Regenerative role of mast cells and mesenchymal stem cells in histopathology of the sciatic nerve and tibialis cranialis muscle, following denervation in rats.

Objectives: Atrophy of the muscles following denervation can lead to the death of myofibers. This study evaluated the sciatic nerve and tibialis cranialis muscle (TCM) regeneration using scaffold and cells.

Materials and methods: Ninety adult male Wistar rats were divided into six main groups (n=15) and three subgroups (2, 4, and 8 weeks). Groups: control; without surgery, Tr; sciatic nerve transected in silicone tube, S; collagen gel put inside the silicone tube, MC; placed 3×10⁴ mast cells mixed with scaffold, MSC; placed 3×10⁴ mesenchymal stem cells mixed with scaffold, and MC+MSC; 3×10⁴ of each of the mast cell and mesenchymal stem cells along with scaffold. Animals were euthanized and sampled for muscle and nerve histological and nerve immunohistochemical evaluations.

Results: Diameter of muscle fibers, ratio of the muscle fiber's nuclei to the fibrocyte nuclei (mn/fn), ratio of the muscle fibers nuclei number to the muscle fiber's number (mn/mf), and ratio of the blood vessels number to the number of muscle fibers (v/mf) in all treatment groups, especially the MC + MSC group, increased compared to the Tr group but the number of mast cells, the percentage of sarcoplasmolysis, and necrosis fibers decreased. Histomorphometric results of the nerve in its various parts and immunohistochemistry results also showed improved nerve conduction, especially in the MC + MSC group.

Conclusion: In this study, nerve improvement happened mainly for two reasons: cells and time. So, the most obvious improvement occurred in the group with mast and mesenchymal cells in the 8^th week.