Objective: To investigate the effect of NGF on fracture healing, and to study the role of BMP-2 induced osteoblast.
Methods: Sixty cleaned male Kunming mice (aging 6-8 weeks and weighing 23-25 g) were made fracture models in the middle of femoral shaft and randomly divided into four groups (groups A, B, C and D, n=15). Fracture was treated with NGF/normal saline, BMP-2, BMP-2/NGF/normal saline, and normal saline in groups A, B, C and D, respectively. After 14, 21 and 28 days, the specimens were selected from 5 mice each group to do the biochemical and histological analysis. Before the mice were killed, the arteriovenous blood was taken from their eye-ball to test the ALP activity.
Results: After 14 days, 21 days and 28 days, the gross observation showed that the size and hardness of bone tissue, and callus tissue growth increased in groups A, B and C order and were higher than those in group D; the X-ray films showed that the calcified area increased in groups A, B and C order and were higher than those in group D; the histological observation showed that the trabecular maturity increased in groups A, B and C order and were higher than those in group D. The osteoblast area, the gray degree value of the radiographs in callus tissue, the ALP contents of serum and callus tissue, calcium content of callus tissue and net weight of callus were higher in groups A, B and C than in group D. There were significant differences (P < 0.05) in osteoblast area and gray degree values of the radiographs at 14, 21 and 28 days; in ALP contents of serum at 14 days; in ALP contents of callus tissue at 14 days and 21 days; in calcium content of callus tissue at 21 days and 28 days among 4 groups. There were significant differences in net weight of callus between groups B, C and groups A, D at 14 days (P < 0.05). At 21 days and 28 days, the trabecular surface index of osteoblast, the average trabecular volume and the mean trabecular width decreased as time went on, having an increase order of groups A, B, C and was higher in groups A, B, C than in group D, showing significant differences among 4 groups (P < 0.05).
Conclusion: NGF promotes the healing of fractures. NGF possesses synergistic effect on ectopic bone formation induced by BMP-2.