Objective: To study the effect of local application of different concentrations of nerve growth factor (NGF) on fracture healing, and to further search for the appropriate concentration gradient of NGF to promote fracture healing.
Methods: Seventy-five adult male Sprague Dawley rats, weighing (220.0 +/- 2.5) g, were made the right tibia fracture model at 1 cm distal from the tibial tubercle and randomly divided into 5 groups (groups A, B, C, D, and E, n=15). Fractures were treated with 0.3 mL normal saline containing different concentration of NGF (0.00648 x 10(-2), 0.032 40 x 10(-1), 0.16200 x 10(-2), and 0.81000 x 10(-2) microg/g) in groups A, B, C, and D, respectively, and the same amount of normal saline in group E. After 2, 4, and 6 weeks, the specimens were harvested from 5 rats of each group to perform the biochemical test and histological observation. Before the rats were sacrificed, the arteriovenous blood was taken from the eye-ball to test the alkaline phosphatase (ALP) activity.
Results: After 2, 4, and 6 weeks, the gross observation showed that the size and hardness of bone tissue and callus tissue growth gradually increased in groups A, B, C, and D, and group D was higher than groups A, B, C, and E. The X-ray films showed that the calcified area gradually increased in groups A, B, C, and D, and group D was higher than groups A, B, C, and E. The histological observation showed that the trabecular quality and maturity in group D were better than those in groups A, B, C, and E. Group D was significantly higher than groups A, B, C, and E (P < 0.05) in the gray values of callus tissue and the calcium content of callus tissue at 4 and 6 weeks, in the wet weight of callus tissue at 2 and 4 weeks, and in the ALP content of serum at 2 weeks. The trabecula surface index of osteoblast, the trabecular volume, and the trabecular width decreased as time in the order of groups A, B, C, and D, which were higher than those of group E; group D was the highest, showing significant differences when compared with the other groups (P < 0.05).
Conclusion: The local application of NGF can promote fracture healing in rats. The high concentration gradient of NGF (0.81000 x 10(-2) microg/g) has an obvious promotion role on fracture healing.