Effects of macrophage activation on bone healing

In this study the effect of macrophage activation on bone healing was investigated in rats. In three groups of rats, an osteotomy of the femoral bone was performed and then nailed. Macrophages were activated by semisoluble aminated glucan. In one group of animals this was applied locally, in another group it was applied systemically (intraperitoneally), and the third group served as control. Eight rats in each group were killed after 4, 8, and 12 weeks, and the mechanical characteristics of the healing osteotomies were evaluated. We found that local activation of macrophages induced an immature hypertrophic callus with reduced biomechanical characteristics, as evaluated by bending moment, rigidity, and energy absorption. There were no significant differences between the rats subjected to systemic macrophage activation and the control rats. We conclude that local macrophage activation during the initial phase of bone repair impairs healing.