Could oxygen gradient ektacytometry help to detect sickle cell trait carriers at risk for kidney disorders or exercise-related complications?

The study of Ellsworth et al. (Br J Haematol, 2024) demonstrated the usefulness of oxygen gradient ektacytometry technique to better identify the physiological parameters that could increase the risk of sickling of red blood cells (RBCs) from sickle cell trait (SCT) carriers. Oxygen gradient ektacytometry combined with pH and osmolality modulations could help in identifying SCT carriers at risk for kidney disorders or exercise-related complications. Other factors than the percentages of haemoglobin S are probably involved in the propensity of RBCs from SCT carriers to sickle during deoxygenation. Commentary on: Ellsworth et al. Hypertonicity and/or acidosis induce marked rheological changes under hypoxic conditions in sickle trait red blood cells. Br J Haematol 2024; 205:1565-1569.

Controversies in the pathophysiology of leg ulcers in sickle cell disease.

Patients with sickle cell disease (SCD) often experience painful vaso-occlusive crises and chronic haemolytic anaemia, as well as various acute and chronic complications, such as leg ulcers. Leg ulcers are characterized by their unpredictability, debilitating pain and prolonged healing process. The pathophysiology of SCD leg ulcers is not well defined. Known risk factors include male gender, poor social conditions, malnutrition and a lack of compression therapy when oedema occurs. Leg ulcers typically start with spontaneous pain, followed by induration, hyperpigmentation, blister formation and destruction of the epidermis. SCD is characterized by chronic haemolysis, increased oxidative stress and decreased nitric oxide bioavailability, which promote ischaemia and inflammation and consequently impair vascular function in the skin. This cutaneous vasculopathy, coupled with venostasis around the ankle, creates an ideal environment for local vaso-occlusive crises, which can result in the development of leg ulcers that resemble arterial ulcers. Following the development of the ulcer, healing is hindered as a result of factors commonly observed in venous ulceration, including venous insufficiency, oedema and impaired angiogenesis. All of these factors are modulated by genetic factors. However, our current understanding of these genetic factors remains limited and does not yet enable us to accurately predict ulceration susceptibility.

Impaired microvascular function in patients with sickle cell anemia and leg ulcers improved with healing.

Leg Ulcer (LU) pathophysiology is still not well understood in sickle cell anaemia (SCA). We hypothesised that SCA patients with LU would be characterised by lower microvascular reactivity. The aim of the present study was to compare the microcirculatory function (transcutaneous oxygen pressure (TcPO2) on the foot and laser Doppler flowmetry on the arm) and several blood biological parameters between nine SCA patients with active LU (LU+) and 56 SCA patients with no positive history of LU (LU-). We also tested the effects of plasma from LU+ and LU- patients on endothelial cell activation. We observed a reduction of the TcPO2 in LU+ compared to LU- patients. In addition, LU+ patients exhibited lower cutaneous microvascular vasodilatory capacity in response to acetylcholine, current and local heating compared to LU- patients. Inflammation and endothelial cell activation in response to plasma did not differ between the two groups. Among the nine patients from the LU+ group, eight were followed and six achieved healing in 4.4 ± 2.5 months. Among thus achieving healing, microvascular vasodilatory capacity in response to acetylcholine, current and local heating and TcPO2 improved after healing. In conclusion, microcirculatory function is impaired in patients with LU, and improves with healing.

Oxygen release from hemoglobin has limited effects on mitochondrial respiration measured from red blood cells. Reply to the Comment on "Increased retention of functional mitochondria in mature sickle red blood cells is associated with increased sickling tendency, hemolysis and oxidative stress".

Not available.

Are coagulation profiles in Andean highlanders with excessive erythrocytosis favouring hypercoagulability?

