The Effects of Small Extracellular Vesicle Biogenesis Inhibitors and Plasma-Derived Small Extracellular Vesicles on Nociception in Mice.

INTRODUCTION: Nociception arises from complex intercellular communication among diverse cell types. Small extracellular vesicles (sEVs) are critical mediators of this communication, yet their role in nociceptive signaling remains poorly understood. Here, we investigated the impact of sEV modulation on nociception in both naïve mice and a mouse model of postoperative pain induced by plantar incision. METHODS: Female and male C57BL/6 mice were injected with the sEV biogenesis inhibitors Manumycin-A or GW4869, or administered isolated plasma-derived sEVs, under both naïve conditions and following plantar incision. To assess mechanical and thermal sensitivity, von Frey and Hargreaves were used, respectively. RESULTS: Administration of manumycin-A and GW4869 significantly reduced circulating sEV levels to a comparable extent. While manumycin-A had no effect on mechanical or thermal sensitivity in either uninjured or injured animals, GW4869 unexpectedly increased nociceptive sensitivity across both conditions. Preliminary data suggest an off-target, immune-mediated mechanism. In addition, administration of plasma-derived sEVs did not alter nociceptive responses in either model. CONCLUSION: These findings suggest that circulating plasma-derived sEVs and systemic pharmacological inhibition of EV biogenesis did not play a major role in nociceptive assays tested here under naive and injury-induced conditions. Importantly, our results also uncover a previously unrecognized side-effect of GW4869, cautioning against its use in vivo studies of sEV biology. Further studies are necessary to decipher the tissue- and cell-specific roles of sEVs in pain processing.