Pathophysiology of Sickle Cell Disease

Hemolysis dictates monocyte differentiation via two distinct pathways in sickle cell disease vaso-occlusion

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by painful vaso-occlusive crises (VOC) and chronic hemolysis. The mononuclear phagocyte system is pivotal to SCD pathophysiology, but the mechanisms governing monocyte/macrophage differentiation remain unknown. This study examined the influence of hemolysis on circulating monocyte trajectories in SCD. We discovered that hemolysis stimulated CSF-1 production, partly by endothelial cells via Nrf2, promoting classical monocyte (CMo) differentiation into blood patrolling monocytes (PMo) in SCD mice. However, hemolysis also upregulated CCL-2 through IFN-I, inducing CMo transmigration and differentiation into tissue monocyte-derived macrophages. Blocking CMo transmigration by anti-P selectin antibody in SCD mice increased circulating PMo, corroborating that CMo-to-tissue macrophage differentiation occurs at the expense of CMo-to-blood PMo differentiation. We observed a positive correlation between plasma CSF-1/CCL-2 ratios and blood PMo levels in patients with SCD, underscoring the clinical significance of these two opposing factors in monocyte differentiation. Combined treatment with CSF-1 and anti-P selectin antibody more effectively increased PMo numbers and reduced stasis compared with single-agent therapies in SCD mice. Altogether, these data indicate that monocyte fates are regulated by the balance between two heme pathways, Nrf2/CSF-1 and IFN-I/CCL-2, and suggest that the CSF-1/CCL-2 ratio may present a diagnostic and therapeutic target in SCD.

Proinflammatory state promotes red blood cell alloimmunization in pediatric patients with sickle cell disease

We examined risk factors for red blood cell (RBC) alloimmunization in pediatric patients with sickle cell disease, focusing on the recipients' inflammatory state at the time of transfusion and anti-inflammatory role of hydroxyurea (HU). Among 471 participants, 55 (11.70%) participants were alloimmunized and formed 59 alloantibodies and 17 autoantibodies with an alloimmunization rate of 0.36 alloantibodies per 100 units. Analysis of 27 participants in whom alloantibodies were formed with specificities showed 23.8% (30/126) of units transfused during a proinflammatory event resulting in alloantibody formation compared with 2.8% (27/952) of units transfused at steady state. Therefore, transfusion during proinflammatory events increased the risk for alloimmunization (odds ratio [OR], 4.22; 95% confidence interval [CI], 1.64-10.85; P = .003). Further analysis of all the 471 participants showed that alloimmunization of patients who received episodic transfusion, mostly during proinflammatory events, was not reduced with HU therapy (OR, 6.52; 95% CI, 0.85-49.77; P = .071), HU therapy duration (OR, 1.13; 95% CI, 0.997-1.28; P = .056), or HU dose (OR, 1.06; 95% CI, 0.96-1.16; P = .242). The analysis also identified high transfusion burden (OR, 1.02; 95% CI, 1.003-1.04; P = .020) and hemoglobin S (HbSS) and HbSβ0-thalassemia genotypes (OR, 11.22, 95% CI, 1.51-83.38; P = .018) as additional risk factors for alloimmunization. In conclusion, the inflammatory state of transfusion recipients affects the risk of RBC alloimmunization, which is not modified by HU therapy. Judicious use of transfusion during proinflammatory events is critical for preventing alloimmunization.

Neuroprotective Effects of Phenolic Antioxidant Tert-butylhydroquinone (tBHQ) in Brain Diseases

Human life and health are gravely threatened by brain diseases. The onset and progression of the illnesses are influenced by a variety of factors, including pathogenic causes, environmental factors, mental issues, etc. According to scientific studies, neuroinflammation and oxidative stress play a significant role in the development and incidence of brain diseases by producing pro-inflammatory cytokines and oxidative tissue damage to induce inflammation and apoptosis. Neuroinflammation, oxidative stress, and oxidative stress-related changes are inseparable factors in the etiology of several brain diseases. Numerous neurodegenerative diseases have undergone substantial research into the therapeutic alternatives that target oxidative stress, the function of oxidative stress, and the possible therapeutic use of antioxidants. Formerly, tBHQ is a synthetic phenolic antioxidant, which has been widely used as a food additive. According to recent researches, tBHQ can suppress the processes that lead to neuroinflammation and oxidative stress, which offers a fresh approach to treating brain diseases. In order to achieve the goal of decreasing inflammation and apoptosis, tBHQ is a specialized nuclear factor erythroid 2-related factor (Nrf2) activator that decreases oxidative stress and enhances antioxidant status by upregulating the Nrf2 gene and reducing nuclear factor kappa-B (NF-κB) activity. This article reviews the effects of tBHQ on neuroinflammation and oxidative stress in recent years and looks into how tBHQ inhibits neuroinflammation and oxidative stress through human, animal, and cell experiments to play a neuroprotective role in Alzheimer's disease (AD), stroke, depression, and Parkinson's disease (PD). It is anticipated that this article will be useful as a reference for upcoming research and the creation of drugs to treat brain diseases.

Severity and burden of sickle cell disease in France: a nationwide real-world study

The burden of sickle cell disease (SCD) in France has been difficult to apprehend due to the paucity of reliable nationwide epidemiological data. We aimed to describe the epidemiology of SCD and evaluate its burden and costs. Patients with SCD and most severely affected patients were identified between 2012 and 2018 from the French National Health Data System database (SNDS, Système national des données de santé). Outcomes of interest included rates of acute and chronic complications, healthcare resource utilization and associated costs, and were compared in subpopulations of patients before and after hematopoietic stem cell transplantation, initiating hydroxyurea or a chronic transfusion program. Between 2012 and 2018, 22,619 patients with SCD were identified, among which 4,270 patients were defined as most severely affected. Rates of vaso-occlusion episodes and acute chest syndrome were 86.29 (95% confidence interval [CI]: 85.75-86.83] and 12.90 (95% CI: 12.69-13.11) per 100 person years in the study population and 166.9 (95% CI: 165.4- 168.4) and 22.71 (95% CI: 22.16-23.27) per 100 person years in most severely affected patients. Median (Q1-Q3) annualized total costs were €5,073.63 (range, €1,633.74-14,000.94) and €13,295.67 (range, €5,754.67-26,385.23) in the study population and most severely affected patients. Median annualized costs were ten times lower after treatment intensification for hematopoietic stem cell transplantation (€29,011.75 vs. €2,465.98; P<0.001), they slightly decreased after hydroxyurea initiation (€13,057.79 vs. €12,752.44; P=0.003) and were five times higher after chronic transfusion program initiation (€4,643.11 vs. €22,715.85; P<0.001). SCD still places a significant demand on health resources, even after therapeutic intensification.

Long-Term L-Glutamine Treatment Reduces Hemolysis without Ameliorating Hepatic Vaso-Occlusion and Liver Fibrosis in a Mouse Model of Sickle Cell Disease

Sickle cell disease (SCD) is an autosomal recessive monogenic disorder caused by a homozygous mutation in the β-globin gene, which leads to erythrocyte sickling, hemolysis, vaso-occlusion, and sterile inflammation. The administration of oral L-glutamine has been shown to reduce the frequency of pain in SCD patients; however, the long-term effect of L-glutamine in SCD remains to be determined. To understand the long-term effect of L-glutamine administration in the liver we used quantitative liver intravital microscopy and biochemical analysis in humanized SCD mice. We here show that chronic L-glutamine administration reduces hepatic hemoglobin-heme-iron levels but fails to ameliorate ischemic liver injury. Remarkably, we found that this failure in the resolution of hepatobiliary injury and persistent liver fibrosis is associated with the reduced expression of hepatic Kupffer cells post-L-glutamine treatment. These findings establish the importance of investigating the long-term effects of L-glutamine therapy on liver pathophysiology in SCD patients.

