Early life stress modulates neonatal somatosensation and the transcriptional profile of immature sensory neurons

Early life stress (ELS) is associated with an increased risk of experiencing chronic pain during adulthood, but surprisingly little is known about the short-term influence of ELS on nociceptive processing in the immature nervous system and the concomitant effects on somatosensation in the neonate. Here we investigate how ELS modulates pain in neonatal mice as well as the transcriptional and electrophysiological signatures of immature dorsal root ganglia (DRG). Shortly after the administration of a neonatal limiting bedding (NLB) paradigm from postnatal days (P)2 to P9, both male and female pups exhibited robust hyperalgesia in response to mechanical, pressure and noxious cold stimuli compared to a control group housed under standard conditions, with no change in their sensitivity to noxious heat. Bulk RNA-seq analysis of L3-L5 DRGs at P9 revealed significant alterations in the transcription of pain- and itch-related genes following ELS, highlighted by a marked downregulation in Sst, Nppb, Chrna6, Trpa1 and Il31ra. Nonetheless, ex vivo whole cell patch-clamp recordings from putative A- and C-fiber sensory neurons in the neonatal DRG found no significant changes in their intrinsic membrane excitability following NLB. Overall, these findings suggest that ELS triggers hyperalgesia in neonates across multiple pain modalities that is accompanied by transcriptional plasticity within developing sensory neurons. A better understanding of the mechanisms governing the interactions between chronic stress and pain during the neonatal period could inform the future development of novel interventional strategies to relieve pain in infants and children who have experienced trauma. Neonatal mouse pups underwent neonatal limited bedding protocol (stress) or control bedding protocol (control) from postnatal day (P)2-9 Lumbar L3-L5 DRG were harvested at P9, and total RNA was extracted for sequencing. Differential gene analysis was performed to identify stress-induced transcriptional changes.早期生活压力（Early Life Stress, ELS）与成年后慢性疼痛的发病风险升高显著相关，但目前学界对ELS在未成熟神经系统中对伤害性感受处理的短期影响，以及其对新生个体躯体感觉的伴随效应仍知之甚少。本研究聚焦于探究ELS如何调控新生小鼠的疼痛反应，以及未成熟背根神经节（Dorsal Root Ganglia, DRG）的转录组与电生理特征。于出生后第2天至第9天（Postnatal Days, P）施加新生期限制垫料（Neonatal Limiting Bedding, NLB）范式后不久，相较于标准饲养环境下的对照组，雌雄幼崽在机械刺激、压迫刺激及伤害性冷刺激下均表现出显著痛觉过敏，但对伤害性热刺激的敏感性未发生改变。对P9时期的腰段L3-L5背根神经节开展批量RNA测序（bulk RNA-seq）分析结果显示，ELS处理后疼痛与瘙痒相关基因的转录水平发生显著改变，其中Sst、Nppb、Chrna6、Trpa1及Il31ra的显著下调尤为突出。尽管如此，对新生小鼠背根神经节中疑似A类和C类感觉神经元的离体全细胞膜片钳记录表明，经NLB处理后，这些神经元的固有膜兴奋性未出现显著变化。综合上述结果，本研究提示ELS可在新生小鼠的多种疼痛模态下诱发痛觉过敏，并伴随发育中感觉神经元的转录可塑性改变。深入阐明新生儿期慢性应激与疼痛相互作用的调控机制，可为未来开发针对创伤婴幼儿的新型疼痛缓解干预策略提供科学依据。本实验中，新生小鼠幼崽于出生后第2天至第9天接受新生期限制垫料方案（应激组）或标准垫料方案（对照组）；于P9时期收集腰段L3-L5背根神经节，提取总RNA进行测序；通过差异基因分析筛选应激诱导的转录组变化。