scholarly journals IMR-261, a Novel Oral Nrf2 Activator, Induces Fetal Hemoglobin in Human Erythroblasts, Reduces VOCs, and Ameliorates Ineffective Erythropoiesis in Experimental Mouse Models of Sickle Cell Disease and Beta-Thalassemia

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 853-853
Author(s):  
Thiago Trovati Maciel ◽  
Caroline Carvalho ◽  
Rachel Rignault ◽  
Biree Andemariam ◽  
Betty S. Pace ◽  
...  
Keyword(s):  
Research Funding ◽  
Fetal Hemoglobin ◽  
Fold Change ◽  
Beta Thalassemia ◽  
Human Monocytes ◽  
Ineffective Erythropoiesis ◽  
Antioxidant Genes ◽  
F Cells ◽  
Hbf Induction

Abstract Background Sickle cell disease (SCD) is an autosomal recessive disorder where mutated hemoglobin (HbS) polymerizes and can lead to irreversible red blood cell (RBC) sickling and painful vaso-occlusive crisis (VOC). The RBC sickling is amplified by inflammation, resulting in tissue and organ damage. The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) coordinates the expression of antioxidant genes in response to oxidative stress, regulates inflammation, inhibits the NFkB pathway, and induces fetal hemoglobin (HbF), making it an attractive target in SCD and beta-thalassemia. IMR-261 is a novel oral activator of Nrf2 and has been tested in Phase 2 clinical trials (previously as CXA-10). Methods & Results CD14+ human monocytes were exposed to IMR-261 at 3µM and 10µM for 3 hours, to determine via quantitative PCR (qPCR) its ability to induce expression of antioxidant genes. IMR-261 at 10 µM significantly increased (p<0.05) the expression of Nrf2-dependent genes (p<0.05), including HMOX1, HSPA1A, HSP90, GCLM, SOD1 and TXNRD1. Human monocytes were treated with lipopolysaccharide (LPS) to test the ability of IMR-261 to block inflammatory genes with a NFkB target dataset. IMR-261 significantly inhibited (p<0.05) LPS-induced expression of IL-1-beta, TNF-alpha and IL-6 in human monocytes. To test the effects of IMR-261 on HbF induction, human erythroblasts were derived from CD34+ blood marrow progenitor cells sourced from healthy or SCD subjects. IMR-261 induced expression of the gamma-globin gene (4.0-fold change at 3µM and 7.18-fold change at 6 µM). This was accompanied by increased %F-cells (2.8-fold change at 3µM and 3.0-fold change at 6 µM). IMR-261 was also tested in the Townes HbSS mouse model of SCD to assess the potential for HbF induction. Mice were dosed with IMR-261 at 12.5 mg/kg or 37.5 mg/kg BID for 4 weeks (N=4-8/group). After 4 weeks of treatment, IMR-261 at 12.5 mg/kg and 37.5 mg/kg resulted in a significant increase in HbF relative to control, and 37.5 mg/kg resulted in a significant increase in %F-cells relative to control (Table 1, p<0.05). In addition, both doses of IMR-261 led to significant increases in RBC counts and total hemoglobin (Hb) (Table 1, p<0.05). IMR-261 at 37.5 mg/kg also significantly decreased (p<0.05) both reticulocyte counts and spleen cellularity. The ability of IMR-261 to reduce VOCs was assessed in separate Townes HbSS mice after the administration of TNF-alpha (0.5 µg/mice i.p.). IMR-261 was dosed at 37.5 mg/kg BID for 5 days before triggering VOCs. RBCs were stained with Ter-119 antibodies on spleen and liver of mice. Compared to controls, IMR-261 significantly reduced the presence of RBC on occluded vessels. This was coupled with a reduction of P-selectin (3109±97 Mean Fluorescence Units [MFI] in vehicle-treated vs. 1974±379 MFI in IMR-261 group, p<0.05) and L-selectin (375±20 MFI in vehicle-treated vs. 242±60 MFI in IMR-261 group, p<0.05). IMR-261 also reduced select hemolysis biomarkers: bilirubin (11.2±0.3 mg/dL in vehicle-treated vs. 8.4±0.7 mg/dL in IMR-261 group, (p<0.05) and free-heme (325±52 µM in vehicle-treated vs. 203±51 µM in IMR-261 group, p<0.05). A beta-thalassemia experimental model Hbb th1/th1 was tested to evaluate whether IMR-261 could improve ineffective erythropoiesis seen in beta-thalassemia. IMR-261 treatment at 37.5 mg/kg BID significantly increased hemoglobin levels, RBC counts and hematocrit (p<0.05), with significant reductions observed in reticulocytes (p<0.05). flow cytometry analysis (CD71/Ter119) showed that IMR-261 significantly decreased late basophilic and polychromatic erythroblasts (Ery.B) and increased orthochromatic erythroblasts and reticulocytes (Ery.C) cell numbers in the spleen (p<0.05). Conclusions IMR-261 activates Nrf2-dependent antioxidant genes and inhibits NFkB-induced pro-inflammatory genes in human monocytes. In human erythroblasts, IMR-261 significantly increased HbF and %F-cells. In vivo SCD models show that IMR-261 significantly induced HbF and %F-cells, improved hemolytic markers, and decreased VOCs. IMR-261 also increased Hb and improved ineffective erythropoiesis in a beta-thalassemia in-vivo model. Together these data suggest that IMR-261 is a promising, novel, oral therapy that warrants clinical testing in SCD and beta-thalassemia. Figure 1 Figure 1. Disclosures Maciel: Imara Inc.: Research Funding. Carvalho: Imara Inc.: Research Funding. Rignault: Imara Inc.: Research Funding. Pace: Imara Inc.: Consultancy. OCain: Imara Inc.: Current Employment, Current equity holder in publicly-traded company. Ballal: Imara Inc.: Current Employment, Current equity holder in publicly-traded company.