Determinants of ventricular arrhythmias in sickle cell anemia: toward better prevention of sudden cardiac death

Sudden death is 1 of the leading causes of death in adults with sickle cell anemia (SCA) but its etiology remains mostly unknown. Ventricular arrhythmia (VA) carries an increased risk of sudden death; however, its prevalence and determinants in SCA are poorly studied. This study aimed to identify the prevalence and predictors of VA in patients with SCA. From 2019 to 2022, 100 patients with SCA were referred to the physiology department to specifically analyze cardiac function and prospectively included in the DREPACOEUR registry. They underwent a 24-hour electrocardiogram monitoring (24h-Holter), transthoracic echocardiography, and laboratory tests on the same day. The primary end point was the occurrence of VA, defined as sustained or nonsustained ventricular tachycardia (VT), >500 premature ventricular contractions (PVCs) on 24h-Holter, or a recent history of VT ablation. The mean patient age was 46 ± 13 years, and 48% of the patients were male. Overall, VA was observed in 22 (22%) patients. Male sex (81% vs 34%; P = .02), impaired global longitudinal strain (GLS): -16% ± 1.9% vs -18.3% ± 2.7%; P = .02), and decreased platelet count (226 ± 96 giga per liter [G/L] vs 316 ± 130 G/L) were independently associated with VA. GLS correlated with PVC load every 24 hours (r = 0.39; P < .001) and a cutoff of -17.5% could predict VA with a sensitivity of 82% and a specificity of 63%. VAs are common in patients with SCA, especially in men. This pilot study uncovered GLS as a valuable parameter for improving rhythmic risk stratification.

Economic and Clinical Burden of Managing Sickle Cell Disease with Recurrent Vaso-Occlusive Crises in the United States

INTRODUCTION

The aim of this study was to describe the clinical complications, treatment use, healthcare resource utilization (HCRU), and costs among patients with sickle cell disease (SCD) with recurrent vaso-occlusive crises (VOCs) in the US.

METHODS

Merative MarketScan Databases were used to identify patients with SCD with recurrent VOCs from March 1, 2010, to March 1, 2019. Inclusion criteria were ≥ 1 inpatient or  ≥ 2 outpatient claims for SCD and ≥ 2 VOCs per year in any 2 consecutive years after the first qualifying SCD diagnosis. Individuals without SCD in these databases were used as matched controls. Patients were followed for ≥ 12 months, from their second VOC in the 2nd year (index date) to the earliest of inpatient death, end of continuous enrollment in medical/pharmacy benefits, or March 1, 2020. Outcomes were assessed during follow-up.

RESULTS

In total, 3420 patients with SCD with recurrent VOCs and 16,722 matched controls were identified. Patients with SCD with recurrent VOCs had a mean of 5.0 VOCs (standard deviation [SD] = 6.0), 2.7 inpatient admissions (SD 2.9), and 5.0 emergency department visits (SD 8.0) per patient per year during follow-up. Compared to matched controls, patients with SCD with recurrent VOCs incurred higher annual ($67,282 vs. $4134) and lifetime ($3.8 million vs. $229,000 over 50 years) healthcare costs.

CONCLUSION

Patients with SCD with recurrent VOCs experience substantial clinical and economic burden driven by inpatient costs and frequent VOCs. There is a major unmet need for treatments that alleviate or eliminate clinical complications, including VOCs, and reduce healthcare costs in this patient population.

Levels of inflammatory markers are differentially expressed in sickle cell anemia and sickle cell trait

Although sickle cell anemia (SCA) is related to inflammation, the profile of inflammatory markers in sickle cell trait (SCT) is poorly studied. This is a cross-sectional study of inflammatory biomarkers carried out involving adults with SCA in steady state, SCT and controls. The SCA group had higher levels of lactato dehydrogenase, IL-1β, IL-6, IL-10, and tumor necrosis factor alpha than the others, while the SCT group had similar levels to control group. In addition, SCA group had lower IL-8/IL-10 and soluble triggering receptor expressed on myeloid cells-1/IL-10 ratios. These findings indicate that individuals with SCT do not have a chronic inflammatory profile and reinforce that cytokines are involved in the maintenance of the inflammatory state in SCA.

Nrf2 sensitizes ferroptosis through l-2-hydroxyglutarate-mediated chromatin modifications in sickle cell disease

Sickle cell disease (SCD) is a chronic hemolytic and systemic hypoxia condition with constant oxidative stress and significant metabolic alterations. However, little is known about the correlation between metabolic alterations and the pathophysiological symptoms. Here, we report that Nrf2, a master regulator of cellular antioxidant responses, regulates the production of the metabolite l-2-hydroxyglutarate (L2HG) to mediate epigenetic histone hypermethylation for gene expression involved in metabolic, oxidative, and ferroptotic stress responses in SCD. Mechanistically, Nrf2 was found to regulate the expression of L2HG dehydrogenase (L2hgdh) to mediate L2HG production under hypoxia. Gene expression profile analysis indicated that reactive oxygen species (ROS) and ferroptosis responses were the most significantly affected signaling pathways after Nrf2 ablation in SCD. Nrf2 silencing and L2HG supplementation sensitize human sickle erythroid cells to ROS and ferroptosis stress. The absence of Nrf2 and accumulation of L2HG significantly affect histone methylation for chromatin structure modification and reduce the assembly of transcription complexes on downstream target genes to regulate ROS and ferroptosis responses. Furthermore, pharmacological activation of Nrf2 was found to have protective effects against ROS and ferroptosis stress in SCD mice. Our data suggest a novel mechanism by which Nrf2 regulates L2HG levels to mediate SCD severity through ROS and ferroptosis stress responses, suggesting that targeting Nrf2 is a viable therapeutic strategy for ameliorating SCD symptoms.

Biphosphoglycerate Mutase: A Novel Therapeutic Target for Malaria?

Biphosphoglycerate mutase (BPGM) is a tri-functional enzyme expressed exclusively in erythroid cells and tissues that is responsible for the production of 2,3-biphosphoglycerate (2,3-BPG) through the Rapoport-Luebering shunt. The 2,3-BPG is required for efficient glycolysis and ATP production under anaerobic conditions, but is also a critical allosteric regulator of hemoglobin (Hb), acting to regulate oxygen release in peripheral tissues. In humans, BPGM deficiency is very rare, and is associated with reduced levels of erythrocytic 2,3-BPG and ATP, left shifted Hb-O2 dissociation curve, low P50, elevated Hb and constitutive erythrocytosis. BPGM deficiency in mice recapitulates the erythroid defects seen in human patients. A recent report has shown that BPGM deficiency in mice affords striking protection against both severe malaria anemia and cerebral malaria. These findings are reminiscent of studies of another erythrocyte specific glycolytic enzyme, Pyruvate Kinase (PKLR), which mutational inactivation protects humans and mice against malaria through impairment of glycolysis and ATP production in erythrocytes. BPGM, and PKLR join glucose-6-phosphate dehydrogenase (G6PD) and other erythrocyte variants as modulating response to malaria. Recent studies reviewed suggest glycolysis in general, and BPGM in particular, as a novel pharmacological target for therapeutic intervention in malaria.

Correlation of Transfusion Dependence and Its Associated Sequelae to Hematological and Biochemical Parameters in Patients With Sickle Cell Disease and Beta Thalassemia Major in Khobar: A Retrospective Study

Sickle cell disease (SCD) and beta thalassemia major (βTM) are multisystemic, genetically inherited diseases. They are caused by mutations of hemoglobin, which ultimately cause abnormal functioning of the red blood cells. The morbidity and mortality rates of these diseases are significant, as they may result in severe complications, some of which are quite fatal; hence, early diagnosis and treatment are crucial. The purpose of this study is to collect patients' data in terms of their manifestations and overall clinical picture and correlate them to the laboratory parameters with emphasis on their transfusion dependence and its sequelae in King Fahd Hospital of the University (KFHU), Al-Khobar, Saudi Arabia. After obtaining ethical approval from the institutional review board and in collaboration with the blood bank, patients' data were retrospectively collected from the hospital's database and categorized into two disease groups. Accordingly, data related to the biological and demographic information, clinical picture pattern, laboratory investigations, and therapeutic measures, with emphasis on blood transfusion as a treatment option, were gathered and analyzed. Eventually, the aforementioned data aspects were assessed for the probability of correlations, which were proven to be present to some level as an answer to our cohort study's question. Such findings, which will be depicted later in this study, might represent a ground for having a more comprehensive and extensive approach in terms of the general evaluation of patients with SCD and βTM based on the established level of correlation. During the course of conducting our research, we encountered some limitations, including the sample size and scarce data available during the process of data collection.

