127: Deciphering the impact of neutrophils in the onset of pediatric pain.

Topic: Basic Science
Subtopic: Pain category (ICD-11), Acute postsurgical pain, , , , , , , , , , Neuroimmunology, Electrophysiology, Assessment and Measurement of Pain/Nociception

Background and Aims: The recent advancements in understanding the neuroimmune landscape after injury have highlighted the role of various immune cells in the onset and resolution of pain. Notably, the interaction between macrophages and sensory neurons in post-surgical pain development has been recently reported [1]. Building on this, the aim of our current study is to investigate the role of neutrophils, the first immune cells to respond to injury, in a model of pediatric post-surgical pain. This study will also assess whether their involvement persists in later stages of life to modulate neonatal nociceptive priming.

Methods: For behavioral studies, a right hind paw muscle incision was performed at P7 and/or P35, followed by intraperitoneal administration of neutrophil-targeting antibodies (anti-Ly6G and MAR 18.5) [1, 2]. Neutrophil depletion was validated by hematoxylin and eosin (H&E) staining.
To determine how neutrophils modulated sensory neuron responsiveness, we utilized an ex vivo hind paw muscle–tibial nerve–DRG–spinal cord calcium imaging preparation in neutrophil-depleted mice and corresponding controls [1, 3]. Finally, single-cell RNA sequencing (scRNA-seq) was performed on cells isolated from the dorsal root ganglia (DRG) under various conditions to determine potential mechanisms for acute and chronic post-surgical pain development.

Results: Behavioral analyses of antibody-depleted mice demonstrated reduced paw guarding and mechanical hypersensitivity following muscle incision at P7 and after repeated incision at P35, compared with neutrophil-depleted mice or those subjected to a single injury during adolescence. Consistently, ex vivo calcium imaging revealed altered mechanical thresholds and changes in fluorescent intensity in sensory neurons from neutrophil-depleted mice relative to their respective controls. scRNA-seq from DRGs identified Schwann cell-derived genes and pathways associated with neutrophil degranulation. Findings that were supported by H&E staining.

Conclusions: This study supports the notion that neutrophils contribute to pain development following both single and repeated surgical procedures in neonates. Our findings further suggest that this process is potentially guided by Schwann cell–mediated signaling to the immune system. Together, these results provide important insights into the role of neutrophils in inflammation and pain and identify a potential therapeutic target for alleviating pain in the often-overlooked pediatric population.

References: 1. Dourson, A.J., et al., Macrophage memories of early-life injury drive neonatal nociceptive priming. Cell Rep, 2024. 43(5): p. 114129.
2. Boivin, G., et al., Durable and controlled depletion of neutrophils in mice. Nat Commun, 2020. 11(1): p. 2762.
3. Fadaka, A.O., et al., The intersection of endocrine signaling and neuroimmune communication regulates muscle inflammation-induced nociception in neonatal mice. Brain Behav Immun, 2025. 125: p. 198-211.

Presenting Author: Namrata Raut
Submitting Author: Namrata Raut

Senior Author: Michael P. Jankowski

IASP 2026 Global Year theme of Neuropathic Pain: No