GENETIC LOSS OF ERYTHROID TFR2 STRONGLY AFFECTS THE THALASSEMIC PHENOTYPE IN MICE
(Abstract release date: 05/19/16)
EHA Library. Nai A. 06/10/16; 135166; S133
Dr. Antonella Nai
Contributions
Contributions
Abstract
Abstract: S133
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 11:30 - 11:45
Location: Hall C15
Background
Transferrin receptor 2 (TFR2) is a multifaceted protein that in the liver activates hepcidin, the master regulator of iron homeostasis, while in erythroid cells is a component of the erythropoietin (EPO) receptor complex. We have shown that the lack of Tfr2 in the bone marrow (BM) increases the EPO sensitivity of erythroid cells and mimics iron-deficiency (Nai et al., Blood 2015).β-thalassemias are recessive severe disorders of beta-globin gene, characterized by microcytic anemia, ineffective erythropoiesis, splenomegaly and secondary iron overload. Several studies demonstrated that iron restriction partially corrects the β-thalassemia phenotype in the Hbbth3/+ model of thalassemia intermedia.
Aims
In order to verify if the absence of Tfr2, mimicking iron-deficiency, could ameliorate the thalassemic phenotype we generated thalassemic animals with BM selective Tfr2 inactivation.
Methods
We generated thalassemic mice with (Hbbth3/+) or without BM Tfr2 (Tfr2BMKO/Hbbth3/+) by transplanting BM cells from Hbbth3/+ or Tfr2-/-/Hbbth3/+ mutants into lethally irradiated wild-type mice. Chimerism and hematological parameters were evaluated at 2 months. Mice were sacrificed 4 months after BM transplantation (BMT). At sacrifice blood was collected for hematological analysis, transferrin saturation (TS) and Epo levels; liver, spleen and BM cells were used for gene expression, tissue iron quantification, histology and flow cytometry analysis.
Results
Two months after BMT the engraftment of donor cells was 98-99%. Tfr2BMKO/Hbbth3/+ and Hbbth3/+ animals appear viable and indistinguishable from one another. Tfr2BMKO/Hbbth3/+ mice have greater red cells count and Hb levels as compared to Hbbth3/+ animals. On the contrary, 4 months after BMT Tfr2BMKO/Hbbth3/+ mice are smaller and more anemic than Hbbth3/+controls, have increased spleen size, TS and hepatic iron, but reduced spleen iron content. The alteration of body iron homeostasis is likely due to their lower hepcidin levels as compared with Hbbth3/+mice. The ineffective erythropoiesis is exacerbated in the absence of Tfr2 and results in extramedullary spleen and liver erythropoiesis. Anemia is accompanied by increased Epo gene trascription in the kidney and by increased expression of Epo target genes, such as Epor, Bcl-xL and erythroferrone (Erfe) in BM.
Conclusion
Deleting erythroid Tfr2 in Hbbth3/+ animals has a transient beneficial effect, but is detrimental in long-term. Reasonably the loss of Tfr2 increases the sensitivity of thalassemic erythroid cells to Epo stimulation (as we demonstrated for normal cells), favouring erythroid reconstitution after BMT. However, when erythropoiesis reaches a steady state, increased stimulation becomes deleterious. We propose that this occurs through high and persistent production of erythroferrone, the soluble factor released by the erythroblasts in order to inhibit the hepcidin expression. This would increase iron absorption and release, causing iron overload, further impairing the thalassemic erythropoiesis and generating a “thalassemia major-like phenotype” in Tfr2BMKO Hbbth3/+ mice. Further studies will better elucidate the mechanism of the observed biphasic effect on the phenotype and whether a time-controlled modulation of Tfr2 might improve β-thalassemia.
Session topic: Red blood cells and iron
Keyword(s): Erythropoieisis, Thalassemia, Transferrin receptor
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 11:30 - 11:45
Location: Hall C15
Background
Transferrin receptor 2 (TFR2) is a multifaceted protein that in the liver activates hepcidin, the master regulator of iron homeostasis, while in erythroid cells is a component of the erythropoietin (EPO) receptor complex. We have shown that the lack of Tfr2 in the bone marrow (BM) increases the EPO sensitivity of erythroid cells and mimics iron-deficiency (Nai et al., Blood 2015).β-thalassemias are recessive severe disorders of beta-globin gene, characterized by microcytic anemia, ineffective erythropoiesis, splenomegaly and secondary iron overload. Several studies demonstrated that iron restriction partially corrects the β-thalassemia phenotype in the Hbbth3/+ model of thalassemia intermedia.
Aims
In order to verify if the absence of Tfr2, mimicking iron-deficiency, could ameliorate the thalassemic phenotype we generated thalassemic animals with BM selective Tfr2 inactivation.
