beta Minor-globin messenger RNA accumulation in reticulocytes governs improved erythropoiesis in beta 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 beta thalas semic C57Bl/6(Hbbth) mice. Naked DNA encoding an expression vector for mous e Epo was introduced into skeletal muscles by electrotransfer. A transient increase of serum Epo concentrations with a proportional augmentation of he matocrit values was observed. Various parameters relevant to beta thalassem ia were surveyed in blood samples taken before treatment, at the peak of Ep o secretion, and when the phenotype reverted to anemia. We measured globin messenger RNA (mRNA) levels in reticulocytes by real-time quantitative poly merase chain reaction, globin chain synthesis levels, and several indicator s of erythrocyte membrane quality, including bound alpha chains, bound immu noglobulins, main protein components, and iron compartmentalization. Data i ndicated that high serum Epo levels primarily affect beta minor-globin mRNA accumulation in reticulocytes. Other changes subsequent to intense Epo sti mulation, like increased beta minor/alpha -globin chain synthesis ratio, re duced levels of alpha chains and immunoglobulins bound to membranes, improv ed spectrin/band 3 ratio, increased red blood cell survival, and improved e rythropoiesis appeared as consequences of increased beta minor-globin mRNA levels. This conclusion is consistent with models postulating that intense Epo stimulation induces the expansion and differentiation of erythroid prog enitors committed to fetal erythropoiesis. Although phenotypic correction w as partial in mice, and comparable achievements will probably be more diffi cult 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 feta l erythropoiesis reactivation in patients with beta thalassemia. (Blood. 20 01;97:2213-2220) (C) 2001 by The American Society of Hematology.