Effects of Poloxamer 188 on red blood cell membrane properties in sickle cell anaemia

Vaso‐occlusive crisis (VOC) is the main acute complication in sickle cell anaemia (SS) and several clinical trials are investigating different drugs to improve the clinical severity of SS patients. A phase III study is currently exploring the profit of Velopoloxamer in SS during VOCs. We analysed, in‐vitro, the effect of poloxamer (P188) on red blood cell (RBC) properties by investigating haemorheology, mechanical and adhesion functions using ektacytometry, microfluidics and dynamic adhesion approaches, respectively. We show that poloxamer significantly reduces blood viscosity, RBC aggregation and adhesion to endothelial cells, supporting the beneficial use of this molecule in SS therapy.     

An exploratory study of physiological correlates of neurodevelopmental delay in infants with sickle cell anaemia

This study aimed to investigate whether infants with sickle cell anaemia (SCA) are at risk of neurodevelopmental delay, and whether any delay is associated with SCA pathology. Twenty-eight infants (14 SCA; 14 age- and ethnic-similar controls) were assessed longitudinally with the Bayley Infant Neurodevelopmental Screener (BINS) at 3, 9 and 12 months. Transcranial Doppler (TCD) and pulse oximetry (SpO2) measures were recorded longitudinally in SCA infants, and a subgroup of controls. Haemoglobin values were obtained from SCA infants. At each age, SCA infants obtained BINS scores indicative of greater risk of neurodevelopmental delay compared with controls. The number of moderate-high BINS risk scores increased significantly between 3 and 9 months. At 9 months BINS raw scores correlated negatively with TCD velocity and positively with haemoglobin. This exploratory study suggests that SCA infants may be at greater risk of neurodevelopmental delay than previously considered, and may provide the impetus for further research into the very early precursors of cognitive impairment.     

Enhanced platelet reactivity and hypercoagulability in the steady state of sickle cell anaemia.

A prospective controlled study was undertaken to investigate the haemostatic and coagulation status of 18 adult subjects in the steady state of sickle cell anaemia (SCA), using a relatively new in vitro technique. Shear induced haemostasis, whole blood dynamic coagulation, and spontaneous thrombolysis were measured using nonanticoagulated blood. As expected, the haemoglobin levels were significantly lower and platelet counts significantly higher in subjects with SCA compared with controls. Haemostasis and coagulation were significantly enhanced in SCA. No correlation was found between the raised platelet count and enhanced haemostasis or the reduced haemoglobin and hypercoagulation, respectively. Hyperactivity of the haemostatic system may have a pathogenic role in vaso-occlusive microthrombotic events and in the leg ulcers, both of which occur frequently in SCA.     

Effect of myeloablative bone marrow transplantation on growth in children with sickle cell anaemia: results of the multicenter study of haematopoietic cell transplantation for sickle cell anaemia

Although haematopoietic cell transplantation (HCT) is curative for sickle cell anaemia (SCA), concerns about its short- and long-term toxicities limit its application. A potential toxicity is an adverse effect on growth. To identify an HCT growth effect, serial height and weight measurements from 53 children and adolescents with SCA after receiving a transplant were compared to historical controls. Hierarchical Linear Models for longitudinal data were used for analysis. In general growth was not impaired by HCT for SCA in young children; however, diminished growth may occur if HCT is carried out near or during the adolescent growth spurt.     

High red blood cell nitric oxide synthase activation is not associated with improved vascular function and red blood cell deformability in sickle cell anaemia

Human red blood cells (RBC) express an active and functional endothelial‐like nitric oxide (NO) synthase (RBC‐NOS). We report studies on RBC‐NOS activity in sickle cell anaemia (SCA), a genetic disease characterized by decreased RBC deformability and vascular dysfunction. Total RBC‐NOS content was not significantly different in SCA patients compared to healthy controls; however, using phosphorylated RBC‐NOS‐Ser¹¹⁷⁷ as a marker, RBC‐NOS activation was higher in SCA patients as a consequence of the greater activation of Akt (phosphorylated Akt‐Ser⁴⁷³). The higher RBC‐NOS activation in SCA led to higher levels of S‐nitrosylated α‐ and β‐spectrins, and greater RBC nitrite and nitrotyrosine levels compared to healthy controls. Plasma nitrite content was not different between the two groups. Laser Doppler flowmetric experiments demonstrated blunted microcirculatory NO‐dependent response under hyperthermia in SCA patients. RBC deformability, measured by ektacytometry, was reduced in SCA in contrast to healthy individuals, and pre‐shearing RBC in vitro did not improve deformability despite an increase of RBC‐NOS activation. RBC‐NOS activation is high in freshly drawn blood from SCA patients, resulting in high amounts of NO produced by RBC. However, this does not result in improved RBC deformability and vascular function: higher RBC‐NO is not sufficient to counterbalance the enhanced oxidative stress in SCA.     

