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The goal of the present study was to analyze if sustained delivery of elevated doses of recombinant erythropoietin (Epo), by genetically modified and immunoprotected allogeneic cells, was able to correct the chronic anemia, characteristic of a spontaneous mouse model of β-thalassemia (Hbb thal 1). Mouse C2C12 myoblast cells were transfected with a plasmid containing the mouse Epo cDNA and a mutated dihydrofolate reductase (DHFR) gene for gene amplification upon administration of increasing doses of methotrexate. In order to immunoprotect the transplanted cells, the stably modified cells were loaded into polyethersulfone microporus hollow fibers which were implanted subcutaneously into Hbb thal 1 mice. An increase in hematocrit starting 2 weeks after implantation was associated with elevated blood levels of Epo and an improved red blood cell phenotype. The latter indicated an improvement of cell morphology and membrane defects, in particular a reduced amount of free α hemoglobin chain, the hallmark of globin chain imbalance in β-thalassemia. A reduction of reticulocyte count contrasting with the increase in hematocrit was also observed suggesting an improved erythrocyte survival. We conclude that the phenotype can be durably improved in some β-thalassemic mice upon in vivo delivery of recombinant Epo by polymer encapsulated cells. Sustained elevated delivery of recombinant Epo holds promise for the treatment of β-thalassemia-associated chronic anemia. [ABSTRACT FROM AUTHOR]

The erythopoietin (Epo) is a model of proteins expressed upon hypoxia, regulated at the transcriptional and post transcriptional levels. The Hypoxia Induced Factor (HIF-I) activates the transcription of genes which exhibit the Hypoxia Regulatory Element (HRE). In addition the mRNA is stabilized upon hypoxia, increasing the hormone synthesis. The Epo gene is a convenient reporter gene to develop gene delivery systems and the in vivo regulation of the transgene. The ß thalassemia and acquired chronic anemias may benefit from the Epo gene transfer and expression, if it becomes safe, tunable and inexpensive. [ABSTRACT FROM AUTHOR]