Bone repair: Effects of physical exercise and LPS systemic exposition

Bone repair can be facilitated by grafting, biochemical and physical stimulation. Conversely, it may be delayed lipopolysaccharide (LPS). Physical exercise exerts beneficial effects on the bone, but its effect on bone repair is not known. We investigated the effect of exercise on the LPS action on bone healing through bone densitometry, quantitative histological analysis for bone formation rate and immunohistochemical markers in sedentary and exercised animals. Rats ran on the treadmill for four weeks. After training the rats were submitted to a surgical procedure (bone defect in the right tibia) and 24h after the surgery LPS was administered at a dose of 100μg/kg i.p., whereas the control rats received a saline injection (1ml/kg, i.p.). Right tibias were obtained for analysis after 10days during which rats were not submitted to physical training. Physical exercise had a positive effect on bone repair, increasing bone mineral density, bone mineral content, bone formation rate, type I collagen and osteocalcin expression. These parameters were not affected by systemic administration of LPS. Our data indicate that physical exercise has an important osteogenic effect, which is maintained during acute systemic inflammation induced by exposure to a single dose of LPS.