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- Editing an α-globin enhancer in primary human hematopoietic stem cells as a treatment for β-thalassemiaPublication . Mettananda, Sachith; Fisher, Chris A.; Hay, Deborah; Badat, Mohsin; Quek, Lynn; Clark, Kevin; Hublitz, Philip; Downes, Damien; Kerry, Jon; Gosden, Matthew; Telenius, Jelena; Sloane-Stanley, Jackie A.; Faustino, Paula; Coelho, Andreia; Doondeea, Jessica; Usukhbayar, Batchimeg; Sopp, Paul; Sharpe, Jacqueline A.; Hughes, Jim R.; Vyas, Paresh; Gibbons, Richard J.; Higgs, Douglas R.β-Thalassemia is one of the most common inherited anemias, with no effective cure for most patients. The pathophysiology reflects an imbalance between α- and β-globin chains with an excess of free α-globin chains causing ineffective erythropoiesis and hemolysis. When α-thalassemia is co-inherited with β-thalassemia, excess free α-globin chains are reduced significantly ameliorating the clinical severity. Here we demonstrate the use of CRISPR/Cas9 genome editing of primary human hematopoietic stem/progenitor (CD34+) cells to emulate a natural mutation, which deletes the MCS-R2 α-globin enhancer and causes α-thalassemia. When edited CD34+ cells are differentiated into erythroid cells, we observe the expected reduction in α-globin expression and a correction of the pathologic globin chain imbalance in cells from patients with β-thalassemia. Xenograft assays show that a proportion of the edited CD34+ cells are long-term repopulating hematopoietic stem cells, demonstrating the potential of this approach for translation into a therapy for β-thalassemia.
- Interaction between HFE and haptoglobin polymorphisms and its relation with plasma glutathione levels in obese childrenPublication . Aguiar, Laura; Marinho, Cláudia; Martins, Rute; Alho, Irina; Ferreira, Joana; Levy, Pilar Quinhones; Faustino, Paula; Bicho, Manuel; Inácio, AngelaObesity among children has emerged as a serious public health problem. The growing prevalence of childhood obesity has led to the appearance of serious complications, including a chronic systemic inflammation associated with oxidative stress. In the present study, we analysed the interaction between two genes related with iron metabolism - HFE and haptoglobin - and the plasmatic concentration of glutathione, as a way to evaluate the antioxidant response capacity in obesity. To achieve this, 118 obese children and 89 eutrophic children were recruited for the study. Results showed that although obese children present a significantly decreased tGSH levels, once we analysed separately children based on their haptoglobin phenotype, the decreased tGSH levels is significant only for the Hp 2 allele. Additionally, Hp 2.2 obese children carrying H63D polymorphism show significantly lower tGSH/GSSG values. Our results found an association of haptoglobin and HFE with oxidative stress in childhood obesity.
- Genetic modulators of fetal hemoglobin expression and ischemic stroke occurrence in African descendant children with sickle cell anemiaPublication . Nicolau, Marta; Vargas, Sofia; Silva, Marisa; Coelho, Andreia; Ferreira, Emanuel; Mendonça, Joana; Vieira, Luís; Kjöllerström, Paula; Maia, Raquel; Silva, Rita; Dias, Alexandra; Ferreira, Teresa; Morais, Anabela; Soares, Isabel Mota; Lavinha, João; Faustino, PaulaSickle cell anemia (SCA) is an autosomal recessive monogenic disease with significant clinical variability. Cerebrovascular disease, particularly ischemic stroke, is one of the most severe complications of SCA in children. This study aimed to investigate the influence of genetic variants on the levels of fetal hemoglobin (Hb F) and biochemical parameters related with chronic hemolysis, as well as on ischemic stroke risk, in ninety-one unrelated SCA patients, children of sub-Saharan progenitors. Our results show that a higher Hb F level has an inverse relationship with the occurrence of stroke, since the group of patients who suffered stroke presents a significantly lower mean Hb F level (5.34 ± 4.57% versus 9.36 ± 6.48%; p = 0.024). Furthermore, the co-inheritance of alpha-thalassemia improves the chronic hemolytic pattern, evidenced by a decreased reticulocyte count (8.61 ± 3.58% versus 12.85 ± 4.71%; p < 0.001). In addition, our findings have confirmed the importance of HBG2 and BCL11A loci in the regulation of Hb F expression in sub-Saharan African SCA patients, as rs7482144_A, rs11886868_C, and rs4671393_A alleles are significantly associated with a considerable increase in Hb F levels (p = 0.019, p = 0.026, and p = 0.028, respectively). Concerning KLF1, twelve different variants were identified, two of them novel. Seventy-three patients (80.2%) presented at least one variant in this gene. However, no correlation was observed between the presence of these variants and Hb F level, severity of hemolysis, or stroke occurrence, which is consistent with their in silico-predicted minor functional consequences. Thus, we conclude that the prevalence of functional KLF1 variants in a sub-Saharan African background does not seem to be relevant to SCA clinical modulation.
