Human Adipose Stem Cells Improve Mechanical Allodynia and Enhance Functional Recovery in a Rat Model of Neuropathic Pain.

Stem cells are a promising source of tissue engineering due to their differentiation potential. Today, direct transplantation of stem cells for cell therapy is commonly performed. However, in cases of nerve injury, direct transplantation of cells could lead to secondary nerve damage. Male Sprague-Dawley rats were randomized into four groups: the phosphate-buffered saline epineural transplantation (PBS-ENT) group, the PBS intraneural transplantation (PBS-INT) group, the human adipose-derived stem cells epineural transplantation (hASCs-ENT) group, and human adipose-derived stem cells intraneural transplantation (hASCs-INT) group. Transplantation was conducted 1 week later after inflicting a crush injury with subsequent observation for 5 weeks. To evaluate pain, each group was examined with regard to paw withdrawal latency and evoked potentials. The sciatic functional index (SFI) was calculated to estimate functional recovery. The sciatic nerve was also examined histologically. The hASCs-ENT group showed a more rapid paw withdrawal threshold and SFI recovery than the other groups (p<0.05). The hASCs-ENT group also showed shorter initial latencies in both somatosensory evoked potential (SSEP) and motor evoked potential (MEP) than the PBS-INT group (p<0.05). In addition, the N1 latency of the MEP and the N1 and P1 latencies of the SSEP were significantly shorter than those of the PBS-INT group (p<0.05). Histological examination revealed that the transplanted groups showed better neural recovery and remyelination than the groups injected with PBS. These results show that the transplantation of hASCs into the injured sciatic nerve improved mechanical allodynia and functional recovery as determined by the paw withdrawal test, SFI analysis, and electrophysiological studies. ENT is superior to INT in terms of invasiveness and better outcomes.