Unlike other tissues, bone has the unique capacity to heal bony injuries without fibrous scar formation via its regeneration process and therefore maintains physiological and mechanical characteristics. This continuous and well-orchestrated regeneration process is also critical for the upkeep of calcium homeostasis throughout the lifetime. Stimulating bone regeneration is the central aim in orthopedic surgery and in oral and maxillofacial surgery, in order to overcome large bone defects and to cure metabolic/inflammatory bone diseases. Although tissue-engineered materials or artificial bone can help to retain bone stability, biocompatibility and bioresorbability are still significant obstacles for biomaterials to overcome in order to sync with the natural regeneration process.

During recent decades, advances in this field have begun to reveal various regulatory molecules shared by the immune system and skeletal system, which depict interesting crosstalk of signaling transducers between immune cells and bone cells. Therefore, osteoimmunology has developed as an essential interdisciplinary field underlying major discoveries concerning bone regeneration and developing targeted therapies for bone diseases.

This special issue aims to provide a better understanding of the crosstalk between the immune system and the skeletal system during bone regeneration. Investigators are invited to contribute original research articles focusing on the novel mechanisms or clinical pathogenesis that provide insight into the complex interplay of immune cells with bone cells under physiological or pathological scenarios. Review articles describing the current state of the art within the field are also welcomed.

Potential topics include but are not limited to the following:

• New discoveries or perspectives of intercellular communication between immune cells and bone cells in bone fracture healing
• The interplay between immune cells and bone cells in metabolic/inflammatory bone diseases
• Effects of the immune response to the bone tumor on bone remodeling
• Immune control in bone regeneration after implantation of biomaterials
• Immune factors mediating angiogenesis in bone regeneration
• Meta-analysis of immunological risk factors for metabolic/inflammatory bone diseases