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Angiocrine Bmp2 signaling in murine liver controls normal iron homeostasis

Philipp-Sebastian Koch, Victor Olsavszky, Friederike Ulbrich, Carsten Sticht, Alexandra Demory, Thomas Leibing, Thomas Henzler, Mathias Meyer, Johanna Zierow, Sven Schneider, Katja Breitkopf-Heinlein, Haristi Gaitantzi, Bradley Spencer-Dene, Bernd Arnold, Kay Klapproth, Kai Schledzewski, Sergij Goerdt and Cyrill Géraud

Key points

  • Angiocrine Bmp2 signaling in the liver controls tissue and serum iron concentrations via regulation of hepcidin expression in hepatocytes.

  • Liver-specific angiocrine signaling is essential for the metabolic homeostasis of the whole organism.

Abstract

Microvascular endothelial cells (EC) display a high degree of phenotypic and functional heterogeneity among different organs. Organ-specific EC control their tissue microenvironment by angiocrine factors in health and disease. Liver sinusoidal EC (LSEC) are uniquely differentiated to fulfil important organ-specific functions in development, under homeostatic conditions, and in regeneration and liver pathology. Recently, Bmp2 has been identified by us as an organ-specific angiokine derived from LSEC. To study angiocrine Bmp2 signaling in the liver, we conditionally deleted Bmp2 in LSEC using EC subtype-specific Stab2-Cre mice. Genetic inactivation of hepatic angiocrine Bmp2 signaling in Stab2-Cre;Bmp2fl/fl (Bmp2LSECKO) mice caused massive iron overload in the liver, and increased serum iron levels and iron deposition in several organs similar to classic hereditary hemochromatosis. Iron overload was mediated by decreased hepatic expression of hepcidin, a key regulator of iron homeostasis. Thus, angiocrine Bmp2 signaling within the hepatic vascular niche represents a constitutive pathway indispensable for iron homeostasis in vivo that is non-redundant with Bmp6. Notably, we demonstrate that organ-specific angiocrine signaling is essential not only for the homeostasis of the respective organ, but also for the homeostasis of the whole organism.

  • Submitted July 25, 2016.
  • Accepted November 23, 2016.