Bridging the Access Gap for Comprehensive Sickle Cell Disease Management Across Sub-Saharan Africa: Learnings for Other Global Health Interventions?

Background: Sickle cell disease (SCD) is a major unresolved global health issue, with the highest disease burden in sub-Saharan African countries; yet, SCD care has not proportionally reached patients in these regions, and the disease has received limited attention in the past. Addressing the burden of SCD in sub-Saharan Africa requires a holistic, collaborative approach to ensure solutions are both comprehensive - i.e., cover the entire continuum of care from early diagnosis to treatment - and sustainable - i.e., are co-created and co-owned with local partners and integrated into existing local systems to enable long-term independence without the need for continuous external support. Objective: We outline a set of recommendations for enhancing the provision of comprehensive healthcare for prevalent diseases in resource-constraint settings, gathered from the Novartis Africa SCD Program, that could serve as 'blueprint' for public-private partnerships to tackle global health priorities. Methods: The Novartis Africa SCD program was initiated with the aim to bridge access gaps to SCD care and provide comprehensive and innovative treatment solutions for SCD, especially in SSA where the disease burden is highest. The Program was first inaugurated in 2019 in Ghana through a public-private partnership with the Ministry of Health of the Government of Ghana, the Ghana Health Service, and the Sickle Cell Foundation of Ghana. Through engagement with these partners, as well as with support from other organizations with complementary competencies and resources, several targeted solutions were implemented to help strengthen the healthcare ecosystem to allow for comprehensive SCD management. Learnings from these interventions are highlighted as best practice consideration as a catalyst and to activate more public-private actors for this neglected global health issue. Findings and Conclusions: A solid understanding of the access barriers to comprehensive care has to be acquired by listening to and learning from patients, civil society, and local experts. Access barriers need to be addressed at multiple levels, i.e., by not only making medicines available and affordable, but also by strengthening healthcare systems, building capacity, and fostering local research and development. Partnerships across governmental, public, academic, non-profit, and private organizations are needed to secure political will, pool resources, gather expertise with understanding of the local context, and allow integration into all levels of existing local healthcare structures and the wider society.

Access to essential therapy for sickle cell disease in Africa: Experience from a national program in Ghana.

Novartis, a global medicines company, and the Sickle Cell Foundation of Ghana (SCFG), an advocacy organization, have endeavored to support the implementation of global best practices in the care of people living with sickle cell disease (SCD) in Africa, and to address unmet needs relating to this condition on the continent. Beginning in 2019, a multifaceted SCD program was implemented in Ghana through a public-private partnership involving the government of Ghana, the SCFG, Novartis, and other partners. A key component of the program involved expanding the reach of hydroxyurea (HU), the only approved disease-modifying generic treatment for SCD, in ways that would promote sustainable access. The program helped to raise the profile of SCD in Ghana and, in 2022, the government adopted HU into its National Health Insurance Scheme. Features of the effort in Ghana are now being expanded to other countries in Africa through cocreated programs with in-country partners. This article reviews the program's history, progress, challenges, and lessons learned.

White-matter abnormalities and cognitive dysfunction are linked to astrocyte activation in sickle mice.

White-matter injury in sickle-cell disease (SCD) includes silent cerebral infarction diagnosed by diffusion tensor imaging (DTI), a complication associated with cognitive dysfunction in children with SCD. The link between white-matter injury and cognitive dysfunction has not been fully elucidated. The goal of this study was to define whether cerebrovascular lesions and cognitive function in SCD are linked to neuroaxonal damage and astrocyte activation in humanized Townes' SCD mice homozygous for human sickle hemoglobin S (SS) and control mice homozygous for human normal hemoglobin A (AA). Mice underwent MRI with DTI and cognitive testing, and histology sections from their brains were stained to assess microstructural tissue damage, neuroaxonal damage, and astrocyte activation. Fractional anisotropy, showing microstructural cerebrovascular abnormalities identified by DTI in the white matter, was significantly associated with neuronal demyelination in the SS mouse brain. SS mice had reduced learning and memory function with a significantly lower discrimination index compared with AA control mice in the novel object recognition tests. Neuroaxonal damage in the SS mice was synchronously correlated with impaired neurocognitive function and activation of astrocytes. The interplay between astrocyte function and neurons may modulate cognitive performance in SCD.

