βMinor-globin messenger RNA accumulation in reticulocytes governs improved erythropoiesis in β thalassemic mice after erythropoietin complementary DNA electrotransfer in muscles

Mechanisms governing the induction of effective erythropoiesis in response to erythropoietin (Epo) oversecretion have been investigated in β thalassemic C57Bl/6Hbbth mice. Naked DNA encoding an expression vector for mouse Epo was introduced into skeletal muscles by electrotransfer. A transient increase of serum Epo concentrations with a proportional augmentation of hematocrit values was observed. Various parameters relevant to β thalassemia were surveyed in blood samples taken before treatment, at the peak of Epo secretion, and when the phenotype reverted to anemia. We measured globin messenger RNA (mRNA) levels in reticulocytes by real-time quantitative polymerase chain reaction, globin chain synthesis levels, and several indicators of erythrocyte membrane quality, including bound α chains, bound immunoglobulins, main protein components, and iron compartmentalization. Data indicated that high serum Epo levels primarily affect βminor-globin mRNA accumulation in reticulocytes. Other changes subsequent to intense Epo stimulation, like increased βminor/α-globin chain synthesis ratio, reduced levels of α chains and immunoglobulins bound to membranes, improved spectrin/band 3 ratio, increased red blood cell survival, and improved erythropoiesis appeared as consequences of increased βminor-globin mRNA levels. This conclusion is consistent with models postulating that intense Epo stimulation induces the expansion and differentiation of erythroid progenitors committed to fetal erythropoiesis. Although phenotypic correction was partial in mice, and comparable achievements will probably be more difficult to obtain in humans, naked DNA electrotransfer may provide a safe and low-cost method for reassessing the potentials of Epo as an inducer of fetal erythropoiesis reactivation in patients with β thalassemia.