Histomorphometry in the engraftment model.

A) Axonal regeneration was evaluated at the 1) proximal: midgraft and 2) distal section, 2 mm distal to the graft (4 weeks post transplantation; n = 4 per group). B) Number of myelinated axon into the graft. Left: proximal, right: distal. Myelinated fibers in the bilateral end-to-side (ETS) group were the highest, followed by the unilateral ETS and control groups. Differences among all groups were significant. *p < 0.05, **p < 0.01, ***p < 0.001. C) Electron micrograph of the proximal and distal section. a1–a2) In the control group, proximal and distal sections, respectively, from regenerating nerves of the control group. A small minority of regenerated fibers were confirmed compared with the other groups. Moreover, histological feature was a predominance of thin myelinated fibers in the three groups. b1–b2) In the unilateral end-to-side (ETS) group, proximal and distal sections, respectively, from regenerating nerves of the unilateral ETS group. The number of regenerated fibers was increased more than the control group. The number of regenerated fibers both proximal and distal section exponentially increased compared with the control group. In addition, there were a number of thick myelinated fibers at the distal section compared with the control group. c1–c2) In the bilateral ETS group, proximal and distal sections, respectively, from regenerating nerves of the bilateral ETS group. The number of regenerated fibers at the distal section dramatically increased compared with the unilateral ETS group. Furthermore, at the distal section, abundant myelinated fibers appeared to have a larger myelin thickness than the other groups. Scale bar, 10 μm.