Correcting β-thalassemia by combined therapies that restrict iron and modulate erythropoietin activity.
ß-thalassemia intermedia is a disorder characterized by ineffective erythropoiesis (IE), anemia, splenomegaly and systemic iron overload. Novel approaches are being explored based on the modulation of pathways that reduce iron absorption (i.e. using hepcidin activators like Tmprss6-antisense oligonucleotides (ASO)) or increase erythropoiesis (by erythropoietin (EPO) administration or by modulating the ability of transferrin receptor 2 (Tfr2) to control red blood cell (RBC) synthesis). Targeting Tmprss6 mRNA by Tmprss6-ASO was proven to be effective in improving the IE and splenomegaly by inducing iron restriction. However we postulated that combinatorial strategies might be superior to single therapies. Here we combined Tmprss6-ASO with EPO administration or removal of a single Tfr2 allele in the bone marrow of animals affected by ß-thalassemia intermedia (Hbbth3/+). EPO administration alone or removal of a single Tfr2 allele increased hemoglobin levels and RBCs. However, EPO or Tfr2 single allele deletion alone, respectively, exacerbated or did not improve the splenomegaly in ß-thalassemic mice. To overcome this issue, we postulated that some level of iron restriction (by targeting Tmprss6) would improve the splenomegaly while preserving the beneficial effects on RBC production mediated by EPO or Tfr2 deletion. While administration of Tmprss6-ASO alone improved the anemia, combination of Tmprss6-ASO+EPO or Tmprss6-ASO+Tfr2 single allele deletion showed significantly higher hemoglobin levels as well as reduction of splenomegaly. In conclusion, our results clearly indicate that these combinatorial approaches are superior to single treatments in ameliorating the IE and anemia in ß-thalassemia and could provide guidance to translate some of these approaches into viable therapies.