scholarly journals Fetal Hemoglobin Rescues Ineffective Erythropoiesis in Sickle Cell Disease

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 14-15
Author(s):  
Sara El Hoss ◽  
Sylvie Cochet ◽  
Auria Godard ◽  
Hongxia Yan ◽  
Michaël Dussiot ◽  
...  
Keyword(s):  
Cell Death ◽  
Fetal Hemoglobin ◽  
Erythroid Differentiation ◽  
Ineffective Erythropoiesis ◽  
Hypoxic Conditions ◽  
Cd34 Cells ◽  
F Cells

Sickle cell disease (SCD) is an autosomal hereditary recessive disorder caused by a point mutation in the β globin gene resulting in a Glu-to-Val substitution at the 6th position of the β globin protein. The resulting abnormal hemoglobin (HbS) polymerizes under hypoxic conditions driving red blood cell (RBC) sickling (Pauling et al., 1949). While pathobiology of circulating RBCs has been extensively analyzed in SCD, erythropoiesis is surprisingly poorly documented. In β-thalassemia, ineffective erythropoiesis is characterized by high levels of apoptotic erythroblasts during the late stages of terminal differentiation, due to an accumulation of free β-globin chains (Arlet et al., 2016). Ineffective erythropoiesis is the major cause of anemia in β-thalassemia patients. In contrast, a marked decrease in life span of circulating red cells, a feature of sickle red cells, is considered to be the major determinant of chronic anemia in SCD. It is generally surmised that ineffective erythropoiesis contributes little to anemia. The bone marrow environment has been well documented to be hypoxic (0.1 to 6% O2) (Mantel et al., 2015). As hypoxia induces HbS polymerization, we hypothesized that cell death may occur in vivo because of HbS polymer formation in the late stages of differentiation characterized by high intracellular hemoglobin concentration. In the present study, using both in vitro and in vivo derived human erythroblasts we assessed the extent of ineffective erythropoiesis in SCD. We explored the mechanistic basis of the ineffective erythropoiesis in SCD using biochemical, cellular and imaging techniques. In vitro erythroid differentiation using CD34+ cells isolated from SCD patients and from healthy donors was performed. A 2-phase erythroid differentiation protocol was used and cultures were performed at two different oxygen conditions, i.e. normoxia and partial hypoxia (5% O2). We found that hypoxia induces cell death of sickle erythroblasts starting at the polychromatic stage, positively selecting cells with high levels of fetal hemoglobin (HbF). This inference was supported by flow cytometry data showing higher percentages of dead cells within the non-F-cell population as compared to the F-cell population for SCD cells. Moreover, SCD dead cells showed higher levels of chaperon protein HSP70 in the cytoplasm than live cells, while no difference was detected between both subpopulations for control cells, suggesting that cell death of SCD erythroblasts was probably due to HSP70 cytoplasmic sequestration. This was supported by western-blot experiments showing less HSP70 in the nucleus of SCD erythroblasts under hypoxia, associated with decreased levels of GATA-1. At the molecular level, HSP70 was co-immunoprecipitated with HbS under hypoxia indicating that both proteins were in the same complex and suggesting interaction between HSP70 and HbS polymers in the cyotplasm. Importantly, we confirm these results in vivo by showing that in bone marrow of SCD patients (n = 5) cell loss occurs during terminal erythroid differentiation, with a significant drop in the cell count between the polychromatic and the orthochromatic stages (Figure 1). In order to specifically address the role of HbF in cell survival, we used a CRISPR-Cas9 approach to mimic the effect of hereditary persistence of fetal hemoglobin (HPFH). CD34+ cells were transfected either with a gRNA targeting the LRF binding site (-197) or a gRNA targeting an unrelated locus (AAVS1) (Weber, Frati, et al. 2020). As expected, the disruption of the LRF binding site resulted in HbF induction as shown by higher %F-cells compared to AAVS1 control. These higher levels of F-cells resulted in decreased apoptosis, under both normoxic and hypoxic conditions, clearly demonstrating the positive and selective effect of HbF on SCD cell survival (Figure 2). In summary, our study shows that HbF has a dual beneficial effect in SCD by conferring a preferential survival of F-cells in the circulation and by decreasing ineffective erythropoiesis. These findings thus bring new insights into the role of HbF in modulating clinical severity of anemia in SCD by both regulating red cell production and red cell destruction. Disclosures No relevant conflicts of interest to declare.

scholarly journals Inhibition of Fibroblast Growth Factor-23 (FGF-23) Rescues Bone and Hematopoietic Stem Cell Niche Defects in Beta-Thalassemia, Uncovering the Missing Link between Hematopoiesis and Bone

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 572-572
Author(s):  
Annamaria Aprile ◽  
Laura Raggi ◽  
Simona Bolamperti ◽  
Mariangela Storto ◽  
Isabella Villa ◽  
...  
Keyword(s):  
Research Funding ◽  
Fibroblast Growth Factor 23 ◽  
Beta Thalassemia ◽  
Erythroid Cells ◽  
Ineffective Erythropoiesis ◽  
Hematopoietic Stem ◽  
Bm Niche ◽  
Fgf 23

