Red Blood Cell Population Research Articles

Clearance of pathogenic erythrocytes is maintained despite spleen dysfunction in children with sickle cell disease.

In children with sickle cell disease (SCD), splenectomy is immediately beneficial for acute sequestration crises and hypersplenism (ASSC/HyS) but portends a long-term risk of asplenia-related complications. We retrieved peripheral and splenic red blood cells (RBCs) from 17 SCD children/teenagers undergoing partial splenectomy for ASSC/HyS, 12 adult subjects without RBC-related disease undergoing splenectomy (controls), five human spleens perfused ex vivo with HbSS- and HbAA-RBC, and quantified abnormal RBC by microscopy, spleen-mimetic RBC filtration, and adhesion assays. Spleens were analyzed by immunohistochemistry and transmission electron microscopy (TEM). In circulating blood of SCD and control subjects, dysmorphic (elongated/spherocytic) RBCs were <2%, while proportions of pocked-RBC were 4.3-fold higher in SCD children than in controls. Compared to controls, splenic RBCs were more frequently dysmorphic (29.3% vs. 0.4%), stiffer (42.2% vs. 12.4%), and adherent (206 vs. 22 adherent RBC/area) in SCD subjects. By TEM, both polymer-containing and homogenous RBC contributed to spleen congestion, resulting in 3.8-fold higher RBC population density in SCD spleens than in control spleens, predominantly in the cords. Perfused spleens with normal function displayed similar congestion and retention of dysmorphic RBC as SCD spleens. The population density of active macrophages was similar in SCD and control spleens, with a relative deficit in phagocytosis of polymer-containing RBC. Despite the existence of hyposplenism, splenectomy in SCD children removes an organ that still efficiently filters out potentially pathogenic altered RBC. Innovative treatments allowing fine-tuned reduction of RBC retention would alleviate spleen congestion, the major pathogenic process in ASSC/HyS, while preserving spleen protective functions for the future.

Lysis of human erythrocytes due to Piezo1-dependent cytosolic calcium overload as a mechanism of circulatory removal

Hematopoietic stem cells surrender organelles during differentiation, leaving mature red blood cells (RBC) devoid of transcriptional machinery and mitochondria. The resultant absence of cellular repair capacity limits RBC circulatory longevity, and old cells are removed from circulation. The specific age-dependent alterations required for this apparently targeted removal of RBC, however, remain elusive. Here, we assessed the function of Piezo1, a stretch-activated transmembrane cation channel, within subpopulations of RBC isolated based on physical properties associated with aging. We subsequently investigated the potential role of Piezo1 in RBC removal, using pharmacological and mechanobiological approaches. Dense (old) RBC were separated from whole blood using differential density centrifugation. Tolerance of RBC to mechanical forces within the physiological range was assessed on single-cell and cell population levels. Expression and function of Piezo1 were investigated in separated RBC populations by monitoring accumulation of cytosolic Ca2+ and changes in cell morphology in response to pharmacological Piezo1 stimulation and in response to physical forces. Despite decreased Piezo1 activity with increasing cell age, tolerance to prolonged Piezo1 stimulation declined sharply in older RBC, precipitating lysis. Cell lysis was immediately preceded by an acute reversal of density. We propose a Piezo1-dependent mechanism by which RBC may be removed from circulation: Upon adherence of these RBC to other tissues, they are uniquely exposed to prolonged mechanical forces. The resultant sustained activation of Piezo1 leads to a net influx of Ca2+, overpowering the Ca2+-removal capacity of specifically old RBC, which leads to reversal of ion gradients, dysregulated cell hydration, and ultimately osmotic lysis.

Distribution of Red Blood Cells Deformability: Study on Density-Separated Cell Subpopulations

Aging-related processes lead to significant metabolic and structural changes in red blood cells (RBCs) and, as a result, to heterogeneity in cell populations. Using the Percoll linear density gradient, separating the RBC population and obtaining fractions enriched with cells of different ages is possible. Previously, cells from the “light” fraction were characterized by increased deformability. However, the distribution of RBC deformability in subpopulations possessing a different density has not been studied. In this study, we measured the deformability of RBCs from cell fractions characterized by different densities. RBC deformability was determined using a computerized cell flow-properties analyzer, which provides the deformability distribution in a population of 10,000–15,000 cells. Our results demonstrate a strong correlation between the cytosol hemoglobin concentration and the cell deformation indexes. In addition, we show that the “lightest” fraction of RBCs contains the lowest number of deformable and the highest number of highly deformable cells. In contrast, the “dense” fraction is enriched with undeformable RBCs, with a minimal presence of highly deformable cells. In summary, we have shown that RBC fractions depleted or enriched with undeformable cells can be obtained by using a density gradient. However, these fractions are not homogeneous in their deformability properties.

Routine maternal ABO/Rhesus D blood typing can alert of massive foetomaternal haemorrhage.