Insulin-like Growth Factor-1 Prevents Hypoxia/Reoxygenation-Induced White Matter Injury in Sickle Cell Mice.

Occlusion of cerebral blood vessels causes acute cerebral hypoxia-an important trigger of ischemic white matter injury and stroke in sickle cell disease (SCD). While chronic hypoxia triggers compensatory neuroprotection via insulin-like growth factor-1 (IGF-1) and hypoxia inducible factor-1α (HIF-1α), severe bouts of acute hypoxia and subsequent restoration of blood flow (hypoxia/reoxygenation, H/R) overwhelm compensatory mechanisms and cause neuroaxonal damage-identified as white matter lesions-in the brain. The neuroprotective role of IGF-1 in the pathogenesis of white matter injury in SCD has not been investigated; however, it is known that systemic IGF-1 is reduced in individuals with SCD. We hypothesized that IGF-1 supplementation may prevent H/R-induced white matter injury in SCD. Transgenic sickle mice homozygous for human hemoglobin S and exposed to H/R developed white matter injury identified by elevated expression of non-phosphorylated neurofilament H (SMI32) with a concomitant decrease in myelin basic protein (MBP) resulting in an increased SMI32/MBP ratio. H/R-challenge also lowered plasma and brain IGF-1 expression. Human recombinant IGF-1 prophylaxis significantly induced HIF-1α and averted H/R-induced white matter injury in the sickle mice compared to vehicle-treated mice. The expression of the IGF-1 binding proteins IGFBP-1 and IGFBP-3 was elevated in the IGF-1-treated brain tissue indicating their potential role in mediating neuroprotective HIF-1α signaling. This study provides proof-of-concept for IGF-1-mediated neuroprotection in SCD.

The BLOODSAFE program: Building the future of access to safe blood in Sub-Saharan Africa.

BACKGROUND: The supply of blood in many low- and middle-income nations in Sub-Saharan Africa (SSA) does not meet the patient care needs. Lack and delay of blood transfusion cause harm to patients and slow the rate of progress in other parts of the health system. Recognizing the power of implementation science, the BLOODSAFE Program was initiated which supports three SSA research study teams and one data coordinating center (DCC) with the goal to improve access to safe blood transfusion in SSA. STUDY DESIGN AND METHODS: The study team in Ghana is focusing on studying and decreasing iron deficiency in blood donors and evaluating social engagement of blood donors through different approaches. The study team in Kenya is building a "vein to vein" workflow model to elucidate and devise strategies to overcome barriers to blood donation and improve infrastructural components of blood product production and use. The Malawi team is studying the infectious disease ramifications of blood donation as well as blood donor retention strategies aimed at blood donors who commence their donation career in secondary schools. RESULTS AND DISCUSSION: Together the project teams and the DCC work as a consortium to support each other through a shared study protocol that will study donor motivations, outcomes, and adverse events across all three countries. The BLOODSAFE Program has the potential to lead to generalizable improvement approaches for increasing access to safe blood in SSA as well as mentoring and building the research capacity and careers of many investigators.

Hydroxyurea Decouples Persistent F-Cell Elevation and Induction of γ-Globin.

