Prevention of bone loss by injection of insulin-like growth factor-1 after sciatic neurectomy in rats

Objective: Injection of insulin-like growth factor-1 (IGF-1) can prevent bone loss in sciatic nerve transaction rats. We try to investigate the action mechanism of IGF-1 on bone formation. Methods: A total of 40 adult male Spragne-Dawley rats were divided into two groups (experimental group and control group) with 20 animals in each. Sciatic neurectomy was performed to model disuse osteoporosis in all rats. IGF-1 was administered in experimental group with the dose of 100 mu g/kg per day for 3 days. Meanwhile, the rats in control group were treated with saline. Bone mineral density was measured by dual-energy X-ray absorptiometry 4 and 6 weeks after neurectomy respectively. Expression of Osterix and Runx2 was determined by reverse transcription-polymerase chain reaction (RT-PCR) assay. Results: There was a significant increase in the bone mineral density of experimental group compared with control group. There was a significant decrease in the level of receptor activator of nuclear factor-kappa B-ligand but an increase in the level of osteoprotegerin 4 and 6 weeks after neurectomy in the experimental group compared with control one. The expression of Osterix and Runx2 was up-regulated in the bone marrow of experimental group compared with control group. Conclusion: IGF-1 can increase bone formation by stimulation of osteoblast number and activity, and reduce bone resorption by restriction of differentiation of osteoclast, suggesting that IGF-1 may improve the therapeutic efficacy for disuse osteoporosis.