Mild haemorheological changes induced by a moderate endurance exercise in patients with sickle cell anaemia

The levels and duration of physical activity that can be considered as completely safe in patients with sickle cell anaemia (SCA) is unknown. The present study compared the haemorheological and haematological profile, cell density distribution and basic biochemistry between a group of 17 patients with SCA and 21 healthy subjects before and after a 20 min duration submaximal cycling exercise at the same absolute workload. Blood was sampled at rest and 3 min after the end of exercise for measurement of biological parameters. Exercise did not affect the haematocrit and blood viscosity in the two groups. Plasma viscosity was not different between the two groups at rest and similarly increased with exercise. The proportion of intermediary dense cells (with density between 1·11 and 1·12 g/ml) decreased with exercise in the SCA group resulting in an increase in the proportion of red blood cells with a density >1·12 g/ml. No change was observed in the control group. The present study suggests that mild-moderate exercise is not very harmful for SCA patients. The haemorheological and haematological changes were very mild, except for the formation of dense cells but no clinically significant signs of medical complication were present in any of the patients.     

Splenic regrowth in sickle cell anaemia following hypertransfusion

We describe five adult patients with sickle cell anaemia (SS) who developed clinical, radiological and histological evidence of splenic regrowth while receiving regular blood transfusions. Five patients, all homozygous SS, range 23–34 years, were commenced on hypertransfusion therapy. Three patients were transfused because of severe recurrent vaso-occlusive crises, one for chronic sickle lung and one in an attempt to prevent deterioration of renal function. The mean duration of hypertransfusion prior to documentation of splenic regrowth was 52 months (range 12–97 months). Two patients developed significant hypersplenism. One patient had clinically-apparent splenomegaly and four patients had splenomegaly documented on ultrasound. Splenic regrowth in hypertransfused adults with sickle cell anaemia is not infrequent and may have important clinical implications.     

Genetic determinants of haemolysis in sickle cell anaemia

Haemolytic anaemia is variable among patients with sickle cell anaemia and can be estimated by reticulocyte count, lactate dehydrogenase, aspartate aminotransferase and bilirubin levels. Using principal component analysis of these measurements we computed a haemolytic score that we used as a subphenotype in a genome‐wide association study. We identified in one cohort and replicated in two additional cohorts the association of a single nucleotide polymorphism in NPRL3 (rs7203560; chr16p13·3) (P = 6·04 × 10⁻⁰⁷). This association was validated by targeted genotyping in a fourth independent cohort. The HBA1/HBA2 regulatory elements, hypersensitive sites (HS)‐33, HS‐40 and HS‐48 are located in introns of NPRL3. Rs7203560 was in perfect linkage disequilibrium (LD) with rs9926112 (r² = 1) and in strong LD with rs7197554 (r² = 0·75) and rs13336641 (r² = 0·77); the latter is located between HS‐33 and HS‐40 sites and next to a CTCF binding site. The minor allele for rs7203560 was associated with the −∝^3·7thalassaemia gene deletion. When adjusting for HbF and ∝ thalassaemia, the association of NPRL3 with the haemolytic score was significant (P = 0·00375) and remained significant when examining only cases without gene deletion∝ thalassaemia (P = 0·02463). Perhaps by independently down‐regulating expression of the HBA1/HBA2 genes, variants of the HBA1/HBA2 gene regulatory loci, tagged by rs7203560, reduce haemolysis in sickle cell anaemia.     

Hypofibronectinaemia and severity of sickle cell anaemia in Nigeria

Plasma fibronectin levels in sickle cell anaemia and apparently healthy Nigerians were investigated to determine any correlation with disease severity. A cheaper in-house plasma fibronectin assay was also developed that could be adapted for use in Africa and elsewhere. Plasma fibronectin assay was concurrently carried out using the newly developed inhibition enzyme-linked immunosorbent assay (ELISA) and a commercial competitive binding ELISA. The in-house assay compared favourably with that of the commercial kit. The mean plasma fibronectin levels in sickle cell anaemia subjects were significantly lower than that of control subjects (P < 0.001). Plasma fibronectin concentration could therefore be useful in assessing the severity of sickle cell anaemia.     

