Improvement of mouse β-thalassemia by electrotransfer of erythropoietin cDNA

Objective A new intramuscular DNA electrotransfer method for erythropoietin (EPO) expression was evaluated in the natural mouse model of human β-thalassemia (Hbb-thal1) in terms of its ability to reverse the anemia and improve the thalassemic features of erythrocytes. Materials and Methods Intramuscular injection of small amounts of a plasmid encoding mouse EPO, immediately followed by controlled electric pulses, was used. Results This procedure induced very high hematocrit levels in β-thalassemic mice compared to nonelectrotransferred mice. The hematocrit increase was dose dependent, still increased 4 months after injection of plasmid DNA, and associated with a high transgenic EPO blood level in all mice (up to 2500 mU/mL of plasma). EPO gene electrotransfer not only led to a long-lasting and dose-dependent increase in the hematocrit but also to a 100% increase in the lifespan of erythrocytes of thalassemic mice. This was related to a nearly complete reestablishment of α/β globin chain balance, as demonstrated by a marked decrease in unpaired α globin chain. Eight months after the first electrotransfer of pCMV-mEPO plasmid, reinjection of the same construct raised the hematocrit to a level close to that observed following the first electrotransfer. Conclusion This is the first description of the use of plasmid DNA to achieve long-term improvement in a mouse model of a human genetic disorder.