Steroid-associated osteonecrosis animal model in rats

Zheng, Li-Zhen; Wang, Jia-Li; Kong, Ling; Huang, Le; Tian, Li; Pang, Qian-Qian; Wang, Xin-Luan; Qin, Ling

During development of ON, necrotic bone repair was accompanied by bone resorption of necrotic bone and reparative bone formation of new bone in this rat SAON model. At the beginning of the repair progress at week 2, bone histomorphometry evaluated in the proximal tibia showed significantly lower Ob. S/BS and higher osteoclast number in the SAON group, suggesting significant bone loss after induction. Bone resorption marker CTX in the SAON group and normal group were however not significantly different, whereas the bone formation marker PINP and OC in the SAON group were both significantly lower than those in the normal group, suggesting systemic bone loss under the influence of LPS and MPS induction. At week 6, because of the continuous steroid treatment and the continuous bone loss, both bone formation markers and bone resorption marker were lower for the SAON group than those in the normal group. Bone histomorphometry revealed that the Ob. S/BS correspondingly showed lower osteoblast number in the SAON group at week 6, which demonstrated the continuous inhibiting effect of the steroid. Severe fat accumulation was found in red marrow region, and more oedema persisted in yellow marrow region at week 6 than those at week 2 in SAON group, suggesting poor blood supply at week 6 when compared with that at week 2, although at week 6, there were only two rats in the SAON group classified as ONÀ, which was explained by on-going repairing progress and the significant bone loss especially in red marrow region of ROIs evaluated at proximal femur, distal femur and proximal tibia.