BACKGROUND
The most common surgical technique that used for repairing segmental nerve defects is using autolog nerve grafts. Although there are alternative tecniques, the results of these techniques are not successful. The morbidity of the donor site is a disadvantage of the nerve graft. In this study it was aimed to produce prefabricated nerve graft as effective as autolog nerve graft without donor site morbidity.
METHODS
Thirty adult Sprague-Dawley rats were used. One centimeter long jugular vein of the rats were excised and epineurial sheaths were excised in the related area. Rats were separeted into three groups each of them included ten rats. In the first group (epineural window group), vein graft excised from jugular vein was sutured to make a bridge between epineurial gaps of tibial and peroneal nerve. In the second group (partial incision group), ¼ of the nerve diameter was incised after excision of epineurial sheath, and vein graft excised from jugular vein was sutured to make a bridge between epineurial gaps of tibial and peroneal nerve. In the third group (gene therapy group), vein graft excised from jugular vein was sutured between epineurial gaps of tibial and peroneal nerve, and plasmid including VEGF gene were injected to muscle next to the nerve. At 2, 4, 6, and 8. weeks, functional assessment of nerve regenaration was realized by using “walking track analysis”. Morphological assessment was performed at the end of the eight weeks follow up period.
RESULTS:
Gene Therapy Results
The amount of VEGF was determined by test of quantitative ELISA from muscle samples preoperatively (0. day), 15 days postoperatively and 45 days postoperatively in gene therapy group (Group III) .
While increase of gene expression was seen at second week postoperatively in all samples, it was seen only in three samples until sixth week postoperatively. According to these results, gene therapy was succeeded in all samples, but its effect continued no more than six weeks.
Functional Assessment
According to peroneal function index, nerve injury signs were occurred initially in partial incision groups, but it improved gradually and got normal values at six week postoperatively. Peroneal function index values were changed with operation in neither epineural window group nor gene therapy groups. There were no statistical significant difference between the groups at eighth week (p>0.05).
Similarly, when tibial function index values were evaluated, we observed that nerve injury signs were occurred initially in partial incision group, but it improved gradually and got normal values at six week postoperatively. Tibial function index values were changed with operation in neither epineural window group nor gene therapy group. There were no statistical significant differences between groups at eighth week (p>0.05).
Histologic Results
The difference of the numbers of myelinated fibers between group II (partial incision group) and group III (gene therapy group) was not significant (p> 0.05); however, the differences of the other groups (group I-group II, group I-group III) were significant (p< 0.05).
The difference of the mean fiber diameters between group II (partial incision group) and group III (gene therapy group) was not significant (p> 0.05); however, the differences of the other groups (group I-group II, group I-group III) were significant (p< 0.05).
According to microscopic evaluation of semithin sections, there were myelinated fibers passed through vein graft in all groups. Although prefabricated grafts were included a few thinly myelinated axons in group I (epineural window group); there were so many myelinated fibers in group II (partial incision group) and group III (gene therapy group). The myelinated fibers of the group II and group III were better organized and thicker than group I.
The electron microscopic results were similar with semithin sections.
CONCLUSION
We prefabricated nerve graft by using autolog vein as a conduit material between two intact nerve and by gene therapy which increases the VEGF level in the medium.