Chronic mountain sickness is a maladaptive syndrome that affects individuals living permanently at high altitude and is characterized primarily by excessive erythrocytosis (EE). Recent results concerning the impact of EE in Andean highlanders on clotting and the possible promotion of hypercoagulability, which can lead to thrombosis, were contradictory. We assessed the coagulation profiles of Andeans highlanders with and without excessive erythrocytosis (EE+ and EE-). Blood samples were collected from 30 EE+ and 15 EE- in La Rinconada (Peru, 5100-5300 m a.s.l.), with special attention given to the sampling pre-analytical variables. Rotational thromboelastometry tests were performed at both native and normalized (40%) haematocrit using autologous platelet-poor plasma. Thrombin generation, dosages of clotting factors and inhibitors were measured in plasma samples. Data were compared between groups and with measurements performed at native haematocrit in 10 lowlanders (LL) at sea level. At native haematocrit, in all rotational thromboelastometry assays, EE+ exhibited hypocoagulable profiles (prolonged clotting time and weaker clot strength) compared with EE- and LL (all P < 0.01). At normalized haematocrit, clotting times were normalized in most individuals. Conversely, maximal clot firmness was normalized only in FIBTEM and not in EXTEM/INTEM assays, suggesting abnormal platelet activity. Thrombin generation, levels of plasma clotting factors and inhibitors, and standard coagulation assays were mostly normal in all groups. No highlanders reported a history of venous thromboembolism based on the dedicated survey. Collectively, these results indicate that EE+ do not present a hypercoagulable profile potentially favouring thrombosis.

Plasma monomeric ApoA1 and high-density lipoprotein bound ApoA1 are markedly decreased and associated with low levels of lipophilic antioxidants in sickle cell disease: A potential new pathway for therapy.

Patients with sickle cell disease (SCD) exhibit high levels of reactive oxygen species and low plasma levels of lipophilic antioxidants, which may contribute to end-organ damage and disease sequelae. Apolipoprotein A1, the major apolipoprotein of high-density lipoprotein (HDL), is mainly secreted by the intestine and liver in the form of monomeric ApoA1 (mApoA1) present in plasma. Cholesterol and α-tocopherol are delivered to ApoA1 via the ATP-binding cassette transporter, subfamily A, member 1 (ABCA1). We measured cholesterol, mApoA1, ApoA1, and lipophilic antioxidants in the plasma of 17 patients with SCD and 40 healthy volunteers. Mean HDL cholesterol (-C) levels in SCD patients and healthy subjects were 59.3 and 48.1 mg/dL, respectively, and plasma lutein, zeaxanthin, and α-tocopherol were 64.0%, 68.7%, and 9.1% lower, respectively. To compare SCD to healthy subjects with similar HDL-C, we also performed subgroup analyses of healthy subjects with HDL-C above or below the mean. In SCD, the mApoA1 level was 30.4 µg/mL; 80% lower than 141 µg/mL measured in healthy volunteers with similar HDL-C (56.7 mg/dL). The mApoA1 level was also 38.4% greater in the higher versus lower HDL-C subgroups (p = .002). In the higher HDL-C subgroup, lutein and zeaxanthin transported by HDL were 48.9% (p = .01) and 41.9% (p = .02) higher, respectively, whereas α-tocopherol was 31.7% higher (p = .003), compared to the lower HDL-C subgroup. Plasma mApoA1 may be a marker of the capacity of HDL to capture and deliver liposoluble antioxidants, and treatments which raise HDL may benefit patients with high oxidative stress as exemplified by SCD.

Exercise and training in sickle cell disease: Safety, potential benefits, and recommendations.

Sickle cell disease (SCD) is a genetic disorder characterized by complex pathophysiological mechanisms leading to vaso-occlusive crisis, chronic pain, chronic hemolytic anemia, and vascular complications, which require considerations for exercise and physical activity. This review aims to elucidate the safety, potential benefits, and recommendations regarding exercise and training in individuals with SCD. SCD patients are characterized by decreased exercise capacity and tolerance. Acute intense exercise may be accompanied by biological changes (acidosis, increased oxidative stress, and dehydration) that could increase the risk of red blood cell sickling and acute clinical complications. However, recent findings suggest that controlled exercise training is safe and well tolerated by SCD patients and could confer benefits in disease management. Regular endurance exercises of submaximal intensity or exercise interventions incorporating resistance training have been shown to improve cardiorespiratory and muscle function in SCD, which may improve quality of life. Recommendations for exercise prescription in SCD should be based on accurate clinical and functional evaluations, taking into account disease phenotype and cardiorespiratory status at rest and in response to exercise. Exercise programs should include gradual progression, incorporating adequate warm-up, cool-down, and hydration strategies. Exercise training represents promising therapeutic strategy in the management of SCD. It is now time to move through the investigation of long-term biological, physiological, and clinical effects of regular physical activity in SCD patients.

