The Effect of Neuronal Growth Factor on the Early Recovery After Experimental Sciatic Nerve Defect in Rabbits

Abstract

Objective/Hypothesis: The facilitation of early functional recovery after peripheral nerve damage is a key component in the treatment of severe nerve traumas. The regeneration of peripheral nerves is determined by multiple factors. The nerve growth factor (NGF) plays an important role in the recovery process by facilitating the Schwann cell proliferation and helping to prepare the reception of the regenerating axon. The purpose of the study was to evaluate the rate of early nerve regeneration in the presence or absence of NGF treatment, using either silicon tubes or autolog veins as a bridge for the neuron defect in a rabbit model of nerve injury. Materials and Methods: White Canadian rabbits were used in the study. Animals were divided into 4 groups (n = 10 in each group). Under general anesthesia, 1 cm long part of the sciatic nerve was removed and the ends were connected with either silicon tube or autolog vein. In case of 10-10 rabbits, NGF was added into the connecting tubes or veins. For another 10-10 rabbits (Control animals), only plasma was added. Electrophysiological examination was performed 2, 4, 6, and 8 weeks following surgery. Histological examination was done on the postoperative second, fourth, and sixth week on 2-2 animals and on the postoperative eighth week on 4-4 animals. Results: The regeneration analyzes demonstrated that the NGF-treated nerves had already become more mature and organized by the postoperative fourth week. The rest of the fibers were still demyelinated; however, there were more myelinated fibers in the NGF-treated group. On the sixth week, the regenerated parts formed into small fascicules, showing a diffuse pattern of myelinated and demyelinated fibers. On the eighth week, the fascicules were strengthened with the signs of longitudinal vascularization. We found significantly higher number of myelinated fibers in the NGF containing tubes, compared with the Controls. Conclusion: Here, we demonstrated that the NGF-treated regenerating nerves show more maturity and neuronal organization on the fourth and sixth week, compared with the Control groups. This effect could facilitate the early functional recovery after peripheral nerve injuries. While NGF has a significant effect on the early regeneration of the rabbit sciatic nerve, based on our results, the endogen NGF has no significant effect on the late nerve regeneration process.