Dynamic expression of Runx2, Osterix and AJ18 in the femoral head of steroid-induced osteonecrosis in rats.

OBJECTIVE

To study dynamic changes in gene expression and protein synthesis of runt-related transcription factor-2 (Runx2), Osterix and AJ18 in the femoral head of steroid-induced osteonecrosis in rats.

METHODS

Forty mature Wistar rats, 250-270 g (mean, 260 g) in weight, were randomly divided into model (30 rats) and control groups (10 rats). An early rat model of femoral head necrosis (FHN) was created by weekly injections of dexamethasone (20 mg/kg) into alternate sides of the gluteus maximus and twice-weekly training on a laboratory animal treadmill for 8 weeks. Hematoxylin and eosin (HE) staining was used to determine whether osteonecrosis had been successfully induced, and the model was then divided into equal 8, 10 and 12 week groups. At the end of the appropriate time period, total RNA and total protein were extracted from the femoral heads, and then real-time quantitative polymerase chain reaction and Western blot were performed to detect dynamic changes in the expression of Runx2, Osterix and AJ18 and protein synthesis in femoral heads with steroid-induced osteonecrosis in rats.

RESULTS

At the post-modeling eighth, tenth and twelfth week, expression of Runx2 mRNA, Osterix mRNA and related protein synthesis were significantly down-regulated compared to that of the control group, which showed a downward trend with time; while expression of AJ18 mRNA and protein synthesis in the model group was much higher than in the control group, which showed an upward trend with time.

CONCLUSION

Glucocorticoids may induce femoral head osteonecrosis by down-regulating Runx2/Osterix mRNA and up-regulating AJ18 mRNA.