Making a virtue out of an evil: Are red blood cells from chronic mountain sickness patients eligible for transfusions?

We investigated highlanders, permanently living at an altitude of 5100 m and compared Chronic Mountain Sickness (CMS) patients with control volunteers. While we found differences in systemic parameters such as blood oxygen content, hematocrit, hemoglobin concentration, and blood viscosity, the mechanical and rheological properties of single red blood cells did not differ between the two investigated groups.

Influence of storage and buffer composition on the mechanical behavior of flowing red blood cells.

On-chip study of blood flow has emerged as a powerful tool to assess the contribution of each component of blood to its overall function. Blood has indeed many functions, from gas and nutrient transport to immune response and thermal regulation. Red blood cells play a central role therein, in particular through their specific mechanical properties, which directly influence pressure regulation, oxygen perfusion, or platelet and white cell segregation toward endothelial walls. As the bloom of in-vitro studies has led to the apparition of various storage and sample preparation protocols, we address the question of the robustness of the results involving cell mechanical behavior against this diversity. The effects of three conservation media (EDTA, citrate, and glucose-albumin-sodium-phosphate) and storage time on the red blood cell mechanical behavior are assessed under different flow conditions: cell deformability by ektacytometry, shape recovery of cells flowing out of a microfluidic constriction, and cell-flipping dynamics under shear flow. The impact of buffer solutions (phosphate-buffered saline and density-matched suspension using iodixanol/Optiprep) are also studied by investigating individual cell-flipping dynamics, relative viscosity of cell suspensions, and cell structuration under Poiseuille flow. Our results reveal that storing blood samples up to 7 days after withdrawal and suspending them in adequate density-matched buffer solutions has, in most experiments, a moderate effect on the overall mechanical response, with a possible rapid evolution in the first 3 days after sample collection.

Metabolic Profile of Individuals with and without Type 2 Diabetes from Sub-Saharan Africa.

Epidemiological data predicts that sub-Saharan Africa will have the largest increase in type 2 diabetes (T2D) prevalence over the next two decades. Metabolomics studies have identified biomarkers that could improve T2D diagnosis and follow-up. However, no studies have characterized the metabolome of people from sub-Saharan Africa. Plasma samples from Senegalese individuals with T2D (n = 31) or without T2D (n = 34) were compared using measures of oxidative stress damage and plasma antioxidant enzyme activity and mass-spectrometry-based metabolomics analyses. Results showed that glucose, lactate, and tricarboxylic acid metabolites (fumarate, malate, and succinate) were increased in the T2D group, suggesting alterations in glycolysis and mitochondrial dysfunction. Several amino acids (leucine, isoleucine, valine, and tryptophan) and long-to-very-long-chain fatty acids were higher in the T2D group. Finally, elevated levels of ketone bodies and acylcarnitines were observed along with increased levels of oxidative stress damage and antioxidant activity. In conclusion, the T2D group exhibited modifications in metabolites previously shown to be associated with T2D risk in populations from other areas of the world. Future studies should seek to test whether these metabolites could be used as predictors for T2D-related complications in people from sub-Saharan Africa.

Expedition 5300: limits of human adaptations in the highest city in the world.

