title: Macrophage-derived IL-33 is a critical factor for placental growth.
abstract: IL-33, the most recently discovered member of the IL-1 superfamily and ligand for the transmembrane form of ST2 (ST2L), has been linked to several human pathologies including rheumatoid arthritis, asthma, and cardiovascular disease. Deregulated levels of soluble ST2, the natural IL-33 inhibitor, have been reported in sera of preeclamptic patients. However, the role of IL-33 during healthy pregnancy remains elusive. In the current study, IL-33 was detected in the culture supernatants of human placental and decidual macrophages, identifying them as a major source of secreted IL-33 in the uteroplacental unit. Because flow cytometry and immunofluorescence stainings revealed membranous ST2L expression on specific trophoblast populations, we hypothesized that IL-33 stimulates trophoblasts in a paracrine manner. Indeed, BrdU incorporation assays revealed that recombinant human IL-33 significantly increased proliferation of primary trophoblasts as well as of villous cytotrophoblasts and cell column trophoblasts in placental explant cultures. These effects were fully abolished upon addition of soluble ST2. Interestingly, Western blot and immunofluorescence analyses demonstrated that IL-33 activates AKT and ERK1/2 in primary trophoblasts and placental explants. Inhibitors against PI3K (LY294002) and MEK1/2 (UO126) efficiently blocked IL-33-induced proliferation in all model systems used. In summary, with IL-33, we define for the first time, to our knowledge, a macrophage-derived regulator of placental growth during early pregnancy.
authors.affiliation: Reproductive Biology Unit, Department of Obstetrics and Fetal-Maternal Medicine, Medical University of Vienna, 1090 Vienna, Austria;
authors.forename: Valerie
authors.initials: V
authors.lastname: Fock
authors.forename: Mario
authors.initials: M
authors.lastname: Mairhofer
authors.forename: Gerlinde R
authors.initials: GR
authors.lastname: Otti
authors.forename: Ursula
authors.initials: U
authors.lastname: Hiden
authors.forename: Andreas
authors.initials: A
authors.lastname: Spittler
authors.forename: Harald
authors.initials: H
authors.lastname: Zeisler
authors.forename: Christian
authors.initials: C
authors.lastname: Fiala
authors.forename: Martin
authors.initials: M
authors.lastname: Knöfler
authors.forename: Jürgen
authors.initials: J
authors.lastname: Pollheimer
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D000072179:Interleukin-1 Receptor-Like 1 Protein; D000067596:Interleukin-33; D007378:Interleukins / Q000378:metabolism* / Q000494:pharmacology; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D010929:Placentation; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction; D046509:Tissue Culture Techniques; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism
chemical_list: C079241:IL1RL1 protein, human; C506536:IL33 protein, human; D000072179:Interleukin-1 Receptor-Like 1 Protein; D000067596:Interleukin-33; D007378:Interleukins; D018950:Lipopolysaccharide Receptors; D011956:Receptors, Cell Surface; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3