Mechanisms that control the fetal-to-adult hemoglobin switch are attractive therapeutic targets in sickle cell disease. In this study, we investigated developmental γ-globin silencing in the Townes humanized knock-in mouse model, which harbors a construct containing the human γ-, ßA-, and ßS-globin genes, and examined the utility of this model in evaluation of pharmacologic induction of fetal hemoglobin (HbF). We studied mouse pups on the day of delivery (P0) to 28 days after birth (P28). Regardless of the hemoglobin genotype (SS, AS, or AA), the proportion of F cells in peripheral blood was 100% at P0, declined sharply to 20% at P2, and was virtually undetectable at P14. Developmental γ-globin silencing in Townes mice was complete at P4 in association with significantly increased BCL11A expression in the primary erythropoietic organs of the mouse. Hydroxyurea given at P2 significantly sustained elevated percentages of F cells in mice at P14. However, the percentage of F cells declined at P14 for treatment begun at P4. A lack of augmentation of γ-globin mRNA in erythroid tissues suggests that the apparent increase in HbF in red cells caused by hydroxyurea was not due to sustained or re-activation of γ-globin transcription, but was instead a function of erythropoiesis suppression. Thus, we provide new details of the hemoglobin switch in the Townes murine model that recapitulates postnatal γ- to ß-globin switch in humans and identify the myelosuppressive toxicity of hydroxyurea as a superseding factor in interpreting pharmacologic induction of HbF.

Immunomodulatory actions of a kynurenine-derived endogenous electrophile.

The up-regulation of kynurenine metabolism induces immunomodulatory responses via incompletely understood mechanisms. We report that increases in cellular and systemic kynurenine levels yield the electrophilic derivative kynurenine-carboxyketoalkene (Kyn-CKA), as evidenced by the accumulation of thiol conjugates and saturated metabolites. Kyn-CKA induces NFE2 like bZIP transcription factor 2- and aryl hydrocarbon receptor-regulated genes and inhibits nuclear factor κB- and NLR family pyrin domain containing 3-dependent proinflammatory signaling. Sickle cell disease (SCD) is a hereditary hemolytic condition characterized by basal inflammation and recurrent vaso-occlusive crises. Both transgenic SCD mice and patients with SCD exhibit increased kynurenine and Kyn-CKA metabolite levels. Plasma hemin and kynurenine concentrations are positively correlated, indicating that Kyn-CKA synthesis in SCD is up-regulated during pathogenic vascular stress. Administration of Kyn-CKA abrogated pulmonary microvasculature occlusion in SCD mice, an important factor in lung injury development. These findings demonstrate that the up-regulation of kynurenine synthesis and its metabolism to Kyn-CKA is an adaptive response that attenuates inflammation and protects tissues.

Nrf2 Activation With CDDO-Methyl Promotes Beneficial and Deleterious Clinical Effects in Transgenic Mice With Sickle Cell Anemia.

Activation of Nrf2, a major transcription factor that drives the antioxidant defense system, is an emerging therapeutic strategy in Sickle Cell Disease (SCD). In this study, transgenic Sickle Cell Anemia mice (SS mice) treated with CDDO-Methyl (CDDO-Me), a potent Nrf2 activator, showed reduced progression of hemolytic anemia with aging, but surprisingly also showed reduced endothelial function. Pulmonary vessels isolated from SS mice treated for 4 months with CDDO-Me displayed a diminished response to nitric oxide (NO)-induced vasodilation compared to littermates given vehicle. It is unclear what molecular mechanism underly the vascular impairment, however, our in vitro assays revealed that CDDO-Me induced the expression of the endothelin receptor (ETA and ETB) in vascular smooth muscle cells. Endothelin signaling is associated with increased vascular tone and vasoconstriction. This study underscores the importance of pre-clinical benefit-risk investigations of Nrf2 activating compounds which may be used to treat patients with SCD.

Sickle Cell Disease Genomics of Africa (SickleGenAfrica) Network: ethical framework and initial qualitative findings from community engagement in Ghana, Nigeria and Tanzania.

OBJECTIVES: To provide lay information about genetics and sickle cell disease (SCD) and to identify and address ethical issues concerning the Sickle Cell Disease Genomics of Africa Network covering autonomy and research decision-making, risk of SCD complications and organ damage, returning of genomic findings, biorepository, data sharing, and healthcare provision for patients with SCD. DESIGN: Focus groups using qualitative methods. SETTING: Six cities in Ghana, Nigeria and Tanzania within communities and secondary care. PARTICIPANTS: Patients, parents/caregivers, healthcare professionals, community leaders and government healthcare representatives. RESULTS: Results from 112 participants revealed similar sensitivities and aspirations around genomic research, an inclination towards autonomous decision-making for research, concerns about biobanking, anonymity in data sharing, and a preference for receiving individual genomic results. Furthermore, inadequate healthcare for patients with SCD was emphasised. CONCLUSIONS: Our findings revealed the eagerness of patients and parents/caregivers to participate in genomics research in Africa, with advice from community leaders and reassurance from health professionals and policy-makers, despite their apprehensions regarding healthcare systems.

