Objectives To determine whether adults with sickle cell disease (SCD) without glaucoma exhibit subclinical optic neuropathy (ON) on optical coherence tomography (OCT) and to identify genetic, clinical, and biologic correlates of optic nerve thinning. Methods Monocentric, retrospective cross-sectional study of 185 eyes from 96 adults with SCD (116 eyes/59 HbSS; 69 eyes/37 HbSC) and 40 eyes from 20 controls. Spectral-domain OCT measured Bruch’s membrane opening–minimum rim width (BMO-MRW), peripapillary retinal nerve fiber layer (RNFL), and macular ganglion cell complex (GCC). ON was defined as concordant thinning across all three parameters. Patient-clustered models with Holm adjustment compared groups; multivariable clustered logistic regression identified risk factors. Results Compared with controls, SCD eyes showed thinner BMO-MRW, RNFL, and GCC (all p < 0.001). Within SCD, HbSC exhibited greater thinning than HbSS, especially in temporal and superonasal BMO-MRW sectors and RNFL average, inferotemporal, and superotemporal sectors. Proliferative SCR showed more pronounced loss than non-proliferative disease, including lower BMO-MRW, temporal RNFL thinning, and global GCC reduction. Hemoglobin correlated positively with BMO-MRW in HbSS (ρ = 0.41, p = 0.001), hematocrit tended toward a negative association with RNFL in HbSC (ρ=−0.29, p = 0.06), and reticulocytes were inversely associated with GCC in HbSS (ρ=−0.25, p = 0.038) and HbSC (ρ=−0.31, p = 0.038). Older age, recent acute chest syndrome, and ≥ 1 vaso-occlusive crisis within 2 years independently increased ON odds, whereas higher hemoglobin was protective. Conclusions Adults with SCD show OCT-detectable subclinical ON linked to genotype, retinopathy stage, anemia severity, and vaso-occlusive burden; combined BMO-MRW, RNFL, and GCC may aid risk-stratified surveillance.

Objective:Red blood cells (RBCs) must be highly deformable to pass through capillaries narrower than their own diameter for delivering oxygen to the tissues. Ion channels are central regulators of RBC deformability and volume. Gain-of-function mutations in Piezo1, as seen in hereditary xerocytosis, cause RBC dehydration and have been associated with an increased risk of thromboembolism. Here we investigated how pharmacological RBC-Piezo1 activation affects RBC membrane potential, RBC ion content, RBC deformability, coagulation dynamics, and clot structure. Study Design:Blood samples were collected from healthy donors. RBCs were isolated and incubated with Yoda1, a drug known to activate Piezo1. Membrane potential was measured using the Macey-Bennekou-Egée method. Intracellular Na+/K+ content was determined by flame photometry. RBC deformability was measured by ektacytometry. Coagulation dynamics were investigated by rotational thromboelastometry, and clot structure was observed by electron microscopy. Results:Yoda1 treatment led to RBC membrane hyperpolarization, reduced cell volume, a decrease in intracellular K+, an increase in Na+, and a reduction in RBC deformability. ROTEM analysis showed shorter clotting and lysis times in Yoda1-treated samples compared with samples treated with the vehicle (control condition), independently of RBC phosphatidylserine exposure. Electron microscopy revealed structural alterations in Yoda1-treated samples, with less compacted RBCs. Conclusion:Altogether, these findings indicate that Piezo1 activation disrupted RBC ion balance and membrane potential, leading to dehydration and decreased deformability. These alterations contributed to accelerated coagulation and compromised clot structure, suggesting a potential role of Piezo1 in modulating thrombotic risk in RBC-related disorders.