Spontaneous massive foetomaternal haemorrhage (SM-FMH) is a rare yet critical condition that poses substantial risk to foetal health and survival. Existing data indicate that many cases may be undiagnosed. The current study aimed to investigate and validate the utility of identifying mixed field red blood cell (RBC) agglutination during maternal blood typing as a diagnostic aid for SM-FMH. Retrospective analysis of medical records from neonates born at our tertiary, university-affiliated medical centre between 2016 and 2023 was performed. Diagnosis of SM-FMH was based on neonates born with severe anaemia (haematocrit [HCT] <15%) within the first 24 h post-delivery with positive maternal Kleihauer-Betke (KB) test. Maternal ABO/Rhesus D (RhD) blood typing results were scrutinized with the primary objective of assessing the ability to identify dual RBC populations in cases clinically diagnosed with SM-FMH. Among 29,192 neonates studied, a mere 0.02% (5 cases) exhibited severe SM-FMH. Notably, a mixed field RBC agglutination was discerned in 80% (4/5) of these cases. This study underscores the significance of detecting mixed field RBC agglutination during antepartum maternal ABO/RhD blood typing as a potential indicator for SM-FMH. Increased awareness among blood bank technology specialists and obstetricians regarding these laboratory findings could prove instrumental in saving foetal lives.

Abstract PO3-26-09: A novel class of RNR inhibitors that induces genomic instability and breast cancer cell death without inducing overt toxicities

Abstract Despite the development of screening techniques and therapies, nearly 30% of breast cancers progress to Stage IV metastatic disease. These advanced cancers are highly proliferative, engaging in ongoing DNA synthesis that requires ribonucleotide reductase (RNR), the rate-limiting enzyme for dNTP synthesis. RRM2, the small subunit of RNR, activates the enzyme, increases deoxynucleotide pools, and is overexpressed in many cancers, including breast cancer. Thus, RNR is an established therapeutic target in advanced breast cancer. Currently, gemcitabine is the only FDA-approved RNR inhibitor used to treat Stage IV disease. As a nucleoside analog, gemcitabine also causes severe dose-limiting toxicities (i.e. myelosuppression and hepatotoxicity) due to off-target DNA replication termination. We hypothesize that a novel, non-nucleoside, RNR inhibitor may overcome these limitations. To address this, we developed TMU27a, a derivative of naphthyl salicylic acyl hydrazone (NSAH), which was identified in an in silico screen for its high-affinity binding to the RNR catalytic site. To measure direct interactions between TMU27a and purified RNR protein, we used surface plasmon resonance, revealing on-target, tight binding (Kd = 150 nM). Unbiased docking and molecular dynamics simulations (using lowest energy calculations) predicted the binding sight of TMU27a to be the catalytic site of RNR, where it is stabilized through extensive interactions formed with conserved residues. Preliminary docking predictions also indicate multiple clash sites between TMU27a and the DNA polymerase lambda nucleotide pocket even in the lowest energy pose (unlike gemcitabine), suggesting that TMU27a inhibits RNR activity through a novel mechanism without significant off-target binding to other nucleotide binding proteins that contribute to toxicity. Demonstrating on-target inhibition, TMU27a reduces dATP levels and induces S and G2/M-phase stalling, leading to significant DNA damage and chromosomal instability. This excessive genomic damage causes growth repression, apoptosis, and senescence in several triple negative breast cancer (TNBC) cell lines. In xenograft mouse models of TNBC, TMU27a fully suppressed tumor growth without impacting mouse weight, suggesting strong drug efficacy in the absence of overt toxicity. Moreover, while short-term exposure to gemcitabine suppresses red and white blood cell populations, TMU27a does not. Together, these data indicate that TMU27a and its potential analogs are novel, non-toxic RNR inhibitors that overcome the limitations of gemcitabine for treating breast cancer. We are currently investigating how and where TMU27a binds human RNR using cryo-electron microscopy with the goal of generating a novel class of RNR inhibitors through structure-based drug design, improving binding affinity and selectivity. Citation Format: Taylor Baker, Kristen Weber-Bonk, Wei Huang, Derek Taylor, Ruth Keri. A novel class of RNR inhibitors that induces genomic instability and breast cancer cell death without inducing overt toxicities [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-26-09.

Abstract 3665: Stratifying prostate cancer patients through circulating genes related to prostate cell subtypes, drug targets, and therapeutic resistance