Editing the core region in HPFH deletions alters fetal and adult globin expression for treatment of β-hemoglobinopathies

Reactivation of fetal hemoglobin (HbF) is a commonly adapted strategy to ameliorate β-hemoglobinopathies. However, the continued production of defective adult hemoglobin (HbA) limits HbF tetramer production affecting the therapeutic benefits. Here, we evaluated deletional hereditary persistence of fetal hemoglobin (HPFH) mutations and identified an 11-kb sequence, encompassing putative repressor region (PRR) to β-globin exon-1 (βE1), as the core deletion that ablates HbA and exhibits superior HbF production compared with HPFH or other well-established targets. PRR-βE1-edited hematopoietic stem and progenitor cells (HSPCs) retained their genome integrity and their engraftment potential to repopulate for long-term hematopoiesis in immunocompromised mice producing HbF positive cells in vivo. Furthermore, PRR-βE1 gene editing is feasible without ex vivo HSPC culture. Importantly, the editing induced therapeutically significant levels of HbF to reverse the phenotypes of both sickle cell disease and β-thalassemia major. These findings imply that PRR-βE1 gene editing of patient HSPCs could lead to improved therapeutic outcomes for β-hemoglobinopathy gene therapy.

Effect of a Physical Exercise Program on the Inflammatory Response, Cardiac Functions, Functional Capacity, and Quality of Life in Patients with Sickle Cell Disease

INTRODUCTION

The beneficial effects of physical exercise on functional capacity and inflammatory response are well-known in cardiovascular diseases; however, studies on sickle cell disease (SCD) are limited. It was hypothesized that physical exercise may exert a favorable effect on the inflammatory response of SCD patients, contributing to an improved quality of life. This study aimed to evaluate the effect of a regular physical exercise program on the anti-inflammatory responses in SCD patients.

METHODS

A non-randomized clinical trial was conducted in adult SCD patients. The patients were divided into two groups: 1-Exercise Group, which received a physical exercise program three times a week for 8 weeks, and; 2-Control Group, with routine physical activities. All patients underwent the following procedures initially and after eight weeks of protocol: clinical evaluation, physical evaluation, laboratory evaluation, quality of life evaluation, and echocardiographic evaluation.

STATISTICAL ANALYSIS

Comparisons between groups were made using Student's t-test, Mann-Whitney test, chi-square test, or Fisher's exact test. Spearman's correlation coefficient was calculated. The significance level was set at p < 0.05.

RESULTS

There was no significant difference in inflammatory response between the Control and Exercise Groups. The Exercise Group showed an improvement in peak VO2 values (p < 0.001), an increase in the distance walked (p < 0.001), an improvement in the limitation domain due to the physical aspects of the 36-Item Short Form Health Survey (SF-36) quality of life questionnaire (p = 0.022), and an increase in physical activity related to leisure (p < 0.001) and walking (p = 0.024) in the International Physical Activity Questionnaire (IPAQ). There was a negative correlation between IL-6 values and distance walked on the treadmill (correlation coefficient -0.444, p = 0.020) and the estimated peak VO2 values (correlation coefficient -0.480; p = 0.013) in SCD patients in both groups.

CONCLUSIONS

The aerobic exercise program did not change the inflammatory response profile of SCD patients, nor did it show unfavorable effects on the parameters evaluated, and patients with lower functional capacity were those with the highest levels of IL-6.

Therapeutic perspective for children and young adults living with thalassemia and sickle cell disease

Hemoglobinopathies, including thalassemias and sickle cell disease, are the most common monogenic diseases worldwide, with estimated annual births of more than 330,000 affected infants. Hemoglobin disorders account for about 3.4% of deaths in children under 5 years of age. The distribution of these diseases is historically linked to current or previously malaria-endemic regions; however, immigration has led to a worldwide distribution of these diseases, making them a global health problem. During the last decade, new treatment approaches and novel therapies have been proposed, some of which have the potential to change the natural history of these disorders. Indeed, the first erythroid maturation agent, luspatercept, and gene therapy have been approved for beta-thalassemia adult patients. For sickle cell disease, molecules targeting vaso-occlusion and hemoglobin S polymerization include crizanlizumab, which has been approved for patients ≥ 16 years, voxelotor approved for patients ≥ 12 years, and L-glutamine for patients older than 5 years.    Conclusion: We herein present the most recent advances and future perspectives in thalassemia and sickle cell disease treatment, including new drugs, gene therapy, and gene editing, and the current clinical trial status in the pediatric populations. What is Known: • Red blood cell transfusions, iron chelation therapy and hematopoietic stem cell transplantation have been the mainstay of treatment of thalassemia patients for decades. • For sickle cell disease, until 2005, treatment strategies were mostly the same as those for thalassemia, with the option of simple transfusion or exchange transfusion. In 2007, hydroxyurea was approved for patients ≥ 2 years old. What is New: • In 2019, gene therapy with betibeglogene autotemcel (LentiGlobin BB305) was approved for TDT patients ≥ 12 years old non β0/β0 without matched sibling donor. • Starting from 2017 several new drugs, such as L-glutamine (approved only by FDA), crizanlizumab (approved by FDA and EMA for patients ≥ 16 years), and lastly voxelotor (approved by FDA and EMA for patients ≥ 12 years old).

The perception of pediatric sickle cell anemia patient's caregivers toward hematopoietic stem cell transplantation (single-center experience, Saudi Arabia)

Background

Sickle cell disease (SCD) is a relatively common genetic disorder in Saudi Arabia characterized by the predominance of sickle hemoglobin (HbS). Although multiple supportive care options exist for patients with SCD, hematopoietic stem cell transplantation (HSCT) is the only cure available and has become highly successful, with an almost 91% overall survival rate. However, pursuing this procedure is still restrained as a curative treatment option. Therefore, this study aimed to evaluate the perception of parents' caregivers at the National Guard Hospital pediatric hematology clinic regarding using HSCT as a curative approach for their children with SCD.

Methods

This is a cross-sectional study of the interviewer-administered survey distributed utilizing electronic devices to caregivers of pediatric patients with SCD. Subjects were recruited from Pediatric Hematology & Oncology clinics at National Guard Hospital Affairs in King Abdulaziz Medical City, Jeddah, Saudi Arabia. An estimated sample size of 100 was initially calculated out of 140 pediatric SCD patients; 72 responses were collected from participants. All study participants gave informed consent. All results were analyzed using SPSS; moreover, statistics were set at a CI of 95% and a p < 0.05. In addition, inferential and descriptive statistics were done.

Results

Of all respondents, 42 (67.8%) would accept HSCT if their hematologist recommended it. However, approximately 7 (11.3%) were not interested in the procedure, and the rest, 13 (21%), were uncertain. The most reported reasons for HSCT rejection among all respondents were attributed to side effects 31 (50.8%), lack of knowledge 8 (13.1%), and misconception toward the procedure 22 (36.1%).

Conclusion

The results of this study were consistent with the fact that most caregivers would follow along with HSCT if it seemed to be fit and was recommended by their hematologists. However, to the best of our knowledge, our study being the first of its kind in the region, further research in the kingdom on the perception of HSCT is needed. Nonetheless, further patient education, an increase in caregivers' knowledge, and enlightenment of the medical team on HSCT as a curative option for sickle cell disease are vital.

