Effects of hydroxyurea treatment on cerebral oxygenation in adult patients with sickle cell disease: an open-label pilot study

Endurance training and hydroxyurea have synergistic effects on muscle function and energetics in sickle cell disease mice

Sickle cell disease (SCD) is an hemoglobinopathy resulting in the production of an abnormal Hb (HbS) which can polymerize in deoxygenated conditions, leading to the sickling of red blood cells (RBC). These alterations can decrease the oxygen-carrying capacity leading to impaired function and energetics of skeletal muscle. Any strategy which could reverse the corresponding defects could be of interest. In SCD, endurance training is known to improve multiples muscle properties which restores patient's exercise capacity but present reduced effects in anemic patients. Hydroxyurea (HU) can increase fetal hemoglobin production which can reduce anemia in patients. The present study was conducted to determine whether HU can improve the effects of endurance training to improve muscle function and energetics. Twenty SCD Townes mice have been trained for 8 weeks with (n = 11) or without (n = 9) HU. SCD mice muscle function and energetics were analyzed during a standardized rest-exercise-recovery protocol, using Phosphorus-31 Magnetic resonance spectroscopy (31P-MRS) and transcutaneous stimulation. The combination of training and HU specifically decreased fatigue index and PCr consumption while muscle oxidative capacity was improved. These results illustrate the potential synergistic effects of endurance training and HU on muscle function and energetics in sickle cell disease.

Role of hydroxyurea therapy in the prevention of organ damage in sickle cell disease: a systematic review and meta-analysis

BACKGROUND

Hydroxyurea is an affordable drug that reduces vaso-occlusive crises and transfusion requirements in sickle cell disease. However, its effectiveness in preventing chronic organ damage is still unclear. This systematic review and meta-analysis aimed to evaluate the role of hydroxyurea in preventing organ morbidity.

METHOD

We included original articles published in English from 1st January 1990 to 31st January 2023, reporting hydroxyurea therapy and organ damage from PubMed, Google Scholar, Scopus, and CrossRef databases. A total of 45 studies with 4681 sickle cell disease patients were evaluated for organ damage.

RESULTS

Our analysis showed that hydroxyurea intervention significantly lowered transcranial Doppler and tricuspid regurgitant velocity, with a standardized mean difference of - 1.03 (- 1.49; - 0.58); I 2 = 96% and - 1.37 (CI - 2.31, - 0.42); I 2 = 94%, respectively. Moreover, the pooled estimate for albuminuria showed a beneficial effect post-hydroxyurea therapy by reducing the risk of albuminuria by 58% (risk ratio of 0.42 (0.28; 0.63); I 2 = 28%).

CONCLUSION

Our study found that a hydroxyurea dose above 20 mg/kg/day with a mean rise in HbF by 18.46% post-hydroxyurea therapy had a beneficial role in reducing transcranial doppler velocity, tricuspid regurgitant velocity, albuminuria, and splenic abnormality.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023401187.

Infrared Spectroscopy: A New Frontier in Hematological Disease Diagnosis

Hematological diseases, due to their complex nature and diverse manifestations, pose significant diagnostic challenges in healthcare. The pressing need for early and accurate diagnosis has driven the exploration of novel diagnostic techniques. Infrared (IR) spectroscopy, renowned for its noninvasive, rapid, and cost-effective characteristics, has emerged as a promising adjunct in hematological diagnostics. This review delves into the transformative role of IR spectroscopy and highlights its applications in detecting and diagnosing various blood-related ailments. We discuss groundbreaking research findings and real-world applications while providing a balanced view of the potential and limitations of the technique. By integrating advanced technology with clinical needs, we offer insights into how IR spectroscopy may herald a new era of hematological disease diagnosis.

Cerebral and muscle microvascular oxygenation in children with sickle cell disease: Influence of hematology, hemorheology and vasomotion

The present study investigated cerebral and muscle hemoglobin oxygen saturation (tissue oxygen index, TOI) in children with sickle cell anemia (SS), sickle cell hemoglobin C disease (SC) and healthy children (AA). TOI was measured by near-infrared spectroscopy (NIRS) and spectral analysis of the TOI variability was used to assess flowmotion and vasomotion. Arterial oxyhemoglobin saturation (SpO₂), hemorheological and hematological parameters were also measured in SS and SC children. Both TOI were lower in SS compared to both AA and SC children, with SC exhibiting lower values than AA children. Cerebral vasomotion expressed in absolute values was enhanced in SS compared to AA and SC children. Muscle vasomotion did not differ between the three groups. Hematocrit, SpO₂ and red blood cell deformability were positively associated with cerebral TOI in SS children. We demonstrated that 1) cerebral and muscle TOI were markedly decreased in SS children while the decrease of TOI was milder in SC children, 2) cerebral TOI level was associated with several biological markers in SS children only and 3) cerebral vasomotion was enhanced in SS, possibly to counterbalance the effects of chronic cerebral hypoxia.