Abstract Background and purpose PIEZO1 mechanosensitive cation channels translate mechanical cues into intracellular Ca 2+ and Na + elevations, enabling cells to respond to physical alterations in their environment. PIEZO1 contributes to red blood cells (RBC) volume homeostasis and gain-of-function PIEZO1 mutations cause hereditary xerocytosis (HX), a rare mostly compensated hemolytic anemia, and aberrant channel activation exacerbates sickling and vascular dysfunction in sickle cell disease. Despite strong genetic and physiological evidence supporting PIEZO1 as a therapeutic target, potent and selective inhibitors are limited, and existing compounds show modest specificity or poorly explored mechanisms. Improved pharmacological tools are needed. Experimental approach We conducted a high-throughput screen of FDA-approved drugs to identify PIEZO1 inhibitors. Compounds were tested at concentrations of 10 µM in a monocytic cell line, using intracellular Ca 2+ elevations evoked by the PIEZO1 agonist Yoda1 as read-out. The inhibitory activity of the best hit was validated and compared to existing PIEZO1 inhibitors using electrophysiological analysis, orthogonal PIEZO1-dependent assays across cell lines and human RBCs. As functional proof, we investigated the impact of three PIEZO1 inhibitors on RBC deformability by ektacytometry, after Yoda1 pre-stimulation. Key results This screen identified Otenabant, a selective Cannabinoid Receptor Type 1 (CB1) antagonist, as a potent PIEZO1 inhibitor. Otenabant dose-dependently inhibited Ca 2+ elevations mediated by endogenous or exogenously expressed human PIEZO1, but was ineffective against mouse Piezo1, revealing species-specific channel differences. Otenabant inhibited mechanosensitive currents elicited by shear stress in fibroblasts and by repeated poking in PIEZO1-expressing HEK-293 cells, altering the currents activation and inactivation kinetics, and prevented Yoda1-induced hyperpolarization in RBCs. Otenabant was able to reverse the negative impact of Yoda1 on RBC deformability. Conclusions and implications These findings demonstrate the utility of Yoda-based screening for discovering PIEZO1 antagonists and identify Otenabant as a promising chemical scaffold for developing selective PIEZO1 inhibitors with therapeutic potential.

This study investigated whether implementing heat training during the final week of a 3-week altitude training camp affects the hematological adaptations and variables monitored during chronic hypoxia. Twenty-three well-trained triathletes (19 males, 4 females) underwent 21 days of altitude training camp in spring (Live-High-Train-High, 1850 m). From day 14 to day 21, participants were split into two groups: a control group (HYPOXIA), which remained in the same condition, while the second group (COMBINED) had a ~1 h cycling session per day conducted in the heat (36°C ± 1°C, 40% ± 5% RH). Training load was the same for both groups. Hematological responses (including hemoglobin mass (Hbmass) and plasma volume (PV)) were assessed. Monitoring included physiological responses at rest (nocturnal oxygen saturation (SpO2) and heart rate, Hooper and Spiegel questionnaires, hydration status) and during exercise (incl. power, SpO2 through 45 min cycling at fixed heart rate). Both Hbmass (3.2% ± 3.1% for HYPOXIA, 3.7% ± 2.9% for COMBINED, p < 0.001) and PV (p = 0.003) increased during the camp, without interaction between groups (p ≥ 0.266). Exercise SpO2 decreased between the end of the second and the third week (p = 0.034, d = 0.583) in the COMBINED group. No difference between groups was detected for the other physiological or perceptual parameters. Adding heat training during the third week of an altitude training camp did not affect the increase in Hbmass or monitoring variables at rest. However, it did not confer any additional PV expansion and was associated with a reduced exercise SpO2.

Blood viscosity is recognized as a key determinant in the pathophysiology of vaso-occlusive crises (VOC) in sickle cell anemia (SCA). However, its longitudinal relationship with changes in VOC frequency over time remains poorly understood. The present study analyzed the associations between the changes in blood rheological parameters and the changes (delta) in the rate of VOC over time in 63 SCA patients. VOC rates (calculated over the 3 years preceding each blood sampling) and biological parameters were measured at two separate occasions, spaced by at least 3 yrs. (mean difference between the two measurements: 5.7 ± 2.0 years). A positive correlation was observed between the delta-VOC rate and the percentages of change in white blood cells, lactate dehydrogenase and blood viscosity. A multivariate linear regression was performed to test the independent association between the delta-VOC rate and the percentages of change in these biological parameters. The model was statistically significant (R2 = 0.47, p < 0.01), and blood viscosity was the only parameter independently associated with the percentage of change in VOC rate (β coefficient = 0.025, 95% CI: 0.009-0.040, p < 0.01). Our study demonstrated that steady-state blood viscosity is a valuable biomarker in SCA, given its associations with temporal variations of VOC frequency.

