Multiple sclerosis is an immune-mediated chronic inflammatory disease of the CNS that leads to demyelinated lesions in the grey and white matter. Inflammatory, active demyelinating white matter lesions predominate in the relapsing-remitting disease stages, whereas in the progressive stage the so-called slowly expanding lesion is characteristic. These lesions show an accumulation of macrophages/microglia at their borders, mediating the ongoing myelin breakdown and axonal degeneration. The exact pathogenetic mechanisms of lesion progression in chronic multiple sclerosis are still not clear. In the present study, we performed a detailed immunological and molecular profiling of slowly expanding lesions (n = 21) from 13 patients aged between 30 to 74 years (five females and eight males), focusing on macrophage/microglia differentiation. By applying the microglia-specific marker TMEM119, we demonstrate that cells accumulating at the lesion edge almost exclusively belonged to the microglia lineage. Macrophages/microglia can be subdivided into the M1 type, which are associated with inflammatory and degenerative processes, and M2 type, with protective properties, whereby also intermediate polarization phenotypes can be observed. By using a panel of markers characterizing M1- or M2-type macrophages/microglia, we observed a preferential accumulation of M1-type differentiated cells at the lesion edge, indicating a crucial role of these cells in lesion progression. Additionally, unbiased RNA microarray analyses of macrodissected lesion edges from slowly expanding and chronic inactive lesions as well as normal-appearing white matter were performed. In slowly expanding lesions, we identified a total of 165 genes that were upregulated and 35 genes that were downregulated. The upregulated genes included macrophage/microglia-associated genes involved in immune defence and inflammatory processes. Among the upregulated genes were ALOX15B, MME and TNFRSF25. We confirmed increased expression of ALOX15B by quantitative PCR, and of all three genes on the protein level by immunohistochemistry. In conclusion, the present study characterized in detail slowly expanding lesions in progressive multiple sclerosis and demonstrated a preferential accumulation of resident microglia with M1 differentiation at the lesion edge. Microarray analysis showed an increased expression of genes related to immune function, metabolic processes as well as transcription/translation. Thus, these genes may serve as future therapeutic targets to impede lesion progression.

中文翻译：

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进行性多发性硬化中缓慢扩展病变的分子标记。

多发性硬化症是中枢神经系统的一种免疫介导的慢性炎症性疾病，可导致灰质和白质脱髓鞘性病变。炎性的，活跃的脱髓鞘性白质病变在复发型疾病阶段占主导地位，而在进行性阶段，所谓的缓慢扩展病变是特征。这些病变在其边界处显示出巨噬细胞/小胶质细胞的积累，介导了持续的髓磷脂分解和轴突变性。慢性多发性硬化症中病变进展的确切发病机制尚不清楚。在本研究中，我们对缓慢扩展的病变进行了详细的免疫学和分子分析（n = 21）年龄在30至74岁之间的13位患者（五位女性和八位男性），主要研究巨噬细胞/小胶质细胞的分化。通过应用小胶质细胞特异性标记TMEM119，我们证明了在病变边缘积累的细胞几乎完全属于小胶质细胞谱系。巨噬细胞/小胶质细胞可分为与炎症和变性过程相关的M1型和具有保护特性的M2型，因此也可以观察到中间极化表型。通过使用一组表征M1或M2型巨噬细胞/小胶质细胞的标志物，我们观察到了M1型分化细胞在病灶边缘的优先积累，表明这些细胞在病灶进展中起着至关重要的作用。另外，进行了从缓慢扩展和慢性非活动性病变以及正常出现的白质的宏观解剖病变边缘的无偏RNA微阵列分析。在缓慢扩展的病变中，我们确定了总共165个上调的基因和35个下调的基因。上调的基因包括参与免疫防御和炎症过程的巨噬细胞/小胶质细胞相关基因。在上调的基因中有ALOX15B，MME和TNFRSF25。我们通过定量PCR证实了ALOX15B的表达增加，并且通过免疫组织化学证实了蛋白质水平上的所有三个基因。总而言之，本研究详细描述了进行性多发性硬化中缓慢扩展病变的特征，并证明了在病变边缘具有M1分化的常驻小胶质细胞优先积累。微阵列分析显示与免疫功能，代谢过程以及转录/翻译相关的基因表达增加。因此，这些基因可作为将来治疗靶标以阻止病变进展。