Bone Abstracts

Introduction: Low-magnitude, high-frequency (LMHF) mechanical stimuli lead to enhance bone formation and decrease resorption. This study aimed to investigate the effect of vibration on the bone loss induced by inflammatory cytokine, lipopolysaccharide (LPS).

Methods and designs: Balb-C mice were administered to LPS (5 mg/kg) with two i.p. injections on days 0 and 4, while sham control group was injected with 400 μl of water for injection without LPS. Animals were sacrificed at days 7 (n=15) and 14 (n=13) after second injection of LPS. Vibration (0.4 g, 45 Hz) were exposed to LPS-injected group next day after second injection for 10 min/day for 4 days (n=10), and then sacrificed for micro-computed tomography (micro-CT) analysis of bone mass. Bone chips extracted from tibia (n=6) was examined for the change of gene expression using real time RT-PCR.

Results: Micro-CT-based evaluation showed that LPS injection led to significant decrease of bone volume (BV) at days 7 after injection, while there was little change in BV at 14 days post-injection. Bone loss was apparent in tibia region rather than other skeletal sites such as femur or calvarium, with significant decrease by 26% in BV, and by 35% in bone mineral density (BMD). Vibratory stimulation after LPS injection led to the increase of both BV and BMD by 18 and 24.5%, respectively, compared to those of non-vibrated, LPS-injected group, which corresponds to ~80% in sham control. Real time RT-PCR using bone chips extracted from tibia revealed the increased expression of type I collagen and osteopontin genes in vibrated group more than non-vibrated, LPS-injected groups.

Conclusions: These findings exhibited that systematic injection of inflammatory cytokine, LPS induced the significant loss of BV and BMD in tibia. Rapid bone loss induced by LPS was efficiently suppressed by LMHF vibration.