Changes in Macrophageand Inflammatory Cytokine Expressions During Fracture Healing in an Ovariectomized Mice Model

Abstract Background: Macrophages and inflammatory cytokines plays important roles in bone fracture healing. However, the expression patterns of macrophages and inflammatory cytokines during fracture healing under the condition of postmenopausal osteoporosis has not been fully revealed.Methods:Tibia transversefracture was established 12 weeks after ovariectomyor shamoperation in 3-month old female mice. Tibias were harvested before fracture or 1, 3, 5, 7, 14, 21, 28 days after fracture for radiological and histological examinations. M1/M2 inflammatorymacrophages, ostealmacrophages and gene expressions of tumor necrosis factor-α,interleukin-6, interleukin-1βand macrophage conversion related molecules in the fracturehaematoma or callus were also detected.Results:The process of fracture healing,especially the phases of endochondral ossification and callus remodeling, was delayed in ovariectomized mice.The expressions of tumor necrosis factor-α andinterleukin-6, but not interleukin-1β, in the fracturehaematoma or callus were disturbed. We also foundthe decreases in M1 and M2 macrophages inthe initialinflammatory stage, M2 macrophagesin the middle stage and ostealmacrophagesin the middle and late stages of fracture healing in ovariectomized mice.Conclusions: The expressions of macrophages and inflammatory cytokines were impaired in ovariectomized mice, which might contribute partially to poor fracture healing.