| Objectives: The influencing factors of functional recovery for regenerated nerve is very complicated after faical nerve injuried. The aims of nerve renovation is not only the regeneration of nerve trunk, the much important is reestablishment of nerval physiologic function. We established the facial nerve transsection modle, to observe morphology changes , electrophysiological reaction and neurotrophic factors'express in the damage site after transsection of the facial nerve, to evaluate the effect of local microenvironment in the elongation of axons and branches and functional recovery.Methods: 36 Newzeland adult rabbits were selected in random, then divided into mutilation group, micro- inosculation group and nerve growth factor(NGF) treatment group. Mutilation group:separated and revealed buccal branches of facial nerve, intersected it, then put the two ends of the nerve into the ?2.4mm silica canal, establishing the silica regeneration chamber. Micro- inosculation group: separated , revealed and intersected buccal branches of facial nerve in the same way, sutured the two ends by the 10/0 partition suture. NGF treatment group: have the same operation process. Injected 0.1ml stroke-physiological saline solution into the anastomotic stoma(mutilation point) once every 3 days for mutilation group and micro- inosculation group, Injected 0.1ml stroke-physiological saline solution which contains 2μgNGF into the anastomotic stoma once every 3 days for NGF treatment group. At the time of 2 week, 4 week, 6 week after operation, electrophysiology tests were be done in 4 rabbits each group, observe the latency period and conduction velocity, collected the section of facial nerve in the transsection site to take the immunohistochemical test, to observe the express of nerve growth factor in the damage site, at the time of 4 and 6 week the section be taken to have the silver staining and HE staining, at the same time it was observed under the transmission electron microscope, to know the change of ultramicrostructure in the axons and branches. Results:1. macroscopic observation: 2 weeks after operation: connective tissue could be seen around the transsection site(silica regeneration chamber) of facial nerve. 4 weeks after operation: the distal ends of injury facial nerve of mutilation group and micro- inosculation group were thinner than normal nerve, the NGF treatment group's were thicker than the others; 6 weeks after operation: the distal ends of injury facial nerve of mutilation group group is thinner yet, micro- inosculation group's became oncoides and thicker, the NGF treatment group's were ncoides and thicker than normal nerve, and could tolerance the tensile force not to break.2. Electrophysiology test: Mutilation group, micro- inosculation group and NGF treatment group were not educed action potential 2 weeks after operation. 4 weeks after operation, the action potential could be educes in every group, and the latency period was longer than normal, but there is not obviously different between each of them,nerve conduction velocity(NCV) was slowly than normal too, and there is not obviously different between each of them.3. immunohistochemical test: NGF express extensive in all time and in all group, it distribute in the stroma chiefly. 4 weeks and 6 weeks after operation, it expressed significantly in the micro- inosculation group and NGF treatment group, and it is intensive in the lamellar sheath.4. Silver staining and HE staining: The quantity of SC (Schwann cell) and regeneration fibers is few in Mutilation group and micro- inosculation group, the proportion of collagen tissue is large 4 weeks after operation. There were more regeneration fibers in NGF treatment group relatively, and the arrangement of the regeneration fibers is in disorder in all groups. 6 week after operation, the proportion of regeneration fibers and the quantity of SC increased in all group, but the arrangement of the regeneration fibers was still in disorder. NGF treatment group had the well-arranged regeneration fibers relatively.5. Images of transmission electron microscope:It shows that the regeneration axons are rare in Mutilation group 4 weeks after operation, collagen fibers are the main composition of the regeneration tissue. Micro- inosculation group have more regeneration axons, but the thickness of myelin is unequal, the structure of myelin layers is loose, the average diameter≈5μm, the proportion of myelinated fibres and nonmyelinated fibers is about 1:2. There are more regeneration axons in NGF treatment group, the diameter of myelinated fibres is thicker(≈6μm), and the distribution is more uniformity and compactive, but there are more nonmyelinated fibers in them. Six weeks after operation, regeneration axons'myelin is more thicker, and the diameter increased, but the structure is not compative enough. There are few myelinated fibres distribute diffusely in the collagen tissue in Mutilation group, the structure of myelin is loose, the proportion of myelinated fibres and nonmyelinated fibers is 1:2. Micro- inosculation group have more regeneration axons, and structure of myelin is more regular and compative. There are much more regeneration axons in the NGF treatment group, and the disposition of them are compative, the myelin thickness is uniformity, the structure of myelin layers is tight, the myelinated fibres have thicker diameter, the proportion of myelinated fibres and nonmyelinated fibers is about 1:3.Conclusion:1. The mechanical guide and neurotrophy factors in the local microenvironment could promote the growth of the axons and branches of the facial nerve after it is injuried.2. The proportion of myelinated fibres after injury of facial nerve may be concerned with the level of functional recovery of nerve.3. The precise inosculation and increasing the density of neurotrophic factors could shorten the reparative process and promote the level of recovery. |
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