Adipose-derived Mesenchymal Stem Cells Improve Spontaneous Pain in a Rat Model of Neuropathic Pain

Background: Several studies have investigated the efficacy of transplanting adipose-derived mesenchymal stem cells (ADMSC) in the treatment of neuropathic pain in animals. However, these studies evaluated the effects of transplantation by measuring stimulus-induced pain but not spontaneous pain. Evaluation of spontaneous pain is essential for assessing neuropathic pain in clinical practice, using such measures as the visual analogue scale (VAS). Therefore, spontaneous pain should be evaluated even at the animal experiments stage to verify the efficacy of ADMSC transplantation for treating neuropathic pain. Here, we verify whether ADMSC transplantation improves spontaneous pain in a rat model of neuropathic pain induced by chronic constriction injury of the sciatic nerve. Methods: ADMSC were isolated from rat adipose tissue and propagated in culture. One week after CCI model rats were generated, ADMSC were transplanted into the epineurium of the area of nerve damage. The effects of transplantation were evaluated by automatically measuring the number of spontaneous pain-related behaviors and quantifying the degree of mechanical allodynia using the von-Frey filament test. A total of 20 F344 rats were used in these experiments. Results: ADMSC transplantation significantly reduced the number of spontaneous pain-related behaviors and significantly alleviated mechanical allodynia from 21 and 7 days after transplantation, respectively. No animals died during the experiments, and all animals gained weight over the course of the study. Conclusion: ADMSC transplantation improved not only stimulus-induced pain but also spontaneous pain. ADMSC transplantation may be an effective treatment for neuropathic pain in clinical practice.