Comparison of the effects of Polycaprolactone (PCL) nanofibers containing methylcobalamin and tacrolimus on peripheral nerve regeneration

Peripheral nerve injuries are common and can cause loss of sensory and motor functions in the affected patient group. Even after successful surgeries, satisfactory results in motor and sensory functions may not be achieved. Incomplete healing of peripheral nerve injuries often leads to many adverse consequences such as numbness, chronic pain, and decreased sensory and/or motor function in the affected limbs, and for these reasons, peripheral nerve injuries constitute a worldwide clinical problem. Current research has evolved in this direction in order to find a pharmacological agent that can be successfully administered. One of these researches is nanotechnology and nanomaterials produced with this method. In our study, we aimed to compare the effects of nanofiber nerve wraps containing methylcobalamin and tacrolimus, which contribute to peripheral nerve regeneration through different mechanisms. Six groups were constituted with 8 rats in each group and the studies were performed. The left sciatic nerve of rats was explored by dorsal approach under anesthesia in all groups. In all groups except Group 1, a full-thickness straight transection was performed with micro scissors 1 cm proximal to the left sciatic trifurcation under the microscope. After the transection, epineural repair of the sciatic nerve was performed with 9/0 nylon sutures in the same session and coaptation was achieved. For Group 2, only epineural repair was performed. For group 3, PCL nerve wrap produced by electro-spinning method was wrapped around the epineural repair site. PCL nanofiber nerve wraps containing Methylcobalamin for Group 4, Tacrolimus for Group 5 and both Methylcobalamin and Tacrolimus for Group 6 were wrapped around the epineural repair site. The rats were followed up for 8 weeks. Before the rats were sacrificed, walking track test and electrophysiologic evaluations were performed for functional assessment. After sacrification under anesthesia, the left sciatic nerve was sampled for histopathological examination. Bilateral gastrocnemius muscles were separated from their origo-insertions and weights were measured on a sensitive laboratory scale and gastrocnemius muscle weight index was calculated. At the end of the 8th week, the best SFI value was found in Group 4 among the groups that underwent surgical procedure with a full-thickness transection of the sciatic nerve. The highest and best gastrocnemius muscle weight index values were found in Groups 4 and 5, which were closest to the sham group among the groups that underwent surgical procedure by making a full-thickness transection in the sciatic nerve. There was no statistically significant difference between Groups 4 and 5 (p=0.600). The mean latency periods from Group 1 to Group 6 were 1.42±0.13, 2.15±0.47, 1.83±0.22, 1.63±0.22, 1.74±0.25, 1.82±0.16 ms, respectively. The mean amplitude values from Group 1 to Group 6 were 11.91±2.30, 3.59±0.76, 4.86±3.71, 9.27±2.41, 7.75±2.51, 5.62±3.37 mV, respectively. In histopathological assessment, the mean fibrosis value was found to be the lowest in Group 5. When inflammation was evaluated, less inflammation was observed in Groups 5 and 6 compared to the other groups. In Groups 4 and 5, there were no rats with more than 50% axonal degeneration. Group 3 had the highest mean vascularization value and Groups 4, 5 and 6 had similar vascularization values. When the groups were compared in terms of axonal density per mm2 , the highest mean axon number was seen in Group 5. Fascicular disorganisation was found to be the least in Group 4 of the groups that underwent surgery with full-thickness transection of the sciatic nerve. In group 4, there were no rats with more than 50% fascicular disorganisation. In conclusion, nanofiber nerve wraps containing either methylcobalamin or tacrolimus contributed favorably to nerve regeneration functionally and histopathologically when used separately. When the two agents were compared functionally and histopathologically, no significant superiority was observed in terms of nerve regeneration. It was observed that the combined use of methylcobalamin and tacrolimus did not have a synergistic effect on nerve regeneration and did not result in a statistically significant difference, although there were positive contributions to nerve regeneration.