Abstract The bone marrow (BM) niche regulation and interactions with hematopoietic stem cells (HSC) have been extensively studied in steady state conditions and malignancies, but are still underexplored in hematological inherited disorders. We provided the first demonstration of impaired HSC function caused by an altered BM niche in a non-malignant disease, beta-thalassemia (BT) (Aprile et al., Blood 2020). BT is a globally widespread congenital hemoglobin disorder, resulting in severe anemia, ineffective erythropoiesis and multi-organ secondary complications, including bone alterations. Correction of the genetic defect is achieved by transplantation of HSC from healthy donors or autologous HSC from patients upon gene therapy. Since the quality and the engraftment of HSC depend on the BM microenvironment, niche-HSC crosstalk plays a crucial role for transplantation outcome. During the analysis of different components of the niche, we found reduced bone density in BT th3 mice, along with a defective HSC supporting activity by the BM stromal niche. Interestingly, osteoporosis is a constant hallmark in BT patients. We investigated the mechanisms underlying bone and HSC niche defects focusing on the role of fibroblast growth factor-23 (FGF-23), a hormone mainly secreted by osteocytes, but also by erythroid cells, which negatively modulates bone metabolism. Since FGF-23 is stimulated by the anemia-related factor erythropoietin (EPO), we hypothesized that the high EPO levels in BT might contribute to increase FGF-23, potentially affecting bone and BM niche homeostasis. We found high levels of circulating FGF-23 in th3 mice (wt vs. th3: 290.5±27.3 vs. 1823±136.1 pg/ml, p<0.0001) and in BT patients (HD vs. THAL: 94.7±1.8 vs. 117.2±5.3 RU/ml, p<0.01), associated to its increased expression by bone and BM erythroid cells. In vivo neutralization of EPO axis was sufficient to normalize FGF-23 levels (th3 vs. th3+anti-EPO: 1591±162.2 vs. 496.1±33.3 pg/ml, p<0.001), thus demonstrating the causative role of EPO. EPO stimulation and signaling inhibition strategies highlighted the involvement of Erk1/2 and Stat5 pathways in activating Fgf-23 transcription in bone and BM erythroid cells, respectively. To provide proof of concept data on the contribution of FGF-23 to BT bone and stromal niche alterations, we inhibited FGF-23 signaling. In vivo administration of FGF-23 blocking peptide rescued the trabecular bone density in th3 mice (th3 vs. th3+FGF23inh: 138.2±4.9 vs. 166.9±5.2 mg/cm 3, p<0.01). Short-term inhibition treatment (38 hours) was sufficient to enhance bone mineralization by acting on Alkaline Phosphatase and on the expression of the main regulators of mineralization Dmp1 and Mepe by osteocyte, whereas long-term administration (12 days) restored also osteoblast number and bone deposition. Importantly, FGF-23 inhibition normalized the expression of key niche molecules, such as Jagged-1 and osteopontin, involved in the functional crosstalk between HSC and the stromal niche. Consistently, the treatment restored the frequency of th3 HSC by expanding the pool of quiescent cells (th3 vs. th3+FGF23inh: 0.026 vs. 0.045% on Lin neg BM cells, p<0.01). FGF-23 inhibition had also a positive anti-apoptotic effect on the expanded BM erythroid compartment (th3 vs. th3+FGF23inh: 61.6±1.3 vs. 51.1±2.1% of BM Ter119 + cells, p<0.001), promoting the maturation of early erythroid precursors (th3 vs. th3+FGF23inh: 8.5±1 vs. 16.4±1.1% of BM Pro-Erythroblasts, p<0.0001), as already shown in models of secondary anemias. Evidence in BT patients showed negative correlations between FGF-23 levels and markers of bone homeostasis (e.g. osteocalcin R 2=0.88, p<0.05) and positive correlations with makers of ineffective erythropoiesis (e.g. circulating reticulocytes R 2=0.83, p<0.05), thus positioning FGF-23 as the molecule at the crossroads of erythropoiesis and bone metabolism in BT. Our findings uncover an underexplored role of FGF-23 in bone and BM niche defects in a primary anemia, as a condition of chronic EPO stimulation, and propose FGF-23 as the missing link between hematopoiesis and bone regulation. The inhibition of FGF-23 signaling might provide a novel strategy to ameliorate bone compartment and restore HSC-BM niche interactions in BT by a 'two birds with one stone' approach, with a potential translational relevance in improving HSC transplantation and gene therapy. Disclosures Cappellini: Celgene: Consultancy, Research Funding; Vifor: Consultancy; La Jolla: Research Funding; Protagonist Therapeutics: Research Funding; IONIS Pharmaceuticals: Consultancy; CRISPR Therapeutics: Research Funding; Novartis: Consultancy, Honoraria, Research Funding.

scholarly journals Fetal hemoglobin induction by acetate, a product of butyrate catabolism [see comments]

Blood ◽  
1994 ◽  
Vol 84 (9) ◽  
pp. 3198-3204 ◽  
Author(s):  
G Stamatoyannopoulos ◽  
CA Blau ◽  
B Nakamoto ◽  
B Josephson ◽  
Q Li ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Sickle Cell Disease ◽  
Umbilical Cord Blood ◽  
Sodium Acetate ◽  
Fetal Hemoglobin ◽  
Cell Disease ◽  
Gamma Globin ◽  
Hbf Induction ◽  
Globin Synthesis