Abstract The erythrocyte sedimentation rate (ESR) is one of the most widely used laboratory diagnostic parameters in the preliminary assessment of inflammation; indeed, every reader of this work has likely received an ESR assessment in their lifetime. A rapid ESR is a non-specific parameter that provides information about the inflammatory process. Although the origins of this methodology date back to antiquity, the prevailing view that ESR simply reflected particle settling of erythrocytes has recently undergone a paradigm shift: once cell aggregates form a system-spanning network, gravitational collapse of a weak and percolating gel reveals a more complex process reflecting the failure. The apparent non-specific nature of the cells and proteins involved also called into question the medical utility of ESR, at least in well-resourced environments. Here we show a new experimentally derived and physically modelled approach (“supraESR”) that enhances the value and accuracy of ESR for a variety of conditions that exhibit abnormally slow ESR (e.g., sickle cell disease, neuroacanthocytosis syndromes, chronic mountain sickness). We introduce a completely new diagnostic parameter that is based on an established and easily automated measurement method that promises low-cost screening for neuroacanthocytosis syndrome, a group of rare neurodegenerative diseases that are currently detectable only through integration of complex multimodal findings.

Voxelotor, a hemoglobin S polymerization inhibitor, has been shown to reduce anemia in sickle cell anemia (SCA) but its effects on vaso-occlusive crisis frequency are limited. Its recent market withdrawal due to concerns over treatment-related excess mortality highlights the need for a better understanding of its mechanisms of action, especially with similar compounds under development.We investigated, in vitro, the effects of voxelotor on red blood cells (RBCs) from SCA patients, in hypoxia and normoxia. Parameters included: 1) RBC senescence markers including phosphatidylserine (PS) and CD47 exposure, calcium and reactive oxygen species (ROS) content measured with flow cytometry; 2) RBC aggregation assessed by light transmission; 3) RBC deformability using ektacytometry under shear stress, osmotic, and oxygen gradients.Voxelotor decreased RBC PS exposure in both hypoxia and normoxia but increased ROS levels. Voxelotor increased RBC aggregation and RBC deformability, decreased Ohyper (indicating decreased cell hydration state). The extent of RBC deformability increase with voxelotor was negatively correlated with fetal hemoglobin levels.While voxelotor demonstrated beneficial effects on RBC deformability and sickling propensity, its impact on RBC aggregation properties and ROS generation requires further investigation to better understand its different mechanisms of action.

Ultra-endurance running imposes extreme demands on oxygen transport, yet how red blood cells (RBCs) respond at the molecular level remains poorly defined. We integrated plasma and RBC multi-omics with hematology and hemorheology in athletes sampled before and after two trail races of distinct duration: a 40-km marathon (MCC) and a 171-km ultramarathon (UTMB). Both races elicited systemic inflammation, but UTMB was distinguished by marked IL-6 and kynurenine increases, acute-phase protein induction, and profound lipid remodeling. In RBCs, acylcarnitine accumulation, pantothenate depletion, and oxidized lipid species indicated Lands cycle activation, while purine salvage and carboxylate metabolism reflected redox-sensitive rerouting of energy pathways. Proteomics revealed non-random oxidation, particularly methionine oxidation of antioxidant enzymes, metabolic proteins, and proteasome components, correlating with impaired deformability as gleaned by testing of rheological properties. Elevated copper provided an additional correlate of reduced RBC mechanics. Despite minimal signatures of intravascular hemolysis, plasma bilirubin and hypoxanthine rose, consistent with extravascular clearance of damaged RBCs. Collectively, these results demonstrate that ultra-running accelerates RBC aging through inflammatory and oxidative pathways beyond mechanical trauma, linking systemic cytokine responses to molecular lesions, biomechanical dysfunction, and splenic sequestration. These findings not only identify actionable biomarkers of exercise-induced hemolysis but also provide translational insight into oxidative lesions that similarly limit RBC survival in transfusion and inflammatory disease settings.

