Carter Debra A, Dick Andrew D
University of Bristol, Bristol Eye Hospital, Bristol, UK.
Curr Eye Res. 2004 Jun;28(6):427-36. doi: 10.1080/02713680490503778.
Retinal microglia (MG) migrate in response to injury, degeneration and inflammation dependent upon both soluble and cognate signals they receive. Previously we found that lipopolysaccharide/interferon-gamma (LPS/IFNgamma) stimulation induces a paradoxical IL-10 mediated suppression of MG migration from retinal explants. Given the high expression of neuronal CD200, which can induce down regulation of CD200 receptor-positive MG activation and neuronal fractalkine expression potentially stimulating MG migration, we wished to further examine their respective roles in the maintenance of MG activation and migration.
A human retinal explant model of MG migration was used. CD200 receptor and fractalkine receptor stimulation was achieved by addition to explants of CD200:Fc fusion protein and recombinant cytokine respectively, with or without LPS-IFNgamma stimulation that is known to suppress migration. Cell migration and cell activation (iNOS expression) was counted and assessed by numbers of CD45+ cells by immunofluorescence and standardised flow cytometric bead array analysis was performed for cytokine production.
Retinal explants expressed fractalkine and CX3CR1 immunohistochemically and by PCR. Addition of Fractalkine and not CD200:Fc induced MG migration from retinal explants. However LPS/IFNgamma-induced suppression of MG migration could only be restored in the presence of CD200:Fc, whilst MG remained iNOS-negative and generated IL-10.
Microglial responses are tightly governed within retina. Although MG do not classically activate following LPS/IFNgamma stimulation, their migration is sustained via CD200R stimulation maintaining their potential to migrate in response to injury.
视网膜小胶质细胞（MG）会根据接收到的可溶性信号和同源信号，对损伤、退化及炎症做出迁移反应。此前我们发现，脂多糖/干扰素-γ（LPS/IFNγ）刺激会诱导一种矛盾的现象，即IL-10介导的对视网膜外植体中MG迁移的抑制。鉴于神经元CD200的高表达，其可诱导CD200受体阳性的MG激活下调以及可能刺激MG迁移的神经元趋化因子表达下调，我们希望进一步研究它们在维持MG激活和迁移中的各自作用。
使用MG迁移的人视网膜外植体模型。分别向视网膜外植体中添加CD200:Fc融合蛋白和重组细胞因子来实现对CD200受体和趋化因子受体的刺激，同时或不进行已知会抑制迁移的LPS-IFNγ刺激。通过免疫荧光法对CD45+细胞数量进行计数并评估细胞迁移和细胞激活（诱导型一氧化氮合酶表达）；通过标准化流式细胞术微珠阵列分析检测细胞因子的产生。
视网膜外植体通过免疫组织化学和PCR检测到趋化因子和CX3CR1的表达。添加趋化因子而非CD200:Fc可诱导MG从视网膜外植体迁移。然而，只有在存在CD200:Fc的情况下，LPS/IFNγ诱导的MG迁移抑制才能恢复，同时MG仍为诱导型一氧化氮合酶阴性并产生IL-10。
视网膜内小胶质细胞的反应受到严格调控。尽管MG在LPS/IFNγ刺激后不会发生典型激活，但其迁移通过CD200R刺激得以维持，从而保持其对损伤做出迁移反应的潜力。
