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[Changes of vessel in steroid-induced osteonecrosis of femoral head: experimental study of rabbits].

OBJECTIVE
To investigate the changes of vessel function, vessel injury, blood viscosity and vessel regeneration in steroid-induced osteonecrosis of femoral head.


METHODS
Forty Chinese white rabbits were randomly divided into 2 equal groups to be injected with: horse serum intravenously twice with an interval of 3 weeks and than prednisone intraperitoneally once a day for 5 days (Group A), or injected with prednisone once a day for 5 days (Group B). Whole blood samples were collected by intracordal puncture before intravenous injection in group A and B, 24 hr after injection of horse serum in group A, and 3, 7, and 21 days after prednisone administration. Radioimmunological methods were used to detect the plasma endothelin (ET) and thrombomodulin (TM), and ELISA was used to detect the plasma intercellular adhesion molecule-1 (ICAM-1. Some rabbits were killed before intravenous administration, 24 hrs after injection of horse serum in group A, and 3, 7, 21, 35, and 49 days after the first treatment with prednisone respectively and their bilateral femoral heads were taken out to undergo HE staining and microscopy and SP-VEGF immunohistochemistry.


RESULTS
The levels of plasma TM, ET, and ICAM-1 gradually increased in comparison with those before treatment in both group, however, not significantly (all P > 0.05). The levels of plasma TM 1 week and 3 weeks after the initial prednisone administration inn Group A were significantly higher than those in Group B (both P < 0.05). 3 weeks after the initial prednisone administration the levels of plasma ICAM-1 and TM began to decrease and were lower than those 1 week after, however, not significantly (both P > 0.05). Pathological changes could be seen 1 and 3 weeks after in both groups and then recovered by the 7th week after the treatment. The level of VEGF expression in the osteocytes, osteoblasts, and cells of bone matrix and endothelial cells increased first 1 week after and then decreased after the prednisone administration in Group A, and decreased after the prednisone administration in Group B, however, without significant differences between these 2 groups.


CONCLUSION
After prednisone treatment, a pre-necrosis status occurs in femoral head with a potential to restore which can be affected by many factors. Long-term observation on this status is necessary.