Study On Regeneration Of Facial Nerve In Hemifacial Composite Tissue Allotransplantation

[Objective]: 1. establish the experimental animal models of the rabbit facial neurotmesis to study the respective effect on nerve regeneration after recovering in three ways : the application of anastomosis are wrapped by Bio-Gide Biomembrane or autogenous vein and direct anastomosis. 2. establish the experimental animal models of hemifacial composite tissue allotransplantation of rabbit and dog to study the facial nerve regeneration after the transplantation.[Method]: 1. A total of 27 livid blue Rabbits selected randomly were evenly divided into simple closure group, autogenous vein group and Bio-Gide Biomembrane group. Experimental animal model of facial buccal neurotmesis was set up in each group. The anastomosis were wrapped with autologous vein and Bio-Gide Biomembrane in autologous vein group and Biogide Biomembrane, while nothing was done in simple closure group. The anastomotic sites were observed with naked eyes after, 4weeks, 8weeks and 12weeks, respectively. Nerve anastomotic samples were observed under HE stained microscopy and transmission electron microscope after 4weeks, 8weeks and 12weeks, respectively. And after 4weeks, 8weeks, and 12weeks, electroneuromyography tests were conducted to analyze the regeneration of rabbit facial nerve. 2. Divided 16 Japanese white rabbits into 8 groups, randomly paired as donor and recipient. establish the experimental animal models of rabbit composite facial allotransplantation, using FK506 and corticosteroids to conduct immunosuppressive treatment. Nerve anastomotic samples were observed under HE stained microscopy and transmission electron microscope after 14 days, 28 days and 40 days respectively. And electroneuromyography tests were conducted to analyze the regeneration of rabbit facial nerve after 28 days, 40 days, respectively.3. The facial nerve of extracranial segment in three hybrid dogs were dissected to study the arrangement and distribution of the nerve. The experimental animal models of dog composite facial allotransplant ation are established based on buccal branches of facial nerve served as transplanted nerve and2 Beagle dogs served as donor and recipient respectively. Nerve electromyography is conducted after 60 days, 100 days, respectively and nerve anastomotic samples are observed under HE stained microscopy and transmission electron microscope after 100 days to see how the dog facial nerve regeneration change after transplantation.[Results]: 1. All of operations succeed and the rabbits survived. The facial nerve of the three groups recovered at different degree. Autogenous vein group and Bio-Gide Biomembrane group are significantly better than the simple suture group either in anastomosis adhesion with surrounding tissue observed with naked eye , or in the indexes of regenerating nerve fibers characters, the disruption of collagen proliferation and changes of ultrastructure , as well as latency and amplitude of nerve electrophysiological testing under microscopy and electron microscope. However, there are no significant differences in the indexes between the autogenous vein group and Bio-Gide Biomembrane group.2. Out of 8 cases of transplant surgery, six succeed. 14 days after transplantation, degenerative changes is the main change in nerve fibers. A small number of nerve fibers appear in the anastomosis, but nerve bundle are in disorder. There are more nerve fibers appear in anastomotic after 28 days and nerve bundle looks more order while the morphology is still not normal. After 40 days, regeneration of nerve fibers become more sophisticated and myelinated nerve increase, but degenerative changes nerve fibers still can be seen. Electroneurography (ENG) cannot be measured clear after 28 days. After 40 days the waveform appear discrete, showing block.conduc- tion.3. Transplant operation makes a success. The latent period of indexes of electroneuromyography is significantly longer than normal. Amplitude reduced remarkably. The latency and amplitude improve significantly after 100 days and at that time the structure of anastomosis become normal.[Conclusion]: 1. Wrapping nerve anastomotic with Bio-Gide Biomembrane and autogenous vein at early period can relieve nerve anastomotic adhesion with surrounding tissue and prevent scar tissue and nerve fibers tumor and in the end promote regeneration of nerve tissue. However, there is on obvious difference between the two.2. The transplantation animal models of Japanese white rabbit, Beagle dog composite facial allotransplantation is feasible, of which Japan rabbit can be used as short-and-medium term model, Beagle dog to be long-term model.3. FK506 oral absorption rate varies differently. The effective plasma concentration may reach 3ng / ml in animal experiment. In this experiment, the starting dose of 0.4mg/kg/d is safe and effective. 4. The regeneration of facial nerve after composite tissue allotransplantation is a very slow process, requiring a series of pathophysiological process. The organizational structure of anastomosis maybe nearly normal 100 days after transplantation, but a longer time is needed before restore functionally.