Rhabdomyolysis aggravates renal iron accumulation and acute kidney injury in a humanized mouse model of sickle cell disease

Individuals with sickle cell disease (SCD) are at greater risk of rhabdomyolysis, a potentially life-threatening condition resulting from the breakdown of skeletal muscle fibers. Acute kidney injury (AKI) is one of the most severe complications of rhabdomyolysis. Chronic kidney and cardiovascular disease, which account for SCD mortality, are long-term consequences of AKI. Although SCD elevates the risks of rhabdomyolysis-induced sudden death, the mechanisms that underlie rhabdomyolysis-induced AKI in SCD are unclear. In the present study, we show that, unlike their control non-sickling (AA) counterparts, transgenic homozygous SCD (SS; Townes model) mice exhibited 100% mortality 8-24 h after intramuscular glycerol injection. Five hours after glycerol injection, SS mice showed a more significant increase in myoglobinuria and plasma creatine kinase levels than AA mice. Basal plasma heme and kidney tissue iron levels were significantly higher in SS than in AA mice. In contrast to AA, glycerol-induced rhabdomyolysis aggravated these parameters in SS mice. Rhabdomyolysis also amplified oxidative stress in SS compared to AA mice. Glycerol-treated SS mice exhibited worse renal function, exemplified by a reduction in GFR with a corresponding increase in plasma and urinary biomarkers of early AKI and renal tubular damage. The free radical scavenger and Fenton chemistry inhibitor, TEMPOL, ameliorated rhabdomyolysis-induced AKI in the SS mice. These findings demonstrate that oxidative stress driven by renal iron accumulation amplifies rhabdomyolysis-induced AKI in SCD mice.

Multi-center retrospective study of children with sickle cell disease admitted to pediatric intensive care units in the United States

Data on outcomes and interventions for children with sickle cell disease (SCD) admitted to a pediatric intensive care units (PICU) are unknown. We provide the first comprehensive multi-center report on PICU interventions associated with death, the need for invasive respiratory support or stroke among critically ill children with SCD. We collected retrospective multi-center cohort data from January 1, 2012 to December 31, 2019 utilizing the Virtual Pediatric Systems, LLC database. We identified 3388 unique children with SCD, accounting for a total of 5264 PICU admissions from 138 PICUs. The overall mortality rate for the PICU admissions cohort was 1.8% (95/5264 PICU admissions, 95/3388 [2.8%] of all unique patients), the rate of needing of needing Invasive Respiratory Support (IRS, a composite category of exposure) was 21.3% (872/4093 PICU admissions with complete data) and the overall rate of stroke (ischemic or hemorrhagic) was 12.5% (657/5264 PICU admissions). In multivariable analysis adjusting for admission age category, sex, race/ethnicity, PRISM-3 score at admission, exposure to IRS, quartile of unit volume of patients with SCD, and patient origin, admitted children who needed invasive respiratory support (IRS) had higher adjusted odds ratios for mortality (adjusted odds ratio [aOR], 19.72; 95% confidence interval [CI] 8.98-43.29; p < 0.001), although admitted children > 2 years old had decreased aOR for needing IRS (aOR 0.25-0.62; 95% CI 0.16-0.94; p < 0.001-0.025). By contrast, admitted children > 2 years old had a strikingly increased aOR for stroke (aOR 7.57-16.32; 95% CI 2.25-52.15; p < 0.001). These groups may represent PICU-specific subsets of patients with SCD who are at higher risk for more serious illness and should deserve early consideration for referral to a pediatric institution providing comprehensive care for patients with SCD.

A Pharmacometrics Model to Characterize a New Type of Target-Mediated Drug Disposition (TMDD) - Nonlinear Pharmacokinetics of Small-Molecule PF-07059013 Mediated By Its High-capacity Pharmacological Target Hemoglobin With Positive Cooperative Binding

In general, small-molecule target-mediated drug disposition (TMDD) is caused by the interaction of a drug with its high-affinity, low-capacity pharmacological target. In the current work, we developed a pharmacometrics model to characterize a new type of TMDD, where the nonlinear pharmacokinetics (PK) is mediated by a high-capacity pharmacological target with cooperative binding instead of target saturation. The model drug we used was PF-07059013, a noncovalent hemoglobin modulator that demonstrated promising preclinical efficacy to treat sickle cell disease (SCD), and showed complex nonlinear PK in mice with the fraction of unbound drug in blood (fu_b) decreased with an increase in PF-07059013 concentrations/doses due to the positive cooperative binding of PF-07059013 to hemoglobin. Among the various models we evaluated, the best one is a semi-mechanistic model where only drug molecules not bound to hemoglobin were allowed for elimination, with the nonlinear pharmacokinetics being captured by incorporating cooperative binding for drug molecules bound to hemoglobin. Our final model provided valuable insight on target binding-related parameters, such as the Hill coefficient γ (estimated to be 1.6), binding constant K_H (estimated to be 1450 µM), and the amount of total hemoglobin R_tot (estimated to be 2.13 µmol). As the dose selection of a compound with positive cooperative binding is tricky and challenging due to the nonproportional and steep response, our model may be valuable in facilitating the rational dose regimen selection for future preclinical animal and clinical trials for PF-07059013 and other compounds whose nonlinear pharmacokinetics are caused by similar mechanisms.

An open-label, multicenter, phase 2 study of a food enriched with docosahexaenoic acid in adults with sickle cell disease

Sickle cell disease (SCD) induces red blood cell sickling, which causes debilitating symptoms including vaso-occlusion and inflammation. We investigated a food enriched with omega-3 fatty acids to determine its effect on certain factors: blood cell membrane fatty acid composition (including anti-inflammatory elements-docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)-and the pro-inflammatory, arachidonic acid (AA)); the inflammation biomarker, C-reactive protein (CRP); and vaso-occlusive crisis (VOC) pain. Ten adults with SCD ingested the food, daily, for 28 days. Evaluated measures included blood cell membrane fatty acid ratios (AA vs omega-3 (DHA+EPA)), CRP (mg/L) levels, and Visual Analogue Scale (VAS) scores (a VOC assessment). The food was well tolerated and led to a statistically significant CRP reduction (39%). However, changes in omega-3 fatty acid ratios and VAS scores were not significant. Overall, while the omega-3-enriched food reduced inflammation, larger, blinded studies are needed to assess its effectiveness on other measures.

COVID-19 and Sickle Cell Disease: Two Independent Risk Factors for Venous Thromboembolism

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been widely documented as a multi-systemic illness and associated with an increased incidence of thromboses. Likewise, sickle cell disease (SCD) is a hematologic disease responsible for widespread effects on the vasculature and is also associated with elevated thrombotic risk. In this review, we examine the incidence rates of venous thromboembolism (VTE) in SCD and COVID-19 independently and review the mechanisms of coagulopathy associated with both diseases. We describe the possible associations and commonalities between VTE mechanisms, as both diseases cause widespread inflammation that influences each tenet of Virchow's triad. We also discuss current anticoagulation guideline recommendations for the prevention of VTE events in each of these diseases. We report on current literature to date describing rates of VTE in SCD-COVID-19 patients and outline prospective areas of research to further understand the possible synergistic influence of coagulopathy in these patients. The association between SCD and COVID-19 remains a largely under-researched area of coagulopathy in current hematology and thrombotic literature, and our report lays out potential future prospects in the field.

Effects of l-arginine supplementation in patients with sickle cell disease: A systematic review and meta-analysis of clinical trials

Background and Aims

Previous studies have shown that supplementation of some amino acids such as l-arginine or its precursors could exert beneficial effects in patients with sickle cell disease (SCD). The objective of this study is to systematically review the literature to assess the effect of arginine administration on the clinical and paraclinical parameters of patients with SCD.

Methods

Four online databases of PubMed, Web of Sciences, Scopus, and Embase were selected for systematic search. Eligible studies were clinical trials that evaluated the effect of arginine usage in patients with SCD. Effects sizes were calculated using weighted mean difference (WMD) and Hedge's g and they were pooled using random-effects modeling with Hartung-Knapp adjustment. Additional analyses were also conducted.

Results

Twelve studies containing detail of 399 patients with SCD were found to be eligible. The data synthesis showed that l-arginine significantly increased the level of NO metabolites (Hedge's g: 1.50, 0.48-1.82, I 2: 88%) and hemoglobin F (WMD: 1.69%, 0.86-2.52, I 2: 0%) and significantly decreased systolic blood pressure (WMD: -8.46 mmHg, -15.58 to -1.33, I 2: 53%) and aspartate transaminase (Hedge's g: -0.49, -0.73 to -0.26, I 2: 0%). However, there were no significant effects on hemoglobin, reticulocyte, malondialdehyde and diastolic blood pressure, and alanine transaminase.

