Neuroimmunology unit, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montreal, H2X 0A9, Canada.
Department of Neurosciences, Université de Montréal, Montreal, H3T 1J4, Canada.
Brain. 2024 Jan 4;147(1):147-162. doi: 10.1093/brain/awad286.
Multiple sclerosis is a chronic neuroinflammatory disorder characterized by demyelination, oligodendrocyte damage/loss and neuroaxonal injury in the context of immune cell infiltration in the CNS. No neuroprotective therapy is available to promote the survival of oligodendrocytes and protect their myelin processes in immune-mediated demyelinating diseases. Pro-inflammatory CD4 Th17 cells can interact with oligodendrocytes in multiple sclerosis and its animal model, causing injury to myelinating processes and cell death through direct contact. However, the molecular mechanisms underlying the close contact and subsequent detrimental interaction of Th17 cells with oligodendrocytes remain unclear. In this study we used single cell RNA sequencing, flow cytometry and immunofluorescence studies on CNS tissue from multiple sclerosis subjects, its animal model and controls to characterize the expression of cell adhesion molecules by mature oligodendrocytes. We found that a significant proportion of human and murine mature oligodendrocytes express melanoma cell adhesion molecule (MCAM) and activated leukocyte cell adhesion molecule (ALCAM) in multiple sclerosis, in experimental autoimmune encephalomyelitis and in controls, although their regulation differs between human and mouse. We observed that exposure to pro-inflammatory cytokines or to human activated T cells are associated with a marked downregulation of the expression of MCAM but not of ALCAM at the surface of human primary oligodendrocytes. Furthermore, we used in vitro live imaging, immunofluorescence and flow cytometry to determine the contribution of these molecules to Th17-polarized cell adhesion and cytotoxicity towards human oligodendrocytes. Silencing and blocking ALCAM but not MCAM limited prolonged interactions between human primary oligodendrocytes and Th17-polarized cells, resulting in decreased adhesion of Th17-polarized cells to oligodendrocytes and conferring significant protection of oligodendrocytic processes. In conclusion, we showed that human oligodendrocytes express MCAM and ALCAM, which are differently modulated by inflammation and T cell contact. We found that ALCAM is a ligand for Th17-polarized cells, contributing to their capacity to adhere and induce damage to human oligodendrocytes, and therefore could represent a relevant target for neuroprotection in multiple sclerosis.
多发性硬化症是一种慢性神经炎症性疾病，其特征是在中枢神经系统免疫细胞浸润的情况下发生脱髓鞘、少突胶质细胞损伤/丢失和神经轴突损伤。目前尚无神经保护疗法可促进少突胶质细胞的存活并保护其髓鞘过程免受免疫介导的脱髓鞘疾病的影响。促炎 CD4 Th17 细胞可在多发性硬化症及其动物模型中与少突胶质细胞相互作用，通过直接接触导致髓鞘过程损伤和细胞死亡。然而，Th17 细胞与少突胶质细胞紧密接触和随后的有害相互作用的分子机制尚不清楚。在这项研究中，我们使用单细胞 RNA 测序、流式细胞术和免疫荧光研究，对多发性硬化症患者、其动物模型和对照者的中枢神经系统组织进行研究，以表征成熟少突胶质细胞表达的细胞粘附分子。我们发现，在多发性硬化症、实验性自身免疫性脑脊髓炎和对照者中，相当一部分人类和鼠类成熟少突胶质细胞表达黑色素瘤细胞粘附分子（MCAM）和活化白细胞细胞粘附分子（ALCAM），尽管它们在人类和小鼠之间的调节不同。我们观察到，暴露于促炎细胞因子或人类激活的 T 细胞与人类原代少突胶质细胞表面 MCAM 的表达明显下调有关，但 ALCAM 的表达则没有。此外，我们使用体外实时成像、免疫荧光和流式细胞术来确定这些分子对 Th17 极化细胞粘附和对人类少突胶质细胞细胞毒性的贡献。沉默和阻断 ALCAM 但不是 MCAM 限制了人类原代少突胶质细胞和 Th17 极化细胞之间的长时间相互作用，导致 Th17 极化细胞对少突胶质细胞的粘附减少，并对少突胶质细胞过程提供显著保护。总之，我们表明人类少突胶质细胞表达 MCAM 和 ALCAM，它们受炎症和 T 细胞接触的不同调节。我们发现 ALCAM 是 Th17 极化细胞的配体，有助于其粘附能力并诱导人类少突胶质细胞损伤，因此可能成为多发性硬化症神经保护的一个相关靶点。
