Objective To investigate the effect of glucocorticoid on the expression levels of osteoprotegerin (OPG)/receptor activator of nuclear factor kappa B ligand (RANKL)-matrix metalloproteinases (MMP)/tissue inhibitor of matrix metalloproteinase (TIMP) system in bone tissues of femoral head of rats, and to discuss its interrelated action mechanism in glucocorticoid-induced avascular necrosis of femoral head (ANFH). Methods Forty adult Sprague Dawley rats, weighing 250-300 g, half males and half females, were randomly divided into 4 groups: high dose glucocorticoid group (HD, n=10), medium dose glucocorticoid group (MD, n=10), low dose glucocorticoid group (LD, n=10), and control group (n=10). The rats in HD group, MD group, and LD group were intramuscularly injected with 25.0, 12.5, and 7.0 mg/kg of prednisolone respectively, and the rats in the control group were injected with physiological saline. After 4 weeks intervention, the osteonecrosis of left femoral heads was observed by HE staining, total RNA was extracted from the right femoral head bone tissue and the mRNA expression levels of OPG, RANKL, MMP-2, MMP-9, TIMP-1, and TIMP-2 were detected by RT-PCR. Results After injection of prednisolone, 4 rats of HD group and 1 rat of MD group died of systemic failure caused by the decreased food and weight culminating in cachexia. HE staining showed that the integrity of bone trabecula and osteon was destroyed at different levels, discontinuous bone chips formed, and osteocytes were replaced by granulation tissue in some lacunae in HD, MD, and LD groups; the integrated osteon was observed, the lamellar structure formed concentric circles around the blood vessel and osteocytes were seen in the lacunae in the control group. The necrosis rates of femoral head were 83.3% (5/6), 66.7% (6/9), 30.0% (3/10), and 0 (0/10) in HD, MD, LD, and control groups. The results of RT-PCR showed: the mRNA expression levels of the OPG, TIMP-1, TIMP-2 in HD, MD, and LD groups were lower than those in the control group, showing significant differences (P lt; 0.05) and there was negative correlation with the hormone dosage. The difference in OPG expression was significant between the hormone groups (P lt; 0.05); the differences in the TIMP-1 and TIMP-2 expressions were not significant between the LD group and MD group (P gt; 0.05), but there were significant differences when compared with HD group (P lt; 0.05). The RANKL, MMP-2, and MMP-9 mRNA expression levels in HD, MD, and LD groups were higher than those in the control group and there was a positive correlation with the hormone dosage, showing significant differences when compared MD and HD groups with control group (P lt; 0.05); there was no significant difference in RANKL expression between HD group and MD group (P gt; 0.05), but there was significant difference when compared HD and MD groups with LD group (P gt; 0.05); no significant difference was observed in the MMP-2 and MMP-9 expression between MD group and LD group (P gt; 0.05), but the differences were significant when compared with HD group (P lt; 0.05). Conclusion Glucocorticoid-induced ANFH may be related to the expression levels of OPG/RANKL-MMP/TIMP mRNA regulated by glucocorticoid.
Objective To investigate the effect of TIMP-2 gene that was transfected by adenovirus on extracellular matrix of abdominal aortic through assessing the changes of morphology and histopathology of the rat models with abdominal aortic aneurysm. Methods The rat models with abdominal aortic aneurysm were constructed by intraluminally perfusing porcine pancreatic elastase. Twenty-four SD rats with aneurysm were then randomly divided into 3 groups: AdTIMP-2 group (perfused locally with solution of TIMP-2 gene transfected by adenovirus vector to abdominal aorta), AdCMV group (transfected by non-viral vector), and PBS group. After 14 days, the concentrations of elastin and collagen that were collected from the samples of aortic wall were measured by image analysis system and the fixed aortic tissues were examined by light microscopy and some other specific staining methods. Results None of abdominal aortic aneurysm developed in TIMP-2 gene transfected group, with significantly higher rates of developed aneurysm in the other groups (P＜0.01). The diameters of arteries on day 14 in the AdTIMP-2 group were (2.33±0.06) mm, which were significantly smaller than those in the AdCMV group 〔（3.52±0.11） mm〕 and PBS group 〔（3.43±0.09） mm〕. The elastic fibers and collagenous fibers were preserved with more integrity in AdTIMP-2 group and inflammation cells that were observed in adventitia of artery were also less than those of the other groups. Conclusion TIMP-2 gene transfected by adenovirus vector could restore the degradation of extracellular matrix that was aroused by elastase and could block the formation of abdominal aortic aneurysm, which may provide a new strategy for the treatment of abdominal aortic aneurysm.