- VCAM1, HMOX1 and NOS3 differential endothelial expression may impact sickle cell anemia vasculopathyPublication . Silva, Marisa; Coelho, Andreia; Vargas, Sofia; Faustino, PaulaEndothelial dysfunction plays a major role in sickle cell anemia (SCA) systemic vasculopathy, with upregulation of adhesion molecules (e.g., VCAM-1), decreased nitric oxide bioavailability, and oxidative stress. We aimed to assess the modulation role of pro-inflammatory and pro-oxidative stimuli on endothelial VCAM1, NOS3, and HMOX1 expression. We also evaluated the effect of the main SCA therapeutic agent, hydroxyurea, on that modulation. Our results showed that two VCAM1 promoter haplotypes, we previously associated with pediatric cerebral vasculopathy and severe hemolysis in SCA, increased promoter activity in TNF-α-stimulated transfected EA.hy926 and HBEC cell lines, consistent with a higher VCAM1 expression in macro and microvascular settings. In non-transfected cells, we also observed TNF-α-induced VCAM1 overexpression as well as heme-induced overexpression of HMOX1 in both cell models. Heme did not affect VCAM1 nor NOS3 expression and the latter was also not affected by TNF-α stimulus. Hydroxyurea treatment lowered TNF-induced VCAM1 and NOS3 expression but did not affect heme-induced HMOX1 expression. These data further indicate that VCAM1 haplotypes we studied lead to higher VCAM1 expression affecting not only cerebral but also systemic vasculopathy risk. The differential endothelial expression of VCAM1, NOS3, and HMOX1 also confirms their genetic modulation role in SCA systemic vasculopathy.
- Biomarkers and genetic modulators of cerebral vasculopathy in sub-Saharan ancestry children with sickle cell anemiaPublication . Silva, Marisa; Vargas, Sofia; Coelho, Andreia; Ferreira, Emanuel; Mendonça, Joana; Vieira, Luís; Maia, Raquel; Dias, Alexandra; Ferreira, Teresa; Morais, Anabela; Soares, Isabel Mota; Lavinha, João; Silva, Rita; Kjöllerström, Paula; Faustino, PaulaWe investigated biomarkers and genetic modulators of the cerebral vasculopathy (CV) subphenotype in pediatric sickle cell anemia (SCA) patients of sub-Saharan African ancestry. We found that one VCAM1 promoter haplotype (haplotype 7) and VCAM1 single nucleotide variant rs1409419_T were associated with stroke events, stroke risk, as measured by time-averaged mean of maximum velocity in the middle cerebral artery, and with high serum levels of the hemolysis biomarker lactate dehydrogenase. Furthermore, VCAM-1 ligand coding gene ITGA4 variants rs113276800_A and rs3770138_T showed a positive association with stroke events. An additional positive relationship between a genetic variant and stroke risk was observed for ENPP1 rs1044498_A. Conversely, NOS3 variants were negatively associated with silent cerebral infarct events (VNTR 4b_allele and haplotype V) and CV globally (haplotype VII). The -alpha3.7kb–thal deletion did not show association with CV. However, it was associated with higher red blood cell and neutrophil counts, and lower mean corpuscular volume, mean corpuscular hemoglobin and red cell distribution width. Our results underline the importance of genetic modulators of the CV sub-phenotype and their potential as SCA therapeutic targets. We also propose that a biomarker panel comprising biochemical, hematological, imaging and genetic data would be instrumental for CV prediction, and prevention.
