A Comparison Between The Repair Functions Of Autologous Platelet Rich Plasma(PRP) And Nerve Growth Factor(NGF) To Facial Nerve Injuries

Objective: An animal experiment model is built on severely damaged rabbit facial nerves through the method of applying a silica gel tube on the two ends of the severed facial nerve thus creating a regeneration chamber. Then by injecting PRP and NGF respectively into the tube and waiting for the surrounding tissues to absorb the chemicals, and an observation was made throughout 8 weeks on the nerve regeneration and functional recovery. PRP and NGF both played a role in the mechanism of facial nerve injury repair. The role of PRP and NGF in inducing nerve axons and myelin regeneration effects was compared, in order to seek a simple, economic, safe, and effective way to repair facial nerve injury for clinical purposes. Methods: 30 healthy, big ear white rabbits were randomly divided into 3 groups, each group containing 10 rabbits. After transecting all of the rabbits’ facial nerve buccal branch the first group was injected with PRP, the second group was injected with the same amount of NGF, and the last group was injected with the same amount of normal saline as a control group. All the rabbits were kept in separate cages. 8 weeks after the operation, observation was made to the rabbits’ whiskers and facial muscle movement. The original wound was cut and re-opened and an electrophysiological detection was conducted. The 30 rabbits were sacrificed and the new-born neural tissue were extracted from the regenerative chamber, each stained with HE and silver nitrate colouring and observed under an inverted microscope with magnification of 40 x and 100 x. Nikon T1-RCP medical image software and image analyzer was used to calculate the amount of nerve regeneration, and assess the recovery of nerve regeneration. Results: 1.General observation of the facial nerve: the restoration of the movement in the upper lip moustache orbicularis muscle in the control group was the weakest, followed by the NGF experimental group. The PRP experimental group’s upper lip orbicularis muscle movement restoration was the best. 2.The detection of nerve electrophysiology: the PRP group orbicularis muscle action potential latencies was significantly lower than the experimental NGF group and the control group(P<0.01). The PRP’s neuromuscular compound action potential amplitude(M wave) was higher than the NGF group and was significantly higher than the control group(P<0.01). 3.Observation made under inverted microscope: the experimental groups PRP and NGF mainly consisted of myelinated nerve fibres, myelin sheath thickness of the PRP group was slightly better than the NGF group. The molecular size and shape arrangements of the nuclei in the PRP group tended to be more consistent than the NGF group. And the diameter of the regenerated axons in the PRP group, compared with the NGF group, was closer to the diameter of normal axons. Regenerated nerve tissues in the control group consisted of the myelinated nerve fibres and non-myelinated nerve fibres. The myelin was thinner, demyelination and myelin disintegration phenomenon was common, which mean the blank area caused by the liquidation and dissolution of the axonal myelin lipids was more common. Both the PRP group and the NGF group were significantly better than that of the control group in terms of the regenerated nerve myelinated axon area, myelin sheath thickness and axon counts. The PRP group was the best of the three groups. The results of the multiple comparison among the three groups were all statistically significant(P<0.01). Conclusion:1.PRP can induce and promote neuron axon and myelin regeneration; 2.PRP, compared with NGF, is more effective in the repair and regeneration of facial nerve injury, and,with PRP, the regeneration of facial the myelinated nerve tissue is relatively better.