Single Cell Atlas of Injured Sciatic Nerve Tissue

Sciatic nerve crush (SNC) triggers sterile inflammation within the distal nerve and de-afferented dorsal root ganglia (DRGs). In the nerve, neutrophils and pro-inflammatory Ly6Chigh monocytes appear first and rapidly give way to Ly6Clow resolving macrophages. Transcriptional profiling of injured nerve tissue identifies six macrophage subpopulations, repair Schwann cells and mesenchymal cells as the main cell types. Macrophages at the nerve crush site are distinct from macrophages associated with degenerating nerve fibers. Monocytes and macrophages in the injured nerve “eat” apoptotic cell corpses of leukocytes and thereby contribute to an anti-inflammatory milieu. Studies with chimeric mice show that following SNC few blood-derived immune cells enter DRGs. Myeloid cells in the injured nerve, but not DRGs, express the receptor for the chemokine GM-CSF. In the absence of GM-CSF, conditioning-lesion induced regeneration of DRG neuron central projections is abrogated. Thus, a carefully orchestrated immune response in the nerve is required for conditioning-lesion induced neurorepair. Overall design: scRNAseq analysis, 3 days post sciatic nerve crush, for 3 WT mice

坐骨神经压榨损伤（Sciatic nerve crush, SNC）可引发损伤远端神经以及去传入背根神经节（dorsal root ganglia, DRGs）内的无菌性炎症。在损伤神经中，中性粒细胞与促炎型Ly6C高表达单核细胞率先出现，并快速被Ly6C低表达的消退型巨噬细胞所取代。对损伤神经组织开展转录组谱分析后，鉴定得到6种巨噬细胞亚群，修复型雪旺细胞与间充质细胞为主要细胞类群。坐骨神经压榨损伤部位的巨噬细胞与退变神经纤维关联的巨噬细胞存在显著差异。损伤神经内的单核细胞与巨噬细胞可吞噬白细胞的凋亡细胞小体，进而参与构建抗炎微环境。嵌合小鼠实验结果显示，坐骨神经压榨损伤后，仅有少量血液来源的免疫细胞会侵入背根神经节。损伤神经而非背根神经节内的髓系细胞，可表达趋化因子GM-CSF（粒细胞-巨噬细胞集落刺激因子）的受体。在缺乏GM-CSF的情况下，条件性损伤诱导的背根神经节神经元中枢投射再生会被完全阻断。因此，条件性损伤诱导的神经修复有赖于神经内经过精密调控的免疫应答。实验整体设计：针对3只野生型（wild-type, WT）小鼠，在坐骨神经压榨损伤后3天开展单细胞RNA测序（single-cell RNA sequencing, scRNAseq）分析。