Placenta-derived adherent cells attenuate hyperalgesia and neuroinflammatory response associated with perineural inflammation in rats

Neuropathic pain is a debilitating condition of the somatosensory system caused by pathology of the nervous system. Current drugs treat symptoms but largely fail to target the underlying mechanisms responsible for the pathological changes seen in the central or peripheral nervous system. We investigated the therapeutic effects of PDA-001, a culture expanded placenta-derived adherent cell, in the rat neuritis model. Pain is induced in the model by applying carrageenan to the sciatic nerve trunk, causing perineural inflammation of the sciatic nerve. PDA-001, at doses ranging from 0.4 × 10⁶ to 4 × 10⁶ cells/animal, or vehicle control was intravenously administrated to assess the biological activity of the cells. A dose-dependent effect of PDA-001 on pain relief was demonstrated. PDA-001 at doses of 1 × 10⁶ and 4 × 10⁶, but not 0.4 × 10⁶, reduced mechanical hyperalgesia within 24 h following treatment and through day 8 after induction of neuritis. The mechanism underlying PDA-001-mediated reduction of neuroinflammatory pain was also explored. Ex vivo tissue analyses demonstrated that PDA-001 suppressed homing, maturation and differentiation of dendritic cells, thus inhibiting T-cell priming and activation in draining lymph nodes. PDA-001 also reduced interferon gamma and IL-17 in draining lymph nodes and in the ispilateral sciatic nerve, and increased the levels of IL-10 in draining lymph nodes and plasma, pointing to T-cell modulation as a possible mechanism mediating the observed anti-hyperalgesic effects. Furthermore, in the ipsilateral sciatic nerve, significantly less leukocyte infiltration was observed in PDA-001-treated animals. The results suggest that PDA-001may provide a novel therapeutic approach in the management of inflammatory neuropathic pain and similar conditions.