteers (n=4) (Table 1). Over a three-week trial period with 4 study visits, serial blood samples were collected to define the pharmacokinetics (PK), pharmacodynamics (PD), and PK-PD interactions of L-glutamine using a broad panel of laboratory investigations including amino acid concentrations, blood counts, percentage of dense red blood cells (%DRBC), whole blood viscosity, osmotic and oxygen gradient ektacytometry, and reactive oxygen species (ROS) of reticulocytes (ROS retic) and mature red blood cells (ROS RBC). In PK-PD analysis of amino acids, we focused analysis on arginine (Arg), citrulline (Cit), and ornithine (Orn) based on the hypothesis that L-glutamine improves endothelial function by increasing arginine bioavailability and augmenting nitric oxide (NO) production. Peak arginine concentration was directly correlated with both the maximum L-glutamine concentration (C max p=0.001) and area-under-the curve (AUC) (p=0.047) indicating improvement in arginine bioavailability, but there was no significant linear correlation with either the Arg:Orn or Arg:(Orn+Cit) ratios. In PK-PD analysis of osmotic gradient ektacytometry, L-glutamine C max was directly correlated with the elongation maximum (EI max), noted in all participants at visit 4 (p=0.033). In SCD participants, L-glutamine C max was inversely correlated with O hyper (osmolality at EI max/2) at visits 3 (p=0.044) and 4 (p=0.004). In PK-PD analysis of oxygen gradient ektacytometry in SCD participants, L-glutamine C max was inversely correlated with the point of sickling (POS) at visit 3 (p=0.005) but not at visit 4 (p=0.054). Together, these findings suggest that although L-glutamine may decrease cellular hydration (decreased O hyper) it may increase RBC deformability (increased EI max) and delay the onset of sickling after hypoxia (decreased POS). In PK-PD analysis of viscometry, higher L-glutamine C max was associated with higher whole blood viscosity measurements at all shear rates (p&amp;lt;0.05). However, L-glutamine C max was also directly correlated with hematocrit-to-viscosity ratio (HVR) at the highest shear rates in the overall population at visit 4 (p&amp;lt;0.05). In addition, L-glutamine C max for SCD participants was associated with increased hemoglobin concentration, an effect that was observed at visit 4 (p=0.025), and increased %DRBC, an effect detected at visits 3 (p=0.008) and 4 (p=0.007). In PK-PD analysis of ROS, L-glutamine AUC was inversely correlated with ROS Retic (p=0.024), but not ROS RBC, in all participants at visit 3. When considered as total ROS Retic (calculated as ROS retic × absolute reticulocyte count), there was a similar inverse correlation with glutamine AUC in SCD participants, although not statistically significant. In contrast to all other biomarkers, L-glutamine C max was not correlated with any ROS measurement. This PK-PD analysis of L-glutamine reveals biological effects that alter RBC characteristics and could modify SCD-related complications, with a complex interplay summarized in Figure 1. Prospective studies can validate these biomarkers and be used to monitor the effects of L-glutamine therapy in SCD patients.

Novel Biomarkers for Assessing Clinical Severity in Hereditary Spherocytosis - Application of Routine and Advanced Diagnostic Tests