Abstract Stratification remains an obstacle for the optimal treatment of prostate cancer (PCa) patients throughout the treatment trajectory. Targeting the androgen receptor (AR) kills the majority of luminal-like cells, which are AR-positive and express Prostate Specific Antigen (PSA). However, a subset of surviving AR-positive cells develop resistance to treatments while AR-negative cells of the neuroendocrine (NE) or stem-like phenotypes emerge through selection. We reported on the clinical relevance of cell-subtype genes in whole blood RNA of advanced PCa patients. Here, we studied an expanded panel of genes to include drug targets and therapeutic resistance as predictive biomarkers to stratify patients at diagnosis and at the advanced stage of disease.Genes were chosen based on literature review, results of clinical trials in PCa, and PCa transcriptomic data. Technical validation of TaqMan RT-qPCR assays was carried out for each gene, including rigorous testing of reproducibility. Whole blood RNA was extracted from 26 healthy controls with no prostatic disease, 16 patients prior to prostatectomy, and 43 blood samples from 28 metastatic cases. Gene overexpression was defined as the 99.5% confidence interval of expression in controls. Clinical data were retrieved from patients’ charts.A panel of 64 genes was built, showing overexpression in advanced PCa but low or no expression in normal blood (including whole blood, white and red blood cell populations and platelets). Testing in control blood showed no correlation with age. The proportions of patients’ white blood cells did not correlate with gene expression in their blood. Overall, up to 44/64 genes were overexpressed in at least one patient sample. Patients with prostatic intraductal carcinoma at prostatectomy showed more circulating genes, including more NE and stemness genes, and more PCa cell subtypes represented. Intermediate and high-risk patients showed more circulating NE genes. In metastatic patients, signatures of luminal, NE, stemness, and resistance to AR inhibitors or taxanes were associated with progression. PCa-specific luminal genes were associated with shorter overall survival. Treatment resistance genes correlated with lines of treatment and current taxanes. Two targetable NE genes were overexpressed in distinct categories of patients, suggesting that they may benefit from more specific treatments.In conclusion, phenotypic and functional differences in circulating gene patterns of PCa patients correlate with pathological features, treatments, progression. They may be clinically meaningful to stratify patients and predict therapeutic response. Circulating genes encoding drug targets may justify clinical trials to offer personalized treatments and impact on lethal PCa. Citation Format: Seta Derderian, Edouard Jarry, Arynne Santos, Mohanachary Amaravadi, Quentin Vesval, Lucie Hamel, Raphael Sanchez-Salas, Alexis Rompré-Brodeur, Wassim Kassouf, Raghu Rajan, Marie Duclos, Fadi Brimo, Armen Aprikian, Simone Chevalier. Stratifying prostate cancer patients through circulating genes related to prostate cell subtypes, drug targets, and therapeutic resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3665.

Homologous blood transfusion and doping: Where are we now?

Homologous blood transfusion (HBT) is used for doping in endurance sports since the 1960s. The blood comes from a compatible donor, that is, someone with a compatible ABO and rhesus blood group. Despite been prohibited by the IOC in 1985, no detection method was available until 2003. Then came the idea to use red blood cells (RBC) minor blood groups antigens that constitute an "identity" card of someone's RBC to detect the presence of a second RBC population. The method validated for doping control samples uses flow cytometry after incubation of isolated RBC with eight to 12 primary antibodies against specific minor blood groups antigens. The presence of double populations of RBC is revealed by a major and a minor peak in a fluorescence histogram. The sensitivity was estimated sufficient to detect HBT for a few weeks. Despite the complexity and cost of the method, right after its application in 2004, several cases of HBT were identified but the number of cases dropped rapidly over the years. In the 2010s, other ways to detect HBT were developed and evaluated: indirect detection using the Athlete Biological Passport approach, and a few years later forensic DNA analysis to establish the presence of two different DNA in a blood sample after HBT. Despite the high specificity of the latter, the sensitivity was recently questioned in vivo. Nowadays, the flow cytometry method remains the method of choice for HBT detection and recent investigations helped to simplify the method and increase its specificity and sensitivity.

Viscoelastic phenotyping of red blood cells

Red blood cells (RBCs) are the simplest cell types with complex dynamical and viscoelastic phenomenology. While the mechanical rigidity and the flickering noise of RBCs have been extensively investigated, an accurate determination of the constitutive equations of the relaxational kinetics is lacking. Here we measure the force relaxation of RBCs under different types of tensional and compressive extension-jump protocols by attaching an optically trapped bead to the RBC membrane. Relaxational kinetics follows linear response from 60 pN (tensional) to −20 pN (compressive) applied forces, exhibiting a triple exponential function with three well-separated timescales over four decades (0.01–100 s). While the fast timescale (τF∼0.02(1)s) corresponds to the relaxation of the membrane, the intermediate and slow timescales (τI=4(1)s; τS=70(8)s) likely arise from the cortex dynamics and the cytosol viscosity. Relaxation is highly heterogeneous across the RBC population, yet the three relaxation times are correlated, showing dynamical scaling. Finally, we find that glucose depletion and laser illumination of RBCs lead to faster triple exponential kinetics and RBC rigidification. Viscoelastic phenotyping is a promising dynamical biomarker applicable to other cell types and active systems.

