Single-cell sequencing reveals the optimal time window and mechanism of anti-inflammatory treatment in spinal cord injury

Though the occurrence of neuroinflammation after spinal cord injury (SCI) is essential for antigen clearance and tissue repair, excessive inflammation results in cell death and axon dieback. The effect of anti-inflammatory medicine utilized in clinical treatment remains debatable owing to the inappropriate therapeutic schedule that does not align with the biological process of immune reaction. A better understanding of the immunity process is critical to promote effective anti-inflammatory therapeutics. However, cellular heterogeneity, which results in complex cellular functions, is a major challenge. In this study, we performed single-cell RNA sequencing by profiling the tissue proximity to the injury site at different time points after SCI. Depending on the analysis of single-cell data and histochemistry observation, we proposed an appropriate time window for anti-inflammatory medicine treatment. We also verified the mechanism of typical anti-inflammatory medicine MPSS, which was found attributable to the activation inhibition of cells with pro-inflammatory phenotype through the down-regulation of pathways such as TNF, IL2, and MIF. These pathways could also be provided as targets for anti-inflammatory treatment. Collectively, we provide a therapeutic schedule of 1–3 dpi (days post-injury) to argue against classical early pulse therapy and provide some pathways for target therapy in the future.尽管脊髓损伤（SCI）后发生神经炎症（neuroinflammation）对于抗原清除（antigen clearance）与组织修复（tissue repair）至关重要，但过度炎症反应会引发细胞死亡（cell death）与轴突溃变（axon dieback）。当前临床应用的抗炎药物（anti-inflammatory medicine）治疗方案仍存在争议，究其原因在于现有治疗方案未匹配免疫反应（immune reaction）的生物学进程。深入阐明免疫过程（immunity process），对于开发有效的抗炎治疗策略（anti-inflammatory therapeutics）至关重要。然而，细胞异质性（cellular heterogeneity）导致细胞功能复杂多样，这是该领域研究的核心挑战之一。本研究针对脊髓损伤后不同时间点的损伤灶邻近组织开展单细胞RNA测序（single-cell RNA sequencing）分析。结合单细胞数据分析与组织化学观察（histochemistry observation）结果，我们提出了适配抗炎药物治疗的合理时间窗。此外，我们验证了典型抗炎药物MPSS的作用机制，发现其可通过下调肿瘤坏死因子（TNF）、白细胞介素2（IL2）及巨噬细胞迁移抑制因子（MIF）等通路，抑制促炎表型（pro-inflammatory phenotype）细胞的激活。上述通路亦可作为抗炎治疗的潜在靶点。综上，本研究提出损伤后1~3天（dpi，days post-injury）的治疗方案，以挑战经典早期冲击疗法，并为未来的靶向治疗（target therapy）提供了若干潜在通路靶点。