BDNF Gene Transfre Promotes Regeneration after Rat Facial Nerve Crush Injury

Although facial nerve injury is seldom a complication of dentoalveolar surgery, transient Bell's palsy may follow an inadvertent injection of local anesthetic into the parotid gland and its superficial location make it liable to be injured during dental treatment. A variety of methods are used in the treatment of facial palsy. However, there is no simple and effective treatment for this problem up to now.

Objectives: Damage to the facial nerve produces weak muscles of facial expression. Facial nerve crush model was designed and nerve recovery was evaluated using BDNF gene transfer.

Materials and Methods: A crushed injury was made with hemostat to create axonotmesis on the right facial nerve main trunk in rats. Adenoviral BDNF (BDNF-Ad) was injected into the experimental group and saline was injected for the control group. Regeneration was evaluated with functional test (vibrissae and ocular movement), electrophysiologic (threshold voltage, peak voltage, conduction velocity) and histomorphometric study.

The t-test was used to compare the mean score of the electrophysiology test and axon density results in the same day. The Mann-Whitney U test was used to compare the mean score of functional test in the same day. For analysis of experiments involving time, one-way ANOVA was used to determine the mean score of the electrophysiology test results and the axon density measurements. The Kruskal-Wallis test was used to compare the mean score of the functional test results on the same day between the control and experimental groups. A value of p < 0 .05 was considered significant.

Results: Functional test score, threshold and conduction velocity improved with time in both groups.  However, axon density increased significantly only in the experimental group. Functional tests at 10 and 20 days showed no difference. Vibrissae movement, threshold, conduction velocity and axon density at 30 days revealed that the degree of regeneration in the experimental group was significantly superior. The degree of nerve regeneration in the BDNF-Ad group was significantly higher during the 30 days of analysis, and functional recovery after facial nerve crush was obtained 30 days.

 Conclusion: Despite the lack of long-term effectiveness, the present study demonstrates that the administration of BDNF using an adenoviral vector accelerates nerve regeneration for a period of 30 days following crush injury.

References

Zhang, J.Y., Luo, X.G., Xian, C.J., Liu, Z.H. and Zhou, X.F. (2000). Endogenous BDNF is required for myelination and regeneration of injured sciatic nerve in rodents. Eur J Neurosci 12, 4171-4180

Hadlock, T.A., Heaton, J., Cheney, M. and Mackinnon, S.E. (2005). Functional recovery after facial and sciatic nerve crush injury in the rat. Arch Facial Plast Surg 7, 17-20.