Abstract Butyrate induces fetal hemoglobin (HbF) synthesis in cultures of erythroid progenitors, in primates, and in man. The mechanism by which this compound stimulates gamma-globin synthesis is unknown. In the course of butyrate catabolism, beta oxidation by mitochondrial enzymes results in the formation of two acetate molecules from each molecule of butyrate. Studies were performed to determine whether acetate itself induces HbF synthesis. In erythroid burst-forming unit (BFU-E) cultures from normal persons, and individuals with sickle cell disease and umbilical-cord blood, dose-dependent increases in gamma-globin protein and gamma mRNA were consistently observed in response to increasing acetate concentrations. In BFU-E cultures from normal adults and patients with sickle cell disease, the ratio of gamma/gamma + beta mRNA increased twofold to fivefold in response to acetate, whereas the percentage of BFU-E progeny staining with an anti-gamma monoclonal antibody (MoAb) increased approximately twofold. Acetate-induced increases in gamma-gene expression were also noted in the progeny of umbilical cord blood BFU-E, although the magnitude of change in response to acetate was less because of a higher baseline of gamma- chain production. The effect of acetate on HbF induction in vivo was evaluated using transgenic mouse and primate models. A transgenic mouse bearing a 2.5-kb mu locus control region (mu LCR) cassette linked to a 3.3-kb A gamma gene displayed a near twofold increase in gamma mRNA during a 10-day infusion of sodium acetate at a dose of 1.5 g/kg/d. Sodium acetate administration in baboons, in doses ranging from 1.5 to 6 g/kg/d by continuous intravenous infusion, also resulted in the stimulation of gamma-globin synthesis, with the percentage of HbF- containing reticulocytes (F reticulocytes) approaching 30%. Surprisingly, a dose-response effect of acetate on HbF induction was not observed in the baboons, and HbF induction was not sustained with prolonged acetate administration. These results suggest that both two- carbon fatty acids (acetate) and four-carbon fatty acids (butyrate) stimulate synthesis of HbF in vivo.

scholarly journals Truncated Erythropoietin Receptors Confer an In Vivo Selective Advantage in Gene-Modified Erythroid Cells Expressing Fetal Hemoglobin Due to BCL11A Interference

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2063-2063
Author(s):  
Naoya Uchida ◽  
Claire Drysdale ◽  
Morgan Yapundich ◽  
Jackson Gamer ◽  
Tina Nassehi ◽  
...  
Keyword(s):  
Rhesus Macaques ◽  
Fetal Hemoglobin ◽  
Selective Advantage ◽  
Erythroid Cells ◽  
Post Transplant ◽  
Human Cd34 ◽  
Cd34 Cells ◽  
Hbf Induction

Hematopoietic stem cell gene therapy for hemoglobin disorders, such as sickle cell disease, requires high-level gene marking and robust therapeutic globin expression in erythroid cells (>20% of γ- or β-globin production) for widespread successful clinical application. We previously demonstrated that lentiviral transduction of a truncated human erythropoietin receptor (thEpoR) gene allows for erythropoietin-dependent selective proliferation of gene-modified human erythroid cells during in vitro differentiation (ASH 2017). In this study, we sought to evaluate whether thEpoR can enhance the phenotypic effect of a therapeutic vector in erythroid cells in xenograft mouse and autologous non-human primate transplantation models. To investigate this hypothesis, we designed lentiviral vectors encoding both thEpoR and BCL11A-targeting micro RNA-adapted short hairpin RNA (shmiBCL11A), driven off an erythroid specific ankyrin 1 (ANK1) promoter. Both selective proliferation and high-level fetal hemoglobin (HbF) induction were observed in in vitro erythroid differentiation cultures using transduced human CD34+ cells. Healthy donor CD34+ cells were transduced with shmiBCL11A vector, thEpoR-shmiBCL11A vector, and GFP vector (control). Transduced cells were transplanted into immunodeficient NBSGW mice. Five months post-transplant, xenograft bone marrow cells were evaluated for human cell engraftment (human CD45+) and vector copy number (VCN) in both human CD34+ progenitor cells and glycophorin A+ (GPA+) erythroid cells. HbF production was also measured in GPA+ erythroid cells by reverse phase HPLC. We observed efficient transduction in transduced CD34+ cells in vitro (VCN 2.1-5.1) and similar human cell engraftment among all groups (84-89%). The VCN with thEpoR-shmiBCL11A transduction was 3-fold higher in human erythroid cells when compared to CD34+ cells (p<0.01), but not with shmiBCL11A or GFP vectors. HbF levels were significantly elevated in thEpoR-shmiBCL11A vector (43±6%, p<0.01) when compared to no transduction control (1±0%), but not for either shmiBCL11A vector (3±1%) or GFP vector (1±0%). These data demonstrate selective proliferation of gene-modified erythroid cells, as well as enhanced HbF induction with thEpoR-shmiBCL11A transduction. We then performed autologous rhesus CD34+ cell transplantation using either shmiBCL11A vector (142562 and RA0706, n=2, compared to a GPA promoter-derived shmiBCL11A vector) or thEpoR-shmiBCL11A vector (ZL50 and ZM24, n=2, compared to a Venus-encoding vector). Transduced CD34+ cells were transplanted into autologous rhesus macaques following 2x5Gy total body irradiation. Efficient transduction was observed in CD34+ cells in vitro among all 4 macaques (VCN 3.8-8.7) using a high-density culture protocol (Uchida N, Mol Ther Methods Clin Dev. 2019). In shmiBCL11A transduction animals, engraftment of gene-modified cells (VCN 0.2-1.0) and robust HbF induction (14-16%) were observed 1 month post-transplant. However, VCN and HbF levels were reduced down to VCN ~0.1 and HbF ~0.4% in both animals 6 months post-transplant. In contrast, a thEpoR-shmiBCL11A transduction animal (ZL50) resulted in engraftment of gene-modified cells (VCN 0.8-1.0) and robust HbF induction (~18%) 1 month post-transplant, with both gene marking and HbF levels remaining high at VCN 0.6-0.7 and HbF ~15% 4 months post-transplant. These data suggest that shmiBCL11A transduction results in transient HbF induction in gene-modified erythroid cells, while thEpoR-based selective advantage allows for sustained HbF induction with shmiBCL11A. In summary, we developed erythroid-specific thEpoR-shmiBCL11A expressing vectors, enhancing HbF induction in gene-modified erythroid cells in xenograft mice and rhesus macaques. While further in vivo studies are desirable, the use of thEpoR appears to provide a selective advantage for gene-modified erythroid cells in gene therapy strategies for hemoglobin disorders. Disclosures No relevant conflicts of interest to declare.

