Abstract: Objective　 To study the dynamic changes in gene expression and protein synthesis of runt-related transcription factor-2(Runx2), Osterix and MMP-13 in the femoral head of steroid-induced osteonecrosis (SANFN) in rats.　Methods　Forty adult Wistar rats were randomly divided into two groups: a model group (n = 30) and a control group (n=10). Rats in the model group were treated with dexamethasone 20 mg/kg intramuscularly injection once a week. After the injection, the animals were trained on the treadmill. The model group was divided into 3 groups according to the training time (10 cases each): A group for 8 weeks; B group for 10 weeks; C group for 12 weeks. The expression of Runx2, Osterix and MMP-13 and protein synthesis in femoral heads were detected by PCR and Western blot.    Results    The maximal diameter of adipocyte and the ratio of empty bone lacuna in model group were higher than those in control group. With the increasing of training time, the maximal diameter of adipocyte and the percentage of empty bone lacuna gradually increased (P<0.00). The area of trabecular bone in the model group was lower than that in the control group, and the area of trabecular bone decreased gradually with the increasing of training time (P< 0.00). The expression of Runx2, Osterix protein and gene in the model group was lower than that in the control group. With the extension of time, the expression level decreased gradually (P<0.05). The expression level of MMP-13 protein and gene in the model group was higher than that in control group. With the extension of time, the expression level increased gradually (P<0.05).　Conclusions　The mRNA and protein expression level of Runx2, Osterix in steroid-induced osteonecrosis of femoral head is lower than that in normal femoral head tissue and the mRNA and protein expression level of MMP-13 is higher than that in normal femoral head tissue.

Key words:  , MMP-13, 　Steroid-induced necrosis of femoral head, 　Osterix, 　Runx2