Fetal Hemoglobin Decrease during Voxelotor Treatment

Sickle cell disease (SCD) is an inherited disorder caused by a point mutation in the β-globin gene leading to the formation of hemoglobin S (HbS). The polymerization of deoxygenated HbS is the first event in the molecular pathogenesis of SCD resulting in sickling of red blood cells (RBC), and hemolytic anemia which has been shown to be associated with organ damage and early death. Hemolytic anemia is defined by an accelerated rate of destruction RBC resulting in a lowered Hb level and a reduced gas transport capacity. Because Hb S in its oxy (R) conformation do not polymerize, drugs modifying hemoglobin (Hb) to increase the proportion of oxy-HbS have been propose to inhibit HbS polymerization. Voxelotor is such a molecule, which allosterically modifies Hb-oxygen affinity improving anemia and reducing hemolysis. However, the impact of Voxelotor on HbF levels is unknown. We describe here variations of %HbF and Mean corpuscular HbF (MCHbF) in a cohort of homozygous SCD patients treated with Voxelotor in our Sickle Cell Referral center. We conducted a prospective register study to analyze clinical and biological evolution of SCD patients treated with Voxelotor at 1500mg taken orally once daily. From December 2021 through December 2022, 25 SCD adult patients were followed during a median of 7 months [1-12]. Among them, HbF values were analyzable for 15 patients (SS gentype n=14; women in 73%; median age of 50 years [24-61]) who completed 6 months of Voxelotor with no transfusion during the same period; and with a stable dose of hydroxyurea (HU), for at least 3 months before inclusion and during the study in case of patients treated by HU (n=10). The dose of Voxelotor was stable for 13/15 patients and was decreased in 2 patients due to skin allergy (n=1) and moderate digestive intolerance. One patient died after 6 months of treatment in a context of end-stage renal failure and severe pulmonary hypertension not related to Voxelotor treatment. Mean corpuscular HbF (MCHbF) was calculated (MCHbF (pg) = MCH x %HbF). HbF percentage was measured by high performance liquid chromatography (Biorad, Variant II, beta-thal dual program). All participants provided written informed consent (CPP Erythropedie). From baseline to 6 months of follow up mean Hb (g/dL) concentration increased from 7.4 [5.4-8.5] to 8 [5-11.9] (p=0,0003; Figure A); absolute reticulocyte count (ARC ; Giga/L) decreased from 158 to 145 (p=0,005), %HbF decreased by 63% in all patients from 7,1% to 3,3% (p=0,008; Figure B) and MCHbF (pg) decreased from 3,36 to 1,03 (p=0,001; Figure D). A decrease in % HbF was observed from the first 15 days of treatment in both groups of patients treated or not with HU (Figure C) ; no changes in mean corpuscular volume (p=0.15) was observed in patients treated with HU during follow up. The HbF decrease in SCD patients treated with Voxelotor could be explained by different mechanisms: - Reduction of stress erythropoiesis which is due to an increase in erythroid output in response to anemic stress associated with a reduced expression of BCL11A, a transcriptional repressor that inhibits adult-stage HbF expression. This hypothesis is supported by the reduction in reticulocytes in patients treated with Voxelotor - The loss of an HbF-related survival advantage for SCD RBCs, while the normal RBC lifespan is approximatively 120 days, in SCD RBCs it is only a sixth of it. HbF is a major modulator of SCD and prolonge SCD RBCs survival. Its protective effect relies on its quantity and distribution among the RBC population, which is often heterogeneous in SCD patients. Protection against polymerisation of Voxelotor is probably more homogeneous among RBCs. As a result, RBCs containing low levels of HbF, which would normally disappear, have a prolonged lifespan. Similarly, it was presumed that sickling of erythroblasts could lead to ineffective terminal erythroid differentiation with an anti-apoptotic role for HbF during the terminal stages of erythroid differentiation. However we found no significant difference for index of ineffective erythropoiesis (soluble transferrin receptor / absolute reticulocyte count) before and after 6 months of treatment. The question raised is therefore that of the risk of a rebound effect upon discontinuation of Voxelotor, which has a short half-life, during the time it takes for HbF to increase. To better study this hypothesis, distribution of HbF/RBC will be studied in the HEMOPROVE trial (NCT05199766) currently in progress.

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.

Platelets mediate the clearance of senescent red blood cells by forming prophagocytic platelet-cell complexes

AbstractIn humans, ∼0.1% to 0.3% of circulating red blood cells (RBCs) are present as platelet-RBC (P-RBC) complexes, and it is 1% to 2% in mice. Excessive P-RBC complexes are found in diseases that compromise RBC health (eg, sickle cell disease and malaria) and contribute to pathogenesis. However, the physiological role of P-RBC complexes in healthy blood is unknown. As a result of damage accumulated over their lifetime, RBCs nearing senescence exhibit physiological and molecular changes akin to those in platelet-binding RBCs in sickle cell disease and malaria. Therefore, we hypothesized that RBCs nearing senescence are targets for platelet binding and P-RBC formation. Confirming this hypothesis, pulse-chase labeling studies in mice revealed an approximately tenfold increase in P-RBC complexes in the most chronologically aged RBC population compared with younger cells. When reintroduced into mice, these complexes were selectively cleared from the bloodstream (in preference to platelet-free RBC) through the reticuloendothelial system and erythrophagocytes in the spleen. As a corollary, patients without a spleen had higher levels of complexes in their bloodstream. When the platelet supply was artificially reduced in mice, fewer RBC complexes were formed, fewer erythrophagocytes were generated, and more senescent RBCs remained in circulation. Similar imbalances in complex levels and senescent RBC burden were observed in humans with immune thrombocytopenia (ITP). These findings indicate that platelets are important for binding and clearing senescent RBCs, and disruptions in platelet count or complex formation and clearance may negatively affect RBC homeostasis and may contribute to the known risk of thrombosis in ITP and after splenectomy.

