title: Resting and injury-induced inflamed periosteum contain multiple macrophage subsets that are located at sites of bone growth and regeneration.
abstract: Better understanding of bone growth and regeneration mechanisms within periosteal tissues will improve understanding of bone physiology and pathology. Macrophage contributions to bone biology and repair have been established but specific investigation of periosteal macrophages has not been undertaken. We used an immunohistochemistry approach to characterize macrophages in growing murine bone and within activated periosteum induced in a mouse model of bone injury. Osteal tissue macrophages (osteomacs) and resident macrophages were distributed throughout resting periosteum. In tissues collected from 4-week-old mice, osteomacs were observed intimately associated with sites of periosteal diaphyseal and metaphyseal bone dynamics associated with normal growth. This included F4/80+Mac-2-/lowosteomac association with extended tracks of bone formation (modeling) on diphyseal periosteal surfaces. Although this recapitulated endosteal osteomac characteristics, there was subtle variance in the morphology and spatial organization of periosteal modeling-associated osteomacs, which likely reflects the greater structural complexity of periosteum. Osteomacs, resident macrophages and inflammatory macrophages (F4/80+Mac-2hi) were associated with the complex bone dynamics occurring within the periosteum at the metaphyseal corticalization zone. These three macrophage subsets were also present within activated native periosteum after bone injury across a 9-day time course that spanned the inflammatory through remodeling bone healing phases. This included osteomac association with foci of endochondral ossification within the activated native periosteum. These observations confirm that osteomacs are key components of both osteal tissues, in spite of salient differences between endosteal and periosteal structure and that multiple macrophage subsets are involved in periosteal bone dynamics.
authors.affiliation: The University of Queensland, Institute for Molecular Bioscience, St Lucia, Queensland, Australia.|The University of Queensland Centre for Clinical Research, Faculty of Medicine and Biomedical Sciences, Royal Brisbane Hospital, Herston, Queensland, Australia.
authors.forename: Kylie Anne
authors.initials: KA
authors.lastname: Alexander
authors.affiliation: The University of Queensland, Institute for Molecular Bioscience, St Lucia, Queensland, Australia.|The University of Queensland Centre for Clinical Research, Faculty of Medicine and Biomedical Sciences, Royal Brisbane Hospital, Herston, Queensland, Australia.|Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors.forename: Liza-Jane
authors.initials: LJ
authors.lastname: Raggatt
authors.affiliation: Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Millard
authors.affiliation: Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors.forename: Lena
authors.initials: L
authors.lastname: Batoon
authors.affiliation: The University of Queensland, Institute for Molecular Bioscience, St Lucia, Queensland, Australia.|The University of Queensland Centre for Clinical Research, Faculty of Medicine and Biomedical Sciences, Royal Brisbane Hospital, Herston, Queensland, Australia.
authors.forename: Andy
authors.initials: A
authors.lastname: Chiu-Ku Wu
authors.affiliation: The University of Queensland, Institute for Molecular Bioscience, St Lucia, Queensland, Australia.
authors.forename: Ming-Kang
authors.initials: MK
authors.lastname: Chang
authors.affiliation: The University of Queensland, Institute for Molecular Bioscience, St Lucia, Queensland, Australia.|The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin, Midlothian EH25 9PS, Scotland, UK.
authors.forename: David Arthur
authors.initials: DA
authors.lastname: Hume
authors.affiliation: The University of Queensland, Institute for Molecular Bioscience, St Lucia, Queensland, Australia.|The University of Queensland Centre for Clinical Research, Faculty of Medicine and Biomedical Sciences, Royal Brisbane Hospital, Herston, Queensland, Australia.|Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba, Queensland, Australia.
authors.forename: Allison Robyn
authors.initials: AR
authors.lastname: Pettit
mesh_terms: D000818:Animals; D001846:Bone Development; D001861:Bone Regeneration; D007249:Inflammation / Q000473:pathology; D008262:Macrophage Activation; D008264:Macrophages / Q000473:pathology*; D008297:Male; D008810:Mice, Inbred C57BL; D010012:Osteogenesis; D010521:Periosteum / Q000473:pathology*; D014945:Wound Healing