Department of Neurobiology & Anatomy, Marion Murray Spinal Cord Research Center, College of Medicine, Drexel University, Philadelphia, Pennsylvania.
J Pain. 2024 May;25(5):104433. doi: 10.1016/j.jpain.2023.11.016. Epub 2023 Nov 24.
Spinal cord injury (SCI) affects ∼500,000 people worldwide annually, with the majority developing chronic neuropathic pain. Following SCI, approximately 60% of these individuals are diagnosed with comorbid mood disorders, while only ∼21% of the general population will experience a mood disorder in their lifetime. We hypothesize that nociceptive and depressive-like dysregulation occurs after SCI and is associated with aberrant macrophage infiltration in segmental pain centers. We completed moderate unilateral C5 spinal cord contusion on LysM-eGFP reporter mice to visualize infiltrating macrophages. At 6-weeks post-SCI, mice exhibit nociceptive and depressive-like dysfunction compared to naïve and sham groups. There were no differences between the sexes, indicating that sex is not a contributing factor driving nociceptive or depressive-like behaviors after SCI. Utilizing hierarchical cluster analysis, we classified mice based on endpoint nociceptive and depressive-like behavior scores. Approximately 59.3% of the SCI mice clustered based on increased paw withdrawal threshold to mechanical stimuli and immobility time in the forced swim test. SCI mice displayed increased myeloid cell presence in the lesion epicenter, ipsilateral C7-8 dorsal horn, and C7-8 DRGs as evidenced by eGFP, CD68, and Iba1 immunostaining when compared to naïve and sham mice. This was further confirmed by SCI-induced alterations in the expression of genes indicative of myeloid cell activation states and their associated secretome in the dorsal horn and dorsal root ganglia. In conclusion, moderate unilateral cervical SCI caused the development of pain-related and depressive-like behaviors in a subset of mice and these behavioral changes are consistent with immune system activation in the segmental pain pathway. PERSPECTIVE: These experiments characterized pain-related and depressive-like behaviors and correlated these changes with the immune response post-SCI. While humanizing the rodent is impossible, the results from this study inform clinical literature to closely examine sex differences reported in humans to better understand the underlying shared etiologies of pain and depressive-like behaviors following central nervous system trauma.
脊髓损伤 (SCI) 每年影响全球约 50 万人,其中大多数人患有慢性神经性疼痛。SCI 后,这些人中约有 60%被诊断出患有共病情绪障碍,而一般人群中只有约 21%在其一生中会经历情绪障碍。我们假设疼痛和抑郁样失调发生在 SCI 后,并与节段性疼痛中心异常的巨噬细胞浸润有关。我们对 LysM-eGFP 报告小鼠完成了中度单侧 C5 脊髓挫伤,以可视化浸润的巨噬细胞。在 SCI 后 6 周时,与对照和假手术组相比,小鼠表现出疼痛和抑郁样功能障碍。雌雄之间没有差异,表明性别不是导致 SCI 后疼痛或抑郁样行为的一个因素。利用层次聚类分析,我们根据终点疼痛和抑郁样行为评分对小鼠进行分类。大约 59.3%的 SCI 小鼠根据机械刺激的足底撤回阈值和强迫游泳试验中的不动时间增加而聚类。与对照和假手术组相比,SCI 小鼠在损伤中心、同侧 C7-8 背角和 C7-8 背根神经节中显示出更多的髓样细胞存在,这一点通过 eGFP、CD68 和 Iba1 免疫染色得到证实。这进一步通过 SCI 诱导的背角和背根神经节中髓样细胞激活状态及其相关分泌组的基因表达改变得到证实。总之,中度单侧颈 SCI 在一小部分小鼠中引起了与疼痛相关的和抑郁样行为的发展,这些行为变化与节段性疼痛通路中的免疫系统激活一致。观点:这些实验描述了与疼痛相关的和抑郁样行为,并将这些变化与 SCI 后的免疫反应相关联。虽然使啮齿动物人性化是不可能的,但本研究的结果为临床文献提供了信息,以仔细检查在人类中报告的性别差异,以更好地理解中枢神经系统创伤后疼痛和抑郁样行为的潜在共同病因。
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