Xanthine Oxidase Drives Hemolysis and Vascular Malfunction in Sickle Cell Disease.

OBJECTIVE: Chronic hemolysis is a hallmark of sickle cell disease (SCD) and a driver of vasculopathy; however, the mechanisms contributing to hemolysis remain incompletely understood. Although XO (xanthine oxidase) activity has been shown to be elevated in SCD, its role remains unknown. XO binds endothelium and generates oxidants as a byproduct of hypoxanthine and xanthine catabolism. We hypothesized that XO inhibition decreases oxidant production leading to less hemolysis. Approach and Results: Wild-type mice were bone marrow transplanted with control (AA) or sickle (SS) Townes bone marrow. After 12 weeks, mice were treated with 10 mg/kg per day of febuxostat (Uloric), Food and Drug Administration-approved XO inhibitor, for 10 weeks. Hematologic analysis demonstrated increased hematocrit, cellular hemoglobin, and red blood cells, with no change in reticulocyte percentage. Significant decreases in cell-free hemoglobin and increases in haptoglobin suggest XO inhibition decreased hemolysis. Myographic studies demonstrated improved pulmonary vascular dilation and blunted constriction, indicating improved pulmonary vasoreactivity, whereas pulmonary pressure and cardiac function were unaffected. The role of hepatic XO in SCD was evaluated by bone marrow transplanting hepatocyte-specific XO knockout mice with SS Townes bone marrow. However, hepatocyte-specific XO knockout, which results in >50% diminution in circulating XO, did not affect hemolysis levels or vascular function, suggesting hepatocyte-derived elevation of circulating XO is not the driver of hemolysis in SCD. CONCLUSIONS: Ten weeks of febuxostat treatment significantly decreased hemolysis and improved pulmonary vasoreactivity in a mouse model of SCD. Although hepatic XO accounts for >50% of circulating XO, it is not the source of XO driving hemolysis in SCD.

Heme Induces IL-6 and Cardiac Hypertrophy Genes Transcripts in Sickle Cell Mice.

Emerging data indicate that free heme promotes inflammation in many different disease settings, including in sickle cell disease (SCD). Although free heme, proinflammatory cytokines, and cardiac hypertrophy are co-existing features of SCD, no mechanistic links between these features have been demonstrated. We now report significantly higher levels of IL-6 mRNA and protein in hearts of the Townes sickle cell disease (SS) mice (2.9-fold, p ≤ 0.05) than control mice expressing normal human hemoglobin (AA). We find that experimental administration of heme 50 µmoles/kg body weight induces IL-6 expression directly in vivo and induces gene expression markers of cardiac hypertrophy in SS mice. We administered heme intravenously and found that within three hours plasma IL-6 protein significantly increased in SS mice compared to AA mice (3248 ± 275 vs. 2384 ± 255 pg/ml, p ≤ 0.05). In the heart, heme induced a 15-fold increase in IL-6 transcript in SS mice heart compared to controls. Heme simultaneously induced other markers of cardiac stress and hypertrophy, including atrial natriuretic factor (Nppa; 14-fold, p ≤ 0.05) and beta myosin heavy chain (Myh7; 8-fold, p ≤ 0.05) in SS mice. Our experiments in Nrf2-deficient mice indicate that the cardiac IL-6 response to heme does not require Nrf2, the usual mediator of transcriptional response to heme for heme detoxification by heme oxygenase-1. These data are the first to show heme-induced IL-6 expression in vivo, suggesting that hemolysis may play a role in the elevated IL-6 and cardiac hypertrophy seen in patients and mice with SCD. Our results align with published evidence from rodents and humans without SCD that suggest a causal relationship between IL-6 and cardiac hypertrophy.