Conclusion

Our meta-analysis showed that l-arginine use for SCD could be beneficial, increase hemoglobin F and exert blood pressure-lowering and hepatoprotective properties. However, for a firm conclusion and widespread use of  l-arginine for these patients, more studies are needed.

Low Bone Mass and Recurrent Fractures in Neurofibromatosis With Concomitant Hemoglobin SC Disease

Bone disease and bone loss are common features in certain monogenic diseases such as RASopathies, including neurofibromatosis (NF). Similarly, bone complications are frequent in hemoglobinopathies, another group of Mendelian diseases. This paper reports a young patient with both NF and hemoglobin SC (HbSC) diseases who had multiple vertebral fractures with osteopenia. We also discuss the cellular and pathophysiological mechanisms underlying both diseases and the factors responsible for bone pain and low bone mass in NF and hemoglobinopathies such as HbSC. This case emphasizes the importance of careful evaluation and management of osteoporosis in patients with HbSC and NF1, as both are relatively common monogenic diseases in certain communities.

Tranilast reduces cardiomyocyte injury induced by ischemia‑reperfusion via Nrf2/HO‑1/NF‑κB signaling

Tranilast, a synthetic derivative of a tryptophan metabolite, can be used to treat heart diseases. However, the specific mechanism underlying the effect of tranilast on ischemia-reperfusion (I/R) injury-induced cardiomyocyte apoptosis remains unclear. Therefore, the present study aimed to determine if tranilast could attenuate I/R-induced cardiomyocyte injury. A hypoxia/reoxygenation (H/R) model of H9c2 cardiomyocytes was established to simulate I/R-induced cardiomyocyte injury. The viability, apoptosis, inflammation and oxidative stress in H/R-induced H9c2 cells following treatment with tranilast were evaluated by Cell Counting Kit-8 and TUNEL assay. Commercially available kits were used to detect the levels of inflammatory markers and oxidative stress indicators. In addition, the expression levels of the apoptosis- and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1)/NF-κB signalling pathway-associated proteins were detected by western blotting. The levels of reactive oxygen species were determined using 2',7'-dichlorofluorescin diacetate assay kit. The viability of H9c2 cells was decreased following induction with H/R. However, treatment with tranilast increased viability while decreasing apoptosis, oxidative stress and inflammatory response in H/R-induced H9c2 cells by activating Nrf2/HO-1/NF-κB signalling. Furthermore, treatment with ML-385, an Nrf2 inhibitor, reversed the effects of tranilast on H/R-induced H9c2 cells. In conclusion, the results of the present study suggested that tranilast could attenuate I/R-induced cardiomyocyte injury via the Nrf2/HO-1/NF-κB signalling pathway.

Evaluation of lung function in a German single center cohort of young patients with sickle cell disease using EIT and standard techniques

Background and objective

Sickle cell disease (SCD) is a very common autosomal recessive hemoglobinopathy leading to multiple pulmonary complications that are closely associated with mortality. The pathophysiology of chronic pulmonary involvement is not yet fully understood and no specific therapies are available.

Methods

The aim of this cross-sectional study was to characterize the lung function of children and young adolescents with SCD in a German single-center cohort and to extend conventional lung function testing by the use of a new imaging method. We performed spirometry and body plethysmography in 35 children and young adults with hemoglobin SS, SC, S/β-thalassemia as well as 50 controls. These data were compared with clinical characteristics and typical laboratory parameters of hemolysis and disease activity in SCD. To identify lung inhomogeneities, for example due to atelectasis, hyperinflation, air trapping or vascular occlusions, we used the promising new method of electrical impedance tomography (EIT) and calculated global inhomogeneity indices.

Results

Lung function of patients with SCD was significantly reduced compared to that of healthy controls. When the result was found to be pathological, the most commonly observed type of breathing disorder was classified as restrictive. Laboratory parameters showed typical features of SCD including decreased levels of hemoglobin and hematocrit and elevated levels of leucocytes, platelets, lactate dehydrogenase and total bilirubin. However, there was no correlation between blood values and reduced lung function. Electrical impedance tomography (EIT) revealed no abnormalities in SCD patients compared to healthy controls. In particular, we were unable to demonstrate any regional inhomogeneities in lung ventilation.

Conclusion

In our study, SCD patients showed impaired lung function, with a relevant percentage of patients suffering from restrictive breathing disorder. Signs of obstruction could not be detected. Electrical impedance tomography (EIT) measurements revealed no unevenness that would suggest air entrapment, blockage of blood vessels, excessive inflation, obstruction, or other forms of lung disease. Additionally, the reduction in lung function observed in SCD patients was not related to the disease severity or laboratory test results.

Real-world characteristics of patients with sickle cell disease who initiated crizanlizumab therapy

OBJECTIVE

To provide real-word evidence of patients with SCD initiating crizanlizumab, their use of other SCD treatments, and crizanlizumab treatment patterns.

METHODS

Using IQVIA's US-based, Longitudinal Patient-Centric Pharmacy and Medical Claims Databases patients with a diagnosis of SCD between November 1, 2018, and April 30, 2021, and ≥1 claim for crizanlizumab (date of first claim = index date) between November 1, 2019, and January 31, 2021 who were ≥16 years of age, and had ≥12 months of pre-index data were selected for analysis. Two cohorts were identified based on available follow-up time (3- and 6-month cohorts). Patient characteristics were reported along with pre- and post-index SCD treatments and crizanlizumab treatment patterns (e.g. total doses received, gap-days between doses, days on therapy, discontinuation, and restarts).

RESULTS

540 patients met the base inclusion criteria (345 in the 3-month cohort and 262 in the 6-month cohort. Most patients (64%) were female with a mean (SD) age of 35 (12) years overall. Concomitant hydroxyurea use was observed in 19-39% of patients, while concomitant L-glutamine use was observed for 4-8% of patients. 85% of 3-month cohort patients received at least two doses of crizanlizumab, while 66% of the 6-month cohort received at least 4 doses of crizanlizumab. The median number of gap days between doses was 1 or 2.

CONCLUSIONS

66% of patients who receive crizanlizumab receive at least 4 doses within 6-months. The low median number of gap days suggests high adherence.

Occult ischemic bone lesions in children with sickle cell disease: A study of prevalence

INTRODUCTION

Avascular necrosis (AVN) is a severe complication of sickle cell disease (SCD) and involves principally the femoral head. Few data exist about the prevalence of lesions in other segments.

METHODS

In this cross-sectional study, 42 children (20 males and 22 females) underwent a magnetic resonance imaging (MRI) of the spine, upper arms, and femurs. The primary outcome was to define the prevalence and locations of bone infarcts.

RESULTS

Forty-two patients completed the study; the total median age was 11.9 years (interquartile range = 9.5-13.9). Eleven patients (26.2%) were positive for altered bone findings for a total of 32 lesions. Most of the lesions were in the humerus 17 (53.1%), 11 (34.4%) in the femurs, and 4 (12.5%) in the vertebrae. The median number of vaso-occlusive crises (VOCs) was two and four for patients without and with bone lesions, respectively (p = .01). The annual rate of VOC is the best marker for the positive MRI (odds ratio = 82.6; p = .03), and it is correlated with the number of sites involved (p = .02).

CONCLUSIONS

Our study highlights that the prevalence of skeletal lesions could be underestimated, and it provides the basis for clinical reasoning and tailored therapy in SCD children.

Sickle Cell Trevor Thompson Transition Project (ST3P-UP) protocol for managing care transitions: Methods and rationale

BACKGROUND

Emerging adults with sickle cell disease (EASCD) experience significant challenges transitioning from pediatric to adult care. Acute care utilization increases, quality of life (QOL) declines, with an increased risk of mortality. Currently, there are no practice standards to guide emerging adults through the transition process. We are creating a structured transition education (STE) based program for EASCD by customizing the Six Core Elements (6 CE) of Health Care Transition model and are evaluating the effectiveness of adding peer mentoring (PM).

METHODS

The Sickle Cell Trevor Thompson Transition Project (ST3P-UP) is an ongoing multi-site, cluster randomized clinical trial with a target enrollment of 537 EASCD aged 16 to 25 years in pediatric care. Each site (n = 14) comprises a pediatric clinic, adult clinic, and a sickle cell disease (SCD) community-based organization (CBO). Sites are randomized 1:1 to either STE or STE + PM. EASCDs are followed prospectively for 24 months. Rapid cycle plan-do-study-act quality improvement (QI) methods are used to implement the STE. The primary objective is to compare the effectiveness of STE + PM versus STE only at decreasing the number of acute care visits per year over 24 months. The secondary objectives are to compare overall healthcare utilization and patient-reported QOL outcomes at 24 months.

CONCLUSION

We aim to demonstrate the feasibility of using a QI approach to implement 6 CE-based practice standards at 14 disparate SCD clinical programs to guide EASCD through the transition process. We hypothesize that adding PM to the STE program will improve acute care reliance, QOL, and satisfaction with transition outcomes.

Altered T-cell profile in sickle cell disease

Background: Impaired immune status due to altered T-cell response in sickle cell disease (SCD) might provide substantial insight into immune activity in SCD patients. Materials & methods: A total of 30 healthy control, 20 SCD patients in a crisis state and 38 SCD patients in a steady state were evaluated for T-cell subsets. Results: A significant decrease in CD8+ (p = 0.012) and CD8+45RA-197+ (p = 0.015) T-cells were observed among SCD patients. Naive T-cells (45RA+197+; p < 0.01) were elevated and effector (RA-197-) and central memory (RA-197+) T-cells were grossly reduced in the crisis state. Negative regression of naive T-cells with CD8+57+ affirmed immune inactivation. The predictor score reflected 100% sensitivity for predicting the crisis state (area under the curve = 0.851; p < 0.001). Conclusion: Monitoring naive T-cells with predictive scores can help assess the early shift from a steady state to a crisis state.

Palatability and Acceptability of Flaxseed-Supplemented Foods in Children with Sickle Cell Disease

Omega-3 fatty acids (w3FAs) have demonstrated benefits in several inflammatory disease states; however, limited research has been conducted in sickle cell disease (SCD). While marine-based w3FAs are used, their strong odor and taste are a barrier to long-term use. Plant-based sources, especially those in whole foods, may circumvent this barrier. We tested whether flaxseed (rich source of w3FAs) was acceptable to children with SCD. A cross-sectional tasting trial of flaxseed added to baked products (cookies, pancakes, brownies) or to readily available foods (applesauce, pudding, yogurt) was conducted among 30 children (median age = 13 years) reporting to a clinic for routine follow-up, sick visits, or transfusion for SCD to determine acceptability. A food preference rank scale (1-7) was used to rank products based on taste, sight, smell, and texture. An average score for each product was computed. Children were also asked to rank their top three products. The top-ranked products were flaxseed baked in brownies and cookies and ground flaxseed added to yogurt. More than 80% of participants indicated willingness to be contacted for a follow-up study in which a flaxseed-supplemented diet would be evaluated for mitigation of SCD-associated pain. In conclusion, flaxseed-enriched products are palatable and acceptable in children with SCD.

Neutrophils as drivers of vascular injury in sickle cell disease

While neutrophils are the main effectors of protective innate immune responses, they are also key players in inflammatory pathologies. Sickle cell disease (SCD) is a genetic blood disorder in which red blood cells (RBCs) are constantly destroyed in the circulation which generates a highly inflammatory environment that culminates in vascular occlusions. Vaso-occlusion is the hallmark of SCD and a predictor of disease severity. Neutrophils initiate and propagate SCD-related vaso-occlusion through adhesive interactions with the activated and dysfunctional endothelium, sickle RBCs, and platelets, leading to acute and chronic complications that progress to irreversible organ damage and ultimately death. The use of SCD humanized mouse models, in combination with in vivo imaging techniques, has emerged as a fundamental tool to understand the dynamics of neutrophils under complex inflammatory contexts and their contribution to vascular injury in SCD. In this review, we discuss the various mechanisms by which circulating neutrophils sense and respond to the wide range of stimuli present in the blood of SCD patients and mice. We argue that the central role of neutrophils in SCD can be rationalized to develop targets for the management of clinical complications in SCD patients.

The oxygen dissociation curve of blood in COVID-19-An update

An impressive effect of the infection with SARS-Co-19 is the impairment of oxygen uptake due to lung injury. The reduced oxygen diffusion may potentially be counteracted by an increase in oxygen affinity of hemoglobin. However, hypoxia and anemia associated with COVID-19 usually decrease oxygen affinity due to a rise in [2,3-bisphosphoglycerate]. As such, COVID-19 related changes in the oxygen dissociation curve may be critical for oxygen uptake and supply, but are hard to predict. A Pubmed search lists 14 publications on oxygen affinity in COVID-19. While some investigations show no changes, three large studies found an increased affinity that was related to a good prognosis. Exact causes remain unknown. The cause of the associated anemia in COVID-19 is under discussion. Erythrocytes with structural alterations of membrane and cytoskeleton have been observed, and virus binding to Band 3 and also to ACE2 receptors in erythroblasts has been proposed. COVID-19 presentation is moderate in many subjects suffering from sickle cell disease. A possible explanation is that COVID-19 counteracts the unfavorable large right shift of the oxygen dissociation curve in these patients. Under discussion for therapy are mainly affinity-increasing drugs.

Leg Ulcers in Sickle Cell Disease: A Multifactorial Analysis Highlights the Hemolytic Profile

Sickle cell disease (SCD) is characterized by the presence of the variant S hemoglobin (HbS). The homozygous genotype (HbSS) is sickle cell anemia (SCA), while the double heterozygous of HbS and HbC (HbSC) is defined as SC hemoglobinopathy. The pathophysiology is based on chronic hemolysis, inflammation, endothelial dysfunction, and vaso-occlusion, which results in vasculopathy and serious clinical manifestations. Sickle leg ulcers (SLUs) are cutaneous lesions around the malleoli frequent in 20% of Brazilian patients with SCD. SLUs present a variable clinical and laboratory pattern modulated by several characteristics that are not fully understood. Hence, this study aimed to investigate laboratory biomarkers and genetic and clinical parameters associated with the development of SLUs. This descriptive cross-sectional study included 69 SCD patients, 52 without SLU (SLU-) and 17 with active or previous SLU history (SLU+). The results showed a higher incidence of SLU in SCA patients and there was no observed association of α-3.7 Kb thalassemia in SLU occurrence. Alterations in NO metabolism and hemolysis were associated with clinical evolution and severity of SLU, in addition to hemolysis modulating the etiology and recurrence of SLU. Our multifactorial analyses demonstrate and extend the role of hemolysis driving the pathophysiological mechanism of SLU.

The NLRP3 inflammasome fires up heme-induced inflammation in hemolytic conditions

Overactive inflammatory responses are central to the pathophysiology of many hemolytic conditions including sickle cell disease. Excessive hemolysis leads to elevated serum levels of heme due to saturation of heme scavenging mechanisms. Extracellular heme has been shown to activate the NLRP3 inflammasome, leading to activation of caspase-1 and release of pro-inflammatory cytokines IL-1β and IL-18. Heme also activates the non-canonical inflammasome pathway, which may contribute to NLRP3 inflammasome formation and leads to pyroptosis, a type of inflammatory cell death. Some clinical studies indicate there is a benefit to blocking the NLRP3 inflammasome pathway in patients with sickle cell disease and other hemolytic conditions. However, a thorough understanding of the mechanisms of heme-induced inflammasome activation is needed to fully leverage this pathway for clinical benefit. This review will explore the mechanisms of heme-induced NLRP3 inflammasome activation and the role of this pathway in hemolytic conditions including sickle cell disease.

Complementary and alternative medicine for children with sickle cell disease: A systematic review

BACKGROUND

Complementary and alternative medicine (CAM) is a popular alternative to opioid and other analgesics in sickle cell disease (SCD). We review the effectiveness, prevalence, and factors associated with CAM use in the pediatric SCD population.

METHODS

The review protocol was created based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A literature search was conducted in MEDLINE, Embase, Cochrane Library, PubMed, and Web of Science.

RESULTS

Twenty-four studies were examined. The prevalence of CAM use in pediatric patients with SCD ranged from 36 to 84.5%. Common inpatient CAM interventions were yoga, virtual reality, and acupuncture, which decreased pain scale scores. Outpatient CAMs were consisted of cognitive behavioral therapy, massage therapy, and guided-imagery, which increased pain tolerability and decreased pain scale scores.

CONCLUSIONS

CAM modalities can decrease pain scale scores. However, the impact of specific CAM modalities on emergency department visits, hospitalizations, and school absences were inconclusive.

Diverse Approaches to Gene Therapy of Sickle Cell Disease

Sickle cell disease (SCD) results from a single base pair change in the sixth codon of the β-globin chain of hemoglobin, which promotes aggregation of deoxyhemoglobin, increasing rigidity of red blood cells and causing vaso-occlusive and hemolytic complications. Allogeneic transplant of hematopoietic stem cells (HSCs) can eliminate SCD manifestations but is limited by absence of well-matched donors and immune complications. Gene therapy with transplantation of autologous HSCs that are gene-modified may provide similar benefits without the immune complications. Much progress has been made, and patients are realizing significant clinical improvements in multiple trials using different approaches with lentiviral vector-mediated gene addition to inhibit hemoglobin aggregation. Gene editing approaches are under development to provide additional therapeutic opportunities. Gene therapy for SCD has advanced from an attractive concept to clinical reality.

Thrombo-Inflammation in COVID-19 and Sickle Cell Disease: Two Faces of the Same Coin

People with sickle cell disease (SCD) are at greater risk of severe illness and death from respiratory infections, including COVID-19, than people without SCD (Centers for Disease Control and Prevention, USA). Vaso-occlusive crises (VOC) in SCD and severe SARS-CoV-2 infection are both characterized by thrombo-inflammation mediated by endothelial injury, complement activation, inflammatory lipid storm, platelet activation, platelet-leukocyte adhesion, and activation of the coagulation cascade. Notably, lipid mediators, including thromboxane A2, significantly increase in severe COVID-19 and SCD. In addition, the release of thromboxane A2 from endothelial cells and macrophages stimulates platelets to release microvesicles, which are harbingers of multicellular adhesion and thrombo-inflammation. Currently, there are limited therapeutic strategies targeting platelet-neutrophil activation and thrombo-inflammation in either SCD or COVID-19 during acute crisis. However, due to many similarities between the pathobiology of thrombo-inflammation in SCD and COVID-19, therapies targeting one disease may likely be effective in the other. Therefore, the preclinical and clinical research spurred by the COVID-19 pandemic, including clinical trials of anti-thrombotic agents, are potentially applicable to VOC. Here, we first outline the parallels between SCD and COVID-19; second, review the role of lipid mediators in the pathogenesis of these diseases; and lastly, examine the therapeutic targets and potential treatments for the two diseases.

Oxidants and Antioxidants in the Redox Biochemistry of Human Red Blood Cells

Red blood cells (RBCs) are exposed to both external and internal sources of oxidants that challenge their integrity and compromise their physiological function and supply of oxygen to tissues. Autoxidation of oxyhemoglobin is the main source of endogenous RBC oxidant production, yielding superoxide radical and then hydrogen peroxide. In addition, potent oxidants from other blood cells and the surrounding endothelium can reach the RBCs. Abundant and efficient enzymatic systems and low molecular weight antioxidants prevent most of the damage to the RBCs and also position the RBCs as a sink of vascular oxidants that allow the body to maintain a healthy circulatory system. Among the antioxidant enzymes, the thiol-dependent peroxidase peroxiredoxin 2, highly abundant in RBCs, is essential to keep the redox balance. A great part of the RBC antioxidant activity is supported by an active glucose metabolism that provides reducing power in the form of NADPH via the pentose phosphate pathway. There are several RBC defects and situations that generate oxidative stress conditions where the defense mechanisms are overwhelmed, and these include glucose-6-phosphate dehydrogenase deficiencies (favism), hemoglobinopathies like sickle cell disease and thalassemia, as well as packed RBCs for transfusion that suffer from storage lesions. These oxidative stress-associated pathologies of the RBCs underline the relevance of redox balance in these anucleated cells that lack a mechanism of DNA-inducible antioxidant response and rely on a complex and robust network of antioxidant systems.

Subperiosteal Orbital Hematoma: A Rare Clinical Manifestation of Sickle Cell Disease - A Case Report

Sickle cell disease (SCD), an inherited vaso-occlusive disorder, results in recurrent painful episodes and a variety of serious systemic complications that can lead to severe disabilities and even death. Here, we report a case of a 19-year-old African American patient with homozygous sickle cell trait who presented with right upper lid edema and ptosis, 3 days after his admission to the hospital following a sickle cell crisis. Initially, mistaken as a superinfection in the context of his disease, a diagnosis of orbital abscess was made. Intravenous antibiotics and a proper treatment plan were set accordingly. Only after extensive clinical and radiological examinations, it turned out to be an acute subperiosteal orbital hematoma, a rare clinical manifestation of SCD. The aim of our case report was to highlight the difference in orbital presentation between osteomyelitis and subperiosteal hematoma, as well as spreading awareness among medical professionals and especially ophthalmologists for this rare presentation of orbital wall infarction, as the initial differential diagnosis of SCD patients with ocular involvement.

Lovo-cel gene therapy for sickle cell disease: Treatment process evolution and outcomes in the initial groups of the HGB-206 study

lovo-cel (bb1111; LentiGlobin for sickle cell disease [SCD]) gene therapy (GT) comprises autologous transplantation of hematopoietic stem and progenitor cells transduced with the BB305 lentiviral vector encoding a modified β-globin gene (β^A-T87Q ) to produce anti-sickling hemoglobin (HbA^T87Q ). The efficacy and safety of lovo-cel for SCD are being evaluated in the ongoing phase 1/2 HGB-206 study (ClinicalTrials.gov: NCT02140554). The treatment process evolved over time, using learnings from outcomes in the initial patients to optimize lovo-cel's benefit-risk profile. Following modest expression of HbA^T87Q in the initial patients (Group A, n = 7), alterations were made to the treatment process for patients subsequently enrolled in Group B (n = 2, patients B1 and B2), including improvements to cell collection and lovo-cel manufacturing. After 6 months, median Group A peripheral blood vector copy number (≥0.08 c/dg) and HbA^T87Q levels (≥0.46 g/dL) were inadequate for substantial clinical effect but stable and sustained over 5.5 years; both markedly improved in Group B (patient B1: ≥0.53 c/dg and ≥2.69 g/dL; patient B2: ≥2.14 c/dg and ≥6.40 g/dL, respectively) and generated improved biologic and clinical efficacy in Group B, including higher total hemoglobin and decreased hemolysis. The safety of the lovo-cel for SCD treatment regimen largely reflected the known side effects of HSPC collection, busulfan conditioning regimen, and underlying SCD; acute myeloid leukemia was observed in two patients in Group A and deemed unlikely related to insertional oncogenesis. Changes made during development of the lovo-cel treatment process were associated with improved outcomes and provide lessons for future SCD GT studies.

Allogeneic hematopoietic stem cell transplantation to cure sickle cell disease: A review

Sickle cell disease (SCD) had first been mentioned in the literature a century ago. Advancement in the molecular basis of the pathophysiology of the disease opens the door for various therapeutic options. Though life-extending treatments are available for treating patients with SCD, allogeneic hematopoietic stem cell transplantation (HSCT) is the only option as of yet. A major obstacle before HSCT to cure patients with SCD is the availability of donors. Matched sibling donors are available only for a small percentage of patients. To expand the donor pool, different contrasting approaches of allogeneic HSCT like T-cell replete and deplete have been tested. None of those tested approaches have been without the risk of GvHD and graft rejection. Other limitations such as transplantation-related infections and organ dysfunction caused by the harsh conditioning regimen need to be addressed on a priority basis. In this review, we will discuss available allogeneic HSCT approaches to cure SCD, as well as recent advancements to make the approach safer. The center of interest is using megadose T-cell-depleted bone marrow in conjugation with donor-derived CD8 veto T cells to achieve engraftment and tolerance across MHC barriers, under reduced intensity conditioning (RIC). This approach is in phase I/II clinical trial at the MD Anderson Cancer Centre and is open to patients with hemoglobinopathies.

Role of Primary Care in Bridging Gaps in the Health Care System for Vulnerable Children in the United States of America: A Sickle Cell Disease Case Study

Sickle cell disease (SCD) is a life-threatening condition. Given the nature of the disease and associated complications with high mortality and morbidity rates, it is imperative that patients are diagnosed in early infancy, are established with specialists and general pediatric care immediately, and receive continuity in care. A percentage of patients diagnosed with SCD fall within a vulnerable, at-risk population. This population may face greater social barriers that lead to missed or late diagnosis and therefore delayed management, significantly increasing the risk of morbidity and mortality. Screening tools such as state newborn screens help to identify the diagnosis early. However, patients in vulnerable, at-risk populations who are not established in the health care system may not receive timely communication about their illness and necessary next steps for care. We present a case of a 12-month-old female who is an example of one of the many patients who despite having undergone newborn screening, fell through the cracks due to social barriers including housing instability, food insecurity, and lack of access to transportation. This paper emphasizes the need for and provides a real example of the benefit of access to longitudinal primary care for vulnerable patients. We also demonstrate the role of primary care in clearing the care gaps and coordinating services quickly to ultimately prevent life-threatening complications specifically for children with previously undiagnosed chronic illnesses.

Comparative study between chronic automated red blood cell exchange and manual exchange transfusion in patients with sickle cell disease: A single center experience from Saudi Arabia

BACKGROUND

Red cell transfusion remains the gold standard in managing sickle cell disease (SCD) with severe complications. Offering red blood cell exchange (RBCX) either manual exchange transfusion (MET) or automated RBCX (aRBCX) can reduce the complications of chronic transfusion and maintain target Hb thresholds. This study audits the hospital experience of overseeing adult SCD patients treated with RBCX, both automated and manual, and compares the safety and efficacy.

MATERIALS AND METHODS

This retrospective observational study was conducted as an audit for chronic RBCX for adult patients with SCD in 2015-2019 at King Saud University Medical City, Riyadh, Saudi Arabia.

RESULTS

A total of 344 RBCX for 20 adult SCD patients who were enrolled in regular RBCX, (11/20) patients had regular aRBCX with a total of (157) sessions, and (9/20) patients had MET with a total of (187) sessions. The median level of HbS% post-aRBCX was significantly lower than MET (24.5.9% vs. 47.3%, P < 0.010). Patients on aRBCX had fewer sessions (5 vs. 7.5, P < 0.067) with better disease control. Although the median yearly pRBC units per patient for aRBCX was more than the double needed for MET (28.64 vs. 13.39, P < 0.010), the median ferritin level was 42 μg/L in aRBCX versus 983.7 μg/L in MET, P < 0.012.

CONCLUSION

Compared to MET, aRBCX was more effective in reducing HbS, with fewer hospital visits and better disease control. Although more pRBCs were transfused, the ferritin level was better controlled in the aRBCX group without increasing alloimmunization risk.

Sickle Cell Disease in Early Infancy: A Case Report

Sickle cell disease (SCD) refers to a group of hereditary disorders that result in faulty hemoglobin carriage by the red blood cells. This paper discusses an atypical presentation of SCD in early infancy. Despite current literature suggesting protection by fetal hemoglobin in the first few months of life, we report a diagnosis of SCD at 2 months of age with severe symptoms requiring hospitalization. It is therefore important for clinicians to raise their clinical index of suspicion of SCD in children presenting with severe anemia even though they are less than 6 months old and do not present with classic dactylitis or pain syndromes. Expansion and sustained newborn screening programs for SCD in developing countries could help clinicians and parents plan for early treatment, appropriate prophylaxis, and improved management of SCD complications.

Adhesion molecules and cerebral microvascular hemodynamic abnormalities in sickle cell disease

Cerebrovascular abnormalities are a common feature of sickle cell disease that may be associated with risk of vaso-occlusive pain crises, microinfarcts, and cognitive impairment. An activated endothelium and adhesion factors, VCAM-1 and P-selectin, are implicated in sickle cell vasculopathy, including abnormal hemodynamics and leukocyte adherence. This study examined the association between cerebral expression of these adhesion factors and cortical microvascular blood flow dynamics by using in-vivo two-photon microscopy. We also examined the impact of blood transfusion treatment on these markers of vasculopathy. Results showed that sickle cell mice had significantly higher maximum red blood cell (RBC) velocity (6.80 ± 0.25 mm/sec, p ≤ 0.01 vs. 5.35 ± 0.35 mm/sec) and more frequent blood flow reversals (18.04 ± 0.95 /min, p ≤ 0.01 vs. 13.59 ± 1.40 /min) in the cortical microvasculature compared to controls. In addition, sickle cell mice had a 2.6-fold (RFU/mm2) increase in expression of VCAM-1 and 17-fold (RFU/mm2) increase in expression of P-selectin compared to controls. This was accompanied by an increased frequency in leukocyte adherence (4.83 ± 0.57 /100 μm/min vs. 2.26 ± 0.37 /100 μm/min, p ≤ 0.001). We also found that microinfarcts identified in sickle cell mice were 50% larger than in controls. After blood transfusion, many of these parameters improved, as results demonstrated that sickle cell mice had a lower post-transfusion maximum RBC velocity (8.30 ± 0.98 mm/sec vs. 11.29 ± 0.95 mm/sec), lower frequency of blood flow reversals (12.80 ± 2.76 /min vs. 27.75 ± 2.09 /min), and fewer instances of leukocyte adherence compared to their pre-transfusion imaging time point (1.35 ± 0.32 /100 μm/min vs. 3.46 ± 0.58 /100 μm/min). Additionally, we found that blood transfusion was associated with lower expression of adhesion factors. Our results suggest that blood transfusion and adhesion factors, VCAM-1 and P-selectin, are potential therapeutic targets for addressing cerebrovascular pathology, such as vaso-occlusion, in sickle cell disease.

Understanding pulse oximetry in hematology patients: Hemoglobinopathies, racial differences, and beyond

Pulse oximetry (SpO₂ ) is a widely used, non-invasive method of estimating arterial oxygen saturation. Measurement of SpO₂ relies on comparing the relative absorption of light in the red and infrared regions with the expected absorption pattern of oxygenated and deoxygenation adult hemoglobin. As this screening tool has entered common clinical use, test limitations have emerged, including concern about the risk of overestimation of oxygen saturation by pulse oximetry in a disproportionate number of people with dark skin pigment, leading to potential for underdiagnosis of true hypoxemia. In addition, a range of challenges may arise in patients with increased levels of methemoglobin - whether acquired or inherited - carboxyhemoglobin, or in patients with a subset of inherited variant hemoglobins. It is important for Hematologists, and indeed all clinicians who rely on pulse oximetry, to understand the principles and limitations of this ubiquitous test.

Congenital Disorders of Red Blood Cells

See Bonus NeoBriefs videos and downloadable teaching slides Understanding the physiologic process of red blood cell development in utero and subsequent erythropoiesis in the neonate is crucial as this determines red blood cell structure and therefore function, which is vital to neonatal health. Infants frequently experience anemia, and special consideration must be given to the evaluation of these infants to determine the correct etiology. Traditionally, anemia is conceptualized in terms of inadequate red blood cell production, increased red blood cell destruction, or whole blood loss. This framework translates well to inherited red blood cell defects, which include genetic abnormalities in bone marrow productivity or structure of the red blood cell membrane, enzymes, or hemoglobin. This article highlights fetal and neonatal erythropoiesis and the underlying etiologies of the inherited red blood cell disorders, as well as reviews the appropriate diagnostic evaluation and next steps in management. It is imperative that neonatal clinicians remain informed about these disorders to enable early recognition and treatment, and ultimately to improve outcomes in affected infants.