New insights about close connection between skeletal and immune systems have expanded vistas of modern medicine and tissue engineering. Intensive progress of osteoimmunology enabled the understanding of processes related to bone tissue from a completely new angle, both in physiological and pathological conditions. In this respect, macrophages stand out as cells which affect bone through the ability to secrete a range of different cytokines. Macrophages’ activation is directed by environmental conditions which determine the phenotype and function of these cells. Acquired phenotypic and functional characteristics of macrophages are changed according to changes in their environment. Thanks to these abilities, macrophages have great impact on bone development, bone homeostasis and osteoreparatory process. During bone development, macrophages can affect osteoblast differentiation and matrix mineralization. Coordinated action of osteoclasts and osteoblasts is important in bone tissue remodeling process. Also, during osteoreparation macrophages are among the first cells that will come to the site of bone injury. Their impact on bone is particularly visible during inflammatory phase of fracture healing. Better understanding of mechanisms by which macrophages exert their influence on bone would be an important step in approach to more specific therapies that would modulate activity of these cells and might accelerate healing of bone defects
