ABSTRACT
BACKGROUND: Steroid-induced avascular necrosis of the femoral head (SANFH) may be associated with apoptosis of osteocytes, but its regulatory mechanism remains unclear. Cytochrome C and Caspase-9 are key factors in the mitochondrial apoptosis signaling pathway, and their roles in SANFH still need further investigation. OBJECTIVE: To investigate the roles of cytochrome C and Caspase-9 in the SANFH. METHODS: Twenty New Zealand white rabbits were randomly divided into experimental and control groups (n=10 per group). Rabbits in the experimental group were injected with 7.5 mg/kg methylprednisolone, twice weekly, and those controls were subjected to the injection of same amount of normal saline. The treatment period was 8 weeks in both group.The rabbits were then sacrificed by air embolism to remove the bilateral femoral head specimens for histological and transmission electron microscope observations. The apoptotic cells were detected by TUNEL method and the expression levels of cytochrome C and Caspase 9 were detected by immunohistochemistry. RESULTS AND CONCLUSION: Eight weeks after intervention, compared with the control group, the experiment group had loose femoral head, thinned trabecular bone, increased adipocytes in the medullary cavity, and increased percentage of empty lacunae (P ＜ 0.05); the apoptotic bodies were formed, and the apoptosis rate was increased (P ＜ 0.05); and the positive expression rates of cytochrome C and Caspase-9 were significantly increased (P ＜ 0.01). Correlation analysis results showed that the apoptosis rate was positively correlated with the empty lacunae rate and the positive expression rates of cytochrome C and Caspase-9 (P ＜ 0.01). These findings indicate that the abnormal release of cytochrome C and high expression of Caspase-9 are related to the apoptosis of osteocytes in SANFH.