Posters

Neuropathic pain is devastating as affecting 9% of people worldwide, and many discoveries from pre-clinical models fail to be translated into effective treatments. Therefore, the investigations using ‘human nerve tissues’ are gaining more attentions. Through bulk RNAseq and histology, we found the signature of glucocorticoid-induced macrophages (MGC: CD163+STAB1+MARCO+) in Morton’s neuroma, i.e., a human focal nerve injury at foot, compared to non-neuropathic nerves. The mRNA level of MARCO was positively correlated with patients’ paroxysmal pain. Our unpublished scRNAseq result also indicates the normalized count of MARCO in ‘macrophage cluster’ is 3-time higher in Morton’s neuroma compared to control human nerves at donor level (N= 6 each). The findings from human nerves were then translated to a humanised in vitro microfluidic coculture platform to detect the spontaneous neuronal firings as the surrogate indicator of paroxysmal pain. Using GCaMP8 calcium imaging, our bespoke coculture system and ‘Fast Fourier Transform’-based analysis pipeline were validated using a published inflammatory soup to prove capable of digitalizing the level of spontaneous neuronal firing. At single-somata level, we observed the significant enhancement of sensitizing effect (p= 0.036) when MGC were cocultured with human induced pluripotent stem cell derived sensory neurons for 4 days compared to M0 neutral macrophage control. The difference in sensitizing effect didn’t reach significance at per microfluidic device level but with an obvious enhancement trend. In summary, aligned with our RNAseq implications, the pilot coculture result suggests MGC can sensitise human sensory neurons; however, additional interrogations will be required before drawing a solid conclusion.

Psilocybin, a serotonergic psychedelic and selective 5-hydroxytryptamine 2A (5 HT2A) receptor agonist, has been shown to induce structural and functional neuroplasticity in the prefrontal cortex through serotonergic signalling and brain-derived neurotrophic factor (BDNF) upregulation. While emerging evidence suggests analgesic potential, mechanistic insights into psilocybin’s effects in chronic pain remain limited. Here, we investigated its actions in the spared nerve injury (SNI) model of neuropathic pain in male and female C57BL/6J mice, with emphasis on interaction with gabapentin. A single intraperitoneal dose of psilocybin (0.3–1 mg/kg) produced robust, lasting reductions in mechanical hypersensitivity up to 30 days in males and shorter, yet significant, effects in females. These outcomes coincided with dose-dependent head-twitch responses and were blocked by the selective 5 HT2A antagonist volinanserin, implicating 5 HT2A activation in psilocybin’s antinociception. Repeated low-dose administration (0.3 mg/kg weekly for three weeks) amplified and prolonged analgesic effects without impairing locomotion. To assess combination potential, gabapentin (50 mg/kg) was administered during psilocybin’s peak analgesic window or weeks later, after its effects had subsided. Co-administration enhanced and extended gabapentin efficacy, while prior psilocybin treatment markedly potentiated gabapentin’s analgesic response 30–55 days after nerve injury in otherwise poorly responsive mice. These findings identify psilocybin as a promising adjunct therapy for neuropathic pain capable of both direct analgesia and sustained enhancement of standard treatment efficacy, suggesting a novel therapeutic approach in which a single psilocybin exposure may restore or augment responsiveness to existing pain medications.