Thu, 21 Aug 2008 16:11:14 BST CiteULike: Author Fazzalari http://www.citeulike.org/author/Fazzalari CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/ajaymalik/article/2973294 <i>J Immunol, Vol. 181, No. 2. (15 July 2008), pp. 1232-1244.</i><br /><br />Resident macrophages are an integral component of many tissues and are important in homeostasis and repair. This study examines the contribution of resident tissue macrophages to bone physiology. Using immunohistochemistry, we showed that a discrete population of resident macrophages, OsteoMacs, was intercalated throughout murine and human osteal tissues. OsteoMacs were distributed among other bone lining cells within both endosteum and periosteum. Furthermore, OsteoMacs were coisolated with osteoblasts in murine bone explant and calvarial preparations. OsteoMacs made up 15.9% of calvarial preparations and persisted throughout standard osteoblast differentiation cultures. Contrary to previous studies, we showed that it was OsteoMacs and not osteoblasts within these preparations that responded to pathophysiological concentrations of LPS by secreting TNF. Removal of OsteoMacs from calvarial cultures significantly decreased osteocalcin mRNA induction and osteoblast mineralization in vitro. In a Transwell coculture system of enriched osteoblasts and macrophages, we demonstrated that macrophages were required for efficient osteoblast mineralization in response to the physiological remodeling stimulus, elevated extracellular calcium. Notably, OsteoMacs were closely associated with areas of bone modeling in situ, forming a distinctive canopy structure covering >75% of mature osteoblasts on diaphyseal endosteal surfaces in young growing mice. Depletion of OsteoMacs in vivo using the macrophage-Fas-induced apoptosis (MAFIA) mouse caused complete loss of osteoblast bone-forming surface at this modeling site. Overall, we have demonstrated that OsteoMacs are an integral component of bone tissues and play a novel role in bone homeostasis through regulating osteoblast function. These observations implicate OsteoMacs, in addition to osteoclasts and osteoblasts, as principal participants in bone dynamics. Osteal Tissue Macrophages Are Intercalated throughout Human and Mouse Bone Lining Tissues and Regulate Osteoblast Function In Vitro and In Vivo Ming Chang Liza-Jane Raggatt Kylie Alexander Julia Kuliwaba Nicola Fazzalari Kate Schroder Erin Maylin Vera Ripoll David Hume Allison Pettit J Immunol, Vol. 181, No. 2. (15 July 2008), pp. 1232-1244. 2008-07-08T19:53:50-00:00 2008 J Immunol 181 2 1232 1244 osteomacs http://www.citeulike.org/user/heliopais/article/1714002 <i>Arthritis Research & Therapy, Vol. 9 (27 September 2007), R100.</i> Microarray gene expression profiling of human osteoarthritic bone suggests altered bone remodelling, WNT and TGF beta/BMP signalling Blair Hopwood Anna Tsykin David Findlay Nicola Fazzalari doi:10.1186/ar2301 Arthritis Research & Therapy, Vol. 9 (27 September 2007), R100. 2007-10-01T06:39:53-00:00 2007 Arthritis Research & Therapy 1478-6354 9 R100 bone_formation microarray