Sickle cell disease as a vascular disorder.

INTRODUCTION: In sickle cell disease (SCD), hemoglobin S (HbS) red blood cells (RBCs) are characteristically deformed and inflexible. Often breaking down in the circulation, they exhibit increased adhesive properties with the endothelium and activated neutrophils and platelets, increasing the risk of occlusion of the microcirculation. SCD is categorized into two sub-phenotypes: hyperhemolytic, associated with priapism, leg ulcers, pulmonary hypertension, and stroke, and high hemoglobin/viscosity, which may promote vaso-occlusion-associated pain, acute chest syndrome, and osteonecrosis. AREAS COVERED: The sub-phenotypes are not completely distinct. Hemolysis may trigger vaso-occlusion, contributing to vascular complications. Targeting P-selectin, a key mediator of cross-talk between hyperhemolysis and vaso-occlusion, may be beneficial for vascular and vaso-occlusion-associated complications. English-language articles from PubMed on the topic of SCD and vaso-occlusive crises (VOCs) were reviewed from 1 January 2000 to 1 January 2019 using the search terms 'sickle cell disease,' 'vaso-occlusive crises,' and 'selectin.' EXPERT OPINION: Besides targeting P-selectin, other strategies to counter VOCs and RBC sickling are being pursued. These include platelet inhibition to counter aggregation, intercellular adhesion, and thrombosis during VOCs; gene therapy to correct the homozygous missense mutation in the ß-globin gene, causing polymerization of HbS; L-glutamine, possibly reducing oxidative stress in sickled RBCs; and fetal hemoglobin inducers.

Nrf2 deficiency in mice attenuates erythropoietic stress-related macrophage hypercellularity.

Erythropoiesis in the bone marrow and spleen depends on intricate interactions between the resident macrophages and erythroblasts. Our study focuses on identifying the role of nuclear factor erythroid 2-related factor 2 (Nrf2) during recovery from stress erythropoiesis. To that end, we induced stress erythropoiesis in Nrf2+/+ and Nrf2-null mice and evaluated macrophage subsets known to support erythropoiesis and erythroid cell populations. Our results confirm macrophage and erythroid hypercellularity after acute blood loss. Importantly, Nrf2 depletion results in a marked numerical reduction of F4/80+/CD169+/CD11b+ macrophages, which is more prominent under the induction of stress erythropoiesis. The observed macrophage deficiency is concomitant to a significantly impaired erythroid response to acute stress erythropoiesis in both murine bone marrow and murine spleen. Additionally, peripheral blood reticulocyte count as a response to acute blood loss is delayed in Nrf2-deficient mice compared with age-matched controls (11.0 ± 0.6% vs. 14.8 ± 0.6%, p ≤ 0.001). Interestingly, we observe macrophage hypercellularity in conjunction with erythroid hyperplasia in the bone marrow during stress erythropoiesis in Nrf2+/+ controls, with both impaired in Nrf2-/- mice. We further confirm the finding of macrophage hypercellularity in another model of erythroid hyperplasia, the transgenic sickle cell mouse, characterized by hemolytic anemia and chronic stress erythropoiesis. Our results revealed the role of Nrf2 in stress erythropoiesis in the bone marrow and that macrophage hypercellularity occurs concurrently with erythroid expansion during stress erythropoiesis. Macrophage hypercellularity is a previously underappreciated feature of stress erythropoiesis in sickle cell disease and recovery from blood loss.

Hemopexin deficiency promotes acute kidney injury in sickle cell disease.

