OsteoMacs: Key regulators of bone biology and emerging therapeutic perspectives

The bone is an active tissue subjected to ongoing remodeling process regulated through a fine-tuned equilibrium between formation and resorption and is mainly regulated by osteoblasts, osteoclasts, and osteocytes. Recent developments have identified the essential importance of Osteal Macrophages (OsteoMacs), a unique subset of tissue-resident macrophages, in bone homeostasis. In contrast to osteoclasts, the mononuclear F4/80⁺ OsteoMacs are non-resorbing cells that promote osteoblast function, preserve the structure of the bone remodeling canopy, and regulate local immune responses of the skeletal microenvironment. This review was designed to summarize the uncovering, source, phenotypic characteristic as well as functional role of OsteoMacs in bone remodeling, osseointegration, and response to biomaterials. Knowledge of the cross talk between OsteoMacs and biomaterials provides new opportunities to improve bone regeneration via specific immunomodulation. OsteoMacs therefore, serve as a critical interface between the skeletal and immune systems; and have large relevance in implantology and regenerative medicine.