- Characterization of a cohort of Angolan children with sickle cell anemia treated with hydroxyureaPublication . Santos, Brígida; Ginete, Catarina; Gonçalves, Elisângela; Delgadinho, Mariana; Miranda, Armandina; Faustino, Paula; Arez, Ana Paula; Brito, MiguelBackground: Sickle Cell Anemia (SCA) is a monogenic disease, although its severity and response to treatment are very heterogeneous. Objectives: This study aims to characterize a cohort of Angolan children with SCA and evaluate their response to hydroxyurea (HU) treatment and the potential side effects and toxicity. Methods: The study enrolled 215 patients between 3 and 12 years old before and after the administration of HU, at a fix dose of 20 mg/kg/day for 12 months. Results: A total of 157 patients started HU medication and 141 of them completed the 12-month treatment. After initiating HU treatment, the frequency of clinical events decreased (transfusions 53.4 %, hospitalizations 47.1 %). The response to HU medication varied among patients, with some experiencing an increase in fetal hemoglobin (HbF) of <5 %. The mean increase in HbF was 11.9 %, ranging from 1.8 % to 31 %. Responders to HU treatment were 57 %, inadequate responders 38.7 % and non-adherent 4.2 %. No clinical side effects related to HU were reported. Hematological toxicities were transient and reversible. Children naïve to HU and with lower HbF reported higher number of hospitalizations caused by malaria infection. During HU treatment, the frequency of malaria episodes did not appear to be affected by HbF levels. Conclusions: the present study provided a valuable contribution to the understanding of the clinical and laboratory profiles of Angolan children with SCA. These findings support the evidence that the implementation of prophylactic measures and treatment with HU is associated with increased survival in children with SCA.
- Genetic modulation of anemia severity, hemolysis level, and hospitalization rate in Angolan children with sickle cell anemiaPublication . Germano, Isabel; Santos, Brígida; Delgadinho, Mariana; Ginete, Catarina; Lopes, Pedro; Arez, Ana Paula; Brito, Miguel; Faustino, PaulaBackground: Sickle Cell Anemia (SCA) is a genetic disease caused by the c.20 A > T mutation in HBB gene, generally characterized by sickle erythrocytes, chronic hemolytic anemia, and vaso-occlusive events. This study aimed to investigate genetic modulators of anemia severity, chronic hemolytic rate, and clinical manifestations in pediatric SCA patients from Angola, where the disease is a severe public health problem. Methods and results: The study was conducted on 200 SCA children living in Luanda or Caxito province. Their clinical phenotype was collected from patients' hospital records. Hematological and biochemical phenotypes were characterized in steady state condition. Twelve polymorphic regions in VCAM1, CD36 and NOS3 genes were genotyped using PCR, RFLP, and Sanger sequencing. CD36 gene promoter variants showed a significant impact on anemia severity. Particularly, the rs1413661_C allele was associated with lower hemoglobin levels, and increased number of hospitalizations and transfusions. This is the first report associating this SNP with SCA phenotypic heterogeneity. Moreover, the rs1041163_C allele in VCAM1 was associated with lower LDH levels; inversely the rs2070744_C allele in NOS3 was related with higher LDH levels and number of hospitalizations, being a risk factor for increased hemolytic rate. Conclusion: This study highlights, for the first time in the Angolan population, the importance of the genetic modifiers of vascular cell adhesion and nitric oxide metabolism in SCA pediatric phenotypic variability.
- Co-Inheritance of alpha-thalassemia and sickle cell disease in a cohort of Angolan pediatric patientsPublication . Santos, Brígida; Delgadinho, Mariana; Ferreira, Joana; Germano, Isabel; Miranda, Armandina; Arez, Ana Paula; Faustino, Paula; Brito, MiguelThe aim of this study was to explore the association between alpha-thalassemia, fetal hemoglobin, hematological indices, and clinical adverse events in Angolan sickle cell disease pediatric patients. A total of 200 sickle cell disease (SCD) children were sampled in Luanda and Caxito. A venous blood sample was collected and used for hematological analyses, fetal hemoglobin quantifcation, and genotyping of 3.7 kb alpha-thalassemia deletion by GAP-PCR. The frequency of the 3.7 kb alpha-thalassemia deletion in homozygosity was 12.5% and in heterozygosity was 55.0%. An increase in alpha-thalassemia frequency was observed in children older than 5 years old (11.7% vs. 13.00%). Furthermore, 3.7 kb alpha-thalassemia deletion homozygotes had a signifcantly higher age of the frst manifestation, lower number of blood transfusions by year, higher hemoglobin, lower mean corpuscular volume, mean corpuscular hemoglobin, and lower hemolytic rate observed by a lower number of reticulocytes count. There were no diferences in fetal hemoglobin between the three genotypes. Moreover, the number of stroke events, osteomyelitis, splenomegaly, splenectomy, and hepatomegaly were lower when alpha-thalassemia was co-inherited. For the frst time in Angolan population, the efect of alpha-thalassemia deletion in sickle cell disease was analyzed and results reinforce that this trait infuences the hematological and clinical aspects and produces a milder phenotype.