scholarly journals Inhibition of Fibroblast Growth Factor-23 (FGF-23) As a Novel Strategy to Target Bone and Hematopoietic Stem Cell Niche Defects in Beta-Thalassemia

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 2-2
Author(s):  
Annamaria Aprile ◽  
Laura Raggi ◽  
Mariangela Storto ◽  
Isabella Villa ◽  
Sarah Marktel ◽  
...  
Keyword(s):  
Bone Mineralization ◽  
Fibroblast Growth Factor 23 ◽  
Beta Thalassemia ◽  
Causative Role ◽  
Ineffective Erythropoiesis ◽  
Hematopoietic Stem ◽  
Bm Niche ◽  
Fgf 23

In the last decade many studies unraveled the bone marrow (BM) niche regulation and crosstalk with hematopoietic stem cells (HSC) in steady state conditions and malignancies, but HSC-niche interactions are still underexplored in hematological inherited disorders. We have recently provided the first demonstration of impaired HSC function caused by an altered BM niche in a non-malignant disease, beta-thalassemia (BT) (Aprile et al., Blood 2020). BT is a congenital hemoglobin disorder resulting in severe anemia, ineffective erythropoiesis and multi-organ secondary complications, such as bone defects. It is one of the most globally widespread monogenic diseases, which can be cured by transplantation of HSC from compatible healthy donors or autologous HSC from patients upon gene therapy. Cases of graft failure have been reported, but causes have not been deeply investigated and might include an impaired HSC function and a defective supporting activity of the BM niche, worsened by age and disease progression. We showed that the prolonged residence of HSC into an altered BM stromal niche in BT Hbbth3/+ (th3) mice negatively affects stem cell number, quiescence and self-renewal. Moreover, we demonstrated that correction of HSC-stromal niche crosstalk rescues BT HSC function by in vivo reactivation of parathyroid hormone (PTH) signaling. Consistently with the common finding of osteoporosis in BT patients, we found reduced bone deposition and low levels of PTH also in the murine model. We investigated the potential mechanisms underlying the decreased PTH and bone defect and we focused on the role of fibroblast growth factor-23 (FGF-23). FGF-23 is a systemic hormone mainly secreted by osteocytes, which acts as negative regulator of bone metabolism by inhibiting bone mineralization and PTH production by parathyroid glands. Since FGF-23 is positively modulated by the anemia-related factor erythropoietin (EPO), we hypothesized that the high EPO levels in BT, subsequent to ineffective erythropoiesis, might contribute to increase FGF-23. We measured high levels of circulating FGF-23 in th3 mice (wt vs. th3: 399.7±69.77 vs. 1975±209.3 pg/ml, p&lt;0.01) and also in BT patients (HD vs. THAL: 94.2±3.8 vs. 125.8±9.2 RU/ml, p&lt;0.05). To provide proof of concept data of the causative role of FGF-23 on BT bone and stromal niche defects, we inhibited FGF-23 signaling. FGF-23 inhibition by in vivo administration of FGF-23 blocking peptide rescued the bone defect in th3 mice, by increasing trabecular bone mineral density (th3 vs. th3+FGF23inh: 117.7±3.3 vs. 181.1±6.9 mg/cm3, p&lt;0.0001). Importantly, the treatment restored the frequency of HSC to levels comparable to wild-type controls by expanding the pool of quiescent cells (th3 vs. th3+FGF23inh: 0.03±0.002 vs. 0.07±0.0% on Linneg BM cells, p&lt;0.0001). Consistently, we found increased the expression of key molecules by bone cells, such as Jagged-1 and osteopontin, involved in the functional crosstalk between HSC and the stromal niche. Interestingly, FGF-23 inhibition had also a positive anti-apoptotic effect on the expanded BM erythroid compartment, promoting the maturation of erythroid precursors, as already shown in models of secondary anemias. Preliminary evidence in BT patients showed negative correlations between FGF-23 levels and markers of bone homeostasis (e.g. osteocalcin and vitamin D) and positive correlations with makers of ineffective erythropoiesis (e.g. reticulocytes), thus proposing FGF-23 as the molecule at the crossroads of erythropoiesis and bone metabolism in BT. In vivo studies and molecular analysis in th3 mice and patients' samples will better unravel the causative role of EPO on FGF-23 levels in BT and the negative impact of high FGF-23 on bone mineralization and BM stromal niche-HSC interactions. Our findings uncover an underexplored role of FGF-23 in bone and BM niche defects in BT, as a condition of severe anemia and chronic EPO stimulation. The inhibition of FGF-23 signaling might provide a novel strategy to ameliorate bone compartment and restore HSC-BM niche interactions in BT, with a potential translational relevance in improving HSC transplantation approaches. Disclosures Motta: Sanofi Genzyme: Honoraria. Cappellini:BMS: Honoraria; CRISPR Therapeutics, Novartis, Vifor Pharma: Membership on an entity's Board of Directors or advisory committees; Genzyme/Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Does Gene Therapy in Beta Thalassemia Normalize Novel Markers of Ineffective Erythropoiesis and Iron Homeostasis?

