Fig. 2

Schematic representation of the possible recruitment and regulatory functions of monocyte. The entire healing process of an occurring fracture can be broadly divided into three main phases, i.e., the inflammatory phase, repair phase and the tissue regeneration phase, during which monocyte participate and regulate subsequent fracture repair. Fractures lead to the release of cellular signaling of chemokine to bone marrow, which triggering the release of monocyte from bone marrow through cellular signaling. During the inflammatory phase, inflammatory mediator cytokine and chemokine through chemoattractant recruit monocytes from the bone marrow to the site of injury and participate in the immune response by phagocytosing cellular debris and secreting proinflammatory cytokines (e.g., TNF, IL-1β, IL-6 and IL-12). Differentiate into M1 macrophages promote tissue regeneration in the early and middle stages without enhancing matrix mineralization. activated macrophage release growth factors, cytokines, enzyme to stabilize the regeneration process in the late repair phase, M2 (anti-inflammatory) macrophages release regenerative cytokines such as IL-10, TGF-β, BMP-2 and VEGF to establish an anti-inflammatory environment which promotes osteoclast genesis and bone healing