Sickle cell β-thalassaemia compared with sickle cell anaemia in Algeria

Clinical, haematological and biochemical features in 42 subjects with S-beta thalassaemia (31 subjects with S-beta° thalassaemia and 11 subjects with S-beta⁺ thalassaemia); and in 42 with homozygous sickle cell disease were compared. Persistent splenomegaly was more common and painful crises less common in the S-beta thalassaemia group. Total Hb was higher and reticulocyte count lower in S-beta⁺ thalassaemia than in S-beta° thalassaemia or SS disease. Microcytosis was marked in the S-beta thalassaemia group while the MCV was normal in sickle cell anaemia. Hb F was significantly higher in the S-beta° thalassaemia group, without any influence on the severity of the disease. Many features suggest that sickle cell thalassaemia is more severe in Algeria than in Negro subjects and similar to the disease in Italian patients.     

Red cell deformability in oral contraceptive pill users with sickle cell anaemia

The use of the combined oral contraceptive pill (COCP) in women with sickle cell anaemia (SCA) is controversial, as contraceptive steroids are thought to adversely affect erythrocyte deformability. This observational study was performed to investigate whether hormonal contraception influenced erythrocyte deformability in women with SCA. 30 women with SCA using various contraceptive modalities: COCP (n = 10); progestogen only (PO) contraception (n = 10) and non-hormonal contraception (n = 10) were recruited. Erythrocyte deformability was assessed using the clogging rate (CR) and red cell transit time (RCTT). There was no statistical difference in the mean CR and RCTT between the three groups of women (one-way ANOVA). Current contraceptive steroids do not appear to impair red cell deformability in women with SCA.     

Defining stroke risk in children with sickle cell anaemia

Sickle cell anaemia (SCA) is the most common cause of childhood stroke, occurring with the highest frequency before the age of 6 years. Despite the relative frequency of stroke in SCA, few predictors of risk exist. Anaemia, leucocytosis, hypertension, silent infarction, and history of acute chest syndrome are well-documented risk factors for ischaemic stroke in SCA. Recent data suggest that other environmental and genetic factors, many unrelated to SCA, influence the development of cerebrovascular disease. Non-invasive assessment of individual stroke risk using transcranial Doppler ultrasonography has provided a means of selecting and prophylactically treating SCA children at highest risk. With the ultimate goal of preventing stroke, the information gained from the studies reviewed here may lead to improved prediction of stroke so that clinical trials to assess risk-based therapy may be carried out on selected children with SCA.     

Plasma and erythrocyte lipids in sickle cell anaemia

Summary. The content and composition of plasma and erythrocyte lipids from individuals having sickle cell anaemia has been determined. The plasma contains a significantly reduced content of both cholesterol and phospholipid while the ratio of cholesteryl ester to total cholesterol, the distribution of phospholipids classes, triglyceride concentration and the fatty acid content were similar to normal values. However, the free glycerol content of the plasma was eight-fold higher than normal. Erythrocyte lipids contain an elevated level of cholesterol and control levels of phospholipid content, phospholipid distribution and fatty acid content. The plasma was separated by ultracentrifugation into VLDL (density <1.006), LDL (1.006< d <1.063) and HDL (1.063< d< 1.21). Significant decreases in cholesterol and phospholipid were observed in LDL and HDL.     

Subcortical and cerebellar volumetric deficits in paediatric sickle cell anaemia

Sickle cell anaemia (SCA) is associated with silent cerebral infarction (SCI), affecting white and cortical grey matter, but there are few data on subcortical volumes. We analysed retrospective magnetic resonance imaging (MRI) data in 26 SCA patients and 20 controls, comparing mean subcortical volumes between three groups: controls, SCA with SCI (n = 13) and SCA without visible abnormality (n = 13). Specific volumetric differences were found in the hippocampus, amygdala, pallidum, caudate, putamen, thalamus, and cerebellum. This is the first study to demonstrate subcortical volume change in SCA, with the most severe volumetric deficits occurring in children with SCI seen on MRI.