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 816-816 ◽  
Author(s):  
Alexis A. Thompson ◽  
Tomas Ganz ◽  
Mary Therese Forsyth ◽  
Elizabeta Nemeth ◽  
Sherif M. Badawy
Keyword(s):  
Gene Therapy ◽  
Stem Cell ◽  
Iron Overload ◽  
Serum Ferritin ◽  
Research Funding ◽  
Iron Homeostasis ◽  
Beta Thalassemia ◽  
Ineffective Erythropoiesis ◽  
Liver Iron ◽  
Equity Ownership

BACKGROUND: Ineffective erythropoiesis in thalassemia alters iron homeostasis, predisposing to systemic iron overload. Successful allogeneic hematopoietic stem cell transplantation (HSCT) in thalassemia major corrects anemia, should eliminate ineffective erythropoiesis (IE) and normalize iron homeostasis (IH). Whether gene therapy (GT) will fully correct IE and IH is not known. This cross-sectional observational study evaluated the iron status of patients with beta thalassemia following HSCT or GT, and compared them with cohorts of patients with thalassemia intermedia (TI) or transfusion-dependent thalassemia (TDT) using recently introduced biomarkers along with imaging studies and other clinical assessments to better understand and characterize IE and IH across groups. METHODS: We evaluated a convenience sample of 29 participants with beta thalassemia (median age 25 years, IQR 21-35; females 55%; Asian 52%). Participants in the HSCT (n=6) and GT (n=10) groups were evaluated on average 116.5 and 46.9 months following cell infusion, respectively. TDT patients (n= 9) were evaluated pre-transfusion and off iron chelation for at least 7 days, and TI (n=4) were un-transfused or not transfused in &gt;3 years. Clinical lab assessments and MRI R2*/ T2* to assess heart and liver iron burden including post-processing, were performed using local clinical protocols. ELISAs for hepcidin, erythroferrone (Erfe) and GDF-15 were performed in a blinded manner. RESULTS: Median values for all IE and IH parameters tested were normal in the HSCT group, and were significantly lower than in all other groups. There were significant differences among all groups for hemoglobin (p=0.003), erythropoietin (Epo) (p=0.03), serum ferritin (SF) (p=0.01), transferrin (p=0.006), soluble transferrin receptor (sTfR) (p=0.02), serum hepcidin: serum ferritin (H:F) ratio (p=0.006), Erfe (p=0.001), GDF15 (p=0.003), and liver iron content (LIC) by MRI R2* (p=0.02). H:F ratio, a surrogate for predisposition to systemic iron loading, inversely correlated with Erfe (rs= -0.85, p&lt;0.0001), GDF15 (rs= -0.69, p=0.0001) and liver R2* (rs= -0.66, p=0.0004). In a multivariate analysis, adjusted for gender and race, H:F ratio and Epo levels predicted Erfe and GDF15 (p=0.05 and p=0.06; p=0.01 and p=0.05), respectively. Even after excluding GT patients that are not transfusion independent (N=2), SF, Epo, sTfR and hepcidin remain abnormal in the GT group, and there were no significant differences in these parameters between GT and TDT. However, novel biomarkers of IH and IE suggested lower ineffective erythropoiesis in GT compared to TDT (median (IQR) Erfe, 12 (11.6-25.2) vs. 39.6 (24.5-54.7), p=0.03; GDF15, 1909.9 (1389-4431) vs. 8906 (4421-12331), p=0.02), respectively. Erfe and GDF15 were also lower in GT compared to TI, however these differences did not reach statistical significance. There were no differences in hepcidin, ferritin, or H:F by race, however Erfe and GDF15 were significantly lower in Asians compared to non-Asians (p=0.006 and p=0.02, respectively). CONCLUSION: Nearly 4 years post infusion, most subjects with TDT treated with GT are transfusion independent with near normal hemoglobin, however, studies in this limited cohort using conventional measures suggest IE and IH improve, particularly when transfusion support is no longer needed, however they remain abnormal compared to HSCT recipients, who using these parameters appear to be cured. STfR did not detect differences, however GDF15 and Erfe were more sensitive assays that could demonstrate significant improvement in IE and IH with GT compared to TDT. Contribution to IE by uncorrected stem cell populations post GT cannot be determined. Transduction enhancement and other recent improvements to GT may yield different results. Longitudinal studies are needed to determine if thalassemia patients treated with GT will have ongoing IE predisposing to systemic iron overload. Disclosures Thompson: bluebird bio, Inc.: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Baxalta: Research Funding. Ganz:Intrinsic LifeSciences: Consultancy, Equity Ownership. Nemeth:Intrinsic LifeSciences: Consultancy, Equity Ownership; Silarus Therapeutics: Consultancy, Equity Ownership; Keryx: Consultancy; Ionis Pharmaceuticals: Consultancy; La Jolla Pharma: Consultancy; Protagonist: Consultancy.