Exposure to chronic hypobaric hypoxia imposes a significant physiological burden to more than 80 million humans living above 2500 m throughout the world. Among them, 50 000 live in the world's highest city, La Rinconada, located at 5000-5300 m in southern Peru. Expedition 5300 is the first scientific and medical programme led in La Rinconada to investigate the physiological adaptations and altitude-related health issues in this unique population. Dwellers from La Rinconada have very high haemoglobin concentration (20.3 ± 2.4 g/dL; n = 57) and those with chronic mountain sickness (CMS) exhibit even higher concentrations (23.1 ± 1.7 g/dL; n = 150). These values are associated with large total haemoglobin mass and blood volume, without an associated iron deficit. These changes in intravascular volumes lead to a substantial increase in blood viscosity, which is even larger in CMS patients. Despite these large haematological changes, 24 h blood pressure monitoring is essentially normal in La Rinconada, but some results suggest impaired vascular reactivity. Echocardiography revealed large right heart dilatation and high pulmonary arterial pressure as well as left ventricle concentric remodelling and grade I diastolic dysfunction. These changes in heart dimension and function tend to be more severe in highlanders with CMS. Polygraphy evaluations revealed a large reduction in nocturnal pulse oxygen saturation (median SpO2  = 79%), which is even more severe in CMS patients who also tended to show a higher oxygen desaturation index. The population of La Rinconada offers a unique opportunity to investigate the human responses to chronic severe hypoxia, at an altitude that is probably close to the maximum altitude human beings can permanently tolerate without presenting major health issues.

Association of haemolysis markers, blood viscosity and microcirculation function with organ damage in sickle cell disease in sub-Saharan Africa (the BIOCADRE study).

Sickle cell anaemia (SCA) is a monogenic disease with a highly variable clinical course. We aimed to investigate associations between microvascular function, haemolysis markers, blood viscosity and various types of SCA-related organ damage in a multicentric sub-Saharan African cohort of patients with SCA. In a cross-sectional study, we selected seven groups of adult patients with SS phenotype in Dakar and Bamako based on the following complications: leg ulcer, priapism, osteonecrosis, retinopathy, high tricuspid regurgitant jet velocity (TRV), macro-albuminuria or none. Clinical assessment, echocardiography, peripheral arterial tonometry, laboratory tests and blood viscosity measurement were performed. We explored statistical associations between the biological parameters and the six studied complications. Among 235 patients, 58 had high TRV, 46 osteonecrosis, 43 priapism, 33 leg ulcers, 31 retinopathy and 22 macroalbuminuria, whereas 36 had none of these complications. Multiple correspondence analysis revealed no cluster of complications. Lactate dehydrogenase levels were associated with high TRV, and blood viscosity was associated with retinopathy and the absence of macroalbuminuria. Despite extensive phenotyping of patients, no specific pattern of SCA-related complications was identified. New biomarkers are needed to predict SCA clinical expression to adapt patient management, especially in Africa, where healthcare resources are scarce.

Piezo1 activation augments sickling propensity and the adhesive properties of sickle red blood cells in a calcium-dependent manner.

Haemoglobin S polymerization in the red blood cells (RBCs) of individuals with sickle cell anaemia (SCA) can cause RBC sickling and cellular alterations. Piezo1 is a mechanosensitive protein that modulates intracellular calcium (Ca2+ ) influx, and its activation has been associated with increased RBC surface membrane phosphatidylserine (PS) exposure. Hypothesizing that Piezo1 activation, and ensuing Gárdos channel activity, alter sickle RBC properties, RBCs from patients with SCA were incubated with the Piezo1 agonist, Yoda1 (0.1-10 µM). Oxygen-gradient ektacytometry and membrane potential measurement showed that Piezo1 activation significantly decreased sickle RBC deformability, augmented sickling propensity, and triggered pronounced membrane hyperpolarization, in association with Gárdos channel activation and Ca2+ influx. Yoda1 induced Ca2+ -dependent adhesion of sickle RBCs to laminin, in microfluidic assays, mediated by increased BCAM binding affinity. Furthermore, RBCs from SCA patients that were homo-/heterozygous for the rs59446030 gain-of-function Piezo1 variant demonstrated enhanced sickling under deoxygenation and increased PS exposure. Thus, Piezo1 stimulation decreases sickle RBC deformability, and increases the propensities of these cells to sickle upon deoxygenation and adhere to laminin. Results support a role of Piezo1 in some of the RBC properties that contribute to SCA vaso-occlusion, indicating that Piezo1 may represent a potential therapeutic target molecule for this disease.

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 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.

Adverse effects of delta-9-tetrahydrocannabinol on sickle red blood cells.

