title: GM-CSF Inhibits c-Kit and SCF Expression by Bone Marrow-Derived Dendritic Cells.
abstract: Stem cell factor (SCF), the ligand of c-kit, is a key cytokine for hematopoiesis. Hematopoietic precursors express c-kit, whereas differentiated cells of hematopoietic lineage are negative for this receptor, with the exception of NK cells, mast cells, and a few others. While it has long been recognized that dendritic cells (DCs) can express c-kit, several questions remain concerning the SCF/c-kit axis in DCs. This is particularly relevant for DCs found in those organs wherein SCF is highly expressed, including the bone marrow (BM). We characterized c-kit expression by conventional DCs (cDCs) from BM and demonstrated a higher proportion of c-kit+cells among type 1 cDC subsets (cDC1s) than type 2 cDC subsets (cDC2s) in both humans and mice, whereas similar levels of c-kit expression were observed in cDC1s and cDC2s from mouse spleen. To further study c-kit regulation, DCs were generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) from mouse BM, a widely used protocol. CD11c+cells were purified from pooled non-adherent and slightly adherent cells collected after 7 days of culture, thus obtaining highly purified BM-derived DCs (BMdDCs). BMdDCs contained a small fraction of c-kit+cells, and by replating them for 2 days with GM-CSF, we obtained a homogeneous population of c-kit+CD40hiMHCIIhicells. Not only did BMdDCs express c-kit but they also produced SCF, and both were striking upregulated if GM-CSF was omitted after replating. Furthermore, a small but significant reduction in BMdDC survival was observed upon SCF silencing. Incubation of BMdDCs with SCF did not modulate antigen presentation ability of these cells, nor it did regulate their membrane expression of the chemokine receptor CXCR4. We conclude that the SCF/c-kit-mediated prosurvival circuit may have been overlooked because of the prominent use of GM-CSF in DC culturesin vitro, including those human DC cultures destined for the clinics. We speculate that DCs more prominently rely on SCFin vivoin some microenvironments, with potential implications for graft-versus-host disease and antitumor immunity.
authors.affiliation: Institute of Molecular Biology and Pathology, National Research Council (CNR), c/o Department of Molecular Medicine, University of Rome "Sapienza", Rome, Italy; Department of Molecular Medicine, University of Rome "Sapienza", Rome, Italy.
authors.forename: Amairelys Belen
authors.initials: AB
authors.lastname: Barroeta Seijas
authors.affiliation: Department of Molecular Medicine, University of Rome "Sapienza" , Rome , Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Simonetti
authors.affiliation: Institute of Molecular Biology and Pathology, National Research Council (CNR), c/o Department of Molecular Medicine, University of Rome "Sapienza" , Rome , Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Vitale
authors.affiliation: Istituto Pasteur Italia - Fondazione Cenci Bolognetti , Rome , Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Runci
authors.affiliation: Department of Molecular Medicine, University of Rome "Sapienza" , Rome , Italy.
authors.forename: Angela Caterina
authors.initials: AC
authors.lastname: Quinci
authors.affiliation: Department of Molecular Medicine, University of Rome "Sapienza" , Rome , Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Soriani
authors.affiliation: Department of Molecular and Developmental Medicine, University of Siena , Siena , Italy.
authors.forename: Mattia
authors.initials: M
authors.lastname: Criscuoli
authors.affiliation: Department of Molecular and Developmental Medicine, University of Siena , Siena , Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Filippi
authors.affiliation: Department of Molecular and Developmental Medicine, University of Siena , Siena , Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Naldini
authors.affiliation: Centro Traumatologico Ortopedico Andrea Alesini Hospital , Rome , Italy.
authors.forename: Federico Maria
authors.initials: FM
authors.lastname: Sacchetti
authors.affiliation: Department of Orthopaedics and Traumatology, University of Rome "Tor Vergata" , Rome , Italy.
authors.forename: Umberto
authors.initials: U
authors.lastname: Tarantino
authors.affiliation: Department of Orthopaedics and Traumatology, University of Rome "Tor Vergata" , Rome , Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Oliva
authors.affiliation: Department of Orthopaedics and Traumatology, University of Rome "Tor Vergata" , Rome , Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Piccirilli
authors.affiliation: Department of Molecular Medicine, University of Rome "Sapienza", Rome, Italy; Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Rome, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Santoni
authors.affiliation: Institute of Molecular Biology and Pathology, National Research Council (CNR), c/o Department of Molecular Medicine, University of Rome "Sapienza" , Rome , Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Rosa
keywords: GM-CSF; bone marrow; bone marrow-derived dendritic cells; conventional dendritic cell subsets; dendritic cell homeostasis; dendritic cell survival; stem cell factor