Bayesian analyses demonstrate tissue blood volume is not decreased during acute sickle cell pain episodes: A preliminary study

BACKGROUND

Pain is the most common complication of Sickle Cell Disease (SCD). Tissue oximetry properties in SCD during steady state and acute pain are not well described.

METHODS

This was a cross sectional study of tissue oximetry properties in individuals with SCD during steady state, acute pain and healthy controls without SCD. A novel tissue oximetry device was used to better account for tissue pigmentation interference. We hypothesized that during acute SCD pain, blood volume to painful areas would be at least 10% less than steady state. Bayesian analyses of the data (with flat piors) were planned a priori because of the small projected sample size.

RESULTS

The sample included 14 individuals (4 during crisis, 5 steady state, and 5 controls). In individuals with SCD, blood volume to the lower back was higher during crisis (0.18% of tissue volume vs. 0.14% ). Bayesian analyses yielded a 3% probability that our hypothesis (that blood volume would decrease by 10% ) was correct.

CONCLUSIONS

During acute SCD pain, blood volume to painful areas is not decreased. Bayesian analyses were useful for interpretation of small sample data and may have utility in early phase trials for rare diseases.

Normal muscle oxygen consumption and fatigability in sickle cell patients despite reduced microvascular oxygenation and hemorheological abnormalities

Background/Aim

Although it has been hypothesized that muscle metabolism and fatigability could be impaired in sickle cell patients, no study has addressed this issue.

Methods

We compared muscle metabolism and function (muscle microvascular oxygenation, microvascular blood flow, muscle oxygen consumption and muscle microvascular oxygenation variability, which reflects vasomotion activity, maximal muscle force and local muscle fatigability) and the hemorheological profile at rest between 16 healthy subjects (AA), 20 sickle cell-hemoglobin C disease (SC) patients and 16 sickle cell anemia (SS) patients.

Results

Muscle microvascular oxygenation was reduced in SS patients compared to the SC and AA groups and this reduction was not related to hemorhelogical abnormalities. No difference was observed between the three groups for oxygen consumption and vasomotion activity. Muscle microvascular blood flow was higher in SS patients compared to the AA group, and tended to be higher compared to the SC group. Multivariate analysis revealed that muscle oxygen consumption was independently associated with muscle microvascular blood flow in the two sickle cell groups (SC and SS). Finally, despite reduced muscle force in sickle cell patients, their local muscle fatigability was similar to that of the healthy subjects.

Conclusions

Sickle cell patients have normal resting muscle oxygen consumption and fatigability despite hemorheological alterations and, for SS patients only, reduced muscle microvascular oxygenation and increased microvascular blood flow. Two alternative mechanisms can be proposed for SS patients: 1) the increased muscle microvascular blood flow is a way to compensate for the lower muscle microvascular oxygenation to maintain muscle oxygen consumption to normal values or 2) the reduced microvascular oxygenation coupled with a normal resting muscle oxygen consumption could indicate that there is slight hypoxia within the muscle which is not sufficient to limit mitochondrial respiration but increases muscle microvascular blood flow.

Hemorheological alterations, decreased cerebral microvascular oxygenation and cerebral vasomotion compensation in sickle cell patients

Sickle cell anemia (SS) is characterized by a reduced cerebral microvascular oxygen saturation (cerebral TOI), which is not associated with hemoglobin concentration. Cerebral TOI has never been studied in sickle cell-hemoglobin C disease (SC). We focused on the relationships between hemorheological alterations and cerebral TOI in sickle cell patients with no cerebral vasculopathy and on the usefulness of TOI variability to assess the cerebral vasomotion activity. The blood rheological profile, the level of cerebral TOI (spatial resolved spectroscopy) and the cerebral TOI variability, which reflects vasomotion activity, were compared between 20 healthy subjects (AA), 21 SC patients, and 21 SS patients. Cerebral TOI exhibited the following order: AA > SC > SS. The low cerebral TOI in SS patients was related to red blood cell aggregation and deformability properties. The cerebral TOI variability of SS and SC patients was increased above healthy values and vasomotion activity was negatively associated with the reduced cerebral TOI in SS patients. We demonstrated that (1) blood rheology could be involved in the reduced cerebral TOI in SS patients but not in SC patients; (2) vasomotion activity is increased in SS and SC patients to compensate for the reduced cerebral TOI.