Background: Hereditary spherocytosis (HS) is caused by pathogenic variants in genes encoding red blood cell (RBC) cytoskeletal and (trans)membrane proteins. This ultimately leads to instability of the RBC membrane and subsequent membrane loss, resulting in the transformation of the biconcave RBC into a poorly deformable spherocyte, which is susceptible to premature splenic clearance. The diagnosis of HS has substantially improved over the last years and new advanced techniques have been established, including osmotic gradient ektacytometry, eosin-5'-maleimide (EMA) binding test and next-generation sequencing (NGS). However, there is little knowledge on the applicability of these diagnostic outcome parameters as biomarkers for clinical severity in HS. Aim: To explore possible correlations between established and novel diagnostic outcome parameters and clinical severity in a well-defined cohort of HS patients. Methods: This monocenter retrospective cohort study involves patients diagnosed with HS upon referral to our department between 2012 and 2023. Clinical characteristics, routine and advanced diagnostic laboratory parameters, and genotype were evaluated. Clinical severity was classified as previously described, based on parameters such as hemoglobin, reticulocyte percentage and bilirubin 1. The following laboratory tests were included: routine hematological parameters (Cel-Dyn Sapphire or Alinity hq), EMA binding test, osmotic fragility test (OFT) and osmotic gradient ektacytometry (osmoscan, Lorrca MaxSis). The latter technique was also explored for other parameters than the commonly used EI max, O hyper and O min. NGS gene panel analysis was used for molecular diagnosis. Differences between groups were determined using either Chi-squared test, unpaired t-test or Mann-Whitney U test and correlations using point-biserial, Pearson's or Spearman's test via GraphPad Prism. Results: Eighty-two non-splenectomized patients were included. Thirty-five of these (42.7%) were classified as mild, and forty-seven as moderate-severe (57.3%)). Demographic characteristics nor genotype differed significantly, albeit SPTB variants occurred more frequently in the moderate-severe group (15 vs. 4 in the mild group). Expectedly, both reticulocyte count and EI max correlated with clinical severity. RBC distribution width (RDW) correlated moderately, suggesting greater RBC heterogeneity (r=0.606, p&amp;lt;0.0001) is associated with a more severe clinical phenotype. Similarly, EMA binding test results correlated with clinical severity (r=0.390, p&amp;lt;0.001), indicating more pronounced membrane loss in clinically more severe patients. We further evaluated three novel osmoscan parameters ( Figure 1): EI O290, the elongation index (EI) at physiologic isotonicity, which correlated with clinical severity (r=-0.500, p&amp;lt;0.0001), and also with EI max (r=0.856, p&amp;lt;0.0001). The O min-width and O max-width, defined as the difference in osmolality between the intersection points of y=EI min or EI max +/- 0.05 and the osmoscan curve. Thisassesses the effect of changes in osmolality on EI min or EI max, respectively. O min-width correlated with RDW (r-0.439, p&amp;lt;0.0001), OFT results (N=30, r=0.671, p&amp;lt;0.0001) and clinical severity (r=0.390, p&amp;lt;0.001). O max-width correlated with clinical severity (r=-0.375, p&amp;lt;0.001) and strongly with percentage of hyperchromic cells (N=76, r=-0.751, p&amp;lt;0.0001), yet weakly with RDW (-0.273, p&amp;lt;0.05). All significant correlations with clinical severity are displayed in Figure 2. Conclusion: In this study, a number of routine and advanceddiagnostic laboratory parameters were found to correlate with clinical severity in HS. O min-width and O max-width are novel osmoscan-derived biomarkers that correlated with RDW, hyperchromic cells (O max-width), OFT results (O min-width) and clinical severity. EI O290, another novel osmoscan-derived biomarker, also correlated with clinical severity, although not stronger than EI max and AUC. The biomarkers identified in this study, together with patient-reported outcome measures (PROMs), could be used to revise the previously established severity classification system and thereby aid in stratifying clinical severity and subsequent clinical decision-making.

The Pyruvate Kinase (PK) Activator AG-946 Improves PK Properties and Red Blood Cell (RBC) Characteristics upon Ex Vivo treatment of RBCs from Patients with Myelodysplastic Syndromes