Acute kidney injury (AKI) is a major clinical concern in sickle cell disease (SCD). Clinical evidence suggests that red cell alarmins may cause AKI in SCD, however, the sterile inflammatory process involved has hitherto not been defined. We discovered that hemopexin deficiency in SCD is associated with a compensatory increase in α-1-microglobulin (A1M), resulting in an up to 10-fold higher A1M-to-hemopexin ratio in SCD compared with healthy controls. The A1M-to-hemopexin ratio is associated with markers of hemolysis and AKI in both humans and mice with SCD. Studies in mice showed that excess heme is directed to the kidneys in SCD in a process involving A1M causing AKI, whereas excess heme in controls is transported to the liver as expected. Using genetic and bone marrow chimeric tools, we confirmed that hemopexin deficiency promotes AKI in sickle mice under hemolytic stress. However, AKI was blocked when hemopexin deficiency in sickle mice was corrected with infusions of purified hemopexin prior to the induction of hemolytic stress. This study identifies acquired hemopexin deficiency as a risk factor of AKI in SCD and hemopexin replacement as a potential therapy.

Smooth muscle cytochrome b5 reductase 3 deficiency accelerates pulmonary hypertension development in sickle cell mice.

Pulmonary and systemic vasculopathies are significant risk factors for early morbidity and death in patients with sickle cell disease (SCD). An underlying mechanism of SCD vasculopathy is vascular smooth muscle (VSM) nitric oxide (NO) resistance, which is mediated by NO scavenging reactions with plasma hemoglobin (Hb) and reactive oxygen species that can oxidize soluble guanylyl cyclase (sGC), the NO receptor. Prior studies show that cytochrome b5 reductase 3 (CYB5R3), known as methemoglobin reductase in erythrocytes, functions in VSM as an sGC heme iron reductase critical for reducing and sensitizing sGC to NO and generating cyclic guanosine monophosphate for vasodilation. Therefore, we hypothesized that VSM CYB5R3 deficiency accelerates development of pulmonary hypertension (PH) in SCD. Bone marrow transplant was used to create SCD chimeric mice with background smooth muscle cell (SMC)-specific tamoxifen-inducible Cyb5r3 knockout (SMC R3 KO) and wild-type (WT) control. Three weeks after completing tamoxifen treatment, we observed 60% knockdown of pulmonary arterial SMC CYB5R3, 5 to 6 mm Hg elevated right-ventricular (RV) maximum systolic pressure (RVmaxSP) and biventricular hypertrophy in SS chimeras with SMC R3 KO (SS/R3KD) relative to WT (SS/R3WT). RV contractility, heart rate, hematological parameters, and cell-free Hb were similar between groups. When identically generated SS/R3 chimeras were studied 12 weeks after completing tamoxifen treatment, RVmaxSP in SS/R3KD had not increased further, but RV hypertrophy relative to SS/R3WT persisted. These are the first studies to establish involvement of SMC CYB5R3 in SCD-associated development of PH, which can exist in mice by 5 weeks of SMC CYB5R3 protein deficiency.

Cardiac expression of HMOX1 and PGF in sickle cell mice and haem-treated wild type mice dominates organ expression profiles via Nrf2 (Nfe2l2).

Haemolysis is a major feature of sickle cell disease (SCD) that contributes to organ damage. It is well established that haem, a product of haemolysis, induces expression of the enzyme that degrades it, haem oxygenase-1 (HMOX1). We have also shown that haem induces expression of placental growth factor (PGF), but the organ specificity of these responses has not been well-defined. As expected, we found high level expression of Hmox1 and Pgf transcripts in the reticuloendothelial system organs of transgenic sickle cell mice, but surprisingly strong expression in the heart (P < 0·0001). This pattern was largely replicated in wild type mice by intravenous injection of exogenous haem. In the heart, haem induced unexpectedly strong mRNA responses for Hmox1 (18-fold), Pgf (4-fold), and the haem transporter Slc48a1 (also termed Hrg1; 2·4-fold). This was comparable to the liver, the principal known haem-detoxifying organ. The NFE2L2 (also termed NRF2) transcription factor mediated much of the haem induction of Hmox1 and Hrg1 in all organs, but less so for Pgf. Our results indicate that the heart expresses haem response pathway genes at surprisingly high basal levels and shares with the liver a similar transcriptional response to circulating haem. The role of the heart in haem response should be investigated further.