The Experimental Study On Using MGTR Technique And Schwann Cells Self-Planting Engineering To Repair The Facial Nerve

The facial nerve is one of the most important motor nerves in facial area, which controls the movement of muscle of face. Because the facial nerves are situated in superficial place, they are easy to be hurt in traumatism. In addition the facial nerves can be injured during the operation of parotid tumours, which leads to facial paralysis.The traditional method to treat facial nerve defect is to take microsurgical repair techniques that fit the two ends of the nerve together. But because of many factors the effects of traditional method are usually not perfect, facial muscle joint movement can be found and the recovery speed is slow. It is known that the Schwann cells and many cytokines (neurotropic factors and neurotropic trophic factors and so on) which are produced by Schwann cells have a important effect on the nerve regeneration, so we change the traditional method and take self Schwann cells to improve the nerve regeneration in order to establish a newmethod that can be used in clinical work to treat the nerve defect.In this study, seven experiments on rabbits were performed to confirm the effect of some new methods of repairing facial nerve.The experiment 1 was using e-PTFE tube to bridge the 10mm facial nerve defect of rabbits. Then the result shows that this mGTR technique can finish the facial nerve repairing well.The experiment 2 was comparing the effect of two methods that were mGTR and self-nerve transplantation. The result shows that their effects are almost equal.The experiment 3 was to observe and compare the effects of using mGTR or silicon tube or Vine connection to repair the defect of facial nerve. The mGTR, silicon tube connection and Vine connection methods were performed on three groups of rabbits. Then physical and Histological examination was carried out to get the results of these three repair methods. All of them can induce regeneration of facial nerve. The mGTR is more effective and faster in repairing the nerve defect. Three months after operation, the distance of NCV between two side facial nerve is 2.10 ± 1.2 in mGTR group, 6.80 ± 1.4 in silicon tube group and 6.16 ± 1.6 in Vine group. The conclusion is mGTR is more effective than silicon tube connection and vine connectionsmethod in repair facial nerve.The experiment 4 was to observe the NGF's effect with mGTR technique in repair facial nerve. The 10mm facial nerve defect was created, and bridged using e-PTFE tube. Then NGF was injected into the nerve regeneration chamber to repair facial nerve defect. The result shows the NGF is effective in facial nerve repairing.The experiment 5 was to investigate the effect of using e-PTFE tube containing nervous homogenates to repair the rabbit facial nerve defect. Thirty-six adult New-Zealand rabbits weighing 250-300g were randomly selected. Right sides were selected as e-PTFE containing nervous homogenates group: Firstly 8mm defects of facial never were made, then the defects were bridged with e-PTFE tube, finally the nervous homogenates were implanted into the e-PTFE tube. Left sides were selected as e-PTFE group: 8mm defects of facial nerve were made, the proximal and distal stumps were simply bridged with e-PTFE tube. Regeneration of the nerve was assessed by gross observation, nerve electrophysiological test and optical microscope observation. The electrophysiological examination showed that in the e-PTFE group there was no muscular contraction while in the homogenates group the electric stimulus could get through the nerve defect at 4th week. The nerve conduction velocity of the homogenates group recovered betterthan that ot the e-Flrb group at 8th, lzth week. Uptical microscope observation showed that at 4th week, the proximal and distal nerve stumps widely denervated in the e-PTFE group, but in the homogenates group, all the proximal nerve stumps regenerated through the chamber and reached to the distal end. AT 8th week, in the e-PTFE group, the regenerating nerve fiber got through the nerve defect, the nerve fibers were sparse and arranged in disorder throughout the tube. In the homogenates group, the tubes were filled with regenerating nerve fibers which arranged in order. At 12th week, in the e-PTFE group, the nerve fibers lined up in orders, but there existed the phenomena that the nerve fibers were confused. In the homogenates group, regenerating nerve fibers were mature. Conclusions: The effect of e-PTFE tube with nervous homogenates planting to repair the facial never is better than that of e-PTFE group alone.The main content of the study is to bridge the 10mm facial nerve defect with e-PTFE tube and take self Schwann cells planting in the nerve regeneration chamber.The experiment 6 was to find the best method to get pure Schwann cells from nerve pieces. Enzymatic digest method and poly-L-lysine differential adhesion method were used to get pure Schwann cells in short time and the best appropriate digest time and the purification method were established, which proved that it is possible to get enough pure Schwann cells in short time bythe method of enzymatic digest.The experiment 7 was to bridge the 10mm defect of facial nerve using e-PTFE tube and pure self-Schwann cells were planted into the e-PTFE chamber. In the control groups the nerve defect was bridged using e-PTFE and silicon tube without the Schwann cells plantation. At 6w, 12w and 16w after operation, the electric physiological experiment and histological examination were taken to compare the effect of nerve regeneration of experimental group and control group to evaluate the three methods.In these observations the nerve regeneration effect of the experimental group was best of the three groups at any time, which had been proved by electric physiological experiment and histological examination. The NCV of the experimental group is fastest in the three groups at 6w, 12w and 16w. The regenerative nerve of experimental group is more mature than the control groups by histopathologically examination. The nerve fibers organized into coherent bundles containing abundant mature elements were seen throughout the e-PTFE tubes and the Schwann cells were seen within the graft wall itself. The regenerative nerves of experimental group were similar with normal nerve. In the two control groups, the e-PTFE control group was better than silicon tube group. The following conclusion can be drawn:1. It is possible to obtain sufficient active Schwann cells by enzymatic digest method and it takes 95 percent of all the cells. The fibroblasts of the nerve membrane can be eliminated effectively after poly-L-lysine differential adhesion method is used.2. In the experiment that e-PTFE had been used to bridge the defect of facial nerve. It is found that the effect of the self Schwann cells planting group is better than that of control group (only use e-PTFE to bridge the nerve but without the self Schwann cells planting in regeneration chamber). A small quantity of self Schwann cells planted in e-PTFE nerve chamber can improve the nerve regeneration speed and the quality. No obvious difference exists between the regenerative nerve and normal facial nerve in facial movement and electrophysiology examination results. The self-Schwann cells can increase in the nerve regeneration chamber and produce neurotropic factors. By the method of Immunohistochemistry (SI00) we found the existence of Schwann cells in the nerve regeneration chamber and the finestra of the e-PTFE. The e-PTFE tube provided a favorable local microenvironment for the nerve regeneration because of its microporous structure. Schwann cells in the tube can get nutrition and get rid of the waste freely through the minuteness hole of the e-PTFE, which maintain a favorable local microenvironment.