Recent studies have shown that mesenchymal stem cells (MSCs) and their conditioned medium (CM) have potential therapeutic effects in animal models of neuropathic pain (NP). However, the mechanisms underlying these effects are not fully understood. Because of the leading involvement of purinergic receptors in the pathogenesis of NP, this study aimed to investigate the effect of MSCs-CM on the expression levels of P2X4 and P2X7 receptors in a rat model of NP induced by chronic constriction injury (CCI) of the sciatic nerve. CM was prepared from the rats' bone marrow-derived MSCs culture. After that, NP rats were treated by intraperitoneal injection of CM, or Dulbecco's modified Eagle's medium (DMEM) 1 day before and 7 and 11 days after CCI surgery. The NP status was assessed in the treated animals using behavioral tests, including mechanical allodynia and thermal hyperalgesia, on days - 1, 3, 6, 9, 12, and 15 of the study. At the end of the study (Day 15), the animals were sacrificed, and the relative gene expression of P2X4 and P2X7 receptors were measured in the spinal cord using quantitative real-time PCR. The results demonstrated that in the CM-treated NP rats, mechanical allodynia and thermal hyperalgesia were significantly reduced compared with the DMEM-treated group. In addition, the expression levels of P2X4 and P2X7 receptors were noticeably prevented in the CM-treated group than the control group. These findings indicate that the antinociceptive effects of CM in the NP rats are partly mediated through preventing the upregulation of P2X4 and P2X7 receptors in the spinal cord.
Keywords: Allodynia; Conditioned medium; Hyperalgesia; Mesenchymal stem cells; Neuropathic pain; P2X4 receptor; P2X7 receptor.