Sickle cell disease as a vascular disorder

Hydroxyurea Mitigates Heme-Induced Inflammation and Kidney Injury in Humanized Sickle Cell Mice

Kidney disorders significantly contribute to morbidity and mortality in sickle cell disease (SCD). Acute kidney injury (AKI), a major risk factor for chronic kidney disease (CKD), often arises from intravascular hemolysis, where plasma cell-free heme drives AKI through inflammatory and oxidative stress mechanisms. Hydroxyurea (HU), a well-established SCD-modifying therapy, improves clinical outcomes, but its effects on systemic heme and inflammatory mediators of kidney injury remain underexplored. This study evaluated HU's impact on plasma heme, pro-inflammatory mediators, kidney injury, and renal histopathology in a sickle cell mouse model. Townes humanized sickle cell mice (HbSS) and non-sickle (HbAA) controls were treated with HU or vehicle for two weeks. HU significantly reduced total plasma heme, lactate dehydrogenase, and pro-inflammatory cytokines (CXCL10, VEGF-A, IFN-γ) in HbSS mice. HU reduced renal injury biomarkers (cystatin C, NGAL) and improved renal histopathology, evidenced by reduced vascular congestion, glomerulosclerosis, and tubular damage. Interestingly, HU did not alter the levels of kidney repair biomarkers (clusterin and EGF). These findings suggest that HU mitigates kidney injury by reducing the deleterious effects of circulating heme and inflammation, supporting its potential to slow or prevent progressive kidney injury in SCD.

Musculoskeletal complications in sickle cell disease: Pathophysiology, diagnosis and management

Sickle cell disease (SCD) is a mono-genic disorder causing chronic hemolysis, anemia, and vaso-occlusion, leading to musculoskeletal complications such as osteonecrosis, osteoporosis, and bone fractures affecting 50-70% SCD patients. These complications result from a complex interplay of genetic and physiological factors, including abnormal hemoglobin production, chronic inflammation, and oxidative stress. This review discusses the pathophysiology, pre-clinical symptoms, and clinical manifestations of musculoskeletal complications in SCD, as well as current treatment options, including pharmacological interventions, surgical procedures, and bone marrow transplantation. Early detection of pre-clinical symptoms is crucial to prevent progression. Pharmacological interventions (analgesics, anti-inflammatory agents, bone-modifying agents and hydroxyurea), surgical interventions (core decompression, bone grafting, joint replacement and osteotomy) and supportive measures enhance mobility, strength and well-being. A multidisciplinary approach is essential for optimal care, and early diagnosis and management are crucial to prevent long-term damage and improve outcomes. Future research directions include targeted therapies, biomarker investigation and infrastructure development to improve outcomes for SCD individuals with musculoskeletal complications.

Platelet signaling in immune landscape: comprehensive mechanism and clinical therapy

Platelets are essential for blood clotting and maintaining normal hemostasis. In pathological conditions, platelets are increasingly recognized as crucial regulatory factors in various immune-mediated inflammatory diseases. Resting platelets are induced by various factors such as immune complexes through Fc receptors, platelet-targeting autoantibodies and other platelet-activating stimuli. Platelet activation in immunological processes involves the release of immune activation stimuli, antigen presentation and interaction with immune cells. Platelets participate in both the innate immune system (neutrophils, monocytes/macrophages, dendritic cells (DCs) and Natural Killer (NK) cells and the adaptive immune system (T and B cells). Clinical therapeutic strategies include targeting platelet activation, platelet-immune cell interaction and platelet-endothelial cell interaction, which display positive development prospects. Understanding the mechanisms of platelets in immunity is important, and developing targeted modulations of these mechanisms will pave the way for promising therapeutic strategies.

Haemoglobinopathies and other rare anemias in Spain: ten years of a nationwide registry (REHem-AR)

REHem-AR was created in 2013. The progressive implementation of neonatal screening for haemoglobinopathies in Spanish autonomous communities where the registry had not been implemented, as well as the addition of new centres during this period, has considerably increased the sample of patients covered. In this study, we update our previous publication in this area, after a follow-up of more than 5 years. An observational, descriptive, multicentre and ambispective study of adult and paediatric patients with haemoglobinopathies and rare anaemias registered in REHem was performed. The data are from a cross-sectional analysis performed on 1 June, 2023. The study population comprised 1,756 patients, of whom 1,317 had SCD, 214 had thalassaemia and 224 were diagnosed with another condition. Slightly more than one third of SCD patients (37%) were diagnosed based on neonatal bloodspot screening, and the mean age at diagnosis was 2.5 years; 71% of thalassaemia patients were diagnosed based on the presence of anaemia. Vaso-occlusive crisis and acute chest syndrome continue to be the most frequent complications in SCD. HSCT was performed in 83 patients with SCD and in 50 patients with thalassaemia. Since the previous publication, REHem-AR has grown in size by more than 500 cases. SCD and TM are less frequent in Spain than in other European countries, although the data show that rare anaemias are frequent within rare diseases. REHem-AR constitutes an important structure for following the natural history of rare anaemias and enables us to calculate investment needs for current and future treatments.

Stroke in sickle cell patients, epidemiology, pathophysiology, systemic and surgical treatment options and prevention strategies

Background

A hereditary haemoglobinopathy known as sickle cell disease (SCD) affects over 100 000 people in the United States severely. Cerebrovascular disease is a prominent consequence of SCD. By the age of 30, 53% of patients have silent cerebral infarcts (SCIs) (a stroke that occurs without any obvious symptoms because it damages a small part of the brain that isn't responsible for any essential functions), and by the age of 40, 3.8% have overt strokes.

