Bones are an integral part of our skeleton and provide a frame, protection and stability for our organism. Bones are dynamic tissues and turnover occurs constantly at homeostasis and is impaired in various conditions including aging, pregnancy and metabolic disease, leading to a high risk for fracture and impaired bone healing. We have shown (Schaupp, Cell 2020) that innate cell-derived cytokines such as type I interferons are regulated by the microbiota and control the metabolism and function of a wide range of mononuclear phagocytes (e.g., dendritic cells, microglia, macrophages). Osteoclasts are bone-resorbing macrophages, but the contribution of such pathways to bone regeneration remains unknown. In addition, we have investigated mechanisms by which TNF regulates osteoclast formation by controlling the pre-osteoclast pool. How innate cell-derived cytokines control the ability of osteoclast precursors to form osteoclasts remains largely unknown. To address this, we systematically investigate the role of innate cytokines and the microbiota as regulators of osteoclastogenesis. A second line of research interrogates how mononuclear phagocyte subsets and tissue-resident innate lymphoid cells (ILCs) regulate the pre-osteoclast pool, thus modulating bone homeostasis or bone repair. Finally, we are investigating the role of ILC in the small intestine for the uptake of nutrients and salts that are needed for bone homeostasis at steady-state but also during pregnancy, a state of hightened bone metabolism. Our goal is to unravel how innate and microbiota-dependent pathways control bone regeneration at homeostasis, in pregnancy and in the context of compromised healing.