Use of human Adipose-derived Stem Cells in a mouse model of neuropathic pain

Neuropathic pain is a complex disease and, so far, there are no pharmacological treatments acting in a definitive way. Recent studies suggest that this disease is associated with neuronal-tissue damage. Adipose-derived Stem Cells (ASCs) have shown the capacity of limiting neuronal damage through their anti-apoptotic effect, together with the reported capacity of releasing neurotrophic molecules. These cells are adult, undifferentiated, multipotent cells capable of self-renewal, with low immunogenicity and immunosuppressive properties; moreover, they are easily available in large amount. Our study aimed to detect the effect of human ASCs in a mouse sciatic nerve chronic constriction injury (CCI) model. hASC were isolated from subcutaneous adipose tissue of 5 healthy women (mean age 37±12); all the populations were characterized phenotipically and their clonogenic and differentiative potential were evaluated in order to verify their stemness. Particularly these cells shown a clonogenic capacity of about 3% at early passages and, when cultured in osteoinductive medium for 14 days, they presented an increase in phosphatase activity and in calcified extracellular matrix deposition of 252% and 193%, respectively. 10^6 hASC were injected into the rodents caudal vein 7 days after CCI, and, at 1,3,7,14,21 and 28 days post injection, we assessed their effect on mechanical allodynia (Dynamic Plantar Aesthesiomether) and thermal hyperalgesia (Plantar test) and correlated it with the alterations in pro- and anti-inflammatory cytokines (ELISA assay). hASCs were able to completely reverse hyperalgesia and reduce allodynia starting 24 hours after injection. The effect began to fade 21 days after administration, but it could be restored by a new cell injection (1x106). In parallel we observed a recovery of cytokines balance both for pro- and anti-inflammatory ones. In particular the levels of IL-1β and IL-6, that are significantly enhanced in CCI mice, are restored when mice are treated with cells. As far as anti-inflammatory cytokines are concerned, hASCs treatment induces a significant increase in IL-10 level respect to both sham-operated and CCI animals. In this study, we demonstrated that hASCs treatment is able to reduce neuropathic pain symptoms and to re-establish cytokine balance in a CCI mouse model; this phenomenon might be due to the recruitment of the cells in the lesion area and to their interaction with the resident ones inducing a modulation of pain and inflammation.