Background: Myelodysplastic syndromes (MDS) consist of a heterogenous group of clonal myeloid malignancies, characterized by dysplasia, ineffective hematopoiesis and cytopenias. MDS patients frequently suffer from anemia, directly affecting quality of life. The limited therapeutic options often do not result in the desired clinical improvement. Interestingly, in MDS the activity of the red blood cell (RBC) enzyme pyruvate kinase (PK), a key regulatory enzyme of glycolysis, may be decreased. The activation of PK via small molecules is hypothesized to be beneficial in a wide range of anemias. Currently, a phase 2a, open-label, proof of concept trial is running on the use of the PK activator AG-946 in low-risk MDS patients (NCT05490446). In light of these developments, we investigated the effect of ex vivo treatment of MDS RBCs with AG-946. Objectives: To evaluate RBC PK and cellular properties of patients with MDS, and to determine the effect of ex vivo treatment with the PK activator AG-946. Methods: Eleven low-risk non-transfusion dependent MDS patients and six healthy controls (HCs) were studied. Baseline PK activity and PK thermostability were measured in RBC lysates of purified RBCs, under V max conditions (phosphoenolpyruvate (PEP) 5mM final concentration). Hexokinase (HK) activity was included to relate PK activity to mean RBC age. Ex vivo treatment was performed by incubating MDS RBCs for 16 hours at 37 °C in presence or absence of the PK activator AG-946 (10μM or 5μM) using dimethylsulfoxide (DMSO) as a blank. Effect was assessed by measuring PK activity (using a final concentration of PEP 0.5mM) and levels of adenosine triphosphate (ATP) (LC-MS/MS). Functional RBC analysis was performed by osmotic gradient ektacytometry (Lorrca MaxSis). To investigate the effect on PK thermostability, RBC lysates were incubated with AG-946 (2μM or 1μM) or DMSO, after which residual PK activity was measured (PEP 0.5mM). The effect of AG-946 on erythroid development was studied using peripheral blood mononuclear cells, cultured in MethoCult TM H4434 medium for 14 days in the presence or absence of AG-946 (10μM or 625nM, DMSO as blank). Differences between conditions were determined using Unpaired T-test, ANOVA with Dunnett's test or Kruskal-Wallis with Dunn's test via GraphPad Prism. Results: Mean PK/HK ratio was significantly lower in RBCs from MDS patients compared to HCs (6.1 (SD 1.8) versus 10.5 (SD 1.5), p&amp;lt;0.001). Upon ex vivo treatment, PK activity significantly increased (independent of dosage) when compared to DMSO (10μM AG-946, mean increase 30% ( p&amp;lt;0.001); 5μM, 28% ( p&amp;lt;0.0001)) (Figure 1A). MDS RBCs displayed decreased PK thermostability at baseline under V max conditions (HCs 79% residual activity versus 68% in MDS, p&amp;lt;0.01). This was restored by ex vivo treatment with AG-946 (DMSO, 33% residual activity, 2μM AG-946, 85% ( p&amp;lt;0.0001); 1μM, 87% ( p&amp;lt;0.0001)). The increase in PK activity was accompanied by significantly increased ATP levels (N=10, DMSO, mean ATP 14.9 μg/mL RBC; 10μM AG-946, 21.0 μg/mL RBC ( p&amp;lt;0.01); 5μM, 21.1 μg/mL RBC ( p&amp;lt;0.01)) (Figure 1B). Functionally, RBC properties improved upon ex vivo treatment with AG-946 as reflected by the modest yet significant increase in O hyper, indicating improved hydration status (10μM AG-946, mean increase 2.3% ( p&amp;lt;0.001); 5μM, 2.9% ( p&amp;lt;0.0001)). To date, culture assays were performed in 8 patients; 3/8 showed an increase in the number of burst forming units-erythroid (BFU-Es) upon treatment with AG-946 when compared to DMSO. The percentual increases differed per patient: increase of 25% with 10μM AG946 and 150% with 625nM, increase of 40% (10μM) and 39% (625nM), and for the third an increase of 22% (10μM) and 39% (625nM). Conclusion: Our findings show that RBCs from MDS patients have decreased PK activity and thermostability. We demonstrate that ex vivo treatment with AG-946 increases PK activity and ATP levels and restores PK thermostability. Moreover, ex vivo treatment with AG-946 improves RBC hydration, suggesting that improved energy status directly improves RBC functional properties. The preliminary results of the culture assay could indicate that in certain patients, dyserythropoiesis may be ameliorated upon PK activation. To better understand the effects on erythropoiesis additional experiments are required. In conclusion, our data might support a rationale for the use of PK activators as a novel therapeutic option for MDS.

Congenital Dyserythropoietic Anemia Type II: An Update from the Congenital Dyseryhtropoietic Anemia Registry of North America (CDAR)

Congenital Dyserythropoietic Anemias (CDAs) are a heterogeneous group of rare anemias characterized by ineffective erythropoiesis and hemolysis. The CDA registry in North America (CDAR; NCT02964494) was established to facilitate natural history studies. Participants who do not have a genetic diagnosis are offered family-trio whole genome sequencing (WGS) and elect to provide samples to CDAR biorepository to support collaborative mechanistic studies. CDA type II (CDA-II), the most common CDA type, is an autosomal recessive disease caused by biallelic SEC23Bvariants. CDA-II presents with hemolytic anemia with suboptimal reticulocytosis, iron overload, splenomegaly, and characteristic binucleation in 10-30% of the bone marrow (BM) erythroblasts. Although CDA-II is a recessive disorder, only one SEC23B variant is found in some patients. Here, we present the genetic and clinical data of CDA-II patients enrolled in CDAR so far. As of July 2023, 169 individuals (85 patients; 84 unaffected family members) enrolled in CDAR. Nine have a confirmed CDA-II diagnosis. Six patients have biallelic SEC23B pathogenic variants and 3 have only one variant identified. WGS for the 3 patients with a single variant revealed rare deep-intronic candidate variants. Since SEC23Bis ubiquitously expressed, we studied SEC23B protein levels in patient-derived lymphoblastoid cell lines generated for the CDAR biorepository. Patients with a single SEC23B variant exhibited an expression level comparable to those with biallelic mutations (Figure). The candidate deep intronic variants are currently being investigated for pathogenicity. Seven patients presented with hemolytic anemia during infancy, but the age of diagnosis was delayed by a mean of 12.5 yrs (0.1 to 55 y.o). Blood smears showed mild macrocytosis, poikilocytosis, and several spherocytes congruent with an osmotic gradient ektacytometry resembling mild hereditary spherocytosis. BM examination, when performed, exhibited erythroid hyperplasia, prominent dyserythropoiesis, and binucleation in ≥ 10% of erythroblasts. Anemia severity was variable: 6 patients were transfusion-dependent, 1 received intermittent transfusions, and 2 did not need blood transfusions. Two became transfusion-independent after splenectomy at ages 6 and 7 y.o, and two underwent successful matched-sibling BMT at age 10 and 26 y.o, after adequate chelation (liver iron concentration [LIC]&amp;lt;7 mg/g) Iron overload, disproportionate to transfusions, was present in 6 patients; 5 received iron chelation. All 5 patients with available MRI results had hepatic hemosiderosis (LIC range 3.4 to 21.8 mg/g) and evidence of myocardial hemosiderosis (T2* range 6.3 to 20 ms). Ferritin values were variable (range 58 to 1631.5 ng/ml) and discordant from LIC and T2* measurements. Notably, ferritin underestimated iron overload burden: 2 patients with normal ferritin (58 and 160 ng/mL) had hepatic hemosiderosis (LIC 6.1 and 3.4 mg/g respectively), and patients with severe hepatic and myocardial hemosiderosis (LIC 16.6-21.8 mg/g; T2* 6.3-7.8 ms) had modest ferritin values 1475-1631 ng/mL. Iron overload was present even in a non-transfusion-dependent patient and worsened in a patient post-splenectomy, suggesting a role for ineffective erythropoiesis. To further investigate this possibility, we measured erythroferrone (ERFE), GDF-15, and hepcidin levels in 2 patients so far. ERFE and GDF-15 levels were remarkably higher than controls, and hepcidin-to-ferritin ratios were significantly lower, suggesting that high ERFE, caused by ineffective erythropoiesis, inappropriately suppressed hepcidin for the body's iron levels. In summary, CDA-II diagnosis is often delayed despite early onset of anemia. Genetic testing may expedite the diagnosis. The severity of anemia is variable and there are several patients requiring transfusions. The risk of iron overload, including myocardial overload, is high and appears to be related to ineffective erythropoiesis. While frequency of transfusions may improve post-splenectomy, iron overload is not determined by blood transfusions alone and does not resolve post-splenectomy. Serum ferritin underestimated the burden of tissue iron in CDA-II, suggesting that MRI scans should be employed early. Future studies may identify a role for SEC23B deep intronic variants in CDA-II patients with heterozygous variants.

