Transplanted MDSPCs foster repair of critical-size sciatic nerve defects.

<p>(<b>A</b>) A 4- to 5 mm segment of the sciatic nerve was removed from the hind limb of each mouse, (<b>B</b>) resulting in a 6.5 to 7 mm defect. (<b>C</b>) Following transplantation of MDSPCs into the defect, complete regeneration from proximal to distal end was observed <i>(n</i> = 28). Blood vessel networks (arrowheads) were also present around all regenerated nerves. (<b>D</b>) Many <i>nLacZ</i>-positive cells (blue) were observed between weeks 5 and 9 following injury. “<i>p</i>” corresponds to the proximal stump and “<i>d</i>” to the distal stump. (<b>E</b>) The regenerated nerve exhibited both NF (green) and CNPase (red) immunoreactivity. (<b>F</b>) CNPase (red) staining of the regenerated sciatic nerve revealed nodes of Ranvier-like structures (white circles). (<b>G</b>) Cross-sections of regenerated nerve showed <i>nLacZ</i>-positive cells (blue) and exhibited NF-positive axons (green, inset) encompassed by FluoroMyelin-positive cells (red, inset). (<b>H, I, J</b>) Colocalization of β-gal (red) with (<b>H, I</b>) GFAP (green) or (<b>J</b>) CNPase (green), and DAPI (blue) suggests possible differentiation of the MDSPCs into Schwann cells (double-positive cells denoted by arrows). (<b>K-M</b>) Electron microscopy of semi-thin cross-sections of (<b>K</b>) non-operated (uninjured) control, and (<b>L, M</b>) MDSPC-regenerated peripheral nerve 10 weeks after implantation, show a high number of myelin-producing Schwann cells. Arrows indicate Schwann cells surrounding the myelinated axon. “Sc” corresponds to Schwann cells, “M” to myelin sheath, and “Ax” to axons. (<b>N</b>) Graphical quantification of the g-ratio (axonal area: myelinated fiber area) represents the median values of both uninjured and MDSPC-regenerated nerves (<i>P</i><0.001, Mann-Whitney Rank Sum Test). Sciatic nerve regeneration studies represent three independent experiments. The morphometric parameters represent results from 5 mice (2 controls and 3 treated) and analysis of 1000 fibers. Scale bars represent 100 µm (<b>D, E, and G</b>) or 10 µm (<b>F, H-M</b>).