New Insights into VOC Incidence By Analyzing the Single Cell Quantification of HbF per RBC and Mchbs

Vaso-occlusive crisis (VOC), the main complication of sickle cell disease (SCD), is responsible for more than 50% of the associated deaths. The effect of hydroxyurea, the cornerstone treatment for SCD, on the occurrence of VOC is mainly mediated by increasing HbF levels, which is a protective factor by inhibiting hemoglobin S (HbS) polymerization. 1,2 However, HbF level is variable between patients, and its expression is heterogeneous among the red blood cell (RBC) population. 3 As a result, while an increase in HbF levels is associated with better survival, %HbF only partially explains patients' clinical manifestations. The protective effect of HbF is also related to the HbS content; the more HbS, the more HbF is needed to inhibit its polymerization. In this study, we wondered if the single-cell quantification of HbF that we developed could better explain the VOC incidence of SCD compared to %HbF. Patients and method We analyzed data from the FCDREP1 protocol, aiming to obtain a predictive score for VOC at 1 year. Inclusion criteria were SS and S- S-b 0 Thal SCD patients, more than 1 month after a vaso-occlusive crisis, 3 months after a transfusion, and on a stable dose of hydroxyurea (HU) for at least 3 months. After giving their consent (IRB no. 00003835) during a routine blood sampling visit, an additional sample was taken for HbF single cell quantification, providing HbF/cell distribution. VOC were collected prospectively for 1 year. HbF single cell quantification was measured by flow cytometry using a previously published protocol, 4 data are expressed as histograms representing % RBC in each HbF range in pg for the whole cluster. K-means clustering was performed on different combination of variables containing ranges of HbF/cell distribution versus %HbF, with MCHbS (MCH x %HbS) using UMAP for dimensionality reduction (into 2), after we applied Min-Max scaling to preprocess the features, with python 3 on sklearn and umap library. This clustering approach can group data points based on their similarity, providing insights into distinct patterns or subgroups within the dataset. Results One hundred two patients were included with a mean age of 38 ± 11 years, a sex ratio F/M of 0.56, 63% of patients were on HU. Patients had a total of 74 VOC with a mean of 0.71 ± 1.4 VOC per patient in the year. Analyses were performed finding 4 different clusters in different 2 groups. Group 1: clusters identified by the association of HbF/cell distribution and MCHbS (HbF/Cell) and Group 2: clusters identified by %HbF and MCHbS (%HbF). Clusters were numbered according to increasing HbF levels (Figure 1A and B). There was no significant difference in age or sex ratio between the groups whereas the percentage of patients on HU differed between groups (Figure 1F). The number of patients by cluster was also similar. Cluster analysis of Group 1 showed a decrease in VOC incidence (Figure 1E, blue bars) associated with an increase in HbF level per RBC (Figure 1A). If clusters 1 and 2 are similar regarding the % of HU-treated patients, cluster 1 shows a lower HbF/cell content (Figure 1A) but lower MCHbS and MCH (Figure 1C and 1D), possibly explaining a similar VOC incidence in the 2 clusters. With a higher % of HU-treated (Figure 1F), Cluster 3 and 4 stand out from each other by different HbF expression patterns and VOC incidence (Figure 1A). The clusters of group 2 does not show the same increasing incidence of VOC as a function of median %HbF (Figure 1B and E). If cluster 4, mostly treated with HU, corresponds to patients with high %HbF and low VOC; cluster 1, with little HU treatment and very low %HbF, has few VOCs, not explained by MCHbS. The difference in severity between clusters 2 and 3, which have the same percentage of HU, could be explained by the greater difference in %HbF distribution, with median %HbF values of 11.8 [5-14] and 13.8 [11-15] (p=0.06) respectively, as well as by the low MCHbS of cluster 3. Conclusion : Single cell quantification of HbF in RBC in association with MCHbS could help improve to better understand VOC incidence.