Methods
We generated thalassemic mice with (Hbbth3/+) or without BM Tfr2 (Tfr2BMKO/Hbbth3/+) by transplanting BM cells from Hbbth3/+ or Tfr2-/-/Hbbth3/+ mutants into lethally irradiated wild-type mice. Chimerism and hematological parameters were evaluated at 2 months. Mice were sacrificed 4 months after BM transplantation (BMT). At sacrifice blood was collected for hematological analysis, transferrin saturation (TS) and Epo levels; liver, spleen and BM cells were used for gene expression, tissue iron quantification, histology and flow cytometry analysis.
Results
Two months after BMT the engraftment of donor cells was 98-99%. Tfr2BMKO/Hbbth3/+ and Hbbth3/+ animals appear viable and indistinguishable from one another. Tfr2BMKO/Hbbth3/+ mice have greater red cells count and Hb levels as compared to Hbbth3/+ animals. On the contrary, 4 months after BMT Tfr2BMKO/Hbbth3/+ mice are smaller and more anemic than Hbbth3/+controls, have increased spleen size, TS and hepatic iron, but reduced spleen iron content. The alteration of body iron homeostasis is likely due to their lower hepcidin levels as compared with Hbbth3/+mice. The ineffective erythropoiesis is exacerbated in the absence of Tfr2 and results in extramedullary spleen and liver erythropoiesis. Anemia is accompanied by increased Epo gene trascription in the kidney and by increased expression of Epo target genes, such as Epor, Bcl-xL and erythroferrone (Erfe) in BM.
Conclusion
Deleting erythroid Tfr2 in Hbbth3/+ animals has a transient beneficial effect, but is detrimental in long-term. Reasonably the loss of Tfr2 increases the sensitivity of thalassemic erythroid cells to Epo stimulation (as we demonstrated for normal cells), favouring erythroid reconstitution after BMT. However, when erythropoiesis reaches a steady state, increased stimulation becomes deleterious. We propose that this occurs through high and persistent production of erythroferrone, the soluble factor released by the erythroblasts in order to inhibit the hepcidin expression. This would increase iron absorption and release, causing iron overload, further impairing the thalassemic erythropoiesis and generating a “thalassemia major-like phenotype” in Tfr2BMKO Hbbth3/+ mice. Further studies will better elucidate the mechanism of the observed biphasic effect on the phenotype and whether a time-controlled modulation of Tfr2 might improve β-thalassemia.
Session topic: Red blood cells and iron
Keyword(s): Erythropoieisis, Thalassemia, Transferrin receptor
Abstract: S133
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 11:30 - 11:45
Location: Hall C15
Background
Transferrin receptor 2 (TFR2) is a multifaceted protein that in the liver activates hepcidin, the master regulator of iron homeostasis, while in erythroid cells is a component of the erythropoietin (EPO) receptor complex. We have shown that the lack of Tfr2 in the bone marrow (BM) increases the EPO sensitivity of erythroid cells and mimics iron-deficiency (Nai et al., Blood 2015).β-thalassemias are recessive severe disorders of beta-globin gene, characterized by microcytic anemia, ineffective erythropoiesis, splenomegaly and secondary iron overload. Several studies demonstrated that iron restriction partially corrects the β-thalassemia phenotype in the Hbbth3/+ model of thalassemia intermedia.
Aims
In order to verify if the absence of Tfr2, mimicking iron-deficiency, could ameliorate the thalassemic phenotype we generated thalassemic animals with BM selective Tfr2 inactivation.
Methods
We generated thalassemic mice with (Hbbth3/+) or without BM Tfr2 (Tfr2BMKO/Hbbth3/+) by transplanting BM cells from Hbbth3/+ or Tfr2-/-/Hbbth3/+ mutants into lethally irradiated wild-type mice. Chimerism and hematological parameters were evaluated at 2 months. Mice were sacrificed 4 months after BM transplantation (BMT). At sacrifice blood was collected for hematological analysis, transferrin saturation (TS) and Epo levels; liver, spleen and BM cells were used for gene expression, tissue iron quantification, histology and flow cytometry analysis.
Results
Two months after BMT the engraftment of donor cells was 98-99%. Tfr2BMKO/Hbbth3/+ and Hbbth3/+ animals appear viable and indistinguishable from one another. Tfr2BMKO/Hbbth3/+ mice have greater red cells count and Hb levels as compared to Hbbth3/+ animals. On the contrary, 4 months after BMT Tfr2BMKO/Hbbth3/+ mice are smaller and more anemic than Hbbth3/+controls, have increased spleen size, TS and hepatic iron, but reduced spleen iron content. The alteration of body iron homeostasis is likely due to their lower hepcidin levels as compared with Hbbth3/+mice. The ineffective erythropoiesis is exacerbated in the absence of Tfr2 and results in extramedullary spleen and liver erythropoiesis. Anemia is accompanied by increased Epo gene trascription in the kidney and by increased expression of Epo target genes, such as Epor, Bcl-xL and erythroferrone (Erfe) in BM.