Cerebral tissue hemoglobin saturation in children with sickle cell disease

BACKGROUND

Desaturation of hemoglobin (Hb) in cerebral tissue, a physiologic marker of brain vulnerable to ischemic injury, can be detected non-invasively by transcranial oximetry. Absolute cerebral oximetry has not been studied in sickle cell disease (SCD), a group at very high risk of cerebral infarction in whom prevention of brain injury is key.

PROCEDURE

We measured absolute Hb saturation in cerebral tissue (S(CT)O(2)) in children with SCD using near-infrared spectrophotometry and investigated the contributions of peripheral Hb saturation (S(P)O(2)), hematologic measures, cerebral arterial blood flow velocity, and cerebral arterial stenosis to S(CT)O(2). We also assessed the effects of transfusion.

RESULTS

We studied 149 children with SCD (112 HbSS/Sβ(0); 37 HbSC/Sβ(+)). S(CT)O(2) was abnormally low in 75% of HbSS/Sβ(0) and 35% of HbSC/Sβ(+) patients. S(CT)O(2) (mean ± SD) was 53.2 ± 14.2 in HbSS/Sβ(0) and 66.1 ± 9.2% in SC/Sβ(+) patients. S(CT)O(2) correlated with age, sex, Hb concentration, reticulocytes, Hb F, and S(P)O(2), but not transcranial Doppler arterial blood flow velocities as continuous measures. In multivariable models, S(P)O(2), Hb concentration, and age were significant independent determinants of S(CT)O(2). Cerebral vasculopathy was associated with ipsilateral cerebral desaturation. Transfusion increased S(CT)O(2) and minimized the inter-hemispheric differences in S(CT)O(2) due to vasculopathy.

CONCLUSIONS

Cerebral desaturation, a physiologic marker of at-risk brain, is common in SCD, more severe in HbSS/Sβ(0) patients, and associated with peripheral desaturation, more severe anemia, and increasing age. Cerebral oximetry has the potential to improve the identification of children with SCD at highest risk of neurologic injury and possibly serve as a physiologic guide for neuroprotective therapy.

Sickle cell disease and stroke

Twenty-four percent of sickle cell disease (SCD) patients have a stroke by the age of 45 years. Blood transfusions decrease stroke risk in patients deemed high risk by transcranial Doppler. However, transcranial Doppler has poor specificity, and transfusions are limited by alloimmunization and iron overload. Transfusion withdrawal may be associated with an increased rebound stroke risk. Extended blood typing decreases alloimmunization in SCD but is not universally adopted. Transfusions for thalassemia begun in early childhood are associated with lower rates of alloimmunization than are seen in SCD, suggesting immune tolerance. Optimal oxygen transport efficiency occurs at a relatively low hematocrit for SCD patients because of hyperviscosity. Consequently, exchange rather than simple transfusions are more effective in improving oxygen transport efficiency, but the former are technically more demanding and require more blood units. Although viscosity is of importance in the noncerebral manifestations of SCD, inflammation may play a larger role than viscosity in the development of large-vessel stroke. The future of SCD stroke management lies in the avoidance of transfusion. Hydroxyurea and anti-inflammatory measures may reduce the need for transfusion. Recent genome-wide association studies may provide methods for modulating fetal hemoglobin production enough to attenuate stroke risk and other complications of SCD.

Near-infrared spectra absorbance of blood from sickle cell patients and normal individuals

Limited data are available regarding the physicochemical dynamics of tissue hypoxia in sickle cell disease. Studies using near-infrared spectroscopy (NIRS) have reported that patients with sickle cell disease (SCD) have lower cerebral oxygen saturation values (rSO2) than normal individuals. The reason SCD patients have subnormal rSO2 values is not known. It may be related to the degree of anaemia, sickle haemoglobin, disease complications and the possibility of SCD different NIRS absorbance spectra than normal. This study compared NIRS absorbance spectra of blood with adult haemoglobin AA, sickle haemoglobin SS, and AS. Venous blood was collected from SCD (SS and AS) and non-SCD patients (AA). Whole blood, cell free haemoglobin samples were scanned through the wavelength range of 600-1000 nm. The results showed no different NIRS spectra absorbance between the haemoglobin's AA, SS. It thus appears that lower brain oxygen saturation in sickle cell anaemia patients is related to impaired oxygen carrying capacity or delivery by sickle haemoglobin.

Effect of transfusion on cerebral oxygenation, flow velocity in a patient with sickle cell anemia and Moyamoya disease: a case report

Vascular occlusive diseases affect brain blood flow, brain metabolism and are associated with arterial ischemic stroke. This study was designed to measure the brain blood flow velocity, brain oxygenation, hemoglobin concentrations, hematocrit, and cell free hemoglobin at pre- and post-exchange red cell transfusion in an 18 year old male patient with sickle cell disease and moyamoya syndrome (MMS). Exchange transfusion increased cerebral oxygen saturation 12%, total hemoglobin concentration 2%, hemoglobin AA 80%, and reduced sickle (SS) hemoglobin 12%, arterializations 33%, and cell free hemoglobin 33%. Brain blood flow velocity values were unaffected by transfusion. These observations suggest that exchange transfusion increases the hemoglobin carrying capacity and reduces sickle hemoglobin and shunting of blood, which may improve the peripheral and cerebral oxygenation. Transfusion did not affect the brain blood flow in this patient. Therefore the risk of transient ischemic attack and arterial ischemic stroke from mms still exist.

