Development of an early-stage femoral head necrosis rabbit model using methylprednisolone and Complete Freund's Adjuvant

Abstract

Introduction: Pathological animal models provide the foundation for developing new methods for disease treatment. This research aims to establish a rabbit model of femoral head necrosis. Methods: Osteonecrosis of the femoral head (ONFH) was induced in rabbits by using methylprednisolone (MPS) combined with Complete Freund's Adjuvant (CFA). New Zealand White rabbits were divided into two groups. ONFH group (n=10) was given an intramuscular injection of 0.5 mg/kg CFA and 40 mg/kg methylprednisolone. Normal group (n=6) received normal saline at the same location and same volume as those in ONFH group. The efficiency of the ONFH rabbit model was assessed at week 7 after the last injection. Body weight was detected, and the histological structure of head femoral and bone were assessed by H&E staining. The empty lacunae were counted. Cartilage degeneration was evaluated using image analysis software. Blood vessel density was assessed after ink artery infusion. The cell cycle of bone marrow-derived mononuclear cells was analyzed by flow cytometry. Results: The results showed that there was no difference in body weight changes of rabbits between the two groups. However, the bone morphology and cartilage surface of the femoral head showed abnormalities in the ONFH group. The percentage of empty osteocyte lacunae was significantly higher in ONFH group than normal group. Chondrocyte degeneration and fibrocartilage expression were observed in the ONFH group. Compared to the normal group, the ONFH group had less ink-stained blood vessels. However, the fraction of bone marrow-derived mononuclear cells in S phase and G2/M phase of the cell cycle was significantly increased in the ONFH group. Conclusion: Thus, CFA combined with MPS for 7 weeks can be used to establish an early-stage femoral head necrosis model in rabbits.