Single-night continuous positive airway pressure treatment improves blood fluid properties in individuals recently diagnosed with obstructive sleep apnoea.

Obstructive sleep apnoea (OSA) is a prevalent disorder that causes repetitive, temporary collapses of the upper airways during sleep, resulting in intermittent hypoxaemia and sleep fragmentation. Given those with OSA also exhibit decreased blood fluidity, this clinical population is at heightened risk for cardiovascular disease (CVD) development. Continuous positive airway pressure (CPAP) remains a primary therapy in OSA, which improves sleep quality and limits sleep fragmentation. While CPAP effectively ameliorates nocturnal hypoxic events and associated arousals, it remains unclear whether CVD risk factors are positively impacted. The aim of the present study was thus to assess the effects of an acute CPAP therapy on sleep quality and the physical properties of blood that determine blood fluidity. Sixteen participants with suspected OSA were recruited into the current study. Participants attended the sleep laboratory for two visits: an initial diagnostic visit that included confirmation of OSA severity and comprehensive assessments of blood parameters, followed by a subsequent visit where participants were administered an individualised, acute CPAP therapy session and had their blood assessments repeated. Holistic appraisal of blood rheological properties included assessment of blood and plasma viscosity, red blood cell (RBC) aggregation, deformability, and osmotic gradient ektacytometry. Acute CPAP treatment significantly improved sleep quality parameters, which were associated with decreased nocturnal arousals and improved blood oxygen saturation. Whole blood viscosity was significantly decreased following acute CPAP treatment, which might be explained by the improved RBC aggregation during this visit. Although an acute increase in plasma viscosity was observed, it appears that the alterations in RBC properties that mediate cell-cell aggregation, and thus blood viscosity, overcame the increased plasma viscosity. While deformability of RBC was unaltered, CPAP therapy had mild effects on the osmotic tolerance of RBC. Collectively, novel observations demonstrate that a single CPAP treatment session acutely improved sleep quality, which was accompanied by improved rheological properties.

Quality assessment of red blood cell concentrates from blood donors at the extremes of the age spectrum: The BEST collaborative study.

