[Effect of different types of jumps on the expressions of IL-6, OPG and RANKL in rat tibia].

OBJECTIVE

To investigate the effect of different types of jumps on the expressions of interleukin 6 (IL-6), osteoprotegerin(OPG), ligand of receptor activator of NF-κB(RANKL) genes related to bone metabolism in rat tibia, and explore the molecular mechanism underlying bone destruction associated with over-loading jumping.

METHODS

Twenty-four male SD rats were randomly assigned to control group (C), jump group (J) and loading jump group (JL), 8 rats in each group. J group participated in incremental load training. The rats in JL group carried loads that were 5% of their body mass. Same training plan was used in J and JL groups, while control group was not treated. The experiment was completed after 6 weeks. The serum samples were collected and assayed for the contents of alkaline phosphatase (ALP) and tartrate resistant acid phosphatase (TRACP). One-side tibia was used for paraffin section and HE staining, and the other side was used for real time quantitative PCR(qRT-PCR) to detect the expressions of IL-6, OPG and RANKL mRNA.

RESULTS

Compared with control group and J group, the collagen fibers in periost was more disordered in JL group. We further observed a more serious damage of the cortical bone and increased cavities in JL group. The serum ALP levels in JL group were significantly higher than those in control and J groups (P<0.05). The serum TRACP levels in JL and J groups were significantly higher compared to control group (P<0.05). Furthermore, there was a significantly higher expression level of IL-6 in both jump groups (P<0.01), while the JL group had a higher IL-6 expression compared with J group (P<0.01). There was a higher expression of OPG mRNA in JL and J groups (P<0.05). The highest expression level of OPG was observed in J group. The expression level of RANKL was significantly higher in JL group compared with control and J groups (P<0.01).

CONCLUSION

After loading jump for 6 weeks, the expressions of IL-6 and RANKL were markedly elevated in rat tibia, suggesting that IL-6 and RANKL might be involved in the process of bone destruction due to increased bone turnover.