Center for Neuroscience, University of California Davis, Davis, CA, 95618, USA.
Department of Cell Biology and Human Anatomy, University of California Davis, Davis, CA, 95616, USA.
Sci Rep. 2019 Mar 19;9(1):4858. doi: 10.1038/s41598-019-41141-0.
Neuroinflammation commonly accompanies neurodegeneration, but the specific roles of resident and infiltrating immune cells during degeneration remains controversial. Much of the difficulty in assessing myeloid cell-specific functions during disease progression arises from the inability to clearly distinguish between activated microglia and bone marrow-derived monocytes and macrophages in various stages of differentiation and activation within the central nervous system. Using an inducible model of photoreceptor cell death, we investigated the prevalence of infiltrating monocytes and macrophage subpopulations after the initiation of degeneration in the mouse retina. In vivo retinal imaging revealed infiltration of CCR2 leukocytes across retinal vessels and into the parenchyma within 48 hours of photoreceptor degeneration. Immunohistochemistry and flow cytometry confirmed and characterized these leukocytes as CD11bCD45 cells. Single-cell mRNA sequencing of the entire CD11bCD45 population revealed the presence of resting microglia, activated microglia, monocytes, and macrophages as well as 12 distinct subpopulations within these four major cell classes. Our results demonstrate a previously immeasurable degree of molecular heterogeneity in the innate immune response to cell-autonomous degeneration within the central nervous system and highlight the necessity of unbiased high-throughput and high-dimensional molecular techniques like scRNAseq to understand the complex and changing landscape of immune responders during disease progression.
神经炎症通常伴随着神经退行性变，但驻留和浸润免疫细胞在变性过程中的具体作用仍存在争议。在评估疾病进展过程中髓样细胞特定功能时，面临的主要困难是无法在中枢神经系统内的分化和激活的各个阶段，明确区分活化的小胶质细胞与骨髓来源的单核细胞和巨噬细胞。我们利用光感受器细胞死亡的诱导模型，研究了在小鼠视网膜变性开始后浸润单核细胞和巨噬细胞亚群的流行情况。体内视网膜成像显示，在光感受器变性后 48 小时内，CCR2 白细胞通过视网膜血管渗透并进入实质。免疫组织化学和流式细胞术证实并将这些白细胞鉴定为 CD11bCD45 细胞。对整个 CD11bCD45 群体的单细胞 mRNA 测序揭示了在中枢神经系统内的自主变性的固有免疫反应中存在静止小胶质细胞、活化小胶质细胞、单核细胞和巨噬细胞以及这四个主要细胞类别的 12 个不同亚群。我们的研究结果表明，在中枢神经系统内的自主变性的固有免疫反应中存在以前无法衡量的分子异质性程度，并强调需要使用无偏倚的高通量和高维分子技术（如 scRNAseq）来理解疾病进展过程中免疫反应者的复杂和不断变化的景观。