Blood donors at the extremes of the age spectrum (16-19 years vs. ≥75 years) are characterized by increased risks of iron deficiency and anemia, and are often underrepresented in studies evaluating the effects of donor characteristics on red blood cells (RBC) transfusion effectiveness. The aim of this study was to conduct quality assessments of RBC concentrates from these unique age groups. We characterized 150 leukocyte-reduced (LR)-RBCs units from 75 teenage donors, who were matched by sex, and ethnicity with 75 older donors. LR-RBC units were manufactured at three large blood collection centers in the USA and Canada. Quality assessments included storage hemolysis, osmotic hemolysis, oxidative hemolysis, osmotic gradient ektacytometry, hematological indices, and RBC bioactivity. RBC concentrates from teenage donors had smaller (9%) mean corpuscular volume and higher (5%) RBC concentration compared with older donors counterparts. Stored RBCs from teenage donors exhibited increased susceptibility to oxidative hemolysis (>2-fold) compared with RBCs from older donors. This was observed at all testing centers independent of sex, storage duration, or the type of additive solution. RBCs from teenage male donors had increased cytoplasmatic viscosity and lower hydration compared with older donor RBCs. Evaluations of RBC supernatant bioactivity suggested that donor age was not associated with altered expression of inflammatory markers (CD31, CD54, and IL-6) on endothelial cells. The reported findings are likely intrinsic to RBCs and reflect age-specific changes in RBC antioxidant capacity and physical characteristics that may impact RBC survival during cold storage and after transfusion.

New-Generation Ektacytometry Study of Red Blood Cells in Different Hemoglobinopathies and Thalassemia

Next-generation ektacytometry provided by the osmoscan module of the Laser Optical Rotational Red Cell Analyser (LoRRca) MaxSis is, so far, one of the best complementary diagnostic tools for congenital rare anaemias due to red blood cell defects. Osmotic gradient ektacytometry (OGE) is currently considered the gold standard for the diagnosis of red cell membrane disorders, especially hereditary spherocytosis (HS). Impairment of red cell deformability, leading to a decrease in red cell survival rate, is the common trait of hereditary haemolytic anaemias; in general, it is the consequence of an abnormal cell shape, increased rigidity or dehydration. Up to now, the next-generation ektacytometry has been mainly used for the differential diagnosis of red blood cell membranopathies, but experience with structural hemoglobinopathies and thalassemia is still scarce. However, recently, many new forms of therapy are being developed for the treatment of hemoglobinopathies, particularly sickle-cell disease and β-thalassemia; clinical interest in ektacytometry is increasing and should be further explored. Here, we have evaluated the OGE profiles provided by the osmoscan module of the LoRRca ektacytometer in 96 patients with different hemoglobinopathies, both structural and thalassemia, with the aim of analysing their usefulness for the early diagnosis of these disorders either individually or in co-inheritance with other hereditary RBC defects. In addition, this study aims to improve our knowledge of the contribution of red cell deformability, osmotic fragility and intracellular viscosity to the physiopathology of haemolysis, especially when these disorders are a cause of rare anaemia. From this study, we conclude that the osmoscan profile provides complementary information on red cell deformability and hydration homeostasis that may contribute to the better understanding of the physiopathology of decreased red cell survival and hemolysis which is present in some patients.

An Endogenous Metabolic Modulator Composition Improves Hydration Status and Decreases Adhesion Properties of Red Blood Cells from Patients with Sickle Cell Disease

