Spinal cord injury (SCI) results in acute damage and triggers secondary injury responses with sustained neuronal loss and dysfunction. However, the underlying mechanisms for these delayed neuronal pathologies are not entirely understood. SCI results in the swelling of spinal neurons, but the contribution of cell swelling to neuronal loss and functional deficits after SCI has not been systematically characterized. In this study, we devised a three-dimensional image analysis pipeline to evaluate spinal neurons, examining their types, quantities, volumes, and spatial distribution in a double-lateral hemisection SCI mouse model. We found that both excitatory and inhibitory neurons swell and are lost, albeit with distinct temporal patterns. Inhibitory neurons demonstrated marked swelling and decline in number on day 2 after SCI, which resolved by day 14. In contrast, excitatory neurons maintained persistent swelling and continued cell loss for at least 35 days after SCI in mice. Excitatory neurons exhibited sustained expression of the Na + -K + -Cl − cotransporter 1 (NKCC1), whereas inhibitory neurons down-regulated the protein by day 14 after SCI. Treatment with a Food and Drug Administration–approved NKCC1 inhibitor, bumetanide, mitigated swelling of excitatory neurons and reduced their loss in the secondary injury phase after SCI. The administration of bumetanide after SCI in mouse improved locomotor recovery, with functional benefits persisting for at least 4 weeks after treatment cessation. This study advances our understanding of SCI-related pathology and introduces bumetanide as a potential treatment to mitigate sustained neuronal swelling and enhance recovery after SCI.

中文翻译：

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减少脊髓损伤后长时间兴奋性神经元肿胀可改善小鼠的运动恢复


脊髓损伤 （SCI） 导致急性损伤，并引发继发性损伤反应，伴有持续的神经元丢失和功能障碍。然而，这些延迟性神经元病变的潜在机制尚不完全清楚。SCI 导致脊髓神经元肿胀，但尚未系统地表征细胞肿胀对 SCI 后神经元丢失和功能缺陷的贡献。在这项研究中，我们设计了一个三维图像分析管道来评估脊髓神经元，检查它们在双侧半切 SCI 小鼠模型中的类型、数量、体积和空间分布。我们发现兴奋性和抑制性神经元都会肿胀和丢失，尽管具有不同的时间模式。抑制性神经元在 SCI 后第 2 天表现出明显的肿胀和数量下降，并在第 14 天消退。相比之下，小鼠 SCI 后兴奋性神经元维持持续肿胀和持续细胞丢失至少 35 天。兴奋性神经元表现出 Na + -K + -Cl − 协同转运蛋白 1 （NKCC1） 的持续表达，而抑制性神经元在 SCI 后第 14 天下调该蛋白。用美国食品和药物管理局批准的 NKCC1 抑制剂布美他尼治疗可减轻兴奋性神经元的肿胀并减少它们在 SCI 后继发性损伤期的损失。小鼠 SCI 后布美他尼的给药改善了运动恢复，功能益处在治疗停止后持续至少 4 周。这项研究促进了我们对 SCI 相关病理学的理解，并介绍了布美他尼作为减轻持续神经元肿胀和促进 SCI 后恢复的潜在治疗方法。