Genetic Regulation of Carnitine Metabolism Controls Lipid Damage Repair Mechanisms and Hemolytic Propensity of Human Red Blood Cells during Aging In Vivo and in Vitro

Large scale genomics studies and vein-to-vein databases have started to reveal that donor biology and genetics influence red blood cell (RBC) storability and transfusion outcomes. To further delve into this concept, here we performed metabolomics analyses of 13,091 packed RBC units from donors enrolled in the Recipient Epidemiology and Donor Evaluation (REDS) RBC Omics study. End of storage (day 42) units were tested for metabolomics and hemolytic propensity. Donors ranking in the 5 th and 95 th percentile were contacted again and invited to donate a second unit of blood, which was stored again for 42 days (n=643). Correlation of end of storage metabolomics measurements for the first (index) and second (recalled) donation identified a core of metabolites involved in carnitine synthesis and acyl-carnitine metabolism as the most reproducible within the same donor across multiple donations ( Figure 1.A). Carnitine and its precursors, methyl- and trimethyl-lysine were the most significantly reproducible of all the metabolites tested in this study ( Figure 1.A). Association of L-carnitine measurements to genomics data (i.e., 879,000 single nucleotide polymorphisms that were assayed via a precision transfusion medicine array developed for this study - Figure 1.B) identified non-synonymous coding polymorphisms in the carnitine transporter SLC22A16 as a critical genetic factor contributing to inter-donor heterogeneity in end of storage carnitine levels ( Figure 1.B). Donors carrying two alleles of this SNP were characterized by the lowest L-carnitine levels, and associated depletion of the whole carnitine pool. Functionally, stored RBCs with the lowest levels of carnitine pools were characterized by significant elevation in in vitro hemolysis and the highest degree of vesiculation, in parallel to increases in lipid peroxidation markers (hydroxy-eicosatetraenoic - HETEs and hydroxy-octadecadienoic acids - HODEs). We leveraged a novel CFDA-SE staining protocol, which allows flow cytometry sorting of end of storage RBCs in two highly enriched preparations: a morphologically-altered subpopulation (CFDA-SE high) and a morphologically-normal RBC subpopulation (CFDA-SE low). The morphologically-altered subpopulations contains mostly storage-induced micro-erythrocytes (SMEs), i.e., RBCs with decreased surface/volume ratio upon storage-induced vesiculation. This RBC sub-population has increased susceptibility to extravascular hemolysis via splenic sequestration upon transfusion in vivo. Metabolic characterization of SMEs (i.e., CFDA-SE low) vs morphologically-normal end of storage RBCs (i.e., CFDA-SE low) showed that the former are characterized by a complete depletion of acyl-carnitine pools compared to the latter or to fresh RBCs. We thus propose a model where storage promotes lipid peroxidation, which is in turn counteracted by activation of the Lands cycle, a pathway that relies on acyl-carnitine pools to repair lysophospholipids secondary to oxidation of fatty acids in membrane lipids. To determine the translational relevance of this mechanism to RBCs as they age in the bloodstream in vivo, we separated packed RBCs via Percoll density gradients and determined total carnitine pools in each fraction. Our results indicate that the oldest circulating RBCs are not only the smallest, but are also characterized by the lowest levels of carnitine pools. Incubation of the youngest, oldest and intermediate RBC populations with radio-labeled palmitate showed that incorporation of labeled hexadecenoic acid into phosphatidylethanolamines is constrained by carnitine pools in old and average age RBCs, compared to the youngest population. Altogether, our results suggest an important role for L-carnitine levels during RBC aging in vivo and in vitro. As such, carnitine supplementation may represent a viable strategy to boost RBC storage quality and modulate hemolytic propensity, especially in RBCs from donors harboring genetic polymorphism associated with partial ablation of the carnitine transport system. Figure 1 - Levels of carnitine metabolites are reproducible across multiple donations from the 643 REDS RBC Omics donors across two consecutive donations (index and recalled in A), a phenomenon in part explained by genetic polymorphisms to the carnitine transporter SLC22A16 as gleaned by L-carnitine measurements in end of storage units from 13,091 blood donors ( B).

Increased retention of functional mitochondria in mature sickle red blood cells is associated with increased sickling tendency, hemolysis and oxidative stress.

Abnormal retention of mitochondria into mature red blood cells (RBCs) has been recently reported in sickle cell anemia (SCA) but their functionality and their role in the pathophysiology of SCA remain unknown. The presence of mitochondria within RBCs was determined by flow cytometry in 61 SCA patients and 10 healthy donors. Patients were classified according to the percentage of mature RBCs with mitochondria contained in the whole RBC population: low (0-4%), moderate (>4 and 8%). RBC rheological, hematological, RBC senescence and oxidative stress markers were compared between the three groups. RBC senescence and oxidative stress markers were also compared between mature RBC containing mitochondria and those without. The functionality of residual mitochondria in sickle RBCs was measured by high-resolution respirometry assay and showed detectable mitochondrial oxygen consumption in sickle mature RBCs but not in healthy RBCs. Increased levels of mitochondrial reactive oxygen species (ROS) were observed in mature sickle RBCs when incubated with Antimycin A vs without. In addition, mature RBCs retaining mitochondria exhibited greater levels of ROS compared to RBCs without mitochondria, as well as greater Ca2+, lower CD47 and greater phosphatidylserine exposure. Hematocrit and RBC deformability were lower, and the propensity of RBC to sickle under deoxygenation was higher, in the SCA group with a high percentage of mitochondria retention in mature RBCs. This study showed the presence of functional mitochondria in mature sickle RBCs, which could favor RBC sickling and accelerate RBC senescence, leading to increased cellular fragility and hemolysis.