Background Sickle cell disease (SCD) is a group of hemoglobinopathies caused by point mutations in the β-globin gene leading to abnormal red blood cells (RBCs). There are various forms of SCD; sickle cell anemia (SCA) is characterized by homozygosity for hemoglobin (Hb) S (HbSS) whereas HbSC disease results from compound heterozygosity for HbS and HbC. HbC does not lead to RBC sickling, but induces loss of intracellular K+ and H2O causing RBC dehydration. Similarly, in HbSS RBCs, through dehydration, an increase of the intracellular concentration of poorly soluble HbS enhances polymerization upon deoxygenation, causing RBCs to become rigid and to sickle. Until recently, the only approved therapy for SCD was hydroxyurea (HU). HU increases fetal Hb (HbF) levels and improves RBC hydration and deformability. For decades, amino acids have been explored as potential treatment to restore the disrupted pathophysiological pathways in SCD. RCitNacQCarLKHVS, an Endogenous Metabolic Modulator (EMM) composition of ten different amino acids and derivatives, was designed to target and support RBC metabolism. In this study, we investigated the effect of ex vivo treatment of this EMM on RBC properties and function in SCA and HbSC. Methods Blood of 12 different adult SCD patients (9 HbSS [of whom 6 were on chronic RBC exchange (RBCX)], 3 HbSC) and 2 healthy controls was collected. Whole blood was incubated at standardized hematocrit (20%, patient plasma) in the presence or absence of different RCitNacQCarLKHVS concentrations for 4h at 37°C. Routine hematological parameters were measured using the Cell-Dyn Sapphire (Abbott Diagnostics). Percentage of total dense RBCs (%DRBCs) was analyzed from 10/12 patients (4 HbSS on RBCX, 3 HbSS not on RBCX, 3 HbSC) using the Advia 120/2120 hematology analyzer (Siemens Healthcare Diagnostics). Point of sickling (PoS), RBC deformability (EImax), and hydration status (Ohyper) were assessed by oxygen gradient ektacytometry and osmotic gradient ektacytometry, respectively, in 12/12 patients using the Lorrca (RR Mechatronics). Blood viscosity was measured in 6/12 patients (3 HbSS not on RBCX and 3 HbSC) at 37°C using a cone-plate viscometer (Brookfield). The hematocrit-to-viscosity ratio (HVR) was calculated as follows: hematocrit/blood viscosity at 300 s-1. RBC adhesion to laminin (BioLamina) was assessed in 4/12 patients (3 HbSS not on RBCX, 1 HbSC) using a microfluidic device (IBIDI μ-Slide VI 0.4). Statistical analysis was performed in Graphpad Prism v9.3.0 using the Friedman test. Results Ex vivo treatment of blood of SCD patients with RCitNacQCarLKHVS showed a significant dose-dependent increase in Ohyper as measured by osmotic gradient ektacytometry (Figure 1), indicating an improvement of RBC hydration status of SCD RBCs. This was accompanied by a significant increase in mean corpuscular volume (MCV) and reduction in mean corpuscular Hb concentration (MCHC). RBCs of healthy controls showed a similar trend in Ohyper, MCV and MCHC. In addition, %DRBCs showed a significant dose-dependent decrease in both HbSS and HbSC RBCs as a result of RCitNacQCarLKHVS treatment. Oxygen gradient ektacytometry showed a significant increase in maximum deformability (EImax), but no significant change in point of sickling. The HVR did not significantly change during dose-response experiments. Median RBC adhesion to laminin decreased as a result of ex vivo treatment with RCitNacQCarLKHVS (Figure 2). Conclusion Ex vivo treatment with RCitNacQCarLKHVS demonstrated a significant dose-dependent increase in RBC hydration (Ohyper, MCV, MCHC and %DRBCs), deformability (EImax) and decreased adhesion properties in SCD RBCs. Dehydrated and dense RBCs with reduced deformability and increased adhesion are more prone to hemolysis, and associated with vaso-occlusive complications such as priapism, skin ulcers, and nephropathy. Results from this study therefore suggest benefit of EMM in modulating clinically-relevant rheological properties such as hydration state and adhesion of SCD RBCs in both SCA and HbSC. The fact that HVR did not change may represent an additional therapeutic benefit, especially for HbSC patients who have, in general, higher blood viscosity compared to HbSS patients. Moreover, it would be worthwhile to investigate if the concomitant use of select amino acid combinations with HU or other anti-sickling agents has an additional beneficial effect in SCD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The Use of Next-generation Sequencing in the Diagnosis of Rare Inherited Anaemias: A Joint BSH/EHA Good Practice Paper.

The Use of Next-generation Sequencing in the Diagnosis of Rare Inherited Anaemias: A Joint BSH/EHA Good Practice Paper.

Efficient Screening Tests and Gene Mutation Spectrum for Hereditary Stomatocytosis in Japan

Background: Hereditary stomatocytosis (HSt) is a group of congenital hemolytic anemia caused by abnormally increased cation permeability of erythrocyte membranes. The most common subtype is dehydrated HSt (DHSt), and heterozygous mutations of the mechanosensitive calcium channel gene PIEZO1 have been associated with it most frequently. DHSt is suspected by screening tests such as erythrocyte morphology, cation concentration measurements inside and outside the erythrocyte membrane, or osmotic gradient ektacytometry; target-captured sequencing (TCS) is used for definitive diagnosis. We have shown that an increase in the residual red cells (%RRC) in a quantitative osmotic fragility test using a flow cytometer (FCM-OF) is useful as a screening test for DHSt.Purpose: We report the clinical findings and mutation spectrum of Japanese patients with DHSt confirmed by genetic testing.Methods: From April 2015 to June 2021, 27 patients who had a clinical diagnosis of DHSt and provided written consent were genetically tested. The clinical indications were hemolytic anemia with stomatocytes, accompanied by hemochromatosis, a family history, perinatal edema, and severe jaundice. Laboratory tests showed increased MCV, and subjects with an increased %RRC in FCM-OF were analyzed. TCS was performed using a hemolytic anemia-related gene panel.Results: Of the 27 patients, 14 had PIEZO1 variants, 3 had KCNN4 variants, and 2 had ABCB6 variants, for a total of 19 cases diagnosed as HSt. There was 1 SPTB mutation, 1 GCLC mutation, and 6 cases without mutations in genes known to be related to hemolytic anemia. There were 12 previously reported mutations (KCNN4: R352H, PIEZO1: V598M, T2014I, R2488Q, E2496ELE) and 5 novel mutations (KCNN4: P204R, A279T, PIEZO1: 427_428ins9AA, A1457V, K2323T).Notably, 5 E2496ELE mutations were found in unrelated individuals. There were no differences in age at diagnosis and severity of anemia between the E2496ELE mutation and other PIEZO1 mutations, but jaundice was more severe in patients with the E2496ELE mutation (p=0.007).The median age at diagnosis of the DHSt patients was 28 years (range: 2 months to 89 years); there were 6 men and 11 women. Three patients underwent splenectomy, and 2 patients with PIEZO1 mutations had postoperative thrombosis; 1 KCNN4 mutation had no complications, but no improvement in hemolytic anemia. Six patients had gallstones, 3 had fetal ascites, and 11 received red blood cell transfusions. Laboratory test results showed median Hb 10.4 g/dL (6.9-15.6), median MCV 99.7 fL (85-127.4), median MCHC 35.6% (33-39), and median T-Bil 3.4 mg/dL (0.5-37.9). The median ferritin level was 569.3 ng/mL (87.1-3895); of the 14 patients whose ferritin was measured at the time of diagnosis, 6 had already exceeded 1,000 ng/mL. The FCM-OF showed high values in all 16 cases tested.Discussion: Genetic testing was performed on cases in which DHSt was suspected based on clinical findings, smears, and FCM-OF; the diagnosis of DHSt was confirmed at a high percentage. As previously reported, the severity of hemolytic anemia was wide-ranging, and many cases of hemochromatosis were observed. The PIEZO1 mutation is the most common in the Japanese population, and the number of E2496ELE mutations is particularly conspicuous. Patients carrying E2496ELE mutations are reported to have a younger age at diagnosis and more severe hematological findings than other mutations; however, our results showed no significant differences in age at diagnosis or degree of anemia. Since the correlation between PIEZO1 gene mutation and phenotype has not yet been clarified, further research is considered necessary. DisclosuresNo relevant conflicts of interest to declare.

