Histological and morphometric evaluations (VBD group vs. VB group). Transverse sections of the regenerated nerve 5 mm distal to the distal suture were observed under light microscopy (A–H) and transmission electron microscopy (TEM; I–L) at 12 (A, B, E, F, I, and J) and 24 (C, D, G, H, K, and L) weeks. Red blood cells filled the lumen of the inserted vessels (arrow). The number of myelinated axons (M) and the neural area (N) were larger in the VBD group compared with the VB group. Regenerated axons with a larger diameter (O) and thicker myelin sheaths (P) were observed in the VBD group compared with the VB group. Scale bars: 100 μm (A–D), 10 μm (E–H), and 2 μm (I–L). ∗p <0.05. VBD group, the group with implantation of the sural vessels, bone marrow-derived mesenchymal stem cells (BM-MSCs), and a decellularized allogenic nerve matrix (DANM); VB group, the group with the sural vessels and the BM-MSCs.