THC triggers a pronounced entry of Ca2+ , which may be deleterious, into sickle cell red blood cells via activation of the TRPV2 channel.

Sublingual Microcirculation Specificity of Sickle Cell Patients: Morphology of the Microvascular Bed, Blood Rheology, and Local Hemodynamics.

Patients with sickle cell disease (SCD) have poorly deformable red blood cells (RBC) that may impede blood flow into microcirculation. Very few studies have been able to directly visualize microcirculation in humans with SCD. Sublingual video microscopy was performed in eight healthy (HbAA genotype) and four sickle cell individuals (HbSS genotype). Their hematocrit, blood viscosity, red blood cell deformability, and aggregation were individually determined through blood sample collections. Their microcirculation morphology (vessel density and diameter) and microcirculation hemodynamics (local velocity, local viscosity, and local red blood cell deformability) were investigated. The De Backer score was higher (15.9 mm-1) in HbSS individuals compared to HbAA individuals (11.1 mm-1). RBC deformability, derived from their local hemodynamic condition, was lower in HbSS individuals compared to HbAA individuals for vessels < 20 µm. Despite the presence of more rigid RBCs in HbSS individuals, their lower hematocrit caused their viscosity to be lower in microcirculation compared to that of HbAA individuals. The shear stress for all the vessel diameters was not different between HbSS and HbAA individuals. The local velocity and shear rates tended to be higher in HbSS individuals than in HbAA individuals, notably so in the smallest vessels, which could limit RBC entrapment into microcirculation. Our study offered a novel approach to studying the pathophysiological mechanisms of SCD with new biological/physiological markers that could be useful for characterizing the disease activity.

Autonomic and Vascular Responses during Reactive Hyperemia in Healthy Individuals and Patients with Sickle Cell Anemia.

Background and Objectives: To compare autonomic and vascular responses during reactive hyperemia (RH) between healthy individuals and patients with sickle cell anemia (SCA). Materials and Methods: Eighteen healthy subjects and 24 SCA patients were subjected to arterial occlusion for 3 min at the lower right limb level. The pulse rate variability (PRV) and pulse wave amplitude were measured through photoplethysmography using the Angiodin® PD 3000 device, which was placed on the first finger of the lower right limb 2 min before (Basal) and 2 min after the occlusion. Pulse peak intervals were analyzed using time-frequency (wavelet transform) methods for high-frequency (HF: 0.15-0.4) and low-frequency (LF: 0.04-0.15) bands, and the LF/HF ratio was calculated. Results: The pulse wave amplitude was higher in healthy subjects compared to SCA patients, at both baseline and post-occlusion (p < 0.05). Time-frequency analysis showed that the LF/HF peak in response to the post-occlusion RH test was reached earlier in healthy subjects compared to SCA patients. Conclusions: Vasodilatory function, as measured by PPG, was lower in SCA patients compared to healthy subjects. Moreover, a cardiovascular autonomic imbalance was present in SCA patients with high sympathetic and low parasympathetic activity in the basal state and a poor response of the sympathetic nervous system to RH. Early cardiovascular sympathetic activation (10 s) and vasodilatory function in response to RH were impaired in SCA patients.

Hypoxia briefly increases diuresis but reduces plasma volume by fluid redistribution in women.