The aim of the present study was to compare the effects of dalcetrapib and voxelotor on the rheology of red blood cells (RBCs) from sickle cell patients, as well as on hemoglobin oxygen affinity. Oxygen gradient ektacytometry was used to determine RBC deformability in normoxia and hypoxia, as well as the propensity of RBCs to sickle. Hemoglobin oxygen affinity was also measured following dalcetrapib and voxelotor incubation. Both voxelotor and dalcetrapib increased RBC deformability in hypoxia and decreased the propensity of RBCs to sickle under deoxygenation. However, in contrast to voxelotor, the affinity of hemoglobin S (HbS) to oxygen was not affected by dalcetrapib. The combination of both voxelotor and dalcetrapib led to greater RBC rheological improvement. Our findings suggest that dalcetrapib could inhibit RBC sickling during deoxygenation.

BACKGROUND:Sickle cell anemia (SCA) is characterized by recurrent pain, chronic hemolysis, autonomic imbalance, and progressive vascular dysfunction. In sub-Saharan Africa, where access to disease-modifying therapies remains limited, identifying modifiable behavioral determinants such as physical activity (PA) is of particular clinical relevance. This study examined the associations between objectively measured daily step count and clinical, biological, hemorheological, vascular, and autonomic parameters in adults with SCA. METHODS:Ninety-eight adults with SCA were stratified into tertiles according to accelerometer-derived daily step count. Pain burden, renal indices (albuminuria and estimated glomerular filtration rate [eGFR]), hematological and hemorheological parameters, arterial stiffness (carotid-femoral pulse wave velocity), and heart rate variability were assessed. RESULTS:Higher daily step counts were associated with less frequent intense pain, reduced blood viscosity, and a higher hematocrit-to-viscosity ratio. More active participants also exhibited lower arterial stiffness and greater parasympathetic modulation. A graded, linear pattern was observed across tertiles for most outcomes. Although eGFR was positively associated with physical activity, this relationship was largely explained by age differences between groups. DISCUSSION:Greater daily physical activity is associated with a more favorable clinical and physiological profile in adults with SCA. While causality cannot be inferred, daily PA may represent both a marker of health status and a potential target for preventive strategies in this population. TRIAL REGISTRATION:UMIN000042826.

Red blood cell (RBC) exchanges (RCE) are particularly efficient to treat and prevent complications in patients with sickle cell anemia (SCA). However, the low weight of young children is a barrier to their use. Spectra Optia is a therapeutic apheresis platform that enables automatic priming to prevent hemodynamic complications in low-weight children. The easiest method is to use albumin for priming, which is allowed by the software. We conducted a retrospective monocenter analysis of the feasibility, safety, and efficacy of albumin priming during RCE (RCE/Alb-primed) in 19 children weighing 12 to 23 kg for a total of 153 sessions. They were treated either on an emergency basis (8 children, 8 sessions), before surgery (2 children, 4 sessions) or as part of a RCE program (9 children, 141 sessions). Indications of RCE/Alb-primed sessions included: (i) an extracorporeal volume of the kit equal to 15% of the child's total blood volume, (ii) a weight of less than 20 kg, or (iii) a weight between 20 and 25 kg with a hematocrit (Hct) of 20% or less. We monitored Grade 2 adverse events (AEs) during the sessions, in extenso decreased blood pressure, increased heart rate and fatigue. Post-apheresis hematocrit and the fraction of cell remaining (FCR) values after RCE were compared to the expected ones. A low incidence of complications was observed in the 153 RCE/Alb-primed sessions with only 1 episodes of transient Grade 2 AEs. Post-apheresis Hct and FCR reached expected values with the RCE/Alb-primed method. In conclusion, RCE/Alb-primed seems to be safe and efficient in young SCA children and should be proposed systematically for curative RCE or prophylactic programs.

