Effects Of Dexamethasone On Genes Expressions Of Osteoblast Differentiation And Maturation Inside The Femoral Head Of Steroid-induced Osteonecrosis In Rats

Objective By glucocorticoid-induced femoral head necrosis of Wistar rats to study the regulation of osteoblast differentiation and maturation of key genes Runx2 (runt-related transcription factor-2), Osterix, and AJ18 at different times of hormonal necrosis of femoral head and the expression changes in protein synthesis, analysis the role in the femoral head necrosis during the disease progression, provide new theoretical basis and experimental evidence for the femoral head necrosis in the pathogenesis.Methods Early rat model of femoral head necrosis was made with alternate injection of dexamethasone(20mg/kg) bilateral gluteus maximus once a week and twice-weekly training on laboratory animal treadmill after 8 weeks. HE staining to determine the success of osteonecrosis, the model is divided into 8 weeks,10 weeks and12 weeks groups,each group 10 animals.According to period, extract total RNA and total protein from the femoral head for real-time quantitative polymerase chain reaction(PCR), and Western blot were performed to detect the dynamic changes of the Runx2,Osterix,AJ18,OC genes expressions and proteins synthesis inside the femoral head of steroid-induced osteonecrosis in rats. Analyze the role of glucocorticoid on regulation of osteoblast maturate gene.Results Femoral head specimens make pathological examination afer 8 weeks, under the unit area per high power field empty lacunae rate (12.36%), flat field of view of trabecular bone area (56.54%), fat cell diameter (24.52μm) were statistical diference compared with the normal group. At the post-modeling 8th,10th and 12th week, the expression of the Runx2,Osterix and OC genes, proteins synthesis in model group than the control group to reduce obviously, and the volume of mRNA expression were respectively equivalent to 0.9621,0.3259,0.0512 and 0.9661,0.2026,0.0194 and 0.2857,0.2027,0.1583 times of those in control group. Three expression had a downward trend with the longer time. The expression of the AJ18 mRNA, protein synthesis in model group at the post-modeling 8th,10th and 12th week extremely higher than those in control group, which the volume of mRNA expression were 3.5487,3.6303,3.7576 times of those in control group.Conclusion Early steroid-induced femoral head necrosis in rats, by down-regulation Runx2/Osterix mRNA and up-regulation AJ18 mRNA, glucocorticoids may inhibit osteoblast activity, promote bone resorption, leading to osteoporosis and femoral head necrosis.