We investigated the peripheral demyelination in transgenic mice with peripheral neuropathy and the effect of adiposederived multipotent mesenchymal stromal cells (ADSCs) transplantation on the ultrastructural features of the sciatic nerve in these mice. The B6.Cg-Tg(PMP22)C3Fbas/J transgenic mice with peripheral neuropathy were injected intramuscularly with ADSCs, which were isolated from the adipose tissue of FVB-Cg-Tg(GFPU) mice transgenic by GFP. For ultrastructural analysis, tissue fixation in animals was performed by transcardiac perfusion-fixation with 4% formaldehyde solution and 2.5% glutaraldehyde solution 16 weeks after transplantation. Electron microscopic examination of fibers of the sciatic nerve in the transgenic mice with peripheral neuropathy showed that many axons in this nerve were subjected to dys- and demyelination; the so-called onion bulb-like structures were observed. In some fibers, hypertrophy of myelin sheaths was found. In general, ultrastructural modifications in the sciatic nerve of the transgenic mice were rather similar to the pathomorphological pattern observed in patients with peripheral neuropathy. At 16 weeks after ADSC transplantation, in the sciatic nerve in mice with peripheral neuropathy thickening of the myelin sheath and increasing of the number of lamellae were observed. Thus, ADSC transplantation in mice with hereditary peripheral neuropathy has a protective effect on the ultrastructural features of the sciatic nerve and inhibits the process of axon demyelination.