The association of oral hydroxyurea therapy with improved cognitive functioning in sickle cell disease

This study examined potential cognitive benefits of oral hydroxyurea therapy for children with sickle cell disease (SCD). Cognitive abilities of 15 children with SCD on hydroxyurea were compared to 50 other children with SCD, controlling for demographics and hematocrit. Children on hydroxyurea scored significantly higher on tests of verbal comprehension, fluid reasoning, and general cognitive ability than children not on the drug. The data therefore provide preliminary evidence of cognitive benefits of hydroxyurea. Mechanisms for this effect may be improved blood/oxygen supply to the brain or reduced fatigue and illness.

The pathophysiology, prevention, and treatment of stroke in sickle cell disease

PURPOSE OF REVIEW

Stroke is one of the most devastating complications of sickle cell disease, but current research has led to improved understanding of its pathogenesis and to new approaches in the prevention of both primary and secondary stroke. This review focuses on advances reported in the past 2 years.

RECENT FINDINGS

New concepts in the pathophysiology of central nervous system events in sickle cell disease have centered around hemolytic anemia and nitric oxide metabolism. Genetic risk factors are now being explored. Major improvement in primary stroke prevention has occurred through transcranial Doppler ultrasonography screening, but utilization of this technique is far from optimal. Hydroxyurea is now being tested as an alternative approach to chronic transfusion for secondary stroke prevention through a multicenter trial. Other studies are addressing the management of silent infarcts and nocturnal hypoxemia.

SUMMARY

Increased understanding of the etiology and pathogenesis of stroke in sickle cell disease should eventually lead to improved management of all central nervous system complications. Alternative secondary stroke prevention with hydroxyurea may allow patients to avoid dependence on life-long chronic transfusion. Primary stroke prevention through transcranial Doppler ultrasonography screening may ultimately yield a dramatic reduction in the incidence of stroke in sickle cell disease.

Effects of hydroxyurea on malaria, parasite growth and adhesion in experimental models

We recently raised concern over using hydroxyurea (HU) in the treatment of sickle cell disease in areas endemic for malaria, becauseit up-regulates the endothelial surface expression of ICAM-1, a major receptor for Plasmodium falciparum-infected erythrocytes in the brain. Using human in vitro models of cerebral malaria, we evaluated the interaction of HU with parasites and demonstrated that HU pretreatment increased the number of infected red blood cells adhering to the endothelium, but did not increase endothelial apoptosis. Moreover, using an experimental cerebral malaria model, HU pretreatment was found to prevent significantly mice from developing neurological syndrome by inhibiting parasite growth, opening potential therapeutic avenues.

Evaluation of reticulated platelets in patients with sickle cell diseases

BACKGROUND AND PURPOSE

Reticulated platelet (RP) count provides an estimate of thrombopoiesis. The objective was to evaluate RP in patients in different stages of sickle cell disease (SCD) and to determine the relationship between interleukin-6 (IL-6), interleukin-3 (IL-3) and thrombopoietin (TPO) and RP count and degree of activation.

METHODS

Eighty-nine adult patients with SCD were studied: 38 were in the steady state, 27 in hemolytic crisis (HC) and 24 in vaso-occlusive crisis (VOC). RPs and activated platelets were analyzed by flow cytometry. Soluble P-selectin, IL-6, IL-3 and thrombopoietin (TPO) levels were measured by ELISA tests.

RESULTS

The patients in VOC had a higher absolute number of RPs and CD62P+ platelets than did the control group or patients in the steady state. A significant correlation was observed between the absolute number of CD62P+ platelets and RPs in patients in the steady state, HC and VOC. In the steady-state group of patients, the level of soluble P-selectin was found to be dependent on the RP values. IL-3 and TPO serum levels were higher in patients in the steady state, HC and VOC than in the control group. IL-6 serum levels were higher in HC and VOC patients than in the control group and higher in patients in the steady state than in the VOC group.

CONCLUSION

Our results suggest that PRs contribute to the vaso-occlusive process in sickle cell disease. Increased interleukin serum levels probably indicate that inflammatory process is involved in the vascular-occlusive phenomenon. However, it appears that these inflammatory mediators do not have an effect on thrombopoiesis in sickle-cell-disease patients.