Hyper high haemoglobin content in red blood cells and erythropoietic transitions postnatally in infants of 22 to 26 weeks’ gestation: a prospective cohort study

ObjectiveBlood cell populations, including red blood cells (RBC) unique to the extremely preterm (EPT) infant, are potentially lost due to frequent clinical blood sampling during neonatal intensive care. Currently, neonatal...

Blood crossmatching patterns in a population of killer whales (Orcinus orca) in managed care

AbstractBlood crossmatching is necessary to determine transfusion compatibility between individuals, especially for species for which blood groups have not yet been defined, such as the killer whale (Orcinus orca). This study evaluated methodology for crossmatching in killer whales from a managed care population using individuals of known lineages. Twenty killer whales were evaluated for major or minor crossmatch incompatibilities, determined by evidence of macro‐agglutination. Crossmatching incompatibilities were rarely observed, both when considering 1+ reactions as incompatibilities (~15%; 59/400 pairings with 1+ to 4+) and when omitting 1+ reactions (6%; 24/400 pairings with 2+ to 4+). A universal red blood cell donor within this population (whale T) and universal recipients of red blood cells within this population (whales E, M, O, P, R, S) were identified. Relationships were examined between the most common major crossmatch phenotypes and maternal or paternal lineages. Since these whales have not been previously transfused, the diversity of crossmatch reactions could indicate the presence and diversity of preexisting alloantibodies in killer whale plasma. This study highlights the clinical value of applying a personalized medicine approach to a managed care population.

Evaluation of the detection of the homologous transfusion of a red blood cell concentrate in vivofor antidoping.

Two doping cases of homologous blood transfusion (HBT) during Tokyo 2020 Summer Olympics have shown that more controls are needed. The method of detection using flow cytometry to evaluate the expression of minor blood group antigens from red blood cells (RBCs) and identify different RBC populations is efficient but still complex to perform with multiple antigens detection. Recently, the interest of using forensic DNA analysis was also highlighted as a potential new method to detect HBT, with possibility to start from dried blood spots (DBS) instead of fresh blood. After a first phase of development, a protocol was validated for HBT detection using DNA analysis after extraction from DBS. Presence of a second DNA was clear down to 2% of donor blood in vitro. A flow cytometry protocol was also developed with preparation and analysis in 96-well plates and detection of two different antigens per well using two secondary antibodies with distinct fluorophores. The objective of the project was to evaluate the window of detection of an HBT performed in vivo with 150 mL of RBC concentrate. Blood samples obtained over 7 weeks post-transfusion were analyzed. DNA profiling from DBS was not sensitive enough to detect the presence of a second DNA even 1 day after transfusion. On the contrary, the flow cytometry protocol was very efficient and allowed identification of several double populations of RBC (expressing/non-expressing several antigens) until day 50 post-transfusion. This protocol can be fully validated for a future application to doping control samples.

A report on a modified protocol for flow cytometry-based assessment of blood group erythrocyte antigens potentially suitable for analysis of weak ABO subgroups.

Flow cytometry (FC) has proven its utility in scrutinizing AB antigen expression in red blood cells (RBCs), cooperating with serological tests for accurate blood group typing. However, technical difficulties may impair the characterization of weak ABO subtypes when background noises appear at non-negligible levels. We sought to establish an FC method that could prevent antibody-induced hemagglutination and an increase in cellular autofluorescence, two major issues inherent to RBC-FC analysis of AB expression. We optimized fixatives, multicolor-staining protocols, and sequential gating strategies. Blood samples from weak ABO subtype cases, Bm and Ael , were analyzed with the established protocol. The optimized mixture of glutaraldehyde and formaldehyde successfully generated fixed RBCs resistant to agglutination while maintaining low autofluorescence. These features allowed co-staining of leukocyte- and erythrocyte-markers, which enabled sequential gating strategies facilitating the precise AB antigen analysis in purely single RBCs with minimum background noises. By the established FC analysis, we could detect in the Bm sample a small RBC population exhibiting weak B antigen expression. The assay also proved it feasible to identify a small population (0.04%) of RBCs weakly expressing the A antigen in the Ael sample confirmed as harboring a rare c.816dupG ABO variant allele. The RBC-FC analysis described here allows the detection of AB antigens weakly expressed in RBCs while achieving minimum background noise levels in negative control samples. Overall, the modified protocol provides a quick and reliable assay valuable in transfusion medicine and is potentially applicable to the characterization of rare weak ABO variants.

