title: Proinflammatory M1 Macrophages Inhibit RANKL-Induced Osteoclastogenesis.
abstract: In response to a defined panel of stimuli, immature macrophages can be classified into two major phenotypes: proinflammatory (M1) and anti-inflammatory (M2). Although both phenotypes have been implicated in several chronic inflammatory diseases, their direct role in bone resorption remains unclear. The present study investigated the possible effects of M1 and M2 macrophages on RANKL-induced osteoclastogenesis. In osteoclastogenesis assays using RAW264.7 cells or bone marrow cells as osteoclast precursors, addition of M1 macrophages significantly suppressed RANKL-induced osteoclastogenesis compared to nonstimulated conditions (M0), addition of M2 macrophages, or no macrophage addition (P < 0.05), suggesting that M1 macrophages can downregulate osteoclastogenesis. This effect was maintained when direct contact between M1 and osteoclast precursors was interrupted by cell culture insertion, indicating engagement of soluble factors released from M1. M1 macrophages developed from interferon gamma (IFN-γ) knockout (IFN-γ-KO) mice lost the ability to downregulate osteoclastogenesis. Antibody-based neutralization of interleukin-12 (IL-12), but not IL-10, produced by M1 macrophages also abrogated M1-mediated downregulation of osteoclastogenesis. Real-time PCR analyses showed that IFN-γ suppressed gene expression of NFATc1, a master regulator of osteoclastogenesis, whereas IL-12 increased the apoptosis of osteoclasts, suggesting molecular mechanisms underlying the possible roles of IFN-γ or IL-12 in M1-mediated inhibition of osteoclastogenesis. These findings were confirmed in an in vivo ligature-induced mouse periodontitis model in which adoptive transfer of M1 macrophages showed a significantly lower level of bone loss and less tartrate-resistant acid phosphatase (TRAP)-positive cell induction than M0 or M2 macrophage transfer. In conclusion, by its secretion of IFN-γ and IL-12, M1, but not M0 or M2, was demonstrated to inhibit osteoclastogenesis.
authors.affiliation: The Forsyth Institute, Cambridge, Massachusetts, USA Research and Development Headquarters, LION Corporation, Kanagawa, Japan.
authors.forename: Tsuguno
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: The Forsyth Institute, Cambridge, Massachusetts, USA.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Movila
authors.affiliation: Research and Development Headquarters, LION Corporation, Kanagawa, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kataoka
authors.affiliation: The Forsyth Institute, Cambridge, Massachusetts, USA Harvard School of Dental Medicine, Boston, Massachusetts, USA.
authors.forename: Wichaya
authors.initials: W
authors.lastname: Wisitrasameewong
authors.affiliation: The Forsyth Institute, Cambridge, Massachusetts, USA.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Ruiz Torruella
authors.affiliation: Research and Development Headquarters, LION Corporation, Kanagawa, Japan.
authors.forename: Michiaki
authors.initials: M
authors.lastname: Murakoshi
authors.affiliation: Department of Periodontology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Murakami
authors.affiliation: The Forsyth Institute, Cambridge, Massachusetts, USA Harvard School of Dental Medicine, Boston, Massachusetts, USA tkawai@forsyth.org.
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Kawai
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001854:Bone Marrow Cells; D002454:Cell Differentiation; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D010010:Osteoclasts / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D010518:Periodontitis / Q000503:physiopathology; D016133:Polymerase Chain Reaction / Q000379:methods; D053245:RANK Ligand / Q000502:physiology*; D000071681:Tartrate-Resistant Acid Phosphatase / Q000378:metabolism
chemical_list: D053245:RANK Ligand; D018664:Interleukin-12; D007371:Interferon-gamma; D000071681:Tartrate-Resistant Acid Phosphatase