Stem cell
therapy is a potential treatment for
spinal cord injury (SCI), and a variety of different stem cell types have been grafted into humans suffering from
spinal cord trauma or into animal models of
spinal injury. Although several studies have reported functional motor improvement after
transplantation of stem cells into injured spinal cord, the benefit of these cells for treating SCI-induced
neuropathic pain is not clear. In this study, we investigated the
therapeutic effect of transplanting human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) or amniotic epithelial stem cells (hAESCs) on SCI-induced
mechanical allodynia (MA) and
thermal hyperalgesia (TH) in T13 spinal cord hemisected rats. Two weeks after SCI, hUCB-MSCs or hAESCs were transplanted around the spinal cord lesion site, and behavioral tests were performed to evaluate changes in SCI-induced MA and TH. Immunohistochemical and Western blot analyses were also performed to evaluate possible
therapeutic effects on SCI-induced
inflammation and the nociceptive-related phosphorylation of the
NMDA NR1 receptor subunit. While
transplantation of hUCB-MSCs showed a tendency to reduce MA,
transplantation of hAESCs significantly reduced MA. Neither hUCB-MSC nor hAESC
transplantation had any effect on SCI-induced TH.
Transplantation of hAESCs also significantly reduced the SCI-induced increase in
NMDA receptor NR1 subunit phosphorylation (pNR1) expression in the spinal cord. Both hUCB-MSCs and hAESCs reduced the SCI-induced increase in spinal cord expression of the microglial marker, F4/80, but not the increased expression of GFAP or iNOS. Taken together, these findings demonstrate that the
transplantation of hAESCs into the injured spinal cord can suppress
mechanical allodynia, and this effect seems to be closely associated with the modulation of spinal cord microglia activity and NR1 phosphorylation.