Identification of placental iron-regulatory hormones - PROJECT SUMMARY Iron is essential for a healthy pregnancy. During pregnancy, iron requirements increase substantially to support the development of the placenta and fetus as well as maternal blood cell volume expansion. Insufficient iron and ensuing iron deficiency anemia is linked to adverse pregnancy outcomes, including increased maternal mortality, perinatal death, and preterm birth. Hepcidin regulates systemic iron homeostasis by controlling dietary iron absorption, the release of iron from iron recycling macrophages, and the release of iron from hepatic stores. During pregnancy in humans and rodents, maternal hepcidin is profoundly suppressed, which is thought to maximize dietary iron absorption and mobilization of iron from stores for transfer to the developing fetus. Augmenting maternal hepcidin in mouse pregnancy by administration of hepcidin analogs led to severe embryo anemia or even death. Thus, maternal hepcidin suppression is essential for maternal and embryo iron homeostasis and health. Despite its importance, the mechanism(s) responsible for hepcidin suppression remain elusive. The goal of this project is to identify the pregnancy-related hepcidin suppressor. Specific Aim 1. Identify novel hepcidin regulators produced by the trophoblast – We identified over 600 proteins in our LC-MS/MS analysis of hepcidin suppressive fractions purified from human trophoblast supernatant and placental interstitial fluid. We will perform a high throughput cDNA overexpression screen of individual candidates to identify all proteins that modulate hepcidin expression in hepatocytes. Specific Aim 2. Investigate the role of HGF in hepcidin suppression during pregnancy – Our lab previously discovered that HGF suppresses hepcidin in vitro, but the physiological context for the role of HGF in iron metabolism was lacking. We now detected HGF in the placental LC-MS/MS screen and will characterize its role in hepcidin suppression in vitro and in vivo. In vitro, we will i) deplete HGF from suppressive trophoblast-derived conditioned media and placental interstitial fluid and ii) inhibit HGF signaling in hepatocytes treated with trophoblast media and placental interstitial fluid, and in each case assess their ability to suppress hepcidin. In vivo, we will i) measure HGF concentrations and the proportion of pro- HGF and mature-HGF in maternal circulation across gestation and ii) inhibit HGF receptor MET at the gestational age when maternal hepcidin suppression is initiated and assess hepcidin suppression and serum iron changes. When completed, these studies will provide fundamental insight into the regulation of iron homeostasis during and even outside of pregnancy, with broad translational potential for treatment of iron disorders.