Identification of Biomarkers That Are Associated with Clinical Complications of Hemoglobin SC Disease and Sickle Cell Anemia

Introduction: Sickle cell disease (SCD) is an umbrella term used to describe inherited anemias that originate from a mutation in HBB, the gene coding for β-globin, that causes the formation of the abnormal hemoglobin S (HbS). The two most common genotypes are HbSS, termed sickle cell anemia (SCA) and HbSC, termed hemoglobin SC disease. Due to the higher prevalence and more severe clinical symptoms in SCA, attention is focused on this latter group of patients. Patients with HbSC disease who report significant SCD related symptoms are treated largely the same as SCA patients, despite differences in disease pathophysiology.Objective: To evaluate rheological differences in red blood cells (RBC) and whole blood from individuals with SCA and HbSC, and examine for associations with clinical complications.Methods: We analyzed an adult (n=30) and pediatric cohort (n=226) of SCA and HbSC individuals. Blood samples were evaluated for percent dense red blood cells (% DRBC), whole blood viscosity, and several ektacytometry-derived parameters, such as the cell membrane stability test, osmotic gradient ektacytometry and Point of Sickling (PoS): an oxygen gradient ektacytometry-derived biomarker that depicts the oxygen tension at which sickling is initiated. Subsequently, we assessed in the pediatric cohort (189 SCA and 37 HbSC individuals) if PoS, dense RBCs or blood viscosity are associated with clinical complications.Results: In particular (micro)dense RBCs (Figure 1A and B), blood viscosity (Figure 1C) and point of sickling (PoS, Figure 1D-F), are notably different in HbSC disease compared to SCA. In SCA, PoS was associated with occurrence of acute chest syndrome (ACS, for every 10mmHg increase OR 1.84, p<0.0001, adjusted OR 1.67, p=0.002), but no such association was found in children with HbSC. In contrast, we found an association of blood viscosity and ACS (OR 9.3, p=0.012; adjusted OR 13.5, p=0.015) in HbSC children, while we found no such association in SCA. No significant association of micro dense RBCs was found in SCA or HbSC children.Conclusion: We found that associations between PoS and ACS found in SCA were not found in HbSC. Instead, in HbSC ACS was associated with higher whole blood viscosity. We therefore conclude that sickling is a key factor in the pathophysiology of SCA, whereas in HbSC disease blood viscosity might play a crucial role in development of certain complications like ACS. This study suggests that complications in SCA and HbSC disease are driven by different aspects of blood abnormalities, and may warrant a distinct treatment approach. [Display omitted] DisclosuresRab: Axcella Health: Research Funding; Agios Pharmaceuticals: Research Funding. Schutgens: Shire/Takeda: Research Funding; Pfizer: Research Funding; OctaPharma: Research Funding; Novo Nordisk: Research Funding; CSL Behring: Research Funding; Bayer: Research Funding. Wijk: Axcella health: Research Funding; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding. Van Beers: Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; RR Mechatronics: Research Funding; Pfizer: Research Funding. Sheehan: Beam Therapeutics: Research Funding; Novartis: Research Funding; Forma Therapeutics: Research Funding.