Removal of Macrophages From the Erythroid Niche Impairs Stress Erythropoiesis but Improves Pathophysiology of Polycythemia Vera and Beta-Thalassemia

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 81-81
Author(s):  
Pedro Ramos ◽  
Carla Casu ◽  
Sara Gardenghi ◽  
Laura Breda ◽  
Bart J Crielaard ◽  
...  
Keyword(s):  
Polycythemia Vera ◽  
Research Funding ◽  
Serum Iron ◽  
Transferrin Saturation ◽  
Cell Surface Expression ◽  
Beta Thalassemia ◽  
Ineffective Erythropoiesis ◽  
Erythroid Progenitor ◽  
Distribution Width ◽  
Stress Erythropoiesis

Abstract Abstract 81 We investigated the contribution of macrophages to physiological and pathological conditions in which erythropoietic activity is enhanced. We utilized mouse models of a) anemia by phlebotomy-induced stress erythropoiesis (SE); b) increased erythropoiesis by erythropoietin (Epo) administration; c) Polycythemia Vera (Jak2V617F/+ or PV) and d) beta-thalassemia intermedia (Hbbth3/+ or BTI) in which macrophages were chemically depleted by injection of liposome-clodronate (LC). While chronic injection (up to 3 months) of LC in normal mice had little effect on steady state erythropoiesis, depletion of macrophages severely impaired recovery from anemia following phlebotomy and significantly limited the increase in hematocrit (Htc) in animals treated with Epo. To exclude that this effect was mediated by decreased serum iron parameters, we used mice iron overloaded by dietary means or affected by hemochromatosis (Hfe-KO and Hamp-KO). In these mice, recovery from anemia was still impaired following macrophage depletion, even though serum iron and transferrin saturation levels were elevated and unaffected by LC administration. In vitro studies using both mouse and human primary erythroblasts (EBs) indicated that EBs in S-phase were twice as many compared to EBs cultured in absence of macrophages. The numbers of terminally mature erythroid cells were up to six fold higher in co-culture conditions. Experiments using transwells indicate that direct contact between EBs and macrophages was required to generate this effect. Since our data highlighted an important role of macrophages in enhancing erythropoiesis, we investigated two disorders in which the pool of erythroid progenitor cells is expanded, such as PV and BTI. Chronic administration of LC in PV mice completely reversed splenomegaly and the Htc (P<0.001). BTI mice exhibited normal spleen, amelioration of ineffective erythropoiesis (by accelerating the differentiation of EBs to erythrocytes), improvement of red blood cell (RBC) morphology, red cell distribution width (RDW, P<0.001) and increased hemoglobin levels (∼2g/dL, P<0.01). This effect was due to an increased RBC lifespan following LC administration (P<0.001), which was associated with a decrease in hemichrome formation, but not with a reduction in erythophagocytosis. Our observations indicate that macrophages directly modulate stress- and pathological erythropoiesis. Several adhesion molecules participate in the formation of interactions within the erythroblastic islands, including integrins. Interestingly, βeta1integrin and its associated protein, focal adhesion kinase-1 (Fak1), were reported to be necessary for the compensatory response to anemia, suggesting that this pathway might be involved in the macrophage-EB cross-talk. More EBs co-cultured with macrophages retained cell surface expression of βeta1integrin molecule during the last stage of cell differentiation compared to EBs cultured alone, even though other differentiation markers did not shown any variation. Fak1 phosphorylation in EBs was induced by co-culturing them with splenic macrophages, suggesting that Fak1 signaling is one of the pathways activated in EBs through contact with macrophages. Administration of a FAK1 inhibitor (FAK1i) decreased proliferation of EB co-cultured with macrophages, while delayed recovery from anemia and decreased the spleen size in phlebotomized animals (40% decrease compared to phlebotomized control animals at day 4; P=0.032). Finally, short-term administration of FAK1i to BTI animals rapidly reverted splenomegaly with a concurrent reduction of erythroid expansion in both BM and spleen and led to amelioration of anemia, supported by increased RBCs count. Our data indicate that, while macrophages allow proper erythroid response under conditions of induced anemia or increased erythropoiesis in wt mice, they contribute to the pathological progression of PV and BTI. Activation of Fak1 promotes erythroid proliferation and pathological development, while its inhibition limits ineffective erythropoiesis and splenomegaly in BTI. In conclusion, we identified a new mechanism contributing to the pathophysiology of these disorders, which we believe will have critical scientific and therapeutic implications in the near future. Disclosures: Levine: Agios Pharmaceuticals: Research Funding. Rivella:Novartis Pharmaceuticals: Consultancy; Biomarin: Consultancy; Merganser Biotech: Consultancy, Equity Ownership, Research Funding; Isis Pharma: Consultancy, Research Funding.

In Vivo Efficacy of Bcl11a Erythroid-Enhancer Deletion in Humanized Mouse Models of Anemia

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2465-2465 ◽  
Author(s):  
Thomas M Ryan ◽  
Suean Daimia Fontenard ◽  
Shanrun Liu ◽  
Jonathan Lockhart ◽  
Michael Berlett
Keyword(s):  
Mouse Models ◽  
Fetal Hemoglobin ◽  
Thalassemia Major ◽  
Beta Thalassemia ◽  
Globin Genes ◽  
Humanized Mouse ◽  
Gamma Globin ◽  
Hemoglobin Switching ◽  
Humanized Mouse Models