Conclusion
Deleting erythroid Tfr2 in Hbbth3/+ animals has a transient beneficial effect, but is detrimental in long-term. Reasonably the loss of Tfr2 increases the sensitivity of thalassemic erythroid cells to Epo stimulation (as we demonstrated for normal cells), favouring erythroid reconstitution after BMT. However, when erythropoiesis reaches a steady state, increased stimulation becomes deleterious. We propose that this occurs through high and persistent production of erythroferrone, the soluble factor released by the erythroblasts in order to inhibit the hepcidin expression. This would increase iron absorption and release, causing iron overload, further impairing the thalassemic erythropoiesis and generating a “thalassemia major-like phenotype” in Tfr2BMKO Hbbth3/+ mice. Further studies will better elucidate the mechanism of the observed biphasic effect on the phenotype and whether a time-controlled modulation of Tfr2 might improve β-thalassemia.
Session topic: Red blood cells and iron
Keyword(s): Erythropoieisis, Thalassemia, Transferrin receptor
Type: Oral Presentation
Presentation during EHA21: On Friday, June 10, 2016 from 11:30 - 11:45
Location: Hall C15
Background
Transferrin receptor 2 (TFR2) is a multifaceted protein that in the liver activates hepcidin, the master regulator of iron homeostasis, while in erythroid cells is a component of the erythropoietin (EPO) receptor complex. We have shown that the lack of Tfr2 in the bone marrow (BM) increases the EPO sensitivity of erythroid cells and mimics iron-deficiency (Nai et al., Blood 2015).β-thalassemias are recessive severe disorders of beta-globin gene, characterized by microcytic anemia, ineffective erythropoiesis, splenomegaly and secondary iron overload. Several studies demonstrated that iron restriction partially corrects the β-thalassemia phenotype in the Hbbth3/+ model of thalassemia intermedia.
Aims
In order to verify if the absence of Tfr2, mimicking iron-deficiency, could ameliorate the thalassemic phenotype we generated thalassemic animals with BM selective Tfr2 inactivation.
Methods
We generated thalassemic mice with (Hbbth3/+) or without BM Tfr2 (Tfr2BMKO/Hbbth3/+) by transplanting BM cells from Hbbth3/+ or Tfr2-/-/Hbbth3/+ mutants into lethally irradiated wild-type mice. Chimerism and hematological parameters were evaluated at 2 months. Mice were sacrificed 4 months after BM transplantation (BMT). At sacrifice blood was collected for hematological analysis, transferrin saturation (TS) and Epo levels; liver, spleen and BM cells were used for gene expression, tissue iron quantification, histology and flow cytometry analysis.
Results
Two months after BMT the engraftment of donor cells was 98-99%. Tfr2BMKO/Hbbth3/+ and Hbbth3/+ animals appear viable and indistinguishable from one another. Tfr2BMKO/Hbbth3/+ mice have greater red cells count and Hb levels as compared to Hbbth3/+ animals. On the contrary, 4 months after BMT Tfr2BMKO/Hbbth3/+ mice are smaller and more anemic than Hbbth3/+controls, have increased spleen size, TS and hepatic iron, but reduced spleen iron content. The alteration of body iron homeostasis is likely due to their lower hepcidin levels as compared with Hbbth3/+mice. The ineffective erythropoiesis is exacerbated in the absence of Tfr2 and results in extramedullary spleen and liver erythropoiesis. Anemia is accompanied by increased Epo gene trascription in the kidney and by increased expression of Epo target genes, such as Epor, Bcl-xL and erythroferrone (Erfe) in BM.
Conclusion
Deleting erythroid Tfr2 in Hbbth3/+ animals has a transient beneficial effect, but is detrimental in long-term. Reasonably the loss of Tfr2 increases the sensitivity of thalassemic erythroid cells to Epo stimulation (as we demonstrated for normal cells), favouring erythroid reconstitution after BMT. However, when erythropoiesis reaches a steady state, increased stimulation becomes deleterious. We propose that this occurs through high and persistent production of erythroferrone, the soluble factor released by the erythroblasts in order to inhibit the hepcidin expression. This would increase iron absorption and release, causing iron overload, further impairing the thalassemic erythropoiesis and generating a “thalassemia major-like phenotype” in Tfr2BMKO Hbbth3/+ mice. Further studies will better elucidate the mechanism of the observed biphasic effect on the phenotype and whether a time-controlled modulation of Tfr2 might improve β-thalassemia.
Session topic: Red blood cells and iron
Keyword(s): Erythropoieisis, Thalassemia, Transferrin receptor
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