An Ex Vivo Model of Oxidatively Stressed Red Blood Cells Demonstrates a Role for Exogenous Amino Acids in Enhancing Red Blood Cell Function and Morphology

The capacity of mature red blood cells (RBCs) to respond to oxidative stress is limited due to lack of a full complement of organelles and as such, when faced with an oxidative environment, they rely on their endogenous antioxidant capacity (including superoxide dismutase, catalase, peroxiredoxin and glutathione) to protect against cellular damage. Low blood glutathione activity has been reported in several red cell disorders leading to increased oxidative stress. Targeting oxidative stress has thus been proposed as a secondary treatment in multiple anemia-causing diseases, such as sickle cell disease (SCD) and malaria, although its overall efficacy remains unclear. As glutathione itself is not permeable through the RBC membrane, treatment with cell-permeable amino acid precursors of glutathione (glutamine, cysteine and/or glycine) is a potential strategy to expand the RBC's antioxidant capacity and alleviate oxidative stress. Indeed, L-glutamine has recently been approved as a therapeutic for SCD, although the mechanistic basis for its effect is not clear. To fill this gap in our understanding, we performed detailed characterization of biophysical phenotype, morphology, and intracellular redox environment of oxidatively stressed RBCs in environments with varying amounts of available precursor amino acids.To assess the impact of exogenous amino acid precursors on the RBC's glutathione antioxidant capacity, we exposed mature RBCs from healthy adults to hydrogen peroxide (H 2O 2) and co-incubated with media that included glutamine, cysteine, and/or glycine. As catalase has the ability to scavenge high levels of exogenously fluxed H 2O 2, we performed these experiments using sodium azide to block catalase activity, enabling us to model oxidatively stressed RBCs. We performed osmotic gradient ektacytometry to quantify RBC deformability and hydration status, and assessed RBC morphology using osmotic-adjusted fixation techniques and scanning electron microscopy. As previously documented, H 2O 2 exposure in sodium azide-treated healthy RBCs was associated with decreased deformability, decreased hydration and increased numbers of echinocytes in a dose-dependent manner. We monitored red cell phenotypic changes following co-incubation with glutamine, cysteine, and/or glycine individually and in combination to test whether these amino acids extended the RBC's antioxidant abilities and contributed to improved function and morphology. We found that supplementation with all three amino acids in combination significantly improved both deformability and hydration of H 2O 2-stressed RBCs, as opposed to treatment with glutamine alone. To directly assess whether the exogenous amino acids were in fact contributing to less intracellular oxidative stress in RBCs, we quantified intracellular reactive oxygen species (ROS) using 2‘, 7‘ -dichlorofluorescein diacetate (DCFDA), a cell permeable dye used to measure ROS production. As expected, H 2O 2 exposure alone was associated with elevated intracellular ROS inside RBCs in both a time- and dose-dependent manner. Supplementation with the three amino acid cocktail during H 2O 2 stress resulted in a reduction in the level of intracellular ROS activity.In summary, we documented that exogenous added amino acids reduce oxidative damage in RBCs and we hypothesize that this protection occurs via the glutathione antioxidant pathways. In future studies, we plan to investigate the impact of exogenous amino acids on sickled and irreversibly sickled RBCs (ISCs) in the context of SCD, and on uninfected and infected RBCs in the context of malaria. DisclosuresKim-Shapiro: Beverage Operations LLC: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: co-inventor on a patent related to the use of nitrite under cardiovascular conditions, and a co-author on patents related to treatment of hemolysis.

Facilitating EMA binding test performance using fluorescent beads combined with next-generation sequencing.

The eosin‐5′‐maleimide (EMA) binding test is widely used as diagnostic test for hereditary spherocytosis (HS), one of the most common haemolytic disorders in Caucasian populations. We recently described the advantages of replacing the use of healthy control blood samples with fluorescent beads in a modified EMA binding assay. In this study we further explore this novel approach. We performed targeted next‐generation sequencing, modified EMA binding test and osmotic gradient ektacytometry on consecutive individuals referred to our laboratory on the suspicion of HS. In total, 33 of 95 carried a (likely) pathogenic variant, and 24 had variants of uncertain significance (VUS). We identified a total 79 different (likely) pathogenic variants and VUS, including 43 novel mutations. Discarding VUS and recessive mutations in STPA1, we used the occurrence of (likely) pathogenic variants to generate a diagnostic threshold for our modified EMA binding test. Twenty‐one of 23 individuals with non‐SPTA1 (likely) pathogenic variants had EMA ≥ 43.6 AU, which was the optimal threshold in receiver operating characteristic (ROC) analysis. Accuracy was excellent at 93.4% and close to that of osmotic gradient ektacytometry (98.7%). In conclusion, we were able to simplify the EMA‐binding test by using rainbow beads as reference and (likely) pathogenic variants to define an accurate cut‐off value.