Abstract <p>Peripheral nerve injury (PNI) is a relevant biomedical problem, especially in wartime, given the high frequency of such injuries. Bioengineering means for rehabilitative treatment of PNI are considered the most promising, among which the effect of stem cell transplantation into the subarachnoid space on the process of plastic reconstruction of the nervous system in the context of PNI is the least studied. In this study, we investigated the effect of delayed transplantation of two types of human stromal multipotent stem cells into the cisterna magna on the restoration of the functional index of the sciatic nerve (sciatic functional index, SFI) after its transection and immediate epineural suturing in adult rats. The obtained data indicate that delayed intrathecal xenotransplantation of dermal multipotent stromal stem cells or multipotent mesenchymal stem cells, derived from the wall of umbilical artery, performed 2 weeks postinjury, leads to a significant increase in SFI after 2.5 months of observation. In the case of umbilical artery-derived stem cells’ injection, this result is significantly higher than the result of sciatic nerve suturing without the procedure of cell transplantation.</p>