Neural Stem Cell Institute, Rensselaer, NY, 12214, USA.
J Neuroinflammation. 2022 Nov 4;19(1):266. doi: 10.1186/s12974-022-02627-3.
Immune cells play crucial roles after spinal cord injury (SCI). However, incomplete knowledge of immune contributions to injury and repair hinders development of SCI therapies. We leveraged single-cell observations to describe key populations of immune cells present in the spinal cord and changes in their transcriptional profiles from uninjured to subacute and chronic stages of SCI.
Deep-read single-cell sequencing was performed on CD45 cells from spinal cords of uninjured and injured Swiss-webster mice. After T9 thoracic contusion, cells were collected 3-, 7-, and 60-day post-injury (dpi). Subpopulations of CD45 immune cells were identified informatically, and their transcriptional responses characterized with time. We compared gene expression in spinal cord microglia and B cell subpopulations with those in published models of disease and injury. Microglia were compared with Disease Associated Microglia (DAM) and Injury Responsive Microglia (IRM). B cells were compared to developmental lineage states and to an Amyotrophic Lateral Sclerosis (ALS) model.
In uninjured and 7 dpi spinal cord, most CD45 cells isolated were microglia while chronically B cells predominated. B cells accumulating in the spinal cord following injury included immature B to mature stages and were predominantly found in the injury zone. We defined diverse subtypes of microglia and B cells with altered gene expression with time after SCI. Spinal cord microglia gene expression indicates differences from brain microglia at rest and in inflammatory states. Expression analysis of signaling ligand-receptor partners identified microglia-B cell interactions at acute and chronic stages that may be involved in B cell recruitment, retention, and formation of ectopic lymphoid follicles.
Immune cell responses to SCI have region-specific aspects and evolve with time. Developmentally diverse populations of B cells accumulate in the spinal cord following injury. Microglia at subacute stages express B cell recruitment factors, while chronically, they express factors predicted to reduce B cell inflammatory state. In the injured spinal cord, B cells create ectopic lymphoid structures, and express secreted factors potentially acting on microglia. Our study predicts previously unidentified crosstalk between microglia and B cells post-injury at acute and chronic stages, revealing new potential targets of inflammatory responses for SCI repair warranting future functional analyses.
免疫细胞在脊髓损伤（SCI）后发挥着至关重要的作用。然而，对免疫反应在损伤和修复中的作用认识不充分，阻碍了 SCI 治疗方法的发展。我们利用单细胞观察来描述脊髓中存在的关键免疫细胞群体，并描述它们从未受伤到亚急性和慢性 SCI 阶段转录谱的变化。
对未受伤和受伤的瑞士 Webster 小鼠 T9 胸段挫伤后 3、7 和 60 天的脊髓 CD45 细胞进行深度读取单细胞测序。使用信息学方法鉴定 CD45 免疫细胞的亚群，并随时间描述其转录反应。我们将脊髓小胶质细胞和 B 细胞亚群的基因表达与已发表的疾病和损伤模型进行比较。将小胶质细胞与疾病相关小胶质细胞（DAM）和损伤反应性小胶质细胞（IRM）进行比较。将 B 细胞与发育谱系状态和肌萎缩侧索硬化症（ALS）模型进行比较。
在未受伤和 7 天的脊髓中，分离出的大多数 CD45 细胞是小胶质细胞，而慢性时则以 B 细胞为主。受伤后在脊髓中积累的 B 细胞包括从幼稚 B 细胞到成熟阶段，主要存在于损伤区。我们定义了随着 SCI 后时间的推移，具有不同基因表达的多样化小胶质细胞和 B 细胞亚型。脊髓小胶质细胞的基因表达表明其在静息和炎症状态下与大脑小胶质细胞存在差异。信号配体-受体伙伴关系的表达分析确定了急性和慢性阶段小胶质细胞-B 细胞相互作用，这些相互作用可能参与 B 细胞的募集、保留和异位淋巴滤泡的形成。
SCI 后的免疫细胞反应具有区域特异性，并随时间演变。受伤后，发育多样化的 B 细胞群体在脊髓中积累。亚急性阶段的小胶质细胞表达 B 细胞募集因子，而慢性时则表达预计会降低 B 细胞炎症状态的因子。在受伤的脊髓中，B 细胞形成异位淋巴结构，并表达潜在作用于小胶质细胞的分泌因子。我们的研究预测了损伤后急性和慢性阶段小胶质细胞和 B 细胞之间以前未被识别的交叉对话，揭示了 SCI 修复中炎症反应的新潜在靶点，值得进一步进行功能分析。