Patients with sickle cell anemia (SCA) have long been discouraged from physical activity (PA). The aim of the present study was to assess the impact of increasing daily step counts on physical fitness, pain and vascular function in patients with SCA. Thirty-eight patients with SCA were recruited and equipped with a Fitbit wrist-worn accelerometer-based PA tracker for five weeks to objectively quantify their baseline daily step counts. Patients were then randomly assigned to one of three groups: 1) control group - no specific information regarding PA was given for eight weeks (N=12); 2) PA1 group - daily step counts increased by 25% of baseline for eight weeks (N=12); 3) PA2 group - daily step counts increased by 25% for four weeks, then by 50% for an additional four weeks (N=14). Pain intensity and frequency decreased after the intervention in the PA1 and PA2 groups. In addition, patients from these two groups increased the distance walked in six minutes. Arterial stiffness decreased in both PA1 and PA2 groups, without any change in the autonomic nervous system activity. Several inflammatory markers slightly decreased in the PA2 group. Incubation of cultured endothelial cells with patient plasma showed a decrease in the percentage of ICAM-1 positive cells in the PA2 group. This study is the first to show that adopting a simple approach to increase daily PA (i.e., increasing daily step count by 25-50%) for eight weeks is sufficient to decrease pain, and improve physical condition and vascular function of patients with SCA.

Anemia, a global health challenge affecting a quarter of the global population, results from diverse causes such as nutritional deficiencies, chronic diseases, and genetic factors. It disproportionately impacts women of reproductive age and children, leading to significant morbidity and mortality. While high-altitude populations face unique diagnostic challenges due to natural hemoglobin increases, the current World Health Organization cutoffs often overestimate anemia in these regions. Altitude corrections significantly alter prevalence rates, particularly in South American children, leading to misdiagnosis. Proposed solutions include population-specific thresholds and iron status markers like serum hepcidin, though economic constraints and limited test availability remain challenges. Tailored strategies informed by genetic research highlight adaptations in Tibetan and Ethiopian highlanders, demonstrating the need for region-specific approaches. Socioeconomic factors exacerbate anemia in high-altitude areas. Addressing anemia requires updated diagnostic criteria, personalized strategies, and increased awareness to ensure accurate assessments and interventions in diverse populations, especially those residing at high altitudes.

Millet, Grégoire P, and Philippe Connes. Sickle cell trait is a risk factor for another form of altitude illness. High Alt Med Biol. 27:57-59, 2026.-Acute mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema have been widely investigated. In this letter, we claim that beyond these three altitude illnesses, one cannot rule out an additional serious concern related to altitude exposure in a particular population; the individuals with sickle cell trait.

Gaucher Disease (GD) is a rare genetic disorder characterized by a deficiency in the enzyme glucocerebrosidase, leading to the accumulation of glucosylceramide in various cells, including red blood cells (RBCs). This accumulation results in altered biomechanical properties and rheological behavior of RBCs, which may play an important role in blood rheology and the development of bone infarcts, avascular necrosis (AVN) and other bone diseases associated with GD. In this study, dissipative particle dynamics (DPD) simulations are employed to investigate the biomechanics and rheology of blood and RBCs in GD under various flow conditions. The model incorporates the unique characteristics of GD RBCs, such as decreased deformability and increased aggregation properties, and aims to capture the resulting changes in RBC biophysics and blood viscosity. This study is the first to explore the Young's modulus and aggregation parameters of GD RBCs by validating simulations with confocal imaging and experimental RBC disaggregation thresholds. Through in silico simulations, we examine the impact of hematocrit, RBC disaggregation threshold, and cell stiffness on blood viscosity in GD. The results reveal three distinct domains of GD blood viscosity based on shear rate: the aggregation domain, where the RBC disaggregation threshold predominantly influences blood viscosity; the transition area, where both RBC aggregation and stiffness impact on blood viscosity; and the stiffness domain, where the stiffness of RBCs emerges as the primary determinant of blood viscosity. By analyzing RBC mechanical properties and blood viscosity in relation to bone disease, we find that the RBC aggregation properties, deformability, and blood viscosity, may contribute to its onset. These findings enhance our understanding of how changes in RBC properties impact on blood viscosity and may affect bone health, offering a partial explanation for the bone complications observed in GD patients.

