Human Amniotic Fluid‐Derived Exosomes Alleviate Neuropathic Pain by Inducing an Anti‐Inflammatory Transition in Microglia

Neuropathic pain is a chronic and debilitating condition characterized by persistent discomfort. Modulation of microglial homeostasis and associated neuroinflammation plays a pivotal role in the pathogenesis of neuropathic pain. Microglia exhibit diverse and dynamic states that contribute to the expression of various cytokines and mediators involved in inflammation. Based on the well-documented anti-inflammatory and neuroprotective properties of human amniotic fluid-derived exosomes (AF-Exos), we tested the hypothesis that AF-Exos could alleviate neuropathic pain by modulating the microglial homeostasis both in vivo and in vitro. Spared nerve injury (SNI) surgery was performed on Kunming mice to induce neuropathic pain. AF-Exos, utilized for both in vivo and in vitro interventions, were isolated from pregnant women in their second or third trimesters. The fluorescein-labeled AF-Exos were detected in both the ipsilateral dorsal horn of the spinal cord and lipopolysaccharide (LPS)-induced BV2 cells. Intrathecal administration of AF-Exos alleviated mechanical allodynia in the ipsilateral hind paw of SNI mice. Following nerve injury, AF-Exos suppressed the expression of IL-1β, IL-6, and nitric oxide in microglia, while upregulating the expression of IL-10. Moreover, AF-Exos promoted a reduction in the CD86⁺/CD206⁺ ratio of BV2 cells and upregulated Arg-1 expression, leading to a transition in the functional state of LPS-induced BV2 cells. Notably, the effects of second-trimester AF-Exos were superior to those of third-trimester AF-Exos. The analgesic effects of human AF-Exos on neuropathic pain may be attributed to their ability to suppress neuroinflammation by promoting the transition of microglia to an anti-inflammatory phenotype.