We have recently reported that hypobaric hypoxia (HH) reduces plasma volume (PV) in men by decreasing total circulating plasma protein (TCPP). Here, we investigated whether this applies to women and whether an inflammatory response and/or endothelial glycocalyx shedding could facilitate the TCCP reduction. We further investigated whether acute HH induces a short-lived diuretic response that was overlooked in our recent study, where only 24-h urine volumes were evaluated. In a strictly controlled crossover protocol, 12 women underwent two 4-day sojourns in a hypobaric chamber: one in normoxia (NX) and one in HH equivalent to 3,500-m altitude. PV, urine output, TCPP, and markers for inflammation and glycocalyx shedding were repeatedly measured. Total body water (TBW) was determined pre- and postsojourns by deuterium dilution. PV was reduced after 12 h of HH and thereafter remained 230-330 mL lower than in NX (P < 0.0001). Urine flow was 45% higher in HH than in NX throughout the first 6 h (P = 0.01) but lower during the second half of the first day (P < 0.001). Twenty-four-hour urine volumes (P ≥ 0.37) and TBW (P ≥ 0.14) were not different between the sojourns. TCPP was lower in HH than in NX at the same time points as PV (P < 0.001), but inflammatory or glycocalyx shedding markers were not consistently increased. As in men, and despite initially increased diuresis, HH-induced PV contraction in women is driven by a loss of TCPP and ensuing fluid redistribution, rather than by fluid loss. The mechanism underlying the TCPP reduction remains unclear but does not seem to involve inflammation or glycocalyx shedding.NEW & NOTEWORTHY This study is the first to investigate the mechanisms underlying plasma volume (PV) contraction in response to hypoxia in women while strictly controlling for confounders. PV contraction in women has a similar time course and magnitude as in men and is driven by the same mechanism, namely, oncotically driven redistribution rather than loss of fluid. We further report that hypoxia facilitates an increase in diuresis, that is, however, short-lived and of little relevance for PV regulation.

Plasma microparticles of sickle patients during crisis or taking hydroxyurea modify endothelium inflammatory properties.

Microparticles (MPs) are submicron extracellular vesicles exposing phosphatidylserine (PS), detected at high concentration in the circulation of sickle cell anemia (SS) patients. Several groups studied the biological effects of MPs generated ex vivo. Here, we analyzed for the first time the impact of circulating MPs on endothelial cells (ECs) from 60 sickle cell disease (SCD) patients. MPs were collected from SCD patients and compared with MPs isolated from healthy individuals (AA). Other plasma MPs were purified from SS patients before and 2 years after the onset of hydroxyurea (HU) treatment or during a vaso-occlusive crisis and at steady-state. Compared with AA MPs, SS MPs increased EC ICAM-1 messenger RNA and protein levels, as well as neutrophil adhesion. We showed that ICAM-1 overexpression was primarily caused by MPs derived from erythrocytes, rather than from platelets, and that it was abolished by MP PS capping using annexin V. MPs from SS patients treated with HU were less efficient to induce a proinflammatory phenotype in ECs compared with MPs collected before therapy. In contrast, MPs released during crisis increased ICAM-1 and neutrophil adhesion levels, in a PS-dependent manner, compared with MPs collected at steady-state. Furthermore, neutrophil adhesion was abolished by a blocking anti-ICAM-1 antibody. Our study provides evidence that MPs play a key role in SCD pathophysiology by triggering a proinflammatory phenotype of ECs. We also uncover a new mode of action for HU and identify potential therapeutics: annexin V and anti-ICAM-1 antibodies.

Brain injury pathophysiology study by a multimodal approach in children with sickle cell anemia with no intra or extra cranial arteriopathy.

Despite its high prevalence in children with sickle cell anemia (SCA), the pathophysiology of silent cerebral infarcts (SCI) remains elusive. The main objective of this study was to explore the respective roles of major determinants of brain perfusion in SCA children with no past or current history of intracranial or extracranial vasculopathy. We used a multimodal approach based notably on perfusion imaging arterial spin labeling (ASL) magnetic resonance imaging (MRI) and near infra-red spectroscopy (NIRS), as well as biomarkers reflecting blood rheology and endothelial activation. Out of 59 SCA patients (mean age 11.4±3.9 yrs), eight (13%) had a total of 12 SCI. Children with SCI had a distinctive profile characterized by decreased blood pressure, impaired blood rheology, increased P-selectin levels, and marked anemia. Although ASL perfusion and oximetry values did not differ between groups, comparison of biological and clinical parameters according to the level of perfusion categorized in terciles showed an independent association between high perfusion and increased sP-selectin, decreased red blood cell deformability, low hemoglobin F level, increased blood viscosity and no a-thalassemia deletion. NIRS measurements did not yield additional novel results. Altogether, these findings argue for early MRI detection of SCI in children with no identified vasculopathy and suggest a potential role for ASL as an additional screening tool. Early treatment targeting hemolysis, anemia and endothelial dysfunction should reduce the risk of this under diagnosed and serious complication.