title: Toll-like receptor-3-activated human mesenchymal stromal cells significantly prolong the survival and function of neutrophils.
abstract: Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are stromal precursors endowed with extensive immunomodulative properties. In this study, we aimed to assess whether Toll-like receptor-3 (TLR3)- and TLR4-activated BM-MSC influence human neutrophil (PMN) responses under coculture conditions. We show that TLR3 triggering by polyinosinic:polycytidylic acid dramatically amplifies, in a more significant manner than TLR4 triggering by lipopolysaccharide, the antiapoptotic effects that resting BM-MSC constitutively exert on PMN under coculture conditions, preserving a significant fraction of viable and functional PMN up to 72 hours. In addition, TLR3- and TLR4-activated BM-MSC enhance respiratory burst ability and CD11b expression by PMN. The coculture in the absence of cell contact and the incubation of PMN in supernatants harvested from TLR3- and TLR4-activated BM-MSC yield comparable results in terms of increased survival and immunophenotypic changes, thus suggesting the involvement of endogenous soluble factors. Neutralizing experiments reveal that the biological effects exerted on PMN by TLR3-activated BM-MSC are mediated by the combined action of interleukin 6, interferon-β (IFN-β), and granulocyte macrophage colony-stimulating factor (GM-CSF), while those exerted by TLR4-activated BM-MSC mostly depend on GM-CSF. MSC isolated from thymus, spleen, and subcutaneous adipose tissue behaves similarly. Finally, the effects exerted by TLR3- or TLR4-stimulated BM-MSC on PMN are conserved even after the previous priming of BM-MSC with IFN-γ and tumor necrosis factor-α. Our data highlight a novel mechanism by which MSC sustain and amplify the functions of PMN in response to TLR3- and TLR4-triggering and may consequently contribute to inflammatory disorders.
authors.affiliation: Section of General Pathology, Department of Pathology and Diagnostics, University of Verona, Italy. marco.cassatella@univr.it
authors.forename: Marco A
authors.initials: MA
authors.lastname: Cassatella
authors.forename: Federico
authors.initials: F
authors.lastname: Mosna
authors.forename: Alessandra
authors.initials: A
authors.lastname: Micheletti
authors.forename: Veronica
authors.initials: V
authors.lastname: Lisi
authors.forename: Nicola
authors.initials: N
authors.lastname: Tamassia
authors.forename: Caterina
authors.initials: C
authors.lastname: Cont
authors.forename: Federica
authors.initials: F
authors.lastname: Calzetti
authors.forename: Martin
authors.initials: M
authors.lastname: Pelletier
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pizzolo
authors.forename: Mauro
authors.initials: M
authors.lastname: Krampera
mesh_terms: D001854:Bone Marrow Cells / Q000166:cytology; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D018920:Coculture Techniques; D017077:Culture Media, Conditioned; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism; D006801:Humans; D016899:Interferon-beta / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D010641:Phenotype; D011070:Poly I-C / Q000494:pharmacology; D051196:Toll-Like Receptor 3 / Q000819:agonists / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D017077:Culture Media, Conditioned; D015850:Interleukin-6; D008070:Lipopolysaccharides; D051196:Toll-Like Receptor 3; D014409:Tumor Necrosis Factor-alpha; D016179:Granulocyte Colony-Stimulating Factor; D016899:Interferon-beta; D007371:Interferon-gamma; D011070:Poly I-C