Abstract Autologous cell therapy holds great promise for the treatment of beta thalassemia major and hemoglobinopathies like sickle cell anemia. Gene editing of a patient's own stem cells to reactivate the silenced gamma globin gene is one approach under active development. Prior to directly testing these new therapies in patients, we can answer some basic questions about their in vivo efficiency and efficacy in humanized mouse models of anemia. These models have their endogenous adult alpha and beta globin genes replaced with human alpha, gamma, and beta globin genes. These mice synthesize high level of human fetal hemoglobin during fetal life and complete their fetal-to-adult hemoglobin switch after birth. Experimental strategies designed to reactivate the silenced fetal gamma globin genes in adult erythroid cells are easily tested in vivo in these humanized hemoglobin switching mouse models. The silenced human fetal gamma globin genes can be activated by mutating the erythroid-specific enhancer of Bcl11a by gene editing. CRISPR sgRNAs, designed to target the +62 kb DNase I hypersensitive site in the second intron of Bcl11a, were microinjected along with Cas9 mRNA, into fertilized mouse embryos collected from humanized hemoglobin (Hb A) mice. The indel mutations that were generated in the founder animals were characterized and bred to homozygosity. The data demonstrates that the sgRNAs tested were successful in creating multiple unique mutations at the erythroid enhancer target sites. These mutations were transmitted through the germline allowing the effect of individual edited alleles to be analyzed. The majority of the mutations showed marginal increases in the number of F-cells over control animals. Significantly, despite having homozygous mutation of the erythroid-enhancer in all cells, fetal hemoglobin expression remains heterocellular. Importantly, the therapeutic efficacy of reactivating fetal hemoglobin with specific Bcl11a erythroid-enhancer mutations for the treatment of beta thalassemia major and sickle cell anemia was directly measured in vivo in these humanized models of disease. The reactivation of gamma globin in these humanized mouse models provides us with an opportunity to further interrogate the Bcl11a enhancer element, identify additional factors involved in hemoglobin switching and elucidate the mechanism driving pancellular vs heterocellular fetal hemoglobin expression. Disclosures No relevant conflicts of interest to declare.

Fetal hemoglobin in sickle cell disease: relationship to erythrocyte phosphatidylserine exposure and coagulation activation

Blood ◽  
2000 ◽  
Vol 96 (3) ◽  
pp. 1119-1124 ◽  
Author(s):  
B. N. Yamaja Setty ◽  
Surekha Kulkarni ◽  
A. Koneti Rao ◽  
Marie J. Stuart
Keyword(s):  
Sickle Cell Disease ◽  
Sickle Cell ◽  
Thrombin Generation ◽  
Fetal Hemoglobin ◽  
Strong Relationship ◽  
Cell Disease ◽  
Red Cell Membrane ◽  
Prothrombin Fragment ◽  
F Cells

In sickle cell disease (SCD), loss of erythrocyte membrane phospholipid asymmetry occurs with the exposure of phosphatidylserine (PS), which provides a docking site for coagulation proteins. In vivo sickling/desickling, with resulting red cell membrane changes and microvesicle formation, appears to be one of the factors responsible for PS exposure. We evaluated children with SCD homozygous for sickle hemoglobin (SS disease) and controls (n = 65) and demonstrate that high levels of fetal hemoglobin (assessed as F cells) are associated with decreased microvesicle formation, PS exposure, and thrombin generation. F cells correlated inversely with both microvesicles and PS positivity (P < .000001) in SS disease. Multiple regression analyses using various hematologic parameters as independent variables, and either microvesicles or PS positivity as the dependent variable, showed a strong relationship only with F cells. Additionally, plasma prothrombin fragment F1.2 levels (a marker for thrombin generation) correlated with both PS positivity (P < .001) and F cells (P < .01). An F-cell level of approximately 70% was associated with normal levels of prothrombin fragment F1.2 and with microvesicle formation indistinguishable from control values. We suggest that the use of such surrogate biologic markers in conjunction with F-cell numbers may provide valuable insights into the biology and consequences of in vivo sickling.

scholarly journals Identification of F-reticulocytes by two-stage fluorescence image cytometry.

1996 ◽  
Vol 44 (4) ◽  
pp. 393-397 ◽  
Author(s):  
M L Osterhout ◽  
K Ohene-Frempong ◽  
K Horiuchi
Keyword(s):  
Acridine Orange ◽  
Staining Method ◽  
Fetal Hemoglobin ◽  
Image Cytometry ◽  
Precise Determination ◽  
Beta Thalassemia ◽  
Special Equipment ◽  
Two Stage ◽  
Fluorescence Image ◽  
F Cells

Precise determination of reticulocytes (young red blood cells) containing fetal hemoglobin (Hb F), F-reticulocytes, is important for assessment of the efficacy of drugs such as hydroxyurea and butyrate in elevating the levels of Hb F in patients with sickle cell disease (SCD) and beta-thalassemia. We developed a reliable and easily applicable method for determining F-reticulocytes using fluorescence image cytometry. Reticulocytes were first identified by preparing a monolayer smear of blood stained by acridine orange. Images of reticulocytes and of all cells were obtained for a selected area on the smear. After removing the acridine orange, cells containing Hb F (F-cells) in the same area were then identified by immunofluorescence. Using images of F-cells, reticulocytes, and all cells for the same fields it was possible to identify F-reticulocytes. To assess the validity of our two-stage staining method, we compared our results with those obtained by traditional methods. There was significant correlation of our method with the conventional immunofluorescence staining method for F-cells (r2 = 0.99; slope = 0.99) and with the accepted brilliant cresyl blue method for reticulocytes (r2 = 0.97; slope = 0.96). Heretofore, the ability to determine F-reticulocyte levels has been limited to a small number of laboratories possessing special equipment and techniques. The method presented here should be of great interest to many basic science and clinical investigators involved in studies evaluating synthesis of Hb F.

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