Iron Pathobiology in β-thalassemia Pregnancy

项目总结

PROJECT SUMMARY Iron overload is a major cause of morbidity and mortality in iron-loading anemias, such as β-thalassemia. Iron overload develops due to inappropriately low production of the iron-regulatory hormone hepcidin, resulting in elevated intestinal iron absorption. Blood transfusions further exacerbate iron loading. Pregnancy is a natural condition in which iron homeostasis is altered to meet increased iron demands associated with expansion of maternal erythropoiesis and fetal development. Although iron metabolism has been extensively investigated in healthy pregnancy, how it is altered in thalassemic pregnancy and to what extent iron overload contributes to adverse pregnancy outcomes is unknown. Patients with β-thalassemia are increasingly able to bear children, however, these pregnancies are considered high risk. Investigation in this area is thus of clinical significance. Here, a pre-clinical animal model of β-thalassemia (Th3/+ mice) was studied to define pathophysiological outcomes associated with pregnancy. Key pilot data demonstrated that thalassemia leads to highly disordered maternal and fetal iron homeostasis. Compared to wild-type (WT) dams, thalassemic mothers were iron-loaded and had altered systemic iron handling. High serum iron in dams precipitated in utero iron loading of placentas and WT and Th3/+ fetuses. Iron loading in turn altered the fetal iron-regulatory system. This initial characterization of thalassemic pregnancy will be expanded upon in this investigation, and generation of new mouse models that will accelerate novel discovery. In Aim 1, the hypothesis that maternal factors cause fetal iron imbalance in thalassemic pregnancy will be tested. The approach is to quantify biomarkers of iron, oxygen and hematological status, and the degree of fetal iron loading, throughout pregnancy. Additional experimentation will define whether the iron-regulatory hormone erythroferrone (ERFE), blood transfusions, and maternal anemia/hypoxia impact fetal iron homeostasis. In Aim 2, the hypothesis that fetal iron loading in thalassemic pregnancies exacerbates development of pre- and postnatal pathologies will be considered. The approach includes examination of biomarkers of oxidative stress in dams, placentas, and fetuses throughout pregnancy and during postnatal development. Placental and fetal endothelial cell injury will also be assessed. Effects on DNA will be evaluated by assaying for global epigenetic changes and mutational burden. Physiological phenotyping will include detailed analysis of cognitive and renal function. In Aim 3, the hypothesis that lowering serum iron in Th3/+ dams will prevent fetal iron loading will be tested. Two approaches will be utilized: peroral delivery of nanoparticle/siRNA complexes to blunt expression of the main intestinal iron transporter DMT1 (to block iron absorption); and systemic administration of hepcidin mimetics (to decrease iron absorption and release of storage iron). Both approaches are expected to lower serum iron, thus decreasing placental iron transfer. This investigation will delineate pathophysiological changes associated with thalassemic pregnancy and define molecular pathways that could be targeted to mitigate fetal iron loading, thus diminishing lifelong disease burden.