Abnormal retention of mitochondria in mature red blood cells (RBC) 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 RBC was determined by flow cytometry in 61 SCA patients and ten healthy donors. Patients were classified according to the percentage of mature RBC with mitochondria contained in the whole RBC population: low (0-4%), moderate (>4% and <8%), or high level (>8%). RBC rheological, hematological, 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 RBC was measured by high-resolution respirometry assay and showed detectable mitochondrial oxygen consumption in sickle mature RBC but not in healthy RBC. Increased levels of mitochondrial reactive oxygen species were observed in mature sickle RBC when incubated with Antimycin A versus without. In addition, mature RBC retaining mitochondria exhibited greater levels of reactive oxygen species compared to RBC 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 RBC. This study showed the presence of functional mitochondria in mature sickle RBC, which could favor RBC sickling and accelerate RBC senescence, leading to increased cellular fragility and hemolysis.

Altitude training camps are frequently used by endurance athletes to increase total hemoglobin mass (Hbmass) and potentially aerobic performance. However, the effects of such intervention on red blood cell (RBC) properties remain largely unexplored, although these factors could influence the physiological responses following altitude training. This self-controlled study investigated the effects of a "live high-train high" (LHTH) altitude training camp on RBC senescence and Hbmass in nine elite swimmers. Participants performed two 4-wk training camps, one at 1,850 m altitude (LHTH) and the other one at sea level. Hbmass, hematocrit, RBC senescence, and deformability were measured before and immediately after both training camps, and again 10 days after the LHTH camp. A 400-m freestyle "all-out" swimming test was performed before and 10 days after each training camp (n = 6). Hbmass, hematocrit, CD71-positive RBCs, RBC phosphatidylserine exposure, and the percentage of RBC retaining mitochondria were increased after LHTH camp. RBC reactive oxygen species content was increased after both interventions, whereas RBC deformability and CD47 exposure remained unchanged. Although LHTH camp was accompanied by an increase in RBC senescence markers, Hbmass remained increased 10 days post-LHTH. Although 400-m swimming performance was not significantly improved 10 days post-LHTH (-3.8 ± 5.1 s), its change was associated with Hbmass variations. These results indicate that a 4-wk LHTH camp (1,850 m) is accompanied by an increase in Hbmass, which persists for up to 10 days after the camp, despite the increase in RBC senescence markers, a persistence that could be explained by a prolonged RBC survival.NEW & NOTEWORTHY This self-controlled study investigated the effects of a "live high-train high" (LHTH) altitude training camp on RBC senescence and Hbmass in nine swimmers. Despite increased RBC senescence markers, Hbmass increases during LHTH camp and remained elevated 10 days postaltitude, a persistence that could be due to an extended RBC lifespan. The self-controlled design, where each athlete completed both an LHTH training camp and a sea-level training camp, enables a rigorous assessment of the altitude effects.

PurposeRed blood cell (RBC) senescence and blood rheology during ultraendurance running events appear to be affected differently depending on the race distance. The physiological mechanisms underlying these differences are poorly understood.MethodsWe investigated the effects of three different ultra-trail running races performed in La Reunion Island (Mascareignes, "the 70 km," 70 km/4000 m D+; Trail Du Bourbon, "the 100 km," 100 km/6090 m D+; Diagonale des Fous, "the 170 km," 170 km/10,500 m D+) on RBC oxidative stress, RBC senescence, and blood rheology in 66 finishers (18 "70 km," 24 "100 km," and 24 "170 km").ResultsWe observed a decrease in RBC antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, and catalase) positively related to the race distance and an increase in RBC H2O2 and isoprostane levels after the three races. However, RBC H2O2 and isoprostane levels were found to be higher after the 70-km race compared with the 170-km and the 100-km races. RBC phosphatidylserine externalization increased over baseline value after the 70-km race only. Chymotrypsin-like and trypsin-like activities of the RBC proteasome were decreased after all races compared with before. RBC-derived microparticles (RBC-MP) were increased after the 170-km and the 70-km races. Despite increased RBC senescence markers, RBC deformability increased after the three races. Blood viscosity was differently affected by the three races with a decrease at low shear rate after the two longest races (the 170 km and the 100 km) and an increase at high shear rate after the shortest one (the 70 km).ConclusionsOur results confirm that ultraendurance running events differently affect RBC senescence markers and blood viscosity depending on the race distance and suggest that RBC oxidative stress could play a key role in the observed alterations.