| Abstract |
An in vivo experimental rat model was established to test the effects of the neurotrophic factors brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF) and neurotrophin-3 (NT3), on the regeneration of the peripheral sciatic and peroneal nerves. Nerve grafts contained Schwann cells genetically modified using lentiviral vectors to express individual factors. As controls, autografts and acellular nerve sheaths were also tested as grafting material. With about 1cm nerve defects, acellular grafts performed just as well as autografts. Quantitative analysis showed that axonal densities within grafts were increased, with NT3 expressing Schwann cells presumably inducing sprouting of regenerated axons. Further analysis of grafts assessed ultra-structural morphology, myelination and organization of unmyelinated axons in Remak bundles. Again NT3 appeared as an influential factor, this time simultaneously increasing the number of unmyelinated axons and of Remak bundles. On the other hand, myelination was enhanced by two other factors: BDNF, which increased the number of myelinated fibres; and CNTF, which increased the area of myelin around individual fibres. The latter factor also affected the recovery of muscle weights from denervation induced atrophy, on which NGF had equally a significant impact. Lastly, both NGF and GDNF produced remarkable displays of tropism, inducing the formation of axonal entrapments and neuromas. |
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These results highlighted the need for a new generation of delivery vectors, providing the benefits of delivery of neurotrophic factor to the site of injury but allowing for control of their expression. Finally, as regain of function is the ultimate goal of any repairment strategy, the locomotor function of injured animals was analysed using the newly developed Ratwalk system, a software application allowing for objective assessment of several locomotio parameters. Overall, this thesis sustains the proposition that there are effective alternatives to autografts, and presents a comprehensive analysis of several regenerative parameters influenced different types of neurotrophic factor. |
