[Study on relationship between osteoporosis and mRNA expressions of vascular endothelial growth factor and bone morphogenetic protein 2 in nontraumatic avascular necrosis of femoral head].

OBJECTIVE

To explore the significance and the relationship between osteoporosis and the mRNA expressions of vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP-2) in nontraumatic avascular necrosis of the femoral head (NONFH), so as to provide a theoretical basis for the pathogenesis and the clinical treatment of NONFH.

METHODS

Sixty-nine specimens of femoral head were collected from voluntary donators undergoing total hip arthroplasty, including 37 cases of NONFH (NONFH group) and 32 cases of fresh femoral neck fracture (control group). In NONFH group, there were 26 males and 11 females with an average age of 57.3 years (range, 43-75 years), including 19 cases of steroid-induced avascular necrosis of the femoral head (ANFH), 16 cases of alcoholic ANFH, and 2 cases of idiopathic ANFH; according to Ficat staging system, there were 23 cases at stage III and 14 cases at stage IV. In control group, there were 23 males and 9 females with an average age of 58.6 years (range, 46-79 years). The NO level of serum, the Q value of femur, and the bone mineral density (BMD) of weight-bearing area were measured firstly. The bone tissues were harvested from weightbearing necrosis area and healthy area. The pathological change was observed by HE staining, the percentage of empty bone lacuna and the percentage of trabecular bone area were calculated. The mRNA expressions of VEGF and BMP-2 in femoral head were detected through in situ hybridization technique.

RESULTS

There were significant differences (P < 0.05) in the NO level of serum, the Q value of femur, and the BMD between NONFH group and control group. In NONFH group, the femoral head showed irregular shape, the articular cartilage exfoliated and collapsed. In weight-bearing necrosis area, the bone trabeculae were sparse and non-intact with a great number of empty lacuna; necrotic bone trabeculae were decomposed and absorbed; no obvious bone regeneration and repair were observed. In weight-bearing healthy area, the fat cells in bone marrow showed proliferation and hypertrophy. In control group, the femoral head had normal appearance, intact articular cartilage, and intact bone trabeculae with a regular arrange, and osteocytes were clearly seen. There were significant differences in the percentage of empty bone lacuna and the percentage of trabecular bone area between NONFH group and control group (P < 0.05). The mRNA expressions of VEGF and BMP-2 were positive in 2 groups. The positive area ratio, the absorbance value, and integral absorbance value of VEGF mRNA and BMP-2 mRNA in NONFH group were significantly lower than those in control group (P < 0.05); the grey scales of VEGF mRNA and BMP-2 mRNA in NONFH group were significantly higher than that in control group (P < 0.05).

CONCLUSION

The pathological stage of osteoporosis may play an important role in the mechanism of the NONFH. The decrease of mRNA expressions of VEGF and BMP-2 in femoral head of NONFH is important reason that affect its bone mass, osteoporosis, rehabilitation, and reconstruction. It may be benefit to the reparative process of the necrosis femoral head to increase the mRNA expressions of VEGF and BMP-2 in the femoral head.