Molecular Background of Toxic-Substances-Induced Morphological Alterations in the Umbilical Cord Vessels and Fetal Red Blood Cells

The relationship between smoking and human health has been investigated mostly in adults, despite the fact that the chemicals originating from sustained maternal smoking disrupt the carefully orchestrated regulatory cascades in the developing fetus. In this study, we followed molecular alterations in the umbilical cord (UC) vessels and fetal red blood cells (RBCs), which faithfully reflect the in vivo status of the fetus. We showed evidence for the decreased level of DNA-PKcs-positive nuclei in samples with smoking origin, which is associated with the impaired DNA repair system. Furthermore, we pointed out the altered ratio of MMP-9 metalloproteinase and its endogenous inhibitor TIMP-1, which might be a possible explanation for the morphological abnormalities in the UC vessels. The presented in vivo dataset emphasizes the higher vulnerability of the veins, as the primary target for the toxic materials unfiltered by the placenta. All these events become amplified by the functionally impaired fetal RBC population via a crosstalk mechanism between the vessel endothelium and the circulating RBCs. In our ex vivo approach, we looked for the molecular explanation of metal-exposure-induced alterations, where expressions of the selected genes were upregulated in the control group, while samples with smoking origin showed a lack of response, indicative of prior long-term in utero exposure.

Altered Cellular Sedimentation during Apheresis Impacts Outcomes of Peripheral Blood Stem Cell Collection Efficiency in Patients with Sickle Cell Disease

Recent reports have demonstrated the potential for gene therapy as a therapeutic option to achieve a durable cure in patients with sickle cell disease (SCD). However, for these emerging cell therapies, relatively large numbers of peripheral blood hematopoietic stem cells (PB HSCs) are required to generate a therapeutic dose. Outcomes of stem cell collections in patients with SCD are highly variable, at times yielding far fewer numbers of HSCs in the product than predicted by the number of PB CD34+ cells. While the CXCR4 antagonist plerixafor has emerged as a safe and reliable drug to mobilize CD34+ cells in patients with SCD, collection failures continue to occur requiring additional cycles or failure to generate a gene therapy product. We sought to understand the mechanics affecting stem cell sedimentation in real time and posited that SCD disease associated changes to red cells results in altered HSC sedimentation during apheresis, negatively impacting collection. Methods Autologous PB stem cell collections were performed in patients with SCD following mobilization with 240ug/kg plerixafor. To uncover the mechanisms impacting apheresis efficiency for collecting PB HSCs, we devised a method to interrogate the sedimentation of cells in peripheral blood in real time, by interrupting the return collection circuit line. Cellular composition analyses of the collecting interfaces were performed including CD34+ enumeration by flow cytometry, CBC and differential, reticulocyte counts, and surface CD47 expression of red blood cells (RBCs). Results Patients were mobilized with 240ug/kg of plerixafor up to 6 hours before apheresis collection. We collected fewer cells than predicted (3.78 million cells/kg) in these patients with an overall average apheresis collection efficiency of 38%, and a strikingly wide range of 2%-107%. We determined that the lower collection efficiency outcomes were primarily derived when using standard apheresis interface settings. The pre-apheresis PB CD34+ counts were less predictive of total CD34+ cells collected (p=0.012) in patients with SCD (r2=0.2557, p=0.0023) when compared to historical control patients without SCD (r2=0.7638, p<0.0001). Real time measurement of cell counts at standard (Hematocrit 3%, S) and deep (Hematocrit 5%, D) collecting interfaces of the apheresis machine showed a significant decrease in lymphocytes (p=0.0146), increase in monocytes (p=0.0496), and increase enrichment in CD34+ cells at the D interface (Panel A). Enrichment of CD34+ cells correlated with monocyte enrichment and (n=21, r2=0.6706, p<0.0001) and an increased fold change in CD34+ cells between the S and D interfaces correlated with higher PB reticulocyte percentage (r2=0.5295, p=0.0111). Further analysis of the individual collection interfaces revealed that most RBCs were HbS containing despite a PB HbS concentration <30%, consistent with an enrichment for shorter lived sickle red cells. CD47 expression has been previously reported in higher concentrations on the surface of younger RBCs during erythropoiesis. Surface expression of CD47 was found to be significantly higher at both the S and D interfaces compared to the PB of patients, indicating that the accumulation of a younger population of RBCs at the collecting interfaces. As microcytic RBCs have been associated with poor collection efficiencies, the SCD red cell hemoglobin concentration in the PB was used as a marker for size and a significant correlation was determined (r2=0.6086, p=0.0001). Patients with SCD can mobilize PB HSC in response to plerixafor but demonstrate specific characteristics that impede the collection of stem cells. During apheresis, CD34+ stem cells sediment at a deeper hematocrit interface in the buffy coat as a result of displacement by the younger patient-derived population of RBCs. The relative shift in erythrocyte sedimentation requires a corresponding alteration in collection strategies to improve the collection efficiency. In addition to red cell age, other factors that affect red cell buoyancy including iron status or additional globin gene mutations negatively impact apheresis stem cell collections. Full assessment of red cell parameters can identify patients that are at risk for poor stem cell collection outcomes. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal