Sickle Cell Disease Phenotype Research Articles

Identification of genetic variants associated with clinical features of sickle cell disease

Sickle cell disease (SCD) is an inherited blood disorder marked by homozygosity of hemoglobin S, which is a defective hemoglobin caused by a missense mutation in the β-globin gene. However, clinical phenotypes of SCD vary among patients. To investigate genetic variants associated with various clinical phenotypes of SCD, we genotyped DNA samples from 520 SCD subjects and used a genome-wide association study (GWAS) approach to identify genetic variants associated with phenotypic features of SCD. For HbF levels, the previously reported 2p16.1 locus (BCL11A) reached genome significance (rs1427407, P = 8.58 × 10–10) in our GWAS as expected. In addition, we found a new genome-wide significance locus at 15q14 (rs8182015, P = 2.07 × 10–8) near gene EMC7. GWAS of acute chest syndrome (ACS) detected a locus (rs79915189, P = 3.70 × 10–8) near gene IDH2 at 15q26.1. The SNP, rs79915189, is also an expression quantitative trait locus (eQTL) of IDH2 in multiple tissues. For vasoocclusive episode (VOE), GWAS detected multiple significant signals at 2p25.1 (rs62118798, P = 4.27 × 10–8), 15q26.1 (rs62020555, P = 2.04 × 10–9) and 15q26.3 (rs117797325, P = 4.63 × 10–8). Our findings provide novel insights into the genetic mechanisms of SCD suggesting that common genetic variants play an important role in the presentation of the clinical phenotypes of patients with SCD.

Bone-marrow-homing lipid nanoparticles for genome editing in diseased and malignant haematopoietic stem cells.

Therapeutic genome editing of haematopoietic stem cells (HSCs) would provide long-lasting treatments for multiple diseases. However, the in vivo delivery of genetic medicines to HSCs remains challenging, especially in diseased and malignant settings. Here we report on a series of bone-marrow-homing lipid nanoparticles that deliver mRNA to a broad group of at least 14 unique cell types in the bone marrow, including healthy and diseased HSCs, leukaemic stem cells, B cells, T cells, macrophages and leukaemia cells. CRISPR/Cas and base editing is achieved in a mouse model expressing human sickle cell disease phenotypes for potential foetal haemoglobin reactivation and conversion from sickle to non-sickle alleles. Bone-marrow-homing lipid nanoparticles were also able to achieve Cre-recombinase-mediated genetic deletion in bone-marrow-engrafted leukaemic stem cells and leukaemia cells. We show evidence that diverse cell types in the bone marrow niche can be edited using bone-marrow-homing lipid nanoparticles.

Azathioprine/hydroxyurea preconditioning prior to nonmyeloablative matched sibling donor hematopoietic stem cell transplantation in adults with sickle cell disease: A prospective observational cohort study.

Nonmyeloablative, matched sibling donor hematopoietic stem cell transplantation with alemtuzumab/total body irradiation (TBI) conditioning is a curative therapy with low toxicity for adults with sickle cell disease (SCD). However, relatively low donor chimerism levels and graft rejection remain important challenges. We hypothesized that adding azathioprine/hydroxyurea preconditioning will improve donor chimerism levels and reduce graft failure rate. In this prospective cohort study, we enrolled consecutive adult patients with SCD undergoing matched sibling donor transplantation at the Amsterdam UMC. Patients received azathioprine 150 mg/day and hydroxyurea 25 mg/kg/day for 3 months prior to alemtuzumab 1 mg/kg and 300 cGy TBI conditioning. Twenty patients with SCD (median age 26 years [range 19-49], 13 females) were transplanted. Median follow-up was 46.0 months (IQR 21.8-57.9). One-year overall survival and event-free survival (graft failure or death) were both 95% (95% confidence interval 86-100). Mean donor myeloid and T-cell chimerism 1-year post-transplant were 95.2% (SD ±10.6) and 67.3% (±15.3), respectively. One patient (5%) experienced graft failure without autologous regeneration, resulting in infections and death. All other patients had a corrected SCD phenotype and were able to discontinue sirolimus. Three patients were successfully treated with alemtuzumab (1 mg/kg) after the transplant because of declining donor chimerism and cytopenias to revert impending graft rejection. Toxicity was mostly related to sirolimus and alemtuzumab. One patient developed steroid-responsive grade II intestinal acute graft-versus-host disease. Collectively, preconditioning with azathioprine/hydroxyurea prior to nonmyeloablative matched sibling donor transplantation resulted in excellent event-free survival and robust donor T-cell chimerism, enabling the successful withdrawal of sirolimus. ClinicalTrials.gov: NCT05249452.

Point-of-Care Newborn Screening for Sickle Cell Disease at Selected Health Facilities in the Gambia

Sickle cell disease (SCD) contributes significantly to childhood morbidity and mortality in sub-Saharan Africa. Early diagnosis through newborn screening (NBS) and subsequent comprehensive follow-up care will reduce the burden. Up till now, the prevalence of SCD among newborns remains unknown in The Gambia and there is no national NBS programme to address this significant public health issue. We assessed the real-time frequency of SCD in the country and determined differences in the pattern of SCD phenotypes among different ethnic groups. A preliminary prospective feasibility study was done in eight purposively selected hospitals in the seven Health Administrative Regions and Banjul. Consecutive newborn babies delivered or managed in these facilities were screened using HemoTypeSC, a sensitive and specific ELISA-based point-of-care test (POCT). Babies identified as SCD with HemoTypeSC were retested at age ≥6 months using alkaline cellulose acetate hemoglobin electrophoresis (ACAE). Head-to-head comparison between HemoType screening and gold standard HPLC could not be done. 1,168 newborn babies were screened from April 14 to August 12, 2023. Fifteen (1.3%) had homozygous HbS (HbSS), two (0.2%) heterozygous for HbS and HbC (HbSC), 204 (17.5%) had sickle cell trait (HbAS), four (0.3%) heterozygous for HbA and HbC (HbAC), and 943 (80.7%) had normal hemoglobin (HbAA). The 17 with SCD (HbSS and HbSC) comprised of 7 (2.2%) of 324 Fula; 6 (1.4%) of 426 Mandinka; 2 (1.6%) of 125 Jola and 2 (1.3%) of 150 Wolof. Fourteen (82.4%) of the 17 accepted the diagnosis and were enrolled into the SCD program. For these 14, HemoTypeSC had 100% sensitivity with ACAE when repeated at age ≥6 months. In addition to determining the real-time newborn prevalence of SCD and trait in The Gambia for the first time, this pilot study showed that SCD-POCT is feasible in Gambian health facilities.

Mechanisms of Iron-Mediated Renal Injury in a Mouse Model of Sickle Cell Disease

Background: Sickle cell disease (SCD) is a hematologic disorder characterized by polymerization of the mutated hemoglobin S and sickling of red blood cells, leading to hemolysis, release of free heme/iron, and subsequent tissue iron accumulation. The kidney is one of the most frequently affected organs by iron overload, and chronic hemolysis is associated with chronic kidney disease severity in SCD. The potential role of iron overload in causing the observed renal injury in SCD has never been established. The goal of our study is to identify the impact of iron accumulation on the renal phenotype in SCD. We hypothesized that renal iron accumulation causes injury by oxidative stress dependent ferroptosis and/or mitochondrial dysfunction and subsequent kidney damage, that is worse in males than in females. Methods: We used 20-week-old male and female humanized SCD mice (HbSS) and age-matched genetic controls (HbAA). Mice were treated with either vehicle or the iron chelator Deferiprone (DFP, 100 mg/kg/day) for 8 weeks. Urinary excretion of protein and albumin as markers of renal injury were measured. Glomerular filtration rate (GFR) was measured transdermally after injection of FITC-sinistrin. Thiobarbituric acid reactive substance (TBARS) assay was performed for assessment of lipid peroxidation. Mitochondrial bioenergetics was assessed by Oroboros O2k Fluorometer of permeabilized renal cortices. Results: We previously demonstrated comparable iron accumulation in the kidney of male and female mice. However, HbSS males developed a more severe renal injury than females at 20 weeks of age, evidenced by proteinuria (2.52 ± 0.16 vs. 0.55 ± 0.16 mg/24hrs, p=0.0008) and albuminuria (76.44 ± 6.85 vs. 33.9 ± 8.81 μg/24hrs, p=0.0005). There was higher lipid peroxidation, a hallmark of ferroptosis, in the renal cortex of female HbSS than HbAA mice (1.31 ± 0.07 vs. 1.07 ± μM/mg, p=0.04). Bioenergetics studies revealed significantly lower state 3 oxygen consumption rate (108.2 ± 18.1 vs 164.8 ± 9.3 pmol/(s*mg), p=0.05), signifying lower oxidative phosphorylation capacity in HbSS males. In addition, there was significant reduction in state 4◦ respiration (36.4 ± 3.4 vs. 52.8 ± 3.4 pmol/(s*mg), p=0.03) in male HbSS mice. I also detected a decrease in maximum complex IV activity in male HbSS mice (325.5 ± 63.8 vs. 639.5 ± 51.3 pmol/(s*mg), p=0.02). Treatment with DFP improved proteinuria (2.66 ± 0.09 vs. 1.3 ± 0.14 mg/24hrs, p=0.0011) and GFR (165.3 ± 9.4 vs. 236.6 ± 12.6 μl/min, p=0.0058) in male HbSS mice. Conclusion: Iron accumulation causes renal injury which may be attributed to ferroptosis and mitochondrial dysfunction in SCD mice. Funding: NHLBI—R00HL144817 and ASN Norman Siegel Research Grant to MK. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A novel high-titer, bifunctional lentiviral vector for autologous hematopoietic stem cell gene therapy of sickle cell disease

A major limitation of gene therapy for sickle cell disease (SCD) is the availability and access to a potentially curative one-time treatment, due to high treatment costs. We have developed a high-titer bifunctional lentiviral vector (LVV) in a vector backbone that has reduced size, high vector yields, and efficient gene transfer to human CD34+ hematopoietic stem and progenitor cells (HSPC). This LVV contains locus control region cores expressing an anti-sickling βAS3-globin gene and two microRNA adapted short hairpin RNA simultaneously targeting BCL11A and ZNF410 transcripts to maximally induce fetal hemoglobin (HbF) expression. This LVV induces high levels of anti-sickling hemoglobins (HbAAS3 + HbF), while concurrently reducing sickle hemoglobin (HbS). The reduction in HbS and increased anti-sickling hemoglobin impedes deoxygenated HbS polymerization and red blood cell sickling at low vector copy per cell in transduced SCD patient CD34+ cells differentiated into erythrocytes. The dual alterations in red cell hemoglobins ameliorated the SCD phenotype in the SCD Berkeley mouse model in vivo. With high titer and enhanced transduction of HSPC at low multiplicity of infection, this LVV will increase the number of patient doses of vector from production lots to reduce costs and help improve accessibility to gene therapy for SCD.

Sickle Cell Disease Phenotypes and Obstructive Sleep Apnea; Are They Related?

This study aims to compare the polysomnographic features between Arab-Indian and Benin phenotypes of sickle cell disease (SCD). This prospective cross-sectional study was conducted in the Children's Hospital at King Fahad MedicalCity, in Riyadhwhere childrenwere recruited fromthe pediatric hematology clinic and pediatric sleepmedicine. All families were approached and patients who met the inclusion criteria and agreed to participate were included in the study. Eighty four children (37 of whom were females) with SCD were included in the study. Their median (interquartile) age was 9 (6.65, 11) years and their body mass index z score was -1.45 (-2.195, -1.45). The evidence of obstructive sleep apnea (OSA) was more prominent in the Benin phenotype (66.7%) in comparison to those of the Arab-Indian (35.2%) phenotype ( p = 0.006). Additionally, 56.7% of Benin had moderate to severe OSA whereas Arab-Indian had 18% with a ( p = 0.0003). Controlling for other factors, the odds ratio (confidence interval) of having OSA in Benin phenotype was 4.68 (1.42-15.38) times higher as compared to Arab-Indian phenotype. The risk of having OSA as well as the severity of OSA is higher in Benin phenotype as compared to Arab-Indian phenotype which indicates the presence of potential OSA risk factors other than the SCD itself.

Clinical Biomarkers of Acute Vaso-Occlusive Sickle Cell Crisis.

It is known that an inherited blood condition called sickle cell disease (SCD) is a result of one gene. A number of blood and urine biomarkers have been determined in association with lab and clinical history for SCD patients. SCD has numerous interacting pathways associated with it, which have been identified by biomarkers. These mechanisms consist of some examples, such as endothelial vasodilation response, hypercoagulability, hemolysis, inflammation, oxidative stress, vascular dysfunction, and reperfusion injury among others. To effectively manage SCD, a comprehensive panel of validated blood and urine biomarkers must be established. Despite its monogenic inheritance, the complex nature of the SCD phenotype has impeded progress in its treatment. However, significant strides have been made in clinical biotechnology, paving the way for potential breakthroughs. In SCD, a panel of verified blood and urine biomarkers must be established, however. Despite monogenic inheritance, the great complexity of the SCD phenotype has hindered progress in its management. With few exceptions, clinical biomarkers of illness severity have been found through epidemiological investigations; nevertheless, systematic integration of these biomarkers into clinical treatment algorithms has not occurred. Furthermore, sickle cell crisis, the primary acute consequence of SCD, has been difficult to diagnose with the biomarkers now in use. Inadequate care and a lack of appropriate outcome measures for clinical research are the consequences of these diagnostic constraints. A new chapter in SCD customized treatment has begun with recent advancements in molecular and imaging diagnostics. Strategies in precision medicine are especially relevant now that molecular therapies are within reach. The significance of biochemical indicators linked to clinical manifestation and sub-phenotype identification in SCD is reviewed in this research.

Simvastatin-Mediated Nrf2 Activation Induces Fetal Hemoglobin and Antioxidant Enzyme Expression to Ameliorate the Phenotype of Sickle Cell Disease.

Sickle cell disease (SCD) is a pathophysiological condition of chronic hemolysis, oxidative stress, and elevated inflammation. The transcription factor Nrf2 is a master regulator of oxidative stress. Here, we report that the FDA-approved oral agent simvastatin, an inhibitor of hydroxymethyl-glutaryl coenzyme A reductase, significantly activates the expression of Nrf2 and antioxidant enzymes. Simvastatin also induces fetal hemoglobin expression in SCD patient primary erythroid progenitors and a transgenic mouse model. Simvastatin alleviates SCD symptoms by decreasing hemoglobin S sickling, oxidative stress, and inflammatory stress in erythroblasts. Particularly, simvastatin increases cellular levels of cystine, the precursor for the biosynthesis of the antioxidant reduced glutathione, and decreases the iron content in SCD mouse spleen and liver tissues. Mechanistic studies suggest that simvastatin suppresses the expression of the critical histone methyltransferase enhancer of zeste homolog 2 to reduce both global and gene-specific histone H3 lysine 27 trimethylation. These chromatin structural changes promote the assembly of transcription complexes to fetal γ-globin and antioxidant gene regulatory regions in an antioxidant response element-dependent manner. In summary, our findings suggest that simvastatin activates fetal hemoglobin and antioxidant protein expression, modulates iron and cystine/reduced glutathione levels to improve the phenotype of SCD, and represents a therapeutic strategy for further development.

Mortality in adults with sickle cell disease: Results from the sickle cell disease implementation consortium (SCDIC) registry.

The cause of death in people affected by sickle cell disease (SCD) is often challenging to define as prior studies have used retrospective or administrative data for analysis. We used a prospective longitudinal registry to assess mortality and clinical co-morbidities among subjects enrolled in the Sickle Cell Disease Implementation Consortium (SCDIC) registry. At enrollment, we collected the following data: patient-reported demographics, SCD phenotype, baseline laboratory values, comorbidities, and current medications. Subjects were followed for a median of 4.7 years before the present analysis. The relationship of clinical co-morbidities (at time of enrollment) to mortality was determined using survival analysis, adjusting for SCD phenotype and gender. There was a total of 2439 people with SCD enrolled in the SCDIC registry. One hundred and twenty-eight participants (5%) died during the observation period (2017-2022). Six people died from trauma and were excluded from further analysis. Proximate cause of death was unwitnessed in 17% of the deaths, but commonest causes of death include cardiac (18%), acute chest or respiratory failure (11%), sudden unexplained death (8%). Enrollment characteristics of the individuals who died (n = 122) were compared to those of survivors (n = 2317). Several co-morbidities at enrollment increased the odds of death on univariate analysis. All co-morbidities were included in a multivariable model. After backward elimination, iron overload, pulmonary hypertension, and depression, remained statistically significant predictors of the risk of death. SCD reduces life expectancy. Improved comprehensive and supportive care to prevent end-organ damage and address comorbidities is needed for this population.

Neurological abnormalities among pediatric patients with sickle cell disease in Saudi Arabia: a single-center retrospective study.

Sickle cell disease (SCD) is a common inherited blood disorder characterized by the production of abnormal sickle-shaped red blood cells. SCD can lead to various complications including neurological issues. Early detection and treatment are crucial for preventing these complications. This study aimed to describe the neurological manifestations, radiological findings, and neurological diagnosis related to SCD in Saudi children with the aim of contributing to the formulation of population-based guidelines for screening and treating SCD-related neurological complications. This descriptive retrospective study included pediatric patients aged < 14 years diagnosed with SCD who were regularly followed up at the hematology clinic in KAMC, Jeddah, Saudi Arabia, from January 2008 to January 2022. Demographic and clinical data were collected from the clinical charts of 101 participants. This study included 101 patients with SCD with a mean age of 23 months at diagnosis. Among these, 59% had SCD and high fetal hemoglobin (HbF) levels. Neurological sequelae, including seizures, stroke, and other abnormalities, were observed in 26.7% of patients. There were no significant differences in the onset of neurological issues between the patients with SCD-high HbF and those with other SCD phenotypes. This study highlights the increased risk of brain injury and neurocognitive deficits in children with SCD. The occurrence of neurological sequelae in many patients emphasizes the need for early detection and intervention. Some patients experience neurological complications despite having high HbF levels, suggesting that further interventions are needed. This study has some limitations, including its small sample size and retrospective nature. Early detection and intervention are crucial for neurological complications in patients with SCD. This study emphasizes the need for further research and effective treatment strategies considering the presence of neurological complications despite the presence of high HbF levels. Large-scale studies and population-specific guidelines are warranted for better understanding and management of SCD-related neurological complications in the Saudi population.

In vivo measurement of RBC survival in patients with sickle cell disease before or after hematopoietic stem cell transplantation

AbstractStable, mixed-donor–recipient chimerism after allogeneic hematopoietic stem cell transplantation (HSCT) for patients with sickle cell disease (SCD) is sufficient for phenotypic disease reversal, and results from differences in donor/recipient–red blood cell (RBC) survival. Understanding variability and predictors of RBC survival among patients with SCD before and after HSCT is critical for gene therapy research which seeks to generate sufficient corrected hemoglobin to reduce polymerization thereby overcoming the red cell pathology of SCD. This study used biotin labeling of RBCs to determine the lifespan of RBCs in patients with SCD compared with patients who have successfully undergone curative HSCT, participants with sickle cell trait (HbAS), and healthy (HbAA) donors. Twenty participants were included in the analysis (SCD pre-HSCT: N = 6, SCD post-HSCT: N = 5, HbAS: N = 6, and HbAA: N = 3). The average RBC lifespan was significantly shorter for participants with SCD pre-HSCT (64.1 days; range, 35-91) compared with those with SCD post-HSCT (113.4 days; range, 105-119), HbAS (126.0 days; range, 119-147), and HbAA (123.7 days; range, 91-147) (P<.001). RBC lifespan correlated with various hematologic parameters and strongly correlated with the average final fraction of sickled RBCs after deoxygenation (P<.001). No adverse events were attributable to the use of biotin and related procedures. Biotin labeling of RBCs is a safe and feasible methodology to evaluate RBC survival in patients with SCD before and after HSCT. Understanding differences in RBC survival may ultimately guide gene therapy protocols to determine hemoglobin composition required to reverse the SCD phenotype as it relates directly to RBC survival. This trial was registered at www.clinicaltrials.gov as #NCT04476277.

Sickle Cell Anemia Screening in Newborns and Analysis of Haplotypes in Patients from Santiago Island, Cape Verde.

Sickle cell anemia (SCA) results from a mutation in the β-globin gene, leading to the production of mutant hemoglobin, known as hemoglobin S (HbS). Despite being a genetic disorder, the phenotype of SCA can be influenced by the level of fetal hemoglobin (HbF), which is associated with beta S-globin haplotypes. In this study, we conducted newborn screening (NBS) using samples collected from umbilical cord blood in two hospitals on Santiago Island, Cape Verde. In newborns, HbS was detected using high-performance liquid chromatography (HPLC) on dried blood spot, with confirmation through polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). In addition, we assessed the hematological and clinical characteristics of a second population group consisting of patients diagnosed with SCA. Haplotype determination was performed on both newborns with HbS and patients with SCA. Beta S-globin haplotypes were determined using PCR-RFLP. Hematological values were analyzed using standard methods. Out of 346 newborns, 21 (6%) were carriers of the sickle cell trait (HbAS) while none were identified as homozygous for sickle cell disease (HbSS). Among both groups of individuals, four haplotypes were identified: Senegal, Arabi-Indian, Bantu, and Benin. The Senegal haplotype was the most prevalent, possibly reflecting the ethnic origin of the mutations observed. Hematological values did not differ significantly among haplotypes. However, higher levels of HbF were associated with better hematological values. These findings suggest a positive impact of elevated HbF levels on reducing the severity of SCA. Finally, we demonstrated how the combination of technics, HPLC and molecular analysis, provided a consistent and reproducible results that can be used for NBS for SCA.

Renal outcomes in pediatric patients with sickle cell disease: a single center experience in Saudi Arabia.

Sickle cell nephropathy (SCN) is a significant complication of sickle cell disease (SCD) with an asymptomatic onset in childhood and potential progression to chronic kidney disease (CKD). The clinical findings of SCN include hyposthenuria, hematuria, proteinuria, hyperfiltration, and CKD. Data on renal manifestation among patients with SCD in Saudi Arabia is lacking. Therefore, this study aimed to evaluate renal outcomes in patients with SCD who visited a hematology clinic at the National Guard Hospital, Jeddah. We conducted a retrospective chart review of renal complications in patients with SCD who are within 0-14 years of age and on regular follow-ups at the pediatric hematology clinic in King Abdulaziz Medical City-Jeddah, Saudi Arabia. Among the 140 patients with SCD, 99 met the inclusion criteria. The median age at diagnosis was 18 (1-108) months. Two SCD phenotypes were observed, with 82 (83%) patients having sickle cell anemia (HbSS) and 17 (17%) having HbS/B+ thalassemia. Of the total patients, 92 (93%) were administered hydroxyurea (HU), with a median starting age of 48 (9-168) months. The most common renal complication observed during routine urinalysis was hematuria (38%), followed by proteinuria (11%). After stratifying the sample into four age groups (0-3 years old, 4-7 years old, 8-11 years old, and 12-14 years old), the mean glomerular filtration rate (GFR) values were 96.16, 101.36, 112.69, and 120.11 ml/min/1.73 m2 respectively. Renal imaging revealed abnormal findings in 27 (29%) patients. The most common abnormality observed on US was increased echogenicity (43%). SCN is a significant complication of SCD. In this study, we assessed the renal outcomes in pediatric patients with SCD. After analyzing the clinical findings of SCN, we concluded that the presence of renal complications in pediatric patients presented a progressive pattern.

Pharmacologic Reduction of Platelet Count Attenuates Whole Blood Hypofibrinolysis in a Mouse Model of Sickle Cell Disease

Increased risk of venous thrombosis is a hallmark of sickle cell disease (SCD). We previously reported that SCD dramatically alters the properties of venous clots, including resistance to tissue plasminogen activator (tPA)-mediated fibrinolysis. Using an internal fibrinolysis assay (tPA added to whole blood before clot formation), clot lysis time (CLT) was significantly (p&amp;lt;0.01) prolonged in clots formed ex vivo from whole blood of SCD patients (SS) (651±34 min) compared to race-matched controls (AA) (370±75). We then investigated how therapeutic RBC exchange affects CLT in SCD patients. Interestingly, despite hemoglobin A levels of approximately 50%, CLT for the pre-exchange SS clots (639±81 min) was similar to CLT recorded for blood clots from SS patients who did not undergo RBC exchange (see above). However, CLT for post-exchange SS clots was significantly shortened (240±34; p&amp;lt;0.05 vs pre-exchange) to the level observed for clots from AA controls. We noticed that the RBC exchange procedure not only changes the proportion of AA and SS RBCs, but also reduces both platelet counts and serum plasminogen activator inhibitor-1 (PAI-1) levels by approximately 50-60%. Importantly, exvivo restoration of the platelet number in post-exchange samples to the level observed in pre-exchange blood resulted in restoration of the hypofibrinolytic phenotype and a partial restoration of serum PAI-1 levels. Changes in platelet count after RBC exchange are quickly normalized. Therefore, in the current study, we investigated the effect of sustained reduction of platelet count on whole blood hypofibrinolysis in SCD mice. Using an external fibrinolysis assay (2.5 nM tPA added after clot formation) as described by Bonnard et al. (Sci Rep, 2017) we determined if hypofibrinolysis is also observed in Townes sickle cell mice (SS). Consistent with human SCD, the CLT was profoundly increased in ex vivo clots formed from whole blood of SS mice (n=13) compared to non-sickle (AA) control mice (n=12) (Figure 1A; first two bars). Next, we demonstrated that the cellular fraction of SS blood was responsible for resistance of the clots to tPA-mediated fibrinolysis, regardless of whether the plasma was from SS or AA mice (Figure 1A; last four bars). We then used a pharmacologic strategy to reduce platelet counts. Thrombopoietin (TPO) is a growth factor that promotes maturation of hematopoietic stem cells into megakaryocytes and thereby increases platelet production. We previously showed that silencing liver TPO expression using a liver-specific antisense oligonucleotide (TPO-ASO) resulted in a sustained 50% reduction in both plasma TPO levels and platelet counts without affecting hemostasis in both baboons and mice. In the present study, TPO-ASO (20 mg/kg subcutaneous) or vehicle control were administered to 3-month old AA and SS mice (n=3-6) on days 0, 3, 5 and 7, followed by weekly maintenance injections for the next 3 weeks. 4 weeks after initiation of treatment, mice were euthanized, and blood was collected to evaluate plasma levels of TPO and external whole blood fibrinolysis. Platelet, but no other cell count was significantly reduced in both AA (by 62%, p&amp;lt;0.05) and SS (by 47%, P&amp;lt;0.05) mice treated with TPO-ASO. Baseline plasma levels of TPO were reduced in SS mice (101±20 pg/ml) compared to AA controls (182±10; p&amp;lt;0.05). TPO-ASO treatment resulted in significant reduction of TPO plasma levels in both AA (21±16; p&amp;lt;0.01) and SS (17±9; p&amp;lt;0.05) mice. Interestingly, TPO-ASO-mediated reduction of platelet count did not affect CLT of ex vivo clots formed from whole blood of AA mice (Figure 1B). In contrast, TPO-ASO treatment dramatically reduced CLT in SS clots (p&amp;lt;0.05) (Figure 1B). In conclusion, we demonstrated that: (i) the resistance of ex vivo formed clots to tPA-mediated fibrinolysis observed in SCD patients can be reproduced in a mouse model of the disease; (i) the external fibrinolysis assay provides a robust and reliable model for studying whole blood hypofibrinolysis in SCD; (iii) hypofibrinolysis in SCD appears to be predominantly driven by the cellular fraction of blood; and (iv) platelets play an important role in the hypofibrinolytic phenotype in SCD, demonstrated by mitigation of the hypofibrinolytic phenotype in SS mice subjected to long-term reduction of platelet count. Further studies investigating the effect of platelet count reduction on venous thrombosis and vascular stasis in SS mice are currently ongoing.

Initial Results in a Phase 1b Trial of PB-04 in Sickle Cell Disease Demonstrate Fetal Hemoglobin Induction, Additive Activity with Hydroxyurea, and Improved Red Blood Cell Sickling Parameters

Extensive evidence has shown fetal hemoglobin (HbF) is a major modulator of sickle cell disease (SCD) phenotype. Clinical benefit with any increment of HbF was shown in the NIH-sponsored Natural History Study and the Multicenter Study of Hydroxyurea (HU), with mean HbF increases of 3.6% above baseline (BL), to improve survival, reduce painful vaso-occlusive crises, and recently stroke prevention and improved cardiac and neurocognitive function with HU are reported. As some patients do not tolerate optimal HU doses due to cytopenias, additional inducers suitable for combined use are desirable. Proportions of F-cells and HbF-quantity/cell have been cited as important. PB-04, a repurposed drug with a well-known safety profile, is an oral fetal globin stimulant identified in high throughput screening, which suppresses 4 repressors of the HMG gene promoter, ( BCL-11A, LSD-1, HDAC-3, KLF-1). PB-04 induces fetal globin in nonhuman primates, transgenic mice, with additive effect when combined with HU in SCD erythroid progenitors, and was shown to reduce infarcts in multiple organs with preserved splenic function in transgenic sickle mice. An ongoing Phase 1b trial in beta thalassemia intermedia (BTI) ( NCT04432623) of 3 doses (1,3, or 5 mg/kg QD) given 3 (TIW) or 5 times/week (Wk) for 12 or 24 Wks in 18 courses in 10 subjects demonstrates a favorable safety profile, dose-proportional PK with 5 &amp;gt;3 mg/kg doses and 5 &amp;gt;3 doses/Wk, Median fold-increases from baseline (BL) in F-cells of 4.4x BL (range 2.3-7x), 2.8x F-reticulocytes (1.6-14.8x), and 6.5x (range 3-11x) increases in mean fluorescence intensity (MFI, representing amount of HbF/RBC). Mean increases in % HbF were 6.5%. Evaluation of PB-04 has now begun in 7 subjects with SCD, 19-51 yrs; 3 were receiving HU with HbF responses (12-22%). Adverse events, F-cells, F-reticulocytes, MFI (amount of HbF/RBC or HbF/reticulocyte) by FACS and ImageStream Analysis and % HbF are assessed Q 4 wks; flow adhesion of whole blood to VCAM-1 (FA-WB-VCAM) and sickling kinetics are assessed q 12 wks. In 4 subjects on 3 mg/kg QD TIW for 24 wks, changes observed from BL values included mean increases of 6% F-cells and 27% F-reticulocytes (2-fold) . In 3 ongoing subjects receiving 5 mg/kg QD TIW for 12 wks mean changes above BL are currently 13% F-cells, 15% F-reticulocytes; HbF/cell or HbF/reticulocyte have increased up to 10-fold. Mean % HbF has increased above HU effects in 2/3 pts on the second dose by 5-12.6% (mean 8.8%), producing 81-95% F-cells, and 35-38% HbF. Decline in FA-WB-VCAM) was observed ± HU and with both doses in 3 subjects. Correlation of HbF quantity/cell with RBC survival and sickling dynamics is being explored. These early results with not-yet-optimized doses of PB-04 suggest additive activity with HU, producing significant HbF and F-cell levels, and support further PK-optimized studies in patients with SCD.

A Genotype Validated Bimodal Method for the Large-Scale Identification and Phenotyping of Persons with Sickle Cell Disease Using Electronic Health Record Data

Introduction Clinical trials for using hematopoietic stem cell transplant (HSCT) with gene therapies to cure sickle cell disease (SCD) began in 2019. The Food and Drug Administration (FDA) requires that 1) all gene therapy participants receive at least 15 years of ongoing surveillance and 2) their outcomes be compared to a contemporaneous cohort that did not receive gene therapy. Previously we developed an automated contemporaneous cohort of children and adults with SCD from electronic health record (EHR) data (Cronin RM et al. 2023, Blood Adv). Our work was built upon previously explored algorithms utilizing ICD codes and laboratory data to identify persons with sickle cell anemia (SCA), a severe form of SCD (Singh et al. 2018, Blood Adv). Still, our algorithm additionally classifies other predicted genotypes. However, we could not test the SCD phenotypes against the SCD genotypes due to the absence of beta-globin gene sequence data. Here we tested the hypothesis that our Vanderbilt-EHR algorithm for identifying a contemporaneous cohort at Vanderbilt can classify their predicted genotype compared to beta-globin gene sequencing, the gold standard for SCD diagnosis, in the cohort. We subsequently tested the Vanderbilt-EHR algorithm in an established cohort of children from St. Jude Children's Research Hospital that have been deeply phenotyped. Methods We applied the Vanderbilt-EHR algorithm to a cohort of 275 samples from Vanderbilt's biorepository of DNA, BioVU, linked to de-identified medical records in a data warehouse called the Synthetic Derivative. These 275 samples were previously submitted for whole genome sequencing as part of the Genetic Variation of Heart, Lung, and Kidney Disease in Sickle Cell Disease: Pre- and Post-Curative Therapies TOPMed project (HLK-SCD phs002617). The returned genotypes were validated using the hemoglobin variant database HbVar (Giardine BM et al. 2021, Nucleic Acids Res) (Table 1). We applied the hemoglobinopathy genotype classification portion of the algorithm to the Sickle Cell Clinical Research and Intervention Program (SCCRIP) cohort from St. Jude Children's Research Hospital, which includes putative genotype diagnoses derived from a comprehensive evaluation of clinical data for each member. We performed statistical analyses of the identification and classification results of the Vanderbilt cohort and the SCCRIP cohort's classification results. Results Of the 275 genotyped samples, the algorithm correctly predicted 255 SCD cases and 10 non-SCD cases. There were three cases predicted to be false positives; however, a comprehensive analysis showed that all have laboratory values indicative of SCA (high hemoglobin S levels &amp;gt;60%, absent or negligible hemoglobin A levels, elevated reticulocytes, and low mean corpuscular volume) suggesting that there may be a genotyping error. The remaining 7 cases were either indeterminate in the prediction or in the genotype (Table 1). Given the small number of indeterminate results, we performed a sensitivity analysis to identify the range of performance for SCD identification. The method performed very well with over 98% sensitivity and over 96% positive predictive value (PPV) (Table 2). The lower specificity and negative predictive value (NPV) could be largely attributed to the disproportionately high number of SCD cases in the dataset compared to non-SCD cases. The SCD classification algorithm performed similarly in both the VUMC and SCCRIP cohorts (Table 2). The algorithm performs best in identifying SC and SCA types of SCD with nearly 100% accuracy for SC and over 94% accuracy for SCA. Transfusions can confound the diagnosis of SCA vs. S beta thalassemia +, but the latter has a much lower prevalence consistent with our results (Table 2). Discussion and Conclusions Larger SCD cohorts will be identified using these approaches in singular EHR databases and in de-identified data warehouses that EHR companies have developed by aggregating data across multiple EHR systems (e.g., EPIC Cosmos and Cerner Real-World Data). The ongoing need for contemporaneous comparison cohorts of persons with SCD to understand outcomes related to treatment and phenotype can be greatly assisted by accurate automated approaches. The Vanderbilt-EHR algorithm is the first to comprehensively phenotype SCD and other hemoglobinopathies involving variant hemoglobin beta alleles.

Pain Frequency and Health Care Utilization Patterns in Women with Sickle Cell Disease Experiencing Menstruation-Associated Pain Crises.

Background: Pain crises in sickle cell disease (SCD) lead to high rates of health care utilization. Historically, women have reported higher pain burdens than men, with recent studies showing a temporal association between pain crisis and menstruation. However, health care utilization patterns of SCD women with menstruation-associated pain crises have not been reported. We studied the frequency, severity, and health care utilization of menstruation-associated pain crises in SCD women. Materials and Methods: A multinational, cross-sectional cohort study of the SCD phenotype was executed using a validated questionnaire and medical chart review from the Consortium for the Advancement of Sickle Cell Research (CASiRe) cohort. Total number of pain crises, emergency room/day hospital visits, and hospitalizations were collected from a subcohort of 178 SCD women within the past 6 months and previous year. Results: Thirty-nine percent of women reported menstruation-associated pain crises in their lifetime. These women were significantly more likely to be hospitalized compared with those who did not (mean 1.70 vs. 0.67, p = 0.0005). Women reporting menstruation-associated pain crises in the past 6 months also experienced increased hospitalizations compared with those who did not (mean 1.71 vs. 0.75, p = 0.0016). Forty percent of women reported at least four menstruation-associated pain crises in the past 6 months. Conclusions: Nearly 40% of SCD women have menstruation-associated pain crises. Menstruation-associated pain crises are associated with high pain burden and increased rates of hospitalization. Strategies are needed to address health care disparities within gynecologic care in SCD.

Improved Biorepository to Support Sickle Cell Disease Genomics and Clinical Research: A Practical Approach to Link Patient Data and Biospecimens from Muhimbili Sickle Cell Program, Tanzania.

In Africa, sickle cell disease phenotypes' genetic contributors remain understudied due to the dearth of databases that pair biospecimens with demographic and clinical details. The absence of biorepositories in these settings can exacerbate this issue. This article documents the physical verification process of biospecimens in the biorepository, connecting them to patient clinical and demographic data and aiding in the planning of future genomic and clinical research studies' experience from the Muhimbili Sickle Cell Program in Dar es Salaam, Tanzania. The biospecimen database was updated with the current biospecimen position following the physical verification and then mapping this information to its demographic and clinical data using demographic identifiers. The biorepository stored 74,079 biospecimens in three -80°C freezers, including 63,345 from 5159 patients enrolled in the cohort between 2004 and 2016. Patients were identified by a control (first visit), entry (when confirmed sickle cell homozygous), admission (when hospitalized), and follow-up numbers (subsequent visits). Of 63,345 biospecimens, follow-ups were 46,915 (74.06%), control 8067 (12.74%), admission 5517 (8.71%), and entry 2846 (4.49%). Of these registered patients, females were 2521 (48.87%) and males were 2638 (51.13%). The age distribution was 1-59 years, with those older than 18 years being 577 (11.18%) and children 4582 (88.82%) of registered patients. The notable findings during the process include a lack of automated biospecimen checks, laboratory information management system, and tubes with volume calibration; this caused the verification process to be tedious and manual. Biospecimens not linked to clinical and demographic data, date format inconsistencies, and lack of regular updating of a database on exhausted biospecimens and updates when biospecimens are moved between positions within freezers were other findings that were found. A well-organized biorepository plays a crucial role in answering future research questions. Enforcing standard operating procedures and quality control will ensure that laboratory users adhere to the best biospecimen management procedures.

Prevalence of Duffy Null Status and Its Impact on Hydroxyurea Dosing in Young Children with Sickle Cell Disease in the United States

Background: Sickle cell disease (SCD) affects approximately 100,000 Americans and causes many morbidities mediated by inflammation. Hydroxyurea (HU), the primary SCD therapy, demonstrates superior outcomes with dose-escalation. While HU induces fetal hemoglobin, it also reduces absolute neutrophil counts (ANC) and inflammation. However, ANC is used to determine if HU can be dose-escalated. Thus, a lower baseline ANC has potential to limit dose escalation and outcomes. The Duffy null phenotype, ubiquitous among West Africans, reduces ANC through neutrophil egress from the blood into tissues.While this does not increase infection risk, its prevalence and impact on ANC, HU dosing, and outcomes among children with SCD in the U.S. are unknown. Thus, the primary objective of this study was to determine prevalence of Duffy null among children with SCD (any genotype) receiving care and who had erythrocyte phenotyping performed at a large, Midwestern SCD center between 2010-2022. We also aimed to compare baseline ANC of children with SCD and Duffy null and to children with SCD and Duffy positive phenotypes at their one-year hematology visit (overall and by genotype severity). Finally, in those who initiated HU, we aimed to compare ANC, HU dosing, and the frequency of acute healthcare utilization for SCD complications between groups during the first year of HU use. Methods: This was a retrospective study of children with SCD. Subjects were identified using a list of those who had phenotyping performed at the center and confirmed to have SCD in their electronic health records. Individuals with Fy a-Fy b- were considered to be Duffy null. Data abstracted included demographics (e.g., age, race) and laboratory studies (e.g., hemoglobin (Hb), ANC). HU prescribing information and emergency department and/or admissions among those who used HU for ≥1year were also recorded. Descriptive statistics (median and interquartile range (IQR)) were used and Chi-squared, Fisher's exact, and Wilcoxon rank sum were used to compare categorical and continuous groups; p-value &amp;lt;0.05 was considered statistically significant. Results: Of 187 children with SCD who had phenotyping; 147 (78.6%) had Duffy null (Table 1) and were compared to Duffy positive children with SCD (Figure 1). A subset of 72 children with Duffy null and 22 with Duffy positive initiated HU;59 with Duffy null and 15 with Duffy positive remained on HU for ≥1 year. Median HU doses at initiation (p=0.72) and at one year (p=0.35) did not significantly differ between groups. Median ANC at HU initiation was 4.0 mm 3 (IQR 3.3.-5.9) in the Duffy null group and 5.0 mm 3 (IQR 3.2-6.8) in the Duffy positive group but this difference was not significantly different (p=0.21), nor was median ANC at one year between groups (2.0 mm 3, IQR 1.9-4.2 vs. 3.7 mm 3, IQR 2.8-4.9, p=0.07). Median number of acute visits did not differ between the Duffy null (0, IQR 0-1) and Duffy positive (0, IQR 0-1) groups (p=0.65). Discussion: We identified that Duffy null, while not ubiquitous, was present in more than three fourths of young children with SCD in the Midwest and was associated with having a lower ANC at one year of life. Given that HU dose-escalation improves outcomes, it was reassuring that those with Duffy null on HU did not have a significantly lower ANC and were not prescribed lower dose HU than Duffy positive children at either point. However, it is notable that these may be because few children in both groups had ANC low enough to preclude HU initiation or escalation based on dosing guidelines and because acute visits were infrequent. Limitations include the retrospective design, small number of those who initiated and remained on HU for ≥1 year, and short time interval that clinical and laboratory outcomes were compared. Also, it is possible that some did not have phenotyping completed, but standard practice at our center is to complete phenotyping on all with SCD. In conclusion, Duffy null is highly prevalent in young children with SCD in the U.S. While this does not appear to have an impact on HU dosing of young children with SCD early in their HU course, subsequent longitudinal studies of older children are needed to explore if Duffy null has an impact on longer-term HU dosing and outcomes.