Main body

The multidimensional burden of cerebrovascular illness in SCD is reviewed in detail in this article, which includes both clinical strokes and the frequently asymptomatic SCIs. The intricate pathophysiology of SCD and stroke is explored. With SCD, there are currently very few methods for preventing primary and secondary stroke; the most common ones are hydroxyurea and blood transfusion. Nevertheless, not enough research has been done on the possible contributions of anticoagulation and aspirin to strokes linked to SCD. Promising evidence is also highlighted in the study, suggesting that new drugs intended to treat SCD may be able to alleviate leg ulcers and renal impairment in addition to reducing unusually high transcranial Doppler flow velocity – a crucial component of cerebrovascular events. Given that these novel medications specifically target haemolysis and vaso‐occlusion, the two main causes of strokes in this population, more research is desperately needed to determine whether they are effective in avoiding strokes in people with SCD. The literature review also emphasizes how common healthcare inequities are and how they hinder advancements in SCD research and management in the United States.

Conclusion

To successfully address these inequities, the evaluation recommends more funding for both SCD management and research, as well as for patient and clinician education. This multimodal viewpoint highlights the intricate terrain of cerebrovascular problems associated with SCD and the urgent need for all‐encompassing and fair strategies to improve patient outcomes and advance research.

Nitric oxide: A potential etiological agent for vaso-occlusive crises in sickle cell disease

Nitric oxide (NO), a vasodilator contributes to the vaso-occlusive crisis associated with the sickle cell disease (SCD). Vascular nitric oxide helps in vasodilation, controlled platelet aggregation, and preventing adhesion of sickled red blood cells to the endothelium. It decreases the expression of pro-inflammatory genes responsible for atherogenesis associated with SCD. Haemolysis and activated endothelium in SCD patients reduce the bioavailability of NO which promotes the severity of sickle cell disease mainly causes vaso-occlusive crises. Additionally, NO depletion can also contribute to the formation of thrombus, which can cause serious complications such as stroke, pulmonary embolism etc. Understanding the multifaceted role of NO provides valuable insights into its therapeutic potential for managing SCD and preventing associated complications. Various clinical trials and studies suggested the importance of artificially induced nitric oxide and its supplements in the reduction of severity. Further research on the mechanisms of NO depletion in SCD is needed to develop more effective treatment strategies and improve the management of this debilitating disease.

Factors Associated with Leg Ulcers in Adults with Sickle Cell Disease in Brazil

OBJECTIVE

To define the prevalence of leg ulcers and identify the clinical and laboratory factors associated with leg ulcers in adult participants.

METHODS

The authors conducted a cross-sectional study of 1,109 patients who were 18 years or older with SS or Sβ0-thalassemia genotypes from a Brazilian cohort. Investigators assessed the prevalence of factors associated with leg ulcers from 2013 to 2017.

RESULTS

The prevalence of leg ulcers was 21%. Increasing age (odds ratio [OR], 1.07; range, 1.06-1.09), male sex (OR, 2.03; range, 1.44-2.87), treatment with chronic transfusion therapy (OR, 1.88; range, 1.15-3.03), higher indirect bilirubin levels (OR, 1.48; range, 1.02-2.16), and low hemoglobin levels (OR, 2.17; range, 1.52-3.11) were associated with leg ulcers. Participants who self-reported as Black (OR, 6.75; range, 2.63-21.32), mixed (OR, 3.91; range, 1.55-12.20), and other/unknown (OR, 3.84; range, 1.04-15.24) were more likely to have leg ulcers compared with those who self-reported as White.

CONCLUSIONS

The prevalence of leg ulcers in this Brazilian cohort was higher than the prevalence reported in developed countries. Known factors such as age and male sex were corroborated. The increased bilirubin level and decreased hemoglobin levels among participants with leg ulcers support the hypothesis that hemolysis is correlated with leg ulcer pathogenesis. Self-reported black skin color was an independent predictor of leg ulcers and warrants further study to understand the etiology and implications of this finding.

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.

Treatment dilemmas: strategies for priapism, chronic leg ulcer disease, and pulmonary hypertension in sickle cell disease

Sickle cell disease is a disorder characterized by chronic hemolytic anemia and multiorgan disease complications. Although vaso-occlusive episodes, acute chest syndrome, and neurovascular disease frequently result in complication and have well-documented guidelines for management, the management of chronic hemolytic and vascular-related complications, such as priapism, leg ulcers, and pulmonary hypertension, is not as well recognized despite their increasing reported prevalence and association with morbidity and mortality. This chapter therefore reviews the current updates on diagnosis and management of priapism, leg ulcers, and pulmonary hypertension.

Cell and Gene Therapy for Anemia: Hematopoietic Stem Cells and Gene Editing

Hereditary anemia has various manifestations, such as sickle cell disease (SCD), Fanconi anemia, glucose-6-phosphate dehydrogenase deficiency (G6PDD), and thalassemia. The available management strategies for these disorders are still unsatisfactory and do not eliminate the main causes. As genetic aberrations are the main causes of all forms of hereditary anemia, the optimal approach involves repairing the defective gene, possibly through the transplantation of normal hematopoietic stem cells (HSCs) from a normal matching donor or through gene therapy approaches (either in vivo or ex vivo) to correct the patient’s HSCs. To clearly illustrate the importance of cell and gene therapy in hereditary anemia, this paper provides a review of the genetic aberration, epidemiology, clinical features, current management, and cell and gene therapy endeavors related to SCD, thalassemia, Fanconi anemia, and G6PDD. Moreover, we expound the future research direction of HSC derivation from induced pluripotent stem cells (iPSCs), strategies to edit HSCs, gene therapy risk mitigation, and their clinical perspectives. In conclusion, gene-corrected hematopoietic stem cell transplantation has promising outcomes for SCD, Fanconi anemia, and thalassemia, and it may overcome the limitation of the source of allogenic bone marrow transplantation.